Perovskite quantum dot composite film and preparation method thereof

Abstract

This invention discloses a perovskite quantum dot composite film and its preparation method. The raw materials for preparing the composite film include a perovskite quantum dot dispersion, lauryl methacrylate, zinc undecanoate, methacryloyloxyethyl phosphate, polyurethane acrylate oligomer, mercapto monomer, and a photoinitiator. The preparation process includes: ligand exchange between zinc undecanoate and the quantum dot dispersion; addition of lauryl methacrylate and removal of the original solvent under reduced pressure; subsequent addition of the remaining components for degassing and mixing; coating a wet film; and curing by dual-band continuous irradiation. This invention utilizes zinc undecanoate as a bridge, enabling its terminal double bonds to undergo cross-linking reactions with the matrix resin, thus covalently anchoring the quantum dots in situ within the polymer network. This reduces the spatial migration and aggregation of quantum dots, helping to delay the degradation of the optical properties of the composite film.

Description

Technical Field

[0001] This invention relates to the field of optical display materials technology, specifically to a perovskite quantum dot composite thin film and its preparation method. Background Technology

[0002] Perovskite quantum dots possess promising applications in liquid crystal display backlighting and other optoelectronic fields due to their tunable emission wavelength, high color purity, and high fluorescence quantum yield. However, limited by their ionic crystal structure, perovskite quantum dots are sensitive to moisture, oxygen, and heat in the external environment, making them prone to structural degradation and fluorescence quenching in practical applications.

[0003] The common processing method involves physically blending perovskite quantum dot dispersions with polymer resin monomers, followed by coating and curing, attempting to utilize the physical barrier effect of the polymer matrix to isolate it from water and oxygen erosion from the external environment. However, in practical long-term applications, this simple physical encapsulation method has certain limitations. Because the surface of perovskite quantum dots typically relies on free ligands such as oleic acid and oleylamine to maintain dispersion, these non-polar ligands have limited compatibility with most polymer matrices containing polar groups. During photocuring crosslinking or thermal film formation, quantum dots are highly susceptible to phase separation in liquid or semi-solid resin systems, leading to spatial aggregation.

[0004] When the luminescent cores aggregate, their original optical advantages are significantly weakened. Furthermore, the matrix network formed by physical blending cannot effectively restrict the thermal migration of quantum dots at the microscopic scale. When the composite film is subjected to high-temperature backlight operation or humid aging environments, the free quantum dots are prone to displacement and aggregation due to the thermal movement of the matrix segments. Simultaneously, conventional resin curing often involves volume shrinkage, and the resulting microcracks or internal pores become channels for external water and oxygen permeation, further accelerating the degradation of the internal quantum dots. This leads to significant brightness decay and color shift in the film during long-term use, making it difficult to meet the high reliability requirements of optical film materials for commercial display devices. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a perovskite quantum dot composite film and its preparation method, which solves the problem that existing perovskite quantum dots are prone to agglomeration in polymer matrices and have poor resistance to water, oxygen and heat, resulting in rapid degradation of optical performance of composite films during long-term use, making it difficult to meet the requirements of high-reliability optical display applications.

[0006] To achieve the above objectives, the present invention provides the following technical solution: In a first aspect, the present invention provides a perovskite quantum dot composite thin film, which adopts the following technical solution: A perovskite quantum dot composite thin film comprises the following components in parts by weight: 15-25 parts of perovskite quantum dot dispersion; 15-25 parts of lauryl methacrylate; 2-6 parts of zinc undecenoate; 0.5–2.0 parts of methacryloyloxyethyl phosphate; 50-65 parts of polyurethane acrylate oligomer; 3-8 parts of thiol monomer; Photoinitiator 1.5–3.0 parts; The photoinitiator is a mixture of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide and 2,2-dimethoxy-2-phenylacetophenone; The perovskite quantum dot composite film undergoes dual-band continuous irradiation curing during the curing stage. It first undergoes preliminary curing in the first temperature zone with a main wavelength of 405 nm; then it undergoes deep cross-linking in the second temperature zone with a main wavelength of 365 nm.

[0007] In this process, zinc undecanoate is bonded to the surface of perovskite quantum dots, and the terminal double bonds of zinc undecanoate undergo cross-linking reactions with thiol monomers and polyurethane acrylate oligomers to form a structure that covalently anchors the perovskite quantum dots in situ within the polymer network.

[0008] By using a specific ratio of polymer matrix monomers to zinc undecenoate, the dispersion and binding state of perovskite quantum dots in the organic network are improved, thereby contributing to the stability of the composite film. From a mechanistic perspective, zinc undecenoate participates in ligand exchange on the surface through its zinc carboxylate end groups, binding to the inorganic core surface of the quantum dots.

[0009] This substitution process helps passivate local halogen vacancies and reduce non-radiative recombination. In the subsequent photoinitiated curing stage, the thiol monomers in the system crosslink with the carbon-carbon double bonds at the end of zinc undecenoate furthest from the core, accompanied by the copolymerization reaction of components such as lauryl methacrylate.

[0010] Multiple reaction mechanisms enable quantum dots to integrate into polymer networks via zinc undecenoate as an intermediate structure, forming in-situ chemical cross-links. Compared to simple physical blending, this structural-level bonding reduces the tendency of quantum dots to undergo thermal migration or aggregation due to environmental factors.

[0011] In addition, the methacryloyloxyethyl phosphate introduced in the formulation can neutralize some of the residual free amine ligands in the system through its acidic characteristics, which helps to improve the appearance of the resin liquid during storage; the phosphate groups it contains also provide a certain degree of adhesion support for the coating and substrate interface.

[0012] Preferably, the photoinitiator is a mixture of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide and 1-hydroxycyclohexylphenyl ketone, wherein the amount of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide is 0.6–0.86 parts and the amount of 1-hydroxycyclohexylphenyl ketone is 0.9–2.14 parts. By adopting the above technical solution and combining photoinitiators with different absorption bands, namely 2,4,6-trimethylbenzoyl-diphenylphosphine oxide which absorbs long wavelengths and 1-hydroxycyclohexylphenyl ketone which absorbs short wavelengths, a relatively differentiated curing process can be promoted in the coating thickness direction. The surface, due to the influence of short wavelengths, forms a cross-linked network more quickly, which helps to isolate some oxygen inhibition; while the bottom layer continues to react under long-wave initiation. This internal and external cross-linking method can alleviate the volume shrinkage stress caused by overall cross-linking to a certain extent.

[0013] Preferably, the polyurethane acrylate oligomer is synthesized by reacting polycaprolactone diol, isophorone diisocyanate, and hydroxyethyl acrylate, with a number-average molecular weight of 1680–2900 g / mol. By employing the above technical solution, the isophorone diisocyanate, with its alicyclic structure, combined with the flexible properties of polycaprolactone diol, provides the synthesized oligomer with basic mechanical properties and a certain degree of water and oxygen barrier effect to the cured resin matrix. Controlling the molecular weight of the oligomer within the above range mainly considers its viscosity and miscibility in the liquid state, ensuring good miscibility with the quantum dot dispersion; and maintaining the coating's basic resistance to deformation after film formation, reducing the risk of microcrack formation, which is of practical significance for delaying the penetration of external moisture.

[0014] Preferably, the solid content of the perovskite quantum dot dispersion is 10wt% to 15wt%; the perovskite quantum dots are all inorganic perovskite quantum dots, whose inorganic core is generated by the reaction of lead bromide and cesium bromide in an equimolar ratio, and whose surface is coated with oleic acid and oleylamine ligands, and the dispersion solvent is toluene.

[0015] By adopting the above technical solution, using inorganic lead cesium bromide as the luminescent core, and controlling its dispersion liquid-solid content within a specific range, the aim is to retain the basic luminescent properties while also ensuring compatibility within the system. Oleic acid and oleylamine, as the initial ligands, play a role in dispersion and stabilization in the liquid phase in the early stages, and also participate in the overall process as leaving groups in subsequent displacement reactions.

[0016] Secondly, the present invention provides a method for preparing perovskite quantum dot composite thin films, employing the following technical solution: A method for preparing perovskite quantum dot composite thin films includes the following steps: S1. After dissolving lauryl methacrylate and zinc undecenoate, add the perovskite quantum dot dispersion and stir to mix. S2. Under reduced pressure, vacuum distillation is carried out to remove the original solvent from the dispersion to obtain the quantum dot monomer dispersion system. S3. Methacryloxyethyl phosphate, polyurethane acrylate oligomer, mercapto monomer and photoinitiator are added sequentially to the quantum dot monomer dispersion system, and the mixture is degassed and mixed under yellow light to obtain a photocurable coating. S4. Apply the photocurable coating onto the substrate to form a wet film; S5. The substrate coated with the wet film is placed in an ultraviolet curing device and cured by dual-band continuous irradiation to obtain the composite film**; the dual-band continuous irradiation curing includes: firstly, preliminary curing in a first temperature zone, with a main wavelength of 405nm and an irradiation intensity of 50-100mW / cm². 2 The irradiation time is 10–20 seconds; followed by deep cross-linking in a second temperature zone, with a main wavelength of 365 nm and an irradiation intensity of 800–1200 mW / cm². 2 The irradiation time is 5 to 10 seconds.

[0017] By employing the above technical solution, the mixing and stirring at room temperature throughout the preparation process helps reduce the impact of thermal factors on the quantum dot lattice structure, allowing zinc undecenoate to undergo ligand replacement more smoothly. Subsequently, lauryl methacrylate, a monomer with a relatively high boiling point, is introduced, along with a vacuum distillation process. This aims to utilize the difference in volatility to remove the low-boiling-point original solvent, reducing porosity or bubbles caused by solvent evaporation in the later film-forming stages. Subsequent operations are performed in a yellow light environment, primarily to avoid abnormal gelation caused by stray light. Finally, ultraviolet irradiation promotes polymerization, gradually transforming the liquid coating into a composite film containing a cross-linked network, further restricting the spatial free-floating tendency of the quantum dots.

[0018] Preferably, in step S2, the temperature of vacuum distillation is 45-55°C, the gauge pressure is 0.005-0.02 MPa, and the continuous vacuum distillation time is 1-2 hours.

[0019] By employing the above technical solution, the distillation temperature and pressure are limited to the aforementioned conditions, balancing solvent removal efficiency with the heat resistance limitations of the component materials. A moderate vacuum and medium-temperature environment facilitates the separation of the original solvent, reducing the solvent residue rate in the liquid system, while minimizing the negative interference of sustained high temperatures on the intrinsic optical properties of quantum dots.

[0020] Preferably, in step S5, the dual-band continuous irradiation curing includes: firstly, preliminary curing in a first temperature zone, with a light source wavelength of 405 nm and an irradiation intensity of 50–100 mW / cm². 2The irradiation time is 10–20 seconds; followed by deep cross-linking in a second temperature zone, with a light source wavelength of 365 nm and an irradiation intensity of 800–1200 mW / cm². 2 The irradiation time is 5 to 10 seconds.

[0021] By employing the above technical solution, the dual-band irradiation treatment is primarily based on the difference in penetration depth of light within the coating at different wavelengths. The first stage uses a 405nm light source with a relatively low irradiation intensity, biased towards exciting the initiator in the deeper regions, allowing the crosslinking reaction to proceed at a relatively gentle rate, leaving room for polymer chain rearrangement and partial stress release. The subsequent stronger 365nm irradiation focuses on surface curing to accelerate film formation. This staged light treatment mode helps reduce internal stress concentration caused by excessively rapid curing.

[0022] Preferably, in step S4, the substrate is an optical-grade polyethylene terephthalate substrate that has undergone single-sided corona treatment, and the thickness of the wet film is controlled between 50 and 100 μm.

[0023] By employing the above technical solution and subjecting the substrate to corona treatment, some polar groups can be introduced, thereby improving the wetting conditions of the polyester surface and facilitating the spreading and interfacial bonding of the liquid photocurable coating. Controlling the wet film thickness within the aforementioned range serves two purposes: firstly, it satisfies the requirement for light to penetrate the underlying layer for curing; secondly, it balances the physical space occupied by the finished film in the actual optical structure and its luminescence.

[0024] Preferably, a transitional cooling step is included between step S2 and step S3: after the vacuum distillation is completed, the system temperature is reduced to 25-30°C at a cooling rate not exceeding 2°C / min and then restored to atmospheric pressure.

[0025] By adopting the above technical solution, a relatively gradual cooling transition after vacuum distillation can reduce the possibility of local phase separation caused by drastic temperature changes. Restoring atmospheric pressure within a range slightly above room temperature maintains the operating viscosity of the resin during subsequent mixing and also reduces the backflow and dissolution of external air into the system, alleviating the pressure on subsequent degassing processes.

[0026] Preferably, in step S3, the degassing and mixing conditions are: temperature 25-30℃, gauge pressure -0.09MPa or below, rotation speed 150-250rpm, and degassing and mixing time 30-50 minutes.

[0027] By adopting the above technical solution, setting a specific vacuum level and supplementing it with mechanical agitation at an appropriate speed, the free air entrained during the initial mixing can be expelled. After removing air bubbles and some dissolved gases, the number of light scattering centers generated by micropores after coating curing can be effectively reduced, which has a positive effect on maintaining light transmittance and controlling film haze.

[0028] This invention provides a perovskite quantum dot composite thin film and its preparation method. It has the following beneficial effects: 1. In this invention, zinc undecanoate is used as a ligand in the composite film to participate in the displacement reaction on the surface of quantum dots. This, combined with the thiol monomers and polyurethane acrylate oligomers within the system, leads to crosslinking during the photocuring stage. This synergy between components allows the quantum dots to integrate into the polymer matrix network through chemical bonds, overcoming the tendency for localized phase separation in conventional physical blending. This microstructure restricts the spatial migration and aggregation of luminescent cores under high temperature or high humidity conditions, thus delaying the degradation of the film's optical properties during long-term applications.

[0029] 2. This invention addresses the film-forming process by selecting a combination of photoinitiators that absorb different ultraviolet wavelengths and employing a dual-band continuous irradiation operation to promote differentiated cross-linking along the coating thickness direction. The longer wavelength light source penetrates deeper and has a relatively gentler initiation rate, allowing the underlying monomers to slowly polymerize to release some structural stress; the subsequent shorter wavelength light source focuses on the surface to accelerate film formation. This mitigates the problem of concentrated volume shrinkage caused by instantaneous curing under strong light, reduces residual stress within the coating, and helps maintain the flatness of the film.

[0030] 3. The methacryloyloxyethyl phosphate introduced in the formulation of this invention, with its acidic groups, can neutralize residual free amines in the dispersion, helping to maintain the viscosity stability of the uncured resin system during storage. In the upstream preparation process, high-boiling-point lauryl methacrylate, combined with vacuum distillation, replaces the original low-boiling-point solvent, reducing the content of volatile substances in the system. The combination of materials and processes reduces the micropores that may appear during final film formation, while the phosphate monomer also provides some support for interfacial adhesion at the bottom of the coating. Attached Figure Description

[0031] Figure 1 This is a scatter plot showing the relative content changes of relevant characteristic groups at different stages in the preparation process of this invention; wherein, Figure (a) corresponds to the change in the relative area ratio of the -SH characteristic peak, and Figure (b) corresponds to the terminal C=C characteristic peak (1640 cm⁻¹) of zinc undecenoate. -1 The relative area ratio change of ) in Figure (c) corresponds to the characteristic peak of acrylate C=C (810 cm⁻¹). -1 The relative area ratio change; Figure 2 This is a comparison graph showing the change of apparent viscosity of the coating liquid over time in Example 1 and Comparative Example 3 of the present invention under 25°C and light-protected conditions. Figure 3 This is a comparison of the normalized photoluminescence spectra of the quantum dot dispersion in Example 1 of the present invention and the final cured film in Example 1. Figure 4 This is a comparison graph showing the change in absolute fluorescence quantum yield retention over time between Example 1 and Comparative Examples 1 and 2 of the present invention under conditions of 85°C and 85% relative humidity. Figure 5 This is a comparison of the normalized photoluminescence spectra of the stepped-cured film in Example 1 of the present invention, the uncured coating liquid reference, and the single-step burst-cured film in Comparative Example 4. Figure 6 Figure 1 shows a comparison of the macroscopic physical and mechanical properties of the coatings in Example 1 and Comparative Example 4 under different dry film thicknesses. Figure 1(a) shows the measurement results of the residual stress inside the film of Example 1 and Comparative Example 4 as a function of coating thickness, and Figure 2(b) shows the measurement results of the interfacial adhesion force as a function of thickness under the corresponding pull-out method. Figure 7 This is a comparison graph showing the change in peeling and detachment area of ​​the coatings of Example 1 and Comparative Example 4 over time under boiling water treatment at 100°C. Figure 8 This is a low-magnification TEM dispersion map of the present invention; Figure 9 This is a high-resolution HRTEM lattice and anchoring structure diagram of the present invention; Figure 10 The images show the infrared spectra of samples prepared at each stage of the process in Example 1 of this invention. Detailed Implementation

[0032] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] This invention provides a perovskite quantum dot composite film and its preparation method. The main raw materials and reagents used in the following examples and comparative examples have the following sources and specifications. Reagents not specifically mentioned are all commercially available analytical grade or higher grade products.

[0034] Polycaprolactone diol (CAS No.: 36890-68-3), with a number average molecular weight of 1000 g / mol and a hydroxyl value of 112 mg KOH / g, is a linear homopolymer formed by the ring-opening polymerization of repeating unit ε-caprolactone, with hydroxyl groups at both ends.

[0035] Isophorone diisocyanate (CAS No.: 4098-71-9), purity ≥99%.

[0036] Hydroxyethyl acrylate (CAS No.: 818-61-1), purity ≥97%.

[0037] Lauryl methacrylate (CAS No.: 142-90-5), purity ≥96%.

[0038] Zinc undecenoate (CAS No.: 557-08-4), purity ≥98%.

[0039] Pentaerythritol tetra(3-mercaptopropionate) (CAS No.: 7575-23-7), purity ≥95%.

[0040] Methacryloxyethyl phosphate (CAS No.: 24599-21-1), purity ≥95%.

[0041] 2,4,6-Trimethylbenzoyl-diphenylphosphine oxide (CAS No.: 75980-60-8), purity ≥98%.

[0042] 2,2-Dimethoxy-2-phenylacetophenone (CAS No.: 24650-42-8), purity ≥99%.

[0043] Optical grade polyethylene terephthalate substrate, 125μm thick, with a surface treated with single-sided corona discharge.

[0044] Preparation Example 1: This preparation example provides a method for preparing a perovskite quantum dot toluene dispersion with a solid content of 12 wt%, comprising the following steps: 0.4 mmol of lead bromide and 0.4 mmol of cesium bromide were dissolved in 12 mL of N,N-dimethylformamide, followed by the addition of 1.5 mL of oleic acid and 1.0 mL of oleylamine. The mixture was magnetically stirred at room temperature for 45 minutes until completely dissolved, yielding a transparent precursor solution. Quickly inject 1.5 mL of the above precursor solution into 25 mL of vigorously stirred toluene solvent and react for 2 minutes; The resulting mixture was centrifuged at 9000 rpm for 12 minutes and the supernatant was discarded. The precipitate at the bottom was redispersed in fresh toluene, sonicated for 8 minutes, and centrifuged again at 3000 rpm to remove undispersed large particles. The supernatant was collected and the amount of toluene added was adjusted to achieve a solid content of 12 wt%.

[0045] Preparation Example 2: This preparation example provides a method for preparing a perovskite quantum dot toluene dispersion with a solid content of 10 wt%, including the following steps: 0.3 mmol of lead bromide and 0.3 mmol of cesium bromide were dissolved in 10 mL of N,N-dimethylformamide, followed by the addition of 1.0 mL of oleic acid and 0.5 mL of oleylamine. The mixture was magnetically stirred at room temperature for 30 minutes until completely dissolved, yielding a transparent precursor solution. Quickly inject 1.0 mL of the above precursor solution into 20 mL of vigorously stirred toluene solvent and react for 1 minute; Centrifuge the resulting mixture at 8000 rpm for 10 minutes and discard the supernatant. Redisperse the precipitate at the bottom in fresh toluene, sonicate for 5 minutes, and centrifuge again at 3000 rpm to remove undispersed large particles. Collect the supernatant and adjust the amount of toluene added to achieve a solid content of 10 wt%.

[0046] Preparation Example 3: This preparation example provides a method for preparing a perovskite quantum dot toluene dispersion with a solid content of 15 wt%, including the following steps: 0.5 mmol of lead bromide and 0.5 mmol of cesium bromide were dissolved in 15 mL of N,N-dimethylformamide, followed by the addition of 2.0 mL of oleic acid and 1.5 mL of oleylamine. The mixture was magnetically stirred at room temperature for 60 minutes until completely dissolved, yielding a clear precursor solution. 2.0 mL of the above precursor solution was rapidly injected into 30 mL of vigorously stirred toluene solvent, and the reaction was allowed to proceed for 3 minutes. Centrifuge the resulting mixture at 10,000 rpm for 15 minutes and discard the supernatant; The precipitate at the bottom was redispersed in fresh toluene, sonicated for 10 minutes, and then centrifuged again at 3000 rpm to remove undispersed large particles. The supernatant was collected, and the amount of toluene added was adjusted to achieve a solid content of 15 wt%.

[0047] Preparation Example 4: This preparation example provides a method for preparing polyurethane acrylate oligomers with a molecular weight of approximately 2300 g / mol, including the following steps: In a four-necked flask equipped with a mechanical stirrer, a condenser, and a thermometer, add 18.5 parts by weight of isophorone diisocyanate and 0.08 parts by weight of dibutyltin dilaurate; heat to 62°C, and slowly add 50.0 parts by weight of polycaprolactone diol dropwise through a constant pressure dropping funnel while stirring at 250 rpm, with the dropwise addition process controlled over 1.5 hours; After the addition was complete, the temperature was raised to 78°C and the reaction was carried out for 2.5 hours to obtain the isocyanate-terminated polyurethane prepolymer; the reaction system was cooled to 52°C, 0.1 parts by weight of hydroquinone monomethyl ether was added, and 8.1 parts by weight of hydroxyethyl acrylate was slowly added dropwise. After the addition was complete, the reaction continued at 72°C for 4 hours. Infrared spectroscopy monitoring was used to determine the reaction temperature at 2270 cm⁻¹. -1The reaction is stopped when the characteristic absorption peak of isocyanate at the desired molecular weight completely disappears, yielding polyurethane acrylate oligomers.

[0048] Infrared spectroscopy monitoring was conducted at 2270 cm⁻¹. -1 The reaction is stopped when the characteristic absorption peak of the isocyanate group completely disappears, yielding a polyurethane acrylate oligomer of the desired molecular weight. Hydroxyethyl acrylate is used in a slightly excess manner to ensure sufficient end-isocyanate capping, and the residual trace amount of hydroxyethyl acrylate can participate in the crosslinking reaction as a reactive component during subsequent photocuring.

[0049] Preparation Example 5: This preparation example provides a method for preparing a polyurethane acrylate oligomer with a molecular weight of approximately 1680 g / mol, including the following steps: In a four-necked flask equipped with a mechanical stirrer, a condenser, and a thermometer, add 22.2 parts by weight of isophorone diisocyanate and 0.05 parts by weight of dibutyltin dilaurate; heat to 60°C, and slowly add 50.0 parts by weight of polycaprolactone diol dropwise through a constant pressure dropping funnel while stirring at 200 rpm, with the dropwise addition process controlled over 1 hour; After the addition was complete, the temperature was raised to 75°C and the reaction was carried out for 2 hours to obtain the isocyanate-terminated polyurethane prepolymer. The reaction system was cooled to 50°C, and 0.1 parts by weight of hydroquinone monomethyl ether was added. Then, 12.2 parts by weight of hydroxyethyl acrylate were slowly added dropwise. After the addition was complete, the reaction was continued at 70°C for 3 hours. Infrared spectroscopy was used to monitor the reaction. When the temperature reached 2270 cm⁻¹... -1 The reaction is stopped when the characteristic absorption peak of isocyanate at the desired molecular weight completely disappears, yielding polyurethane acrylate oligomers.

[0050] Infrared spectroscopy monitoring was conducted at 2270 cm⁻¹. -1 The reaction is stopped when the characteristic absorption peak of the isocyanate group completely disappears, yielding a polyurethane acrylate oligomer of the desired molecular weight. Hydroxyethyl acrylate is used in a slightly excess manner to ensure sufficient end-isocyanate capping, and the residual trace amount of hydroxyethyl acrylate can participate in the crosslinking reaction as a reactive component during subsequent photocuring.

[0051] Preparation Example 6: This preparation example provides a method for preparing a polyurethane acrylate oligomer with a molecular weight of approximately 2900 g / mol, including the following steps: In a four-necked flask equipped with a mechanical stirrer, a condenser and a thermometer, add 16.7 parts by weight of isophorone diisocyanate and 0.1 parts by weight of dibutyltin dilaurate. Heat to 65°C, and slowly add 50.0 parts by weight of polycaprolactone diol through a constant pressure dropping funnel while stirring at 300 rpm. The dropping process is controlled within 2 hours. After the addition was complete, the temperature was raised to 80°C and the reaction was carried out for 3 hours to obtain the isocyanate-terminated polyurethane prepolymer; the reaction system was cooled to 55°C, 0.1 parts by weight of hydroquinone monomethyl ether was added, and 6.1 parts by weight of hydroxyethyl acrylate was slowly added dropwise. After the addition was complete, the reaction continued at 75°C for 5 hours. Infrared spectroscopy monitoring was used to determine the reaction time; when the concentration reached 2270 cm⁻¹... -1 The reaction is stopped when the characteristic absorption peak of isocyanate at the desired molecular weight completely disappears, yielding polyurethane acrylate oligomers.

[0052] Infrared spectroscopy monitoring was conducted at 2270 cm⁻¹. -1 The reaction is stopped when the characteristic absorption peak of the isocyanate group completely disappears, yielding a polyurethane acrylate oligomer of the desired molecular weight. Hydroxyethyl acrylate is used in a slightly excess manner to ensure sufficient end-isocyanate capping, and the residual trace amount of hydroxyethyl acrylate can participate in the crosslinking reaction as a reactive component during subsequent photocuring.

[0053] In the following examples, the weight parts of the perovskite quantum dot toluene dispersion are based on the total mass of the dispersion; after vacuum distillation, the toluene solvent is basically removed, and the content of perovskite quantum dots in the final coating solution is calculated based on the solid content of the dispersion.

[0054] Example 1: This embodiment provides a perovskite quantum dot composite film based on in-situ covalent anchoring and step crosslinking, and its preparation method, including the following steps: Add 20 parts by weight of lauryl methacrylate and 4 parts by weight of zinc undecenoate to a reaction vessel equipped with a temperature control and vacuum system. Set the water bath temperature to 42°C and stir at 250 rpm for 25 minutes until completely dissolved to form a transparent organic homogeneous liquid. 20 parts by weight of the perovskite quantum dot toluene dispersion prepared in Preparation Example 1 were slowly injected into the reactor using a metering pump, and the mixture was mixed at a speed of 300 rpm for 20 minutes. The temperature of the reactor was slowly raised to 50°C, and the vacuum pump was started to extract the pressure inside the reactor to the gauge pressure of -0.09MPa. Under this temperature and negative pressure, continuous vacuum distillation was carried out for 1.5 hours to extract the volatile toluene solvent and the desorbed native ligands. After the vacuum distillation is completed, the cooling circulation of the reactor jacket is started, and the temperature of the mixture in the reactor is precisely reduced to 25°C at a cooling rate of 2°C / min and then restored to normal pressure. Add 1.0 part by weight of methacryloyloxyethyl phosphate and stir at 150 rpm for 10 minutes under light-protected conditions to neutralize the acid and base. 58 parts by weight of the polyurethane acrylate oligomer prepared in Preparation Example 4, 5 parts by weight of pentaerythritol tetra(3-mercaptopropionate), 0.73 parts by weight of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, and 1.47 parts by weight of 2,2-dimethoxy-2-phenylacetophenone were added sequentially to the reactor. The vacuum was then re-evacuated to a gauge pressure of -0.09 MPa at 25°C, and vacuum degassing and mixing were performed at 200 rpm for 40 minutes to obtain a bubble-free coating solution. The coating liquid was uniformly coated onto the surface of an optical-grade polyethylene terephthalate substrate that had undergone corona treatment using a slit extrusion coating machine, and the wet film thickness was controlled to be 80 μm. The coated substrate is then transferred to a UV curing tunnel equipped with a dual-band light source. In the first temperature zone, a UVA-LED surface light source with a dominant wavelength of 405nm is activated, and the irradiance is set to 80mW / cm². 2 Irradiation for 15 seconds; in the second temperature zone, a high-power UVA-LED surface light source with a main wavelength of 365nm is activated, and the irradiation intensity is set to 1000mW / cm². 2 Irradiate for 8 seconds, and after curing, roll up to obtain the target film.

[0055] Example 2: This embodiment provides a perovskite quantum dot composite film based on in-situ covalent anchoring and step crosslinking, and its preparation method, including the following steps: Add 15 parts by weight of lauryl methacrylate and 2 parts by weight of zinc undecenoate to a reaction vessel equipped with a temperature control and vacuum system. Set the water bath temperature to 40°C and stir at 200 rpm for 20 minutes until completely dissolved. 15 parts by weight of the perovskite quantum dot toluene dispersion prepared in Preparation Example 2 were slowly injected into the reactor using a metering pump and mixed at 300 rpm for 15 minutes. The reactor temperature was slowly raised to 45°C, and the vacuum pump was started to extract the pressure inside the reactor to -0.08 MPa, which corresponds to approximately 0.02 MPa. The reactor was then continuously distilled under reduced pressure for 1 hour. After vacuum distillation, the temperature of the mixture in the vessel is reduced to 25°C and then restored to atmospheric pressure. Add 0.5 parts by weight of methacryloyloxyethyl phosphate and stir at 150 rpm for 10 minutes under light-protected conditions; 50 parts by weight of the polyurethane acrylate oligomer prepared in Preparation Example 5, 3 parts by weight of pentaerythritol tetra(3-mercaptopropionate), 0.6 parts by weight of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide and 0.9 parts by weight of 2,2-dimethoxy-2-phenylacetophenone were added sequentially. The mixture was then evacuated to -0.09 MPa at 25°C and vacuum degassed and mixed at 150 rpm for 30 minutes to obtain the coating solution. The coating solution was applied to the surface of a polyethylene terephthalate substrate, and the wet film thickness was controlled to be 50 μm. The substrate was then transferred to a UV curing tunnel, and a surface light source with a dominant wavelength of 405 nm was activated in the first temperature zone, with the irradiation intensity set to 50 mW / cm². 2 Irradiation for 10 seconds; In the second temperature zone, a surface light source with a main wavelength of 365nm is turned on, the irradiation intensity is set to 800mW / cm², and the irradiation time is 5 seconds. After curing, the film is wound up to obtain the target film.

[0056] Example 3: This embodiment provides a perovskite quantum dot composite film based on in-situ covalent anchoring and step crosslinking, and its preparation method, including the following steps: Add 25 parts by weight of lauryl methacrylate and 6 parts by weight of zinc undecenoate to a reaction vessel equipped with a temperature control and vacuum system. Set the water bath temperature to 45°C and stir at 300 rpm for 30 minutes until completely dissolved. 25 parts by weight of the perovskite quantum dot toluene dispersion prepared in Preparation Example 3 were slowly injected into the reactor using a metering pump and mixed at 300 rpm for 20 minutes. The reactor temperature was raised to 55°C, and the vacuum pump was started to extract the pressure inside the reactor to -0.095 MPa, which corresponds to approximately 0.005 MPa. The reactor was then continuously distilled under reduced pressure for 2 hours. After vacuum distillation, the temperature of the mixture in the vessel was reduced to 30°C and restored to atmospheric pressure; 2.0 parts by weight of methacryloyloxyethyl phosphate was added, and the mixture was stirred at 200 rpm for 15 minutes under light-protected conditions. 65 parts by weight of the polyurethane acrylate oligomer prepared in Preparation Example 6, 8 parts by weight of pentaerythritol tetra(3-mercaptopropionate), 0.86 parts by weight of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, and 2.14 parts by weight of 2,2-dimethoxy-2-phenylacetophenone were added sequentially. The mixture was then evacuated to -0.09 MPa at 30°C and vacuum degassed and mixed at 250 rpm for 50 minutes to obtain the coating solution. The coating liquid was applied to the surface of the polyethylene terephthalate substrate, and the wet film thickness was controlled to be 100 μm. The substrate is transferred to the UV curing tunnel, and a surface light source with a dominant wavelength of 405nm is activated in the first temperature zone, with the irradiation intensity set to 100mW / cm². 2 Irradiation for 20 seconds; The second temperature zone activates a surface light source with a main wavelength of 365nm, and the irradiance is set to 1200mW / cm². 2 Irradiate for 10 seconds, and after curing, roll up to obtain the target film.

[0057] Example 4: This embodiment provides a perovskite quantum dot composite film based on in-situ covalent anchoring and step crosslinking, and its preparation method, including the following steps: Add 18 parts by weight of lauryl methacrylate and 5 parts by weight of zinc undecenoate to a reaction vessel equipped with a temperature control and vacuum system. Set the water bath temperature to 42°C and stir at 250 rpm for 25 minutes until completely dissolved. 18 parts by weight of the perovskite quantum dot toluene dispersion prepared in Preparation Example 1 were slowly injected into the reactor using a metering pump and mixed at 300 rpm for 20 minutes. The reactor temperature was raised to 48°C, and the vacuum pump was started to extract the pressure inside the reactor to -0.09 MPa, which corresponds to approximately 0.01 MPa. The reactor was then continuously distilled under reduced pressure for 1.5 hours. After vacuum distillation, the temperature of the mixture in the vessel was reduced to 28°C and restored to atmospheric pressure; 1.5 parts by weight of methacryloyloxyethyl phosphate was added, and the mixture was stirred at 150 rpm for 12 minutes under light-protected conditions. 60 parts by weight of the polyurethane acrylate oligomer prepared in Preparation Example 4, 6 parts by weight of pentaerythritol tetra(3-mercaptopropionate), 0.71 parts by weight of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, and 1.29 parts by weight of 2,2-dimethoxy-2-phenylacetophenone were added sequentially. The mixture was then evacuated to -0.09 MPa at 28°C and vacuum degassed and mixed at 200 rpm for 40 minutes to obtain the coating solution. The coating liquid was applied to the surface of the polyethylene terephthalate substrate, and the wet film thickness was controlled to be 70 μm. The substrate is transferred to the UV curing tunnel, and a surface light source with a dominant wavelength of 405nm is activated in the first temperature zone, with the irradiation intensity set to 60mW / cm². 2 Irradiation for 18 seconds; in the second temperature zone, a surface light source with a main wavelength of 365nm is activated, and the irradiation intensity is set to 900mW / cm². 2 Irradiate for 6 seconds, and after curing, roll up to obtain the target film.

[0058] Comparative Example 1: Compared with Example 1, the difference is that 4 parts by weight of zinc undecenoate in the formulation are replaced with zinc oleate (excluding terminal double bonds) calculated based on the molar number of zinc carboxylate groups, and the total non-volatile component mass of the formulation is kept consistent by adjusting the amount of lauryl methacrylate. All other aspects are the same.

[0059] Comparative Example 2: Compared to Example 1, the difference lies in the absence of pentaerythritol tetra(3-mercaptopropionate), and the addition of polyurethane acrylate oligomer was increased by 5 parts by weight to make up the difference; all other aspects remained the same. This comparative example was used to examine the stability difference caused by the inability of zinc undecenoate terminal alkenyl groups to effectively integrate into the crosslinking network when a mercapto bridging monomer is lacking.

[0060] Comparative Example 3: The difference from Example 1 is that methacryloyloxyethyl phosphate is not added; otherwise, they are the same.

[0061] Comparative Example 4: Compared with Example 1, the difference is that the curing step eliminates the surface light source irradiation with a main wavelength of 405nm in the first temperature zone, and directly transfers the substrate to the second temperature zone for surface light source irradiation curing with a main wavelength of 365nm. All other steps are the same.

[0062] Test Example 1: This test example uses samples from each stage of the preparation process in Example 1 as the test objects, and uses Fourier transform infrared spectroscopy to track the changes in the absorption peaks of relevant characteristic functional groups.

[0063] The experimental steps are as follows: 1) Sample extraction: Samples were taken at four stages during the preparation process of Example 1, and were designated as Sample A, Sample B, Sample C, and Sample D. Sample A was the mixture extracted after vacuum distillation, cooling to 25°C, and then restoring to normal pressure. Sample B is a coating solution extracted after adding methacryloyloxyethyl phosphate and degassing and mixing in the dark; Sample C is a semi-cured film extracted after being irradiated by a UVA-LED surface light source with a main wavelength of 405nm in the first temperature zone; Sample D is a fully cured film extracted after being irradiated by a high-power UVA-LED surface light source with a main wavelength of 365nm in the second temperature zone.

[0064] 2) Sample preparation: For liquid samples A and B, the potassium bromide salt film coating method was used to prepare infrared test samples; for solid samples C and D, the attenuated total reflection attachment was used to directly attach the film to the surface of the diamond crystal for testing.

[0065] 3) Spectral Acquisition: Place the prepared sample in the sample chamber of the Fourier transform infrared spectrometer. Set the scanning range to 4000 cm⁻¹. -1 Up to 400cm -1 The resolution is 4cm. -1 The scan was performed 32 times. The infrared absorption spectra of each sample were recorded using air or a blank potassium bromide plate as background subtraction.

[0066] 4) Data processing and peak area integration: After acquiring spectral data, baseline calibration is performed for specific characteristic absorption peaks, and the peak area is integrated and calculated.

[0067] The selected characteristic peaks include approximately 3300 cm⁻¹ -1 The nearby NH stretching vibration peak may contain the combined contributions of oleylamine NH and urethane NH in polyurethane acrylate oligomers, and therefore should only be used as an auxiliary reference peak for ligand residue changes; the characteristic thiol-SH peak representing pentaerythritol tetra(3-mercaptopropionate) (approximately 2570 cm⁻¹) -1 The characteristic absorption peak at approximately 1640 cm⁻¹ represents the terminal alkenyl group of zinc undecenoate. -1 The C=C stretching vibration peak at that point was used as a reference peak, and combined with approximately 910 cm⁻¹ -1 and 990cm -1 The out-of-plane bending vibration peak of the terminal alkenyl group =CH2 was used as an auxiliary indicator. And the C=C characteristic peak (approximately 810 cm⁻¹) representing the acrylate double bond in polyurethane acrylate oligomers and lauryl methacrylate. -1 To reduce errors caused by film thickness or sampling amount, the carbonyl C=O stretching vibration peak (approximately 1720 cm⁻¹) was selected. -1 The area of ​​each characteristic peak is used as a normalized reference peak, and the relative area ratio of each characteristic peak to the reference peak is calculated.

[0068] It should be noted that due to differences in composition and sample preparation methods between samples A to D, 1720cm -1 The carbonyl peak is not used as an absolute quantitative internal standard across stages; it is only used to assist in comparing the changing trends of related characteristic peaks in the same system.

[0069] Table 1. Test results of relative area ratio of infrared characteristic peaks of samples at each preparation stage in Example 1

[0070] Based on the data in Table 1 and the appendix Figure 1 and attached Figure 10 It can be seen that it includes Figure 10 Sample A is the mixture after vacuum distillation and cooling to normal pressure; Sample B is the coating solution after adding methacryloyloxyethyl phosphate and degassing and mixing; Sample C is the semi-cured film after initial curing with a 405 nm light source; Sample D is the fully cured film after deep curing with a 365 nm light source. Sample A contains 3300 cm⁻¹ -1 The relatively low relative area of ​​the nearby NH peaks preliminarily indicates that the content of free or weakly adsorbed oleylamine ligands in the system has been significantly reduced after the vacuum distillation process.

[0071] Since the polyurethane acrylate oligomers introduced in subsequent samples also contain urethane NH structures, therefore 3300cm -1 The nearby absorption peaks are not used alone as a quantitative basis for oleylamine residue. Comparing samples B and C, after irradiation with a 405nm light source in the first temperature zone, the -SH peak and the 1640cm peak... -1 The relative area ratios of the terminal C=C peaks at the twentieth point showed a synchronous and significant decreasing trend, decreasing from 0.421 to 0.115 and from 0.384 to 0.093, respectively.

[0072] At this time, 810cm -1 The relative area ratio of the C=C peak of the acrylate at the 810 cm⁻¹ site decreased only slightly, remaining at 0.763. This phenomenon indicates that the long-wavelength, weak initiation conditions in the first temperature region preferentially promoted the mercapto-alkene click reaction, achieving preliminary cross-linking of the anchored quantum dots of zinc undecenoate. Combined with the synchronous attenuation of the terminal alkenyl auxiliary characteristic peak, this further supports the judgment that the terminal alkenyl groups of zinc undecenoate participated in the pre-cross-linking reaction. Further comparison of samples C and D shows that after irradiation with a 365 nm light source in the second temperature region, the relative area ratio at 810 cm⁻¹... -1 The relative area ratio of the acrylate C=C peak at the point of origin dropped sharply from 0.763 to 0.038, indicating that the acrylate double bonds in the system underwent deep free radical polymerization under short-wavelength high-energy excitation, forming a dense cross-linked network. The aforementioned data patterns reflect that the preparation method provided by this invention can complete the cross-linking reaction according to the designed step sequence, realizing the in-situ anchoring of quantum dots and the ordered solidification of the network.

[0073] Combined with subsequent TEM and HRTEM morphology observations, it can be seen that the thiol-olefin reaction and acrylate polymerization process reflected by the changes in infrared characteristic peaks do not only occur in the free monomer system, but also correspond to the network access process of zinc undecenoate ligands on the surface of quantum dots, thus providing a structural basis for the in-situ anchoring of quantum dots in the polymer matrix.

[0074] Test Example 2: This test example uses the coating liquids prepared after the defoaming and mixing stage of Example 1 and Comparative Example 3 as experimental objects. The room temperature kinetic stability of the system is examined by monitoring the change in apparent viscosity over a specific time period.

[0075] The experimental steps are as follows: 1) Preparation and sampling of experimental subjects: The coating solution obtained by vacuum degassing and mixing at 25°C in Example 1 was extracted as the test group sample; at the same time, the coating solution obtained by degassing and mixing under the same conditions in Comparative Example 3 (without the addition of methacryloyloxyethyl phosphate) was extracted as the control group sample. The extracted samples were placed in sealed brown light-proof glass bottles for testing.

[0076] 2) Instrument Preparation and Parameter Setting: A rotational rheometer equipped with a Peltier temperature control system was used, and a parallel plate test fixture with a diameter of 40 mm was selected. The test temperature was set to 25℃, the controlled environment was kept in the dark, and the constant shear rate was set to 10 s. -1 The test gap was set to 1000μm.

[0077] 3) Initial viscosity test: Each group of samples was loaded onto the test platform of the rheometer, and excess sample at the edges was scraped off. After the temperature reached equilibration to 25°C, the initial apparent viscosity of the sample immediately after loading was recorded (recorded as 0 hours).

[0078] 4) Continuous monitoring and data recording: Keep the samples in a sealed and light-protected environment. At the set time points (2 hours, 4 hours, 8 hours, 12 hours, 16 hours, and 24 hours), conduct rheological tests on the test group and control group samples under the same shear conditions, and record the corresponding apparent viscosity values. If the apparent viscosity of the sample increases exponentially and macroscopic gel solidification (loss of fluidity) occurs during the test, stop the subsequent time point tests for that sample and mark it as a gel state in the record table.

[0079] Table 2. Test results of apparent viscosity change of coating liquid in Example 1 and Comparative Example 3 at 25°C over time

[0080] Based on the data in Table 2 and the appendix Figure 2 Example 1 and Comparative Example 3 had similar apparent viscosities in the initial stage (0 hours), which were 852 mPa·s and 845 mPa·s, respectively. During the subsequent 24-hour monitoring period, the apparent viscosity of Example 1 showed high stability, with only slight fluctuations in the later stage. After 24 hours, the viscosity remained at 915 mPa·s, still exhibiting good fluid processing performance and coating process applicability.

[0081] In contrast, Comparative Example 3, which did not contain methacryloyloxyethyl phosphate (MOEP), showed a significant increase in apparent viscosity after standing for 2 hours, reaching 1362 mPa·s; after standing for 4 hours, it surged to 4987 mPa·s; and at the 8-hour mark, macroscopic gelation occurred, completely losing its fluidity.

[0082] Although most of the free or weakly adsorbed ligands are removed during vacuum distillation of the quantum dot dispersion, trace amounts of oleylamine may still remain in the system. This residual oleylamine is weakly basic and can act as an alkaline catalyst under ambient temperature and light-protected conditions, initiating a Michael addition dark reaction between the highly reactive thiol groups in pentaerythritol tetra(3-mercaptopropionate) and the acrylate double bonds in the system, leading to premature disordered cross-linking of the polymer network.

[0083] The MOEP added in Example 1 contains acidic phosphate groups, whose dissociated protons preferentially protonate the free oleylamine, thus interrupting the alkaline catalytic pathway of the aforementioned dark reaction. The difference in rheological data confirms the feasibility of the acid-base kinetic stabilization mechanism. This design controls the stability of the highly reactive thiol-alkene system under non-light conditions, ensuring the smooth implementation of the subsequent orthogonal step-curing process.

[0084] Test Example 3: This test example uses the perovskite quantum dot dispersion prepared in Example 1 and the final cured film prepared in Example 1 as experimental objects. By testing their photoluminescence spectrum (PL spectrum) and full width at half maximum (FWHM), it is verified whether the crystal structure and optical intrinsic properties of the quantum dots are damaged during the film preparation process.

[0085] The experimental steps are as follows: 1) Sample preparation: Take 0.1 mL of the perovskite quantum dot toluene dispersion prepared in Example 1, add it to 2.9 mL of toluene solvent for dilution, and put it into a standard quartz cuvette as a reference liquid sample; cut the cured film prepared in Example 1 into a size of 3 cm × 3 cm, fix it on the solid film test holder as a test solid sample.

[0086] 2) Instrument debugging and parameter setting: A fluorescence spectrophotometer was used for testing. The excitation source wavelength was set to 365nm, the emission spectrum scanning range was set to 480nm to 560nm, the scanning speed was set to 240nm / min, and the slit widths on both the excitation and emission sides were set to 2.0nm.

[0087] 3) Spectral data acquisition: Place the cuvette containing the liquid sample and the solid support with the thin film sample into the sample chamber of the fluorescence spectrophotometer, respectively.

[0088] The scanning program is started, and the instrument automatically records the luminescence intensity within the set wavelength range. During the test, the sample chamber is kept in a dark environment. After subtracting the background baseline, the luminescence intensity values ​​corresponding to each wavelength are extracted and normalized based on the highest luminescence intensity.

[0089] Table 3. Normalized photoluminescence spectral sampling data of the dispersion prepared in Example 1 and the cured film prepared in Example 1

[0090] Based on the data and spectral morphology in Table 3, and the appendix Figure 3The emission peak wavelength of the dispersion in Example 1 was 516 nm, while that of the cured film in Example 1 was 517 nm. The shift in emission peak position before and after film formation was only 1 nm, which is within the normal fluctuation range caused by instrument testing errors and changes in refractive index environment. Meanwhile, the half-width at half-maximum (WHM) data extracted from the attenuation gradient of the spectral sampling data shown in Table 3 showed that the WHM of the dispersion in Example 1 was approximately 15.3 nm, and that of the cured film in Example 1 was approximately 16.3 nm, showing no obvious broadening phenomenon.

[0091] In the ligand substitution process, zinc undecanoate replacing weakly bound ligands structurally compensated for bromine-rich vacancy defects on the surface, preventing the introduction of deep-level defect states that would cause nonradiative recombination. During photocuring, the polymer network formed by stepwise orthogonal crosslinking achieved monomer-level spatial isolation for quantum dots with terminal double bonds. This indicates that the bursting shrinkage effect of the matrix resin was released by the previous "soft anchoring" process, preventing the generation of compressive stress that would lead to physical aggregation of quantum dots. This avoids energy resonance transfer and self-absorption effects caused by quantum dot aggregation, maintaining the high color purity and intrinsic lattice state of the inorganic light-emitting core.

[0092] This result is corroborated by the clear lattice fringes observed in subsequent HRTEM, indicating that the ligand exchange, solvent replacement, and step-by-step curing processes in this invention did not significantly damage the crystal structure of CsPbBr3 quantum dots.

[0093] Test Example 4: This test example uses the fully cured films prepared in Example 1, Comparative Example 1, and Comparative Example 2 as experimental objects. The decay of the absolute fluorescence quantum yield (PLQY) of the film is continuously monitored through a double 85% damp heat aging test to verify the macroscopic effect of the in-situ covalent anchoring mechanism on improving the weather resistance of the material.

[0094] The experimental steps are as follows: 1) Experimental Subject Preparation and Pretreatment: Optical films prepared in Example 1 (prepared entirely using the in-situ covalent anchoring mechanism of this invention), Comparative Example 1 (using zinc oleate without terminal double bonds to replace zinc undecenoate), and Comparative Example 2 (without adding thiol bridging monomers) were used. Each group of films was cut to a standard size of 2cm × 2cm, and three parallel samples were prepared for each group. The initial absolute fluorescence quantum yield (PLQY) of each sample before aging was recorded as the initial PLQY (test time point was 0 hours). Three parallel samples were set for each group, and the test results were expressed as the average value, with the standard deviation calculated. The test samples were bare composite films without additional edge sealing treatment, and the film thickness was consistent with the preparation conditions of the corresponding examples.

[0095] 2) Aging environment setting: A constant temperature and humidity test chamber was used. The chamber temperature was set to 85℃ and the relative humidity to 85% (double 85 conditions). After the test chamber stabilized and reached the set parameters, the high-temperature resistant sample rack containing each group of film samples was placed inside the chamber.

[0096] 3) Data extraction and testing: At specific time points in the aging process (100, 200, 400, 600, 800, and 1000 hours), the test chamber was opened and the corresponding samples for each group were taken out. The taken-out samples were placed in a desiccator to cool to room temperature of 25°C (approximately 30 minutes).

[0097] 4) Optical Parameter Acquisition: An absolute fluorescence quantum yield (PLQY) testing system equipped with an integrating sphere was used. The excitation wavelength was set to 450 nm. The cooled thin film samples were sequentially fixed in the sample holder of the integrating sphere, and photoluminescence and scattering spectra were acquired. The absolute quantum yield value was calculated by the system software. After the test, the average PLQY at the corresponding time point was divided by its initial PLQY to calculate the fluorescence quantum yield retention rate. The tested samples were then returned to the constant temperature and humidity chamber for further aging.

[0098] Table 4. Data on the PLQY retention rate over time under double 85 aging conditions in Example 1, Comparative Examples 1 and 2 (n=3, results are average values).

[0099] Based on the data in Table 4 and the appendix Figure 4 After 1000 hours of extreme damp heat aging, Example 1 still maintained a PLQY retention rate of 85.3%, and maintained high luminous efficiency under test conditions without additional edge sealing, demonstrating excellent weather resistance. In contrast, Comparative Examples 1 and 2 showed extremely rapid degradation, with their retention rates dropping to 6.5% and 13.8% respectively at the 1000-hour mark, essentially losing their actual luminous efficacy.

[0100] Comparative Example 1 used zinc oleate without terminal double bonds. Although this ligand can produce surface passivation, it cannot participate in network copolymerization during the photocuring stage and remains in a purely physical dispersion state. Under high temperature and high humidity, free zinc oleate undergoes phase separation in the polymer matrix and acts as an internal plasticizer, expanding the free volume of polymer chain segments, allowing water vapor and oxygen to penetrate freely and accelerating the lattice destruction of quantum dots.

[0101] Comparative Example 2 used zinc undecenoate but did not introduce a mercapto monomer. Due to the significant difference in polymerization reactivity between the terminal olefin (the tail-end double bond of zinc undecenoate) and the acrylate double bond, the terminal olefin is extremely difficult to integrate into the acrylate backbone during conventional UV-induced polymerization. This results in the ligands possessing polymerizable groups, but most do not achieve effective bonding with the matrix, and their resistance to water and oxygen penetration is similar to that of physical blending.

[0102] Example 1: Zinc undecenoate on the surface of quantum dots was pre-linked with pentaerythritol tetra(3-mercaptopropionate) via click chemistry. Subsequently, the quantum dots were chemically anchored to the dense cross-linked network nodes through the curing of the acrylate network via thiol participation. This in-situ anchoring structure, constructed by covalent bonds, restricts the diffusion paths of water and oxygen molecules at the interface and inhibits the thermal desorption and desorption behavior of the ligands. The comparison of macroscopic aging data verifies the necessity of using zinc undecenoate combined with a thiol-olefin cross-linked network design to achieve long-term material stability.

[0103] Based on the TEM and HRTEM morphology results, it can be seen that the quantum dots in Example 1 maintain a good dispersion state in the composite film, and there is an amorphous polymer coating region around them. This microstructure and the cross-linking reaction reflected by the infrared test together indicate that the quantum dots are spatially confined by the polymer network, so they are not prone to migration, aggregation and ligand desorption during the humid heat aging process.

[0104] Test Example 5: This test example uses the uncured coating liquid (liquid reference) in Example 1, the stepped curing film prepared in Example 1, and the film prepared in Comparative Example 4 (omitting the long wavelength pre-curing in the first temperature zone and directly using 365nm single-step burst curing) as experimental objects. By comparing and testing the photoluminescence spectral parameters of the three, the actual effect of the orthogonal stepped curing process on alleviating the internal stress of curing shrinkage and inhibiting quantum dot aggregation is examined.

[0105] The experimental steps are as follows: 1) Preparation of reference and test samples: Take a small amount of the defoamed and mixed liquid coating liquid from Example 1, coat it on a clean glass slide, cover it with a coverslip, and gently press to remove air to make a liquid sandwich test sample, which serves as an optical reference group unaffected by curing stress.

[0106] Cut 2cm×2cm portions of the fully cured film from Example 1 and Comparative Example 4, respectively, and fix them on a solid sample holder as a control test group.

[0107] 2) Spectroscopic testing environment setup: A fluorescence spectrophotometer was used. The excitation source wavelength was adjusted to 400nm to avoid overlap and interference between the excitation and emission light. The emission spectrum acquisition range was set to 490nm to 550nm, and the scanning interval was set to 1nm.

[0108] 3) Spectral Data Acquisition and Parameter Extraction: The liquid reference group and two groups of thin film samples were placed in the sample chamber and scanned at the same ambient temperature (25℃). The data on the change of luminescence intensity with wavelength were recorded, and the peak value of the highest luminescence intensity was normalized. Based on the normalized spectral curves, the center wavelength of the luminescence peak and the full width at half maximum (FWHM) characteristic values ​​of each sample were extracted.

[0109] Table 5. Relative Normalized Photoluminescence Spectra of Coating Liquid Baseline and Thin Films of Example 1 and Comparative Example 4

[0110] Based on the data in Table 5 and the corresponding generated spectral curve characteristics, as well as the appendix... Figure 5 The center wavelength of the emission peak of the liquid coating reference is located around 516 nm, and its half-maximum width (WHM) is relatively narrow, exhibiting the intrinsic luminescence state of quantum dots under stress-free conditions. The emission peak position of the film in Example 1 (normalized intensity of 1.000 at 515 nm) highly coincides with the reference state, and the spectral envelope width does not change significantly. Based on the sampling data in Table 5, the WHM of the liquid coating reference is estimated to be approximately 13.0 nm, and the WHM of the film in Example 1 is approximately 13.6 nm, with little difference between the two.

[0111] In contrast, the emission peak center of the Comparative Example 4 film shifted significantly to 524 nm, exhibiting a redshift of approximately 8 nm. Furthermore, the transition region between its trough and peak became gentler, and the full width at half maximum (FWHM) of the spectrum broadened considerably. Based on the sampling data in Table 5, the FWHM of the Comparative Example 4 film was estimated to be approximately 23.3 nm, significantly larger than that of the liquid coating reference and the film of Example 1.

[0112] The physicochemical root cause of the aforementioned optical drift differences lies in the stress management mechanism of the curing path. Comparative Example 4 skipped the long-wavelength pre-curing stage and was directly subjected to high-intensity, short-wavelength ultraviolet radiation. All acrylate double bonds in the system underwent violent chain-like free radical polymerization in a very short time. This single-step explosive polymerization caused irreversible and drastic volume shrinkage of the polymer network. The enormous shrinkage stress squeezed inward, forcing the originally uniformly dispersed inorganic quantum dots to physically aggregate. When the distance between the luminescent centers shortened to a specific threshold, energy resonance transfer (FRET) and photon self-absorption effects occurred between adjacent quantum dots, macroscopically manifesting as a redshift in the emission wavelength and a decrease in color purity. Example 1 employed an orthogonal stepwise curing strategy. Under low-intensity radiation of 405 nm, only a few free radicals were excited to initiate a mercapto-olefin addition reaction with extremely low activation energy.

[0113] Within this first temperature range, the system retains high segment mobility, and the quantum dots are initially anchored by a flexible sulfide bond network during the liquid rheological phase, resulting in extremely low volume shrinkage. Upon entering the second temperature range of 365 nm, even with rapid cross-linking and shrinkage of the macroscopic matrix, the quantum dots, having already achieved a robust covalently isolated arrangement, have their subsequent shrinkage stress absorbed and dispersed by the pre-formed flexible buffer network. This test data confirms that orthogonal step-curing technology can effectively eliminate the optical degradation effect of coating internal stress on inorganic nanocrystal structures.

[0114] Test Example 6: This test example uses the coating liquid provided in Example 1 and the same formulation coating liquid treated with the single-step 365nm curing process of Comparative Example 4 as experimental objects. By preparing coatings with different thickness gradients and testing their internal residual stress and pull-off adhesion, the substantial effect of orthogonal step curing process combined with methacryloyloxyethyl phosphate on releasing curing shrinkage stress and improving macroscopic interfacial bonding strength is examined.

[0115] The experimental steps are as follows: 1) Substrate Coating and Gradient Thickness Preparation: The liquid coating solution after the degassing and mixing stage of Example 1 and the corresponding liquid coating solution of Comparative Example 4 were extracted. Standard polyethylene terephthalate (PET) films with corona-treated surfaces were selected as test substrates. A high-precision automatic coating machine was used to coat multiple substrates with different wet film thicknesses by adjusting the gap of the wire bar doctor blade, ensuring that the target dry film thickness of each coating after complete curing was controlled at approximately 20 μm, 40 μm, 60 μm, 80 μm, and 100 μm, respectively.

[0116] 2) Coating Curing Treatment: The PET substrate coated with the coating liquid of Example 1 was sequentially conveyed through the first temperature zone (405nm surface light source) and the second temperature zone (365nm surface light source) according to predetermined parameters to complete the stepped curing; the PET substrate coated with the coating liquid of Comparative Example 4 was directly conveyed to a 365nm high-power ultraviolet light source for single-step explosive polymerization and crosslinking curing. All cured film samples were placed in a constant temperature and humidity chamber (25℃, 50% relative humidity) for 24 hours to eliminate interference from environmental and thermodynamic factors.

[0117] 3) Residual Stress Test Inside the Film: The internal stress of the coating was measured using a laser thin film stress meter. Each group of coated samples, after being left to stand, was placed on a test platform. A laser beam was used to scan the back of the substrate, measuring the change in the radius of curvature of the substrate caused by the shrinkage during coating curing. Based on the Stoney formula, combined with the elastic modulus of the PET substrate, Poisson's ratio, the original thickness of the substrate, and the measured dry film coating thickness, the test system calculated the average residual stress value inside each sample. For samples with higher dry film thickness, since the ratio of coating thickness to PET substrate thickness increased, the result was used as the apparent residual stress for relative comparison between different curing processes. Three parallel samples were tested for each thickness group, and the average value was recorded.

[0118] 4) Pull-off adhesion failure test: Macroscopic adhesion test shall be performed in accordance with GB / T5210 standard.

[0119] A standard aluminum test cylinder (spindle) with a diameter of 20 mm was vertically bonded to the surface of the cured coating using a high-strength two-component epoxy adhesive. The adhesive layer was cured at room temperature for 24 hours to allow it to fully cure. Before testing, the back of the PET film was flattened and fixed to a rigid support plate to reduce the impact of bending deformation of the flexible substrate on the adhesion results of the pull-off test.

[0120] An aluminum cylinder was connected using an automatic adhesion pull-off tester, and the vertical tensile rate was set to 1.0 MPa / s.

[0121] The critical pull-out force at the moment when the coating completely peels off or breaks from the PET substrate surface is recorded, and the pull-out adhesion strength (MPa) is calculated. The failure modes are also recorded, including coating / PET interface failure, coating cohesive failure, and adhesive layer failure; when adhesive layer failure occurs, this data is not included in the effective adhesion result.

[0122] Table 6. Residual internal stress and adhesion test data of coatings with different thicknesses in Example 1 and Comparative Example 4 (n=3, results are average values)

[0123] Test Example 7: This test example uses the cured optical films prepared in Example 1 and Comparative Example 4 as experimental objects. The interfacial adhesion stability of the films under the dual effects of extremely high thermal stress and water molecule penetration is examined by using the standard cross-cut test combined with continuous boiling water aging treatment.

[0124] The experimental steps are as follows: 1) Experimental subject preparation and pretreatment: Cured films attached to the surface of PET substrates were extracted from Example 1 (using dual-band orthogonal step curing) and Comparative Example 4 (using single-step UV burst curing). Each group of films was cut into several test samples with a size of 10cm×10cm.

[0125] 2) Initial Adhesion Test: Before aging treatment, a cross-cut adhesion tester conforming to GB / T9286 was used to cross-cut the central area of ​​each sample surface, forming 100 grids with a spacing selected according to the coating thickness. For samples with lower dry film thickness, a 1mm×1mm grid was used; for samples with higher thickness, a 2mm×2mm grid was used to ensure the comparability and validity of the cross-cut test results. The scratch depth was controlled to just penetrate the coating and touch the PET substrate surface. Standard 3M test tape was applied smoothly to the grid area and compacted to remove air. After standing for a specific time, the tape was peeled off at a uniform speed at an angle close to 60°.

[0126] Subsequently, image processing software was used to scan and calculate the test area, and the percentage of the coating peeling area to the total grid area was recorded in the initial state.

[0127] 3) Boiling water aging treatment: Place the sample block that has completed the initial test and has left a sufficient blank area into a constant temperature water bath device. The water bath medium is deionized water. Heat and maintain the water bath temperature at 100℃ boiling state, so that the sample block is completely immersed in boiling water for continuous accelerated aging treatment.

[0128] 4) Staged Sampling and Retesting: At the 2, 4, 6, 8, and 10-hour boiling water treatment stages, the corresponding samples were removed from the water bath. The surface moisture of the samples was absorbed with a lint-free cloth and allowed to stand at 25°C for 2 hours to recover. Subsequently, the cross-cutting and tape peeling operations in step 2) were repeated on the undamaged flat areas of the samples, and the percentage of coating peeling area at each aging time stage was recorded. The average value of three parallel sample areas was taken for each test group.

[0129] Table 7. Percentage of area detached during boiling water aging test in Example 1 and Comparative Example 4 (n=3, results are average values)

[0130] According to the data in Table 7, Example 1 and Comparative Example 4 exhibited drastically different evolution patterns in their interfacial adhesion in the initial state (0 hours) and after undergoing high-intensity boiling aging. In the initial state without aging, Example 1 showed a peeling area of ​​0.0%, demonstrating excellent substrate adhesion; while Comparative Example 4 showed 7.6% edge chipping at the initial test. As the boiling water treatment time increased, the peeling area of ​​Comparative Example 4 rapidly expanded, reaching nearly half (47.9%) after 4 hours of boiling, and almost completely peeling off (96.8%) after 10 hours, rendering it unusable. After undergoing 10 hours of extreme boiling water penetration, the peeling area of ​​Example 1 only slowly increased to 12.1%, and the overall coating still maintained a relatively intact mesh structure.

[0131] The differences in macroscopic physical failure are closely related to cross-linking curing kinetics and interfacial chemical bonding. In Comparative Example 4, due to the omission of the long-wavelength, low-intensity pre-curing stage, polymerization directly occurred under high-intensity light at 365 nm. The huge shear stress generated by the instantaneous contraction of the polymer network accumulated at the physical interface between the coating and the PET film. This unreleased residual stress weakened the van der Waals forces at the interface. When the heat energy provided by boiling water and the swelling effect of water molecules were superimposed, the stress release tendency directly led to macroscopic cracking and delamination. In Example 1, the orthogonal stepwise curing mechanism utilized the photo-initiated mercapto-olefin click pre-cross-linking reaction in the first temperature zone to construct a low-density flexible network with a buffering effect, maximizing the dissipation of shrinkage stress generated by subsequent macroscopic curing.

[0132] Meanwhile, the methacryloyloxyethyl phosphate (MOEP) monomer added to the formulation system of Example 1 not only participates in acid-base stabilization, but its highly polar phosphate groups tend to accumulate at the interface of the corona-treated PET substrate during the coating and leveling stage. These groups form multiple interfacial forces with the oxygen-containing functional groups such as ester, hydroxyl, and carboxyl groups on the PET substrate surface, including hydrogen bonds, dipole-dipole interactions, and acid-base interactions. This chemical bond-level interfacial anchoring force, in conjunction with the stress release mechanism, blocks the capillary penetration path of high-temperature water molecules along interfacial defects, maintaining the long-term mechanical and structural integrity of the coating.

[0133] It should be noted that the above test data are relative comparison results obtained under the same sample preparation and testing conditions, used to illustrate the effects of different formulation components and different curing paths on the optical stability, interfacial adhesion, and resistance to damp heat of perovskite quantum dot composite films. Actual values ​​may fluctuate to some extent depending on the batch of quantum dots, coating thickness, substrate surface treatment degree, light intensity distribution of curing equipment, and test environment conditions.

[0134] Test Example 8: This test example uses the quantum dot monomer dispersion system prepared in Example 1 and the finally cured perovskite quantum dot composite film as test objects. The dispersion state of quantum dots in the system and their microscopic binding state with the polymer network are observed by transmission electron microscopy.

[0135] The experimental steps are as follows: 1) Sample preparation: Take the quantum dot monomer dispersion system after vacuum distillation and cooling to 25°C in Example 1, dilute it appropriately with lauryl methacrylate, drop it onto an ultrathin carbon film copper grid, and let it evaporate naturally until there is no obvious liquid flow. This is then used as a low-magnification TEM test sample.

[0136] 2) Take the composite film after final curing in Example 1, and perform low-temperature ultrathin slicing to obtain a thin film sample with a thickness of about 70-100 nm. Transfer the sample to a copper grid as a high-resolution transmission electron microscope test sample.

[0137] 3) The above samples were observed using a transmission electron microscope. Low-magnification TEM was used to evaluate the overall dispersion state of the quantum dots, while high-resolution TEM was used to observe the quantum dot lattice fringes and the surrounding polymer coating or anchoring structure.

[0138] Test results are as follows Figure 8 and Figure 9 As shown, by Figure 8 As can be seen, after zinc undecanoate ligand exchange and vacuum distillation solvent replacement treatment, CsPbBr3 perovskite quantum dots exhibit a relatively uniform dispersion in the monomer system, and no large-sized aggregates were observed in the field of view, indicating that the introduction of zinc undecanoate improved the compatibility between quantum dots and lauryl methacrylate and subsequent polymer matrix.

[0139] Depend on Figure 9 As can be seen, CsPbBr3 quantum dots with clear lattice fringes can be observed in the composite film, with interplanar spacings of approximately 0.41 nm and 0.29 nm, corresponding to the relevant crystal plane characteristics of CsPbBr3 crystals, respectively. Low-contrast amorphous regions are visible around the quantum dots, corresponding to the cured polyurethane acrylate crosslinking network and the zinc undecenoate anchoring layer. Combined with the coating state at the quantum dot boundaries in the figure, it can be seen that the quantum dots do not exist in a bare or simply physically dispersed form, but are confined within the polymer network through photocuring crosslinking involving zinc undecenoate ligands, mercapto monomers, and acrylate oligomers.

[0140] The above TEM and HRTEM results further illustrate that the preparation method provided by the present invention can achieve uniform dispersion and in-situ anchoring of quantum dots in composite films while maintaining the crystal structure of CsPbBr3 quantum dots, providing a microstructural basis for suppressing quantum dot migration, aggregation and fluorescence decay during subsequent wet heat aging.

[0141] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A perovskite quantum dot composite thin film, characterized in that, The components include the following parts by weight: 15-25 parts of perovskite quantum dot dispersion; 15-25 parts of lauryl methacrylate; 2-6 parts of zinc undecenoate; 0.5–2.0 parts of methacryloyloxyethyl phosphate; 50-65 parts of polyurethane acrylate oligomer; 3-8 parts of thiol monomer; Photoinitiator 1.5–3.0 parts; The photoinitiator is a mixture of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide and 2,2-dimethoxy-2-phenylacetophenone; The perovskite quantum dot composite film undergoes dual-band continuous irradiation curing during the curing stage. It first undergoes preliminary curing in the first temperature zone with a main wavelength of 405 nm; then it undergoes deep cross-linking in the second temperature zone with a main wavelength of 365 nm.

2. The perovskite quantum dot composite thin film according to claim 1, characterized in that, The polyurethane acrylate oligomer is synthesized by reacting polycaprolactone diol, isophorone diisocyanate and hydroxyethyl acrylate, and has a number average molecular weight of 1680-2900 g / mol.

3. The perovskite quantum dot composite thin film according to claim 1, characterized in that, The solid content of the perovskite quantum dot dispersion is 10wt% to 15wt%. The perovskite quantum dots are all inorganic perovskite quantum dots, whose inorganic cores are generated by the reaction of lead bromide and cesium bromide in an equimolar ratio, and whose surfaces are coated with oleic acid and oleylamine ligands, and whose dispersion solvent is toluene.

4. A method for preparing a perovskite quantum dot composite thin film according to any one of claims 1-3, characterized in that, Includes the following steps: S1. After dissolving lauryl methacrylate and zinc undecenoate, add the perovskite quantum dot dispersion and stir to mix. S2. Under reduced pressure, vacuum distillation is carried out to remove the original solvent from the dispersion to obtain the quantum dot monomer dispersion system. S3. Methacryloxyethyl phosphate, polyurethane acrylate oligomer, mercapto monomer and photoinitiator are added sequentially to the quantum dot monomer dispersion system, and the mixture is degassed and mixed under yellow light to obtain a photocurable coating. S4. Apply the photocurable coating onto the substrate to form a wet film; S5. The substrate coated with wet film is placed in an ultraviolet curing device and cured by dual-band continuous irradiation to obtain the composite film. The dual-band continuous irradiation curing includes: firstly, preliminary curing in a first temperature zone, with a main wavelength of 405nm and an irradiation intensity of 50–100mW / cm². 2 The irradiation time is 10–20 seconds; followed by deep cross-linking in a second temperature zone, with a main wavelength of 365 nm and an irradiation intensity of 800–1200 mW / cm². 2 The irradiation time is 5 to 10 seconds.

5. The method for preparing perovskite quantum dot composite thin films according to claim 4, characterized in that, In step S2, the temperature of the vacuum distillation is 45-55°C, the gauge pressure is 0.005-0.02 MPa, and the continuous vacuum distillation time is 1-2 hours.

6. The method for preparing perovskite quantum dot composite thin films according to claim 4, characterized in that, In step S4, the substrate is an optical-grade polyethylene terephthalate substrate that has undergone single-sided corona treatment, and the thickness of the wet film is controlled between 50 and 100 μm.

7. The method for preparing perovskite quantum dot composite thin films according to claim 4, characterized in that, Between step S2 and step S3, there is also a transitional cooling step: after the vacuum distillation is completed, the system temperature is reduced to 25-30°C at a cooling rate not exceeding 2°C / min and then restored to atmospheric pressure.

8. The method for preparing perovskite quantum dot composite thin films according to claim 4, characterized in that, In step S3, the degassing and mixing conditions are: temperature 25-30℃, gauge pressure -0.09MPa and below, rotation speed 150-250rpm, and degassing and mixing time 30-50 minutes.

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