Polymer dispersed liquid crystal (PDLC) dimming film with wide light response range and high light excitation efficiency as well as preparation method and application of PDLC dimming film

Abstract

The invention discloses a PDLC (Polymer Dispersed Liquid Crystal) dimming film with wide light response range and high light excitation efficiency, which comprises a first transparent conductive layer, a polymer liquid crystal composite material layer and a second transparent conductive layer which are sequentially stacked, and the polymer liquid crystal composite material layer comprises the following raw materials: a photopolymerizable monomer, a cross-linking agent, a liquid crystal, a photoinitiator and an AgVO3 nanowire; in the raw materials, the parts by weight of the photo-polymerizable monomer is 1-5 times of the parts by weight of the cross-linking agent; the weight part of the photoinitiator is 0.5-2% of the sum of the weight part of the photopolymerizable monomer, the weight part of the cross-linking agent and the weight part of the liquid crystal; and the weight part of the AgVO3 nanowire is 0.25-0.60% of the sum of the weight part of the photopolymerizable monomer, the weight part of the cross-linking agent and the weight part of the liquid crystal. According to the invention, the AgVO3 nanowire is creatively introduced into the PDLC light adjusting film and is cooperated with other components, so that the PDLC light adjusting film has a wide light response range and light excitation efficiency.

Description

Technical Field

[0001] The present invention belongs to the technical field of liquid crystal materials, and in particular relates to a PDLC dimming film with a wide light response range and high light excitation efficiency, as well as a preparation method and application thereof. Background Art

[0002] In today's society, environmentally friendly and intelligent materials are permeating every aspect of our daily lives. Smart windows can control radiation flux, reduce energy consumption, and protect privacy, giving them enormous potential for application in fields such as architectural design and automotive manufacturing. Among smart window devices, polymer-dispersed liquid crystal (PDLC) films have attracted considerable attention over the past 40 years due to their excellent tunability, simple processing, and commercial potential.

[0003] PDLC film usually has two transparent conductive layers as substrates, with a liquid crystal / polymer composite layer in the middle, forming a sandwich structure. When an electric field is applied to the PDLC film, the orientation of the liquid crystal molecules changes, and the refractive index changes. When the normal refractive index of the liquid crystal (n o ) and the refractive index of the polymer (n p ) matches, the PDLC film changes from a scattering state to a transparent state, and the transmittance of solar radiation through the PDLC film is adjusted by applying different voltages.

[0004] At present, the main process routes for preparing PDLC films include solvent-induced phase separation, heat-induced phase separation and polymerization-induced phase separation. Due to its superior droplet controllability, polymerization-induced phase separation (PIPS route) has become the most widely used PDLC film preparation process. The PIPS route is a reaction process that uses photothermal polymerization to induce phase separation of liquid crystal and polymer matrix. It usually includes raw material mixing, coating and curing to achieve uniform phase separation of liquid crystal droplets.

[0005] In the process of realizing the present invention, the inventors discovered that the existing technology has at least the following problems: the PIPS route involves processes such as photopolymerization and liquid crystal phase separation. In the industrial production of PDLC films, the light utilization efficiency in the photopolymerization stage is the core bottleneck restricting production efficiency. The traditional process relies on the ultraviolet photoinitiator Irgacure 651, whose absorption spectrum is limited to the ultraviolet bands of 250nm and 340nm. In actual production, the ultraviolet light source has high energy consumption (>500W / m 2 ), high equipment maintenance costs, and ultraviolet light only accounts for about 5% of natural light, resulting in photopolymerization efficiency being limited to a specific wavelength, low light excitation efficiency, film shrinkage and even cracking, and high requirements for lighting conditions and raw material selection. These are the main reasons restricting the industrial promotion of PDLC films. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to address the deficiencies of the above-mentioned prior art and provide a PDLC dimming film with a wide light response range and high light excitation efficiency, as well as a preparation method and application thereof.

[0007] Compared with the prior art, the present invention has the following advantages:

[0008] 1. The method for preparing the PDLC dimming film of the present invention can be cured under ultraviolet light and visible light to obtain a PDLC dimming film with high photoelectric performance, with a high polymerization reaction rate and monomer conversion rate, and can broaden the light response range of PDLC light polymerization, realizing accelerated polymerization under a wider range of lighting conditions to prepare the PDLC dimming film.

[0009] 2. The PDLC dimming film with a wide light response range and high light excitation efficiency of the present invention includes a polymer liquid crystal composite material layer prepared from a photopolymerizable monomer, a crosslinker, a liquid crystal, a photoinitiator and AgVO3 nanowires. AgVO3 nanowires are creatively introduced into the PDLC dimming film and cooperate with the other components to improve the light response range of the PDLC dimming film, accelerate polymerization and improve the light excitation efficiency.

[0010] 3. The raw materials in the method for preparing the PDLC dimming film of the present invention include acrylates with large groups at the end and acrylates with alkyl chains at the end. The composite monomers realize the construction of a gradient interpenetrating network under the action of AgVO3 nanowires and photoinitiators, which can not only inhibit the coarsening of liquid crystal droplets, but also improve the mechanical stability of the PDLC dimming film through stress dispersion, and efficiently obtain a PDLC dimming film with a lower driving voltage.

[0011] 4. The photopolymerizable monomers used in the PDLC dimming film prepared by the present invention are low in price and have low toxicity.

[0012] The technical solution of the present invention is further described in detail below with reference to the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 : is the electro-optical performance curve of the PDLC dimming films F1 and F0 of Example 1 at the test temperature;

[0014] Figure 2 This is a scanning electron microscope image of the PDLC dimming film F1 of Example 1;

[0015] Figure 3 2 is the electro-optical performance curve of the PDLC dimming films F2 and F3 of Example 2 at the test temperature;

[0016] Figure 4 This is a scanning electron microscope image of the PDLC dimming film F2 of Example 2;

[0017] Figure 5 : The electro-optical performance curves of the PDLC dimming films F4 and F5 of Example 3 at the test temperature;

[0018] Figure 6 This is a scanning electron microscope image of the PDLC dimming film F4 of Example 3;

[0019] Figure 7 : This is the electro-optical performance curve of the PDLC dimming films F8 and F9 of Example 5 at the test temperature;

[0020] Figure 8 This is a scanning electron microscope image of the PDLC dimming film F8 of Example 5;

[0021] Figure 9 : This is the electro-optical performance curve of the PDLC dimming film F10 of comparative example 2 at the test temperature;

[0022] Figure 10 This is a scanning electron microscope image of the PDLC dimming film F10 of comparative example 2. DETAILED DESCRIPTION

[0023] The following will be combined with the embodiments of this application to clearly and completely describe the technical solution. Obviously, the embodiments described are part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0024] In the following description, the term "and / or" is used to describe the association relationship between associated objects, indicating that three relationships can exist. For example, A and / or B can represent: A exists alone, B exists alone, and A and B exist at the same time. A and B can be singular or plural.

[0025] In the following description, the terms "include", "comprising", "having" and "containing" are open-ended terms, meaning including but not limited to.

[0026] Those skilled in the art should understand that in the following description of the embodiments of the present application, the order of serial numbers does not mean the order of execution, some or all of the steps can be executed in parallel or sequentially, and the execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0027] It will be understood by those skilled in the art that the numerical ranges in the examples of the present application are to be understood as also specifically disclosing each intermediate value between the upper and lower limits of the ranges. Each smaller range between any intermediate value within a stated value or stated range and any other stated value or intermediate value within the stated range is also included in the present application. The upper and lower limits of these smaller ranges may independently be included or excluded in the range.

[0028] Unless otherwise indicated, the technical / scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which this application belongs. Although this application describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of this application. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In the event of any conflict with any incorporated document, the content of this specification shall prevail.

[0029] The technical principle adopted by this invention is: In the industrial production of PDLC films, the light utilization efficiency in the photopolymerization stage is the core bottleneck restricting production efficiency. The traditional process relies on the ultraviolet photoinitiator Irgacure 651, whose absorption spectrum is limited to the ultraviolet band of 250nm and 340nm. However, in actual production, the ultraviolet light source has high energy consumption (>500W / m 2 ), high equipment maintenance costs, and other issues. Furthermore, ultraviolet light only accounts for about 5% of natural light, resulting in photopolymerization efficiency being limited to specific wavelengths. By introducing silver metavanadate (AgVO3) nanowires and combining them with a light absorber, the V 3d-O 2p-Ag 4d hybrid valence band of AgVO3 forms a narrow bandgap structure of 1.9-2.2eV. The light absorption boundary can be extended to the 550nm visible light region, forming continuous coverage with the ultraviolet absorption band of the light absorber. Utilizing the spectral complementarity of the two, a wide spectral response system can be constructed to adapt to low-cost light sources such as LED arrays or natural light.

[0030] On the one hand, a PDLC dimming film with a wide light response range and high light excitation efficiency is provided, comprising a first transparent conductive layer, a polymer liquid crystal composite material layer, and a second transparent conductive layer stacked in sequence, wherein the raw materials of the polymer liquid crystal composite material layer include a photopolymerizable monomer, a crosslinker, a liquid crystal, a photoinitiator, and AgVO3 nanowires;

[0031] In the raw materials, the weight of the liquid crystal is 1.5 to 4 times the sum of the weight of the photopolymerizable monomer and the crosslinking agent; the weight of the photopolymerizable monomer is 1 to 5 times the weight of the crosslinking agent;

[0032] The weight of the photoinitiator is 0.5-2% of the total weight of the photopolymerizable monomer, the crosslinking agent and the liquid crystal; the weight of the AgVO3 nanowire is 0.25-0.60% of the total weight of the photopolymerizable monomer, the crosslinking agent and the liquid crystal.

[0033] The present invention creatively introduces AgVO3 nanowires into the preparation process of PDLC dimming film. Based on the performance characteristics of AgVO3 nanowires, such as narrow band gap, high light absorption ability and high mobility, a dimming film with a wide light response range and significantly improved photoelectric performance is provided.

[0034] Especially when the weight of the photoinitiator is 0.5-2% of the sum of the weight of the photopolymerizable monomer, the weight of the cross-linker and the weight of the liquid crystal, the applicable light absorption range of the photoinitiator and the AgVO3 nanowire can be fully combined to achieve light absorption in a wider spectrum from ultraviolet light to visible light, breaking the limitations of the traditional photoinitiator absorption spectrum concentrated in the 250nm and 340nm ultraviolet light regions and the limited degree and efficiency of the photochemical reactions stimulated by them, and expanding the absorption wavelength region to ultraviolet light and visible light with a wavelength range of less than 550nm, so as to achieve the preparation of PDLC dimming film in a wider lighting environment.

[0035] In some embodiments, the weight of the photoinitiator is 1.5 to 4 times the weight of the AgVO3 nanowires.

[0036] During the experiment, it was found that the combination of photoinitiator and AgVO3 nanowires, especially when the weight of the photoinitiator is 1.5 to 4 times the weight of the AgVO3 nanowires, can fully exert the synergistic effect of the two. Through the polymerization reaction of the unsaturated prepolymer system initiated by free radicals under ultraviolet excitation, and the interaction between electron-hole pairs generated under visible light excitation to generate active substances such as hydroxyl radicals, the monomer molecules are synergistically promoted to participate in polymerization, maintain chain growth, and accelerate the free radical chain growth reaction.

[0037] During the research process, it was also found that in addition to combining with light absorbers to broaden the light response range, the electrons (e - , -0.34eV vs NHE) is transferred to the LUMO orbital (-1.2eV) of Irgacure651 through the interface, accelerating the generation efficiency of benzoyloxy radicals. At the same time, the hole (h + , +2.56eV) oxidizes acrylate to cationic radicals, opening up a new polymerization pathway. When the mass ratio of AgVO3 and Irgacure 651 is 1:2, the absorbance of the composite photocatalytic system in the range of 250-550nm increases by 2.3 times, and the UV intensity requirement is increased from 80mW / cm 2 Down to 35mW / cm 2, significantly reducing the energy consumption of the equipment. At the same time, based on the above-mentioned dual-channel free radical generation mechanism, the initial polymerization efficiency is improved, the time required for the monomer conversion rate to reach 95% is shortened from 25 minutes to 8 minutes, the molecular weight distribution coefficient PDI is optimized from 1.7 to 1.25, and the polymer is uniformly polymerized.

[0038] Secondly, it can also achieve light-heat-electric multi-field coupling regulation. The surface plasmon resonance effect of AgVO3 nanowires can convert 15% of the incident light into local thermal energy, promote the movement of polymer chains and accelerate phase separation. In addition, the carrier mobility of AgVO3 reaches 1.2×10 -3 cm 2 / V·s, which can make the polymer matrix have charge dissipation ability, reduce the surface resistivity by 3 orders of magnitude, and effectively suppress the electrostatic adsorption pollution problem in outdoor applications.

[0039] In some embodiments, the photopolymerizable monomer includes an acrylate with a bulky group at the end and an acrylate with an alkyl chain at the end; and / or, the acrylate with a bulky group at the end includes one or more of cyclohexyl methacrylate, isobornyl acrylate, 2-phenylethyl acrylate, 3,4-epoxycyclohexyl methacrylate, tetrahydrofuran acrylate, dicyclopentanyl acrylate, phenyl acrylate, cyclohexyl acrylate and glycidyl acrylate; and / or, the acrylate with an alkyl chain at the end includes one or more of lauryl methacrylate, butyl acrylate, 3,5,5-trimethylhexyl acrylate, 2-ethylhexyl acrylate, hexyl acrylate, butyl acrylate and ethoxyethoxyethyl acrylate.

[0040] Furthermore, when the photopolymerizable monomer is a compound of two monomers containing specific groups, namely, an acrylate with a large end group and an acrylate with an alkyl end group, the acrylate with a large end group can delay chain termination, stabilize free radical intermediates, and react with VO3 on the surface of AgVO3. - The groups preferentially adsorb through hydrogen bonding, inducing the formation of a highly cross-linked network at the nanowire interface. The alkyl-terminated acrylates reduce the viscosity of the system and promote the oxidation of monomers by photogenerated holes to form cationic free radicals, providing a new polymerization pathway. The polymerization behavior of the composite monomers synergizes with the AgVO3 nanowires and photoinitiator at multiple levels, increasing the polymerization rate.

[0041] Under the action of AgVO3 nanowires and photoinitiators, the composite monomer can not only enhance the polarization of photoinitiator molecules by utilizing the localized surface plasmon effect, but also promote the diffusion of free radicals by utilizing its carrier migration ability, so that the acrylate with large groups at the end constructs branched cross-linking points on the surface, and the acrylate with alkyl chains at the end forms an extended network in the main area, thus constructing a gradient interpenetrating network structure.

[0042] In some implementations, the weight ratio of the acrylate with a bulky terminal group to the acrylate with an alkyl terminal chain is (1-3):1.

[0043] In some implementations, the crosslinking agent is a bifunctional acrylate, including one or more of triethylene glycol diacrylate, neopentyl glycol diacrylate, dipropylene glycol diacrylate, polyethylene glycol diacrylate, 1,6-hexanediol diacrylate, 1,4-butylene glycol diacrylate, 1,10-decanediol diacrylate, bisphenol A glycerol dimethacrylate, tetraethylene glycol diacrylate and tripropylene glycol diacrylate.

[0044] In some implementations, the photoinitiator is one or more of benzoin ethyl ether, 2-hydroxy-2-methyl-1-phenylpropanone, trimethylbenzoyldiphenylphosphine oxide, and benzoin diethyl ether.

[0045] On the other hand, a method for preparing a PDLC dimming film with a wide light response range and high light excitation efficiency is provided, comprising:

[0046] S1. The photopolymerizable monomer, crosslinker, liquid crystal, photoinitiator and AgVO3 nanowires were mixed and then poured between the first transparent conductive layer and the second transparent conductive layer to obtain sample A;

[0047] S2. Under ultraviolet light and / or visible light, photocuring the sample A to obtain a PDLC dimming film.

[0048] In some implementations, in step S1 , both the first transparent conductive layer and the second transparent conductive layer are conductive glass coated with indium tin oxide; and the distance between the first transparent conductive layer and the second transparent conductive layer is 19-21 μm.

[0049] In some implementations, in step S2, the curing temperature is 0-10°C higher than the temperature at which the mixed system is isotropic, the curing time is ≤500s, and the light intensity is 5-10mW / cm 2 In some specific embodiments, the temperature at which the mixed system is isotropic is room temperature.

[0050] The present invention also provides a method for preparing the PDLC dimming film with a wide light response range and high light excitation efficiency, which is prepared by mixing the raw materials uniformly and pouring them between a liquid crystal cell composed of two conductive layers, and then photocuring the mixture, in particular, the photocuring temperature is 0 to 10°C higher than the temperature of the isotropic mixed system, the curing time is ≤500s, and the light intensity is 5 to 10mW / cm 2Under these conditions, the liquid crystal molecules can be kept in a disordered state at the initial stage of photopolymerization, reducing the hindrance to monomer diffusion, and the curing time is ≤500s. In some specific embodiments, the curing time is 400-500s, and the light intensity is 5-10mW / cm 2 Curing under this light intensity and lighting conditions can not only avoid local heat accumulation caused by excessive light intensity, but also cooperate with the wide-spectrum response AgVO3 to further promote the full conversion of residual monomers, showing a high photopolymerization reaction rate with a conversion rate of up to 98%.

[0051] On the one hand, an application of the above-mentioned PDLC dimming film with a wide light response range and high light excitation efficiency is also provided, including applications in wearable devices, interactive interfaces or artistic decoration, such as as a protective film for automobile glass, which can achieve dimming while effectively avoiding electrostatic adsorption in outdoor applications.

[0052] The present invention has been subjected to a series of experiments before the application is filed. Some of the experimental results are listed below to further describe the invention in detail, and the following embodiments are used to describe the invention in detail.

[0053] In the present invention, the percentages mentioned are all mass percentages, and the meanings of the symbols are as follows:

[0054] T off Indicates the light transmittance of PDLC when no electric field is applied (off-state transmittance); T on Indicates the light transmittance (on-state transmittance) of PDLC when an electric field of 100V is applied; V sat Indicates the saturation voltage, which refers to the voltage when the PDLC light transmittance reaches T on The voltage required to achieve 90% of the required value; CR represents contrast ratio, which is calculated as follows: CR = T on / T off .

[0055] Example 1

[0056] This embodiment provides a PDLC dimming film with a wide light response range and high light excitation efficiency, including a first transparent conductive layer, a polymer liquid crystal composite material layer and a second transparent conductive layer stacked in sequence, wherein the raw materials of the polymer liquid crystal composite material layer include a photopolymerizable monomer, a cross-linking agent, a liquid crystal, a photoinitiator and AgVO3 nanowires.

[0057] This embodiment also provides a method for preparing a PDLC dimming film with a wide light response range and high light excitation efficiency, comprising the following steps performed in sequence:

[0058] S1. Photopolymerizable monomers cyclohexyl methacrylate (CHMA), lauryl methacrylate (LMA), butyl acrylate (BA), crosslinker 1,4-butylene glycol diacrylate (BDDA), liquid crystal E8, ultraviolet light initiator Irg651, and AgVO3 nanowires were sampled and mixed according to Table 1, and stirred thoroughly to obtain a mixed system. The mixed system was poured between two pieces of conductive glass coated with indium tin oxide, and the distance between the two pieces of conductive glass coated with indium tin oxide was 20.0 μm to obtain a liquid crystal layer. The conductive glass coated with indium tin oxide was purchased from Qingdao Taiweida Company, with dimensions of 75*25*1.1 mm and a resistance of 10 ohm / sq. The liquid crystal E8 was an industrial product with a purity of ≥99.0%, a normal light refractive index and an extraordinary light refractive index n. o =1.527 and n e =1.774, purchased from Jiangsu Hecheng Display Co., Ltd.; the temperature when the mixed system is isotropic is room temperature;

[0059] S2. Place the liquid crystal layer in S1 at 30°C and a UV light intensity of 10 mW / cm 2 After curing for 500s under the same conditions, a PDLC dimming film F1 with a wide light response range and high light excitation efficiency was obtained;

[0060] Sample F0 is a control sample without adding AgVO3 nanowires. The composition ratio is shown in Table 1. The preparation method is the same as that of sample F1.

[0061] Table 1 Composition of samples in Example 1

[0062]

[0063] The electro-optical performance curves of the PDLC dimming films F1 and F0 prepared above were measured by a liquid crystal comprehensive parameter tester at test temperature. The test temperature was room temperature. The results are as follows: Figure 1 The electro-optical performance data are given in Table 2.

[0064] Table 2 Main electro-optical properties of PDLC dimming films F1 and F0

[0065] Sample number <![CDATA[V sat (V)]]> CR <![CDATA[T on (%)]]> <![CDATA[T off (%)]]> F0 24.3 179 64.639 0.361 F1 20.4 188 78.496 0.417

[0066] Combine Figure 1 As shown in Table 2, both PDLC switchable films F0 and F1 exhibit traditional voltage-transmittance (VT) curves. Furthermore, with the addition of AgVO3, sample F1 achieves a saturation voltage of approximately 20V, a contrast ratio exceeding 185, and increases in both on- and off-state transmittance. Compared to PDLC switchable film F0, which lacks AgVO3 nanowires, the PDLC switchable film of Example 1 exhibits significantly lower saturation voltage and higher contrast.

[0067] The polymer network of PDLC dimming film F1 was observed by scanning electron microscopy (SEM). Figure 2 shown by Figure 2 The average pore size of the F1 polymer mesh is 1-2 μm, and the sample surface is smooth and neat, consistent with its high contrast. This demonstrates that the addition of AgVO3 nanowires effectively increases the polymerization rate of the photopolymerizable monomers, restricts the diffusion of liquid crystals, and thus forms a good phase separation.

[0068] Example 2

[0069] This embodiment provides a PDLC dimming film with a wide light response range and high light excitation efficiency, including a first transparent conductive layer, a polymer liquid crystal composite material layer and a second transparent conductive layer stacked in sequence, wherein the raw materials of the polymer liquid crystal composite material layer include a photopolymerizable monomer, a cross-linking agent, a liquid crystal, a photoinitiator and AgVO3 nanowires.

[0070] This embodiment also provides a method for preparing a PDLC dimming film with a wide light response range and high light excitation efficiency, comprising the following steps performed in sequence:

[0071] S1. Photopolymerizable monomers cyclohexyl methacrylate (CHMA), lauryl methacrylate (LMA), butyl acrylate (BA), crosslinker 1,6-hexanediol diacrylate (HDDA), liquid crystal E8, ultraviolet light initiator Irg651, and AgVO3 nanowires were sampled and mixed according to Table 3, and stirred thoroughly to obtain a mixed system. The mixed system was poured between two pieces of conductive glass coated with indium tin oxide, and the distance between the two pieces of conductive glass coated with indium tin oxide was 20.0 μm to obtain a liquid crystal layer. The conductive glass coated with indium tin oxide was purchased from Qingdao Taiweida Company, with dimensions of 75*25*1.1 mm and a resistance of 10 ohm / sq. The liquid crystal E8 was an industrial product with a purity of ≥99.0%, and a refractive index of ordinary light and an extraordinary light, n. o =1.527 and n e =1.774, purchased from Jiangsu Hecheng Display Co., Ltd.; the temperature when the mixed system is isotropic is room temperature;

[0072] S2. Place the liquid crystal layer in S1 at 30°C and a UV light intensity of 10 mW / cm 2 After curing for 500s under the same conditions, a PDLC dimming film F2 with a wide light response range and high light excitation efficiency was obtained;

[0073] Sample F3 is a control sample without adding AgVO3 nanowires. The composition ratio is shown in Table 3. The preparation method is the same as that of sample F2.

[0074] Table 3 Composition of samples in Example 2

[0075]

[0076]

[0077] The electro-optical performance curves of the PDLC dimming films F2 and F3 prepared above were measured by a liquid crystal comprehensive parameter tester at test temperature. The test temperature was room temperature. The results are as follows: Figure 3 The electro-optical performance data are given in Table 4.

[0078] Table 4 Main electro-optical properties of PDLC dimming films F2 and F3

[0079] Sample number <![CDATA[V sat (V)]]> CR <![CDATA[T on (%)]]> <![CDATA[T off (%)]]> F2 22.6 187 78.029 0.417 F3 23.7 181 64.804 0.358

[0080] Combine Figure 3 As shown in Table 4, the PDLC dimming films F2 and F3 exhibited traditional voltage-transmittance (VT) curves. At the same time, under the action of AgVO3, the saturation voltage of the F2 sample decreased, the contrast increased, and both the on-state transmittance and the off-state transmittance increased.

[0081] The polymer network of PDLC dimming film F2 was observed by scanning electron microscopy (SEM). Figure 4 shown by Figure 4 The average pore size of the F2 polymer mesh is 1-2 μm, which is consistent with its high contrast. This demonstrates that the addition of AgVO3 nanowires effectively increases the polymerization rate of the photopolymerizable monomers, restricts the diffusion of liquid crystals, and thus forms a good phase separation.

[0082] Comparative Example 1

[0083] This comparative example examines the effect of a crosslinking agent on the performance of a PDLC dimming film. The preparation method is the same as that of Example 1, except that the crosslinking agent is polyethylene glycol diacrylate (PEGDA400) with a molecular weight of 400. The resulting PDLC dimming film is labeled F4.

[0084] Sample F5 is a control sample without adding AgVO3 nanowires. The composition ratio is shown in Table 5. The preparation method is the same as that of sample F4.

[0085] Table 5 Composition of samples in Comparative Example 1

[0086]

[0087] The electro-optical performance curves of the PDLC dimming films F4 and F5 prepared above were measured by a liquid crystal comprehensive parameter tester at test temperature. The test temperature was room temperature. The results are as follows: Figure 5 The electro-optical performance data are given in Table 6.

[0088] Table 6 Main electro-optical properties of PDLC dimming films F4 and F5

[0089] Sample number <![CDATA[V sat (V)]]> CR <![CDATA[T on (%)]]> <![CDATA[T off (%)]]> F4 61.2 185 77.825 0.421 F5 87.1 183 77.904 0.426

[0090] Combine Figure 5 As shown in Table 6, PDLC switchable films F4 and F5 exhibit traditional voltage-transmittance (VT) curves. Compared to PDLC switchable film F5 without AgVO3 nanowires, PDLC switchable film F4, which incorporates AgVO3 nanowires, exhibits a lower saturation voltage and improved contrast. However, the saturation voltage of PDLC switchable film F4 is 61.2V, nearly 40V higher than the saturation voltage of 22.6V of PDLC switchable film F1 in Example 1, while the contrast ratio remains similar.

[0091] The polymer network of PDLC dimming film F4 was observed by scanning electron microscopy (SEM). Figure 6 shown by Figure 6 It can be seen that the polymer mesh of F4 is small and the pore structure collapses severely. The preliminary research results of the present invention show that when acrylates with large groups at the end and acrylates with alkyl chains at the end are used as UV-polymerizable monomers, the physical and chemical properties of the prepared PDLC dimming film are related to the cross-linker, which is manifested as the longer the cross-linker chain length or the larger the molecular weight, the larger the mesh of the PDLC dimming film polymer. The reason is that the longer the cross-linker chain length or the larger the molecular weight, the slower the polymerization rate of the polymer system, and the longer the aggregation time of the liquid crystal droplets, resulting in an increase in the polymer mesh and a serious loss of sample contrast. The present invention has found that under the conditions of long-chain cross-linkers, the addition of AgVO3 nanowires can inhibit the expansion of the polymer mesh and avoid a serious decrease in contrast.

[0092] Example 3

[0093] This embodiment provides a PDLC dimming film with a wide light response range and high light excitation efficiency, including a first transparent conductive layer, a polymer liquid crystal composite material layer and a second transparent conductive layer stacked in sequence, wherein the raw materials of the polymer liquid crystal composite material layer include a photopolymerizable monomer, a cross-linking agent, a liquid crystal, a photoinitiator and AgVO3 nanowires.

[0094] This embodiment also provides a method for preparing a PDLC dimming film with a wide light response range and high light excitation efficiency, comprising the following steps performed in sequence:

[0095] S1. Photopolymerizable monomers cyclohexyl methacrylate (CHMA), lauryl methacrylate (LMA), ethyl acrylate (HA), crosslinker 1,4-butylene glycol diacrylate (BDDA), liquid crystal E8, ultraviolet light initiator Irg651, and AgVO3 nanowires were sampled and mixed according to Table 7, and stirred thoroughly to obtain a mixed system. The mixed system was poured between two pieces of conductive glass coated with indium tin oxide, with a distance of 20.0 μm between the two pieces of conductive glass coated with indium tin oxide, to obtain a liquid crystal layer. The conductive glass coated with indium tin oxide was purchased from Qingdao Taiweida Company, with a size of 75*25*1.1 mm and a resistance of 10 ohm / sq. The liquid crystal E8 was an industrial product with a purity of ≥99.0%, a normal light refractive index and an extraordinary light refractive index n. o =1.527 and n e =1.774, purchased from Jiangsu Hecheng Display Co., Ltd.; the temperature when the mixed system is isotropic is room temperature;

[0096] S2. Place the liquid crystal layer in S1 at 30°C and a UV light intensity of 5 mW / cm 2 , white LED light intensity is 10mW / cm 2 The film was cured for 400 seconds under the above conditions to obtain a PDLC dimming film with a wide light response range and high light excitation efficiency, which was marked as F6. The main peak of the white light LED was 450 nm.

[0097] Example 4

[0098] This example examines the effect of light curing conditions on the performance of PDLC dimming film. The method for preparing the PDLC dimming film is the same as that in Example 3. The difference is that in S2, the liquid crystal layer in S1 is heated at 30°C and the UV intensity is 5mW / cm 2 The film was cured for 400 s under the above conditions to obtain a PDLC dimming film, which was marked as F7.

[0099] The compositions of the PDLC dimming film samples of Example 3 and Example 4 are shown in Table 7, and their main photoelectric properties are shown in Table 8.

[0100] Table 7 Composition of samples in Example 3 and Example 4

[0101]

[0102] Table 8 Main electro-optical properties of samples in Example 3 and Example 4

[0103]

[0104] In Table 8, the final monomer conversion rate is calculated as follows: samples of the liquid crystal layer before curing and the PDLC dimming film after curing are respectively analyzed by infrared spectroscopy, the absorption peak area of ​​the C=C double bond, the characteristic functional group of the acrylate of the sample, is integrated, the peak area decay after curing is determined, and the final monomer conversion rate is calculated using the following formula: Final monomer conversion rate % = (1-A t / A0)*100; where A0 and A t are the peak areas of the C=C characteristic peak at the initial time and time t, respectively.

[0105] As shown in Table 8, at a curing time of 400 seconds, the final monomer conversion rate of PDLC dimming film F6 was 93.7%, and that of F7 was 84.2%. The polymerization conversion rate under visible light + UV light initiation conditions increased by approximately 10% compared to the polymerization conversion rate under UV light alone. The method of the present invention exhibits visible light response and can polymerize over a wide range of illumination conditions, enabling accelerated polymerization to produce PDLC dimming films under a wider range of illumination conditions. Furthermore, compared to PDLC dimming film F7, PDLC dimming film F6 exhibited a slight increase in contrast and a slight decrease in saturation voltage, demonstrating that the method of the present invention can achieve a slight improvement in the optoelectronic performance of PDLC dimming films while overcoming the photoresponse limitations of current PDLC dimming film preparation processes.

[0106] Example 5

[0107] This embodiment provides a PDLC dimming film with a wide light response range and high light excitation efficiency, including a first transparent conductive layer, a polymer liquid crystal composite material layer and a second transparent conductive layer stacked in sequence, wherein the raw materials of the polymer liquid crystal composite material layer include a photopolymerizable monomer, a cross-linking agent, a liquid crystal, a photoinitiator and AgVO3 nanowires.

[0108] This embodiment also provides a method for preparing a PDLC dimming film with a wide light response range and high light excitation efficiency, comprising the following steps performed in sequence:

[0109] S1. Photopolymerizable monomers phenyl acrylate (PA), 2-ethylhexyl acrylate (EHA), butyl acrylate (BA), crosslinker 1,4-butylene glycol diacrylate (BDDA), liquid crystal E8, ultraviolet light initiator Irg651, and AgVO3 nanowires were sampled and mixed according to Table 9, and stirred thoroughly to obtain a mixed system. The mixed system was poured between two pieces of conductive glass coated with indium tin oxide, with a distance of 20.0 μm between the two pieces of conductive glass coated with indium tin oxide, to obtain a liquid crystal layer. The conductive glass coated with indium tin oxide was purchased from Qingdao Taiweida Company, with dimensions of 75*25*1.1 mm and a resistance of 10 ohm / sq. The liquid crystal E8 was an industrial product with a purity of ≥99.0%, a normal light refractive index and an extraordinary light refractive index n. o =1.527 and ne =1.774, purchased from Jiangsu Hecheng Display Co., Ltd.; the temperature when the mixed system is isotropic is room temperature;

[0110] S2. Place the liquid crystal layer in S1 at 30°C and a UV light intensity of 10 mW / cm 2 After curing for 500s under the same conditions, the PDLC dimming film F8 with a wide light response range and high light excitation efficiency was obtained;

[0111] Sample F9 is a control sample without adding AgVO3 nanowires. The composition ratio is shown in Table 9. The preparation method is the same as that of sample F8.

[0112] Table 9 Composition of samples in Example 5

[0113]

[0114]

[0115] The electro-optical performance curves of the PDLC dimming films F8 and F9 prepared above were measured by a liquid crystal comprehensive parameter tester at test temperature. The test temperature was room temperature. The results are as follows: Figure 7 The electro-optical performance data are given in Table 10.

[0116] Table 10 Main electro-optical properties of PDLC dimming films F8 and F9

[0117] Sample number <![CDATA[V sat (V)]]> CR <![CDATA[T on (%)]]> <![CDATA[T off (%)]]> F8 20.2 189 77.825 0.412 F9 23.7 181 64.804 0.358

[0118] Combine Figure 7 As shown in Table 10, both PDLC dimming films F8 and F9 exhibited traditional voltage-transmittance (VT) curves. At the same time, under the action of AgVO3, the saturation voltage of the F8 sample decreased, the contrast increased, and both the on-state transmittance and the off-state transmittance increased.

[0119] The polymer network of PDLC dimming film F8 was observed by scanning electron microscopy (SEM). Figure 8 shown by Figure 8 It can be seen that the average size of the polymer mesh of F8 is 1-2μm, with a tendency to increase slightly. The surface of the sample is smooth and neat, showing a high contrast, which proves that the addition of AgVO3 nanowires effectively promotes the formation of good phase separation.

[0120] Comparative Example 2

[0121] This example examines the effect of the addition amount of AgVO3 nanowires on the performance of the PDLC dimming film. The preparation method is the same as that of Example 1, except that the total weight of the AgVO3 nanowires, monomers, crosslinkers, and liquid crystals is 0.1 wt.%, marked as F10, and the composition comparison with the F1 sample in Example 1 is shown in Table 11. The main optoelectronic properties are shown in Table 12.

[0122] Table 11 Comparative composition of the PDLC dimming film F10 of comparative example 2 and the PDLC dimming film F1 of example 1

[0123]

[0124]

[0125] The electro-optical performance curve of the PDLC dimming film F10 at the test temperature was measured using a liquid crystal comprehensive parameter tester. Figure 9 shown.

[0126] Table 12 Comparison of main photoelectric properties of PDLC dimming film F10 of comparative example 2 and PDLC dimming film F1 of example 1

[0127] Sample number <![CDATA[V sat (V)]]> CR <![CDATA[T on (%)]]> <![CDATA[T off (%)]]> F1 20.4 188 78.496 0.417 F10 22.6 169 76.028 0.450

[0128] Combine Figure 9 As shown in Table 12, the PDLC dimming film F10 in this comparative example exhibits a traditional voltage-transmittance (VT) curve that is essentially identical to that of F1. Furthermore, the saturation voltage of F10 increases compared to F1, and the contrast ratio decreases significantly. This indicates that when the AgVO3 nanowire dosage is too low—that is, when the ratio of AgVO3 nanowires to the sum of the weight of the photopolymerizable monomer, crosslinker, and liquid crystal is less than 0.25%—it is detrimental to improving the optoelectronic performance of the PDLC dimming film. Figure 10 This is a scanning electron microscope image of the PDLC dimming film F10. It can be seen that the polymer network mesh has collapsed severely.

Claims

1. A PDLC dimming film with a wide light response range and high light excitation efficiency, characterized in that: The invention comprises a first transparent conductive layer, a polymer liquid crystal composite material layer and a second transparent conductive layer stacked in sequence, wherein the raw materials of the polymer liquid crystal composite material layer include a photopolymerizable monomer, a crosslinking agent, a liquid crystal, a photoinitiator and AgVO3 nanowires; In the raw materials, the weight of the liquid crystal is 1.5 to 4 times the sum of the weight of the photopolymerizable monomer and the crosslinking agent; the weight of the photopolymerizable monomer is 1 to 5 times the weight of the crosslinking agent; The weight of the photoinitiator is 0.5-2% of the total weight of the photopolymerizable monomer, the crosslinking agent and the liquid crystal; the weight of the AgVO3 nanowire is 0.25-0.60% of the total weight of the photopolymerizable monomer, the crosslinking agent and the liquid crystal.

2. The PDLC dimming film with a wide light response range and high light excitation efficiency according to claim 1, characterized in that: The weight of the photoinitiator is 1.5 to 4 times that of the AgVO3 nanowires.

3. The PDLC dimming film with a wide light response range and high light excitation efficiency according to claim 1, characterized in that: The photopolymerizable monomers include acrylates with a bulky group at the end and acrylates with an alkyl chain at the end.

4. The PDLC dimming film with a wide light response range and high light excitation efficiency according to claim 3, characterized in that: The acrylate with a large group at the end includes one or more of cyclohexyl methacrylate, isobornyl acrylate, 2-phenylethyl acrylate, 3,4-epoxycyclohexyl methacrylate, tetrahydrofuran acrylate, dicyclopentanyl acrylate, phenyl acrylate, cyclohexyl acrylate and glycidyl acrylate; and / or, the acrylate with an alkyl chain at the end includes one or more of lauryl methacrylate, butyl acrylate, 3,5,5-trimethylhexyl acrylate, 2-ethylhexyl acrylate, hexyl acrylate, butyl acrylate and ethoxyethoxyethyl acrylate.

5. The PDLC dimming film with a wide light response range and high light excitation efficiency according to claim 3, characterized in that: The weight ratio of the acrylate with a large group at the end to the acrylate with an alkyl chain at the end is (1-3):

1.

6. The PDLC dimming film with a wide light response range and high light excitation efficiency according to claim 1, characterized in that: The crosslinking agent is a bifunctional acrylate, including one or more of triethylene glycol diacrylate, neopentyl glycol diacrylate, dipropylene glycol diacrylate, polyethylene glycol diacrylate, 1,6-hexanediol diacrylate, 1,4-butylene glycol diacrylate, 1,10-decanediol diacrylate, bisphenol A glycerol dimethacrylate, tetraethylene glycol diacrylate and tripropylene glycol diacrylate.

7. The PDLC dimming film with a wide light response range and high light excitation efficiency according to claim 1, characterized in that: The photoinitiator is one or more of benzoin ethyl ether, 2-hydroxy-2-methyl-1-phenylacetone, trimethylbenzoyldiphenylphosphine oxide and benzoin diethyl ether.

8. A method for preparing the PDLC dimming film with a wide light response range and high light excitation efficiency as claimed in claim 1, characterized in that: include: S1. The photopolymerizable monomer, crosslinker, liquid crystal, photoinitiator and AgVO3 nanowires were mixed and then poured between the first transparent conductive layer and the second transparent conductive layer to obtain sample A; S2. Under ultraviolet light and / or visible light, photocuring the sample A to obtain a PDLC dimming film.

9. The method according to claim 8, characterized in that In step S1, the first transparent conductive layer and the second transparent conductive layer are both conductive glass coated with indium tin oxide; and / or, in step S2, the curing time is ≤ 500s, and the light intensity is 5-10mW / cm 2 .

10. An application of the PDLC dimming film with a wide light response range and high light excitation efficiency as claimed in claim 1.

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