Wide optical response range, high photoexcitation efficiency PDLC dimming film, its preparation method and application

Abstract

This invention discloses a PDLC dimming film with a wide light response range and high photoexcitation efficiency, comprising a first transparent conductive layer, a polymer-liquid crystal composite material layer, and a second transparent conductive layer stacked sequentially. The polymer-liquid crystal composite material layer comprises photopolymerizable monomers, crosslinking agents, liquid crystals, photoinitiators, and AgVO3 nanowires. In the raw materials, the weight percentage of the photopolymerizable monomers is 1 to 5 times that of the crosslinking agent; the weight percentage of the photoinitiator is 0.5 to 2% of the sum of the weight percentages of the photopolymerizable monomers, crosslinking agents, and liquid crystals; and the weight percentage of the AgVO3 nanowires is 0.25 to 0.60% of the sum of the weight percentages of the photopolymerizable monomers, crosslinking agents, and liquid crystals. This invention creatively introduces AgVO3 nanowires into the PDLC dimming film, which, in synergy with the other components, exhibits a wide light response range and high photoexcitation efficiency.

Description

Technical Field

[0001] This invention belongs to the field of liquid crystal material technology, specifically relating to a wide light response range and high light excitation efficiency PDLC dimming film, its preparation method, and its application. Background Technology

[0002] In today's society, environmentally friendly and intelligent materials are permeating every aspect of our daily lives. Smart windows can control radiant flux, reduce energy consumption, and protect privacy, making them a promising candidate for applications in fields such as architectural design and automotive manufacturing. Among smart window devices, polymer-dispersed liquid crystal (PDLC) films have been favored by researchers over the past 40 years due to their excellent moduliability, ease of processing, and commercialization potential.

[0003] PDLC films typically consist of two transparent conductive layers as substrates, with a liquid crystal / polymer composite layer in between, 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 ordinary refractive index (n) of the liquid crystal changes... o ) and the refractive index (n) of the polymer p When matched, the PDLC film transitions from a scattering state to a transparent state. By applying different voltages, the transmittance of solar radiation through the PDLC film can be adjusted.

[0004] Currently, the main process routes for preparing PDLC films include solvent-induced phase separation, thermally induced phase separation, and polymerization-induced phase separation. Due to its superior microdroplet 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 initiates a polymerization reaction through photothermal initiation, causing phase separation between the liquid crystal and the polymer matrix. It typically includes raw material mixing, coating, and curing to achieve uniform phase separation of liquid crystal microdroplets.

[0005] In the process of realizing this invention, the inventors discovered at least the following problems in the prior art: The PIPS route involves processes such as photopolymerization and phase separation of the liquid crystal phase. In the industrial production of PDLC thin films, the light utilization efficiency of the photopolymerization stage is the core bottleneck restricting production efficiency. Traditional processes rely on the ultraviolet photoinitiator Irgacure 651, whose absorption spectrum is limited to the ultraviolet bands of 250nm and 340nm. However, in actual production, ultraviolet light sources have high energy consumption (>500W / m). 2 Problems such as high equipment maintenance costs, and the fact that ultraviolet light accounts for only about 5% of natural light, which limits the photopolymerization efficiency to a specific wavelength, resulting in low photoexcitation efficiency, film shrinkage or even cracking, and high requirements for lighting conditions and raw material selection, 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 provide a PDLC dimming film with a wide light response range and high photoexcitation efficiency, as well as its preparation method and application, in order to address the shortcomings of the prior art.

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

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

[0009] 2. The wide light response range and high photoexcitation efficiency PDLC dimming film of the present invention includes a polymer liquid crystal composite material layer prepared from photopolymerizable monomers, crosslinking agents, liquid crystals, photoinitiators and AgVO3 nanowires. It creatively introduces AgVO3 nanowires into the PDLC dimming film, which work synergistically with the other components to improve the light response range of the PDLC dimming film, accelerate polymerization and improve photoexcitation efficiency.

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

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

[0012] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0013] Figure 1 The electro-optic performance curves of PDLC dimming films F1 and F0 in Example 1 at the test temperature are shown.

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

[0015] Figure 3 The electro-optic performance curves of PDLC dimming films F2 and F3 in Example 2 at the test temperature are shown.

[0016] Figure 4 The image shown is a scanning electron microscope (SEM) image of the PDLC dimming film F2 in Example 2.

[0017] Figure 5 The electro-optic performance curves of PDLC dimming films F4 and F5 in Example 3 at the test temperature are shown.

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

[0019] Figure 7 The electro-optic performance curves of PDLC dimming films F8 and F9 in Example 5 at the test temperature are shown.

[0020] Figure 8 Here is a scanning electron microscope (SEM) image of the PDLC dimming film in Example 5 (F8).

[0021] Figure 9 The electro-optic performance curves of the PDLC dimming film F10 in Comparative Example 2 at the test temperature are shown.

[0022] Figure 10 This is a scanning electron microscope image of the PDLC dimming film F10 in Comparative Example 2. Detailed Implementation

[0023] The technical solution will now be clearly and completely described with reference to the embodiments of this application. Obviously, the described embodiments are only a part of the embodiments of this application, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0024] In the following description, the term "and / or" is used to describe the relationship between related objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists alone, B exists alone, and A and B exist simultaneously. A and B can be singular or plural.

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

[0026] Those skilled in the art should understand that, in the following description of the embodiments of this application, the sequence of numbers does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. 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 this application.

[0027] Those skilled in the art will understand that the numerical ranges in the embodiments of this application should be understood to specifically disclose each intermediate value between the upper and lower limits of the range. Each smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this application. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0028] Unless otherwise stated, the technical / scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. While this application describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this application. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0029] The technical principle employed in this invention is as follows: In the industrial production of PDLC thin films, the light utilization efficiency during the photopolymerization stage is the core bottleneck restricting production efficiency. Traditional processes rely on the ultraviolet photoinitiator Irgacure 651, whose absorption spectrum is limited to the ultraviolet bands of 250nm and 340nm. However, in actual production, ultraviolet light sources suffer from high energy consumption (>500W / m). 2 The high cost of equipment maintenance and the fact that ultraviolet light accounts for only about 5% of natural light limit photopolymerization efficiency to specific wavelengths. By introducing silver metavanadate (AgVO3) nanowires in combination with a light absorber, the V 3d-O 2p-Ag 4d hybrid valence band of AgVO3 forms a narrow bandgap structure of 1.9-2.2 eV, extending the light absorption boundary to the 550 nm visible light region. This creates a continuous coverage with the ultraviolet absorption band of the light absorber. Utilizing the complementary spectral properties of both, a broadband response system can be constructed by adapting 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 photoexcitation efficiency is provided, comprising a first transparent conductive layer, a polymer liquid crystal composite material layer and a second transparent conductive layer stacked sequentially, wherein the polymer liquid crystal composite material layer is made of photopolymerizable monomers, crosslinking agents, liquid crystals, photoinitiators and AgVO3 nanowires;

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

[0032] The photoinitiator is 0.5 to 2% by weight of the sum of the weight of the photopolymerizable monomer, the weight of the crosslinking agent, and the weight of the liquid crystal; the AgVO3 nanowires are 0.25 to 0.60% by weight of the sum of the weight of the photopolymerizable monomer, the weight of the crosslinking agent, and the weight of the liquid crystal.

[0033] This invention creatively introduces AgVO3 nanowires into the fabrication process of PDLC dimming films. Based on their performance characteristics of narrow bandgap, high light absorption capacity and high mobility, it provides a dimming film with a wide light response range and significantly improved photoelectric performance.

[0034] Especially when the weight of the photoinitiator is 0.5% to 2% of the sum of the weight of the photopolymerizable monomer, the crosslinking agent, and the liquid crystal, the applicable light absorption range of the photoinitiator and AgVO3 nanowires can be fully utilized to achieve light absorption in a wide range of spectra from ultraviolet to visible light. This breaks the limitations of traditional photoinitiators, whose absorption spectra are concentrated in the 250nm and 340nm ultraviolet regions and whose photochemical reaction intensity and efficiency are limited. The absorption wavelength range is extended to ultraviolet light and visible light with wavelengths less than 550nm, enabling the preparation of PDLC dimming films in a wider range of lighting environments.

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

[0036] During the experiment, it was found that the combined use of photoinitiator and AgVO3 nanowires, especially when the weight of the photoinitiator is 1.5 to 4 times that of the AgVO3 nanowires, can give full play to 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 of the electron-hole pairs generated under visible light excitation to produce 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] The study also revealed that, in addition to broadening the photoresponse range by combining with light absorbers, AgVO3 generates electrons (ep) under visible light excitation. - The benzoyloxy group (-0.34 eV vs NHE) is transferred to the LUMO orbital (-1.2 eV) of Irgacure651 via the interface, accelerating the generation efficiency of benzoyloxy radicals. Simultaneously, holes (h...) + AgVO3 (+2.56 eV) oxidizes acrylates to cationic radicals, opening up new polymerization pathways. When the mass ratio of AgVO3 to Irgacure 651 is 1:2, the absorbance of the composite photocatalytic system increases by 2.3 times in the 250-550 nm range, and the required ultraviolet light intensity increases from 80 mW / cm². 2 Reduced to 35mW / cm 2This significantly reduces equipment energy consumption. 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 monomer conversion 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 polymerized uniformly.

[0038] Secondly, it can achieve multi-field coupling control of light, heat, and electricity. The surface plasmon resonance effect of AgVO3 nanowires can convert 15% of the incident light into local heat energy, promoting polymer chain segment movement and accelerating phase separation. In addition, the carrier mobility of AgVO3 reaches 1.2 × 10⁻⁶. -3 cm 2 / V·s enables the polymer matrix to have charge dissipation capabilities, reducing surface resistivity by 3 orders of magnitude and effectively suppressing electrostatic adsorption pollution problems in outdoor applications.

[0039] In some embodiments, the photopolymerizable monomer comprises acrylates with large terminal groups and acrylates with alkyl terminal groups; and / or, the acrylates with large terminal groups comprise one or more of cyclohexyl methacrylate, isobornyl acrylate, 2-phenylethyl acrylate, 3,4-epoxycyclohexyl methacrylate, tetrahydrofuran acrylate, dicyclopentyl acrylate, phenyl acrylate, cyclohexyl acrylate, and glycidyl acrylate; and / or, the acrylates with alkyl terminal groups comprise 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 monomers are a blend of two monomers containing specific groups, namely acrylates with large terminal groups and acrylates with alkyl terminal groups, the acrylates with large terminal groups can delay chain termination, stabilize free radical intermediates, and react with VO3 on the AgVO3 surface. - The groups preferentially adsorb via hydrogen bonding, inducing a highly cross-linked network at the nanowire interface. The acrylates with terminal alkyl chains reduce the system viscosity and promote the oxidation of monomers by photogenerated holes to generate cationic radicals, providing a novel polymerization pathway. The polymerization behavior of the composite monomer, along with the multi-level synergy between the AgVO3 nanowires and the photoinitiator, enhances the polymerization rate.

[0041] Under the action of AgVO3 nanowires and photoinitiators, the composite monomers can enhance the polarization of photoinitiator molecules by utilizing the local surface plasmon effect, and promote free radical diffusion by utilizing their carrier migration ability. This allows branched crosslinking points to be constructed on the surface of acrylates with large terminal groups, and acrylates with alkyl chains at the ends to form an extended network in the main region, thus constructing a gradient interpenetrating network structure.

[0042] In some implementations, the weight ratio of acrylates with large terminal groups to acrylates with alkyl terminal chains is (1-3):1.

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

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

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

[0046] S1. After uniformly mixing the photopolymerizable monomer, crosslinking agent, liquid crystal, photoinitiator and AgVO3 nanowires, the mixture is poured between the first transparent conductive layer and the second transparent conductive layer to obtain sample A;

[0047] S2. Sample A is photocured under ultraviolet and / or visible light 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; the distance between the first transparent conductive layer and the second transparent conductive layer is 19 to 21 μm.

[0049] In some implementations, in step S2, the curing temperature is 0–10°C higher than the temperature at which the mixture is isotropic, the curing time is ≤500s, and the light intensity is 5–10mW / cm². 2 In some specific embodiments, the temperature at which the mixture is isotropic is room temperature.

[0050] This invention also provides a method for preparing the PDLC dimming film with a wide optical response range and high photoexcitation efficiency, which involves uniformly mixing raw materials and pouring them between liquid crystal cells composed of two conductive layers, followed by photocuring. Specifically, the photocuring temperature is 0–10°C higher than the isotropic temperature of the mixed system, the curing time is ≤500s, and the light intensity is 5–10 mW / cm². 2Under these conditions and at this temperature, liquid crystal molecules can remain in a disordered state during the initial stage of photopolymerization, reducing the hindrance to monomer diffusion. The curing time is ≤500s, and in some specific embodiments, the curing time is 400–500s, with a light intensity of 5–10 mW / cm². 2 Curing under these light intensity and illumination conditions can avoid local heat accumulation caused by excessive light intensity, and can also work synergistically with the broad-spectrum response of AgVO3 to further promote the full conversion of residual monomers, exhibiting a high photopolymerization reaction rate with a conversion rate of up to 98%.

[0051] On the other hand, an application of the aforementioned 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 decorations. For example, as a protective film for automotive glass, it can achieve dimming while effectively avoiding electrostatic adsorption in outdoor applications.

[0052] Prior to the application for this invention, a series of experiments were conducted. Some of the experimental results are listed below to provide a more detailed description of the invention. The following is a detailed description in conjunction with the embodiments.

[0053] In this invention, all percentages refer to mass percentages, and the meanings of each symbol are as follows:

[0054] T off T represents the light transmittance of the PDLC without an applied electric field (off-state transmittance); on This represents the light transmittance (on-state transmittance) of the PDLC under an applied electric field of 100V; V sat The saturation voltage refers to the voltage at which the light transmittance of the PDLC reaches T. on The voltage required to achieve 90% of the required voltage; CR represents the contrast ratio, which is calculated as: CR = T on / T off .

[0055] Example 1

[0056] This embodiment provides a PDLC dimming film with a wide light response range and high photoexcitation efficiency, comprising a first transparent conductive layer, a polymer liquid crystal composite material layer and a second transparent conductive layer stacked sequentially. The polymer liquid crystal composite material layer is made of photopolymerizable monomers, crosslinking agents, liquid crystals, photoinitiators and AgVO3 nanowires.

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

[0058] S1. Photopolymerizable monomers cyclohexyl methacrylate (CHMA), lauryl methacrylate (LMA), butyl acrylate (BA), crosslinking agent butylene diacrylate (BDDA), liquid crystal E8, UV photoinitiator Irg651, and AgVO3 nanowires were sampled and mixed according to Table 1. After thorough stirring, a mixed system was obtained. This mixed system was poured between two pieces of conductive glass coated with indium tin oxide (ITO), with a distance of 20.0 μm between the two ITO-coated conductive glass pieces, to obtain a liquid crystal layer. The ITO-coated conductive glass was purchased from Qingdao Taiweida Co., Ltd., 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 ≥99.0% and a normal optical refractive index and an extraordinary optical refractive index n. o =1.527 and n e =1.774, purchased from Jiangsu Hecheng Display Co., Ltd.; the temperature at which the hybrid system is isotropic is room temperature;

[0059] S2. The liquid crystal layer in S1 is subjected to 30℃ and ultraviolet light intensity of 10mW / cm². 2 Curing under these conditions for 500 seconds yielded a PDLC dimming film F1 with a wide light response range and high photoexcitation efficiency.

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

[0061] Table 1 Composition of the samples in Example 1

[0062]

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

[0064] Table 2 Main electro-optic 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] Combination Figure 1 As shown in Table 2, both PDLC dimming films F0 and F1 exhibited traditional voltage-transmittance (VT) curves. However, under the influence of AgVO3, the saturation voltage of sample F1 was approximately 20V, with a contrast ratio exceeding 185, and both on-state and off-state transmittance increased. Compared to PDLC dimming film F0 without AgVO3 nanowires, the PDLC dimming film of Example 1 showed a significantly lower saturation voltage and a significantly higher contrast ratio.

[0067] The polymer network of the PDLC dimming film F1 was observed using scanning electron microscopy (SEM), and the results are as follows: Figure 2 As shown; by Figure 2 It can be seen that the average pore size of the polymer mesh in F1 is 1-2 μm, and the sample surface is smooth and neat, which is consistent with its high contrast. This proves that the addition of AgVO3 nanowires effectively improves the polymerization rate of photopolymerizable monomers, restricts the diffusion of liquid crystals, and thus forms good phase separation.

[0068] Example 2

[0069] This embodiment provides a PDLC dimming film with a wide light response range and high photoexcitation efficiency, comprising a first transparent conductive layer, a polymer liquid crystal composite material layer and a second transparent conductive layer stacked sequentially. The polymer liquid crystal composite material layer is made of photopolymerizable monomers, crosslinking agents, liquid crystals, photoinitiators and AgVO3 nanowires.

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

[0071] S1. Photopolymerizable monomers cyclohexyl methacrylate (CHMA), lauryl methacrylate (LMA), butyl acrylate (BA), crosslinking agent hexanediol diacrylate (HDDA), liquid crystal E8, UV photoinitiator Irg651, and AgVO3 nanowires were sampled and mixed according to Table 3. After thorough stirring, a mixed system was obtained. The mixed system was poured between two pieces of conductive glass coated with indium tin oxide (ITO), with a distance of 20.0 μm between the two ITO-coated conductive glass pieces, to obtain a liquid crystal layer. The ITO-coated conductive glass was purchased from Qingdao Taiweida Co., Ltd., 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 ≥99.0% and a normal optical refractive index and an extraordinary optical refractive index n. o =1.527 and n e =1.774, purchased from Jiangsu Hecheng Display Co., Ltd.; the temperature at which the hybrid system is isotropic is room temperature;

[0072] S2. The liquid crystal layer in S1 is subjected to 30℃ and ultraviolet light intensity of 10mW / cm². 2 Curing under these conditions for 500 seconds yielded a PDLC dimming film F2 with a wide optical response range and high photoexcitation efficiency.

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

[0074] Table 3 Composition of the samples in Example 2

[0075]

[0076]

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

[0078] Table 4. Main electro-optic 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] Combination Figure 3 As shown in Table 4, the PDLC dimming films F2 and F3 exhibited the traditional voltage-transmittance (VT) curves. Meanwhile, under the influence of AgVO3, the saturation voltage of sample F2 decreased, the contrast increased, and both the on-state transmittance and the off-state transmittance increased.

[0081] The polymer network of the PDLC dimming film F2 was observed using scanning electron microscopy (SEM), and the results are as follows: Figure 4 As shown; by Figure 4 It is known that the average pore size of the polymer mesh in F2 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 the liquid crystal, and thus forms a good phase separation.

[0082] Comparative Example 1

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

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

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

[0086]

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

[0088] Table 6. Main electro-optic 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] Combination Figure 5 As shown in Table 6, PDLC dimming films F4 and F5 exhibit conventional voltage-transmittance (VT) curves. PDLC dimming film F4, with the addition of AgVO3 nanowires, shows a lower saturation voltage and improved contrast compared to PDLC dimming film F5 without AgVO3 nanowires. However, the saturation voltage of PDLC dimming film F4 is 61.2V, which is nearly 40V higher than the saturation voltage of PDLC dimming film F1 in Example 1 (22.6V), while the contrast ratio remains largely the same.

[0091] The polymer network of the PDLC dimming film F4 was observed using scanning electron microscopy (SEM), and the results are as follows: Figure 6 As shown; by Figure 6 It is known that the polymer pores of F4 are small and the pore structure collapses severely. Previous research results of this invention show that when acrylates with large terminal groups and acrylates with alkyl terminal chains are used as UV-polymerizable monomers, the physicochemical properties of the prepared PDLC dimming film are related to the crosslinking agent. Specifically, the longer the chain length or the larger the molecular weight of the crosslinking agent, the larger the pores of the PDLC dimming film polymer. This is because the longer the chain length or the larger the molecular weight of the crosslinking agent, 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 polymer pore size and a severe loss of sample contrast. This invention has found that under the condition of long-chain long crosslinking agent, the addition of AgVO3 nanowires can inhibit the expansion of polymer pores and avoid a severe decrease in contrast.

[0092] Example 3

[0093] This embodiment provides a PDLC dimming film with a wide light response range and high photoexcitation efficiency, comprising a first transparent conductive layer, a polymer liquid crystal composite material layer and a second transparent conductive layer stacked sequentially. The polymer liquid crystal composite material layer is made of photopolymerizable monomers, crosslinking agents, liquid crystals, photoinitiators and AgVO3 nanowires.

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

[0095] S1. Photopolymerizable monomers cyclohexyl methacrylate (CHMA), lauryl methacrylate (LMA), ethyl acrylate (HA), crosslinking agent butylene diacrylate (BDDA), liquid crystal E8, UV photoinitiator Irg651, and AgVO3 nanowires were sampled and mixed according to Table 7. After thorough stirring, a mixed system was obtained. This mixed system was poured between two pieces of conductive glass coated with indium tin oxide (ITO), with a distance of 20.0 μm between the two ITO-coated conductive glass pieces, to obtain a liquid crystal layer. The ITO-coated conductive glass was purchased from Qingdao Taiweida Co., Ltd., 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 ≥99.0% and a normal optical refractive index and an extraordinary optical refractive index n. o =1.527 and n e =1.774, purchased from Jiangsu Hecheng Display Co., Ltd.; the temperature at which the hybrid system is isotropic is room temperature;

[0096] S2. The liquid crystal layer in S1 is subjected to an ultraviolet light intensity of 5mW / cm at 30℃. 2 The luminous intensity of the white LED is 10mW / cm². 2 Cured under the specified conditions for 400s, a PDLC dimming film with a wide light response range and high light excitation efficiency was obtained and labeled as F6; the main peak of the white LED was 450nm.

[0097] Example 4

[0098] This embodiment examines the effect of photocuring conditions on the performance of PDLC dimming films. The method for preparing the PDLC dimming film is the same as in Example 3, except that S2 is performed by curing the liquid crystal layer in S1 at 30°C and with an ultraviolet light intensity of 5mW / cm². 2 Cured under the specified conditions for 400 seconds, the PDLC dimming film was obtained and labeled as F7.

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

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

[0101]

[0102] Table 8. Main electro-optic properties of the samples in Examples 3 and 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 analyzed using infrared spectroscopy. The absorption peak area of ​​the characteristic functional group C=C double bond of the acrylate in the sample is integrated to determine the peak area attenuation after curing. The final monomer conversion rate is then calculated using the following formula: Final monomer conversion rate % = (1-A t / A0)*100; where A0 and A t The peak areas of the characteristic peak C=C at the initial time and time t are respectively.

[0105] As shown in Table 8, with a curing time of 400 s, the final monomer conversion rate of PDLC dimming film F6 is 93.7%, and that of F7 is 84.2%. The polymerization conversion rate under visible light + ultraviolet light initiation conditions is about 10% higher than that under ultraviolet light initiation alone. The method of this invention has visible light response and can polymerize over a wide range of illumination, enabling accelerated polymerization preparation of PDLC dimming films under a wider range of illumination conditions. Furthermore, compared to PDLC dimming film F7, PDLC dimming film F6 shows a slight increase in contrast and a slight decrease in saturation voltage, indicating that the method of this invention can slightly improve the photoelectric performance of PDLC dimming films while overcoming the limitations of current PDLC dimming film preparation processes in terms of light response.

[0106] Example 5

[0107] This embodiment provides a PDLC dimming film with a wide light response range and high photoexcitation efficiency, comprising a first transparent conductive layer, a polymer liquid crystal composite material layer and a second transparent conductive layer stacked sequentially. The polymer liquid crystal composite material layer is made of photopolymerizable monomers, crosslinking agents, liquid crystals, photoinitiators and AgVO3 nanowires.

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

[0109] S1. Photopolymerizable monomers phenyl acrylate (PA), 2-ethylhexyl acrylate (EHA), butyl acrylate (BA), crosslinking agent 1,4-butylene diacrylate (BDDA), liquid crystal E8, UV photoinitiator Irg651, and AgVO3 nanowires were sampled and mixed according to Table 9. After thorough stirring, a mixed system was obtained. This mixed system was poured between two pieces of conductive glass coated with indium tin oxide (ITO), with a distance of 20.0 μm between the two ITO-coated conductive glass pieces, to obtain a liquid crystal layer. The ITO-coated conductive glass was purchased from Qingdao Taiweida Co., Ltd., 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 ≥99.0% and a normal optical refractive index and an extraordinary optical refractive index n. o =1.527 and ne =1.774, purchased from Jiangsu Hecheng Display Co., Ltd.; the temperature at which the hybrid system is isotropic is room temperature;

[0110] S2. The liquid crystal layer in S1 is subjected to 30℃ and ultraviolet light intensity of 10mW / cm². 2 Curing under these conditions for 500 seconds yielded a PDLC dimming film F8 with a wide light response range and high photoexcitation efficiency.

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

[0112] Table 9 Composition of the samples in Example 5

[0113]

[0114]

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

[0116] Table 10 Main electro-optic 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] Combination Figure 7 As shown in Table 10, both PDLC dimming films F8 and F9 exhibited traditional voltage-transmittance (VT) curves. Meanwhile, under the influence of AgVO3, the saturation voltage of sample F8 decreased, the contrast increased, and both the on-state transmittance and the off-state transmittance increased.

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

[0120] Comparative Example 2

[0121] This embodiment examines the effect of the amount of AgVO3 nanowires added on the performance of PDLC dimming film. The preparation method is the same as in Example 1, except that 0.1 wt.% of the total weight of AgVO3 nanowires, monomers, crosslinking agents and liquid crystals is labeled as F10. The composition of the sample is compared with that of the F1 sample in Example 1 as shown in Table 11, and the main photoelectric properties are shown in Table 12.

[0122] Table 11 Comparison of the composition of PDLC dimming film F10 in Comparative Example 2 and PDLC dimming film F1 in Example 1

[0123]

[0124]

[0125] The electro-optic performance curves of the PDLC dimming film F10 at the test temperature were measured using a liquid crystal comprehensive parameter tester, as follows: Figure 9 As shown.

[0126] Table 12 Comparison of main photoelectric properties of PDLC dimming film F10 in Comparative Example 2 and PDLC dimming film F1 in 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] Combination Figure 9 As shown in Table 12, the PDLC dimming film F10 in this comparative example exhibits a conventional voltage-transmittance (VT) curve that is basically consistent with that of F1. However, compared to F1, the saturation voltage of sample F10 increases, while the contrast ratio decreases significantly. This indicates that when the amount of AgVO3 nanowires is too low—that is, when the ratio of AgVO3 nanowires to the sum of the weights of photopolymerizable monomers, crosslinking agents, and liquid crystals is less than 0.25%—it will be detrimental to improving the photoelectric performance of the PDLC dimming film. Figure 10 The image shows a scanning electron microscope (SEM) image of the PDLC dimming film F10, which reveals severe collapse of the polymer network pores.

Claims

1. A PDLC dimming film with a wide optical response range and high photoexcitation efficiency, characterized in that, It includes a first transparent conductive layer, a polymer liquid crystal composite material layer and a second transparent conductive layer stacked sequentially. The raw materials of the polymer liquid crystal composite material layer include photopolymerizable monomers, crosslinking agents, liquid crystals, photoinitiators and AgVO3 nanowires. In the raw materials, the weight parts of liquid crystal are 1.5 to 4 times the sum of the weight parts of photopolymerizable monomer and crosslinking agent; the weight parts of photopolymerizable monomer are 1 to 5 times the weight parts of crosslinking agent. The photoinitiator is 0.5-2% by weight of the sum of the photopolymerizable monomer, crosslinking agent, and liquid crystal; the AgVO3 nanowires are 0.25-0.60% by weight of the sum of the photopolymerizable monomer, crosslinking agent, and liquid crystal.

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

3. The PDLC dimming film with a wide optical response range and high photoexcitation efficiency according to claim 1, characterized in that, The photopolymerizable monomers include acrylates with large terminal groups and acrylates with alkyl terminal chains.

4. The PDLC dimming film with a wide optical response range and high photoexcitation efficiency according to claim 3, characterized in that, The acrylates with large terminal groups include one or more of cyclohexyl methacrylate, isobornyl acrylate, 2-phenylethyl acrylate, 3,4-epoxycyclohexyl methacrylate, tetrahydrofuran acrylate, dicyclopentyl acrylate, phenyl acrylate, cyclohexyl acrylate, and glycidyl acrylate; and / or, the acrylates containing alkyl chains at the ends include 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 optical response range and high photoexcitation efficiency according to claim 3, characterized in that, The weight ratio of acrylates with large terminal groups to acrylates with alkyl terminal chains is (1-3):

1.

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

7. The PDLC dimming film with a wide optical response range and high photoexcitation efficiency according to claim 1, characterized in that, The photoinitiator is one or more of benzoin ether, 2-hydroxy-2-methyl-1-phenylpropanone, trimethylbenzoyl diphenylphosphine oxide, and benzoin diethyl ether.

8. A method for preparing a PDLC dimming film with a wide optical response range and high photoexcitation efficiency as described in claim 1, characterized in that, include: S1. After uniformly mixing the photopolymerizable monomer, crosslinking agent, liquid crystal, photoinitiator and AgVO3 nanowires, the mixture is poured between the first transparent conductive layer and the second transparent conductive layer to obtain sample A; S2. Sample A is photocured under ultraviolet and / or visible light to obtain a PDLC dimming film.

9. The method according to claim 8, characterized in that, In step S1, both the first and second transparent conductive layers are conductive glass plated 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 a PDLC dimming film with a wide optical response range and high photoexcitation efficiency as described in claim 1.

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