A low-driving-voltage electrically controlled dimming film and its preparation method

Abstract

This application belongs to the field of functional liquid crystal material preparation technology, and discloses a low-driving-voltage electrically controlled dimming film and its preparation method. The raw materials include: polymerizable acrylate monomers, halogenated acrylate polymerizable monomers, liquid crystal materials, glass microspheres, and a photoinitiator; wherein the mass ratio of the halogenated acrylate polymerizable monomers to the acrylate polymerizable monomers is (0.13~0.39):1. In this application, the polymerizable acrylate monomers and halogenated acrylate polymerizable monomers are polymerized to construct a polymer matrix, which increases the steric hindrance of the double bonds to be polymerized, slowing down the phase separation process in the polymerization reaction. The network structure of the polymer matrix becomes more uniform, the porosity is reduced, and the liquid crystal droplets are uniformly distributed in the network structure of the polymer matrix; at the same time, the mesh size in the network structure of the polymer matrix increases, and the mesh size is uniform, generating larger liquid crystal droplets. The electrically controlled dimming film of this application has a lower driving voltage, higher contrast, and a simple preparation method.

Description

Technical Field

[0001] This application belongs to the field of functional liquid crystal material preparation technology, specifically relating to an electrically controlled dimming film with low driving voltage and its preparation method. Background Technology

[0002] Polymer-dispersed liquid crystal (PDLC) films are a type of electrically controlled liquid crystal dimming film, possessing advantages such as high sensitivity, fast response time, and simple preparation process. In PDLC films, liquid crystals are uniformly dispersed in the form of microdroplets within a polymer matrix. Without an applied electric field, the directores of the liquid crystal molecules are randomly distributed. Due to the mismatch in refractive indices between the liquid crystal molecules and the polymer matrix, the PDLC film exhibits light scattering. After applying an electric field, the directores of the liquid crystal molecules align uniformly along the direction of the electric field. At this point, the refractive index of the liquid crystal microdroplets matches the refractive index of the polymer matrix, and the PDLC film becomes transparent.

[0003] When an external voltage is applied, the director of the liquid crystal molecules in a PDLC film aligns uniformly along the direction of the electric field, requiring overcoming the resistance between the liquid crystal and the polymer matrix. To achieve high adhesion strength, existing PDLC films typically have a high polymer matrix content. However, this high polymer matrix content leads to significant resistance between the liquid crystal and the polymer matrix, resulting in excessively high operating voltages for the PDLC film, generally around 50–85V.

[0004] Patent application CN 110256810 B discloses a low-drive-voltage electro-controlled liquid crystal dimming film that combines polymer-dispersed liquid crystal (PDLC) and polymer-stabilized liquid crystal (PSLC). This is achieved by adding crystalline UV-polymerizable monomers to a thermally polymerized PDLC system, followed by thermal polymerization of the mixture. An electric field is then applied to a conductive film to align the liquid crystal molecules vertically. UV light irradiation initiates the polymerization of the crystalline photopolymerizable monomers, forming a vertically oriented polymer network similar to that of PSLC within the liquid crystal microdroplets. This constructs a PD&SLC coexistence structure, thereby reducing the drive voltage of the electro-controlled liquid crystal dimming film. However, this low-drive-voltage electro-controlled liquid crystal dimming film requires a variety of raw materials and undergoes two polymerization reactions, resulting in a complex manufacturing process. Summary of the Invention

[0005] This application discloses an electrically controlled dimming film with low driving voltage. The preparation process is simple. A polymer matrix is ​​constructed by polymerizable monomers of acrylate and halogenated acrylate. The polymer matrix has a uniform network structure and few voids. During the polymerization process, liquid crystal material generates large-sized liquid crystal droplets with uniform size in the polymer matrix. The liquid crystal droplets are evenly distributed in the polymer matrix, which reduces the resistance when the liquid crystal droplets turn in the polymer matrix, thereby reducing the driving voltage of the electrically controlled dimming film.

[0006] To achieve the above objectives, the present application adopts the following technical solution.

[0007] This application provides an electrically controlled dimming film with low driving voltage, the raw materials of which include:

[0008] Acrylates are polymerizable monomers;

[0009] Halogenated acrylates can polymerize monomers;

[0010] liquid crystal materials;

[0011] Glass microspheres;

[0012] Photoinitiator;

[0013] The mass ratio of the halogenated acrylate polymerizable monomer to the acrylate polymerizable monomer is (0.13-0.39):1.

[0014] In some implementation schemes, the raw materials include:

[0015] The total amount of polymerizable monomers of acrylate and halogenated polymerizable monomers is 25.0 to 40.0 parts, liquid crystal material is 60.0 to 75.0 parts, photoinitiator is 0.5 to 3 parts, and glass microspheres are 0 to 1.0 parts.

[0016] In some embodiments, the liquid crystal material is a nematic liquid crystal material;

[0017] The nematic liquid crystal material has a birefringence > 0.10, a crystallization point < -40℃, a clearing point < 200℃, a viscosity < 120 mPa·S, and a dielectric anisotropy > 5.

[0018] Preferably, the halogenated form of the acrylic polymer monomer has a mass percentage of 12-28 wt% in the UV-polymerizable monomer.

[0019] In some embodiments, the polymerizable monomer of the acrylate is at least one selected from 2-methoxyethyl acrylate, allyl acrylate, methyl acrylate, isobornyl acrylate, 1,4-butanediol diacrylate, and 1,5-pentanediol diacrylate.

[0020] In some embodiments, the halogenated acrylate polymerizable monomer is at least one selected from methyl α-chloroacrylate, methyl α-bromoacrylate, methyl α-fluoroacrylate, ethyl α-chloroacrylate, ethyl α-fluoroacrylate, and ethyl α-bromoacrylate.

[0021] In some embodiments, the photoinitiator is at least one selected from benzoin butyl ether, benzoin dimethyl ether, benzoin ethyl ether, diphenyl ethyl ketone, and benzophenone.

[0022] In some embodiments, the glass microspheres have a diameter of 5.5 μm to 20 μm.

[0023] Another aspect of this application provides a method for preparing the above-mentioned low-driving-voltage electrically controlled dimming film, comprising the following steps:

[0024] The liquid crystal material, polymerizable acrylate monomers and halogenated polymerizable acrylate monomers are mixed evenly, and then an initiator and glass microspheres are added and mixed to obtain a uniform mixture.

[0025] The mixture is transferred to a transparent liquid crystal molding mold and cured by ultraviolet light irradiation to obtain an electronically controlled dimming film with low driving voltage.

[0026] In some embodiments, the liquid crystal molding die is made of conductive glass or a conductive plastic film.

[0027] In some embodiments, the ultraviolet light intensity during the ultraviolet irradiation curing is 2 mW / cm². 2 ~20mW / cm 2 UV curing time is 120s to 1200s.

[0028] Compared with the prior art, the beneficial effects of this application are as follows:

[0029] This application prepares an electrically controlled dimming film via ultraviolet light polymerization of polymerizable acrylate monomers, halogenated acrylate monomers, and liquid crystal materials. The polymerizable acrylate monomers and halogenated acrylate monomers construct a polymer matrix through polymerization. Due to the larger volume of halogen atoms, the double bonds to be polymerized experience greater steric hindrance, slowing down the polymerization reaction and thus the phase separation process. This results in a more uniform network structure and reduced porosity in the polymer matrix of the electrically controlled dimming film, allowing for a more uniform distribution of liquid crystal droplets within the network. Furthermore, the increased and consistent pore size in the polymer matrix network leads to larger and more uniform liquid crystal droplets, facilitating their reorientation. The unique structure of this electrically controlled dimming film significantly reduces the resistance to droplet reorientation within the polymer matrix, thereby lowering the driving voltage of the film and achieving high contrast.

[0030] The preparation method of this application is simple and easy to operate, the reaction is mild and controllable, the curing time is short, and it is conducive to large-scale industrial production. Attached Figure Description

[0031] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 This is a SEM image of the electro-controlled dimming film prepared in Example 1 of this application;

[0033] Figure 2 The voltage-transmittance curve of the electro-controlled dimming film prepared in Example 1 of this application;

[0034] Figure 3 This is a SEM image of the electro-controlled dimming film prepared in Example 2 of this application;

[0035] Figure 4 The voltage-transmittance curve of the electro-controlled dimming film prepared in Example 2 of this application;

[0036] Figure 5 SEM image of the electro-controlled dimming film prepared in Comparative Example 1 of this application;

[0037] Figure 6 The voltage-transmittance curve is shown for the electro-dimming film prepared in Comparative Example 1 of this application.

[0038] Figure 7 SEM image of the electro-controlled dimming film prepared in Comparative Example 2 of this application;

[0039] Figure 8 This is a voltage-transmittance curve of the electro-controlled dimming film prepared in Comparative Example 2 of this application. Detailed Implementation

[0040] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. 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.

[0041] In the following description of this embodiment, the terms "including", "comprising", "having", and "containing" are all open-ended terms, meaning that they include but are not limited to.

[0042] In the following description of this embodiment, the term "and / or" is used to describe the association relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, B existing alone, and A and B existing simultaneously. A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0043] In the following description of this embodiment, the term "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0044] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms "a" and "the" as used in the embodiments of this application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0045] 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.

[0046] 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 within the scope of this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0047] 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.

[0048] Embodiments of this application provide an electrically controlled dimming film with low driving voltage, the raw materials of which include:

[0049] Acrylates are polymerizable monomers;

[0050] Halogenated acrylates can polymerize monomers;

[0051] liquid crystal materials;

[0052] Glass microspheres;

[0053] Photoinitiator;

[0054] The mass ratio of the halogenated acrylate polymerizable monomer to the acrylate polymerizable monomer is (0.13-0.39):1.

[0055] This application describes the preparation of an electrically controlled dimming film via ultraviolet light polymerization of polymerizable acrylate monomers, halogenated acrylate monomers, and liquid crystal materials. The polymerizable acrylate monomers and halogenated acrylate monomers form the polymer matrix through polymerization. Due to the larger volume of halogen atoms, the double bonds to be polymerized experience greater steric hindrance, slowing down the polymerization reaction and thus reducing the phase separation process during polymerization.

[0056] The mass ratio of the halogenated acrylate polymerizable monomer to the acrylate polymerizable monomer is (0.13–0.39):1. Under this ratio, on the one hand, the network structure of the polymer matrix in the electro-dimming film is uniformly distributed with reduced porosity, allowing liquid crystal droplets to be uniformly distributed within the polymer matrix network structure; on the other hand, the mesh size in the polymer matrix network structure increases and becomes more uniform, generating larger liquid crystal droplets with good uniformity, making them easier to redirect. The electro-dimming film of this application significantly reduces the resistance to liquid crystal droplet redirection within the polymer matrix, thereby reducing the driving voltage of the electro-dimming film while maintaining high contrast.

[0057] In the embodiments of this application, the raw materials for the low-drive-voltage electrically controlled dimming film include:

[0058] The total amount of polymerizable monomers of acrylate and halogenated polymerizable monomers is 25.0 to 40.0 parts, liquid crystal material is 60.0 to 75.0 parts, photoinitiator is 0.5 to 3 parts, and glass microspheres are 0 to 1.0 parts.

[0059] The liquid crystal material used in this application is preferably a nematic liquid crystal material, and more preferably a nematic liquid crystal material with a birefringence > 0.10, a crystallization point < -40℃, a clearing point < 200℃, a viscosity < 120mPa·S, and a dielectric anisotropy > 5.

[0060] The nematic liquid crystal material described in this application is composed of rod-shaped molecules with a large aspect ratio, and the molecular centroids lack long-range order. It exhibits fluidity similar to ordinary liquids; the molecules are not arranged in layers, but can slide up and down, left and right, and back and forth, maintaining parallelism or near-parallelism only along their long axes. Without an applied electric field, the directores of the nematic liquid crystal molecules are randomly distributed; when an electric field is applied to both ends, the directores of the nematic liquid crystal molecules uniformly align along the direction of the electric field.

[0061] It should be noted that commercially available liquid crystal materials can be selected for nematic liquid crystal materials, such as E8 and E7 from Merck Liquid Crystal Materials Co., Ltd. in Germany, and GXP-6908, GXP-6917, and GXP-6928 from Yantai Xianhua Liquid Crystal Materials Co., Ltd., but are not limited to these materials.

[0062] The polymerizable monomers of the acrylates in this application are any one or a mixture of several of the following: 2-methoxyethyl acrylate, allyl acrylate, methyl acrylate, isobornyl acrylate, 1,4-butanediol diacrylate, and 1,5-pentanediol diacrylate.

[0063] Specifically, the polymerizable monomers for acrylates may be isoborneol acrylate, allyl acrylate, 2-methoxyethyl acrylate, methyl acrylate, or mixtures of isoborneol acrylate and 1,4-butanediol diacrylate, mixtures of isoborneol acrylate and 2-methoxyethyl acrylate, mixtures of allyl acrylate and 1,4-butanediol diacrylate, or mixtures of isoborneol acrylate and 1,5-pentanediol diacrylate.

[0064] The halogenated acrylate monomers of this application are any one or a mixture of several of methyl chloroacrylate, methyl bromoacrylate, methyl fluoroacrylate, ethyl chloroacrylate, ethyl fluoroacrylate, and ethyl bromoacrylate.

[0065] Specifically, the polymerizable monomers of the halogenated acrylate can be selected from methyl α-chloroacrylate, methyl α-bromoacrylate, methyl α-fluoroacrylate, ethyl α-chloroacrylate, ethyl α-fluoroacrylate, or ethyl α-bromoacrylate, or a mixture of methyl α-chloroacrylate and methyl α-bromoacrylate, a mixture of methyl α-chloroacrylate and methyl α-fluoroacrylate, or a mixture of ethyl α-chloroacrylate and ethyl α-fluoroacrylate.

[0066] Acrylic polymerizable monomers and halogenated acrylic polymerizable monomers, after being polymerized by ultraviolet light irradiation, become the polymer matrix of the electrically controlled dimming film of this application. Liquid crystals are uniformly dispersed in the polymer matrix in the form of microdroplets. During the ultraviolet light irradiation polymerization process, halogen atoms slow down the phase separation process in the polymerization reaction, making the polymer network structure more uniform, reducing porosity, and increasing and unifying the mesh size in the network structure. This allows the polymer network structure to accommodate larger liquid crystal microdroplets, and the liquid crystal microdroplets are uniformly distributed within the polymer network structure, exhibiting good uniformity.

[0067] In this embodiment, the photoinitiator is at least one selected from benzoin butyl ether, benzoin dimethyl ether, benzoin ethyl ether, diphenyl ethyl ketone, and benzophenone. The photoinitiator is used for the ultraviolet irradiation polymerization of polymerizable acrylate monomers and halogenated polymerizable acrylate monomers to generate a polymer matrix.

[0068] In this embodiment, the photoinitiator is preferably benzoin dimethyl ether, model Irg651, whose structural formula is shown below:

[0069]

[0070] In this embodiment, glass microspheres are used to control the thickness of the dimming film, and the diameter of the glass microspheres is preferably 5.5 μm to 20 μm.

[0071] To enable those skilled in the art to further understand the technical solutions of this application, the following embodiments will be used to provide a more detailed description of this application.

[0072] In Examples 1-4 and Comparative Examples 1-2 below, the liquid crystal material used is a hybrid liquid crystal E8, with the following specific composition:

[0073]

[0074] In Examples 1-4 and Comparative Examples 1-2, the polymerizable monomers of acrylates were selected as a mixture of isobornyl acrylate and 1,4-butanediol diacrylate, and the polymerizable monomers of halogenated acrylates were selected as methyl α-chloroacrylate.

[0075] The ratios of polymerizable acrylate monomers to polymerizable halogenated acrylate monomers in Examples 1-4 and Comparative Examples 1-2 are shown in Table 1:

[0076] Table 1. Ratio of polymerizable monomers of acrylates to polymerizable monomers of halogenated acrylates

[0077]

[0078] Example 1

[0079] This embodiment prepares an electrically controlled dimming film with low driving voltage, including:

[0080] S1, isobornyl acrylate, 1,4-butanediol diacrylate and methyl α-chloroacrylate are prepared according to the proportion of monomer 1 in Table 1, and stirred evenly to obtain monomer mixture; the monomer mixture is mixed with liquid crystal E8 at a weight ratio of 3:7 and shaken evenly to obtain polymerizable mixture A.

[0081] S2, add 2 parts of photoinitiator and 1 part of glass microspheres to polymerizable mixture A, stir evenly at room temperature to obtain polymerizable mixture B;

[0082] S3, the polymerizable mixture B is poured into a transparent conductive glass liquid crystal mold coated with ITO, and then irradiated and cured at room temperature using ultraviolet light with a wavelength of 365nm in an ultraviolet curing chamber. The ultraviolet light intensity is 4.5mW / cm2, and the curing time is 600s, resulting in an electrically controlled dimming film with a low driving voltage, denoted as X1.

[0083] X1 was cut into small pieces and immersed in cyclohexane solution for two weeks to remove the liquid crystal phase. The microstructure of the sample was observed using a scanning electron microscope, such as... Figure 1 As shown, the polymer matrix in X1 has a uniform network structure with few voids; the mesh size is relatively large, with an average mesh size of 0.8 μm, and the mesh size tends to be consistent.

[0084] The electro-optical properties of X1 at room temperature were tested using a liquid crystal comprehensive parameter analyzer, and its voltage-transmittance curve is shown in the figure below. Figure 2 As shown, X1 has a threshold voltage of 6.01042V, a saturation voltage of 10.9972V, and a contrast ratio of 11.6.

[0085] Example 2

[0086] This embodiment prepares an electrically controlled dimming film with low driving voltage, including:

[0087] S1, isobornyl acrylate, 1,4-butanediol diacrylate and methyl α-chloroacrylate are prepared according to the ratio of monomer 2 in Table 1, and stirred evenly to obtain monomer mixture; the monomer mixture is mixed with liquid crystal E8 at a weight ratio of 3:7 and shaken evenly to obtain polymerizable mixture A.

[0088] S2, add 2 parts of photoinitiator and 1 part of glass microspheres to polymerizable mixture A, stir evenly at room temperature to obtain polymerizable mixture B;

[0089] S3, the polymerizable mixture B is poured into a transparent conductive glass liquid crystal mold coated with ITO, and then irradiated and cured at room temperature using ultraviolet light with a wavelength of 365nm in an ultraviolet curing chamber. The ultraviolet light intensity is 4.5mW / cm2, and the curing time is 600s, resulting in an electrically controlled dimming film with a low driving voltage, denoted as X2.

[0090] X2 was cut into small pieces and immersed in cyclohexane solution for two weeks to remove the liquid crystal phase. The microstructure of the sample was observed using a scanning electron microscope, such as... Figure 3 As shown, the network structure of the polymer matrix in X2 is uniformly distributed with virtually no voids; and the mesh size is further increased, with an average mesh size of 1.5 μm, and the mesh size tends to be uniform.

[0091] The electro-optical properties of X2 at room temperature were tested using a liquid crystal comprehensive parameter analyzer, and its voltage-transmittance curve is shown in the figure below. Figure 4 As shown, X2 has a threshold voltage of 3.5157V, a saturation voltage of 8.00256V, and a contrast ratio of 28.

[0092] Comparative Example 1

[0093] This embodiment prepares an electrically controlled dimming film, including:

[0094] S1, isobornyl acrylate, 1,4-butanediol diacrylate and methyl α-chloroacrylate are prepared according to the ratio of monomer D1 in Table 1, and stirred evenly to obtain monomer mixture; the monomer mixture is mixed with liquid crystal E8 at a weight ratio of 3:7 and shaken thoroughly to obtain polymerizable mixture A.

[0095] S2, add 2 parts of photoinitiator and 1 part of glass microspheres to polymerizable mixture A, stir evenly at room temperature to obtain polymerizable mixture B;

[0096] S3, the polymerizable mixture B is poured into a transparent conductive glass liquid crystal mold coated with ITO, and then cured by irradiation with ultraviolet light at a wavelength of 365nm at room temperature in an ultraviolet curing chamber. The ultraviolet light intensity is 4.5mW / cm². 2 The curing time is 600s, resulting in an electrically controlled dimming film with low driving voltage, denoted as D1.

[0097] The electrically controlled dimming film D1 was cut into small pieces and immersed in cyclohexane solution for two weeks to remove the liquid crystal phase. The microstructure of the sample was observed using a scanning electron microscope, such as... Figure 5 As shown, the network structure of the polymer matrix in D1 is uneven with too many voids; and the mesh size is small, with an average mesh size of 0.6 μm and varying mesh sizes.

[0098] The electro-optic performance of the electro-optical dimming film D1 at room temperature was tested using a liquid crystal comprehensive parameter analyzer, and its voltage-transmittance curve is shown in the figure below. Figure 6 As shown, the threshold voltage of the electronically controlled dimming film D1 is 9.00256V, the saturation voltage is 24.4516V, and the contrast ratio is 6.1.

[0099] Comparative Example 2

[0100] This embodiment prepares an electrically controlled dimming film with low driving voltage, including:

[0101] S1, isobornyl acrylate, 1,4-butanediol diacrylate and methyl α-chloroacrylate are prepared according to the ratio of monomer D2 in Table 1, and stirred evenly to obtain monomer mixture; the monomer mixture is mixed with liquid crystal E8 at a weight ratio of 3:7 and shaken evenly to obtain polymerizable mixture A.

[0102] S2, add 2 parts of photoinitiator and 1 part of glass microspheres to polymerizable mixture A, stir evenly at room temperature to obtain polymerizable mixture B;

[0103] S3, the polymerizable mixture B is poured into a transparent conductive glass liquid crystal mold coated with ITO, and then irradiated and cured at room temperature using ultraviolet light with a wavelength of 365nm in an ultraviolet curing chamber. The ultraviolet light intensity is 4.5mW / cm2, and the curing time is 600s, resulting in an electrically controlled dimming film with a low driving voltage, denoted as D2.

[0104] D2 was cut into small pieces and immersed in cyclohexane solution for two weeks to remove the liquid crystal phase. The microstructure of the sample was observed using a scanning electron microscope, such as... Figure 7 As shown, the polymer matrix in D2 has a uniform network structure with no voids, and the mesh size is further increased, with an average mesh size of 2.5 μm. However, the mesh sizes are not uniform and there is a large difference in mesh size.

[0105] The electro-optical properties of D2 at room temperature were tested using a liquid crystal comprehensive parameter analyzer, and its voltage-transmittance curve is shown in the figure below. Figure 8 As shown, D2 has a threshold voltage of 1.62766V, a saturation voltage of 13.4898V, and a contrast ratio of 10.2.

[0106] The electro-optic data of the electro-optic films prepared in Comparative Examples 1-2 and Examples 1-2 are shown in Table 2.

[0107] Table 2. Electro-optical data of the electro-optical dimming films in the comparative examples and embodiments.

[0108] Threshold voltage / V Saturation voltage / V Contrast Example 1 6.01042 10.9972 11.6 Example 2 3.5157 8.00256 28 Comparative Example 1 9.00256 24.4516 6.1 Comparative Example 2 1.62766 13.4898 10.2

[0109] By comparing and analyzing the SEM images and voltage-transmittance curves of the electrically controlled dimming films prepared in Examples 1-2 and Comparative Examples 1-2, it can be seen that:

[0110] The electrochromic film D1 prepared in Comparative Example 1 did not contain methyl α-chloroacrylate in its raw materials, such as... Figure 5 As shown, the polymer matrix of D1 has an uneven network structure with too many voids; the mesh size is small, with an average mesh size of 0.6 μm and varying mesh sizes. The liquid crystal droplets are unevenly distributed, and the small size of the liquid crystal microdroplets results in a high driving voltage, with a threshold voltage of 9.00256 V, a saturation voltage of 24.4516 V, and a contrast ratio of 6.1.

[0111] The electrically controlled dimming film X1 prepared in Example 1 and the electrically controlled dimming film X2 prepared in Example 2 both incorporated methyl α-chloroacrylate as raw materials. With increasing methyl α-chloroacrylate content, the network structure of the polymer matrix of the dimming film became more uniform, the porosity decreased, and eventually there were no porosity; the mesh size gradually increased, and the mesh size tended to be uniform, such as... Figure 1 and Figure 3 As shown. In the electrically controlled dimming film X1, the liquid crystal droplets are more uniformly distributed, the droplet size is larger, and the driving voltage is lower, with a threshold voltage of 6.01042V and a saturation voltage of 10.9972V, significantly lower than that of the electrically controlled dimming film D1. The contrast ratio is 11.6, higher than that of the electrically controlled dimming film D1. In the electrically controlled dimming film X2, the liquid crystal droplet distribution is even more uniform, the droplet size is larger, and the driving voltage is lower, with a threshold voltage of only 3.5157V and a saturation voltage of 8.00256V, further lower than that of the electrically controlled dimming film X1. The contrast ratio is 28, higher than that of the electrically controlled dimming film X1.

[0112] In Comparative Example 2, when the sum of the amounts of methyl α-chloroacrylate, isobornyl acrylate, and 1,4-butanediol diacrylate exceeded 0.39:1, the SEM image of the electronically controlled dimming film D2 is shown below. Figure 7 As shown, although the mesh size gradually increases, the polymer network structure becomes uneven, and the mesh size varies considerably. The liquid crystal droplet size further increases, but the droplet size becomes inconsistent, and the droplet distribution becomes uneven. Larger droplets cause the threshold voltage to further decrease to 1.62766V; however, due to the inconsistent droplet size and uneven droplet distribution, the saturation voltage increases to 13.4898V, while the contrast ratio decreases to 10.2. The electrical performance of the electrically controlled dimming film D2 deteriorates.

[0113] When the ratio of the sum of the amounts of methyl α-chloroacrylate, isobornyl acrylate, and 1,4-butanediol diacrylate is in the range of (0.13–0.39):1, the prepared electro-dimming film exhibits better electrical properties.

[0114] Example 3

[0115] This embodiment prepares an electrically controlled dimming film with low driving voltage, including:

[0116] S1, isobornyl acrylate, 1,4-butanediol diacrylate and methyl α-chloroacrylate are prepared according to the ratio of monomer 3 in Table 1, and stirred evenly to obtain monomer mixture; the monomer mixture is mixed with liquid crystal E8 at a weight ratio of 4:6, and shaken evenly to obtain polymerizable mixture A.

[0117] S2, add 2 parts of photoinitiator and 1 part of glass microspheres to polymerizable mixture A, stir evenly at room temperature to obtain polymerizable mixture B;

[0118] S3, the polymerizable mixture B is poured into a transparent conductive glass liquid crystal mold coated with ITO, and then cured by irradiation with ultraviolet light at a wavelength of 365nm at room temperature in an ultraviolet curing chamber. The ultraviolet light intensity is 4.5mW / cm². 2 The curing time was 600s, resulting in an electro-optical dimming film with low driving voltage, denoted as X3. The electro-optical properties of X3 are similar to those of X2, with lower threshold voltage and saturation voltage, as well as higher contrast.

[0119] Example 4

[0120] This embodiment prepares an electrically controlled dimming film with low driving voltage, including:

[0121] S1, isobornyl acrylate, 1,4-butanediol diacrylate and methyl α-chloroacrylate are prepared according to the ratio of monomer 4 in Table 1, and stirred evenly to obtain monomer mixture; the monomer mixture is mixed with liquid crystal E8 at a weight ratio of 2.5:7.5, and shaken thoroughly to obtain polymerizable mixture A;

[0122] S2, add 2 parts of photoinitiator and 1 part of glass microspheres to polymerizable mixture A, stir evenly at room temperature to obtain polymerizable mixture B;

[0123] S3, the polymerizable mixture B is poured into a transparent conductive glass liquid crystal mold coated with ITO, and then cured by irradiation with ultraviolet light at a wavelength of 365nm at room temperature in an ultraviolet curing chamber. The ultraviolet light intensity is 4.5mW / cm². 2 The curing time was 600s, resulting in an electro-optical dimming film with low driving voltage, denoted as X4. The electro-optical properties of X4 are similar to those of X2, with lower threshold voltage and saturation voltage, as well as higher contrast.

[0124] Example 5

[0125] This embodiment uses the same method as Example 2, except that isoborneol acrylate is replaced with allyl acrylate, and the ultraviolet light intensity is 18 mW / cm². 2The curing time was 150 seconds, while all other process parameters and materials remained unchanged. The resulting electro-optical film exhibited electro-optical properties similar to X2, both possessing low threshold voltage and saturation voltage, as well as high contrast.

[0126] Example 6

[0127] This embodiment uses the same method as Example 2, except that methyl α-chloroacrylate is replaced with any one of methyl α-bromoacrylate, methyl α-fluoroacrylate, ethyl α-chloroacrylate, ethyl α-fluoroacrylate, or ethyl α-bromoacrylate, while all other process parameters and materials remain unchanged. The resulting electro-optical film has electro-optical properties similar to X2, exhibiting low threshold voltage and saturation voltage, as well as high contrast.

[0128] Example 7

[0129] This embodiment uses the same method as Example 2, except that the liquid crystal E8 is replaced with GXP-6908 from Yantai Xianhua Liquid Crystal Materials Co., Ltd., while all other process parameters and materials remain unchanged. The resulting electro-optical film has similar electro-optical properties to X2, both exhibiting low threshold voltage and saturation voltage, as well as high contrast.

[0130] Although the present invention has been described in detail in this specification with general description and specific embodiments, some modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention are within the scope of protection claimed by the present invention.

Claims

1. A low-drive-voltage electrically controlled dimming film, characterized in that, Its raw materials include: Acrylates are polymerizable monomers; Halogenated acrylates can polymerize monomers; liquid crystal materials; Glass microspheres; Photoinitiator; The mass ratio of the halogenated acrylate polymerizable monomer to the acrylate polymerizable monomer is (0.13~0.39):1; Its preparation methods include: The liquid crystal material, polymerizable acrylate monomers and halogenated polymerizable acrylate monomers are mixed evenly, and then a photoinitiator and glass microspheres are added and mixed to obtain a uniform mixture. The mixture is transferred to a transparent liquid crystal molding mold and cured by ultraviolet light irradiation to obtain an electronically controlled dimming film with low driving voltage.

2. The low-drive-voltage electrically controlled dimming film according to claim 1, characterized in that, Its raw materials include: The total amount of polymerizable monomers of acrylate and halogenated polymerizable monomers is 25.0~40.0 parts, liquid crystal material is 60.0~75.0 parts, photoinitiator is 0.5~3 parts, and glass microspheres are 0~1.0 parts.

3. The low-drive-voltage electrically controlled dimming film according to claim 1 or 2, characterized in that, The liquid crystal material is a nematic liquid crystal material; The nematic liquid crystal material has a birefringence > 0.10, a crystallization point < -40℃, a clearing point < 200℃, a viscosity < 120 mPa·S, and a dielectric anisotropy > 5.

4. The low-drive-voltage electrically controlled dimming film according to claim 2, characterized in that, The polymerizable monomer of the acrylate is at least one selected from 2-methoxyethyl acrylate, allyl acrylate, methyl acrylate, isobornyl acrylate, 1,4-butanediol diacrylate, and 1,5-pentanediol diacrylate.

5. The low-drive-voltage electrically controlled dimming film according to claim 2, characterized in that, The polymerizable monomers of the halogenated acrylate are at least one selected from methyl α-chloroacrylate, methyl α-bromoacrylate, methyl α-fluoroacrylate, ethyl α-chloroacrylate, ethyl α-fluoroacrylate, and ethyl α-bromoacrylate.

6. The low-drive-voltage electrically controlled dimming film according to claim 2, characterized in that, The photoinitiator is at least one of benzoin butyl ether, benzoin dimethyl ether, benzoin ethyl ether, diphenyl ethyl ketone, and benzophenone.

7. The low-drive-voltage electrically controlled dimming film according to claim 1, characterized in that, The glass microspheres have a diameter of 5.5 μm to 20 μm.

8. The low-drive-voltage electrically controlled dimming film according to claim 1, characterized in that, The liquid crystal molding die is made of conductive glass or conductive plastic film.

9. The low-drive-voltage electrically controlled dimming film according to claim 1, characterized in that, In the ultraviolet irradiation curing process, the ultraviolet light intensity is 2 mW / cm. 2 ~20mW / cm 2 UV curing time is 120s~1200s.

Images