A high-transmittance intelligent liquid crystal dimming film and its preparation method

Abstract

The present invention relates to the field of lenses, specifically to a high-transmittance intelligent liquid crystal dimming film and its preparation method. The film comprises a polymer-dispersed liquid crystal material layer, with flexible transparent conductive films disposed on both the upper and lower surfaces of the polymer-dispersed liquid crystal material layer; the polymer-dispersed liquid crystal material layer is obtained by curing the polymer-dispersed liquid crystal material. The present invention prepares a high-transmittance intelligent liquid crystal dimming film that utilizes two layers of flexible transparent conductive films (ITO films) wrapped around a layer of polymer-dispersed liquid crystal material (PDLC). Compared to traditional liquid crystal dimming films, the intelligent liquid crystal dimming film obtained by the present invention exhibits significantly improved transmittance at various voltages.

Description

Technical Field

[0001] The present invention relates to the field of lenses, and in particular to a high-transmittance intelligent liquid crystal dimming film and a preparation method thereof. Background Art

[0002] With the continued rapid growth of the national economy, the domestic building materials market has developed rapidly. Due to the significant reduction in costs, intelligent electric-controlled dimming glass has gradually been accepted by the construction and design industries and has begun to be used on a large scale. As costs continue to fall and market prices drop, dimming glass has also begun to enter the field of home decoration applications. In the near future, this practical high-tech product will enter thousands of households, and its application prospects are very promising.

[0003] Liquid crystal dimming film is an important type of electrically controlled dimming glass. Currently, the most commonly used dimming film material is polymer-dispersed liquid crystal film (PDLC). PDLC is a thin film formed by micron-sized liquid crystal droplets embedded in a continuous polymer matrix. The film itself can switch between transparent and non-transparent states, with transparency adjusted by voltage, thereby regulating natural light. Under electric field control, the film utilizes the external field responsiveness of liquid crystal molecules and the degree of refractive index matching between the liquid crystal droplets and the polymer matrix to switch between light-scattering and transparent states. However, the polymer-dispersed liquid crystal (PDLC) materials currently developed and used by domestic manufacturers have low transmittance when powered, affecting overall performance and requiring improvement. Summary of the Invention

[0004] In view of the problems existing in the prior art, the purpose of the present invention is to provide a high-transmittance intelligent liquid crystal dimming film and a preparation method thereof.

[0005] The purpose of the present invention is achieved by adopting the following technical solutions:

[0006] In a first aspect, the present invention provides a high-transmittance intelligent liquid crystal dimming film, comprising a polymer dispersed liquid crystal material layer (PDLC), wherein the upper and lower surfaces of the polymer dispersed liquid crystal material layer (PDLC) are both provided with a flexible transparent conductive film (ITO film, indium tin oxide).

[0007] Preferably, the thickness of the polymer dispersed liquid crystal material layer is 10-20 μm, and the thickness of the flexible transparent conductive film is 30-80 μm.

[0008] Preferably, the polymer dispersed liquid crystal material layer is obtained by curing a polymer dispersed liquid crystal material, and the polymer dispersed liquid crystal material, calculated by weight, comprises:

[0009] 32-64 parts of liquid crystal material, 15-45 parts of monomer material, 0.1-1 part of photoinitiator and 2-10 parts of solvent.

[0010] Preferably, the liquid crystal material is liquid crystal material E7, liquid crystal material TEB30, or liquid crystal material TEB50; more preferably, liquid crystal material E7.

[0011] Among them, the parameters of liquid crystal material E7 are: contrast ratio of 53.9, maximum transmittance of 90.3%, minimum transmittance of 1.62%, and turn-on voltage of 1.2V; the parameters of liquid crystal material TEB30 are: contrast ratio of 9.7, maximum transmittance of 85.2%, minimum transmittance of 8.7%, and turn-on voltage of 3.6V; the parameters of liquid crystal material TEB50 are: contrast ratio of 7.7, maximum transmittance of 80.1%, minimum transmittance of 10.35%, and turn-on voltage of 3.2V.

[0012] Preferably, the monomer material is a mixture of N-vinylcaprolactam, hexafluorobutyl acrylate, methylallyldiethoxysilane and vinyl polyimide.

[0013] More preferably, the mass ratio of N-vinylcaprolactam, hexafluorobutyl acrylate, methylallyldiethoxysilane, and vinyl polyimide is 1.4-3.6:2.1-8.4:0.8-1.6:1.2-3.6.

[0014] Preferably, the photoinitiator is at least one of benzoin monomethyl ether, benzoin dimethyl ether, 1-hydroxy-cyclohexyl-phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, and phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide.

[0015] Preferably, the solvent is at least one of ethyl acetate, ethyl formate, dichloromethane, cyclohexane, and dimethyl carbonate, more preferably ethyl acetate.

[0016] Preferably, the preparation method of the vinyl polyimide comprises:

[0017] S1. Dissolve 1,4-bis(2,4-diaminophenoxy)benzene in N,N-dimethylformamide in an ice-water bath, then add maleic anhydride, stir in an ice-water bath for 0.2-0.8 h, then warm to room temperature and continue stirring for 1-2 h to obtain a first mixed solution;

[0018] S2. Place the first mixed solution in an ice-water bath again, add 4,4'-diaminodiphenyl ether and 4,4'-diaminobiphenyl in sequence, stir to fully dissolve, then add pyromellitic dianhydride, and stir in an ice-water bath for 2-5 hours to obtain a second mixed solution;

[0019] S3. Add toluene to the second mixed liquid, stir thoroughly, then add p-toluenesulfonic acid, heat to 110-130°C, keep reflux for 10-20 hours, cool to room temperature after the reaction is completed, collect the solid by centrifugation, wash and dry to obtain vinyl polyimide.

[0020] More preferably, in S1, the mass ratio of 1,4-bis(2,4-diaminophenoxy)benzene, maleic anhydride and N,N-dimethylformamide is 0.16-0.32:0.1-0.3:30-60.

[0021] More preferably, in S2, the mass ratio of 4,4'-diaminodiphenyl ether, 4,4'-diaminobiphenyl, pyromellitic dianhydride and the first mixed liquid is 1.5-2.5:1.3-2.1:5.4-8.1:30-60.

[0022] More preferably, in S3, the mass ratio of p-toluenesulfonic acid, toluene and the second mixed liquid is 0.03-0.1:4-8:30-60.

[0023] In a second aspect, the present invention provides a method for preparing a high-transmittance intelligent liquid crystal dimming film, comprising:

[0024] Step 1: taking the components of the polymer dispersed liquid crystal material in proportion by weight, and uniformly mixing them to form a polymer dispersed liquid crystal mixture;

[0025] Step 2: Take a piece of flexible transparent conductive film, lay it flat with the conductive surface facing upward, and then apply the polymer dispersed liquid crystal mixture on the flexible transparent conductive film, maintaining a uniform coating process;

[0026] Step 3: Take another piece of flexible transparent conductive film and cover it on the polymer dispersed liquid crystal mixture with the conductive surface facing downward, so that the polymer dispersed liquid crystal material is evenly dispersed between the two layers of flexible transparent conductive film;

[0027] Step 4: Curing is performed by ultraviolet light treatment. The treatment time is 1-5 minutes. The wavelength of ultraviolet light is 200-450nm and the light intensity is 45-95mW / cm 2 ‌.

[0028] The beneficial effects of the present invention are:

[0029] 1. This invention has developed a high-transmittance intelligent liquid crystal dimming film. This film utilizes two layers of flexible transparent conductive film (ITO film) wrapped around a layer of polymer dispersed liquid crystal (PDLC). Compared to traditional liquid crystal dimming films, this intelligent liquid crystal dimming film exhibits significantly improved transmittance at various voltages.

[0030] 2. Polymer-dispersed liquid crystal materials can be transformed into two states: transparent and scattering under the condition of electricity. The materials that affect their optical properties are mainly liquid crystal materials and monomer materials. The present invention has adjusted and tested the monomer materials and found that when certain liquid crystal materials (especially liquid crystal material E7) are used, the monomer materials are N-vinylcaprolactam, hexafluorobutyl acrylate, methylallyl diethoxysilane, and vinyl polyimide mixed in a certain proportion. The polymer-dispersed liquid crystal material can make light more easily penetrate the glass and become transparent under the action of the electric field, thereby achieving higher transparency.

[0031] 3. The monomers used in preparing the polymer-dispersed liquid crystal material of this invention include, firstly, an acrylic monomer (hexafluorobutyl acrylate) with improved stability and temperature resistance, secondly, a vinyl monomer (N-vinylcaprolactam) and an allylsilane (methylallyldiethoxysilane) with excellent hardness and flexibility, and, in addition, a unique vinyl-containing polymer (vinyl polyimide) as a monomer. Post-use testing has shown that, under the same liquid crystal material conditions, the polymer-dispersed liquid crystal material prepared according to this invention exhibits improved transparency in PDLC. DETAILED DESCRIPTION

[0032] The technical solution of the present invention is described below through specific examples. It should be understood that the one or more method steps mentioned in the present invention do not exclude the presence of other method steps before and after the combination step or the insertion of other method steps between these explicitly mentioned steps; it should also be understood that these embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention. Moreover, unless otherwise specified, the numbering of each method step is only a convenient tool for identifying each method step, and is not intended to limit the order of arrangement of each method step or to define the scope of the present invention. Changes or adjustments in their relative relationships, without substantially changing the technical content, should also be regarded as the scope of the present invention.

[0033] In order to better understand the above technical solutions, exemplary embodiments of the present invention are described in more detail below. Although exemplary embodiments of the present invention are shown, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.

[0034] The present invention will be further described below with reference to the following examples.

[0035] Example 1

[0036] A method for preparing a high-transmittance intelligent liquid crystal dimming film, comprising:

[0037] Step 1: Taking the components of the polymer dispersed liquid crystal material in proportion by weight, the polymer dispersed liquid crystal material includes: 48 parts of liquid crystal material E7, 30 parts of monomer material, 0.3 parts of photoinitiator and 8 parts of solvent, and uniformly mixing the components to form a polymer dispersed liquid crystal mixture;

[0038] Step 2: Take a piece of flexible transparent conductive film with a thickness of 50 μm, lay it flat with the conductive surface facing upward, and then apply the polymer dispersed liquid crystal mixture on the flexible transparent conductive film, maintaining a uniform coating process;

[0039] Step 3: Take another piece of flexible transparent conductive film with a thickness of 50 μm and cover it on the polymer dispersed liquid crystal mixture with the conductive surface facing downward, so that the polymer dispersed liquid crystal material is evenly dispersed between the two layers of flexible transparent conductive film;

[0040] Step 4: Curing is performed by ultraviolet light treatment. The treatment time is 3 minutes, the wavelength of ultraviolet light is 365nm, and the light intensity is 65mW / cm 2 ‌, the thickness of the obtained polymer dispersed liquid crystal material layer is 15 μm.

[0041] Among them, the liquid crystal material is liquid crystal material E7, and the parameters of liquid crystal material E7 are: contrast ratio of 53.9, maximum transmittance of 90.3%, minimum transmittance of 1.62%, and turn-on voltage of 1.2V; the monomer materials include: N-vinylcaprolactam, hexafluorobutyl acrylate, methyl allyl diethoxysilane, and vinyl polyimide in a mass ratio of 2.5:6.7:1.2:2.4; the photoinitiator is benzoin dimethyl ether; and the solvent is ethyl acetate.

[0042] Wherein, the preparation method of vinyl polyimide comprises:

[0043] S1. In an ice-water bath, 0.24 g of 1,4-bis(2,4-diaminophenoxy)benzene was dissolved in 45 mL of N,N-dimethylformamide, and 0.2 g of maleic anhydride was added. The mixture was stirred in an ice-water bath for 0.5 h, and then the mixture was heated to room temperature and stirred for 1.5 h to obtain a first mixed solution.

[0044] S2. Place the first mixed solution in an ice-water bath again, add 2 g of 4,4'-diaminodiphenyl ether and 1.9 g of 4,4'-diaminobiphenyl in sequence, stir until fully dissolved, then add 6.7 g of pyromellitic dianhydride, and stir in an ice-water bath for 3 h to obtain a second mixed solution;

[0045] S3. Add 6 g of toluene to the second mixed liquid, stir thoroughly, then add 0.06 g of p-toluenesulfonic acid, heat to 120°C, keep reflux for 15 hours, cool to room temperature after the reaction is completed, collect the solid by centrifugation, wash and dry to obtain vinyl polyimide.

[0046] Example 2

[0047] A method for preparing a high-transmittance intelligent liquid crystal dimming film, comprising:

[0048] Step 1: Taking the components of the polymer dispersed liquid crystal material in proportion by weight and uniformly mixing them to form a polymer dispersed liquid crystal mixture; the polymer dispersed liquid crystal material layer is obtained by curing the polymer dispersed liquid crystal material, and the polymer dispersed liquid crystal material comprises, by weight, 32 parts of liquid crystal material, 15 parts of monomer material, 0.1 parts of photoinitiator and 2 parts of solvent;

[0049] Step 2: Take a piece of flexible transparent conductive film with a thickness of 30 μm, lay it flat with the conductive surface facing upward, and then apply the polymer dispersed liquid crystal mixture on the flexible transparent conductive film, maintaining a uniform coating process;

[0050] Step 3: Take another piece of flexible transparent conductive film with a thickness of 30 μm and cover it on the polymer dispersed liquid crystal mixture with the conductive surface facing downward, so that the polymer dispersed liquid crystal material is evenly dispersed between the two layers of flexible transparent conductive film;

[0051] Step 4: Curing is performed by ultraviolet light treatment. The treatment time is 1 minute, the wavelength of ultraviolet light is 365nm, and the light intensity is 45mW / cm 2 ‌, the thickness of the obtained polymer dispersed liquid crystal material layer is 10 μm.

[0052] The liquid crystal material is TEB30, and the parameters of the TEB30 liquid crystal material are: contrast ratio of 9.7, maximum transmittance of 85.2%, minimum transmittance of 8.7%, and turn-on voltage of 3.6V; the monomer materials are N-vinylcaprolactam, hexafluorobutyl acrylate, methylallyl diethoxysilane, and vinyl polyimide in a mass ratio of 1.4:8.4:0.8:3.6; the photoinitiator is 1-hydroxy-cyclohexyl-phenyl ketone; and the solvent is dichloromethane. The preparation method of the vinyl polyimide is the same as in Example 1.

[0053] Example 3

[0054] A method for preparing a high-transmittance intelligent liquid crystal dimming film, comprising:

[0055] Step 1: Taking the components of the polymer dispersed liquid crystal material in proportion by weight and uniformly mixing them to form a polymer dispersed liquid crystal mixture; the polymer dispersed liquid crystal material layer is obtained by curing the polymer dispersed liquid crystal material, and the polymer dispersed liquid crystal material comprises, by weight, 64 parts of liquid crystal material, 45 parts of monomer material, 1 part of photoinitiator and 10 parts of solvent;

[0056] Step 2: Take a piece of flexible transparent conductive film with a thickness of 80 μm, lay it flat with the conductive surface facing upward, and then apply the polymer dispersed liquid crystal mixture on the flexible transparent conductive film, maintaining a uniform coating process;

[0057] Step 3: Take another piece of flexible transparent conductive film with a thickness of 80 μm and cover it on the polymer dispersed liquid crystal mixture with the conductive surface facing downward, so that the polymer dispersed liquid crystal material is evenly dispersed between the two layers of flexible transparent conductive film;

[0058] Step 4: Curing is performed by ultraviolet light treatment. The treatment time is 5 minutes, the wavelength of ultraviolet light is 365nm, and the light intensity is 95mW / cm 2 ‌, the thickness of the obtained polymer dispersed liquid crystal material layer is 20 μm.

[0059] The liquid crystal material is TEB50, and the parameters of the TEB50 liquid crystal material are: contrast ratio of 7.7, maximum transmittance of 80.1%, minimum transmittance of 10.35%, and turn-on voltage of 3.2V; the monomer materials are N-vinylcaprolactam, hexafluorobutyl acrylate, methylallyl diethoxysilane, and vinyl polyimide in a mass ratio of 3.6:2.1:1.6:1.2; the photoinitiator is 2-hydroxy-2-methyl-1-phenyl-1-propanone; and the solvent is cyclohexane. The preparation method of the vinyl polyimide is the same as that in Example 1.

[0060] Example 4

[0061] A method for preparing a high-transmittance intelligent liquid crystal dimming film, comprising:

[0062] Step 1: Taking the components of the polymer dispersed liquid crystal material in proportion by weight and uniformly mixing them to form a polymer dispersed liquid crystal mixture; the polymer dispersed liquid crystal material layer is obtained by curing the polymer dispersed liquid crystal material, and the polymer dispersed liquid crystal material comprises, by weight, 58 parts of liquid crystal material E7, 35 parts of monomer material, 0.4 parts of photoinitiator and 7 parts of solvent;

[0063] Step 2: Take a piece of flexible transparent conductive film with a thickness of 45 μm, lay it flat with the conductive surface facing upward, and then apply the polymer dispersed liquid crystal mixture on the flexible transparent conductive film, maintaining a uniform coating process;

[0064] Step 3: Take another piece of flexible transparent conductive film with a thickness of 45 μm and cover it on the polymer dispersed liquid crystal mixture with the conductive surface facing downward, so that the polymer dispersed liquid crystal material is evenly dispersed between the two layers of flexible transparent conductive film;

[0065] Step 4: Curing is performed by ultraviolet light treatment. The treatment time is 2 minutes, the wavelength of ultraviolet light is 365nm, and the light intensity is 50mW / cm 2 ‌, the thickness of the obtained polymer dispersed liquid crystal material layer is 10 μm.

[0066] The liquid crystal material is liquid crystal material E7, and its parameters are: contrast ratio of 53.9, maximum transmittance of 90.3%, minimum transmittance of 1.62%, and turn-on voltage of 1.2V. The monomer materials include: N-vinylcaprolactam, hexafluorobutyl acrylate, methylallyl diethoxysilane, and vinyl polyimide in a mass ratio of 2.5:6.7:1.2:2.4; the photoinitiator is benzoin dimethyl ether; and the solvent is ethyl acetate. The preparation method of the vinyl polyimide is the same as in Example 1.

[0067] Comparative Example 1

[0068] A high-transmittance intelligent liquid crystal dimming film, the preparation method of which differs from that of Example 1 only in that, in the composition of the polymer-dispersed liquid crystal material layer, the monomer materials include: N-vinylcaprolactam, hexafluorobutyl acrylate, and methylallyl diethoxysilane in a mass ratio of 3.3:7.5:2.

[0069] Comparative Example 2

[0070] A high-transmittance intelligent liquid crystal dimming film, the preparation method of which differs from that of Example 1 only in that the monomer materials in the composition of the polymer dispersed liquid crystal material layer include: hexafluorobutyl acrylate, methyl allyl diethoxysilane, and vinyl polyimide in a mass ratio of 3.3:7.5:2.

[0071] Comparative Example 3

[0072] A high-transmittance intelligent liquid crystal dimming film, the preparation method of which differs from that of Example 1 only in that, in the composition of the polymer dispersed liquid crystal material layer, the monomer materials include: N-vinylcaprolactam, methyl allyl diethoxysilane, and vinyl polyimide in a mass ratio of 3.3:7.5:2.

[0073] Comparative Example 4

[0074] A high-transmittance intelligent liquid crystal dimming film, the preparation method of which differs from that of Example 1 only in that, in the composition of the polymer dispersed liquid crystal material layer, the monomer materials include: N-vinylcaprolactam, hexafluorobutyl acrylate, and vinyl polyimide in a mass ratio of 3.3:7.5:2.

[0075] The transmittance of the smart liquid crystal dimming films prepared in Example 1 and Comparative Examples 1-4 was tested at a temperature of 25±2°C and a humidity of 55±5RH%. The test equipment was an HT-15A optical transmittance tester. The test results are shown in Table 1:

[0076] Table 1 Transmittance performance of the dimming film under different voltage conditions

[0077]

[0078] The test results in Table 1 show significant differences in the performance of polymer-dispersed liquid crystal material layers obtained from different monomer compositions. The smart liquid crystal dimming film prepared in Example 1 of the present invention achieved a transmittance of 86.7% at 60V and 89.2% at 110V, significantly outperforming the other comparative examples. This demonstrates that the smart liquid crystal dimming film prepared in Example 1 of the present invention can achieve significant improvements in transmittance at different voltages. The data for Comparative Example 1 is significantly worse than those for Comparative Examples 2-4, indicating that the influence of vinyl polyimide in the monomer material is significantly greater than that of the other components.

[0079] In the description of this specification, reference to the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms should not be understood as necessarily referring to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any suitable manner in any one or more embodiments or examples. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification.

[0080] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A high-transmittance intelligent liquid crystal dimming film, characterized in that: The invention comprises a polymer dispersed liquid crystal material layer, wherein the upper and lower surfaces of the polymer dispersed liquid crystal material layer are both provided with a flexible transparent conductive film; wherein the polymer dispersed liquid crystal material layer is obtained by curing the polymer dispersed liquid crystal material, and the polymer dispersed liquid crystal material is calculated by weight and comprises: 32-64 parts of liquid crystal material, 15-45 parts of monomer material, 0.1-1 part of photoinitiator and 2-10 parts of solvent; The monomer material is a mixture of N-vinyl caprolactam, hexafluorobutyl acrylate, methyl allyl diethoxysilane and vinyl polyimide; The mass ratio of N-vinylcaprolactam, hexafluorobutyl acrylate, methylallyldiethoxysilane and vinyl polyimide is 1.4-3.6:2.1-8.4:0.8-1.6:1.2-3.

6.

2. The high-transmittance intelligent liquid crystal dimming film according to claim 1, characterized in that: The thickness of the polymer dispersed liquid crystal material layer is 10-20 μm, and the thickness of the flexible transparent conductive film is 30-80 μm.

3. The high-transmittance intelligent liquid crystal dimming film according to claim 1, characterized in that: The liquid crystal material is liquid crystal material E7, liquid crystal material TEB30, or liquid crystal material TEB50.

4. The high-transmittance intelligent liquid crystal dimming film according to claim 1, characterized in that: The photoinitiator is at least one of benzoin monomethyl ether, benzoin dimethyl ether, 1-hydroxy-cyclohexyl-phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, and phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide.

5. The high-transmittance intelligent liquid crystal dimming film according to claim 1, characterized in that: The solvent is at least one of ethyl acetate, ethyl formate, dichloromethane, cyclohexane, and dimethyl carbonate.

6. A method for preparing the high-transmittance intelligent liquid crystal dimming film according to claim 1, characterized in that: include: Step 1: taking the components of the polymer dispersed liquid crystal material in proportion by weight, and uniformly mixing them to form a polymer dispersed liquid crystal mixture; Step 2: Take a piece of flexible transparent conductive film, lay it flat with the conductive surface facing upward, and then apply the polymer dispersed liquid crystal mixture on the flexible transparent conductive film, maintaining a uniform coating process; Step 3: Take another piece of flexible transparent conductive film and cover it on the polymer dispersed liquid crystal mixture with the conductive surface facing downward, so that the polymer dispersed liquid crystal material is evenly dispersed between the two layers of flexible transparent conductive film; Step 4: Curing is performed by ultraviolet light treatment. The treatment time is 1-5 minutes. The wavelength of ultraviolet light is 200-450nm and the light intensity is 45-95mW / cm 2 ‌.

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