High-transmittance intelligent liquid crystal dimming film and preparation method thereof

Abstract

The invention relates to the field of lenses, in particular to a high-transmittance intelligent liquid crystal dimming film and a preparation method thereof.The high-transmittance intelligent liquid crystal dimming film comprises a polymer dispersed liquid crystal material layer, and flexible transparent conductive films are arranged on the upper surface and the lower surface of the polymer dispersed liquid crystal material layer; wherein the polymer dispersed liquid crystal material layer is obtained by curing a polymer dispersed liquid crystal material. The invention discloses a high-transmittance intelligent liquid crystal dimming film. The dimming film adopts a mode of wrapping a layer of polymer dispersed liquid crystal material (PDLC) with two layers of flexible transparent conductive films (ITO films). Compared with a traditional liquid crystal light adjusting film, the transmittance of the intelligent liquid crystal light adjusting film can be obviously improved under the condition of different power-on 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 sustained rapid growth of the national economy, the domestic building materials market has developed rapidly. As the cost of intelligent electric-controlled dimming glass has dropped significantly, it has gradually been accepted by the construction and design industries and has begun to be used on a large scale. With the further reduction of costs and the reduction of market prices, 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. 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 dimming film material itself can be switched between transparent and non-transparent states, and the transparency is adjusted by voltage, thereby achieving the adjustment of natural light. Under the control of the electric field, the film uses the external field responsiveness of liquid crystal molecules and can switch between the light scattering state and the transparent state according to the matching degree of the refractive index of the liquid crystal droplets and the polymer matrix. However, the polymer dispersed liquid crystal PDLC material currently developed and used by domestic manufacturers has a low transmittance after power is turned on, which affects the overall use effect and needs to be improved. Summary of the invention

[0004] In view of the problems existing in the prior art, an object 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 the following technical solutions: 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).

[0006] 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.

[0007] Preferably, the polymer dispersed liquid crystal material layer is obtained by curing the polymer dispersed liquid crystal material, and the polymer dispersed liquid crystal material, calculated by weight, includes: 32-64 parts of liquid crystal material, 15-45 parts of monomer material, 0.1-1 parts of photoinitiator and 2-10 parts of solvent.

[0008] 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.

[0009] 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.

[0010] Preferably, the monomer material is a mixture of N-vinyl caprolactam, hexafluorobutyl acrylate, methyl allyl diethoxy silane and vinyl polyimide.

[0011] 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.

[0012] 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.

[0013] Preferably, the solvent is at least one of ethyl acetate, ethyl formate, dichloromethane, cyclohexane and dimethyl carbonate, more preferably ethyl acetate.

[0014] Preferably, the preparation method of the vinyl polyimide comprises: S1. Dissolve 1,4-bis(2,4-diaminophenoxy)benzene in N,N-dimethylformamide in an ice-water bath, add maleic anhydride, stir for 0.2-0.8h in an ice-water bath, heat to room temperature and continue stirring for 1-2h to obtain a first mixed solution; S2, placing the first mixed solution in an ice water bath again, adding 4,4'-diaminodiphenyl ether and 4,4'-diaminobiphenyl in sequence, stirring to fully dissolve, then adding pyromellitic anhydride, stirring in an ice water bath for 2-5 hours, to obtain a second mixed solution; S3. Add toluene to the second mixed liquid, stir thoroughly, then add p-toluenesulfonic acid, heat to 110-130°C, keep reflux for 10-20h, after the reaction is completed, cool to room temperature, collect solids by centrifugation, wash and dry to obtain vinyl polyimide.

[0015] 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.

[0016] More preferably, in S2, the mass ratio of 4,4'-diaminodiphenyl ether, 4,4'-diaminobiphenyl, pyromellitic acid dianhydride and the first mixed liquid is 1.5-2.5:1.3-2.1:5.4-8.1:30-60.

[0017] 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.

[0018] In a second aspect, the present invention provides a method for preparing a high-transmittance intelligent liquid crystal dimming film, comprising: Step 1, taking the components of the polymer dispersed liquid crystal material according to the weight ratio, and evenly 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, and keep the coating process uniform; 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 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 ‌.

[0019] The beneficial effects of the present invention are: 1. The present invention prepares a high-transmittance intelligent liquid crystal dimming film, which adopts a method of wrapping a layer of polymer dispersed liquid crystal material (PDLC) with two layers of flexible transparent conductive film (ITO film). Compared with the traditional liquid crystal dimming film, the intelligent liquid crystal dimming film obtained by the present invention can significantly improve the transmittance under different power-on voltages.

[0020] 2. The polymer dispersed liquid crystal material can be transformed into two states, transparent and scattering, under the condition of electricity. The materials that affect its optical properties are mainly liquid crystal materials and monomer materials. The present invention adjusts and tests the monomer materials therein, and finds that when certain liquid crystal materials (especially liquid crystal material E7) are used, the monomer materials are N-vinyl caprolactam, hexafluorobutyl acrylate, methyl allyl diethoxy silane, 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.

[0021] 3. The monomer materials used in the preparation of polymer dispersed liquid crystal materials of the present invention firstly select acrylic monomers (hexafluorobutyl acrylate) with better stability and temperature resistance, and secondly select vinyl monomers (N-vinyl caprolactam) and allyl silanes (methylallyl diethoxysilane) with better hardness and flexibility. In addition, a polymer containing vinyl (vinyl polyimide) is uniquely added as a monomer. After use, it was found that under the conditions of the same liquid crystal material, the polymer dispersed liquid crystal material prepared according to the ratio of the present invention has better transparency in PDLC. DETAILED DESCRIPTION

[0022] 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 existence 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 limit the scope of the present invention. The change or adjustment of the relative relationship thereof shall also be regarded as the scope of the present invention without substantially changing the technical content.

[0023] In order to better understand the above technical scheme, the 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 in order to enable a more thorough understanding of the present invention and to enable the scope of the present invention to be fully communicated to those skilled in the art.

[0024] The present invention will be further described below in conjunction with the following examples.

[0025] Example 1

[0026] A method for preparing a high-transmittance intelligent liquid crystal dimming film, comprising: Step 1, taking the components of the polymer dispersed liquid crystal material according to the weight ratio, the polymer dispersed liquid crystal material, calculated by weight, 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; 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, and keep the coating process uniform; 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; 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 15μm.

[0027] 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: the mass ratio of N-vinyl caprolactam, hexafluorobutyl acrylate, methyl allyl diethoxysilane, and vinyl polyimide is 2.5:6.7:1.2:2.4; the photoinitiator is benzoin dimethyl ether; and the solvent is ethyl acetate.

[0028] Wherein, the preparation method of vinyl polyimide comprises: S1. Under ice-water bath conditions, 0.24 g of 1,4-bis(2,4-diaminophenoxy)benzene was first dissolved in 45 mL of N,N-dimethylformamide, and then 0.2 g of maleic anhydride was added. After stirring for 0.5 h under ice-water bath conditions, the mixture was heated to room temperature and stirred for 1.5 h to obtain a first mixed solution. S2, placing the first mixed solution in an ice-water bath again, adding 2 g of 4,4'-diaminodiphenyl ether and 1.9 g of 4,4'-diaminobiphenyl in sequence, stirring to fully dissolve, then adding 6.7 g of pyromellitic anhydride, stirring in an ice-water bath for 3 h, to obtain a second mixed solution; 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, after the reaction is completed, cool to room temperature, collect the solid by centrifugation, wash and dry to obtain vinyl polyimide.

[0029] Example 2

[0030] A method for preparing a high-transmittance intelligent liquid crystal dimming film, comprising: Step 1, taking the components of the polymer dispersed liquid crystal material in proportion by weight, and evenly 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, calculated by weight, includes: 32 parts of liquid crystal material, 15 parts of monomer material, 0.1 parts of photoinitiator and 2 parts of solvent; 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, and keep the coating process uniform; 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; Step 4: Curing is performed by ultraviolet light treatment. The treatment time is 1 min, the wavelength of ultraviolet light is 365 nm, and the light intensity is 45 mW / cm 2 ‌, the thickness of the obtained polymer dispersed liquid crystal material layer is 10μm.

[0031] Among them, the liquid crystal material is the liquid crystal material TEB30, and the parameters of the liquid crystal material TEB30 are: contrast ratio is 9.7, maximum transmittance is 85.2%, minimum transmittance is 8.7%, and opening voltage is 3.6V; the monomer material is N-vinyl caprolactam, hexafluorobutyl acrylate, methyl allyl 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. In addition, the preparation method of vinyl polyimide is the same as that in Example 1.

[0032] Example 3

[0033] A method for preparing a high-transmittance intelligent liquid crystal dimming film, comprising: Step 1, taking each component of the polymer dispersed liquid crystal material according to the weight ratio, and evenly 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, calculated by weight, includes: 64 parts of liquid crystal material, 45 parts of monomer material, 1 part of photoinitiator and 10 parts of solvent; 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, and keep the coating process uniform; 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; 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 20μm.

[0034] The liquid crystal material is TEB50, and the parameters of the liquid crystal material TEB50 are: contrast ratio of 7.7, maximum transmittance of 80.1%, minimum transmittance of 10.35%, and opening voltage of 3.2V; the monomer materials are N-vinyl caprolactam, hexafluorobutyl acrylate, methyl allyl 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. In addition, the preparation method of vinyl polyimide is the same as that in Example 1.

[0035] Example 4

[0036] A method for preparing a high-transmittance intelligent liquid crystal dimming film, comprising: Step 1, taking each component of the polymer dispersed liquid crystal material according to the weight ratio, and evenly 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, calculated by weight, includes: 58 parts of liquid crystal material E7, 35 parts of monomer material, 0.4 parts of photoinitiator and 7 parts of solvent; 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, and keep the coating process uniform; 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; 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 10μm.

[0037] The liquid crystal material is liquid crystal material E7, and the parameters of liquid crystal material E7 are: contrast ratio is 53.9, maximum transmittance is 90.3%, minimum transmittance is 1.62%, and opening voltage is 1.2V; the monomer material includes: N-vinyl caprolactam, 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. In addition, the preparation method of vinyl polyimide is the same as that of Example 1.

[0038] Comparative Example 1 A high-transmittance intelligent liquid crystal dimming film, the preparation method of which is different from that of Example 1 only in that, in the composition of the polymer dispersed liquid crystal material layer, the monomer material includes: N-vinyl caprolactam, hexafluorobutyl acrylate, and methyl allyl diethoxy silane in a mass ratio of 3.3:7.5:2.

[0039] Comparative Example 2 A high-transmittance intelligent liquid crystal dimming film, the preparation method of which is different from that of Example 1 only in that, in the composition of the polymer dispersed liquid crystal material layer, the monomer material includes: hexafluorobutyl acrylate, methyl allyl diethoxysilane, and vinyl polyimide in a mass ratio of 3.3:7.5:2.

[0040] Comparative Example 3 A high-transmittance intelligent liquid crystal dimming film, the preparation method of which is different from that of Example 1 only in that, in the composition of the polymer dispersed liquid crystal material layer, the monomer materials include: N-vinyl caprolactam, methyl allyl diethoxy silane, and vinyl polyimide in a mass ratio of 3.3:7.5:2.

[0041] Comparative Example 4 A high-transmittance intelligent liquid crystal dimming film, the preparation method of which is different from that of Example 1 only in that, in the composition of the polymer dispersed liquid crystal material layer, the monomer material includes: N-vinyl caprolactam, hexafluorobutyl acrylate, and vinyl polyimide in a mass ratio of 3.3:7.5:2.

[0042] The transmittance of the intelligent liquid crystal dimming films prepared in Example 1 and Comparative Examples 1-4 was tested, wherein the testing temperature was 25±2°C, the humidity was 55±5RH%, and the testing equipment was an HT-15A optical transmittance tester. The test results are shown in Table 1: Table 1 Transmittance performance of dimming film under different voltage conditions

[0043] It can be seen from the test results in Table 1 that the performance of the polymer dispersed liquid crystal material layer obtained from different monomer components is significantly different. The smart liquid crystal dimming film prepared in Example 1 of the present invention can achieve a transmittance of 86.7% under 60V power supply, and a transmittance of 89.2% under 110V power supply, which is significantly better than other comparative examples, indicating that the smart liquid crystal dimming film prepared in Example 1 of the present invention can have a relatively significant improvement in transmittance under different power supply voltages. The data of comparative example 1 is significantly worse than those of comparative examples 2-4, indicating that the influence of vinyl polyimide in the monomer material is significantly higher than that of other components.

[0044] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. 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 being directed to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine different embodiments or examples described in this specification.

[0045] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary 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 parts of photoinitiator and 2-10 parts of solvent; The monomer material is a mixture of N-vinyl caprolactam, hexafluorobutyl acrylate, methyl allyl diethoxy silane and vinyl polyimide.

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 mass ratio of N-vinyl caprolactam, hexafluorobutyl acrylate, methyl allyl diethoxysilane and vinyl polyimide is 1.4-3.6:2.1-8.4:0.8-1.6:1.2-3.

6.

5. 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-trimethylbenzoyl diphenyl phosphine oxide, and phenyl bis (2,4,6-trimethylbenzoyl) phosphine oxide.

6. 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.

7. 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 according to the weight ratio, and evenly 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, and keep the coating process uniform; 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 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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