Graphene-based liquid crystal material, preparation method and dimming film or dimming glass containing graphene-based liquid crystal material

Abstract

The invention discloses a graphene-based liquid crystal material, a preparation method and a dimming film or dimming glass containing the graphene-based liquid crystal material. The graphene-based liquid crystal material comprises the following raw materials: a graphene oxide sheet (belt) or a reduced graphene oxide belt, a liquid crystal material or a mixture of the liquid crystal material and photocuring glue, the graphene oxide sheets or reduced graphene oxide sheets (bands) are added into the liquid crystal material, so that the arrangement of liquid crystal molecules is not disturbed under the action of an electric field; when liquid crystal molecules and incident light rays are arranged in parallel, the long axis direction of the liquid crystal molecules is parallel to the long axis direction of the liquid crystal molecules, so that the light rays pass through the liquid crystal molecules; when the graphene oxide sheets or the reduced graphene oxide sheets (belts) are arranged along with liquid crystal molecules perpendicular to incident light, the graphene oxide sheets or the reduced graphene oxide sheets (belts) strongly absorb light to prevent the light from passing through; in addition, the liquid crystal compound has certain conductivity, can effectively reduce the driving threshold, can significantly enhance the dimming contrast of guest-host liquid crystal materials, and reduces the threshold voltage.

Description

Technical Field

[0001] The present application relates to the technical field of liquid crystal materials, and in particular to a graphene-based liquid crystal material, a preparation method, and a dimming film or dimming glass containing the same (or referred to as a dimming product containing the same). Background Art

[0002] As people's living standards continue to improve, they have higher and higher requirements for privacy, comfort, and intelligence. Smart dimming film / glass can change the way light passes through and the transmittance by applying different voltages. Therefore, it is used in building curtain walls, indoor partitions, outdoor ceilings, automotive industry, rail transportation, aerospace and other fields, bringing people a good experience.

[0003] Both guest-host dye liquid crystal (GH LC) technology and polymer dispersed (guest-host dye) liquid crystal (PD(GH)LC) dimming technology belong to guest-host liquid crystal dimming technology, which has the advantages of long electrical aging life, moderate driving voltage, adjustable color, and stepless dimming, but the dimming range needs to be improved. The dimming ability of the guest-host liquid crystal dimming film is determined by the order parameter of the liquid crystal on the one hand, and the order parameter, addition amount and solubility of the dichroic dye on the other hand. With the increase of dyes, it will also cause problems such as increased power consumption and increased voltage. The bottleneck problem of the dimming ability of the guest-host liquid crystal dimming film has not been solved. Summary of the invention

[0004] In view of the above-mentioned deficiencies in the prior art, the present application provides a graphene-based liquid crystal material that can significantly enhance the dimming contrast of guest-host liquid crystal materials and reduce the threshold voltage.

[0005] In order to solve the above technical problems, the technical solution adopted in this application is: a graphene-based liquid crystal material, the raw materials of which include: graphene oxide sheets (ribbons) or reduced graphene oxide ribbons, liquid crystal materials or a mixture of liquid crystal materials and photocurable glue.

[0006] Furthermore, the raw material may also contain a dichroic dye.

[0007] Furthermore, the dichroic dye is selected from any one or more of azo dichroic dyes, anthraquinone dichroic dyes, PDI dichroic dyes, and the like.

[0008] Furthermore, the dichroic dye is selected from one or more of azo dichroic dyes and anthraquinone dichroic dyes.

[0009] Furthermore, the content of the dichroic dye in the graphene-based liquid crystal material is 0.1% to 20wt%.

[0010] Furthermore, the content of the dichroic dye in the graphene-based liquid crystal material is 0.1 to 15 wt %.

[0011] Furthermore, the content of the dichroic dye in the graphene-based liquid crystal material is 1% to 10wt%.

[0012] Furthermore, the graphene oxide sheet (ribbon) or reduced graphene oxide ribbon is a single-layer, double-layer or triple-layer structure, preferably a single-layer structure.

[0013] Furthermore, the length of the graphene oxide sheet (ribbon) or the reduced graphene oxide ribbon is 0.5nm to 100nm, and the width is 0.5nm to 100nm.

[0014] Furthermore, the length of the graphene oxide sheet (ribbon) or the reduced graphene oxide ribbon is 1.0 nm to 20 nm, and the length is 0.5 nm to 20 nm.

[0015] Furthermore, the content of the graphene oxide sheet (ribbon) or reduced graphene oxide ribbon in the graphene-based liquid crystal material is 0.1% to 10wt%.

[0016] Furthermore, the content of the graphene oxide sheet (ribbon) or reduced graphene oxide ribbon in the graphene-based liquid crystal material is 0.1% to 5wt%.

[0017] Furthermore, the liquid crystal material is selected from any type of positive nematic mixed crystal, negative nematic mixed crystal, cholesteric mixed crystal, smectic mixed crystal or a mixture of the above mixed crystals and photocurable glue.

[0018] Furthermore, when the liquid crystal material is selected from negative nematic mixed crystals or smectic mixed crystals, it may further include one or more ionic compounds (such as tetrabutylammonium bromide).

[0019] Furthermore, the liquid crystal material or the mixture of the liquid crystal material and the photocurable glue accounts for 80% to 99.9wt% of the graphene-based liquid crystal material.

[0020] Furthermore, the photocurable glue can be a mixture of a photocurable resin, a photocurable monomer and a photoinitiator, and is mixed uniformly at a temperature of 5 to 50°C.

[0021] Furthermore, the photocurable glue accounts for 0 to 50% of the total amount of the graphene-based liquid crystal material.

[0022] Furthermore, the photocurable resin is selected from one or more of acrylate photocurable resin, epoxy acrylate photocurable resin, and polyurethane acrylate resin, and the unsaturation degree is selected from 1.5 to 3.5.

[0023] Furthermore, the photocurable monomers are selected from at least two of monofunctional, difunctional and trifunctional acrylic monomers.

[0024] Furthermore, the photoinitiator is selected from one or more of BDK (equivalent to 651), DEAP, TPO, 369, 907, 819, 184, BP, OMBB, EMK, TETX, 1173, 907, ITX, EHA, OXE-02, OXE-03, OXE-04, OXE-05, BMS, and PTX, preferably two or more.

[0025] Furthermore, the photocurable resin accounts for 5.0% to 50.0% of the total amount of the photocurable glue, the photocurable monomer accounts for 49.9% to 94.9% of the total amount of the photocurable glue, and the photoinitiator accounts for 0.1% to 15% of the total amount of the photocurable glue (the sum of the above three components is 100%).

[0026] The present application also provides a method for preparing a graphene-based liquid crystal material (graphene-based dimming material), the preparation steps comprising:

[0027] (1) weighing a liquid crystal material or a mixture of a liquid crystal material and a photocurable glue and a dichroic dye into a container according to a formula, mixing them evenly at a certain temperature, and then returning them to room temperature for use;

[0028] (2) adding graphene oxide sheets (ribbons) or reduced graphene oxide sheets (ribbons) to the mixture obtained in the above step (1), and mixing them uniformly at a certain temperature;

[0029] (3) The graphene-based dimming material obtained above is filled with nitrogen, sealed, and set aside.

[0030] Furthermore, the mixing temperature of step (1) is room temperature (about 25°C) to 140°C; the mixing temperature of step (1) is preferably room temperature to 70°C.

[0031] Furthermore, the mixing is carried out by at least one of the following methods: magnetic stirring, mechanical stirring, ultrasound, oscillation, rotation + revolution, etc.

[0032] The present application also provides a dimming film or dimming glass, which includes: a first transparent substrate / glass, a first transparent conductive layer formed on the first transparent substrate / glass; a second transparent substrate / glass, a second transparent conductive layer formed on the second transparent substrate / glass, the first transparent conductive layer and the second transparent conductive layer are arranged opposite to each other, and a graphene-based dimming material (the graphene-based dimming material here is the graphene-based liquid crystal material prepared as described above in the present application) filled between the first transparent conductive layer and the second transparent conductive layer.

[0033] Furthermore, the transparent conductive layer is selected from one of ITO conductive film, silver conductive film, carbon material conductive film and composite conductive film thereof.

[0034] Furthermore, the graphene-based dimming material (the graphene-based dimming material here is the graphene-based liquid crystal material prepared above) is at least one of graphene oxide / reduced graphene oxide sheet-liquid crystal, graphene oxide / reduced graphene oxide sheet-dye liquid crystal, graphene oxide / reduced graphene oxide sheet-liquid crystal-glue composite material, and graphene oxide / reduced graphene oxide sheet-dye liquid crystal-glue composite material.

[0035] Furthermore, the liquid crystal in the graphene-based dimming material is selected from any one of positive nematic liquid crystal, negative nematic liquid crystal, cholesteric liquid crystal and smectic liquid crystal.

[0036] Furthermore, the graphene-based dimming material (graphene-based liquid crystal material) is filled between two transparent conductive films / glasses by vacuum infusion, drip roller coating, and slit coating roller composite method.

[0037] The graphene oxide sheet (ribbon) described in the present application may be a graphene oxide sheet or a graphene oxide ribbon.

[0038] Advantages and beneficial effects of this application:

[0039] 1. The present application adds graphene oxide sheets (ribbons) or reduced graphene oxide ribbons (sheets) of specific combinations and specifications to liquid crystal materials. Since single-layer graphene oxide sheets (ribbons) or reduced graphene oxide ribbons (sheets) are two-dimensional carbon materials containing oxygen-containing functional groups, they have very high resistance compared to graphene. This is because graphene oxide or reduced graphene oxide has a large number of sp3 hybridized carbon atoms combined with oxygen-containing groups. Under the action of an electric field, the graphene oxide sheets or reduced graphene oxide sheets will not rotate autonomously. Therefore, when the graphene oxide sheets or reduced graphene oxide sheets (ribbons) are added to the liquid crystal material, the liquid crystal separation will not be disturbed under the action of an electric field. On the contrary, due to its rod-like structure and insulation, it will deflect with the deflection of the liquid crystal. When the liquid crystal molecules are arranged parallel to the incident light, its long axis direction is parallel to the long axis direction of the liquid crystal molecules, allowing the light to pass through; when it is arranged perpendicular to the incident light with the liquid crystal molecules, the graphene oxide sheet or reduced graphene oxide sheet (belt) strongly absorbs light and prevents the light from passing through; in addition, its electrical properties are also very unique, with a certain conductivity (not enough to cause deflection under the electric field), which effectively reduces the driving threshold; therefore, adding graphene oxide sheets (belts) or reduced graphene oxide ribbons (sheets) can significantly enhance the dimming contrast of the guest-host liquid crystal material and reduce the threshold voltage.

[0040] 2. The size, type and content of graphene oxide sheets or reduced graphene oxide sheets (ribbons) have a great influence on the response speed of liquid crystal molecules under an electric field, the dispersion and stability in the liquid crystal material; the present application effectively improves the orderliness and threshold voltage of graphene-based dimming materials by selecting specific graphene sheet (ribbon) specifications, and the dimming device made therefrom has a higher dimming contrast and a lower threshold voltage. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 A schematic structural diagram of a cross-sectional view in the thickness direction of the dimming film or dimming glass of the present application.

[0042] As shown in the accompanying drawings: 1. first transparent substrate / glass, 2. first transparent conductive layer, 3. second transparent substrate / glass, 4. second transparent conductive layer, 5. graphene-based dimming material. DETAILED DESCRIPTION

[0043] The following will combine the embodiments and drawings to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only preferred embodiments, not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention;

[0044] It should also be noted that when a component is referred to as being "fixed to" (and other similar ways of "fixed to") another component, it may be directly on the other component or there may be another intermediate component, fixed through the intermediate component. When a component is considered to be "connected to" (and other similar ways of "connected to") another component, it may be directly connected to the other component or there may be another intermediate component at the same time. When a component is considered to be "set on" (and other similar ways of "set on") another component, it may be directly set on the other component or there may be another intermediate component at the same time. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for illustrative purposes only. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by technicians in the technical field of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0045] As attached Figure 1As shown, a dimming film or dimming glass of the present application, the structure of which includes: a first transparent substrate / glass 1, a first transparent conductive layer 2 formed on the first transparent substrate / glass 1; a second transparent substrate / glass 3, a second transparent conductive layer 4 formed on the second transparent substrate 3, the first transparent conductive layer 2 and the second transparent conductive layer 4 are arranged opposite to each other, and the graphene-based dimming material 5 filled between the first transparent conductive layer 2 and the second transparent conductive layer 4 is the graphene-based liquid crystal material prepared in the present application.

[0046] Specifically, the graphene-based dimming material 5 can be prepared by the following specific embodiments, and the sum of the various components of the formula raw materials of the embodiments is 100%:

[0047] Example 1

[0048] Preparation method: Add the materials in Table 1 below, BASF dye X13, and graphene sheet powder to the mixed crystal E7, stir at 50°C for 1 hour, then ultrasonicate for 1 hour, and cool to room temperature for use. Place the liquid crystal box with an antiparallel orientation of the PI layer on a hot table and set the temperature to 70°C. Add the mixed dye liquid crystal droplets to the reserved crystal filling port, and use the siphon effect to pour the liquid crystal into the liquid crystal box. Stack the two prepared samples in the direction of PI orientation, and use a haze meter (Sanenshi YH1600) to test the transmittance when powered on (driving waveform: 50HZ20V) and not powered on. Dimming contrast = power-on transmittance / power-off transmittance; as shown in Table 1 below:

[0049] Table 1 Graphene-nematic dye liquid crystal H004

[0050]

[0051] Example 2

[0052] Preparation method: Stir the materials in Table 2 below at 120°C for 2 hours and then cool to room temperature. Place the non-oriented liquid crystal box on a hot plate and set the temperature to 120°C. Add the mixed materials to the reserved crystal filling port and use the siphon effect to pour the liquid crystal into the liquid crystal box. Cool the prepared samples to room temperature and use a haze meter (Sanens YH1600) to test the transmittance in the transparent state (driving waveform: 80V2kHZ, 25) and the frosted state (driving waveform: 80V50HZ, 1s). Dimming contrast = power-on transmittance / power-off transmittance; refer to Table 2 below for details:

[0053] Table 2 Graphene-smectic liquid crystal formula H005

[0054]

[0055] Note: 1-7 in Table 2 above are liquid crystals, and 8 is an ammonium ion compound.

[0056] Example 3

[0057] Preparation method: According to the components in Table 3 below, the materials other than the photoinitiator 651 are weighed into the container in proportion, and stirred and mixed at 40°C for 20 minutes, and then added to the homogenizer for dispersion for 30 minutes. Finally, add the initiator to the homogenized material and stir and mix at room temperature for 10 minutes for standby use. Add the material dropwise between the two conductive films, roll and coat evenly, and then cure it under a 365nm ultraviolet lamp (P = 10mw / cm2) for 5 minutes. Use a haze meter (Sanenshi YH1600) to test the transmittance when powered on (driving waveform: 50HZ36V) and not powered on. Dimming contrast = power-on transmittance / power-off transmittance; refer to the following Table 3 for details:

[0058] Table 3 Graphene-glue-dye liquid crystal composite material H003

[0059]

[0060] Note: Dye liquid crystal X6A-5027BK6601 was purchased from Yantai Xianhua; resin PU5179 was purchased from Dongguan Fengjin New Materials Co., Ltd.

[0061] Comparative Example 1:

[0062] Preparation method: Add 0.05g of BASF dye X13 to 4.95g of mixed crystal E7, stir at 50℃ for 1 hour and then cool to room temperature. Place the liquid crystal box with the PI layer having an antiparallel orientation on a hot stage and set the temperature to 70℃. Add the mixed dye liquid crystal dropwise to the reserved crystal filling port and use the siphon effect to pour the liquid crystal into the liquid crystal box. Stack the two prepared samples in the direction of PI orientation, and use a haze meter (Sanenshi YH1600) to test the transmittance when powered on (driving waveform: 50HZ10V) and not powered on. Dimming contrast = power-on transmittance / power-off transmittance; see Table 4 below for details:

[0063] Table 4 Nematic dye liquid crystal H001

[0064]

[0065] Comparative Example 2:

[0066] Preparation method: Stir the materials in Table 5 below at 120°C for 2 hours and then cool to room temperature. Place the non-oriented liquid crystal box on a hot plate and set the temperature to 120°C. Add the mixed dye liquid crystal to the reserved crystal filling port and use the siphon effect to pour the liquid crystal into the liquid crystal box. Cool the prepared sample to room temperature and use a haze meter (Sanens YH1600) to test the transmittance in the transparent state (driving waveform: 80V2kHZ, 25) and the frosted state (driving waveform: 80V50HZ, 1s). Dimming contrast = power-on transmittance / power-off transmittance; refer to the following Table 5 for details:

[0067] Table 5 Smectic liquid crystal formula H002

[0068]

[0069] Comparative Example 3

[0070] Preparation method: weigh the materials in Table 6 below into a container according to the proportion, and stir and mix them evenly at room temperature. Then drop the materials between the two conductive films, roll and coat them evenly, and then cure them under a 365nm ultraviolet lamp (P = 10mw / cm2) for 5 minutes. Use a haze meter (Sanens YH1600) to test the transmittance when powered on (driving waveform: 50HZ48V) and when not powered on. Dimming contrast = power-on transmittance / power-off transmittance; refer to the following Table 6 for details:

[0071] Table 6 Glue-dye liquid crystal composite material H003

[0072]

[0073] Note: Dye liquid crystal X6A-5027BK6601 was purchased from Yantai Xianhua; resin PU5179 was purchased from Dongguan Fengjin New Materials Co., Ltd.

[0074] It can be seen from the test results of the above embodiments and comparative examples that the present application uses graphene oxide sheets (ribbons) or reduced graphene oxide ribbons of specific specifications, which can significantly enhance the dimming contrast of the guest-host liquid crystal material and reduce the threshold voltage.

Claims

1. A graphene-based liquid crystal material, characterized in that: The raw materials of the material include: graphene oxide sheets (ribbons) or reduced graphene oxide ribbons, liquid crystal materials or a mixture of liquid crystal materials and photocurable glue.

2. The graphene-based liquid crystal material according to claim 1, characterized in that: The raw materials also contain a dichroic dye.

3. The graphene-based liquid crystal material according to claim 2, characterized in that: The dichroic dye is selected from any one or more of azo dichroic dyes, anthraquinone dichroic dyes, and PDI dichroic dyes; the content of the dichroic dye in the graphene-based liquid crystal material is 0.1% to 20wt%.

4. The graphene-based liquid crystal material according to claim 3, characterized in that: The dichroic dye is selected from one or more of azo dichroic dyes and anthraquinone dichroic dyes, and the content of the dichroic dye in the graphene-based liquid crystal material is 0.1-15wt%.

5. The graphene-based liquid crystal material according to claim 4, characterized in that: The content of the dichroic dye in the graphene-based liquid crystal material is 1% to 10wt%.

6. The graphene-based liquid crystal material according to claim 1, characterized in that: The graphene oxide sheet (ribbon) or reduced graphene oxide ribbon is a single-layer, double-layer or triple-layer structure; the content of the graphene oxide sheet (ribbon) or reduced graphene oxide ribbon in the graphene-based liquid crystal material is 0.1% to 10wt%.

7. The graphene-based liquid crystal material according to claim 6, characterized in that: The length of the graphene oxide sheet (ribbon) or the reduced graphene oxide ribbon is 0.5nm-100nm, and the width is 0.5nm-100nm.

8. The graphene-based liquid crystal material according to claim 7, characterized in that: The length of the graphene oxide sheet (ribbon) or the reduced graphene oxide ribbon is 1.0nm to 20nm, and the length is 0.5nm to 20nm; the content of the graphene oxide sheet (ribbon) or the reduced graphene oxide ribbon in the graphene-based liquid crystal material is 0.1% to 5wt%.

9. The graphene-based liquid crystal material according to claim 1, characterized in that: The liquid crystal material is selected from any type of positive nematic phase mixed crystal, negative nematic phase mixed crystal, cholesteric phase mixed crystal, smectic phase mixed crystal or a mixture of the above mixed crystals and photocurable glue; the liquid crystal material or the mixture of liquid crystal material and photocurable glue accounts for 80% to 99.9wt% of the graphene-based liquid crystal material.

10. The graphene-based liquid crystal material according to claim 9, characterized in that: When the liquid crystal material is selected from negative nematic mixed crystals or smectic mixed crystals, it further includes one or more ionic compounds.

11. The method for preparing a graphene-based liquid crystal material according to claim 1, characterized in that: The photocurable glue is a mixture of photocurable resin, photocurable monomer and photoinitiator, and is evenly mixed at a temperature of 5 to 50° C.; the photocurable glue accounts for 0 to 50% of the total amount of graphene-based liquid crystal material.

12. The method for preparing a graphene-based liquid crystal material according to claim 11, characterized in that: The photocurable resin is selected from one or more of acrylate photocurable resins, epoxy acrylate photocurable resins, and polyurethane acrylic resins, and the degree of unsaturation is selected from 1.5 to 3.5; the photocurable monomer is selected from at least two of monofunctional, difunctional, and trifunctional acrylic monomers; the photoinitiator is selected from one or more of BDK, DEAP, TPO, 369, 907, 819, 184, BP, OMBB, EMK, TETX, 1173, 907, ITX, EHA, OXE-02, OXE-03, OXE-04, OXE-05, BMS, and PTX; The photocurable resin accounts for 5.0% to 50.0% of the total amount of the photocurable glue, the photocurable monomer accounts for 49.9% to 94.9% of the total amount of the photocurable glue, and the photoinitiator accounts for 0.1% to 15% of the total amount of the photocurable glue.

13. A method for preparing a graphene-based liquid crystal material according to any one of claims 1 to 12, characterized in that: The preparation steps include: (1) weighing a liquid crystal material or a mixture of a liquid crystal material and a photocurable glue and a dichroic dye into a container according to a formula, mixing them evenly at a certain temperature, and then returning them to room temperature for use; (2) adding graphene oxide sheets (ribbons) or reduced graphene oxide sheets (ribbons) to the mixture obtained in the above step (1), and mixing them uniformly at a certain temperature; (3) The graphene-based dimming material obtained above is filled with nitrogen, sealed, and set aside.

14. The method for preparing a graphene-based liquid crystal material according to claim 13, characterized in that: The mixing temperature in step (1) is room temperature to 140° C.; the mixing is carried out by at least one of magnetic stirring, mechanical stirring, ultrasound, oscillation, rotation + revolution and the like.

15. A dimming film or dimming glass, characterized in that: Its structure includes: a first transparent substrate / glass, a first transparent conductive layer formed on the first transparent substrate / glass; a second transparent substrate / glass, a second transparent conductive layer formed on the second transparent substrate / glass, the first transparent conductive layer and the second transparent conductive layer are arranged opposite to each other, and the graphene-based liquid crystal material according to any one of claims 1 to 10 is filled between the first transparent conductive layer and the second transparent conductive layer.

16. The dimming film or dimming glass according to claim 15, characterized in that: The transparent conductive layer is selected from one of ITO conductive film, silver conductive film, carbon material conductive film and composite conductive film thereof; the graphene-based liquid crystal material is at least one of graphene oxide / reduced graphene oxide sheet-liquid crystal, graphene oxide / reduced graphene oxide sheet-dye liquid crystal, graphene oxide / reduced graphene oxide sheet-liquid crystal-glue composite material, and graphene oxide / reduced graphene oxide sheet-dye liquid crystal-glue composite material; the liquid crystal is selected from any one of positive nematic phase liquid crystal, negative nematic phase liquid crystal, cholesteric phase liquid crystal and smectic phase liquid crystal; the graphene-based liquid crystal material is filled between two transparent conductive films / glasses by one of vacuum infusion, drip roller coating and slit coating roller composite.

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