Multiple stimuli response trans-electro-control liquid crystal light regulating film, preparation method and application thereof

Abstract

The application provides a multiple stimulus response transverse electric control liquid crystal dimming film and a preparation method and application, and belongs to the technical field of liquid crystal materials.The dimming film is composed of a first substrate layer, a first conductive layer, a first vertical alignment layer, a dye-doped thiol-epoxy liquid crystal polymer composite functional material layer, a second vertical alignment layer, a second conductive layer and a second substrate layer which are sequentially stacked along the thickness direction.Meanwhile, the dimming film can form multiple optical states such as a transparent state without electricity, a low-frequency electric field absorption state, a high-frequency electric field color state and a high-temperature absorption enhancement state, and has good light-on state transmittance, low driving voltage, low threshold voltage and high substrate peeling strength, so that the application solves the problems that the existing polymer stabilized liquid crystal transverse electric control dimming film is difficult to simultaneously realize low driving voltage and high peeling strength, and the function is single and cannot simultaneously have active electric field control and passive external temperature response dimming.

Description

Technical Field

[0001] This invention relates to the field of liquid crystal materials technology, and in particular to a multi-stimulus responsive inverse electro-controlled liquid crystal dimming film, its preparation method, and its application. Background Technology

[0002] Globally, approximately 40% of energy consumption comes from buildings. Driven by current development concepts, green and energy-efficient buildings have become an inevitable trend for environmental protection and market development. Windows, as the main channel for heat exchange between the interior and exterior environments of a building, are the weakest link in the building envelope's thermal insulation performance and a key area for energy loss, directly leading to low overall building energy efficiency. Smart windows can actively or passively regulate solar radiation and visible light intake, offering significant advantages in reducing building energy consumption and improving human comfort, demonstrating broad application prospects in the field of green building.

[0003] Among numerous smart window technologies, dimming devices based on liquid crystal-polymer composite materials have become a key research and application area in the industry due to their unique ability to achieve stimulus-responsive reversible switching between transparent and opaque states. Among these, inverse electro-electric dimming films based on polymer stabilized liquid crystal (PSLC) systems represent a typical technological approach in this field. However, they face significant technical challenges in practical applications: Firstly, existing PSLC inverse electro-electric dimming films cannot simultaneously achieve both low driving voltage and high peel strength, making it difficult to synergistically optimize the device's electro-control performance and mechanical stability, thus affecting product lifespan and large-scale application. Secondly, current PSLC dimming films have limited functionality, only capable of single-mode light transmittance control, and cannot simultaneously possess the ability to control both active electric fields and passive external temperature responses. This makes it difficult to meet the demands of green buildings for efficient energy saving and flexible control of smart windows, thus limiting the further development and application of liquid crystal-based smart dimming window technology. Summary of the Invention

[0004] In order to overcome the shortcomings of the prior art, the purpose of this invention is to provide a multi-stimulus responsive inverse electro-controlled liquid crystal dimming film, its preparation method and application, which aims to solve the technical problems of existing polymer stabilized liquid crystal (PSLC) inverse electro-controlled dimming films, which are difficult to achieve low driving voltage and high peel strength at the same time, and have a single function that cannot simultaneously possess active electric field control and passive external temperature response dimming.

[0005] To achieve the above objectives, the present invention provides the following solution: On one hand, the present invention provides a multi-stimulus responsive inverse electro-controlled liquid crystal dimming film, comprising a first substrate layer, a first conductive layer, a first vertical alignment layer, a dye-doped thiol-epoxy liquid crystal polymer composite functional material layer, a second vertical alignment layer, a second conductive layer, and a second substrate layer stacked sequentially along the thickness direction. The raw materials for the thiol-epoxy liquid crystal polymer composite functional material layer include epoxy monomers, thiol monomers, dichroic dyes, liquid crystal materials, and curing agents. The raw materials for both the first vertical orientation layer and the second vertical orientation layer include a vertical orientation agent and an interfacial crosslinking agent.

[0006] Preferably, the total thickness of the thiol-epoxy liquid crystal polymer composite functional material layer, the first vertical alignment layer, and the second vertical alignment layer is 1~80μm, and its raw materials include, by weight: 40~99.9 parts of liquid crystal material, 0.01~40 parts of epoxy monomer, 0.01~40 parts of thiol monomer, 0.01~10 parts of curing agent, and 0.01~10 parts of dichroic dye; The raw materials for the first vertical orientation layer and the second vertical orientation layer are, by weight, 0-10 parts of vertical orientation agent and 0-10 parts of interfacial crosslinking agent.

[0007] Preferably, the liquid crystal material is a negative liquid crystal; the epoxy monomer is at least one of aromatic ester type, biphenyl type, α-methylstyrene type, naphthalene type, azo type, and monofunctional type; the thiol monomer is one or more of bis(3-mercaptopropionic acid) ethylene glycol, 4-mercaptomethyl-3,6-dithia-1,8-octanedithiol, 1,3-benzenedithiol, p-terphenyl-4,4-dithiol, 1,4-benzenedithiol, 1,3,5-benzotrithiol, propane-1,2,3-trithiol, 2,4,6-trimercapto-1,3,5-triazine trimethylolpropane tris(3-mercaptopropionate), pentaerythritol tetra(3-mercaptopropionate), or dipentaerythritol hexaalkyl(3-mercaptopropionate).

[0008] Preferably, the curing agent is an amine curing agent, which is one or more of ethylenediamine, diethylenetriamine, imidazoline, 2,4,6-tris(dimethylaminomethyl)phenol, triethylamine, benzyldimethylamine, and N-methylmorpholine; the dichroic dye is an azo or anthraquinone; the vertical orientation agent is one or more of PI or DMOAP; and the interfacial crosslinking agent is a compounding agent for enhancing interlayer bonding, specifically one or more of epoxy silane, acrylate silane, thiol silane, or amino silane.

[0009] Preferably, the first substrate layer and the second substrate layer are each independently selected from glass, polyethylene terephthalate, polyethylene naphthalate, polycarbonate or polymethyl methacrylate; the first conductive layer and the second conductive layer are each independently selected from ITO or FTO.

[0010] Preferably, the dimming film has three electrically controlled operating modes: a transparent state without electricity, an absorption state under a low-frequency electric field, and a color state under a high-frequency electric field, and the thermochromic temperature of the dimming film is 20~150℃.

[0011] On the other hand, the present invention also provides a method for preparing the above-mentioned multi-stimulus responsive inverse electro-controlled liquid crystal dimming film, comprising: mixing epoxy monomer, thiol monomer, dichroic dye, liquid crystal material, curing agent, vertical alignment agent and interfacial crosslinking agent in a uniform ratio, adding the mixture between the first conductive layer and the second conductive layer, and performing thermally initiated ring-opening polymerization to obtain the multi-stimulus responsive inverse electro-controlled liquid crystal dimming film.

[0012] Preferably, the curing temperature of the thermally initiated ring-opening polymerization is 40~120℃, and the curing time is 0.1~12h.

[0013] Preferably, after the thermally initiated ring-opening polymerization, the process further includes: placing a photomask on the obtained multi-stimulus responsive inverse electro-hydraulic liquid crystal dimming film, and then curing it with ultraviolet light to obtain a patterned device; wherein the ultraviolet curing time is 10~1000s, and the light intensity is 1~200mW / cm². 2 .

[0014] As a further explanation, the multi-stimulus responsive reverse electro-controlled liquid crystal dimming film provided by the present invention can be applied in the fields of smart windows, anti-counterfeiting encryption, or displays.

[0015] Compared with the prior art, the present invention discloses at least the following technical effects: This invention uses epoxy and thiol as raw materials, and forms a liquid crystal polymer network through a ring-opening reaction initiated by heating. Simultaneously, dichroic dyes are incorporated into the liquid crystal. Combined with the provided raw materials and methods, this lays the technical foundation for multi-stimulus response regulation. The thermal polymerization reaction of epoxy and thiol forms a moderately cross-linked polymer network, ensuring rotational space for liquid crystal molecules in an electric field. Furthermore, the good adhesion of the epoxy groups and the reinforcing effect of the interfacial cross-linking agent strengthen the bond between the two substrates, achieving high peel strength at a lower driving voltage. Based on this, the guest-host effect is utilized to align dye molecules with the liquid crystal molecules, enabling the device to achieve three switchable electrically controlled operating modes: When no power is applied, liquid crystal molecules are vertically aligned under the guidance of the vertical alignment layer, and dye molecules are synchronously aligned, maintaining the film's transparency; when a low-frequency electric field is applied, ions in the liquid crystal are excited, generating strong dynamic scattering, disturbing the orderly arrangement of dye molecules, and the film transitions to an absorption state; when a high-frequency electric field is applied, the ion-driven effect is significantly weakened, the electric field dominates the alignment of liquid crystal molecules, and the liquid crystal and dye molecules deflect in an orderly manner, resulting in a specific color in the film.

[0016] Furthermore, this dimming film can sense changes in external temperature. As the temperature rises, the ordered arrangement of liquid crystal and dye molecules is gradually disrupted, and the system orientation tends to become disordered, causing uneven refractive index and disturbances in the light propagation path. Simultaneously, the disordering of dye molecules alters their light absorption behavior, allowing the film to automatically reduce its transmittance at a continuously adjustable temperature critical point. This achieves adaptive temperature control without external power supply or human intervention, effectively reducing building heating and cooling energy consumption. After thermal polymerization, ultraviolet light curing is performed using a photomask. The polymer network in the unmasked area further cross-links, altering the local electro-optic response characteristics, allowing for convenient pattern writing on the device. This pattern is visible without power and hides due to liquid crystal reorientation after an electric field is applied. The photomask can be reused, reducing production costs. Therefore, the dimming film provided by this invention can form various optical states, including an unpowered transparent state, a low-frequency electric field absorption state, a high-frequency electric field color state, and a high-temperature absorption-enhanced state. It exhibits good transmittance in the open state, low driving voltage, low threshold voltage, and high substrate peel strength. Furthermore, by using dyes of different colors such as red, orange, blue, and purple, multi-colored dimming films can also be prepared, providing both light transmission and decorative effects while protecting privacy. Based on the above, this invention has promising application prospects in the fields of smart windows, automotive glass, anti-counterfeiting encryption, and displays. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 A schematic diagram of the non-electrically transmitted state of the multi-stimulus responsive inverse electro-controlled liquid crystal dimming film provided by the present invention, and the corresponding substrate layer, conductive layer, and vertical alignment layer. Figure 2 A schematic diagram of the absorption state of the multi-stimulus-responsive inverse electro-controlled liquid crystal dimming film provided by the present invention; Figure 3 A schematic diagram of the color states of the multi-stimulus-responsive inverse electro-controlled liquid crystal dimming film provided by the present invention; Figure 4 A schematic diagram of the temperature response of the multi-stimulus-responsive inverse electro-controlled liquid crystal dimming film provided by the present invention; Figure 5 A schematic diagram of the patterning method for the multi-stimulus-responsive inverse electro-controlled liquid crystal dimming film provided by the present invention; Figure 6 A schematic diagram of the patterned device with and without power applied to the multi-stimulus response inverse electro-controlled liquid crystal dimming film provided by the present invention; Figure 7The transmittance versus voltage curves provided in Embodiments 1 and 2 of the present invention; Figure 8 The contrast and on / off transmittance histograms provided for Embodiments 1 and 2 of the present invention; Figure 9 The above are bar charts showing the comparison between threshold voltage and saturation voltage provided in Embodiments 1 and 2 of the present invention. Figure 10 The visible light spectrum under different frequency electric fields provided in Embodiment 1 of the present invention; Figure 11 This is a thermal stimulus response spectrum provided in Embodiment 1 of the present invention; Figure 12 The visible light spectrum under different frequency electric fields provided in Embodiment 2 of the present invention; Figure 13 This is a thermal stimulus response spectrum provided in Embodiment 2 of the present invention; Figure 14 A bar chart comparing the mechanical property peel strength characterization provided in Embodiments 1 and 2 of the present invention. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0021] This invention provides a multi-stimulus responsive inverse electro-optical liquid crystal dimming film, its preparation method, and its application. Specifically, the multi-stimulus responsive inverse electro-optical liquid crystal dimming film comprises, sequentially stacked along the thickness direction, a first substrate layer, a first conductive layer, a first vertical alignment layer, a dye-doped thiol-epoxy liquid crystal polymer composite functional material layer, a second vertical alignment layer, a second conductive layer, and a second substrate layer. The raw materials for the thiol-epoxy liquid crystal polymer composite functional material layer include epoxy monomers, thiol monomers, dichroic dyes, liquid crystal materials, and curing agents. The first substrate layer and the second substrate layer are respectively composed of transparent substrates made of glass, polyethylene terephthalate, polyethylene naphthalate, polycarbonate, or polymethyl methacrylate; the first conductive layer and the second conductive layer are respectively made of ITO or FTO; the raw materials of the first vertical alignment layer and the second vertical alignment layer include vertical alignment agents and interfacial crosslinking agents. More specifically, the first vertical alignment layer and the second vertical alignment layer are respectively prepared by compounding PI or DMOAP with one or more of epoxy silane, acrylate silane, thiol silane, or amino silane, and the weight ratio of PI or DMOAP to silane compound is 0~5:0~15. The specific structural formula of the interfacial crosslinking agent includes, but is not limited to, the following types: ; The total thickness of the thiol-epoxy liquid crystal polymer composite functional material layer and the first and second vertical alignment layers is 1-80 μm. By weight, the raw materials include 40-99.9 parts of liquid crystal material, 0.01-40 parts of epoxy monomer, 0.01-40 parts of thiol monomer, 0.01-10 parts of curing agent, and 0.01-10 parts of dichroic dye. The raw materials for both the first and second vertical alignment layers, by weight, include 0-10 parts of vertical alignment agent and 0-10 parts of interfacial crosslinking agent.

[0022] The liquid crystal material is a negative liquid crystal; the epoxy monomer is at least one of the following types: aromatic ester, biphenyl, α-methylstyrene, naphthalene, azo, and monofunctional, and the specific structural formula includes, but is not limited to, the following types: ; The thiol monomer is one or more of the following: bis(3-mercaptopropionic acid) ethylene glycol, 4-mercaptomethyl-3,6-dithia-1,8-octanedithiol, 1,3-benzenedithiol, p-terphenyl-4,4-dithiol, 1,4-benzenedithiol, 1,3,5-benzotrithiol, propane-1,2,3-trithiol, 2,4,6-trimercapto-1,3,5-triazine trimethylolpropane tris(3-mercaptopropionate), pentaerythritol tetra(3-mercaptopropionate), or dipentaerythritol hexaalkyl(3-mercaptopropionate); the curing agent is an amine curing agent; the dichroic dye is an azo or anthraquinone; the vertical orientation agent is PI or DMOAP; and the interfacial crosslinking agent is a compound of one or more of the following: epoxy silane, acrylate silane, thiol silane, or amino silane.

[0023] As further explanation, this multi-stimulus responsive inverse electrochromic liquid crystal dimming film has three electrochromic working modes: a transparent state without electricity, an absorption state under a low-frequency electric field, and a color state under a high-frequency electric field, and the thermochromic temperature is 20~150℃.

[0024] This invention relates to a multi-stimulus-responsive inverse electrochromic liquid crystal dimming film capable of dynamically adjusting visible light. The invention introduces dyes into the dimming film, creating an interaction between the host liquid crystal and the guest dye through a host-guest effect, causing the dye molecules to align with the host liquid crystal molecules. By applying an external electric field or changing the external temperature, the alignment of the host liquid crystal is altered, leading to a change in the alignment of the guest dye molecules. This results in changes in the material's optical density and scattering interface, altering the material's transmittance, color, and light scattering state. Compared to other color-changing smart materials, such as organic electrochromic, photochromic, and suspended particles, host-guest liquid crystal materials offer advantages such as fast response speed, adjustable color, simple structure, and no need for polarizers.

[0025] Furthermore, this invention proposes a driving strategy combining dynamic scattering and liquid crystal dye doping, achieving control over transmission and scattering within a single-layer window. Simultaneously, the dimming film exhibits an adjustable temperature thermal response mode, and the invention also enables controllable patterning of the device. The successful development of this multifunctional smart window broadens the application prospects of optical materials in optical modulation and provides new ideas for multifunctional integrated devices in the field of smart windows.

[0026] More specifically, this invention employs a thermally initiated ring-opening polymerization reaction of epoxy and thiol to form a liquid crystal polymer network. A dichroic dye is mixed into the liquid crystal raw material, and the mixture is heated and stirred until homogeneous to color the liquid crystal raw material, forming a colored liquid crystal. The guest-host effect is utilized to align the dye molecules with the liquid crystal molecules. The epoxy-thiol reaction is a stepwise polymerization, resulting in a uniform network structure and good adhesion of the epoxy groups to the substrate. The crosslinking density can be controlled by adjusting the ratio of epoxy to thiol and the functionality of the thiol. Excessive crosslinking points hinder the rotation of liquid crystal molecules, leading to an increase in driving voltage; conversely, insufficient crosslinking points result in insufficient network strength and decreased peel strength between the two substrates. The first and second vertical alignment layers in this invention are composed of PI or DMOAP and a silane compound, with a weight ratio of PI or DMOAP to silane compound of 0~5:0~15. The silane compound contains functional groups that can react with the epoxy-thiol network, forming chemical bonds during thermal polymerization and improving interfacial bonding strength. An interfacial crosslinking agent can also be added separately to the liquid crystal mixture to further enhance interlayer anchoring.

[0027] Furthermore, dichroic dyes have a specific aspect ratio, with their long axes aligning with the orientation of liquid crystal molecules. When the liquid crystals are vertically aligned, the dye molecules are vertical, resulting in minimal absorption of incident light; when the liquid crystals are deflected or disordered, the dye molecules also deflect or become disordered, leading to enhanced absorption. By controlling the tilt angle of the liquid crystals with an electric field, transmittance and color depth can be continuously adjusted.

[0028] Based on the above, the multi-stimulus-responsive inverse electro-controlled liquid crystal dimming film of the present invention has three electro-control modes. When no power is applied, the vertical alignment layer guides the negative liquid crystal molecules to align perpendicularly to the substrate, and the dye molecules are also vertically aligned. The incident light is parallel to the long axis of the dye, resulting in extremely weak absorption. Furthermore, the ordinary light refractive index of the liquid crystal matches the polymer network, leading to weak scattering, and the dimming film is transparent. When a low-frequency electric field is applied, trace ions in the liquid crystal migrate in the electric field, causing space charge accumulation and fluid disturbance, disrupting the ordered arrangement of the liquid crystal and generating dynamic scattering. The dye molecule orientation becomes disordered, enhancing light absorption, and the dimming film is in an absorption state. When a high-frequency electric field is applied, the ion migration speed cannot keep up with the change in electric field, suppressing dynamic scattering. The electric field acts on the liquid crystal through dielectric anisotropy: the long axis of the negative liquid crystal molecules tends to be perpendicular to the direction of the electric field, while the direction of the electric field is perpendicular to the substrate. Therefore, the liquid crystal changes from vertical alignment to parallel alignment, forming a tilt angle. The dye molecules follow the rotation, and their long axes tend to be parallel to the substrate, generating strong absorption of a specific polarization component of the vertically incident light, exhibiting the complementary color of the dye, and the dimming film is in a colored state. The three modes are reversible and have a response time in the millisecond range.

[0029] This multi-stimulus responsive inverse electro-controlled liquid crystal dimming film can also respond to temperature changes. Below the thermochromic temperature, the liquid crystal is in the nematic phase, and the vertical alignment anchoring maintains vertical alignment, making the dimming film transparent. When the temperature rises to near the thermochromic temperature, the thermal motion of the liquid crystal intensifies, the anchoring effect relatively weakens, and the liquid crystal exhibits random disturbances, resulting in a decrease in alignment order; the thermal expansion of the polymer network changes the refractive index matching; and the thermally induced disorder of the azo dye increases the randomness of light absorption, all contributing to a significant decrease in transmittance, resulting in a shaded state, such as... Figure 4 As shown. By adjusting the liquid crystal clearing point, polymer crosslinking density, and dye type, the thermochromic temperature can be continuously adjusted from 20 to 150℃.

[0030] The above-mentioned dimming film is prepared as follows: epoxy monomer, thiol monomer, dichroic dye, liquid crystal material, curing agent, vertical alignment agent and interfacial crosslinking agent are mixed in proportion, heated and shaken evenly, added between the first conductive layer and the second conductive layer, and then subjected to thermally initiated ring-opening polymerization. The curing temperature is 40~120℃ and the time is 0.1~12h, thus obtaining a multi-stimulus responsive inverse electro-controlled liquid crystal dimming film.

[0031] Furthermore, this invention also provides a patterning method based on the above-mentioned dimming film, specifically: after thermal polymerization, a photomask is placed on the dimming film, and then cured with ultraviolet light for 10~1000s at a light intensity of 1~200mW / cm². 2 Patterned devices are obtained. The mechanism is as follows: after thermal polymerization, a small number of unreacted groups remain. Ultraviolet light causes further cross-linking in the exposed area, increasing the network density, while the unexposed area remains unchanged. When an electric field is applied, the liquid crystal in the exposed area is difficult to drive due to anchoring enhancement, and the pattern remains visible; the liquid crystal in the unexposed area responds normally, and the pattern disappears. Thus, the appearance and disappearance of the pattern can be reversibly controlled by switching the electric field on and off.

[0032] The multi-stimulus responsive inverse electro-hydraulic dimming film provided by this invention has promising applications in smart windows, anti-counterfeiting encryption, and display fields. The invention will be further described below with reference to specific embodiments.

[0033] Example 1 This embodiment specifically includes: mixing a dichroic dye into a liquid crystal raw material, heating and stirring until homogeneous, so that the liquid crystal raw material is colored to form a colored liquid crystal. The dichroic dye used is a positive dichroic azobenzene dye, which can be selected from one or more of dye numbers 1653, 1623, 1637, 1504, 1649, 1650, and 1618. In a specific example of this embodiment, dye number 1623 is added to a negative liquid crystal mixture mainly composed of one or more of XH9001V, GXV-7822-180, GXV-7312-075, SLC1717, or 5CB. The weight ratio between the components of the negative liquid crystal mixture can be arbitrarily selected within the range of 0.1~100:0.1~100:0.1~100. The weight ratio of dye number 1623 to the negative liquid crystal mixture is 1:79, and the total weight ratio of dye to liquid crystal raw material can be adjusted within the range of 0~30:100~70. The total thickness of the thiol-epoxy liquid crystal polymer composite functional material layer, the first vertical alignment layer, and the second vertical alignment layer is controlled within 1~80μm.

[0034] The colored liquid crystal is uniformly mixed with polymer monomers to form an isotropic liquid crystal mixture at room temperature. The polymer monomers are selected from epoxy resin, methyl methacrylate, or epoxy acrylate resin. The weight ratio of the dye-doped liquid crystal to the epoxy monomer can be arbitrarily selected between 1~40:99~60. The thiol monomer is selected from one or more of the above-mentioned substances, and the weight ratio of the thiol monomer to other liquid crystal mixtures is 1~40:99~60. The curing agent is an amine curing agent, which can be one or more of ethylenediamine, diethylenetriamine, imidazoline, 2,4,6-tris(dimethylaminomethyl)phenol, triethylamine, benzyldimethylamine, and N-methylmorpholine. The weight ratio of the curing agent to other liquid crystal mixtures is 0.5~10:99.5~90. The conductive layer is made of ITO, and the vertical orientation layer is a compound of PI or DMOAP with one or more of epoxy silane, acrylate silane, thiol silane or amino silane. The weight ratio of PI or DMOAP to silane compound is 0.1~5:0.1~20. The weight ratio of dye-doped liquid crystal mixture to interfacial crosslinking agent can be arbitrarily selected between 95~99.9:5~0.1.

[0035] After mixing the above raw materials, the mixture is heated by vibration within the range of 20~150℃ to fully integrate the system. Then, it is added between the first conductive layer and the second conductive layer and cured at 80℃ for 2 hours. The yellow liquid crystal device is obtained by thermally initiated ring-opening polymerization.

[0036] A multi-stimulus-responsive inverse electrochromic liquid crystal dimming film made with dichroic dyes showed that dye doping did not significantly change the driving voltage of the system, but the contrast was significantly improved.

[0037] like Figure 1As shown, in the absence of an electric field, due to the presence of the vertical alignment layer, the liquid crystal molecules are oriented perpendicular to the substrate, and the dye molecules are oriented in the same way as the liquid crystal molecules. Most of the incident light passes through the thiol-epoxy liquid crystal polymer composite functional material layer, with no light scattering or strong absorption, and the entire film is in a weakly absorbing transparent state. When a specific electric field is applied to excite the dynamic scattering of ions in the system, the molecular orientation is continuously perturbed, leading to refractive index mismatch in the tunable optical dielectric layer, and the film exhibits a hazy state.

[0038] like Figure 2 As shown, when a low-frequency electric field is applied, the ions in the system are excited to form dynamic scattering, and the thin film exhibits an absorption state.

[0039] like Figure 3 As shown, under the action of a high-frequency electric field, the driving effect of ions on liquid crystal is significantly weakened, and the system changes from a dynamic scattering mechanism to an electric field orientation-dominated mechanism. At this time, the electric field mainly acts on the orientation rearrangement of liquid crystal and dye molecules: the liquid crystal molecules undergo rapid orientation oscillation, and the dichroic dye is synchronously deflected under the drive of the guest-host effect, resulting in enhanced selective absorption of light in a specific polarization and wavelength range.

[0040] Compared to the strong scattering state under low-frequency driving, the system exhibits reduced scattering but enhanced absorption in this mode, resulting in a transmissive state with color modulation capabilities. This represents a shift from scattering-dominated to absorption-dominated light modulation mode. By controlling the electric field conditions, rapid transitions can be achieved between transparent, opaque, and absorption-enhanced states.

[0041] Furthermore, by changing the type of dye, the dye's strong absorption band in the visible light spectrum changes, and the device can then produce the color corresponding to that dye. For example... Figure 4 As shown, the device can regulate light through temperature response: under thermal stimulation, the ordered arrangement of liquid crystal molecules and dichroic dye molecules is further disrupted, the local orientation inhomogeneity within the system is significantly enhanced, and the molecular arrangement is in a highly disordered state, thereby causing stronger local refractive index inhomogeneity and light propagation path perturbation; the disordered rearrangement of dye molecules further alters its light absorption behavior, causing the device to exhibit a thermally induced low transmittance state. In this example, the adaptive thermal transition temperature of the device is 120℃.

[0042] Example 2 This embodiment is an improvement based on embodiment 1. The technical content disclosed in embodiment 1 will not be described again here. The content disclosed in embodiment 1 also belongs to the disclosure content of this embodiment.

[0043] This embodiment specifically includes: mixing a dichroic dye into a liquid crystal raw material, heating and stirring until uniform to color the liquid crystal raw material and form a colored liquid crystal. The dichroic dye is also a positive dichroic azobenzene dye, and the dye number can be one or more of 1653, 1623, 1637, 1504, 1649, 1650, and 1618. In a specific example of this embodiment, four dyes, 1623, 1649, 1650, and 1504, are added to a liquid crystal mixture mainly composed of GXV-7312-075. The weight percentage of dye to liquid crystal raw material is 0.1125:0.1075:0.2175:0.0625:99.5, wherein the weight ratio of each component can be arbitrarily selected within the range of 0.01~10:0.01~10:0.01~10:99.99~90.

[0044] Following the preparation steps in Example 1, a black low-temperature multifunctional liquid crystal device was obtained. Testing showed that the adaptive thermal transition temperature of the device in this example is 72°C.

[0045] Example 3 This embodiment is an advancement of patterned application based on Embodiment 1. The technical content disclosed in Embodiment 1 will not be described again here, and the content disclosed in Embodiment 1 is also part of the disclosure content of this embodiment.

[0046] This embodiment specifically includes: taking the yellow liquid crystal device prepared in Example 1, placing a photomask on the device, and then reacting it under ultraviolet light. The ultraviolet curing time is 600 seconds, and the ultraviolet light intensity is 80 mW / cm². 2 Patterned devices can then be obtained, such as Figure 5 As shown. Schematic diagrams before and after applying an electric field are shown below. Figure 6 As shown, the pattern disappears after power is applied and reappears after the electric field is removed. This light-controlled patterning method provides strong support for the promotion of visible light anti-counterfeiting technology in practical applications.

[0047] Furthermore, the devices obtained in Examples 1 and 2 above were subjected to performance tests, hereinafter referred to as Example 1 and Example 2, respectively, corresponding to Examples 1 and 2. The results are as follows: In addition, the present invention also provides the electro-optic performance characterization results of Examples 1 and 2, verifying the excellent dimming performance of the multi-stimulus-responsive inverted electro-controlled liquid crystal dimming film: such as Figure 7As shown, the transmittance versus voltage curves indicate that both examples exhibit typical inverse electro-optical response characteristics. When no power is applied, the device maintains a high transmittance transparent state. As the driving voltage increases, the ordered arrangement of the liquid crystal and dye molecules is gradually altered by the electric field, and the transmittance rapidly decreases and approaches zero. Example 2 shows a faster rate of transmittance decrease with increasing voltage, exhibiting higher electro-optical response sensitivity and enabling switching from a transparent to an opaque state at lower voltages. Figure 8 As shown in the bar chart, the contrast ratio and transmittance in both on and off states are compared. Example 2 has a contrast ratio of 328.56, a significant improvement over Example 1's 104.16. This indicates a greater difference in transmittance between on and off states, resulting in better visual differentiation of the dimming effect. While ensuring good light transmission in the transparent state, it also provides stronger light-blocking and privacy protection in the off state. Figure 9 As shown in the bar chart, the comparison between the threshold voltage and the saturation voltage further confirms that the driving voltage parameter of Example 2 is lower, which is more conducive to the practical application of the device in low-power scenarios.

[0048] like Figure 10 As shown, the visible light spectral characterization results under different frequency electric fields in Example 1 verify the frequency response modulation characteristics of the multi-stimulus response inverse electro-controlled liquid crystal dimming film of the present invention: When no power is applied, the liquid crystal molecules maintain vertical alignment under the action of the vertical alignment layer, and the dichroic dye molecules are synchronously aligned. The device exhibits high transmittance in the visible light region, with the transmittance in the 550-800 nm band stably maintained above 75%. Simultaneously, a characteristic absorption peak of the dye is observed at approximately 400 nm, corresponding to the spectral performance of the transparent state. After applying a low-frequency electric field of 0.3 kHz, the system... When internal ions are excited, dynamic scattering occurs, and the orderly arrangement of dye molecules is disturbed, resulting in a significant decrease in the transmittance of the device across the entire wavelength range, with the overall transmittance below 10%, indicating that it has entered the absorption state. When a 3kHz high-frequency electric field is applied, the ion-driven effect weakens, and the electric field dominates the orderly deflection of liquid crystal and dye molecules. The transmittance of the device recovers to over 75% in the long-wavelength region (600~800nm), while maintaining a low transmittance in the short-wavelength region (300~550nm), forming the spectral characteristics of a specific color state. This demonstrates the precise control of the electric field frequency on the light transmission behavior of the device.

[0049] like Figure 12As shown, the visible light spectrum characterization results under different frequency electric fields in Example 2 further confirm the frequency response characteristics of the dimming film of the present invention: When no power is applied, the liquid crystal and dye molecules are vertically aligned, and the device exhibits high transmittance in the visible light region. The transmittance in the 700~800nm ​​band is stably maintained at about 80%, ensuring the light-gathering effect of the transparent state; after applying a low-frequency electric field of 0.1kHz, the ion scattering effect dominates, the orderly arrangement of dye molecules is destroyed, and the transmittance of the device across the entire wavelength band is greatly suppressed, with the overall transmittance being less than 10%, exhibiting a clear absorption state; when a high-frequency electric field of 3kHz is applied, the electric field dominates the orderly deflection of the liquid crystal and dye molecules, and the transmittance of the device rises to nearly 80% in the long-wavelength region (650~800nm), while maintaining a low transmittance in the mid-short-wavelength region (400~600nm), forming a spectral response with color tendency.

[0050] Compared with Example 1, Example 2 has clearer spectral distinction at different frequencies, further demonstrating its superior frequency response control effect, and providing direct experimental support for the realization of three-state electronic control switching in this invention.

[0051] like Figure 11 As shown, the thermal stimulus response spectral characterization results of Example 1 verify the temperature adaptive control characteristics of the multi-stimulus response inverse electrochromic liquid crystal dimming film of the present invention: at room temperature of 25℃, the liquid crystal molecules and dichroic dye molecules maintain an ordered arrangement under the action of the vertical alignment layer, and the device exhibits high transmittance in the visible light region. The transmittance in the 400-800nm ​​band gradually increases with increasing wavelength, and the transmittance above 600nm is close to 100%, exhibiting the spectral characteristics of a transparent state; when the temperature rises to 120℃ and 140℃, the thermal disturbance... The movement disrupts the ordered arrangement of liquid crystal molecules, causing molecular orientation to become disordered. This significantly enhances the local refractive index inhomogeneity within the system, leading to stronger light propagation path perturbation and light scattering effects. Simultaneously, the disordered rearrangement of dye molecules further alters its light absorption behavior, resulting in a significant reduction in the device's transmittance across the entire wavelength range. The transmittance in the 400-500nm wavelength range drops to approximately 15%, exhibiting a thermally induced low transmittance state. The spectral curves at 120℃ and 140℃ essentially overlap, indicating that the thermal response regulation in Example 1 has become stable in the temperature range above 120℃.

[0052] like Figure 13As shown, the thermal stimulus response spectral characterization results of Example 2 further confirm the temperature response characteristics of the dimming film of the present invention, and exhibit more sensitive low-temperature response performance: at room temperature of 26℃, the liquid crystal and dye molecules maintain a vertical orientation, and the device exhibits high transmittance in the visible light region. The transmittance in the 400-800nm ​​band gradually increases with increasing wavelength, and the transmittance in the band above 700nm remains stable at over 75%. When the temperature rises to 72℃, the ordered arrangement of liquid crystal and dye molecules is destroyed under thermal stimulation, the internal orientation inhomogeneity of the system is enhanced, and the combined effect of light scattering and dye absorption effect significantly reduces the transmittance of the device, with the transmittance in the 400-800nm ​​band all below 30%. When the temperature is further increased to 90℃, the degree of molecular disorder intensifies, the transmittance of the device continues to decrease, and a more obvious thermally induced low transmittance state is exhibited.

[0053] Compared with Example 1, Example 2 has a lower thermal response trigger temperature, achieving significant transmittance control at 72°C. This indicates that after optimization of its formula and process, it has higher thermal response sensitivity and is more suitable for the temperature variation range of actual application scenarios such as buildings and automobiles. This provides direct experimental support for the present invention to achieve adaptive temperature control without external energy.

[0054] Finally, as Figure 14 As shown, the peel stress of Example 1 is approximately 360 kPa, and that of Example 2 is approximately 275 kPa. Both examples exhibit high interlayer bonding strength. This is because the present invention employs an epoxy-thiol thermally initiated polymerization system, combined with the synergistic effect of the interfacial crosslinking agent, which effectively strengthens the interfacial adhesion between the vertically oriented layer, the thiol-epoxy liquid crystal polymer composite functional material layer, and the substrate. This solves the problems of insufficient interlayer bonding and easy peeling failure in traditional inverse electro-optic dimming films. The higher peel strength of Example 1 indicates that its optimized formulation and process result in superior interfacial crosslinking, better resisting mechanical stress during actual use, ensuring the long-term stability of the device structure, and providing mechanical performance support for the reliable application of dimming films in scenarios such as smart windows and automotive glass.

[0055] Therefore, the above-mentioned multi-stimulus-responsive inverse electro-controlled liquid crystal dimming film, its preparation method, and its application utilize epoxy-thiol thermal polymerization to construct a cross-linked grid, ensuring electro-optic response under low driving voltage while significantly improving substrate peel strength. Based on the host-guest effect, it achieves three-state electro-controlled switching of un-electro-activated transparency, low-frequency absorption, and high-frequency color rendering, improving light transmission and privacy shielding effects. On the one hand, it can achieve adaptive transmittance regulation through temperature triggering, effectively reducing building energy consumption. On the other hand, it can also write reversible patterns of electric field through ultraviolet curing of photomasks, and the photomasks can be reused to reduce costs, providing support for visible light anti-counterfeiting. It can be widely used in smart windows, automotive glass, and display fields.

[0056] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0057] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A multi-stimulus responsive inverse electro-controlled liquid crystal dimming film, characterized in that, It includes a first substrate layer, a first conductive layer, a first vertical alignment layer, a dye-doped thiol-epoxy liquid crystal polymer composite functional material layer, a second vertical alignment layer, a second conductive layer, and a second substrate layer, which are stacked sequentially along the thickness direction. The raw materials for the thiol-epoxy liquid crystal polymer composite functional material layer include epoxy monomers, thiol monomers, dichroic dyes, liquid crystal materials, and curing agents. The raw materials for both the first vertical orientation layer and the second vertical orientation layer include a vertical orientation agent and an interfacial crosslinking agent.

2. The multi-stimulus responsive inverse electro-controlled liquid crystal dimming film according to claim 1, characterized in that, The total thickness of the thiol-epoxy liquid crystal polymer composite functional material layer, the first vertical alignment layer, and the second vertical alignment layer is 1~80μm, and its raw materials include, by weight: 40~99.9 parts of liquid crystal material, 0.01~40 parts of epoxy monomer, 0.01~40 parts of thiol monomer, 0.01~10 parts of curing agent, and 0.01~10 parts of dichroic dye; The raw materials for the first vertical orientation layer and the second vertical orientation layer are, by weight, 0-10 parts of vertical orientation agent and 0-10 parts of interfacial crosslinking agent.

3. The multi-stimulus responsive inverse electro-controlled liquid crystal dimming film according to claim 2, characterized in that, The liquid crystal material is a negative liquid crystal; the epoxy monomer is at least one of the following: aromatic ester type, biphenyl type, α-methylstyrene type, naphthalene type, azo type, and monofunctional type; the thiol monomer is one or more of the following: bis(3-mercaptopropionic acid) ethylene glycol, 4-mercaptomethyl-3,6-dithia-1,8-octanedithiol, 1,3-benzenedithiol, p-terphenyl-4,4-dithiol, 1,4-benzenedithiol, 1,3,5-benzotrithiol, propane-1,2,3-trithiol, 2,4,6-trimercapto-1,3,5-triazine trimethylolpropane tris(3-mercaptopropionate), pentaerythritol tetra(3-mercaptopropionate), or dipentaerythritol hexaalkyl(3-mercaptopropionate).

4. The multi-stimulus responsive inverse electro-controlled liquid crystal dimming film according to claim 2, characterized in that, The curing agent is an amine curing agent, specifically one or more of ethylenediamine, diethylenetriamine, imidazoline, 2,4,6-tris(dimethylaminomethyl)phenol, triethylamine, benzyldimethylamine, and N-methylmorpholine; the dichroic dye is an azo or anthraquinone; the vertical orientation agent is one or more of PI or DMOAP; and the interfacial crosslinking agent is a compounding agent used to enhance interlayer bonding, specifically one or more of epoxy silane, acrylate silane, thiol silane, or amino silane.

5. The multi-stimulus responsive inverse electro-controlled liquid crystal dimming film according to claim 1, characterized in that, The first substrate layer and the second substrate layer are each independently selected from glass, polyethylene terephthalate, polyethylene naphthalate, polycarbonate or polymethyl methacrylate; the first conductive layer and the second conductive layer are each independently selected from ITO or FTO.

6. The multi-stimulus responsive inverse electro-controlled liquid crystal dimming film according to claim 1, characterized in that, The dimming film has three electrically controlled operating modes: a transparent state without electricity, an absorption state under a low-frequency electric field, and a color state under a high-frequency electric field. The thermochromic temperature of the dimming film is 20~150℃.

7. A method for preparing a multi-stimulus responsive inverse electro-controlled liquid crystal dimming film as described in any one of claims 1 to 6, characterized in that, include: The epoxy monomer, thiol monomer, dichroic dye, liquid crystal material, curing agent, vertical alignment agent and interfacial crosslinking agent are mixed evenly according to the ratio and added between the first conductive layer and the second conductive layer. After thermally initiated ring-opening polymerization, the multi-stimulus responsive inverse electro-controlled liquid crystal dimming film is obtained.

8. The preparation method according to claim 7, characterized in that, The curing temperature of the thermally initiated ring-opening polymerization is 40~120℃, and the curing time is 0.1~12h.

9. The preparation method according to claim 7, characterized in that, Following the thermally initiated ring-opening polymerization, the process further includes: placing a photomask on the resulting multi-stimulus responsive inverse electro-hydraulic dimming film, followed by ultraviolet (UV) light curing to obtain a patterned device; wherein the UV curing time is 10–1000 s, and the light intensity is 1–200 mW / cm². 2 .

10. The application of a multi-stimulus responsive inverse electro-hydraulic dimming film as described in any one of claims 1 to 6 in the fields of smart windows, anti-counterfeiting encryption, or displays.

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