Polymer network stabilized multistable dimming device

Abstract

Provided in the present application is a polymer network stabilized multistable dimming device. The dimming device comprises a pair of opposite transparent conductive base layers and a dimming layer disposed between the transparent conductive base layers, wherein the dimming layer is a liquid crystal layer comprising polymer networks, and the polymer networks are uniformly arranged. The dimming device at least includes two stable states: a transmissive state in which incident light is substantially transmitted, and a haze state in which the incident light is substantially scattered, wherein the transmissive state has a haze of no greater than 5%, and the haze state has a haze of no less than 85%. In the present application, polymerizable monomers are introduced into a binary mesogen system, the content of the polymerizable monomers is optimized, and a helical pitch P is adjusted to 0.2-2 μm, such that the haze of the dimming device in a transmissive state is reduced, and the haze and stability of the dimming device in a haze state are increased.

Description

A polymer network-stabilized multistable dimming device

[0001] This application is based on and claims priority to Chinese Patent Application No. CN202410671290.6, filed on May 28, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This invention relates to the field of liquid crystals, and more specifically to a polymer network-stabilized multistable dimming device. Background Technology

[0003] Dimming devices, as a novel dimming technology, can control light propagation through electronic, temperature, and voltage control, thus finding applications in various fields. Common dimming device technologies include PDLC dimming technology, dye-based liquid crystal dimming technology, SPD dimming technology, EC electrochromic technology, and bistable dimming technology. Among these, PDLC dimming technology and bistable dimming technology offer privacy protection features, but the high haze at side viewing angles limits their application.

[0004] Bistable dimming technology is renowned for having at least two stable states that remain stable even after power loss. These include at least one transparent state with clear visibility from all angles and at least one shielded state providing all-around privacy protection. Switching between these states requires only a pulse lasting a second, and the system can maintain stability even after power loss with zero power consumption. However, in terms of production line methods, liquid crystal dimming devices are generally manufactured using the ODF (Optical Distribution Frame) method. During ODF fabrication, cell thickness control typically employs liquid crystal doped spacers, sprayed spacers, or photo spacers (PS). Liquid crystal doped spacers and sprayed spacers are prone to unevenness, so the display industry currently favors the PS method for cell thickness control. However, the cell thickness of liquid crystal display devices in the display industry is relatively thin, typically 2-10 μm. Although current photoresist technology promises to break through the 15 μm height barrier, further increases are extremely difficult. To ensure high privacy protection in the shielded state, bistable dimming technology usually requires a cell thickness of at least 15 μm. This is limited by the height of the PS during ODF fabrication, and a thicker cell inevitably leads to higher driving voltage and power consumption, posing safety and energy consumption issues. Although the above problems can all be solved by reducing the thickness of the housing, the scattering effect of the bistable dimming glass in the shielded state becomes worse after the housing thickness is reduced, and the ideal privacy protection effect cannot be achieved.

[0005] Therefore, there is a need to provide a dimming device that has low power consumption, high haze in the scattering state, low haze in the transparent state, and good stability to overcome the above limitations. Summary of the Invention

[0006] The problem the invention aims to solve

[0007] The purpose of this invention is to provide a multi-stable dimming device, which has at least two stable states that remain stable after power failure. At least one of the stable states is a transmission state, in which the collimated transmitted light flux of visible light incident on the liquid crystal layer is greater than the scattered light flux. At least one of the stable states is a fog state, in which the collimated transmitted light flux of visible light incident on the liquid crystal layer is less than the collimated transmitted light flux of the transmission state. At the same time, the fog level of the dimming device in the transmission state is not greater than 5%, and the fog level in the fog state is not less than 85%.

[0008] Another objective of this invention is to provide a dimming layer material that can reduce cell thickness and driving voltage while still maintaining high haze and haze stability in the haze state of a multi-stable dimming device.

[0009] Problem Solving Methods

[0010] To address the aforementioned problems, the inventors discovered that by dispersing a cholesteric liquid crystal composition within a polymer network domain containing an appropriate density, and simultaneously curing it in the presence of an elastic constant modulator, a polymer network-stable multistable dimming device is obtained. This device can impart desired transmittance haze and haze state haze, while also achieving reduced cell thickness and reduced driving voltage, thus completing the present invention. In other words, the present invention provides the following solution.

[0011] A polymer network-stabilized multistable dimming device includes a pair of opposing transparent conductive substrates and a dimming layer disposed between the transparent conductive substrates. The dimming layer is a liquid crystal layer comprising a polymer network, which is uniformly arranged. The dimming device includes at least two stable states: a transmittance state, in which incident light is substantially transmitted, and a hazy state, in which incident light is substantially scattered. The transmittance state exhibits a planar texture, where the liquid crystal molecules are arranged in a substantially ordered manner, forming a substantially uniform planar molecular arrangement with a helical structure. When incident light strikes a glass surface in this state, the dimming glass scatters the incident light relatively little. The hazy state exhibits a focal conic texture, where, due to the strong torque and elasticity of the liquid crystal molecules, the sudden application of an external electric field causes the liquid crystal layer to form multiple disordered molecular domains. Within each molecular domain, the liquid crystal molecules still have a substantially ordered helical arrangement, while the orientation between the molecular domains is substantially disordered. After the external electric field is removed, this multi-domain disordered molecular arrangement can be maintained for a long time, forming a stable liquid crystal molecular arrangement. When incident light strikes the liquid crystal layer, the multi-domain structure of the liquid crystal molecules can strongly scatter the incident light.

[0012] The aforementioned transparent state is obtained by applying a first voltage between the first transparent conductive layer and the second transparent conductive layer. The first voltage is a first alternating pulse voltage, the amplitude of which is not higher than 70V, and the frequency of which is 50-10000Hz. The aforementioned hazy state is obtained by applying a second voltage between the first transparent conductive layer and the second transparent conductive layer. The second voltage is a second alternating pulse voltage, the amplitude of which is not higher than the amplitude of which is the first alternating voltage, and the frequency of which is 50-10000Hz. More preferably, the switching voltage between the two stable states of the dimming device is not higher than 70V, the haze in the transparent state is not higher than 5%, and the haze in the hazy state is not lower than 85%. That is, the dimming device has a low driving voltage, high haze in the hazy state, and low haze in the transparent state.

[0013] Furthermore, the uniform arrangement is arranged substantially perpendicular to or substantially parallel to the transparent conductive substrate.

[0014] Furthermore, the uniform alignment is achieved through an alignment layer disposed on the inner surface of the transparent conductive substrate. This alignment layer provides anchoring energy for the orientation of the liquid crystal molecules. Generally, dimming devices use a friction method, i.e., rubbing the substrate surface in contact with the liquid crystal along a certain direction to align the liquid crystal molecules along the rubbing direction. By adding an alignment layer before friction, a better alignment effect can be obtained. There can be only one alignment layer, disposed on any one of the inner surfaces of the transparent conductive substrate (i.e., the surface in contact with the dimming layer), or there can be two, located on the inner surfaces of two different transparent conductive substrates, further enhancing the alignment effect. The alignment layer is generally formed by curing an alignment agent, which is an organic polymer material such as PVB, siloxane, or polyimide. Depending on the pretilt angle (i.e. the angle formed between the direction of the long axis of the liquid crystal molecules and the surface of the alignment layer when the liquid crystal molecules are arranged in an orderly manner on the surface of the alignment layer), alignment layers are divided into basic planar alignment layers, where the long axis of the liquid crystal molecules on the surface of the alignment layer is basically parallel to the surface of the alignment layer, such as IPS, TN, and STN types; or basic perpendicular alignment layers, where the long axis of the liquid crystal molecules is basically perpendicular to the surface of the alignment layer, such as VA type.

[0015] Here, the polymer network is placed in the dimming layer, and its arrangement depends on the orientation state of the polymerizable monomers during curing. The orientation state of the polymerizable monomers during curing depends on the orientation state of the liquid crystal molecules in the dimming layer. To ensure low haze in the P-state, the polymer network needs to be cured in a uniform state. Its arrangement is basically divided into two types: one is basically perpendicular to the transparent conductive substrate, in which case the liquid crystal molecules are in the H-state; the other is basically parallel to the transparent conductive substrate, in which case the liquid crystal molecules are in the P-state. Curing methods include UV and / or thermal curing, with UV curing being preferred. The polymer network formed after curing interacts with the liquid crystal molecules, making the orientation of the liquid crystal molecules more stable under the action of anchoring forces, especially improving the multi-domain stability of the Fc state.

[0016] The highlight of the dimming layer material of the present invention is that it contains a specific cholesteric liquid crystal composition and a specific amount of RM material, and the dimming material that satisfies specific temperature-dependent parameters can stably impart the desired pitch length, the desired optical anisotropy Δn and dielectric anisotropy Δε. Specifically, the present invention relates to the following dimming layer material.

[0017] A material for a dimming layer used in the dimming device comprises: a liquid crystal composition and at least one polymerizable monomer, wherein the liquid crystal composition comprises at least one cholesteric liquid crystal composition, at least one initiator and at least one elastic constant modifier, characterized in that the polymerizable monomer accounts for 0.5wt%-1.5wt% of the dimming layer, and the liquid crystal composition has Δn≥0.15, Δε≥5, and a helical pitch P of 0.2-2μm.

[0018] Furthermore, the liquid crystal composition has Δn≥0.2, Δε≥10, and a helical pitch P of 0.8μm-2μm.

[0019] Furthermore, the elastic constant modifier in this application is selected from at least one of general formula I.

[0020]

[0021] in:

[0022] R1 and R2 each independently represent -H, -F, -Cl, -CN, -NCS, or an alkyl chain with 1-25 carbon atoms, wherein one or more H atoms in the alkyl chain with 1-25 carbon atoms can be independently substituted by a halogen, and one or more non-adjacent -CH2- atoms in the alkyl chain with 1-25 carbon atoms can be independently substituted by -O-, -CH=CH-, -CH=CF-, or -CF=CF-.

[0023] X is a straight-chain or branched alkylene group with 3-40 carbon atoms, wherein one or more -CH2- groups in the straight-chain or branched alkylene group with 3-40 carbon atoms can be independently replaced by -O-, -CH(F)-, -CH(Cl)-, or -CH=CH-, and the substitution does not involve two -O- groups adjacent to each other or two double bonds adjacent to each other; preferably, X is -(CH2). n -、-O(CH2) n O-, where n is an odd number between 3 and 40;

[0024] MG1 and MG2 each independently represent mesocrystalline units;

[0025] Preferably, the elastic constant modifier accounts for 10wt%-40wt% of the liquid crystal composition;

[0026] Compared with existing compositions, the cholesteric liquid crystal composition according to the present invention uses an appropriate amount of polymerizable monomers in conjunction with an elastic constant modifier conforming to general formula I. Under the influence of electric field, interface, and molecular elastic forces, the polymerizable monomer molecules align with the liquid crystal molecules, achieving an arrangement approximately parallel to or perpendicular to the substrate direction. This is then cured by ultraviolet light to form a spatial network structure, anchoring the liquid crystal molecules within the dimming layer, reducing the focal cone domain size in the hazy state, and improving the haze and stability of the dimming device in the hazy state. As the content of polymerizable monomers increases, the network structure density within the dimming layer increases, improving the haze and stability in the hazy state. However, when the spatial density of the network structure is too high, it affects the planar orientation of the transmitted state, causing an increase in transmitted state haze. Therefore, it is necessary to specifically limit the range of polymerizable monomer content. When the content is too low, the improvement effect is not significant and cannot meet the requirements of the present invention; when the content is too high, the transmitted state haze deteriorates severely, also failing to meet the requirements of the present invention.

[0027] Furthermore, the mesocrystalline unit is selected from the group composed of mesocrystalline units of general formula II.

[0028]

[0029] in:

[0030] H1 and H2 each independently represent a ring structure, and H3 is either a single bond or a ring structure, wherein the ring structure is selected freely. , , , , , , , , , , , , , , , , , , and The group consisting of one or more H atoms in the cyclic structure, wherein each H atom may be independently replaced by a halogen, an alkyl group having 1-10 C atoms, or an ester group;

[0031] Y and Z each independently represent a single bond or an alkyl chain with 1-10 carbon atoms, wherein one or more H atoms in the alkyl chain with 1-10 carbon atoms can be independently substituted by a halogen, and one or more non-adjacent -CH2- atoms in the alkyl chain with 1-10 carbon atoms can be independently substituted by -O-, -COO-, -CH=CH-, -CH=CF-, or -CF=CF-.

[0032] More specifically, the compound of general formula I is selected from one or more compounds in the group consisting of:

[0033] (NPP5PPN) General Formula I-1;

[0034] (NPP7PPN) General Formula I-2;

[0035] (NPP9PPN) General Formula I-3;

[0036] (NPP11PPN) General Formula I-4;

[0037] (NPPO5OPPN) General Formula I-5;

[0038] (NPPO7OPPN) General Formula I-6;

[0039] (FPP7PPN) General Formula I-7;

[0040] (FGIP7PGF) General Formula I-8;

[0041] (FGIPP9PGF) General Formula I-9;

[0042] (FGIP11PGF) General Formula I-10;

[0043] (NUIP7PUN) General Formula I-11;

[0044] (FPP7PPF) General Formula I-12;

[0045] (FPP9PPF) General Formula I-13;

[0046] (FPP11PPF) General Formula I-14;

[0047] (NGIP7PGN) General Formula I-15;

[0048] (NGIP9PGN) General Formula I-16;

[0049] (NGIP11PGN) General Formula I-17;

[0050] (3PP7PP3) General Formula I-18;

[0051] (3PP9PP3) General Formula I-19;

[0052] (3PP11PP3) General Formula I-20;

[0053] (SPP9PPS) General Formula I-21;

[0054] Preferably, the polymerizable monomer is a mono-, di-, or multi-reactive RM material.

[0055] Preferably, the polymerizable monomer is selected from any one or more of RM257, RM82, and LC242, and examples of particularly suitable and preferred polymerizable monomers are shown in the following list.

[0056] RM257

[0057] RM82

[0058] LC242

[0059] Preferably, the cholesteric liquid crystal composition comprises at least one nematic liquid crystal compound and at least one chiral compound; as a preferred embodiment, the at least one nematic liquid crystal compound may be a commercially available nematic liquid crystal composition, such as E7 or SVT3130-10, or may be a prepared nematic liquid crystal composition.

[0060] Preferably, the chiral compound is selected from any one or more of CB15, R(S)5011, R(S)6N, R(S)2011, and R(S)1011.

[0061] Preferably, the initiator is a photoinitiator; more preferably, the photoinitiator is selected from 4,4'-bismaleimide diphenylmethane, 1,4-bis(maleimide)butane, 1,8-bis(maleimide)-3,6-dioxaoctane, 1,11-bismaleimide-3,6,9-trioxaundecane, 1,6-di(maleimide)hexane, bismaleimide methyl ether, N-cyclohexylmaleimide, etc. The photoinitiator is selected from one or more of the following: maleimide, N-phenylmaleimide, N-benzylmaleimide, benzoin methyl ether, benzoin dimethyl ether, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, benzophenone, and phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide; particularly preferred is the following combination, wherein the photoinitiator is selected from one or more of the following: 4,4'-bismaleimide diphenylmethane, 1,4-bis(maleimide)butane, benzoin methyl ether, and benzoin dimethyl ether.

[0062] 4,4'-bismaleimide diphenylmethane: ;

[0063] 1,4-Bis(maleimide)butane: ;

[0064] Benzoin methyl ether: ;

[0065] Benzoin dimethyl ether: ;

[0066] Preferably, the photoinitiator accounts for 0.05wt%-0.2wt% of the liquid crystal composition.

[0067] This invention also relates to a method for preparing the above-mentioned dimming device, comprising:

[0068] 1) Mixing a liquid crystal composition with a polymerizable monomer to form a liquid crystal mixture;

[0069] 2) Fill the liquid crystal mixture into the liquid crystal cell; the liquid crystal mixture can be formed into the cell by vacuum filling or ODF, and the liquid crystal mixture in the liquid crystal layer is required to be in a relatively uniform state;

[0070] 3) To form a planar or vertical texture in the liquid crystal mixture within the liquid crystal cell;

[0071] 4) When a planar texture is formed, the polymerizable monomers are polymerized under zero electric field to form the dimming device; the dimming device is driven to a planar state by selecting an appropriate driving voltage, and the driving voltage is not lower than the first voltage mentioned above; when a vertical texture is formed, the polymerizable monomers are polymerized under energized state, and the driving voltage is not lower than the first voltage mentioned above to form the dimming device.

[0072] The effects of the invention

[0073] This application provides a polymer network-stabilized multi-stable dimming device. Polymerizable monomers are introduced into the bimesocrystalline system of its dimming layer, and their content is optimized. During ultraviolet curing, polymer network domains with multiple arrangements are formed, which can anchor liquid crystal molecules inside the liquid crystal layer. The helical pitch P is adjusted to 0.2-2μm to reduce the focal cone domain size in the hazy state, thereby reducing the haze of the dimming device in the transparent state and improving the haze and stability of the dimming device in the hazy state. Attached Figure Description

[0074] Figure 1 is a schematic diagram of the structure of a multistable dimming device in some embodiments of this application and various arrangements of the polymer network. Detailed Implementation

[0075] In the following description, numerous specific details are set forth for the purpose of explanation and to provide a comprehensive understanding of the invention. However, it will be apparent to those skilled in the art that the invention can be practiced without these specific details. In other examples, well-known structures and apparatuses are shown in block diagrams. In this regard, the illustrative exemplary embodiments given are for illustrative purposes only and do not constitute a limitation on the invention. Therefore, the scope of protection of the invention is not limited to the specific embodiments described above, but is determined solely by the scope of the appended claims.

[0076] All components used in the following embodiments can be synthesized using known methods or obtained commercially. These synthesis techniques are conventional, and the resulting liquid crystal compounds have been tested and found to meet electronic compound standards.

[0077] Terms and Definitions

[0078] The term "mesogen" includes rod-shaped, disk-shaped, plate-shaped, and banana-shaped structures, with a hard core in the center usually surrounded by flexible side chains. The anisotropy of its shape is the basis for the formation of liquid crystal phases. This structure has the ability to induce (LC) phase behavior, and it does not necessarily have to exhibit an LC phase itself.

[0079] The term "polymerizable monomer" refers to liquid crystal materials with relatively low molecular weight. These liquid crystal materials generally have a liquid crystal core and one or more reactive functional groups at the ends, which can be polymerized, crosslinked, or cured to form a polymer network by irradiation under ultraviolet light.

[0080] The term "polymer network" refers to a polymer network formed by cross-linking and curing polymerizable monomers.

[0081] Polymerizable compounds with one polymerizable group are also called single-reactive RM materials, compounds with two polymerizable groups are also called two-reactive RM materials, and compounds with more than two polymerizable groups are also called multi-reactive RM materials.

[0082] Optical anisotropy Δn is defined as follows:

[0083] Δn represents the optical anisotropy of the nematic liquid crystal composition, where Δn = n e -n o n e For unusual refractive index, n o The refractive index of ordinary light was measured using an Abbe refractometer under the following conditions: sodium lamp light source wavelength 589 nm, measurement temperature 20℃.

[0084] Dielectric anisotropy Δε is defined as follows:

[0085] Δε represents the dielectric anisotropy of the nematic liquid crystal composition, Δε = ε ∥ -ε ⊥ , ε ∥ The dielectric constant is ε. ⊥ The perpendicular dielectric constant is used; the measurement method involves filling a nematic liquid crystal composition into a 7-micron left-handed TN cell, measuring at 25°C, and using an LCR meter at 1 kHz and 0.1 V to obtain ε. ⊥ ε was measured at 1kHz and 20V. ∥ .

[0086] The pitch P is defined as follows:

[0087] P = 1 / (c*HTP), where c is the chiral compound content, and HTP is the helical twist constant of the chiral compound. The HTP value is measured by filling a wedge-shaped cell containing an appropriate amount of chiral compound at 25℃, reading the misalignment difference ΔX using a reading microscope, and calculating it using the following formula: HTP = 1 / (c*2*ΔX*tan*1000), tan = 0.0196.

[0088] Referring to Figure 1, the liquid crystal dimming device 100 provided in this application includes a pair of opposing transparent conductive substrates (101A, 101B) and a dimming layer 102 disposed between the transparent conductive substrates. The dimming layer 102 includes a dimming layer material 103, which includes a polymer network 1031 formed from at least one polymerizable monomer and a liquid crystal composition 1032 dispersed in the polymer network. The polymer network is uniformly arranged, and the liquid crystal composition includes an elastic constant modifier. It may also include a plurality of spacers, such as spacers 104, which may exist within the polymer network to help maintain the gap between the opposing transparent conductive substrates. The dimming device includes at least two stable states: a transmitted state that substantially transmits incident light, and a hazy state that substantially scatters incident light. The haze of the transmitted state is not greater than 5%, and the haze of the hazy state is not less than 85%.

[0089] In some embodiments, the uniform alignment is substantially perpendicular to or substantially parallel to the transparent conductive substrate; the liquid crystal in the dimming layer can form a uniform alignment under the interaction of its own elastic properties, alignment conditions, and an applied electric field; in some specific embodiments, the dimming device further includes at least one alignment layer 105 disposed between the transparent conductive substrate and the dimming layer, the alignment layer 105 orienting the liquid crystal molecules substantially parallel to the transparent conductive substrate; in other specific embodiments, it is cured under ultraviolet radiation in the presence of an external electric field, the external electric field promoting the formation of a polymer network perpendicularly aligned to the plane of the transparent conductive substrate (see Figure 1(a)); in some specific embodiments, it is cured under ultraviolet radiation in the presence of zero electric field, the alignment layer promoting the formation of a polymer network parallel to the plane of the transparent conductive substrate (see Figure 1(b)).

[0090] In this application and particularly in the following embodiments, the group structures in the liquid crystal composition are coded and identified; Table 1 shows the group structures and codes used in the liquid crystal composition.

[0091] Table 1. Structure codes of functional groups in liquid crystal compositions

[0092]

[0093] The structure corresponding to "5PPN" according to the naming rules in Table 1 is as follows:

[0094]

[0095] "n=3", according to the naming principle in Table 1, its corresponding structure is: -C3H7.

[0096] To verify the superior technical effect of the technical solution provided in this application, this application provides 7 sets of liquid crystal mixtures as comparative examples and 5 sets of liquid crystal mixtures as embodiments, and these liquid crystal mixtures are made into corresponding liquid crystal dimming devices, and their performance is tested.

[0097] (1) Preparation of liquid crystal mixtures

[0098] According to the following examples and comparative examples, the liquid crystal composition and polymerizable monomer ratios were specified, and the mixture was stirred at 25°C in the dark for 2 hours to obtain a liquid crystal mixture.

[0099] (2) Structure of dimming device

[0100] The bistable liquid crystal dimming device includes a first transparent conductive substrate and a second transparent conductive substrate, which are parallel to each other and arranged opposite to each other to form a liquid crystal cell; a dimming layer is filled in the liquid crystal cell between the first transparent conductive substrate and the second transparent conductive substrate, and the dimming layer includes the liquid crystal mixture described above. The liquid crystal mixture is vacuum-filled into an empty liquid crystal cell manufactured according to various design requirements. The cell formation process is strictly light-protected, and different curing processes are used to polymerize the polymerizable monomers in the liquid crystal composition.

[0101] In the liquid crystal dimming devices of Comparative Examples 1-7 and Examples 1-2, the transparent conductive substrate is ITO transparent glass, the alignment layer is VA type, and alignment is performed using a double-sided rubbing alignment method. In the liquid crystal dimming device of Example 3, the transparent conductive substrate is ITO transparent glass, the alignment layer is VA type, and alignment is performed using a single-sided rubbing alignment method. In the liquid crystal dimming device of Example 4, the transparent conductive substrate is ITO transparent glass, the alignment layer is IPS type, and alignment is performed using top-to-bottom antiparallel rubbing. In the liquid crystal dimming device of Example 5, the transparent conductive substrate is ITO transparent PET, the alignment layer is TN type, and alignment is performed using top-to-bottom antiparallel rubbing.

[0102] (3) Haze measurement method

[0103] After sealing the dimming device, place it at 25℃ for at least 30 minutes in preparation for testing. First, turn on the WGT-S type haze meter and start the test after the light source has stabilized for 30 minutes. Use pulse voltage to drive it to the planar state and the focal conic state respectively. The voltage used to drive it to the planar state is the first voltage, and the voltage used to drive it to the focal conic state is the second voltage. Then measure the transmittance and haze, and observe the phenomenon visually at the same time.

[0104] In the comparative examples and embodiments, the driving voltage mentioned in the parameter list is the first voltage. For ease of explanation, the driving voltage amplitude is the voltage amplitude when switching from any state to the transmission state at an ambient temperature of 25°C and a pulse width of 1s. The fog state was maintained for 16 hours in a small environmental chamber.

[0105] Comparative Example 1

[0106]

[0107] Comparative Example 2

[0108]

[0109] Comparative Example 3

[0110]

[0111] Example 1

[0112]

[0113] Comparative Examples 1-3 and Example 1 were prepared into liquid crystal mixtures according to the corresponding table formulations. These mixtures were stirred at 25°C in the dark for 2 hours and then vacuum-filled into empty liquid crystal cells manufactured according to various design requirements. Curing process: The dimming device was continuously energized at 80V at 25°C. At this point, the liquid crystal molecules were aligned almost perpendicular to the substrate, i.e., in a uniform state. Then, the mixture was placed at a wavelength of 365nm and an intensity of 7-8 mw / cm². 2 Irradiate for 2 minutes under the specified conditions.

[0114] The results showed that, in the dimming device (CELLGAP 15μm), Example 1 improved the haze by 5.22% compared to Comparative Example 1, improved the haze retention for 16 hours by 7.12%, and had a transmittance of <3%. Meanwhile, the dimming device (CELLGAP 15μm) of Example 1 achieved and outperformed the dimming device (CELLGAP 20μm) of Comparative Example 1 in terms of haze and haze stability, while reducing the driving voltage by 20V.

[0115] Comparative Example 2 used the same curing process as Example 1, but because the content of polymerizable monomers exceeded the limits of the present invention, the haze in the permeable state was significantly deteriorated; Comparative Example 3 used the same curing process as Example 1, but because the content of polymerizable monomers was lower than the limits of the present invention, the improvement in haze and stability was not significant.

[0116] Example 2

[0117]

[0118] Example 2: A liquid crystal mixture was prepared according to the formulation in the table, stirred at 25°C in the dark for 2 hours, and then vacuum-filled into an empty liquid crystal cell made according to the design requirements. Curing process: The dimming device was driven to the transmittance state at 80V in an environment of 25°C. At this point, the liquid crystal molecules were basically aligned parallel to the substrate direction, i.e., in a uniform state. After standing for 30 minutes, it was then placed at a wavelength of 365nm and an intensity of 7-8 mw / cm². 2 Irradiate for 2 minutes under the specified conditions.

[0119] The results showed that, in the dimming device (CELLGAP 15μm), the haze of Example 2 was improved by 5.09% compared with that of Comparative Example 1, the haze maintained for 16 hours was improved by 7.00%, and the haze in the transmitted state was <3%. At the same time, the dimming device (CELLGAP 15μm) of Example 2 could achieve the haze and haze stability of the dimming device (CELLGAP 20μm) of Comparative Example 1, while the driving voltage was reduced by 20V.

[0120] Comparative Example 4

[0121]

[0122] Example 3

[0123]

[0124] Comparative Example 4 and Example 3 were prepared into liquid crystal mixtures according to the formulations in the table, stirred at 25°C in the dark for 2 hours, and then vacuum-filled into empty liquid crystal cells made according to the design requirements. Curing process: The dimming device was continuously energized at 80V at 25°C. At this time, the liquid crystal molecules were basically aligned perpendicular to the substrate direction, i.e., in a uniform state. Then, the mixture was placed at a wavelength of 365nm and an intensity of 3-5mw / cm². 2 Conditional irradiation for 2 minutes.

[0125] The results showed that, in the dimming device (CELLGAP 15μm), the haze of Example 3 was 5.11% higher than that of Comparative Example 4, the haze maintained for 16 hours was 7.01% higher, and the haze in the transmitted state was <3%. At the same time, the dimming device (CELLGAP 15μm) of Example 3 could achieve the haze and haze stability of the dimming device (CELLGAP 20μm) of Comparative Example 4, while the driving voltage was reduced by 20V.

[0126] Example 4

[0127]

[0128] Example 4: A liquid crystal mixture was prepared according to the formulation in the table, stirred at 25°C in the dark for 2 hours, and then vacuum-filled into an empty liquid crystal cell made according to the design requirements. Curing process: The device was then driven to the transmittance state at 80V in an environment of 25°C. At this point, the liquid crystal molecules are basically aligned parallel to the substrate direction, i.e., in a uniform state. After standing for 30 minutes, it was then placed at a wavelength of 365nm and an intensity of 3-5mw / cm. 2 Irradiate for 10 minutes.

[0129] The results showed that, in the dimming device (CELLGAP 15μm), the haze of Example 4 was 4.74% higher than that of Comparative Example 4, the haze retention after 16 hours was 6.43% higher, and the haze in the transmitted state was <3%. At the same time, the dimming device (CELLGAP 15μm) of Example 4 could achieve the haze and haze stability of the dimming device (CELLGAP 20μm) of Comparative Example 4, while reducing the driving voltage by 20V.

[0130] Comparative Example 5

[0131]

[0132] Example 5

[0133]

[0134] Comparative Example 5 and Example 5 were prepared into liquid crystal mixtures according to the formulations in the table, stirred at 25°C in the dark for 2 hours, and then vacuum-filled into empty liquid crystal cells made according to the design requirements. Curing process: The dimming device was driven to the transmittance state at 80V in an environment of 25°C. At this point, the liquid crystal molecules were basically aligned parallel to the substrate direction, i.e., in a uniform state. After standing for 30 minutes, the mixture was then placed at a wavelength of 365nm and an intensity of 7-8mw / cm². 2 Conditional irradiation for 2 minutes.

[0135] The results showed that, in the dimming device (CELLGAP 15μm), Example 2 improved the haze by 6.54% compared with Comparative Example 1, improved the haze retention for 16 hours by 9.67%, and had a transmittance of <3%. Meanwhile, the dimming device (CELLGAP 15μm) of Example 5 achieved and outperformed the haze and haze stability of the dimming device (CELLGAP 20μm) of Comparative Example 5, with a 20V reduction in driving voltage.

[0136] Comparative Example 6

[0137]

[0138] Example 6: A liquid crystal mixture was prepared according to the formulation in the table, stirred at 25°C in the dark for 2 hours, and then vacuum-filled into an empty liquid crystal cell made according to the design requirements. At this time, the liquid crystal molecules are in a defective planar state, that is, in a non-uniform state. Curing process: The device was left untreated and allowed to stand at 25°C for 30 minutes, and then placed at a wavelength of 365nm and an intensity of 3-5mw / cm. 2 Irradiate for 10 minutes.

[0139] The results showed that, in the dimming device (CELLGAP 15μm), the haze of Comparative Example 6 was 4.90% higher than that of Comparative Example 4, and the haze was 6.86% higher after 16 hours of haze maintenance. However, the haze in the transmitted state was 7.3%, which did not meet the requirements of this invention.

[0140] Comparative Example 7

[0141]

[0142] Comparative Example 7: A liquid crystal mixture was prepared according to the formulation in the table, stirred at 25°C in the dark for 2 hours, and then vacuum-filled into an empty liquid crystal cell made according to the design requirements. Curing process: The device was placed at 25°C for 30 minutes, and then driven to the Fc state under suitable driving conditions. At this point, the liquid crystal molecules are randomly arranged, i.e., in a non-uniform state. Then, it was placed at a wavelength of 365nm and an intensity of 3-5mw / cm². 2 Irradiate for 10 minutes.

[0143] The results showed that, in the dimming device (CELLGAP 15μm), the haze of Comparative Example 7 was 5.40% higher than that of Comparative Example 4, and the haze was 7.43% higher after 16 hours of haze maintenance. However, the haze in the transmitted state was 11.42%, which did not meet the requirements of this invention.

[0144] Through the above embodiments and comparative examples, it can be seen that the dimming device made of the liquid crystal composition of the present invention can reduce its cell thickness, reduce the driving voltage, and at the same time maintain the high haze and haze stability of the device.

[0145] Although several exemplary embodiments have been described in detail above, the disclosed embodiments are exemplary and not restrictive, and those skilled in the art will readily recognize that many other modifications, alterations, and / or substitutions are possible in the exemplary embodiments without materially departing from the novelty teachings and advantages of this disclosure. Therefore, all such modifications, alterations, and / or substitutions are intended to be included within the scope of this disclosure as defined by the appended claims.

Claims

1. A polymer network-stabilized multistable dimming device, characterized in that, The device includes a pair of opposing transparent conductive substrates and a dimming layer disposed between the transparent conductive substrates. The dimming layer is a liquid crystal layer including a polymer network, wherein the polymer network is uniformly arranged. The dimming device includes at least two stable states: a transmittance state that allows incident light to be substantially transmitted and a hazy state that allows incident light to be substantially scattered. The hazyness of the transmittance state is not greater than 5%, and the hazyness of the hazy state is not less than 85%.

2. The dimming device as described in claim 1, characterized in that, The uniform arrangement is substantially perpendicular to or substantially parallel to the transparent conductive substrate.

3. The dimming device as described in claim 2, characterized in that, The uniform alignment can be achieved by an alignment layer disposed on the inner surface of a transparent conductive substrate.

4. The dimming device according to any one of claims 1-3, characterized in that, The dimming layer comprises a liquid crystal composition and at least one polymerizable monomer. The liquid crystal composition comprises at least one cholesteric liquid crystal composition, at least one initiator, and at least one elastic constant modifier. The polymerizable monomer accounts for 0.5wt%-1.5wt% of the dimming layer, and the liquid crystal composition has Δn≥0.15, Δε≥5, and a helical pitch P of 0.2-2μm.

5. The dimming device as described in claim 4, characterized in that, The elastic constant modifier is selected from at least one of general formula I. in: R1 and R2 each independently represent -H, -F, -Cl, -CN, -NCS, or an alkyl chain with 1-25 carbon atoms, wherein one or more H atoms in the alkyl chain with 1-25 carbon atoms can be independently substituted by a halogen, and one or more non-adjacent -CH2- atoms in the alkyl chain with 1-25 carbon atoms can be independently substituted by -O-, -CH=CH-, -CH=CF-, or -CF=CF-. X is a straight-chain or branched alkylene group with 3-40 C atoms, wherein one or more -CH2- in the straight-chain or branched alkylene group with 3-40 C atoms can be independently replaced by -O-, -CH(F)-, -CH(Cl)- or -CH=CH-, and the substitution does not involve two -O- adjacent to each other or two double bonds adjacent to each other; MG1 and MG2 each independently represent mesocrystalline units; Preferably, the elastic constant modifier accounts for 10wt%-40wt% of the liquid crystal composition. Preferably, the mesocrystalline unit is selected from the group composed of mesocrystalline units of general formula II. in: H1 and H2 each independently represent a ring structure, and H3 is either a single bond or a ring structure, wherein the ring structure is selected freely. 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 and The group consisting of one or more H atoms in the cyclic structure, wherein each H atom can be independently replaced by a halogen, an alkyl group having 1-10 C atoms, or an ester group; Y and Z each independently represent a single bond or an alkyl chain with 1-10 carbon atoms, wherein one or more H atoms in the alkyl chain with 1-10 carbon atoms can be independently substituted by a halogen, and one or more non-adjacent -CH2- atoms in the alkyl chain with 1-10 carbon atoms can be independently substituted by -O-, -COO-, -CH=CH-, -CH=CF-, or -CF=CF-.

6. The dimming device as described in claim 5, characterized in that, The compounds of general formula I are selected from one or more compounds in the group consisting of the following: (NPP5PPN) General Formula I-1; (NPP7PPN) General Formula I-2; (NPP9PPN) General Formula I-3; (NPP11PPN) General Formula I-4; (NPPO5OPPN) General Formula I-5; (NPPO7OPPN) General Formula I-6; (FPP7PPN) General Formula I-7; (FGIP7PGF) General Formula I-8; (FGIPP9PGF) General Formula I-9; (FGIP9PGF) General Formula I-10; (NUIP7PUN) General Formula I-11; (FPP7PPF) General Formula I-12; (FPP9PPF) General Formula I-13; (FPP11PPF) General Formula I-14; (NGIP7PGN) General Formula I-15; (NGIP9PGN) General Formula I-16; (NGIP11PGN) General Formula I-17; (3PP7PP3) General Formula I-18; (3PP9PP3) General Formula I-19; (3PP11PP3) General Formula I-20; (SPP9PPS) General Formula I-21; 7. The dimming device as described in claim 4, characterized in that, The polymerizable monomer is a mono-, di-, or multi-reactive RM material; Preferably, the polymerizable monomer is selected from any one or more of RM257, RM82, and LC242.

8. The dimming device as described in claim 4, characterized in that, The cholesteric liquid crystal composition comprises at least one nematic liquid crystal compound and at least one chiral compound; Preferably, the chiral compound is selected from any one or more of CB15, R(S)5011, R(S)6N, R(S)2011, and R(S)1011.

9. The dimming device as described in claim 4, characterized in that, The initiator is a photoinitiator; Preferably, the photoinitiator is selected from any one or more of 4,4'-bismaleimide diphenylmethane, 1,4-bis(maleimide)butane, 1,8-bis(maleimide)-3,6-dioxaoctane, 1,11-bismaleimide-3,6,9-trioxaundecane, 1,6-di(maleimide)hexane, bismaleimide methyl ether, N-cyclohexylmaleimide, N-phenylmaleimide, N-benzylmaleimide, benzoin methyl ether, benzoin dimethyl ether, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, benzophenone, and phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide; Preferably, the photoinitiator accounts for 0.05wt%-0.2wt% of the liquid crystal composition.

10. A method for preparing a dimming device as described in any one of claims 1-9, comprising: 1) Mixing a liquid crystal composition with a polymerizable monomer to form a liquid crystal mixture; 2) Fill the liquid crystal mixture into the liquid crystal cell; 3) The liquid crystal mixture in the liquid crystal cell is arranged in a uniform manner, wherein the uniform arrangement is a planar texture or a vertical texture; 4) When a planar texture is formed, the polymerizable monomers are polymerized under zero electric field to form the dimming device; when a vertical texture is formed, the polymerizable monomers are polymerized under energized conditions to form the dimming device.

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