A bistable light modulating device
By introducing a liquid crystal composition of a bimecium compound and an oily dye into a dimming device, the problem that existing bistable dimming devices cannot achieve color and electric field-free maintenance is solved, realizing color bistable dimming and improving aesthetics and transparency.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- JIANGSU JICUI INTELLIGENT LCD TECH CO LTD
- Filing Date
- 2019-03-14
- Publication Date
- 2026-07-31
AI Technical Summary
Existing bistable dimming devices cannot achieve color performance, and traditional methods increase cost, thickness, or reduce transparency, and cannot maintain a stable state in the absence of an electric field.
A liquid crystal composition comprising a bimecium compound, a nematic liquid crystal compound, a chiral compound, and an oily dye is used to achieve color bistable state by forming a chiral nematic phase, without requiring an external electric field to maintain the stable state.
It achieves a color bistable dimming effect, maintaining high transparency and haze, while reducing production costs and thickness.
Smart Images
Figure CN117270272B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of liquid crystal-based dimming, and particularly to a bistable dimming device. Background Technology
[0002] Liquid crystal-based dimming devices, which utilize the photoelectric effect, are primarily composed of a transparent substrate and liquid crystal materials. They achieve the switching between full transparency and opacity by controlling the alignment of liquid crystal molecules through an applied electric field. Due to this unique dimming characteristic, liquid crystal-based dimming devices, such as smart glass, are widely used in industries such as construction, home furnishings, and automobiles to adjust light transmittance, increase privacy, and block ultraviolet or infrared rays. Among these, bistable or multistable dimming devices, due to their ability to operate without an electric field and their energy-saving and safety features, have even broader application prospects.
[0003] Currently available bistable dimming devices generally utilize light scattering principles to achieve a hazy, opaque state. However, these devices target full-spectrum scattering, producing scattered light that is either white or near-white. They can only switch between colorless transparency and near-white, failing to achieve color performance, thus reducing their aesthetic appeal and limiting their applications. Most commercially available colored dimming films achieve this by adding dyes to PDLC (Polydioxanone Chromium Carbon) films. However, adding dyes reduces the performance of the dimming film, and PDLC films require an electric field to maintain their stability, which is not energy-efficient. Another solution is to add a colored film to a standard bistable dimming device to achieve color performance. However, the colored film increases light scattering in the transparent state, reducing transparency, and also increases the thickness and manufacturing cost of the dimming device.
[0004] Therefore, there is a need to provide a dimming device that has color performance while achieving bistable operation, and can maintain its original performance, and has a simple manufacturing process and low cost. Summary of the Invention
[0005] To meet the above requirements, the present invention proposes a dimming device, which includes a first transparent conductive substrate, a liquid crystal layer, and a second transparent conductive substrate stacked in sequence. The liquid crystal layer contains a liquid crystal composition, which includes a bimecium compound, a nematic liquid crystal compound, an oily dye, and a chiral compound. The dimming device includes two zero-electric-field stable states: a transmission state in which the transmitted light is essentially directly incident and a fog state in which the transmitted light is essentially scattered.
[0006] The bimesocrystalline compound comprises 14.49% NPP7PPN, 14.49% NPP9PPN, and 14.49% NPP11PPN by mass percentage, while the oily dye accounts for 0.5% of the liquid crystal composition by mass percentage.
[0007] Alternatively, the bimesocrystalline compound comprises 10.99% NPP7PPN, 10.99% NPP9PPN, and 10.99% NPP11PPN by mass percentage, while the oily dye accounts for 0.1% of the mass percentage of the liquid crystal composition.
[0008] The chemical formula of NPP7PPN is:
[0009] ;
[0010] The chemical formula of NPP9PPN is:
[0011] ;
[0012] The chemical formula of NPP11PPN is:
[0013] .
[0014] In some embodiments, the thickness of the liquid crystal layer is 2-60 micrometers. In a preferred embodiment, the thickness of the liquid crystal layer is 5-60 micrometers.
[0015] In a preferred embodiment, the first and second transparent conductive layers each independently include a transparent substrate and a transparent electrode, wherein the transparent electrode is disposed between the transparent substrate and the liquid crystal layer. In some embodiments, the transparent substrate is glass or a polymer material. In some embodiments, the transparent electrode is a carbon-based conductive film, a metal nanowire conductive film, or a metal oxide conductive film.
[0016] In some embodiments, the dimming device further includes at least one alignment layer disposed between the liquid crystal layers and / or between the liquid crystal layers and the first transparent conductive substrate. In a preferred embodiment, the alignment layer is planar or substantially vertically aligned.
[0017] In some embodiments, the bimecium compound accounts for 5% to 50% of the mass percentage of the liquid crystal composition. In a preferred embodiment, the bimecium compound accounts for 15% to 50% of the mass percentage of the liquid crystal composition.
[0018] The bistable dimming device disclosed in this invention can achieve color and zero electric field maintenance by introducing a bimecium compound and an oily dye with a certain solubility in liquid crystal. The bistable dimming device has low transmittance haze and high haze, and can be applied to dimming glass, providing both light transmittance and privacy isolation while also providing aesthetic decoration. Attached Figure Description
[0019] The invention can be better understood by referring to the illustrated description of embodiments thereof, in which:
[0020] Figure 1 This is a schematic diagram of the structure of the dimming device disclosed in this invention;
[0021] Figure 2 This is a schematic diagram illustrating the working principle of the dimming device in two steady states disclosed in this invention.
[0022] Figure 3 This is a schematic diagram of the structure of the dimming device disclosed in this invention;
[0023] Figure 4 This is a schematic diagram of the structure of the dimming device disclosed in this invention, which contains (a) one alignment layer and (b) two alignment layers;
[0024] Figure 5 The absorption spectra of the dimming device prepared according to embodiments of the present invention are in (a) the transmitted state and (b) the fog state;
[0025] Figure 6 The absorption spectra of the dimming device prepared according to embodiments of the present invention are in (a) the transmitted state and (b) the fog state. Detailed Implementation
[0026] 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.
[0027] First refer to Figure 1 The illustration shows a dimming device comprising a first transparent conductive substrate 1, a second transparent conductive substrate 2, and a liquid crystal layer 3 sandwiched between them, wherein the thickness of the liquid crystal layer 3 is 2-60 micrometers. Preferably, the thickness of the liquid crystal layer is 5-60 micrometers. The dimming device has two zero-electric-field stable states: a transmission state in which transmitted light is essentially directly incident, and a hazy state in which transmitted light is essentially scattered.
[0028] The liquid crystal layer 3 contains a liquid crystal composition, which includes a bimectic compound, a nematic liquid crystal compound, a chiral compound, and an oil-based dye. The bimectic compound in the liquid crystal composition is a liquid crystal compound whose molecule contains two mesocrystalline units, meaning it has two groups capable of inducing a liquid crystal phase. In embodiments of the present invention, the bimectic compound accounts for 5% to 50% of the mass percentage of the liquid crystal composition. Preferably, the bimectic compound accounts for 10% to 50% of the mass percentage of the liquid crystal composition. The nematic liquid crystal is a commonly used liquid crystal compound or liquid crystal mixture having a nematic phase, such as 5CB, 2CB, or E7. However, the nematic liquid crystal compound in this invention does not include bimectic compounds capable of inducing a nematic phase. The oil-based dye is an oil-based dye that can absorb specific wavelengths of light in the range of 380 nm to 780 nm and has a certain solubility in liquid crystals. In embodiments of the present invention, oil-based dyes purchased from Dongguan Caihui Chemical Co., Ltd., namely, Scarlet D-001 and Blue D-002, were used. In embodiments of the present invention, the oil-based dye accounts for no more than 5% of the mass percentage of the liquid crystal composition. Preferably, the oil-based dye accounts for 0.01% to 1% of the mass percentage of the liquid crystal composition.
[0029] like Figure 2 As shown, bimectic compounds and nematic liquid crystal compounds can form a chiral nematic phase (i.e., cholesteric phase) under the action of chiral compounds, thus giving the dimming device two stable states: a transmission state in which the transmitted light is essentially directly incident (…). Figure 2 (a) and the hazy state that essentially scatters transmitted light ( Figure 2 (b) In the transmitted state, the cholesteric liquid crystal molecules 301 are substantially parallel to the surface of the dimming device, with their helical axis perpendicular to the surface. This forms a planar texture of the cholesteric liquid crystal, in which transmitted light passes through the dimming device with essentially no effect, maintaining its original incident angle. In the hazy state, the cholesteric liquid crystal molecules form a focal conic texture, where transmitted light is essentially scattered, resulting in a hazy state. Due to its unique elastic coefficient, the bimectic compound can improve the uniformity of the planar alignment of the liquid crystal molecules, reduce texture defects, thereby reducing the haze of the dimming device in the transmitted state and increasing the haze in the hazy state. Meanwhile, the oily dye molecules 302 dispersed in the liquid crystal molecules absorb incident light of a specific wavelength, causing the dimming device to display a specific color, while having essentially no effect on the propagation direction of the transmitted light, thus having essentially no effect on the haze in both the transmitted and hazy states. Furthermore, neither the transmitted nor hazy states of the dimming device require an external electric field to maintain, achieving a stable state with zero electric field. By selecting an appropriate driving method, the dimming device can switch between a specific color-transmitting state and a fog state to achieve the purpose of dimming.
[0030] Reference Figure 3The first transparent conductive substrate 1 and the second transparent conductive substrate 2 may further each include a transparent substrate 11 and a transparent electrode 12, wherein the transparent electrode 12 is disposed on the inner surface of the transparent conductive substrate, that is, the surface where the transparent substrate 11 and the liquid crystal layer 3 contact. The transparent substrate 11 may be transparent glass or a transparent polymer material, such as PET, PEN, PC, PP, PMMA, PBT, PVC, PI, cellulose, etc. However, the present invention is not limited to these, and other materials with acceptable transmittance may also be used. The transparent electrode 12 may be as follows: Figure 3 The thin film shown covers the entire inner surface of the transparent substrate and can be further etched into a specific shape or divided into several corresponding sub-electrodes as needed. Transparent electrodes, based on their conductive materials, can include carbon-based conductive films, metal nanowire conductive films, and metal oxide conductive films. Carbon-based conductive materials mainly include graphene oxide and carbon nanotubes. Metal nanowire conductive films typically use silver or copper nanowires, while metal oxide conductive films are primarily composed of indium tin oxide (ITO), indium oxide, tin oxide, zinc oxide, and a mixture of other metal oxides. In the following embodiments, ITO electrodes are used as the transparent electrodes.
[0031] like Figure 4 As shown, the dimming device may also include an alignment layer 4. Generally, liquid crystal devices align liquid crystal molecules along the rubbing direction by rubbing the substrate surface in contact with the liquid crystal. Adding an alignment layer before rubbing achieves better alignment. The alignment layer 4 can be as follows: Figure 4 As shown in (a), it has only a single layer and is disposed on the inner surface (the surface in contact with the liquid crystal layer 3) of either the first transparent conductive substrate 1 or the second transparent conductive substrate 2; it can also be as follows: Figure 4 As shown in (b), a double-layer alignment layer is formed, located on the inner surfaces of the first transparent conductive substrate 1 and the second transparent conductive substrate 2, respectively, further enhancing the alignment effect. In the following embodiments, a double-layer alignment layer structure is used. The alignment layer 4 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 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), alignment layers are classified into basically planar alignment layers, where the long axis of the liquid crystal molecules on the alignment layer surface is basically parallel to the alignment layer surface, such as IPS, TN, and STN types; or basically perpendicular alignment layers, where the long axis of the liquid crystal molecules is basically perpendicular to the alignment layer surface, such as VA type.
[0032] The structure and optical performance of the dimming device will be described in detail below with reference to specific embodiments. In the following embodiments, the haze in the transmitted and fogged states is measured using a WGT-S type haze meter, while the absorption spectrum of the dimming device can be measured using a commonly used ultraviolet-visible spectrometer.
[0033] For ease of explanation, the functional group structures of the liquid crystal compositions in the following embodiments are represented by the codes listed in Table 1. The structures and codes of the chiral compounds used are also listed in Table 2. All proportions of the liquid crystal compositions are expressed as mass percentages.
[0034] Table 1. Structure codes of liquid crystal compound groups
[0035]
[0036] If n is "3", it means alkyl-C3H7 or spacer group-C3H6-.
[0037] Table 2 Codes and structures of chiral compounds
[0038]
[0039] Comparative Example 1
[0040] In this comparative example, the dimming device includes first and second transparent conductive substrates, two alignment layers, and a liquid crystal layer. The liquid crystal composition in the liquid crystal layer includes nematic liquid crystal compounds and chiral compounds, without the use of bimectic compounds and dyes; its specific formulation is shown in Table 3. The thickness of the liquid crystal layer is 20 micrometers. The transparent conductive substrates are all glass / ITO, and the alignment layer is of the IPS type. A suitable voltage was selected to drive the dimming device to a stable transmitted state and a hazy state, respectively, and its haze was measured. The results were: transmitted state haze 25.6%, haze in the hazy state 64.3%.
[0041] Table 3 Liquid Crystal Composition Formulation
[0042]
[0043] Comparative Example 2
[0044] In this comparative example, the dimming device includes first and second transparent conductive substrates, two alignment layers, and a liquid crystal layer. The liquid crystal composition in the liquid crystal layer comprises a bimectic compound, a nematic liquid crystal compound, and a chiral compound, without the use of dyes. Its specific formulation is shown in Table 4. The thickness of the liquid crystal layer is 20 micrometers. The transparent conductive substrates are all glass / ITO, and the alignment layer is of the IPS type. A suitable voltage was selected to drive the dimming device to a stable transmitted state and a hazy state, respectively, and its haze was measured. The results were: transmitted state haze 0.9%, hazy state haze 90.4%.
[0045] Table 4 Liquid Crystal Composition Formulation
[0046]
[0047] Example 1
[0048] In this embodiment, the dimming device includes first and second transparent conductive substrates, two alignment layers, and a liquid crystal layer. The liquid crystal composition in the liquid crystal layer includes a bimecium compound, a nematic liquid crystal compound, a chiral compound, and an oil-based dye D-001, the specific formulation of which is shown in Table 5. The thickness of the liquid crystal layer is 20 micrometers. The transparent conductive substrates are all glass / ITO, and the alignment layer is of the IPS type. A suitable voltage was selected to drive the dimming device to a stable transmitted state and a hazy state, respectively, and its haze was measured. The results were: transmitted state haze 1.2%, haze state haze 82.4%. Simultaneously, the absorption spectra of the dimming device in the transmitted state and the hazy state were measured, such as... Figure 5 As shown, it absorbs at around 525 nm, which causes the dimming device to appear red in both the transmitted and fogged states.
[0049] Table 5 Liquid Crystal Composition Formulation
[0050]
[0051] Example 2
[0052] In this embodiment, the dimming device includes first and second transparent conductive substrates, two alignment layers, and a liquid crystal layer. The liquid crystal composition in the liquid crystal layer includes a bimectic compound, a nematic liquid crystal compound, a chiral compound, and an oil-based dye D-002, the specific formulation of which is shown in Table 6. The thickness of the liquid crystal layer is 20 micrometers. The transparent conductive substrates are all glass / ITO, and the alignment layer is of the IPS type. A suitable voltage was selected to drive the dimming device to a stable transmitted state and a hazy state, respectively, and its haze was measured. The results were: transmitted state haze 1.2%, haze state haze 89.7%. Simultaneously, the absorption spectra of the dimming device in the transmitted state and the hazy state were measured, such as... Figure 6 As shown, it has multiple absorptions in the 550-650 nm range, which makes the dimming device appear blue in both the transmitted and fogged states.
[0053] Table 6 Liquid Crystal Composition Formulation
[0054]
[0055] Example 3
[0056] In this embodiment, the dimming device includes first and second transparent conductive substrates, two alignment layers, and a liquid crystal layer. The liquid crystal composition in the liquid crystal layer includes a bimectic compound, a nematic liquid crystal compound, a chiral compound, and an oil-based dye D-002, the specific formulation of which is shown in Table 7. The thickness of the liquid crystal layer is 20 micrometers. The transparent conductive substrates are all glass / ITO, and the alignment layer is of type VA. A suitable voltage was selected to drive the dimming device to a stable transmitted state and a hazy state, respectively, and its haze was measured. The results were: transmitted state haze 1.5%, haze in the hazy state 89.4%.
[0057] Table 7 Liquid Crystal Composition Formulation
[0058]
[0059] Example 4
[0060] In this embodiment, the dimming device includes first and second transparent conductive substrates, two alignment layers, and a liquid crystal layer. The liquid crystal composition in the liquid crystal layer includes a bimecium compound, a nematic liquid crystal compound, a chiral compound, and an oil-based dye D-001, the specific formulation of which is shown in Table 8. The thickness of the liquid crystal layer is 20 micrometers. The transparent conductive substrates are all glass / ITO, and the alignment layer is of the IPS type. A suitable voltage was selected to drive the dimming device to a stable transmitted state and a hazy state, respectively, and its haze was measured. The results were: transmitted state haze 1.6%, haze in the hazy state 84.2%.
[0061] Table 8 Liquid Crystal Composition Formulation
[0062]
[0063] Example 5
[0064] In this embodiment, the dimming device includes first and second transparent conductive substrates, two alignment layers, and a liquid crystal layer. The liquid crystal composition in the liquid crystal layer includes a bimecium compound, a nematic liquid crystal compound, a chiral compound, and an oil-based dye D-001, the specific formulation of which is shown in Table 9. The thickness of the liquid crystal layer is 20 micrometers. The transparent conductive substrates are all glass / ITO, and the alignment layer is of the IPS type. A suitable voltage was selected to drive the dimming device to a stable transmitted state and a hazy state, respectively, and its haze was measured. The results were: transmitted state haze 0.58%, haze in the hazy state 80.5%.
[0065] Table 9 Liquid Crystal Composition Formulation
[0066]
[0067] Example 6
[0068] In this embodiment, the dimming device includes first and second transparent conductive substrates, two alignment layers, and a liquid crystal layer. The liquid crystal composition in the liquid crystal layer includes a bimecium compound, a nematic liquid crystal compound, a chiral compound, and an oil-based dye D-002, the specific formulation of which is shown in Table 10. The thickness of the liquid crystal layer is 5 micrometers. The transparent conductive substrates are all glass / ITO, and the alignment layer is of the IPS type. A suitable voltage was selected to drive the dimming device to a stable transmitted state and a hazy state, respectively, and its haze was measured. The results were: transmitted state haze 0.9%, hazy state haze 65.2%.
[0069] Table 10 Liquid Crystal Composition Formulation
[0070]
[0071] Example 7
[0072] In this embodiment, the dimming device includes first and second transparent conductive substrates, two alignment layers, and a liquid crystal layer. The liquid crystal composition in the liquid crystal layer includes a bimecium compound, a nematic liquid crystal compound, a chiral compound, and an oil-based dye D-001, the specific formulation of which is shown in Table 11. The thickness of the liquid crystal layer is 9 micrometers. The transparent conductive substrates are all glass / ITO, and the alignment layer is of the IPS type. A suitable voltage was selected to drive the dimming device to a stable transmitted state and a hazy state, respectively, and its haze was measured. The results were: transmitted state haze 1.7%, haze in the hazy state 80.3%.
[0073] Table 11 Liquid Crystal Composition Formulation
[0074]
[0075] Example 8
[0076] In this embodiment, the dimming device includes first and second transparent conductive substrates, two alignment layers, and a liquid crystal layer. The liquid crystal composition in the liquid crystal layer includes a bimecium compound, a nematic liquid crystal compound, a chiral compound, and an oil-based dye D-001, the specific formulation of which is shown in Table 12. The thickness of the liquid crystal layer is 50 micrometers. The transparent conductive substrates are all glass / ITO, and the alignment layer is of the IPS type. A suitable voltage was selected to drive the dimming device to a stable transmitted state and a hazy state, respectively, and its haze was measured. The results were: transmitted state haze 1.8%, haze in the hazy state 89.0%.
[0077] Table 12 Liquid Crystal Composition Formulation
[0078]
[0079] Example 9
[0080] In this embodiment, the dimming device includes first and second transparent conductive substrates, two alignment layers, and a liquid crystal layer. The liquid crystal composition in the liquid crystal layer includes a bimecium compound, a nematic liquid crystal compound, a chiral compound, and an oil-based dye D-001, the specific formulation of which is shown in Table 13. The thickness of the liquid crystal layer is 20 micrometers. The transparent conductive substrates are all PET / ITO, and the alignment layer is of the IPS type. A suitable voltage was selected to drive the dimming device to a stable transmitted state and a hazy state, respectively, and its haze was measured. The results were: transmitted state haze 1.3%, haze in the hazy state 86.5%.
[0081] Table 13 Liquid Crystal Composition Formulation
[0082]
[0083] Through the above embodiments and comparative examples, it can be seen that the dimming device of the present invention can achieve zero electric field stable transmission state and fog state, and has low transmission state haze and high fog state haze. At the same time, it can achieve color bistable state, thereby further increasing aesthetics on the basis of high light transmittance and privacy isolation.
[0084] 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 bistable dimming device, comprising a first transparent conductive substrate, a liquid crystal layer, and a second transparent conductive substrate stacked sequentially, wherein the liquid crystal layer comprises a liquid crystal composition, the liquid crystal composition comprising a bimecium compound, a nematic liquid crystal compound, an oily dye, and a chiral compound, wherein the dimming device comprises two zero-electric-field stable states: a transmission state in which transmitted light is substantially directly incident and a hazy state in which transmitted light is substantially scattered. The bimesocrystalline compound comprises 14.49% NPP7PPN, 14.49% NPP9PPN, and 14.49% NPP11PPN by mass percentage, while the oily dye accounts for 0.5% of the liquid crystal composition by mass percentage. Alternatively, the bimesocrystalline compound comprises 10.99% NPP7PPN, 10.99% NPP9PPN, and 10.99% NPP11PPN by mass percentage, while the oily dye accounts for 0.1% of the mass percentage of the liquid crystal composition. The chemical formula of NPP7PPN is: ； The chemical formula of NPP9PPN is: ； The chemical formula of NPP11PPN is: 。 2. The dimming device as claimed in claim 1, wherein the thickness of the liquid crystal layer is 2-60 micrometers.
3. The dimming device as claimed in claim 1, wherein the first transparent conductive substrate and the second transparent conductive substrate each independently include a transparent substrate and a transparent electrode, wherein the transparent electrode is disposed between the transparent substrate and the liquid crystal layer.
4. The dimming device as described in claim 3, wherein the transparent substrate is glass or a polymer material.
5. The dimming device as described in claim 3, wherein the transparent electrode is a carbon-based conductive thin film, a metal nanowire conductive thin film, or a metal oxide conductive thin film.
6. The dimming device as claimed in claim 1, wherein the dimming device further comprises at least one alignment layer, the alignment layer being disposed between the first transparent conductive substrate and the liquid crystal layer and / or between the second transparent conductive substrate and the liquid crystal layer.
7. The dimming device as claimed in claim 6, wherein the alignment layer is planar or substantially vertically aligned.