Dye liquid crystal dimming device

Abstract

The invention provides a dye liquid crystal dimming device which comprises a pair of transparent conductive base layers and a dye liquid crystal layer arranged between the transparent conductive base layers, and the dye liquid crystal layer is filled with at least one cholesteric liquid crystal composition, at least one elastic constant regulator and at least one dichroic dye; the dye liquid crystal layer has at least three states under an applied voltage, namely a transparent state in which incident light is transmitted to the greatest extent, a dark state in which the incident light is basically transmitted and absorbed, and a shielding state in which the incident light is basically absorbed and scattered, the dark state is still basically stable after the voltage is withdrawn, and the shielding state is still stable after the voltage is withdrawn. The transparent state and the shielding state need to be basically stable by continuously applying voltage; according to the liquid crystal dimming device, the elastic constant regulator is further added into the liquid crystal mixture, so that a dark-state non-uniform texture is eliminated, and meanwhile, the contrast ratio of the device is improved.

Description

Technical Field

[0001] The present invention relates to the field of liquid crystal optoelectronic devices, and particularly to a dye liquid crystal dimming device capable of simultaneously performing brightness adjustment and privacy protection. Background Art

[0002] As a new dimming technology, dimming devices are increasingly widely used in the fields of architecture and transportation. They can control the propagation of light through methods such as electro-control, temperature-control, and pressure-control, and thus are applied to various fields. Common dimming device technologies mainly include Polymer Dispersed Liquid Crystal (PDLC) dimming technology, dye liquid crystal dimming technology, SPD dimming technology, EC electrochromic technology, and bistable dimming technology. Among them, PDLC dimming technology and bistable dimming technology have privacy protection functions. The traditional PDLC dimming technology has a high side-viewing haze and does not have the ability to adjust brightness, which limits its application. The emerging dye PDLC dimming technology is limited by contrast and dye reliability, and has only two display states. When in the dark state, it is impossible to clearly see the outside, which limits its application.

[0003] Currently, SPD, EC, GHLC and other continuously variable brightness dimming devices and PDLC devices can be combined in structure to achieve brightness adjustment and privacy protection, but the yield of the double-cell structure is low and the cost is high. In addition, the contrast of a conventional single-cell GHLC is relatively low. Generally, multiple cells are stacked or polarizing films are pasted to improve the contrast, but there are also the disadvantages of the above device combination structures. To improve the contrast, cholesterol ester liquid crystals can be used, or chiral agents can be added to conventional GHLC liquid crystals, so that the liquid crystal molecules form a helical twisted structure in the dark state, and can simultaneously absorb light parallel and perpendicular to its vibration direction incident thereon. At this time, the liquid crystal molecules are arranged in a planar texture state in the dark state and in a vertical texture state in the transparent state. However, at this time, more oil lines can be seen in the microscopic state of the planar texture state, and the macroscopic state of the device shows non-uniform haze. Even if the Δn of the liquid crystal composition is reduced to a sufficiently low level, the planar oil lines cannot be eliminated, resulting in non-uniformity and the defect of insufficient clarity when viewed.

[0004] Therefore, there is a need for a safe and reliable dye liquid crystal dimming device that can simultaneously perform brightness adjustment, privacy protection, and has a high contrast, uniform bright and dark states, and low haze in a single-cell device.

[0005] Problems to be Solved by the Invention

[0006] The present invention aims to improve the above existing problems and provides a liquid crystal dimming device that can achieve a transparent state, a dark state, and a shielding state and can switch between these three states, and at the same time, the dimming device has a good contrast.

[0007] Methods for Solving the Problems

[0008] In order to solve the above problems, the inventors of the present invention have found that in a cholesteric liquid crystal system, by adjusting the helix pitch Pitch, adding an elastic constant regulator, and in the presence of a dichroic dye, a desired contrast and the haze of the transparent state and the dark state can be imparted to a dimming device in a single cell device without a polarizer, thereby completing the present invention and broadening the application scope of the dimming device. That is to say, the present invention provides the following solutions.

[0009] A liquid crystal dimming device, including a dye liquid crystal dimming device, characterized in that it includes a pair of oppositely arranged transparent conductive substrates and a dye liquid crystal layer disposed between the transparent conductive substrates. The dye liquid crystal layer is filled with a liquid crystal mixture, and the liquid crystal mixture includes at least one cholesteric liquid crystal composition, at least one elastic constant regulator, and at least one dichroic dye; the dye liquid crystal layer changes the arrangement state of the liquid crystal molecules in the dye liquid crystal layer under the applied voltage, so that the dye liquid crystal layer has at least three states, a transparent state in which incident light is maximally transmitted, a dark state in which incident light is basically transmitted and absorbed, and a shielding state in which incident light is basically absorbed and scattered. Among them, the dark state remains basically stable after the voltage is removed, and the transparent state and the shielding state need to continuously apply voltage to maintain basic stability.

[0010] Further, the Δn of the liquid crystal mixture is ≤0.15.

[0011] Further, the haze of the transparent state is not greater than 2%, and the haze of the dark state is not greater than 10%.

[0012] Further, the elastic constant regulator accounts for 1 wt% - 50 wt% of the liquid crystal mixture.

[0013] Further, the elastic constant regulator accounts for 1 wt% - 30 wt% of the liquid crystal mixture; preferably, the elastic constant regulator accounts for 1 wt% - 20 wt% of the liquid crystal mixture.

[0014] Further, the elastic constant regulator includes a bis-mesogenic compound.

[0015] Further, the bis-mesogenic compound is a liquid crystal compound containing two mesogenic units in the molecule, selected from the general formula I:

[0016] RI-MGI-X-MG2-R2 I:

[0017] Wherein, R1 and R2 each independently represent -H, -F, -Cl or an alkyl group having 1 to 25 carbon atoms, wherein one or more H atoms in the alkyl group having 1 to 25 carbon atoms may each independently be substituted by a halogen, and one or more non-adjacent -CH2- in the alkyl group having 1 to 25 carbon atoms may each independently be replaced by -O-, -CH=CH-, -CH=CF- or -CF=CF-;

[0018] X is a straight-chain or branched-chain alkylene group having 3 to 40 carbon atoms, wherein one or more -CH2- in the straight-chain or branched-chain alkylene group having 3 to 40 carbon atoms may each independently be replaced by -O-, -CH(F)-, -CH(Cl)- or -CH=CH-, and the replacement mode does not include two -O- adjacent to each other or two double bonds adjacent to each other;

[0019] MG1 and MG2 each independently represent a mesogenic unit;

[0020] Preferably, X is -(CH2) n -, -O(CH2) n O-, and n is an odd number from 3 to 40.

[0021] Furthermore, the mesogenic unit is selected from the group consisting of mesogenic units of general formula II:

[0022] -H1-Y-H2-Z-H3 II:

[0023] Wherein:

[0024] H1 and H2 each independently represent a cyclic structure, H3 is a single bond or a cyclic structure, and the cyclic structure is selected from the group consisting of wherein one or more H atoms in the cyclic structure may each independently be substituted by a halogen, an alkyl group having 1 to 10 carbon atoms or an ester group;

[0025] Y and Z each independently represent a single bond or an alkyl group having 1 to 10 carbon atoms, wherein one or more H atoms in the alkyl group having 1 to 10 carbon atoms may each independently be substituted by a halogen, and one or more non-adjacent -CH2- in the alkyl group having 1 to 10 carbon atoms may each independently be replaced by -O-, -COO-, -CH=CH-, -CH=CF- or -CF=CF-;

[0026] Preferably, Y and Z represent single bonds.

[0027] Furthermore, the dichroic dye is selected from at least one of azo dyes, anthraquinone dyes, benzothiadiazole dyes or perylene dyes.

[0028] Furthermore, the dichroic dye is a single component or a mixture of at least two components, and the absorption peak of each component is at any wavelength between 300 nm and 2500 nm.

[0029] Furthermore, the cholesteric liquid crystal composition includes at least one nematic liquid crystal compound and at least one chiral compound.

[0030] Furthermore, the chiral compound accounts for 0.05 wt% - 20 wt% of the liquid crystal mixture.

[0031] Furthermore, the chiral compound is selected from any one or more of CB15, S(R)811, S(R)5011, S(R)1011, S(R)2011, R6N.

[0032] Furthermore, the liquid crystal mixture further includes at least one polymerizable monomer and at least one initiator.

[0033] Furthermore, the transparent conductive base layer includes a first transparent conductive base layer and a second transparent conductive base layer. The first transparent conductive base layer includes a first transparent substrate and a first transparent conductive layer disposed on one side adjacent to the dye liquid crystal layer, and the second transparent conductive base layer includes a second transparent substrate and a second transparent conductive layer disposed on one side adjacent to the dye liquid crystal layer.

[0034] Furthermore, the first transparent substrate and / or the second transparent substrate is flat glass, tempered glass, semi-tempered glass, float glass, or a plastic substrate film.

[0035] Furthermore, the plastic substrate film is selected from at least one of PET film, PI film, PTFE film, PP film, PC film, PVC film, PE film, PS film, PA film, PEN film, PMMA film, PBT film.

[0036] Furthermore, the material of the first transparent conductive layer and / or the second transparent conductive layer is any one of a metal oxide thin film, a metal nanowire conductive thin film, a metal grid, and a carbon-based conductive thin film.

[0037] Furthermore, at least one of the first and second transparent conductive layers is composed of at least one conductive region that can independently apply a voltage.

[0038] Furthermore, a first alignment layer and / or a second alignment layer is also provided on one side of the first transparent conductive base layer and / or the second transparent conductive base layer adjacent to the dye liquid crystal layer.

[0039] Further, the material of the first alignment layer and / or the second alignment layer is any one of polyimide, polyvinyl alcohol, polyester, epoxy resin, polyurethane, polysilane, polystyrene and its derivatives.

[0040] Further, the alignment method of the first alignment layer and / or the second alignment layer is any one of rubbing alignment method, photoalignment method, oblique evaporation method, and LB film method.

[0041] Further, the alignment type of the first alignment layer and / or the second alignment layer is VA type.

[0042] Further, the operation for applying alignment to the first alignment layer and / or the second alignment layer is any one of spin coating method, dipping method, letterpress printing method, spraying method, or slot coating method.

[0043] Further, a spacer material is provided between the first transparent conductive substrate and the second transparent conductive substrate. The spacer material is selected from at least one of resin, glass fiber, and inorganic material, and the shape of the spacer material can be spherical, rod-shaped, or a mixed shape.

[0044] Further, the thickness of the dye liquid crystal layer is 1 - 60 μm.

[0045] Further, the transparent state is obtained by continuously applying a first voltage, and the shielding state is obtained by continuously applying a second voltage.

[0046] Further, the second voltage is less than the first voltage.

[0047] The beneficial effects of the present application are as follows: The present application provides a liquid crystal dimming device. An elastic constant regulator is further added to the liquid crystal mixture to reduce the difference between the bending elastic constant K33 and the twist elastic constant K22 of the liquid crystal mixture, eliminate the non-uniform texture in the dark state, and enable the liquid crystal molecules to quickly form a helical structure arrangement substantially parallel to the substrate direction after the transparent state is powered off. At the same time, the dichroic dye aligns with the liquid crystal molecules, and has double absorption for light incident perpendicular and parallel to its vibration direction, improving the device contrast, while weakening or eliminating the oil lines and having low scattering.

[0048] Other features and advantages of the present invention will be described in detail in the subsequent specific implementation part. Description of the Drawings

[0049] Figure 1 Including the microscope pictures of Comparative Example 3 ( Figure 1 (a)), Example 2 ( Figure 1 (b)), and Example 3 ( Figure 1 (c)) when driven to the dark state for 1 minute;

[0050] Figure 2 are respectively the microscope pictures of Comparative Example 3 ( Figure 2 (a)), Example 2 ( Figure 2 (b)), and Example 3 ( Figure 2 (c)) when driven to the dark state for 2 min. Detailed implementation manners

[0051] In the following description, for the purpose of explanation and illustration to have a comprehensive understanding of the present invention, a large number of specific details are set forth. However, it is obvious that the present invention can be implemented without these specific details for those skilled in the art. In other examples, well-known structures and devices are shown in block diagrams. In this regard, the illustrative example embodiments given are only for illustration and do not limit the present invention. Therefore, the protection scope of the present invention is not limited by the above specific implementation manners, but only by the scope of the appended claims.

[0052] Terms and Definitions

[0053] It should be understood that the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of the said features. In the description of the present application, "a plurality of" means two or more unless otherwise specifically defined.

[0054] Throughout the description of this specification and the claims, "comprising" and "including" and variations of these descriptions, such as "comprises" and "comprising", mean "including but not limited to" and are not intended to exclude other components.

[0055] The terms "liquid crystal", "mesophase", and "mesogenic compound" refer to compounds that can exist as a mesophase or particularly as a liquid crystal phase under suitable temperature, pressure, and concentration conditions.

[0056] The term "mesogen" is known to those skilled in the art and includes rod-shaped, disc-shaped, flat-plate-shaped, and banana-shaped structures. Usually, a flexible side chain surrounds the middle hard core. The anisotropy of its shape is the basis for the formation of the liquid crystal phase. This structure has the ability to induce (LC) phase behavior and does not necessarily show an LC phase itself.

[0057] The term "Δn" is the optical anisotropy of a nematic liquid crystal composition or a nematic liquid crystal compound, Δn = n e -n o , n e is the extraordinary light refractive index, n ois the refractive index of ordinary light, measured by an Abbe refractometer. Test conditions: sodium lamp light source wavelength 589 nm, measurement temperature 20 °C.

[0058] The term "P" is the pitch P (Pitch), P = 1 / (c * HTP), where c is the content of the chiral compound and the HTP value is the helical twist constant of the chiral compound. The method for measuring the HTP value is to fill a wedge cell with a liquid crystal containing an appropriate content of the chiral compound, measure the temperature at 25 °C, and use a reading microscope to read the disclination line difference ΔX. It is calculated by the following formula: HTP = 1 / (c * 2 * ΔX * tan * 1000), where tan = 0.0196.

[0059] The term "contrast ratio" is defined as the ratio of the transmittance in the transparent state to the transmittance in the dark state. Generally, it represents the legibility of the displayed information (images, characters, etc.).

[0060] Detailed Description

[0061] First, the liquid crystal dimming device provided by the present application includes a pair of oppositely arranged transparent conductive base layers and a dye liquid crystal layer disposed between the transparent conductive base layers. The dye liquid crystal layer is filled with a liquid crystal mixture. Specifically, the transparent conductive base layer includes a first transparent conductive base layer and a second transparent conductive base layer. The first transparent conductive base layer includes a first transparent substrate and a first transparent conductive layer disposed on one side adjacent to the liquid crystal layer, and the second transparent conductive base layer includes a second transparent substrate and a second transparent conductive layer disposed on one side adjacent to the dye liquid crystal layer. Further, the liquid crystal mixture includes at least one cholesteric liquid crystal composition, at least one elastic constant regulator, and at least one dichroic dye; the dye liquid crystal layer changes the arrangement state of the liquid crystal molecules in the dye liquid crystal layer under the applied voltage, so that the dye liquid crystal layer has at least three states: a transparent state that maximally transmits incident light, a dark state that basically transmits and absorbs incident light, and a shielding state that basically absorbs and scatters incident light. Among them, the dark state remains basically stable after the voltage is removed, and the transparent state and the shielding state need to continuously apply voltage to maintain basic stability.

[0062] A cholesteric liquid crystal composition, a bis-mesogenic compound, and dichroic dye molecules are mixed and dissolved in the liquid crystal mixture. Among them, the dichroic dye can be selected and used as a conventional dye that orients according to the orientation state of the liquid crystal compound due to the so-called guest-host effect, to achieve the absorption of incident light and the anisotropy of the absorption coefficient.

[0063] The state of the cholesteric liquid crystal is mainly determined by the elastic energy of the liquid crystal, the interfacial anchoring, and the applied electric field. By applying an electric field, the liquid crystal can be switched from one state to another. When the voltage applied to the first transparent conductive layer and the second transparent conductive layer is removed, the liquid crystal molecules form a helical twisted structure. The liquid crystal molecules are arranged approximately parallel to the upper and lower transparent conductive substrates. At the same time, the dichroic dye follows the arrangement of the liquid crystal molecules. The absorption of the dye-liquid crystal layer for polarized light whose polarization rotation direction is basically consistent with the direction of the liquid crystal helical structure is greater than that for polarized light rotating in the opposite direction. Therefore, the transmitted light has a certain polarization rotation characteristic. At the same time, due to the basically ordered arrangement of the liquid crystal molecules, the dye-liquid crystal layer has low light scattering for the incident light, and the dimming device forms a dark state in which the incident light is basically transmitted and absorbed.

[0064] Specifically, the orientation characteristic of the dichroic dye following the liquid crystal molecules is represented by an order parameter. The order parameter of the dichroic dye is related not only to the structure of the dye itself but also to the properties of the host liquid crystal. Generally speaking, the higher the order parameter of the dichroic dye, the higher the orderliness of the orientation arrangement following the liquid crystal. However, there is a certain inclination angle of the liquid crystal molecules relative to the conductive layer. In addition, the order parameter of the dichroic dye in the liquid crystal is <1. Therefore, the dichroic dye cannot be completely perpendicular or parallel to the transparent substrate in the transparent state. Therefore, in fact, there is still some weak absorption even in the high-definition vertical state. Generally speaking, the larger the order parameter, the higher the contrast between the vertical state and the planar state or the focal conic state. Therefore, in order to obtain a higher contrast, dichroic dyes with high order parameters are generally selected. At the same time, the solubility, extinction coefficient, photothermal stability, and resistivity of the dichroic dye in the host liquid crystal should also be considered. For the cholesteric liquid crystal material, K33 / K22 > 2, which will cause defects in the planar state of the dimming device. In order to obtain a lower haze in the planar state and a lower driving voltage, it is inclined to make the △n of the liquid crystal system low enough. Under the condition of appropriate contrast, the Pitch should be as large as possible. However, even though the △n of the liquid crystal system is reduced to be low enough, when the device is driven to the dark state, more oil line textures can still be observed under the microscope, and macroscopically, there is a visually visible non-uniform haze. The double mesogenic compound is a compound with two mesogenic units and has an extremely low bending elastic constant K33, showing a "banana" bend. In the specific embodiments of the present application, when an appropriate content is added, the difference between K33 and K22 of the liquid crystal mixture can be adjusted not to exceed 30%, thereby weakening or eliminating the oil lines in the planar state, obtaining a uniform planar state, further reducing the haze in the dark state, and improving the contrast.

[0065] When any form of voltage is applied to the dye - liquid crystal layer, the voltage parameters depend on the cell thickness, the pitch of the helix, the dielectric anisotropy, and its elastic constants. When the voltage amplitude is high enough, the liquid - crystal molecules are arranged in a direction approximately perpendicular to the direction of the applied electric field. At this time, the liquid - crystal molecules unwind the helix and form a field - induced nematic phase. At the same time, the arrangement of the dye molecules is relatively highly ordered. The dye - liquid crystal layer has extremely low absorption and extremely low scattering for the light incident thereon, making the liquid - crystal dimming device present a transparent state mainly characterized by light transmission; in some embodiments, a stable and maintained transparent state can be obtained by applying a first voltage between the first transparent conductive layer and the second transparent conductive layer.

[0066] Within a certain range, due to the relatively strong torque and elastic action of the liquid - crystal molecules, the application of an external electric field can cause the dye - liquid crystal layer to form multiple molecular domains with disordered orientations. Within each molecular domain, the liquid - crystal molecules still have a basically ordered helical arrangement, while the orientations between the molecular domains are basically disordered. In some embodiments, the Δn of the liquid - crystal mixture can cover any Δn range including positive - nematic liquid - crystal compositions, and at the same time, larger and smaller pitches of the liquid - crystal mixture are allowed. In a preferred technical solution of the present invention, the Δn of the nematic liquid - crystal composition is ≤0.15. The larger the Δn, the higher the scattering haze. To reduce the haze in the dark state, Δn should be appropriately small. However, even if Δn is small enough, the oily - line texture caused by molecular orientation in the dark state cannot be eliminated. By adding an elastic - constant regulator, the oily lines can be weakened or eliminated. Especially when Δn is appropriately small, adding a small amount of the elastic - constant regulator can weaken or eliminate the oily lines and obtain a uniformly low - haze dark state. Therefore, a shielding state with a stably maintained haze can be obtained by applying a second voltage between the first transparent conductive layer and the second transparent conductive layer, where the second voltage is lower than the above - mentioned first voltage. As an example of an implementable dimming device, a device that is in a dark state in the initial state and switches to a transparent state and / or a shielding state according to the voltage applied at the same or different frequencies can be used. To obtain a reproducible haze in the shielding state, the preferred treatment method is that the state of the device before applying the second voltage should be in the same or an approximate state, which can be obtained by experiencing the same time interval after the first voltage is cut off.

[0067] In the following embodiments, each component used can be synthesized by known methods or obtained through commercial channels. These synthesis techniques are conventional, and each of the obtained liquid - crystal compounds meets the standards of electronic compounds after testing.

[0068] In an embodiment of the present invention, the cholesteric liquid crystal composition comprises at least one nematic liquid crystal compound and at least one chiral compound. Among them, at least one nematic liquid crystal compound forms a nematic liquid crystal composition, which is a conventional positive nematic liquid crystal composition with Δε>0. The chiral agent is selected from any commercially available chiral compound. In some embodiments, it is selected from R5011 and CB15. The parameter tables of the nematic liquid crystal compositions used in some embodiments are as follows, and X12 commercially available from BASF is prepared as a dichroic dye. At the same time, the group structures in the elastic constant regulator are code-identified; Table 2 shows the group structures and codes of the elastic constant regulator for the liquid crystal mixture.

[0069] Table 1 Parameter Table of Positive Nematic Liquid Crystal Composition

[0070] Encoding Source △n Cp (°C) SVH3110 - 100 Xianhua 0.15 93.1 SVH7110 - 100 Xianhua 0.10 90.4 3CCV Jiangsu Hecheng 0.04 -

[0071] Table 2 Group Structure Codes of Elastic Constant Regulator

[0072]

[0073] Among them, for "NPP7PPN", according to the naming principle in Table 1, its corresponding structure is:

[0074]

[0075] To verify that the technical solution provided by this application has excellent technical effects, this application provides 6 groups of liquid crystal mixtures as examples and 6 groups of liquid crystal mixtures as comparative examples, and makes these liquid crystal mixtures into corresponding liquid crystal dimming devices and tests their performance.

[0076] (1) Preparation of Liquid Crystal Mixture

[0077] Prepare the liquid crystal mixtures specified in Examples 1-6 and Comparative Examples 1-6 according to the weight percentage numbers of the compounds listed in Table 3. After mixing the components, stir them in the dark at 25°C for 2 h to obtain the liquid crystal mixture after mixing.

[0078] Table 3 Composition and Ratio of Liquid Crystal Mixture

[0079]

[0080]

[0081] (2) Structure of Dimming Device

[0082] The above liquid crystal dimming device includes a first transparent conductive substrate layer and a second transparent conductive substrate layer. The first transparent conductive substrate layer and the second transparent conductive substrate layer are arranged parallel and opposite to each other to form a liquid crystal cell; a dye liquid crystal layer filled in the liquid crystal cell between the first transparent conductive substrate and the second transparent conductive substrate, and the dye liquid crystal layer includes the liquid crystal mixture shown in Table 3. Among them, the liquid crystal mixture is poured into an empty liquid crystal cell fabricated according to various design requirements by a vacuum method, and the cell formation process is strictly protected from light. Specifically, the transparent substrate of the dimming devices in each embodiment and the comparative example is flat glass, the cell thickness is 10 μm, and the alignment mode is up-down reverse parallel alignment. At the same time, the substrate type, cell thickness, and alignment mode can be flexibly adjusted.

[0083] (3) Transmittance and haze evaluation

[0084] After the dimming device is sealed, the dimming device is placed at a constant temperature of 25 °C for more than 30 min for preparation of testing. The transmittance / haze is measured by a WGT-S type transmittance / haze meter of Shanghai Yidian Wuguang, and the optical anisotropy Δn is measured by an Abbe refractometer at 20 °C. Table 3 shows the composition of each liquid crystal mixture and the test results of its performance parameters.

[0085] The dimming device of Comparative Example 1 is a conventional GHLC single-cell dimming device, which has low haze in both the transparent state and the dark state, and has no shielding state. In addition, because it can only absorb light in one vibration direction incident thereon in the dark state, the contrast ratio is low.

[0086] The dye liquid crystal layer of the dimming device of Comparative Example 2 adds a chiral agent on the basis of Comparative Example 1, and the liquid crystal molecules form a helical structure arrangement. The dichroic dye follows the orientation of the liquid crystal molecules. At this time, the dimming device absorbs light both perpendicular and parallel to the vibration direction of the incident light, resulting in a significant increase in the contrast ratio of the dimming device. At the same time, there is at least one energized shielding state in this conditional device, which can play a certain privacy protection effect. However, the orientation is not uniform in the dark state, the haze is high, and the haze cannot be stably maintained, which greatly affects the application experience.

[0087] The dye liquid crystal layer of the dimming device of Example 1 further adds an elastic constant regulator on the basis of Comparative Example 2, and the liquid crystal molecules form a helical structure arrangement approximately parallel to the substrate direction, and the orientation is relatively uniform. It can be observed under a microscope that Example 1 has significantly fewer oil line textures than Comparative Example 2, the haze is significantly reduced, the contrast ratio is significantly increased, the dark state haze is reduced from 42.30% of Comparative Example 2 to 6.63%, and the contrast ratio is increased from 8.06 of Comparative Example 2 to 16.68. At the same time, it contains a shielding state, and the haze of the shielding state is not less than 30%.

[0088] In Example 2 and Example 3, 5% and 20% of elastic constant regulators were respectively added on the basis of Comparative Example 3, so that the dark state haze of Example 2 was reduced from 36.23% of Comparative Example 3 to 14.48%, and the dark state haze of Example 3 was reduced from 36.23% of Comparative Example 3 to 2.74%. At the same time, microscope pictures of Comparative Example 3, Example 2 and Example 3 at 1 minute and 2 minutes after being driven to the dark state were provided, showing that the oil line defects in Example 2 were weakened in the dark state compared with Comparative Example 3, and the oil lines were basically eliminated in Example 3, which corresponded to the macroscopic haze values.

[0089] The liquid crystal compositions of the light modulating devices in Comparative Example 4, Comparative Example 5 and Comparative Example 6 had a relatively low Δn compared with Comparative Example 2. As Δn decreased, the scattering weakened and the dark state haze gradually decreased, but the haze still remained above 5%. It was found by microscopic observation that the oil line planar texture was presented in the dark state. Example 4, Example 5 and Example 6 were obtained by respectively adding an appropriate amount of elastic constant regulator to Comparative Example 4, Comparative Example 5 and Comparative Example 6. It can be seen from the results in Table 3 that Example 4 reduced the dark state haze from 23.65% of Comparative Example 4 to 2.29%, and the contrast ratio was increased from 10.35 of Comparative Example 4 to 16.11; Example 5 reduced the dark state haze from 19.15% of Comparative Example 5 to 0.90%, and the contrast ratio was increased from 11.44 of Comparative Example 5 to 21.27; Example 6 reduced the dark state haze from 9.25% of Comparative Example 6 to 0.53%, and the contrast ratio was increased from 11.44 of Comparative Example 6 to 21.27. At the same time, Example 4, Example 5 and Example 6 also each contained at least one low-voltage shielding state, and the haze of the shielding state was not less than 30%.

[0090] Although several exemplary embodiments have been described in detail above, the disclosed embodiments are merely exemplary and not restrictive, and those skilled in the art will readily realize that many other modifications, changes and / or substitutions are possible in the exemplary embodiments without substantially departing from the novel teachings and advantages of the present disclosure. Therefore, all such modifications, changes and / or substitutions are intended to be included within the scope of the present disclosure as defined by the appended claims.

Claims

1. A dye liquid crystal dimming device, characterized in that: The invention comprises a pair of relatively transparent conductive substrates and a dye liquid crystal layer arranged between the transparent conductive substrates, wherein the dye liquid crystal layer is filled with a liquid crystal mixture, wherein the liquid crystal mixture comprises at least one cholesteric liquid crystal composition, at least one elastic constant regulator and at least one dichroic dye; when a voltage is applied to the dye liquid crystal layer, the arrangement state of the liquid crystal molecules in the dye liquid crystal layer is changed, so that the dye liquid crystal layer has at least three states, namely, a transparent state for maximally transmitting incident light, a dark state for substantially transmitting and absorbing incident light, and a shielding state for substantially absorbing and scattering incident light, wherein the dark state remains basically stable after the voltage is removed, and the transparent state and the shielding state require continuous application of voltage to remain basically stable.

2. The dimming device according to claim 1, characterized in that: The Δn of the liquid crystal mixture is ≤0.

15.

3. The dimming device according to claim 1, characterized in that: The haze of the transparent state is not greater than 2%, and the haze of the dark state is not greater than 10%.

4. The dimming device according to claim 1, characterized in that: The elastic constant adjuster accounts for 1 wt% to 50 wt% of the liquid crystal mixture.

5. The dimming device according to claim 4, characterized in that: The elastic constant regulator accounts for 1wt%-30wt% of the liquid crystal mixture; Preferably, the elastic constant adjuster accounts for 1 wt%-20 wt% of the liquid crystal mixture.

6. The dimming device according to claim 1, characterized in that: The elastic constant adjuster includes a bimesogenic compound.

7. The dimming device according to claim 6, characterized in that: The bimesogenic compound is a liquid crystal compound containing two mesogenic units in the molecule, selected from the general formula I: R1-MG1-X-MG2-R2 I; wherein R1 and R2 each independently represent -H, -F, -Cl or a chain alkyl group having 1 to 25 carbon atoms, wherein one or more H atoms in the chain alkyl group having 1 to 25 carbon atoms may each independently be substituted by halogen, and one or more non-adjacent -CH2- in the chain alkyl group having 1 to 25 carbon atoms may each independently be substituted by -O-, -CH=CH-, -CH=CF- or -CF=CF-; X is a straight or branched alkylene group having 3 to 40 carbon atoms, wherein one or more -CH2- in the straight or branched alkylene group having 3 to 40 carbon atoms can be independently replaced by -O-, -CH(F)-, -CH(Cl)- or -CH=CH-, and the replacement does not include two -O- adjacent to each other or two double bonds adjacent to each other; MG1 and MG2 each independently represent a mesogen; Preferably, X is -(CH2) n -、-O(CH2) n O-, n is an odd number between 3 and 40.

8. The dimming device according to claim 7, characterized in that: The mesogen is selected from the group consisting of mesogens of formula II: -H1-Y-H2-Z-H3 II; in: H1 and H2 each independently represent a cyclic structure, H3 is a single bond or a cyclic structure, and the cyclic structure is selected from The group consisting of, wherein one or more H atoms in the cyclic structure can be independently substituted by halogen, a chain alkyl group having 1 to 10 carbon atoms, or an ester group; Y and Z each independently represent a single bond or a chain alkyl group with 1-10 C atoms, wherein one or more H atoms in the chain alkyl group with 1-10 C atoms can each independently be substituted by halogen, and one or more non-adjacent -CH2- in the chain alkyl group with 1-10 C atoms can each independently be replaced by -O-, -COO-, -CH=CH-, -CH=CF- or -CF=CF-. Preferably, Y, Z represent a single bond.

9. The dimming device according to claim 1, characterized in that: The dichroic dye is selected from at least one of azo dyes, anthraquinone dyes, benzothiadiazole dyes and rylene dyes.

10. The dimming device according to claim 9, characterized in that: The dichroic dye is a single component or a mixture of at least two components, wherein the absorption peak of each component is in any wavelength range between 300nm and 2500nm.

11. The dimming device according to claim 1, characterized in that: The cholesteric liquid crystal composition includes at least one nematic liquid crystal compound and at least one chiral compound.

12. The dimming device according to claim 11, characterized in that: The chiral compound accounts for 0.05 wt% to 20 wt% of the liquid crystal mixture.

13. The dimming device according to claim 11, characterized in that: The chiral compound is selected from any one or more of CB15, S(R)811, S(R)5011, S(R)1011, S(R)2011, and R6N.

14. The dimming device according to claim 1, characterized in that: The liquid crystal mixture also includes at least one polymerizable monomer and at least one initiator.

15. The dimming device according to claim 1, characterized in that: The transparent conductive base layer includes a first transparent conductive base layer and a second transparent conductive base layer, wherein the first transparent conductive base layer includes a first transparent substrate and a first transparent conductive layer disposed adjacent to the dye liquid crystal layer, and the second transparent conductive base layer includes a second transparent substrate and a second transparent conductive layer disposed adjacent to the dye liquid crystal layer.

16. The dimming device according to claim 15, characterized in that: The first transparent substrate and / or the second transparent substrate is flat glass, tempered glass, semi-tempered glass, float glass, or a plastic substrate film.

17. The dimming device according to claim 16, characterized in that: The plastic substrate film is selected from at least one of PET film, PI film, PTFE film, PP film, PC film, PVC film, PE film, PS film, PA film, PEN film, PMMA film and PBT film.

18. The dimming device according to claim 15, characterized in that: The material of the first transparent conductive layer and / or the second transparent conductive layer is any one of a metal oxide film, a metal nanowire conductive film, a metal grid, and a carbon-based conductive film.

19. The dimming device according to claim 18, characterized in that: At least one of the first and second transparent conductive layers is composed of at least one conductive region to which a voltage can be applied independently.

20. The dimming device according to claim 8, characterized in that: It also includes a first alignment layer and / or a second alignment layer disposed on the first transparent conductive base layer and / or the second transparent conductive base layer adjacent to the dye liquid crystal layer.

21. The dimming device according to claim 20, characterized in that: The material of the first alignment layer and / or the second alignment layer is any one of polyimide, polyvinyl alcohol, polyester, epoxy resin, polyurethane, polysilane, polystyrene and derivatives thereof.

22. The dimming device according to claim 20, characterized in that: The first alignment layer and / or the second alignment layer may be aligned in any one of a rubbing alignment method, a photo-controlled alignment method, an oblique evaporation method, and a LB film method.

23. The dimming device according to claim 20, characterized in that: The alignment type of the first alignment layer and / or the second alignment layer is VA type.

24. The dimming device according to claim 20, characterized in that: The alignment application operation of the first alignment layer and / or the second alignment layer is any one of a spin coating method, a dipping method, a relief printing method, a spray coating method or a slit coating method.

25. The dimming device according to claim 8, characterized in that: A spacing material is disposed between the first transparent conductive base layer and the second transparent conductive base layer. The spacing material is selected from at least one of resin, glass fiber and inorganic material. The spacing material may be in a spherical shape, a rod shape or a mixed shape.

26. The dimming device according to claim 1, characterized in that: The thickness of the dye liquid crystal layer is 1-60 μm.

27. The dimming device according to any one of claims 1 to 26, characterized in that: The transparent state is obtained by continuously applying a first voltage, and the shielding state is obtained by continuously applying a second voltage.

28. The dimming device according to claim 27, characterized in that: The second voltage is lower than the first voltage.

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