WO2020238610A1

WO2020238610A1 - A bistable light modulating device

Info

Publication number: WO2020238610A1
Application number: PCT/CN2020/089756
Authority: WO
Inventors: Kai Chen; Dong Li; Hongwei Zhang; Hui Xu
Original assignee: Smart Liquid Crystal Technologies Co., Ltd.
Priority date: 2019-05-24
Filing date: 2020-05-12
Publication date: 2020-12-03
Also published as: CN111983867A

Abstract

A bistable light modulating device which comprises a first transparent substrate (10), a first transparent electrode (20), a liquid crystal layer (30), a second transparent electrode (40) and a second transparent substrate (50) stacked in sequence, wherein the liquid crystal layer (30) contains a liquid crystal mixture including at least one bimesogenic compound, at least one nematic liquid crystal compound, at least one chiral compound and at least one organic ionic compound, wherein the bistable light modulating device includes two zero-electric-field-stable states: a transparent state where substantially all the incident light is transmitted and a light scattering state where substantially all the incident light is scattered. The bistable light modulating device can refresh the haze in the light scattering state and avoid the loss of privacy.

Description

A bistable light modulating device

Technical Field

The present invention relates to liquid crystal light modulating devices, and more particularly, to a bistable light modulating device where the bistable states may be directly refreshed.

Background of the Invention

As a device exploiting the electro-optic effect, a liquid-crystal-based light modulating device is mainly comprised of transparent conductive substrates and liquid crystal materials, where the orientation of liquid crystal molecules may be manipulated by applying an external electric field to switch between different optical states. Because of their unique characteristics, liquid-crystal-based light modulating devices are used in a wide range of applications, such as building materials, home decoration devices, automotive displays, and consuming electronic devices etc., for the realization of privacy, beautification and energy-saving functions. Among them, a bistable or multi-stable light modulating device is highly desirable due to its energy-saving and fail-safe features.

A bistable light modulating device based on cholesteric liquid crystal generally has two zero-electric-field-stable states: a transparent state and a light scattering state. Due to its angular-independent high transparency in the transparent state and high haze in the light scattering state, the bistable cholesteric liquid crystal light modulating device has therefore very high market potential as a light modulation device in a consumer electronics and as a building material. However, the haze in the light scattering state may be reduced because of changes in the external environment (such as stress, temperature, etc. ) , affecting the opacity of the device in the light scattering state and potentially affecting the application of the device in privacy. To restore the high haze, the light modulating device must be re-switched back to the original light scattering state by applying a driving voltage. As shown in FIG. 1, a traditional bistable light modulating device must be first switched from the lighting scattering state (b) to a transparent homeotropic state (c) which will relax to the transparent state (a) , and then is switched back to the light scattering state with high haze. Such a process, however, requires the light modulating device to be completely transparent for a period, thus causing an unwanted loss of privacy and therefore potentially limiting the applications of the device.

Therefore, there remains a need for a light modulating device which can be switch back to the light scattering state of high haze without losing the privacy.

Summary of the Invention

In order to overcome the above mentioned issues, the object of the present invention is to provide a bistable light modulating device which comprises a first transparent substrate, a first transparent electrode, a liquid crystal layer, a second transparent electrode and a second transparent substrate stacked in sequence, wherein the liquid crystal layer contains a liquid crystal mixture including at least one bimesogenic compound, at least one nematic liquid crystal compound, at least one chiral compound and at least one organic ionic compound, wherein the bistable light modulating device includes two zero-electric-field-stable states: a transparent state where substantially all the incident light is transmitted and a light scattering state where substantially all the incident light is scattered. In a preferred embodiment, the thickness of the liquid crystal layer is 5～60 μm. In a more preferred embodiment, the thickness of the liquid crystal layer is 10～60 μm.

In some embodiments, the organic ionic compound includes one or more selected from amine compounds, alkyl sulfate compounds, alkyl phosphate compounds and alkyl iodate compounds. In a preferred embodiment, the amine compound includes one or more selected from (Ferrocenylmethyl) trimethylammonium iodide, Phenyltrimethylammonium iodide, Cetyltrimethylammonium bromide, Tetrabutylammonium bromide, Tetraoctadecylammonium bromide, 1-Butyl-3-methylimidazolium tetrachloroferrate, 1-Butyl-3-methylimidazolium-L-lactate, 1-Ethyl-3-methylimidazolium-L-lactate, Cetyltrimethylammonium perchlorate, Benzyldimethylhexadecylammonium chloride, Dodecylpyridinium bromide, Hexadecylpyridinium bromide, Cetylpyridinium chloride, Cetyltributylammonium bromide, Octadecyltributylammonium bromide, Octadecyltrimethylammonium bromide and Dodecyltrimethylammonium bromide.

In some embodiments, the organic ionic compound is not more than 10%by weight of the liquid crystal mixture. In a preferred embodiment, the organic ionic compound is not more than 5%by weight of the liquid crystal mixture. In a more preferred embodiment, the organic ionic compound is not more than 1%by weight of the liquid crystal mixture.

In some embodiments, the bimesogenic compound is 5%～50%by weight of the liquid crystal mixture. In a preferred embodiment, the bimesogenic compound is 10%～50%by weight of the liquid crystal mixture.

In some embodiments, the materials of the first transparent substrate and the second transparent substrate include glass or polymer materials.

In some embodiments, the bistable light modulating device further comprises at least one alignment layer disposed between the first transparent electrode and the liquid crystal layer and/or between the second transparent electrode and the liquid crystal layer. In a preferred embodiment, the type of the alignment layer includes homogenous alignment and heterogeneous alignment.

In some embodiments, the haze of the light scattering state is changed by applying a refreshing voltage without first switching the bistable light modulating device to the transparent state. In a preferred embodiment, the frequency of the refreshing voltage is smaller than the frequency of the driving voltage for switching the light modulating device from the light scattering state to the transparent state.

In the present invention, by introducing organic ionic compounds into the liquid crystal layer, the bistable light modulating device can maintain two stable states and refresh the haze in the light scattering state without going through transparent homeotropic state, thereby avoiding the loss of privacy.

Brief Description of the Drawings

These and other features and advantages of the present invention will be better understood by reference to the following detailed description of an illustrative embodiment of the present disclosure when read in conjunction with the accompanying drawings, wherein:

FIG. 1 is a schematic, illustrative view of driving method of the bistable light modulating device on prior art;

FIG. 2 is a schematic, illustrative view of the structure of the bistable light modulating device of the present invention;

FIG. 3 is a schematic, illustrative view of working principle of the bistable light modulating device of the present invention;

FIG. 4 is a schematic, illustrative view of driving method of the bistable light modulating device of the present invention.

Detailed Description of the Invention

The following description of the disclosed embodiments is provided in detail to enable any person skilled in the art to fully understand the present invention. However, it will be apparent to those skilled in the art to readily make or use the present invention without these specific details. In other examples, well-known structures and devices are shown in the block diagram. In this regard, the description of the different illustrative exemplary embodiments presented herein are for the purpose of illustration and description and are not intended to be exhaustive or limited to the inventive concept. Accordingly, the scope of the invention is not to be limited by the specific embodiments described above, and is subject only to the scope of the appended claims.

As shown in FIG. 2, the present invention discloses a bistable light modulating device comprising a first transparent substrate 10, a first transparent electrode 20, a second transparent electrode 40, a second transparent substrate 50 and a liquid crystal layer 30 sandwiched between the first transparent electrode 20 and the second transparent electrode 40, where the thickness of the liquid crystal layer 30 is 5～60 μm. Preferably, the thickness of the liquid crystal layer 30 is 10～60 μm. The bistable light modulating device includes two zero-electric-field-stable states: a transparent state where substantially all the incident light is transmitted and a light scattering state where substantially all the incident light is scattered.

The first transparent substrate 10 and the second transparent substrate 50 may be transparent glass or transparent polymer materials, such as PET, PEN, PC, PP, PMMA, PBT, PVC, PI, cellulose, etc. The invention is not limited to this, and other materials with light transmission conforming to the requirements may also be used. The transparent electrode may cover the entire inner surface of the transparent substrate, as shown in FIG. 2, be etched to a specific shape as necessary, or be spitted into multiple electrodes. Depending on the materials, the transparent electrodes may be classified into carbon-based conductive films, metallic nanowire conductive films, and metallic oxide conductive films. The materials of the carbon-based conductive films mainly include graphene oxide and carbon nanotubes. The carbon-based conductive films may be prepared by a hybrid method. The metallic nanowire conductive films usually use silver nanowires or copper nanowires. The main materials of the metallic oxide conductive film are indium tin oxide (ITO) , indium oxide, tin oxide, zinc oxide, and a mixed system of other metallic oxides.

The liquid crystal 30 contains a liquid crystal mixture which includes at least one bimesogenic compound, at least one nematic liquid crystal compound, at least one chiral compound and at least one organic ionic compound. The bimesogenic compound is a liquid crystal containing two mesogen groups, that is, two groups capable of inducing liquid crystal phases. The bimesogenic compound is 5%～50%by weight of the liquid crystal mixture. Preferably, the bimesogenic compound is 10%～50%by weight of the liquid crystal mixture. The nematic liquid crystal is a liquid crystal compound or a liquid crystal mixture that has a nematic phase in a certain temperature range, such as 5CB, 2CB or E7. The nematic liquid crystal compound in the present invention does not include bimesogenic compounds.

The organic ionic compound is an organic compound that has both an ionic state and a certain solubility in liquid crystal compounds due to its similar structure as that of liquid crystal compounds. Normally, the concentration of different organic ionic compounds in liquid crystal compounds depends on respective solubilities, but excessive organic ionic compounds may form bubbles, thus affecting the stability of the liquid crystal phase. As a result, the organic ionic compound is not more than 10%by weight of the liquid crystal mixture. Preferably, the organic ionic compound is not more than 5%by weight of the liquid crystal mixture. More preferably, the organic ionic compound is not more than 1%by weight of the liquid crystal mixture. The organic ionic compound includes one or more selected from amine compounds, alkyl sulfate compounds, alkyl phosphate compounds and alkyl iodate compounds. The amine compound includes one or more selected from (Ferrocenylmethyl) trimethylammonium iodide, Phenyltrimethylammonium iodide, Cetyltrimethylammonium bromide, Tetrabutylammonium bromide (CTAB) , Tetraoctadecylammonium bromide, 1-Butyl-3-methylimidazolium tetrachloroferrate, 1-Butyl-3-methylimidazolium-L-lactate, 1-Ethyl-3-methylimidazolium-L-lactate, Cetyltrimethylammonium perchlorate, Benzyldimethylhexadecylammonium chloride, Dodecylpyridinium bromide, Hexadecylpyridinium bromide, Cetylpyridinium chloride, Cetyltributylammonium bromide, Octadecyltributylammonium bromide, Octadecyltrimethylammonium bromide and Dodecyltrimethylammonium bromide (DTAB) .

As shown in FIG. 3, the liquid crystal mixture in the role of a chiral compound can form a cholesteric liquid crystal, providing the light modulating device two stable states: the transparent state (a) where substantially all incident light goes though the device and the light scattering state (b) where substantially all incident light is scattered. In the transparent state (a) , the cholesteric liquid crystal molecules 301 are substantially aligned parallel to the device substrate, and the helical axis thereof is perpendicular to the device substrate to form a planar texture, where the incident light transmits through the light modulating device substantially unaffected. While in the scattering state (b) , the cholesteric liquid crystal molecules form a focal conic texture and the incident light is substantially scattered to form a state in which the haze is large but total light transmittance contains in a certain level. Due to the special elastic constants of the bimesogenic compound, the uniformity of the planar arrangement of the liquid crystal mixture is improved, the texture defect is decreased, and thereby the haze of the light modulating device in the transparent state reduces while the haze in the light scattering state increases. The organic ionic compound 302 dissolved in the liquid crystal molecules have no effect to the propagation direction of incident light, thus no effect to the haze.

As shown in FIG. 4, by selecting a suitable driving method, the light modulating device can be switched between the transparent state (a) , the light scattering state (b) and the homeotropic state (c) , thereby achieving the purpose of light modulating. The homeotropic state is not a stable state. When dissolved in liquid crystals, the organic ionic compounds decompose into ions which will move rapidly under a refreshing voltage of a certain frequency, thereby disturbing the orientation of the liquid crystal molecules. As a result, the light modulating device that has a dropped haze but are still in the light scattering state will restore the original haze (higher value) without going through the transparent homeotropic state, to achieve refreshing of haze. Generally, the frequency of the refreshing voltage V3 is smaller than the frequency of the driving voltage V2 for switching the light modulating device from the light scattering state (b) to the transparent state (c) .

The bistable light modulating device may also include at least one alignment layer, which further provides a specific orientation arrangement for the liquid crystal molecules in the liquid crystal layer. The bistable light modulating device may have two alignment layers locating on the inner surfaces of two transparent electrodes 20 and 40 (i.e. the surfaces contacting to the liquid crystal layer) , or only one alignment layer disposed on the inner surface of either of the transparent electrodes. The alignment layer is generally formed through the curing of an orientation agent, where the orientation agent is generally an organic polymer material such as PVB, siloxane and polyimide materials. Depending on the pretilt angle (i.e. the angle between the long axis of the liquid crystal molecules and the surface of the alignment layer when the liquid crystal molecules are sequentially arranged on the surface of the alignment layer) , the alignment layer can be classified into homogenous alignment where the long axis is substantially parallel to the surface, such as IPS, TN or STN type, or heterogeneous alignment where the long axis is substantially vertical to the surface, such as VA type.

In the following embodiments, the structure, optical performance and refreshing method of the bistable light modulating device will be described in detail. The two transparent substates used in the following embodiments are glass, and the two transparent electrodes are ITO electrodes. The haze values of the device in the light scattering state are measured using a WGT-Stype haze meter.

In the following embodiments, the formula of liquid crystal composition 1-3 (include bimesogenic compounds, nematic liquid crystal compounds and chiral compounds) is list in TABLE 1-3.

TABLE 1: formula 1 of the liquid crystal composition

TABLE 2: formula 2 of the liquid crystal composition

TABLE 3: formula 3 of the liquid crystal composition

Comparative example 1

In this example, the bistable light modulating device includes two VA alignment layers. The thickness of the liquid crystal layer is 20 μm. The formula of the liquid crystal composition is shown in TABLE 1. By selecting the appropriate driving voltage, the bistable light modulating device was respectively driven to the transparent state or the light scattering state, where the driving voltage from the light scattering state to the transparent state is 130V/1kHz and the driving voltage from the transparent state to the light scattering state is 60V/100Hz. After that, the bistable light modulating device in the light scattering state were processed thermal shock (0-40℃) for 2 hours, and then the bistable light modulating device is drive by the refreshing voltage of 60V/100Hz. The process is repeated on multiple samples and the haze values in the light scattering state are measured, as shown in TABLE 4. The bistable light modulating device cannot be switched directly back to the light scattering state, and the haze value is smaller.

TABLE 4: haze values of the light modulating device

	The original state	After thermal shock	After driven
Sample 1	90.84%	80.87%	61.72%
Sample 2	89.60%	80.81%	62.75%
Sample 3	90.20%	80.56%	60.30%
Sample 4	89.51%	82.41%	62.79%

Embodiment 1

In this example, the bistable light modulating device includes two VA alignment layers. The thickness of the liquid crystal layer is 20 μm. The formula of the liquid crystal mixture includes 99.995 wt%of liquid crystal composition 1 and 0.005 wt%of CTAB. By selecting the appropriate driving voltage, the bistable light modulating device was respectively driven to the transparent state or the light scattering state, where the driving voltage from the light scattering state to the transparent state is 130V/1kHz and the driving voltage from the transparent state to the light scattering state is 60V/100Hz. After that, the bistable light modulating device in the light scattering state were processed thermal shock (0-40℃) for 2 hours, and then the bistable light modulating device is drive by the refreshing voltage of 60V/100Hz. The process is repeated on multiple samples and the haze values in the light scattering state are measured, as shown in TABLE 5.

TABLE 5: haze values of the light modulating device

	The original state	After thermal shock	After refreshing
Sample 1	90.12%	82.36%	90.10%
Sample 2	89.63%	81.54%	90.07%
Sample 3	89.95%	81.37%	89.93%
Sample 4	90.26%	80.65%	90.14%

Embodiment 2

In this example, the bistable light modulating device includes two VA alignment layers. The thickness of the liquid crystal layer is 20 μm. The formula of the liquid crystal mixture includes 99.5 wt%of liquid crystal composition 1 and 0.5 wt%of CTAB. By selecting the appropriate driving voltage, the bistable light modulating device was respectively driven to the transparent state or the light scattering state, where the driving voltage from the light scattering state to the transparent state is 130V/1kHz and the driving voltage from the transparent state to the light scattering state is 60V/100Hz. After that, the bistable light modulating device in the light scattering state were processed thermal shock (0-40℃) for 2 hours, and then the bistable light modulating device is drive by the refreshing voltage of 60V/100Hz. The process is repeated on multiple samples and the haze values in the light scattering state are measured, as shown in TABLE 6.

TABLE 6: haze values of the light modulating device

	The original state	After thermal shock	After refreshing
Sample 1	90.68%	81.96%	90.38%
Sample 2	90.34%	81.05%	90.11%
Sample 3	89.95%	81.37%	89.89%
Sample 4	90.16%	80.58%	90.05%

Embodiment 3

In this example, the bistable light modulating device includes two VA alignment layers. The thickness of the liquid crystal layer is 20 μm. The formula of the liquid crystal mixture includes 99.995 wt%of liquid crystal composition 1 and 0.005 wt%of DTAB. By selecting the appropriate driving voltage, the bistable light modulating device was respectively driven to the transparent state or the light scattering state, where the driving voltage from the light scattering state to the transparent state is 130V/1kHz and the driving voltage from the transparent state to the light scattering state is 60V/100Hz. After that, the bistable light modulating device in the light scattering state were processed thermal shock (0-40℃) for 2 hours, and then the bistable light modulating device is drive by the refreshing voltage of 60V/100Hz. The process is repeated on multiple samples and the haze values in the light scattering state are measured, as shown in TABLE 7.

TABLE 7: haze values of the light modulating device

	The original state	After thermal shock	After refreshing
Sample 1	89.73%	80.64%	90.35%
Sample 2	90.05%	81.15%	89.82%
Sample 3	89.43%	82.38%	89.33%
Sample 4	89.82%	80.10%	89.87%

Embodiment 4

In this example, the bistable light modulating device includes two VA alignment layers. The thickness of the liquid crystal layer is 20 μm. The formula of the liquid crystal mixture includes 99.5 wt%of liquid crystal composition 1 and 0.5 wt%of DTAB. By selecting the appropriate driving voltage, the bistable light modulating device was respectively driven to the transparent state or the light scattering state, where the driving voltage from the light scattering state to the transparent state is 130V/1kHz and the driving voltage from the transparent state to the light scattering state is 60V/100Hz. After that, the bistable light modulating device in the light scattering state were processed thermal shock (0-40℃) for 2 hours, and then the bistable light modulating device is drive by the refreshing voltage of 60V/100Hz. The process is repeated on multiple samples and the haze values in the light scattering state are measured, as shown in TABLE 8.

TABLE 8: haze values of the light modulating device

	The original state	After thermal shock	After refreshing
Sample 1	90.09%	82.40%	90.62%

Sample 2	90.83%	82.69%	90.25%
Sample 3	90.36%	81.32%	90.07%
Sample 4	89.43%	80.34%	89.16%

Embodiment 5

In this example, the bistable light modulating device includes two VA alignment layers. The thickness of the liquid crystal layer is 15 μm. The formula of the liquid crystal mixture includes 99.5 wt%of liquid crystal composition 2 and 0.5 wt%of CTAB. By selecting the appropriate driving voltage, the bistable light modulating device was respectively driven to the transparent state or the light scattering state, where the driving voltage from the light scattering state to the transparent state is 130V/1kHz and the driving voltage from the transparent state to the light scattering state is 60V/100Hz. After that, the bistable light modulating device in the light scattering state were processed thermal shock (0-40℃) for 2 hours, and then the bistable light modulating device is drive by the refreshing voltage of 60V/100Hz. The process is repeated on multiple samples and the haze values in the light scattering state are measured, as shown in TABLE 9.

TABLE 9: haze values of the light modulating device

	The original state	After thermal shock	After refreshing
Sample 1	61.34%	46.80%	69.92%
Sample 2	62.12%	47.98%	62.17%
Sample 3	62.29%	46.03%	62.35%
Sample 4	61.79%	47.89%	61.48%

Embodiment 6

In this example, the bistable light modulating device includes two VA alignment layers. The thickness of the liquid crystal layer is 50 μm. The formula of the liquid crystal mixture includes 99.5 wt%of liquid crystal composition 1 and 0.5 wt%of CTAB. By selecting the appropriate driving voltage, the bistable light modulating device was respectively driven to the transparent state or the light scattering state, where the driving voltage from the light scattering state to the transparent state is 130V/1kHz and the driving voltage from the transparent state to the light scattering state is 60V/100Hz. After that, the bistable light modulating device in the light scattering state were processed thermal shock (0-40℃) for 2 hours, and then the bistable light modulating device is drive by the refreshing voltage of 60V/100Hz. The process is repeated on multiple samples and the haze values in the light scattering state are measured, as shown in TABLE 10.

TABLE 10: haze values of the light modulating device

	The original state	After thermal shock	After refreshing
Sample 1	93.94%	85.65%	93.73%
Sample 2	93.75%	85.31%	93.82%
Sample 3	93.83%	86.02%	93.86%
Sample 4	93.90%	85.86%	93.71%

Embodiment 7

In this example, the bistable light modulating device includes two VA alignment layers. The thickness of the liquid crystal layer is 15 μm. The formula of the liquid crystal mixture includes 99.5 wt%of liquid crystal composition 3 and 0.5 wt%of CTAB. By selecting the appropriate driving voltage, the bistable light modulating device was respectively driven to the transparent state or the light scattering state, where the driving voltage from the light scattering state to the transparent state is 130V/1kHz and the driving voltage from the transparent state to the light scattering state is 60V/100Hz. After that, the bistable light modulating device in the light scattering state were processed thermal shock (0-40℃) for 2 hours, and then the bistable light modulating device is drive by the refreshing voltage of 60V/100Hz. The process is repeated on multiple samples and the haze values in the light scattering state are measured, as shown in TABLE 11.

TABLE 11: haze values of the light modulating device

	The original state	After thermal shock	After refreshing
Sample 1	82.59%	65.46%	82.90%
Sample 2	83.48%	66.82%	83.34%
Sample 3	82.91%	66.55%	83.15%
Sample 4	82.70%	66.53%	82.10%

The liquid crystal mixture used in the bistable light modulating device includes bimesogenic compounds, nematic liquid crystal compounds and chiral compounds which are known well by those skilled in the art. The formula 1-3 of the liquid crystal composition are considered illustrative rather than limiting.

By introducing organic ionic compounds into the liquid crystal layer, the bistable light modulating device can maintain two stable states and refresh the haze in the light scattering state without going through transparent homeotropic state, thereby avoiding the loss of privacy.

While several particular exemplary embodiments have been described above in detail, the disclosed embodiments are considered illustrative rather than limiting. Those skilled in the art will readily realize that alternatives, modifications, variations, improvements, and substantial equivalents are possible without substantially departing from the novelty spirits or scope of the present disclosure. Thus, all such alternatives, modifications, variations, improvements, and substantial equivalents are intended to be embraced within the scope of the present disclosure as defined by the appended claims.

Industrial Applicability

The liquid crystal light modulating devices of the present invention can be applied to the field of liquid crystal.

Claims

A bistable light modulating device, comprising a first transparent substrate, a first transparent electrode, a liquid crystal layer, a second transparent electrode and a second transparent substrate stacked in sequence, wherein the liquid crystal layer contains a liquid crystal mixture including at least one bimesogenic compound, at least one nematic liquid crystal compound, at least one chiral compound and at least one organic ionic compound, wherein the bistable light modulating device includes two zero-electric-field-stable states: a transparent state where substantially all the incident light is transmitted and a light scattering state where substantially all the incident light is scattered.
The bistable light modulating device as defined in claim 1, wherein the organic ionic compound includes one or more selected from amine compounds, alkyl sulfate compounds, alkyl phosphate compounds and alkyl iodate compounds.
The bistable light modulating devices as defined in claim 2, wherein the amine compound includes one or more selected from (Ferrocenylmethyl) trimethylammonium iodide, Phenyltrimethylammonium iodide, Cetyltrimethylammonium bromide, Tetrabutylammonium bromide, Tetraoctadecylammonium bromide, 1-Butyl-3-methylimidazolium tetrachloroferrate, 1-Butyl-3-methylimidazolium-L-lactate, 1-Ethyl-3-methylimidazolium-L-lactate, Cetyltrimethylammonium perchlorate, Benzyldimethylhexadecylammonium chloride, Dodecylpyridinium bromide, Hexadecylpyridinium bromide, Cetylpyridinium chloride, Cetyltributylammonium bromide, Octadecyltributylammonium bromide, Octadecyltrimethylammonium bromide and Dodecyltrimethylammonium bromide.
The bistable light modulating device as defined in claim 1, wherein the organic ionic compound is not more than 10%by weight of the liquid crystal mixture.
The bistable light modulating device as defined in claim 1, wherein the bimesogenic compound is 5%～50%by weight of the liquid crystal mixture.
The bistable light modulating device as defined in claim 1, wherein the thickness of the liquid crystal layer is 5～60 μm.
The bistable light modulating device as defined in claim 3, wherein the materials of the first transparent substrate and the second transparent substrate include glass or polymer materials.
The bistable light modulating device as defined in claim 1, further comprising at least one alignment layer disposed between the first transparent electrode and the liquid crystal layer and/or between the second transparent electrode and the liquid crystal layer.
The bistable light modulating device as defined in claim 8, wherein the type of the alignment layer includes homogenous alignment and heterogeneous alignment.
The bistable light modulating device as defined in claim 1, wherein the haze of the light scattering state is changed by applying a refreshing voltage without first switching the bistable light modulating device to the transparent state.
The bistable light modulating device as defined in claim 10, wherein the frequency of the refreshing voltage is smaller than the frequency of the driving voltage for switching the light modulating device from the light scattering state to the transparent state.