CN113238421A

CN113238421A - Bistable dimming device with reflection wavelength not changing along with temperature and preparation method

Info

Publication number: CN113238421A
Application number: CN202110538089.7A
Authority: CN
Inventors: 李莉; 张宏伟; 沈喜妹
Original assignee: Jiangsu Jitri Smart Liquid Crystal Sci and Tech Co Ltd
Current assignee: Jiangsu Jitri Smart Liquid Crystal Sci and Tech Co Ltd
Priority date: 2021-05-18
Filing date: 2021-05-18
Publication date: 2021-08-10

Abstract

The invention relates to a bistable light modulator with a reflection wavelength not changing with temperature, which comprises a first transparent conductive base layer and a second transparent conductive base layer which are oppositely arranged, and a liquid crystal layer arranged between the first transparent conductive base layer and the second transparent conductive base layer, wherein the liquid crystal layer is prepared from a liquid crystal composition, the liquid crystal composition comprises a nematic liquid crystal compound, a positive temperature sensitive chiral compound, a negative temperature sensitive chiral compound and a bimesogenic compound, and the bistable light modulator comprises two states with stable zero electric field: a transmissive state that substantially transmits incident light, and a foggy state that substantially scatters incident light. The dimming device has low transmission state haze and high fog state haze, can realize that the reflection wavelength does not change along with the ambient temperature, and is suitable for a plurality of application scenes such as showcases, crop cultivation and the like.

Description

Bistable dimming device with reflection wavelength not changing along with temperature and preparation method

Technical Field

The invention relates to the technical field of light-adjusting devices, in particular to a bistable light-adjusting device with a reflection wavelength not changing along with temperature and a preparation method thereof.

Background

The liquid crystal-based dimming device is used as a device applying a photoelectric effect and mainly comprises a transparent conductive base material and a liquid crystal material, and the arrangement state of liquid crystal molecules is controlled by an external electric field mode to realize the conversion between a transparent macroscopic state and an opaque macroscopic state. Due to the unique dimming characteristic, the liquid crystal-based dimming device is widely applied to industries such as buildings, houses and automobiles, and is used for realizing functions such as privacy, aesthetic property and energy conservation.

At present, the bistable liquid crystal light modulator has remarkable improvement in energy saving compared with the traditional light modulator because of zero electric field maintenance of two states, and is a main development trend in the market of the light modulator. In the bistable light modulator disclosed in the prior art, the middle liquid crystal layer is cholesteric liquid crystal, and is prepared by adding chiral dopant into nematic liquid crystal. The central wavelength of the cholesteric liquid crystal planar state reflected light meets the Bragg reflection law: λ ═ nP, n is the average refractive index, and P is the pitch of the helix. The helical pitch of cholesteric liquid crystals has a significant influence on their optical properties, and the characteristics of light transmission and selective light scattering are mainly determined by the helical pitch. However, the helical pitch of cholesteric liquid crystals has a significant temperature sensitivity and changes with temperature. For ease of expression, we define: chiral dopants exhibiting dP/dT > 0 are positive temperature sensitive chiral compounds and chiral dopants exhibiting dP/dT < 0 are negative temperature sensitive chiral compounds. The helical pitches of the conventional chiral dopants such as CB15, S (R)811, S (R)5011, CN and the like all show positive temperature sensitivity, namely dP/dT is more than 0, and finally, the selective reflection wavelength moves to the direction of positive wavelength along with the temperature rise, so that the situation that privacy protection is needed and a specific reflection wavelength is needed is not applicable, for example, a bistable dimming device is applied to crop cultivation and needs to be set according to a specific waveband needed by different crops for growth and does not change along with the environmental temperature. Therefore, it is desirable to provide a light modulation device that has good bistable optical characteristics, can realize a reflection wavelength that does not change with ambient temperature, and can be applied to an application scenario requiring a rated reflection wavelength.

Disclosure of Invention

The application mainly solves the problem of how to design the dimming device, and realizes that the reflection wavelength of the external environment light does not change along with the ambient temperature, thereby meeting the application of a scene needing the rated reflection wavelength.

In order to achieve the above object, the present application provides a bistable light modulator with a reflection wavelength unchanged with temperature, comprising a first transparent conductive substrate and a second transparent conductive substrate which are oppositely arranged, and a liquid crystal layer arranged between the first transparent conductive substrate and the second transparent conductive substrate, wherein the liquid crystal layer is prepared from a liquid crystal composition, the liquid crystal composition comprises a nematic liquid crystal compound, a positive temperature sensitive chiral compound, a negative temperature sensitive chiral compound, and a bimesogenic compound, wherein the bistable light modulator comprises two states with stable zero electric field: a transmissive state that substantially transmits incident light, and a foggy state that substantially scatters incident light.

As a further improvement of the application, the nematic phase liquid crystal compound accounts for 40-70% of the total mass of the liquid crystal composition.

As a further improvement of the application, the positive temperature sensitive chiral compound accounts for 0.1-30% of the total mass of the liquid crystal composition.

As a further improvement of the present application, the positive temperature sensitive chiral compound is at least one of CB15, S811, S5011, R811, R5011.

As a further improvement of the application, the negative temperature sensitivity chiral compound accounts for 0.1-30% of the total mass of the liquid crystal composition.

As a further refinement of the present application, the negative temperature-sensitive chiral compound has the same handedness as the positive temperature-sensitive chiral compound.

As a further improvement of the application, the bimesogenic compound accounts for 5-50% of the total mass of the liquid crystal composition.

As a further improvement of the application, the thickness of the liquid crystal layer is 2-100 μm.

As a further improvement of the present application, the thickness of the liquid crystal layer is 5 μm to 50 μm.

As a further improvement of the present application, the first transparent conductive base layer and/or the second transparent conductive base layer is prepared from a transparent base layer and a transparent conductive electrode covering the transparent base layer.

As a further improvement of the application, the transparent conductive base layer is any one of flat glass, tempered glass, semi-tempered glass, float glass, a PET film and a PTFE film.

As a further improvement of the application, the material for preparing the transparent conductive electrode is at least one of a metal oxide film, a metal nanowire conductive film, a metal grid and a carbon-based conductive film.

As a further improvement of the present application, an alignment layer is 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.

As a further development of the present application, the alignment type of the alignment layer is a substantially planar orientation or a substantially homeotropic orientation.

As a further improvement of the present application, the alignment layer may be oriented by any one of a rubbing orientation method, a photo-orientation method, an oblique evaporation method, and an LB film method.

As a further improvement of the application, the material for preparing the alignment layer is any one of polyimide, siloxane and PVB.

In order to achieve the above object, the present application further provides a method for preparing the bistable light modulator by using a vacuum infusion process, including the following steps: s1, arranging the first transparent conductive base layer and the second transparent conductive base layer in a contraposition mode with inner surfaces opposite to each other; s2, attaching the first transparent conductive base layer and the second transparent conductive base layer which are arranged in an aligned mode through frame sealing glue, and adding a spacer between the two transparent conductive base layers to control the gap between the two transparent conductive base layers; s3, filling a liquid crystal composition in the gap between the two transparent conductive base layers to form a liquid crystal layer, wherein the liquid crystal composition comprises a nematic liquid crystal compound, a positive temperature sensitive chiral compound, a negative temperature sensitive chiral compound and a bimesogenic compound, and the bistable light modulation device comprises two stable states with zero electric field: a transmitted state that substantially transmits incident light and a foggy state that substantially scatters incident light; and S4, curing the seal to form the bistable light modulator.

As a further improvement of the present application, an alignment layer is formed on a surface of the first transparent conductive base layer or the second transparent conductive base layer close to the liquid crystal layer by alignment along a direction; and carrying out orientation arrangement on the alignment layer along the direction.

In order to achieve the above object, the present application further provides an ODF process for manufacturing the bistable light modulator, including the following steps: s1, coating the frame sealing glue on the first transparent conductive base layer; s2, adding spacers into the liquid crystal composition, mixing and stirring uniformly, and dripping the mixture on the first transparent conductive base layer according to a proper single-drop amount and single-drop interval; the liquid crystal composition comprises a nematic liquid crystal compound, a positive temperature sensitive chiral compound, a negative temperature sensitive chiral compound and a bimesogenic compound, wherein the bistable light modulator comprises two states with stable zero electric field: a transmitted state that substantially transmits incident light and a foggy state that substantially scatters incident light; s3, attaching the second transparent conductive base layer to the first transparent conductive base layer by frame sealing glue according to alignment arrangement; and S4, curing the frame sealing glue to form the bistable dimming device.

The positive temperature sensitive chiral compound and the negative temperature sensitive chiral compound are added into the nematic liquid crystal composition, the pitch of the nematic liquid crystal can be adjusted after the two chiral compounds are compounded, the temperature sensitivity of selective reflection wavelength can be eliminated by adjusting the content of the positive temperature sensitive chiral compound and the negative temperature sensitive chiral compound, the reflection wavelength is enabled not to deviate along with the temperature change, and the bistable characteristic of zero electric field is achieved.

Drawings

Fig. 1 is a schematic structural diagram of a bistable light modulator;

FIG. 2 is a graph of the reflectance spectrum of example 1;

FIG. 3 is a graph of the reflectance spectrum of example 2;

FIG. 4 is a graph of the reflectance spectrum of example 3;

FIG. 5 is a graph of the reflectance spectrum of example 4;

FIG. 6 is a graph of the reflectance spectrum of example 5;

FIG. 7 is a graph of the reflectance spectrum of example 6;

FIG. 8 is a graph of the reflectance spectrum of example 7;

FIG. 9 is a graph of the reflectance spectrum of example 8;

in the figure: 1. a first transparent conductive base layer; 2. a second transparent conductive base layer; 3. a liquid crystal layer; 4. a first alignment layer; 5. a second alignment layer.

Detailed Description

In order to make the objects, technical solutions and advantages of the present application more clear, the following description of the present application will be made in detail and completely with reference to the specific embodiments and the accompanying drawings. It should be understood that the described embodiments are only a few embodiments of the present application, not all embodiments, and are not intended to limit the scope of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

In order to prepare a light modulation device with reflection wavelength not changing with temperature for external environment light, the application provides a bistable light modulation device with reflection wavelength not changing with temperature, as shown in fig. 1, comprising a first transparent conductive base layer 1 and a second transparent conductive base layer 2 which are oppositely arranged, and a liquid crystal layer 3 arranged between the first transparent conductive base layer 1 and the second transparent conductive base layer 2, wherein the liquid crystal layer 3 is prepared from a liquid crystal composition, the liquid crystal composition comprises a nematic liquid crystal compound, a positive temperature sensitive chiral compound, a negative temperature sensitive chiral compound and a bimesogenic compound, wherein the bistable light modulation device comprises two stable states with zero electric field: a transmissive state that substantially transmits incident light, and a foggy state that substantially scatters incident light. In the scheme: the bistable light modulator adjusts the pitch by compounding the positive temperature sensitive chiral compound and the negative temperature sensitive chiral compound, and eliminates the temperature sensitivity of selective reflection wavelength by adjusting the content of the positive temperature sensitive chiral compound and the negative temperature sensitive chiral compound, so that the reflection wavelength does not deviate along with the temperature change, and the bistable light modulator has the bistable characteristic of zero electric field. In the present application, the nematic liquid crystal compound is a commonly used liquid crystal compound or liquid crystal mixture with a nematic phase, such as 5CB, 2CB, E7, etc., and the nematic liquid crystal composition provides basic photoelectric characteristic parameters for a bistable light modulator, which is the key of the bistable light modulator with a light modulation function. In a preferred embodiment, the nematic liquid crystal compound accounts for 40 to 70% of the total mass of the liquid crystal composition.

In the application, the positive temperature sensitive chiral compound is a chiral material which is common in the field, the positive temperature sensitive chiral compound can be at least one of CB15, S811, S5011, R811 and R5011, and the positive temperature sensitive chiral compound accounts for 0.1-30% of the total mass of the liquid crystal composition. As a further preferred embodiment, the positive temperature sensitive chiral compound accounts for 0.1% to 20% of the total mass of the liquid crystal composition.

In the present application, as a preferred embodiment, the negative temperature-sensitive chiral compound and the positive temperature-sensitive chiral compound have the same handedness, and the negative temperature-sensitive chiral compound accounts for 0.1 to 30 percent of the total mass of the liquid crystal composition. As a further preferred embodiment, the negative temperature-sensitive chiral compound accounts for 0.1% to 20% of the total mass of the liquid crystal composition.

In the present application, the bimesogenic compound in the liquid crystal composition is a liquid crystal compound containing two mesogens in the molecule, that is, the bimesogenic compound contains two groups capable of inducing liquid crystal phase in the molecule. In a preferred embodiment, the bimesogenic compound accounts for 5% to 50% of the total mass of the liquid crystal composition. As a further preferred embodiment, the bimesogenic compound accounts for 5% to 30% of the total mass of the liquid crystal composition. In principle: the bimesogenic compound and the nematic liquid crystal compound can form a chiral nematic phase (namely, a cholesteric phase) under the action of the chiral compound, so that the dimming device has two stable states: a transmitted state in which incident light is substantially directed and a fogged state in which incident light is substantially scattered. In a transmission state, cholesteric liquid crystal molecules are basically parallel to the surface of the light modulation device, and a spiral shaft of the cholesteric liquid crystal molecules is vertical to the surface of the light modulation device, so that a planar texture of cholesteric liquid crystal is formed, and in the state, incident light basically keeps the original incident angle to pass through the light modulation device without being influenced; in the foggy state, the cholesteric liquid crystal molecules form a focal conic texture, and incident light is basically scattered to form a state with high haze. Due to the special elastic coefficient of the bimesogenic compound, the bimesogenic compound can be used as an elastic constant modulator, so that the relaxation time of the bistable liquid crystal from a vertical state to a planar state is shortened, the uniformity of the planar arrangement of liquid crystal molecules can be improved, and the texture defect is reduced, thereby reducing the haze of the bistable light modulator in a transmission state and simultaneously improving the haze of a fog state.

In the present application, as a preferred embodiment, the thickness of the liquid crystal layer is 2 μm to 100 μm; in a more preferred embodiment, the thickness of the liquid crystal layer is 5 μm to 50 μm. The liquid crystal dimming device can realize the stable transmission state and fog state of a zero electric field, has lower transmission state haze and higher fog state haze, and can realize that the reflection wavelength does not change along with the ambient temperature, thereby further increasing the functionality on the basis of transmission state high transmission and fog state shielding.

As a preferred embodiment, an alignment layer is disposed between the first transparent conductive base layer and the liquid crystal layer and/or between the second transparent conductive base layer and the liquid crystal layer; as a further preferred embodiment, the material for preparing the alignment layer may be any one of, but not limited to, polyimide, siloxane, PVB, and the like. According to the difference of the pretilt angle (i.e. the included angle formed by the long axis direction of the molecules and the surface of the alignment layer when the liquid crystal molecules are orderly arranged on the surface of the alignment layer), the alignment type of the alignment layer can be classified into the basic plane alignment or the basic vertical alignment: the liquid crystal molecules in the alignment layer are oriented in a substantially plane, i.e. the long axes of the liquid crystal molecules on the surface of the alignment layer are substantially parallel to the surface of the alignment layer, such as TN, IPS, STN type and the like; substantially vertical alignment, i.e. the long axis of the liquid crystal molecules is substantially perpendicular to the surface of the alignment layer, e.g. VA-type. As a preferred embodiment, the alignment layer may be oriented by any one of, but not limited to, rubbing, photo-alignment, oblique vapor deposition, and LB film, and the alignment treatment is mainly used to constrain the liquid crystal molecules near the surface of the alignment layer from orderly arrangement.

In the present application, as a preferred embodiment, the first transparent conductive base layer and/or the second transparent conductive base layer is prepared from a transparent base layer and a transparent conductive electrode covering the transparent base layer, the transparent conductive electrode being provided on a side in contact with the liquid crystal layer; the transparent base layer may be transparent glass or a transparent polymer material, and as a further preferred embodiment, the transparent conductive base layer may be, but is not limited to, any one of flat glass, tempered glass, semi-tempered glass, float glass, PET film, PTFE film, and the like. The transparent conductive electrode can be a film covering the whole inner surface of the transparent base layer, and can be further etched into a specific shape or divided into a plurality of corresponding sub-electrodes according to requirements. The material for preparing the transparent conductive electrode can be, but not limited to, at least one of a metal oxide conductive film, a metal nanowire conductive film, a metal grid, a carbon-based conductive film, and the like. The carbon-based conductive material mainly includes graphene oxide and carbon nanotubes, the metal nanowire conductive film usually adopts silver nanowires or copper nanowires, and the metal oxide conductive film is mainly made of a mixed system of Indium Tin Oxide (ITO), indium oxide, tin oxide, zinc oxide and other metal oxides. In the following examples, the transparent electrode is an ITO electrode.

In order to prove that the bistable light-adjusting device prepared by the scheme of the application has the function that the reflection wavelength of the external environment light does not change along with the temperature, the application also provides a series of following embodiments:

the embodiment of the application provides a light modulation device, as shown in fig. 1, including relative first transparent conductive basic layer 1 and the transparent conductive basic layer 2 of second that sets up to and locate first transparent conductive basic layer 1 and the transparent conductive basic layer 2 between the liquid crystal layer 3 first transparent basic layer with be equipped with first alignment layer 4 between the liquid crystal layer 3 the transparent basic layer of second with be equipped with second alignment layer 5 between the liquid crystal layer 3, wherein liquid crystal layer 3 includes nematic liquid crystal compound, positive temperature sensitivity chiral compound, negative temperature sensitivity chiral compound, bimesogenic compound. The thickness of the liquid crystal layer 3 is 5-50 microns, the first transparent conductive base layer 1 and the second transparent conductive base layer 2 are both in a flat glass/ITO mode, the alignment layer materials of the first alignment layer 4 and the second alignment layer 5 are both polyimide, and the alignment types of the first alignment layer 4 and the second alignment layer 5 are both VA types.

The liquid crystal composition is prepared according to the proportion of the liquid crystal composition specified in each example in the embodiment of the application, the preparation of the liquid crystal composition is carried out according to a conventional method in the field, and the specific steps are as follows: weighing the components and compounds according to the corresponding mass percentage in a glass bottle, adding a magnetic stirrer, placing on a heating table, heating and stirring until the liquid crystal composition in the sample bottle is clear, continuing to heat and stir for 30 minutes, stopping heating, and continuing to stir for 2 hours.

The application also provides a method for preparing the bistable light modulator by adopting a vacuum infusion process, which comprises the following steps: s1, arranging the first transparent conductive base layer and the second transparent conductive base layer in a contraposition mode with inner surfaces opposite to each other; s2, attaching the first transparent conductive base layer and the second transparent conductive base layer which are arranged in an aligned mode through frame sealing glue, and adding a spacer between the two transparent conductive base layers to control the gap between the two transparent conductive base layers; s3, filling a liquid crystal composition in the gap between the two transparent conductive base layers to form a liquid crystal layer, wherein the liquid crystal composition comprises a nematic liquid crystal compound, a positive temperature sensitive chiral compound, a negative temperature sensitive chiral compound and a bimesogenic compound, and the bistable light modulation device comprises two stable states with zero electric field: a transmitted state that substantially transmits incident light and a foggy state that substantially scatters incident light; and S4, curing the seal to form the bistable light modulator.

As a preferred embodiment, in the method for manufacturing the bistable light modulation device described above by using a vacuum infusion process, an alignment layer is formed on a surface of the first transparent conductive base layer or the second transparent conductive base layer close to the liquid crystal layer; and carrying out orientation arrangement on the alignment layer along the direction. Preferably, the alignment method includes a rubbing alignment method, a photo-alignment method, an oblique evaporation method, or an LB film method. Further preferably, the rubbing alignment method is a single-sheet intermittent rubbing method or a roll-to-roll continuous rubbing method.

In this application, a method for manufacturing the bistable light modulator using an liquid crystal drop injection (ODF) process is also provided, which includes the following steps: s1, coating the frame sealing glue on the first transparent conductive base layer; s2, adding spacers into the liquid crystal composition, mixing and stirring uniformly, and dripping the mixture on the first transparent conductive base layer according to a proper single-drop amount and single-drop interval; the liquid crystal composition comprises a nematic liquid crystal compound, a positive temperature sensitive chiral compound, a negative temperature sensitive chiral compound and a bimesogenic compound, wherein the bistable light modulator comprises two states with stable zero electric field: a transmitted state that substantially transmits incident light and a foggy state that substantially scatters incident light; s3, attaching the second transparent conductive base layer to the first transparent conductive base layer by frame sealing glue according to alignment arrangement; and S4, curing the frame sealing glue to form the bistable dimming device.

As a preferred embodiment, in the method for manufacturing the bistable light modulation device described above by using the ODF process, an alignment layer is formed on a surface of the first transparent conductive base layer or the second transparent conductive base layer close to the liquid crystal layer; and carrying out orientation arrangement on the alignment layer along the direction. Preferably, the alignment method includes a rubbing alignment method, a photo-alignment method, an oblique evaporation method, or an LB film method. Further preferably, the rubbing alignment method is a single-sheet intermittent rubbing method or a roll-to-roll continuous rubbing method.

For convenience of expression, the names and unit structures of a series of groups and different unit structures in table one, which can be used in the present application, are given in table one, the codes and corresponding structures of chiral compounds added to the liquid crystal composition are given in table two, and the codes, temperature sensitivity, rotation direction and HTP value of chiral compounds for preparing the liquid crystal composition are given in table three, wherein the proportions of groups for preparing the nematic liquid crystal composition in table four and table five are all expressed in mass percent.

Table one: name, unit structure and code for preparing nematic liquid crystal composition and group of bimesogenic compound

Code usage problem: example "5 PPN", according to the nomenclature shown in Table one, the corresponding structure is

For example, n is 3, and the corresponding structure is-C according to the nomenclature shown in table one₃H₇。

Table two: chiral compound code and structure for preparing liquid crystal composition

Table three: chiral compound codes, temperature sensitivity, handedness and HTP values for preparing liquid crystal compositions

Compound code	Temperature sensitivity	Direction of rotation	HTP value/. mu.m^-1
				S811	Is just	Left hand rotation	10
S5011	Is just	Left hand rotation	99
				R1	Negative pole	Left hand rotation	10
R2	Negative pole	Left hand rotation	10

Further preferably, the present application provides a nematic liquid crystal composition a, the formulation of which is shown in table four.

Table four: formulation of nematic liquid crystal composition A

The application also provides a nematic liquid crystal composition B, and the formula of the nematic liquid crystal composition B is shown in Table five.

Table five: formulation of nematic liquid crystal composition B

Component code	Mass percent/%)	Component code	Mass percent/%)
				5PPN	25.0	3PGPN	20.4
2PPN	9.3	5CPPN	11.0
				5OPPN	19.4	5PPPN	5.6
6OPPN	9.3

The liquid crystal composition is prepared from 8 different components based on a nematic liquid crystal composition A and a nematic liquid crystal composition B, and is prepared into a bistable light modulator and subjected to performance detection, wherein the formula and the performance test result of the liquid crystal composition are shown in Table six. The device selected in the performance test process of the reflection spectrum test device with different temperatures is an ultraviolet visible spectrometer and an mk2000 temperature controller, and the measurement conditions are as follows: a) environmental conditions: the temperature controller regulates and controls the temperature; b) dark room conditions: measuring in a dark room; c) preheating conditions are as follows: preheating a light source for 30 min; d) the test direction is as follows: perpendicular to the sample surface; e) measuring the position: the measurement point is located in an active area of the light modulation device.

Table six: examples 1-8 liquid crystal composition formulations and performance results of corresponding bistable dimmers

In table six, the arithmetic mean of the wavelengths at half peak heights is used as the value of the selective reflection wavelength, the half peak height wavelengths at two selected temperatures are required to be displayed in the test waveband, the wavelength offset is evaluated as Δ λ/Δ T, and the reflection wavelength is evaluated as not changing with the temperature when the absolute value of Δ λ/Δ T is less than or equal to 1 nm/DEG C. In addition, haze in the hazy/clear state was measured by WGT-S haze Meter, measuring temperature 25 deg.C 22 deg.C.

In table six, the numerical units corresponding to the substances in the examples all adopt mass percentages, wherein: the reflectance spectrum of example 1 is shown in fig. 2, the reflectance spectrum of example 2 is shown in fig. 3, the reflectance spectrum of example 3 is shown in fig. 4, the reflectance spectrum of example 4 is shown in fig. 5, the reflectance spectrum of example 5 is shown in fig. 6, the reflectance spectrum of example 6 is shown in fig. 7, the reflectance spectrum of example 7 is shown in fig. 8, and the reflectance spectrum of example 8 is shown in fig. 9.

Through the embodiment, the bistable light modulation device can realize the transmission state and the fog state with stable zero electric field, has lower transmission state haze and higher fog state haze, and can realize that the reflection wavelength does not change along with the ambient temperature, thereby further increasing the functionality on the basis of transmission state high transmission and fog state shielding. Can be applied to showcases, crop cultivation and the like.

To sum up, the application provides a bistable light modulator that reflection wavelength does not change along with temperature, including relative first transparent conductive basic unit and the transparent conductive basic unit of second that sets up, and locate first transparent conductive basic unit with liquid crystal layer between the transparent conductive basic unit of second, the liquid crystal layer is formed by the preparation of liquid crystal composition, the liquid crystal composition includes nematic liquid crystal compound, positive temperature sensitivity chiral compound, negative temperature sensitivity chiral compound, bimesogenic compound, wherein, bistable light modulator includes two zero electric field stable states: a transmissive state that substantially transmits incident light, and a foggy state that substantially scatters incident light. The dimming device has low transmission state haze and high fog state haze, can realize that the reflection wavelength does not change along with the ambient temperature, and is suitable for showcases, crop cultivation and the like.

Although the description is given in terms of embodiments, not every embodiment includes only a single embodiment, and such description is for clarity only, and those skilled in the art will recognize that the embodiments described herein may be combined as a whole to form other embodiments as would be understood by those skilled in the art.

The above-listed detailed description is only a specific description of a possible embodiment of the present invention, and they are not intended to limit the scope of the present invention, and equivalent embodiments or modifications made without departing from the technical spirit of the present invention should be included in the scope of the present invention.

Claims

1. The bistable light modulator with the reflection wavelength not changing along with the temperature is characterized by comprising a first transparent conductive base layer and a second transparent conductive base layer which are oppositely arranged, and a liquid crystal layer arranged between the first transparent conductive base layer and the second transparent conductive base layer, wherein the liquid crystal layer is prepared from a liquid crystal composition, the liquid crystal composition comprises a nematic liquid crystal compound, a positive temperature sensitive chiral compound, a negative temperature sensitive chiral compound and a bimesogenic compound, and the bistable light modulator comprises two states with stable zero electric field: a transmissive state that substantially transmits incident light, and a foggy state that substantially scatters incident light.

2. A bistable light modulating device as claimed in claim 1 wherein said nematic liquid crystal compound comprises from 40% to 70% by weight of the total liquid crystal composition.

3. A bistable light modulating device as claimed in claim 1 wherein said positive temperature sensitive chiral compound comprises from 0.1% to 30% by weight of the total liquid crystal composition.

4. A bistable light modulating device as claimed in claim 3 wherein said positive temperature sensitive chiral compound is at least one of CB15, S811, S5011, R811, R5011.

5. A bistable light modulating device as claimed in claim 1 wherein said negative temperature sensitive chiral compound comprises from 0.1% to 30% by weight of the total liquid crystal composition.

6. A bistable light modulating device as claimed in claim 5 wherein said negative temperature sensitive chiral compound has the same handedness as said positive temperature sensitive chiral compound.

7. A bistable light modulating device having a reflection wavelength which does not vary with temperature according to claim 1 wherein said bimesogenic compound comprises 5% to 50% of the total mass of the liquid crystal composition.

8. A bistable light modulating device as claimed in claim 1 wherein said liquid crystal layer has a thickness of 2 to 100 μm.

9. The bistable light modulator of claim 8, wherein said liquid crystal layer has a thickness of 5-50 μm.

10. A bistable light modulating device as claimed in claim 1 wherein said first transparent conductive substrate and/or said second transparent conductive substrate is made of a transparent substrate and a transparent conductive electrode overlying said transparent substrate.

11. A bistable light modulating device as claimed in claim 10 wherein said transparent conductive substrate is any one of flat glass, tempered glass, semi-tempered glass, float glass, PET film, PTFE film.

12. The bistable light modulating device of claim 10 wherein said transparent conductive electrode is made of at least one of metal oxide thin film, metal nanowire conductive thin film, metal mesh, and carbon-based conductive thin film.

13. A bistable light modulating device as claimed in claim 1 wherein an alignment layer is provided between said first transparent conductive substrate and said liquid crystal layer and/or between said second transparent conductive substrate and said liquid crystal layer.

14. A bistable light modulating device having a reflection wavelength which does not vary with temperature according to claim 13 wherein said alignment layer has an alignment type of substantially planar orientation or substantially homeotropic orientation.

15. A bistable light modulating device as defined in claim 14 wherein said alignment layer is oriented by rubbing, photoalignment, oblique evaporation, or LB film.

16. The bistable light modulating device of claim 13, wherein said alignment layer is made of any of polyimide, silicone, and PVB.

17. A method for preparing a bistable light modulator device according to any one of claims 1-16 by vacuum infusion process, comprising the steps of:

s1, arranging the first transparent conductive base layer and the second transparent conductive base layer in a contraposition mode with inner surfaces opposite to each other;

s2, attaching the first transparent conductive base layer and the second transparent conductive base layer which are arranged in an aligned mode through frame sealing glue, and adding a spacer between the two transparent conductive base layers to control the gap between the two transparent conductive base layers;

s3, filling a liquid crystal composition in the gap between the two transparent conductive base layers to form a liquid crystal layer, wherein the liquid crystal composition comprises a nematic liquid crystal compound, a positive temperature sensitive chiral compound, a negative temperature sensitive chiral compound and a bimesogenic compound, and the bistable light modulation device comprises two stable states with zero electric field: a transmitted state that substantially transmits incident light and a foggy state that substantially scatters incident light;

and S4, curing the seal to form the bistable light modulator.

18. The method of claim 17, wherein an alignment layer is formed on the surface of the first transparent conductive substrate or the second transparent conductive substrate adjacent to the liquid crystal layer by alignment along a direction; and carrying out orientation arrangement on the alignment layer along the direction.

19. An ODF process for manufacturing a bistable light modulator device according to any of claims 1-16, comprising the steps of:

s1, coating the frame sealing glue on the first transparent conductive base layer;

s2, adding spacers into the liquid crystal composition, mixing and stirring uniformly, and dripping the mixture on the first transparent conductive base layer according to a proper single-drop amount and single-drop interval; the liquid crystal composition comprises a nematic liquid crystal compound, a positive temperature sensitive chiral compound, a negative temperature sensitive chiral compound and a bimesogenic compound, wherein the bistable light modulator comprises two states with stable zero electric field: a transmitted state that substantially transmits incident light and a foggy state that substantially scatters incident light;

s3, attaching the second transparent conductive base layer to the first transparent conductive base layer by frame sealing glue according to alignment arrangement;

and S4, curing the frame sealing glue to form the bistable dimming device.

20. The method of claim 19, wherein an alignment layer is formed on the surface of the first transparent conductive substrate or the second transparent conductive substrate adjacent to the liquid crystal layer by alignment along a direction; and carrying out orientation arrangement on the alignment layer along the direction.