CN113777841B

CN113777841B - Reflector and preparation method and application thereof

Info

Publication number: CN113777841B
Application number: CN202110929015.6A
Authority: CN
Inventors: 赵威; 韦群美; 吕朋荣; 迪克·杨·波尔; 周国富
Original assignee: South China Normal University; Shenzhen Guohua Optoelectronics Co Ltd
Current assignee: South China Normal University; Shenzhen Guohua Optoelectronics Co Ltd
Priority date: 2021-08-13
Filing date: 2021-08-13
Publication date: 2024-04-19
Anticipated expiration: 2041-08-13
Also published as: CN113777841A

Abstract

The invention discloses a reflector and a preparation method and application thereof, wherein the reflector sequentially comprises a first light-transmitting substrate, a light-adjusting layer and a second light-transmitting substrate, the light-adjusting layer comprises a liquid crystal polymer layer and a small molecule liquid crystal layer, the liquid crystal polymer layer and the small molecule liquid crystal layer are formed by layering liquid crystal mixtures through photopolymerization induction, and the chiral rotation directions of the liquid crystal polymer layer and the small molecule liquid crystal layer are opposite. The reflector disclosed by the invention has the advantages of high reflectivity, adjustable reflectivity and rotation direction of reflected light, easy acquisition of materials required for preparation, simple preparation process, no need of washing or filling, and suitability for industrial production.

Description

Reflector and preparation method and application thereof

Technical Field

The invention relates to the technical field of liquid crystal materials, in particular to a reflector, a preparation method and application thereof.

Background

Currently, liquid crystal reflective devices are widely used in displays, lasers, smart windows, biosensors, and the like. Most of the existing liquid crystal reflecting devices are based on selective reflection of cholesteric liquid crystal, and the left-handed circularly polarized light (L-CPL) or right-handed circularly polarized light (R-CPL) is reflected by the adjusting device through selecting the rotation direction of the added chiral dopant. However, the L-CPL or R-CPL accounts for only 50% of the natural light, so that the reflectivity of the liquid crystal reflecting device is only 50% at most, and the remaining 50% of the natural light is transmitted. Meanwhile, due to the fact that the polymer is not matched with the refractive index of the small-molecule liquid crystal, scattering phenomenon is caused, and the reflectivity of the liquid crystal reflecting device is greatly reduced.

When the liquid crystal reflective device can reflect both handedness of circularly polarized light at the same time, the 50% reflection limit is exceeded, a phenomenon called superreflection. Nowadays, the method for preparing the super-reflective liquid crystal device comprises the following steps: (1) Stacking a plurality of layers of liquid crystal polymer films with opposite rotation directions to obtain a super-reflecting device capable of reflecting left-handed circularly polarized light and right-handed circularly polarized light simultaneously; (2) The liquid crystal polymer layer is prepared, liquid components in the liquid crystal polymer layer are washed out, and finally liquid components with opposite rotation directions to the liquid crystal polymer layer are filled, so that the ultra-reflection device is obtained. The preparation method of the super-reflection device is complex in process and complex in operation.

Disclosure of Invention

The present invention aims to solve at least one of the technical problems existing in the prior art. Therefore, the invention provides the reflector which has the characteristics of simple preparation process and simple operation.

The invention also provides a preparation method of the reflector.

The invention also provides application of the reflector.

According to the first aspect of the invention, a reflector is provided, which sequentially comprises a first light-transmitting substrate, a light-adjusting layer and a second light-transmitting substrate, wherein the light-adjusting layer comprises a liquid crystal polymer layer and a small molecule liquid crystal layer, the liquid crystal polymer layer and the small molecule liquid crystal layer are formed by photo-polymerization induced layering of a liquid crystal mixture, and the chiral rotation directions of the liquid crystal polymer layer and the small molecule liquid crystal layer are opposite.

According to the reflector provided by the embodiment of the invention, the reflector has at least the following beneficial effects: the invention prepares the liquid crystal polymer layer and the micromolecular liquid crystal layer with opposite chiral rotation directions by utilizing the photopolymerization induced layering effect, thereby obtaining the ultra-reflection device. The invention has the advantages of simple and easily obtained required materials, simple and feasible preparation process, short time consumption in the preparation process, convenient operation, high reflectivity (higher than 90 percent) of the reflector, excellent performance, capability of ensuring good reflection effect and lasting effect, and can be applied to industrial production by using low-cost materials and simple preparation flow.

In addition, the reflector disclosed by the invention has the characteristics of high reflectivity and adjustable reflection light rotation direction when being heated or powered (the dimming layer has temperature response and electric response), and specifically comprises the following steps: since the chiral directions of the liquid crystal polymer layer and the small molecule liquid crystal layer are opposite, the reflector can reflect left circularly polarized light and right circularly polarized light at room temperature in a state of no power-up, and the reflector has an effect of super reflection. By regulating and controlling the small-molecule liquid crystal layer, the reflector is heated or an electric field is applied, the small-molecule liquid crystal layer is heated to be in an isotropic state, the small-molecule liquid crystal layer is electrified to be in an orientation zoom cone state, the liquid crystal polymer layer is hardly affected, at the moment, the reflector cannot reflect left-handed circularly polarized light (or right-handed circularly polarized light), the reflectivity of the reflector is less than 50%, and no super-reflection effect is achieved. The temperature is reduced to room temperature or the electric field is removed, the small molecule liquid crystal layer returns to the initial state, at the moment, the small molecule liquid crystal layer can reflect left circularly polarized light (or right circularly polarized light), the polymer layer reflects right circularly polarized light (or left circularly polarized light), the reflectivity of the reflector is more than 90%, and the reflector achieves the super-reflection effect. Wherein, the reflection band of the reflector can be realized by adjusting the type or content of chiral raw materials in the liquid crystal mixture.

In some embodiments of the invention, the liquid crystal polymer layer is a cholesteric liquid crystal polymer network.

In some embodiments of the invention, the small molecule liquid crystal layer is a cholesteric liquid crystal.

In some embodiments of the invention, the liquid crystal mixture comprises polymerizable liquid crystal monomers, non-polymerizable liquid crystal small molecules, a photoinitiator, a polymerizable chiral dopant, and a non-polymerizable chiral dopant, wherein the chiralities of the polymerizable chiral dopant and the non-polymerizable chiral dopant are opposite.

According to the embodiment, the method only needs one-step illumination polymerization (ultraviolet exposure can be adopted), so that the two cholesteric liquid crystals with opposite chiralities can be separated to achieve the aim of super reflection, and the cholesteric liquid crystals with different chiralities are not required to be heated and applied to induce gradual formation in the preparation process. Specifically, the photopolymerization-induced delamination process may be: light (which may be ultraviolet exposure) causes polymerizable monomers (including polymerizable liquid crystal monomers, polymerizable chiral dopants) in the liquid crystal mixture to be initiated on the side near the light source (upper layer) at a faster rate, causing the polymerizable monomers to diffuse to the side near the light source, resulting in the formation of a liquid crystal polymer layer (right-handed or left-handed) on the side near the light source (upper layer). At the same time, since the polymerizable monomer (containing a right-handed or left-handed polymerizable chiral dopant) diffuses to the side (upper layer) near the light source such that the non-polymerizable chiral dopant (left-handed or right-handed) is squeezed to the side (lower layer) far from the light source, the content of the non-polymerizable chiral dopant (left-handed or right-handed) is high on the side (lower layer) far from the light source, and thus a small-molecule liquid crystal layer (left-handed or right-handed) is formed on the side (lower layer) far from the light source.

Meanwhile, the reflector has reversible temperature response, and the light transmission is regulated and controlled by a heating method, wherein the temperature response is based on the liquid crystal temperature range of the material. Because the main components of the small molecule liquid crystal layer are small molecule liquid crystal and non-polymerizable chiral dopants, when the temperature of the reflector is lower (such as 25 ℃), the liquid crystal of the small molecule liquid crystal layer is in an anisotropic liquid crystal phase and is arranged parallel to the light-transmitting substrate, and at the moment, the reflector can reflect left-handed circularly polarized light and right-handed circularly polarized light simultaneously. When the temperature of the reflector is raised (for example, the temperature is raised to 50 ℃), the temperature is higher than the clearing temperature of the small molecule liquid crystal, the liquid crystal of the small molecule liquid crystal layer is converted from the original anisotropic liquid crystal phase into an isotropic liquid state, the clearing temperature is raised due to the existence of a polymer network in the liquid crystal polymer layer, molecules still maintain the arrangement of cholesteric phases parallel to the transparent substrate, and the reflector only can reflect right-handed circularly polarized light (or left-handed circularly polarized light). When the temperature of the reflector is reduced to a lower temperature (such as 25 ℃), the liquid crystal of the small molecule liquid crystal layer is changed from the original isotropic liquid state to the anisotropic liquid crystal state, and is changed back to the alignment parallel to the transparent substrate, and the liquid crystal polymer layer still maintains the parallel alignment, so that the reflector can reflect the left-handed circularly polarized light and the right-handed circularly polarized light at the same time.

In some preferred embodiments of the present invention, the liquid crystal polymer layer comprises a material including polymerizable liquid crystal monomers, polymerizable chiral dopants, photoinitiators, and non-polymerizable liquid crystal small molecules.

In some preferred embodiments of the invention, the materials of the small molecule liquid crystal layer include non-polymerizable liquid crystal small molecules and non-polymerizable chiral dopants.

In some preferred embodiments of the present invention, the ratio of the parts by weight of the polymerizable liquid crystalline monomer and the photoinitiator is (30-45): 0.1-1.

In some preferred embodiments of the invention, the ratio of the parts by weight of the polymerizable liquid crystal monomer to the small non-polymerizable liquid crystal molecules is (30-45): 45-60.

In some preferred embodiments of the invention, the ratio of the polymerizable liquid crystalline monomer to the polymerizable chiral dopant in parts by mass is (30-45): (1-9).

In some preferred embodiments of the invention, the ratio of the mass fraction of the non-polymerizable liquid crystal small molecules to the non-polymerizable chiral dopants is (45-60): (1-9).

In some more preferred embodiments of the present invention, the ratio of the mass parts of the polymerizable liquid crystal monomer, the positive liquid crystal, the photoinitiator, the polymerizable chiral dopant, and the non-polymerizable chiral dopant is (30-45): 45-60): 0.1-1): 1-9. The wave band of the reflection peak is adjusted by regulating the concentration of the chiral dopant. The height of one period of the helical form of the cholesteric liquid crystal molecules is called the pitch (rp), and the direction of rotation of the rp defines the chirality of the cholesteric liquid crystal. The pitch, helical twist direction, together with the refractive index of the cholesteric phase determine the optical properties of the cholesteric liquid crystal. The pitch of the cholesteric liquid crystal is related to the ability of the chiral dopant to induce a continuous uniform Helical Twist (HTP) of the nematic liquid crystal director, the concentration of chiral dopant (c) being:

P＝1/(HTP*c)

The periodic helical structure of cholesteric liquid crystals can produce Bragg reflection effect on light, so that the cholesteric liquid crystals have specific wave band selective reflection. The reflection wavelength (λ) depends on the pitch (P) of the cholesteric liquid crystal and the average refractive index (n) of the liquid crystal, and is related as follows:

λ＝n*P

When the concentration of chiral dopants is increased simultaneously, the pitch P of the cholesteric liquid crystal decreases, and the reflection wavelength decreases, and vice versa. In addition, the direction of rotation of P determines that in theory a layer of cholesteric liquid crystal can only reflect circularly polarized light in the same direction as the twist, with a reflectivity of only 50% at maximum. Meanwhile, different kinds of chiral dopants have different Helical Twisting Powers (HTPs). The shorter the reflection peak at the same content when the HTP of the chiral dopant is larger, whereas the longer the reflection peak at the same content when the HTP of the chiral dopant is smaller. When the chiral dopant is the same, the reflection band blue shifts as the chiral dopant content increases; conversely, if the chiral dopant content is reduced, the reflection band is red shifted.

Therefore, the invention can make the reflector have the performance of super reflectivity (50%) and temperature response in the visible light band and the infrared band by adjusting the types of chiral dopants and the concentration of chiral dopants and adjusting the wave band of the reflection peak, has excellent performance and can be dynamically adjusted and controlled along with the temperature.

In some preferred embodiments of the invention, the small non-polymerizable liquid crystal molecules comprise positive liquid crystals.

In some more preferred embodiments of the invention, the liquid crystal mixture comprises polymerizable liquid crystal monomers, positive liquid crystals, a photoinitiator, polymerizable chiral dopants, and non-polymerizable chiral dopants.

In some more preferred embodiments of the invention, the liquid crystal mixture comprises polymerizable liquid crystal monomers, positive liquid crystals, a photoinitiator, a right-handed polymerizable chiral dopant, and a left-handed non-polymerizable chiral dopant.

In some more preferred embodiments of the present invention, the starting materials for the liquid crystal polymer layer include polymerizable liquid crystal monomers, right-handed polymerizable chiral dopants, photoinitiators, and positive liquid crystals.

In some more preferred embodiments of the invention, the liquid crystal polymer layer comprises a cholesteric liquid crystal polymer network, the liquid crystal polymer layer being formed from polymerizable liquid crystal monomers, right-handed polymerizable chiral dopants, photoinitiators, and positive liquid crystals.

By the above embodiment, the liquid crystal polymer layer has a right-handed polymer structure, and can reflect right-handed circularly polarized light.

In some more preferred embodiments of the invention, the starting materials for the small molecule liquid crystal layer include a positive liquid crystal and a left-handed non-polymerizable chiral dopant.

In some more preferred embodiments of the invention, the small molecule liquid crystal layer is a left-handed cholesteric liquid crystal layer consisting of positive liquid crystals and a left-handed non-polymerizable chiral dopant.

By the embodiment, the small-molecule liquid crystal layer is of a left-handed cholesteric liquid crystal structure, and can reflect left-handed circularly polarized light.

In some more preferred embodiments of the invention, the liquid crystal polymer layer is a cholesteric liquid crystal polymer network formed from polymerizable liquid crystal monomers, a right-handed polymerizable chiral dopant, a photoinitiator, and a positive liquid crystal, and the small molecule liquid crystal layer is a left-handed cholesteric liquid crystal composed of a positive liquid crystal and a left-handed non-polymerizable chiral dopant.

By the above embodiment, the right-handed polymerizable chiral dopant (which may be a right-handed chiral liquid crystal monomer), the polymerizable liquid crystal monomer, and the left-handed non-polymerizable chiral dopant are mixed together, and before the polymerization under no illumination, the right-handed polymerizable chiral dopant has a higher helical twist force than that before the polymerization under no illumination, the right-handed polymerizable chiral dopant is dominant, the left-handed twist force is masked due to the racemization, the reflector can reflect only right-handed circularly polarized light, and the reflectivity is less than 50%. Light (which may be ultraviolet exposure) causes the polymerizable liquid crystal monomer to be initiated on the side near the light source (upper layer) at a faster rate, such that the polymerizable monomer (including polymerizable liquid crystal monomer, right-handed polymerizable chiral dopant) diffuses to the side near the light source, resulting in the formation of a right-handed liquid crystal polymer layer on the side near the light source (upper layer). Meanwhile, since the polymerizable monomer diffuses to the side (upper layer) close to the light source such that the left-handed non-polymerizable chiral dopant is pushed to the side (lower layer) far from the light source, the content of the left-handed non-polymerizable chiral dopant is high, and thus a left-handed small-molecule liquid crystal layer is formed on the side (lower layer) far from the light source.

In some more preferred embodiments of the present invention, the ratio of the mass parts of the polymerizable liquid crystal monomer, the positive liquid crystal, the photoinitiator, the polymerizable chiral dopant, and the non-polymerizable chiral dopant is (30-45): 45-60): 0.1-1): 1-9.

In some preferred embodiments of the present invention, the polymerizable liquid crystal monomer comprises an acrylic monomer.

In some more preferred embodiments of the present invention, the polymerizable liquid crystal monomer includes at least one of a monofunctional acrylate or a difunctional acrylate.

It should be noted that "functional group" specifically refers to a carbon-carbon double bond, and the functional group is mainly used for photopolymerization, particularly ultraviolet polymerization. The invention enables the liquid crystal polymer layer and the small molecule liquid crystal layer to coexist and exist stably by adjusting the proportion of each component.

In some more preferred embodiments of the present invention, the monofunctional acrylate comprises at least one of HCM-020、HCM-021、HCM-022、HCM-039、HCM-040、HCM-042、HCM-043、HCM-044、HCM-045、HCM-046、HCM-047、HCM-048、HCM-049、HCM-050、HCM-059、HCM-062、HCM-065、HCM-066、HCM-074、HCM-075、HCM-076、HCM-078、HCM-079、HCM-080、HCM-083、HCM-091、HCM-108、HCM-109、HCM-110、HCM-116、HCM-126 or HCM-127.

The reagent is available from market, and manufacturers include Jiangsu and Cheng display technology Co., ltd.

In some more preferred embodiments of the present invention, the difunctional acrylates include at least one of HCM-002, HCM-008, HCM-006, HCM-009, HCM-026, HCM-028, HCM-053, HCM-072, HCM-087, or HCM-125.

In some preferred embodiments of the invention, the polymerizable chiral dopant that is right-handed comprises at least one of HCM-006 or RM 96.

In some preferred embodiments of the invention, the non-polymerizable chiral dopant that is left-handed comprises at least one of S811, S1011, S5011 or S6N.

The reagent can be purchased from the market, and manufacturers comprise Jiangsu Hecheng display technology and technology Co., beijing eight hundred million space time liquid crystal technology and technology Co., ltd.

In some preferred embodiments of the invention, the photoinitiator comprises an ultraviolet light initiator.

In some more preferred embodiments of the present invention, the photoinitiator comprises at least one of Irgacure-127, irgacure-1173, irgacure-184, irgacure-819, irgacure-651, irgacure-369, or Irgacure-2959.

The above reagents are commercially available, and manufacturers include xien Site, merck, etc.

In some preferred embodiments of the invention, the positive liquid crystal comprises at least one of 5CB, E7 or HTW 138200-100.

The reagent is available from market, and manufacturers include Jiangsu and Chengzhi technology Co., ltd, merck, etc.

In some embodiments of the invention, the dimming layer has a thickness of 30um to 100um.

In some embodiments of the present invention, the first transparent substrate has a light transmittance ranging from 95% to 100%.

In some embodiments of the present invention, the light transmittance of the second light-transmitting substrate ranges from 95% to 100%.

In some embodiments of the present invention, a first parallel alignment layer is disposed on a side of the first transparent substrate facing the liquid crystal mixture, and a second parallel alignment layer is disposed on a side of the second transparent substrate facing the liquid crystal mixture.

By the above embodiment, the first parallel alignment layer and the second parallel alignment layer may be completely structurally identical. The preparation method comprises the steps of preparing materials and preparing processes.

In some preferred embodiments of the present invention, the first parallel alignment layer comprises at least one of polyvinyl alcohol or polyimide.

In some preferred embodiments of the present invention, the raw material of the second parallel alignment layer includes at least one of polyvinyl alcohol or polyimide.

In some preferred embodiments of the present invention, the dimming layer is located between the first parallel alignment layer and the second parallel alignment layer.

In some more preferred embodiments of the present invention, the first transparent substrate, the first parallel alignment layer, the dimming layer, the second parallel alignment layer, and the second transparent substrate are sequentially stacked.

In some more preferred embodiments of the present invention, the first transparent substrate, the first parallel alignment layer, the liquid crystal polymer layer, the small molecule liquid crystal layer, the second parallel alignment layer, and the second transparent substrate are sequentially stacked.

In some embodiments of the invention, the first transparent substrate is a first transparent conductive substrate.

In some embodiments of the invention, the second transparent substrate is a second transparent conductive substrate.

In some embodiments of the present invention, the first transparent substrate is a first transparent conductive substrate, and the second transparent substrate is a second transparent conductive substrate.

In some preferred embodiments of the present invention, the liquid crystal mixture comprises polymerizable liquid crystal monomers, positive liquid crystals, a photoinitiator, polymerizable chiral dopants, and non-polymerizable chiral dopants.

Through the embodiment, the reflector has reversible temperature response and reversible electric response, has excellent performance, can be dynamically regulated and controlled along with temperature and an electric field, is easier to regulate and control, expands the application range of the reflector, and can be applied to the technical fields of optics and display. In practical application, the reflector with different reflection bands can be obtained by adjusting the content of chiral dopants according to the needs, has the properties of super reflectivity (reflectivity higher than 90%) and temperature response and electric response in the visible light band and the infrared light band, can have reversible cycling temperature response and electric response, namely realizes the regulation and control of transmitted light by a heating or power-up method, improves the equipment performance, can be applied to industrial production with lower materials and simple preparation flow, and has good application prospect.

The principle of electrical response of reflectors is based on the mechanism that positive liquid crystal molecules tend to align parallel to the direction of an electric field under the action of the electric field. The reflector is polymerized to form a liquid crystal polymer layer and a small molecule liquid crystal layer. Because the main components of the small molecule liquid crystal layer are positive liquid crystal and non-polymerizable chiral dopants, when the electric field U=0V is accessed, the liquid crystal of the small molecule liquid crystal layer is arranged parallel to the transparent conductive substrate, the device is transparent, and at the moment, the reflector can reflect left-handed circularly polarized light and right-handed circularly polarized light simultaneously. When an electric field u+.0v is applied (e.g., u=120v), the positive liquid crystal molecules are changed from the original alignment parallel to the transparent conductive substrate to the focal conic alignment, and the liquid crystal molecules in the liquid crystal polymer layer still maintain the cholesteric alignment parallel to the transparent conductive substrate due to the existence of the polymer network. When the electric field u=0v is removed, the positive liquid crystal molecules are converted back to the alignment parallel to the transparent conductive substrate by the alignment layer, and the liquid crystal polymer layer still maintains the parallel alignment, so that the device can reflect both left-handed circularly polarized light and right-handed circularly polarized light.

From above, the reflector disclosed by the invention has the characteristics of high reflectivity and adjustable reflection light rotation direction when being heated or powered, and specifically comprises the following steps: since the chiral directions of the liquid crystal polymer layer and the small molecule liquid crystal layer are opposite, the reflector can reflect left circularly polarized light and right circularly polarized light at room temperature in a state of no power-up, and the reflector has an effect of super reflection. By regulating and controlling the small-molecule liquid crystal layer, the reflector is heated or an electric field is applied, the small-molecule liquid crystal layer is heated to be in an isotropic state, the small-molecule liquid crystal layer is electrified to be in an orientation zoom cone state, the liquid crystal polymer layer is hardly affected, at the moment, the reflector cannot reflect left-handed circularly polarized light (or right-handed circularly polarized light), the reflectivity of the reflector is less than 50%, and no super-reflection effect is achieved. The temperature is reduced to room temperature or the electric field is removed, the small molecule liquid crystal layer returns to the initial state, at the moment, the small molecule liquid crystal layer can reflect left circularly polarized light (or right circularly polarized light), the polymer layer reflects right circularly polarized light (or left circularly polarized light), the reflectivity of the reflector is more than 90%, and the reflector achieves the super-reflection effect. Wherein, the reflection band of the reflector can be realized by adjusting the type or content of chiral raw materials in the liquid crystal mixture.

In some preferred embodiments of the present invention, the first transparent conductive substrate, the first parallel alignment layer, the dimming layer, the second parallel alignment layer, and the second transparent conductive substrate are sequentially stacked.

In some more preferred embodiments of the present invention, the first transparent conductive substrate, the first parallel alignment layer, the liquid crystal polymer layer, the small molecule liquid crystal layer, the second parallel alignment layer, and the second transparent conductive substrate are sequentially stacked.

In some preferred embodiments of the present invention, the reflector further includes a power component, and two poles of the power component are electrically connected to the first transparent conductive substrate and the second transparent conductive substrate, respectively.

In some more preferred embodiments of the invention, the power supply assembly comprises an ac power source with voltage regulating means integrated thereon.

Through the implementation mode, the voltage regulating device is integrated on the alternating current power supply, and the power supply voltage can be directly regulated. The two poles of the power supply component are respectively and electrically connected with the first transparent conductive substrate and the second transparent conductive substrate, and voltage is applied between the first transparent conductive substrate and the second transparent conductive substrate through the power supply component.

In a second aspect of the present invention, a method for manufacturing a reflector is provided, comprising the steps of:

and (3) taking the first light-transmitting substrate and the second light-transmitting substrate, adding a liquid crystal mixture between the first light-transmitting substrate and the second light-transmitting substrate, and illuminating to form a liquid crystal polymer layer and a small molecule liquid crystal layer, namely a dimming layer.

The preparation method of the reflector provided by the embodiment of the invention has at least the following beneficial effects: the preparation method utilizes photopolymerization to induce layering effect to prepare a liquid crystal polymer layer and a small-molecule liquid crystal layer with opposite chiral rotation directions, so that the ultra-reflection device is obtained. The reflecting device belongs to an integrally formed device, has the advantages of simple and easily obtained required materials, simple and feasible preparation process, short time consumption in the preparation process, convenient operation, preparation by simple exposure, no need of washing or filling, and suitability for industrial production and application. Meanwhile, the reflector has high reflectivity (the reflectivity is higher than 90%), excellent performance, good reflection effect and lasting effect, and can be applied to industrial production by low-cost materials and simple preparation flow. In some embodiments of the present invention, the first and second transparent substrates are packaged into a liquid crystal cell, and the liquid crystal cell is filled with a liquid crystal mixture.

In some embodiments of the present invention, the method further includes step S0-1 of preparing a first parallel alignment layer on the first transparent substrate and preparing a second parallel alignment layer on the second transparent substrate with the parallel alignment layer material.

In some more preferred embodiments of the present invention, the first parallel alignment layer is obtained by spin-coating a raw material solution of the first parallel alignment layer on the first light-transmitting substrate.

In some more preferred embodiments of the present invention, the mass fraction of the raw material in the raw material solution of the first parallel alignment layer is 3 to 5%.

In some more preferred embodiments of the present invention, the raw material solution of the first parallel alignment layer is an aqueous solution of a raw material.

In some more preferred embodiments of the present invention, the second parallel alignment layer is obtained by spin-coating an aqueous solution of a raw material of the second parallel alignment layer on the second transparent substrate.

In some more preferred embodiments of the present invention, the mass fraction of the raw material in the raw material solution of the second parallel alignment layer is 3 to 5%.

In some more preferred embodiments of the present invention, the raw material solution of the second parallel alignment layer is an aqueous solution of a raw material.

In some preferred embodiments of the present invention, in step S0-1, an aqueous solution of polyvinyl alcohol is spin-coated on the surfaces of the first and second transparent substrates, respectively, and is rubbed and aligned to obtain a first parallel alignment layer and a second parallel alignment layer.

In some preferred embodiments of the present invention, the method further comprises step S0-2, wherein the first parallel alignment layer and the second parallel alignment layer are disposed opposite to each other, a spacer is disposed on an edge of the first transparent substrate on which the first parallel alignment layer is disposed, the second transparent conductive substrate is disposed on an ultraviolet curable adhesive containing a spacer, and the first transparent substrate and the second transparent substrate are encapsulated into a liquid crystal cell.

In some more preferred embodiments of the invention, a polymerizable liquid crystal monomer, a positive liquid crystal, a chiral dopant (containing a polymerizable chiral dopant, a non-polymerizable chiral dopant) and a photoinitiator are mixed to obtain a liquid crystal mixture, and the liquid crystal mixture is filled into a liquid crystal cell and naturally cooled to room temperature.

In some more preferred embodiments of the invention, the liquid crystal mixture is filled into a liquid crystal cell having parallel alignment layers in each of the same states.

By filling the liquid crystal mixture into the liquid crystal box with the parallel alignment layers under the same state, the alignment effect of the liquid crystal molecules is better, defects in the device are fewer, and the final reflectivity of the reflector is higher.

In some embodiments of the invention, the source of illumination is an ultraviolet light source.

In some preferred embodiments of the invention, the light intensity during illumination is from 0.5 to 120mW cm ^-2.

In some more preferred embodiments of the invention, the light intensity during illumination is from 0.5 to 25mW cm ^-2.

In some preferred embodiments of the invention, the light wavelength during illumination is 280-405nm.

In some more preferred embodiments of the invention, the light wavelength during illumination is 365nm.

In some preferred embodiments of the invention, the illumination time is 5-60 minutes.

In some more preferred embodiments of the invention, the illumination time is 60 minutes.

In a third aspect the invention provides the use of the reflector described above in the fields of construction, furniture, liquid crystal display, laser emission or biosensing.

In some embodiments of the invention, the use of the above-described reflectors in displays, lasers, smart windows or biosensors is proposed.

Drawings

The invention is further described with reference to the accompanying drawings and examples, in which:

FIG. 1 is a schematic view of the structure of the inside of a liquid crystal cell of a reflector in an embodiment of the invention;

FIG. 2 is a schematic diagram of the reflector in a non-energized and 120V AC applied state in an embodiment of the invention;

FIG. 3 is a graph of the transmittance spectrum of a reflector in an unpowered and 120V AC applied state in an embodiment of the invention;

FIG. 4 is a schematic diagram of a reflector in an embodiment of the present invention at room temperature of 25℃and heated to 50 ℃;

FIG. 5 is a graph showing transmittance spectra of reflectors in an embodiment of the present invention at room temperature of 25℃and heated to 50 ℃;

FIG. 6 is a graph showing the results of the amount of chiral dopant required for reflectors in different reflection bands in an embodiment of the present invention;

FIG. 7 is a graph of the transmittance spectra of reflectors of different reflected wave bands in an embodiment of the invention.

Reference numerals: 11. a first transparent conductive substrate; 21. parallel orientation layer one; 31. a liquid crystal polymer layer; 41. a small molecule liquid crystal layer; 22. a second parallel orientation layer; 12. and a second transparent conductive substrate.

Detailed Description

Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to like or similar elements or elements having like or similar functions throughout. The embodiments described below by referring to the drawings are illustrative only and are not to be construed as limiting the invention. In the description of the present invention, it should be understood that references to orientation descriptions such as upper, lower, front, rear, left, right, etc. are based on the orientation or positional relationship shown in the drawings, are merely for convenience of description of the present invention and to simplify the description, and do not indicate or imply that the apparatus or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus should not be construed as limiting the present invention.

In the description of the present invention, the meaning of a number is one or more, the meaning of a number is two or more, and greater than, less than, exceeding, etc. are understood to exclude the present number, and the meaning of a number is understood to include the present number. If one or two are described for the purpose of distinguishing technical features, that is, they are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated or implicitly indicating the precedence of the technical features indicated.

In the description of the present invention, unless explicitly defined otherwise, terms such as arrangement, installation, connection, etc. should be construed broadly and the specific meaning of the terms in the present invention can be reasonably determined by a person skilled in the art in combination with the specific contents of the technical scheme.

In the description of the present invention, the descriptions of the terms "one embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiments or examples. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

The details of the chemical reagents used in the examples of the present invention are as follows:

the polymerizable liquid crystal monomer HCM021 (purchased from Jiangsu and Chemicals Co., ltd.) has the chemical structural formula:

the polymerizable liquid crystal monomer HCM008 (available from Jiangsu and Chemicals Co., ltd.) has the chemical structural formula:

The polymerizable liquid crystal monomer HCM006 (available from Jiangsu and display technologies Co., ltd.) has the chemical structural formula:

The chemical formula of the small molecule liquid crystal 5CB (purchased from Jiangsu and Chemicals Co., ltd.) is:

The chemical structural formula of the non-polymerizable left-handed chiral dopant S1011 (purchased from Jiangsu and Chemicals Co., ltd.) is:

The chemical formula of the photoinitiator Irgacure-651 (purchased from Merck, germany) is:

example 1

The reflector comprises a first transparent conductive substrate 11, a second transparent conductive substrate 12 and a dimming layer, wherein the dimming layer comprises a liquid crystal polymer layer 31 and a micromolecular liquid crystal layer 41 which are prepared by a liquid crystal mixture through a photopolymerization induced layering technology and have opposite chiral rotation directions, and therefore, in particular, the reflector comprises the first transparent conductive substrate 11, a first parallel alignment layer 21, the liquid crystal polymer layer 31, the micromolecular liquid crystal layer 41, a second parallel alignment layer 22 and the second transparent conductive substrate 12 which are sequentially stacked. The liquid crystal mixture comprises polymerizable liquid crystal monomers, positive liquid crystal, a photoinitiator, a right-handed polymerizable chiral dopant and a left-handed non-polymerizable chiral dopant. The liquid crystal polymer layer is of a right-handed polymer structure, specifically comprises a right-handed cholesteric liquid crystal polymer network, and the small-molecule liquid crystal layer is of a left-handed liquid crystal layer, specifically is of a left-handed cholesteric liquid crystal.

The reflector also comprises a power supply component, wherein two poles of the power supply component are respectively and electrically connected with the first transparent conductive substrate 11 and the second transparent conductive substrate 12.

The power supply assembly comprises an alternating current power supply, a voltage regulating device is integrated on the alternating current power supply, and the voltage regulating device is integrated on the alternating current power supply, so that the power supply voltage can be directly regulated. The two poles of the power supply component are respectively and electrically connected with the first transparent conductive substrate and the second transparent conductive substrate, and voltage is applied between the first transparent conductive substrate and the second transparent conductive substrate through the power supply component.

The preparation method of the reflector comprises the following steps:

(1) The first transparent conductive substrate and the second transparent conductive substrate are oppositely arranged. And respectively spin-coating a polyvinyl alcohol aqueous solution (the mass fraction of the polyvinyl alcohol is 5.0%) on the surfaces of the first transparent conductive substrate and the second transparent conductive substrate, and rubbing and orienting to obtain a first parallel orientation layer and a second parallel orientation layer. The spacer is placed on the surface edge of the first transparent conductive substrate provided with the parallel orientation layer I, the second transparent conductive substrate is placed on ultraviolet curing glue containing the spacer, and the first transparent conductive substrate and the second transparent conductive substrate are packaged into a liquid crystal box.

(2) Under a yellow light environment (other light sources which emit light without ultraviolet rays can be used), weighing 0.0300g of crosslinkable liquid crystal monomer HCM021, 0.0110g of crosslinkable liquid crystal monomer HCM008, 0.0047g of crosslinkable right-handed chiral liquid crystal monomer HCM006, 0.0019g of left-handed chiral dopant S1011, 0.0534g of 5CB and 0.0005g of photoinitiator Irgacure-651, placing into a brown bottle, adding 2ml of dichloromethane to promote dissolution, placing the brown bottle into a 60 ℃ and stirring and heating for 5 hours to ensure that the solvent volatilizes completely, and simultaneously stirring uniformly at a rotating speed of 200r/S to ensure that the liquid crystal material mixture is converted into an isotropic liquid crystal mixture and the viscosity of the liquid crystal mixture is reduced. Then, the liquid crystal material mixture is injected into a liquid crystal box at the temperature, and is kept stand and cooled to room temperature, and is solidified for 60 minutes by ultraviolet light with the intensity of 1.5mW cm ^-2 and the wavelength of 365nm, so that the cholesteric liquid crystal reflector with good orientation and super-reflection optical characteristics is obtained.

Example 2

A reflector differing from example 1 in the preparation method: the UV curing adhesive and a spacer with the thickness of 50 mu m are used for setting a packaging frame, and ultraviolet light with the intensity of 25mW cm ^-2 and the wavelength of 365nm is used for packaging to prepare the liquid crystal box.

Example 3

A reflector differing from example 1 in the preparation method: filling the liquid crystal mixture into a liquid crystal box on a hot table at 60 ℃ through capillary force, preserving heat for 30min to enable the liquid crystal to be well oriented, and naturally cooling to room temperature; and then curing for 1h under ultraviolet light of 0.5mW cm ^-2 to prepare the liquid crystal reflection device.

Example 4

Reflectors I-III were prepared separately, all differing from example 1 in the content of chiral dopants, the specific content being given in Table 1 below:

table 1 reflectors made with different amounts of reflector chiral dopants

It should be noted that:

1. The reflector IV is the reflector prepared in example 1;

2. the mass percent (wt.%) in table 1 refers to the mass percent of each chiral dopant to the liquid crystal mixture.

Test examples

This test example tests the performance of the reflectors prepared in examples 1-4. Wherein:

The reflectors prepared in example 1 were tested for transmittance in the state of no power and 120V ac applied, and the test results are shown in fig. 3, under the following conditions: the unpowered state was tested using PERKINELMER LAMBDA 950,950 ultraviolet spectrophotometer: the incident light is unpolarized light, the temperature is 25 ℃, and the voltage is 0V; power-on state: the incident light was unpolarized light at 25℃and a voltage of 120V.

The reflectors prepared in example 1 were tested for transmittance at room temperature of 25 c and at a temperature of 50 c, and the test results are shown in fig. 5, under the following conditions: using PERKINELMER LAMBDA 950,950 uv spectrophotometer test, room temperature state: the incident light is unpolarized light, the temperature is 25 ℃, and the voltage is 0V; heating state: the incident light was unpolarized light at 50℃and a voltage of 0V.

The reflectors prepared in example 1 and the reflectors prepared in example 4 were tested for transmittance in different reflected wave bands, and the test results are shown in fig. 7, under the following test conditions: the incident light was unpolarized, measured using PERKINELMER LAMBDA 950,950 ultraviolet spectrophotometer, at 25 c and 0V voltage.

As shown in fig. 2 and 3, the electric response principle of the reflector is based on a mechanism that positive liquid crystal molecules tend to be aligned parallel to the direction of an electric field under the action of the electric field. The reflector is polymerized to form a liquid crystal polymer layer and a small molecule liquid crystal layer. Because the main components of the small molecule liquid crystal layer are positive liquid crystal and left-handed non-polymerizable chiral dopants, when the electric field U=0V is accessed, the liquid crystal of the small molecule liquid crystal layer is arranged parallel to the transparent conductive substrate, the device is transparent, and the device can reflect left-handed circularly polarized light and right-handed circularly polarized light at the same time. When the electric field u=120v is accessed, the positive liquid crystal molecules are changed from the original orientation parallel to the transparent conductive substrate to the focal conic orientation, and the liquid crystal molecules in the liquid crystal polymer layer still maintain to be arranged parallel to the transparent conductive substrate due to the existence of the polymer network, and the device can be kept in a fuzzy state, and at the moment, the reflector can only reflect right-handed circularly polarized light. When the electric field u=0v is removed, the positive liquid crystal molecules are transformed back to the alignment parallel to the transparent conductive substrate by the alignment layer, and the liquid crystal polymer layer maintains the parallel alignment, and the reflector can reflect both left circularly polarized light and right circularly polarized light.

Because the positive liquid crystal is used in the invention, the reflectivity of the electric field acting reflector to the left-handed circularly polarized light is reduced or even eliminated, and the reflection influence to the right-handed circularly polarized light is small, so that the reflectivity of the reflector to the unpolarized light is reduced to below 50%, and the reflectivity is reversibly restored to above 90% after the electric field is removed.

As shown in fig. 4 and 5, the temperature response of the reflector is based on the liquid crystal temperature range of the material. Because the main components of the small molecule liquid crystal layer are small molecule liquid crystal and left-handed non-polymerizable chiral dopant, when the device temperature is 25 ℃, the liquid crystal of the small molecule liquid crystal layer is in an anisotropic liquid crystal phase and is arranged parallel to the transparent conductive substrate, and at the moment, the reflector can reflect left-handed circularly polarized light and right-handed circularly polarized light simultaneously. When the temperature of the reflector is raised to 50 ℃, the temperature is higher than the clearing point temperature of the small molecule liquid crystal, the liquid crystal of the small molecule liquid crystal layer is converted into an isotropic liquid state from the original anisotropic liquid crystal phase, the clearing point temperature is raised due to the existence of a polymer network in the liquid crystal polymer layer, and the molecules still maintain the arrangement of cholesteric phases parallel to the transparent conductive substrate, so that the reflector can only reflect right-handed circularly polarized light. When the temperature of the reflector is reduced to 25 ℃, the original isotropic liquid state is converted into an anisotropic liquid crystal state, the liquid crystal state is converted back to an orientation parallel to the transparent conductive substrate, and the liquid crystal polymer layer still maintains the parallel orientation, so that the reflector can reflect left-handed circularly polarized light and right-handed circularly polarized light at the same time.

The invention uses polymerizable dextrorotatory chiral liquid crystal monomer, polymerizable liquid crystal monomer, positive liquid crystal and non-polymerizable levorotatory chiral dopant to mix together, the dextrorotatory polymerizable chiral dopant is dominant at the moment because the spiral torsion force of the dextrorotatory chiral monomer is larger before non-illumination polymerization, the levorotatory torsion force is covered due to racemization, the reflector only can reflect dextrorotatory circular polarized light, and the reflectivity is less than 50%. The ultraviolet exposure causes the polymerizable monomer to be initiated at a faster rate on the side closer to the light source (upper layer) such that the polymerizable monomer diffuses to the side closer to the light source, resulting in the upper layer forming a right-handed liquid crystal polymer layer. Meanwhile, since the right-handed polymerizable monomer diffuses to the upper layer so that the left-handed chiral dopant is squeezed to the side (lower layer) away from the light source, the content of the left-handed chiral dopant in the lower layer is high, and thus a left-handed small molecule liquid crystal layer is formed in the lower layer.

The invention realizes coexistence of two components with opposite chiralities in ultraviolet irradiation polymerization, avoids racemization, can reflect two kinds of circularly polarized light with the same rotation direction, and improves the reflectivity of the reflector; the liquid crystal polymer layer and the micromolecular layer are formed after ultraviolet irradiation polymerization, so that the compatibility is good, and substances are not separated out due to poor solubility; meanwhile, the invention has good stability, the device can reflect two kinds of rotary circularly polarized light after ultraviolet irradiation polymerization, and can be reversibly returned to an initial state and stably exist after heating and electrifying. Meanwhile, in order to meet the actual needs, the invention can adjust the wave band position of the reflection peak according to the concentration of the chiral dopant, so that the reflector has super reflection (the reflectivity is more than 90%) in the visible light wave band and the infrared wave band.

The invention can adjust the wave band position of the reflection peak according to the concentration of the chiral dopant, so that the reflector has the functions of super reflection (the reflectivity is more than 90 percent), temperature response and electric response in the visible light wave band and the infrared wave band. The method comprises the steps of heating to change a small molecular layer from a cholesteric liquid crystal state with anisotropy into an isotropic state, so that the small molecular layer cannot reflect left-handed circularly polarized light, or electrifying to change the small molecular layer from the cholesteric liquid crystal state with parallel textures into a scattering state, so that the capability of the small molecular layer for reflecting the left-handed circularly polarized light is weakened, and the two processes are reversible, so that the regulation and control of transmitted light are realized. The preparation method has the advantages of easily obtained required materials, simple and feasible preparation process, short time consumption in the preparation process and excellent performance, and can be applied to industrial production by using cheaper materials and simple and convenient preparation flow.

The reflector disclosed by the invention has the characteristics of high reflectivity and adjustable reflection light rotation direction when being heated or powered, and specifically comprises the following components: since the chiral directions of the liquid crystal polymer layer and the small molecule liquid crystal layer are opposite, the reflector can reflect left circularly polarized light and right circularly polarized light at room temperature in a state of no power-up, and the reflector has an effect of super reflection. By regulating and controlling the small-molecule liquid crystal layer, the reflector is heated or an electric field is applied, the small-molecule liquid crystal layer is heated to be in an isotropic state, the small-molecule liquid crystal layer is electrified to be in an orientation zoom cone state, the liquid crystal polymer layer is hardly affected, at the moment, the reflector cannot reflect left-handed circularly polarized light, the reflectivity of the reflector is less than 50%, and no super-reflection effect is achieved. The temperature is reduced to room temperature or the electric field is removed, the small molecule liquid crystal layer returns to the initial state, at the moment, the small molecule liquid crystal layer can reflect left circularly polarized light, the liquid crystal polymer layer reflects right circularly polarized light, the reflectivity of the reflector is more than 90%, and the reflector achieves the super-reflection effect. Wherein, the reflection band of the reflector can be realized by adjusting the type or content of chiral raw materials in the liquid crystal mixture.

The embodiments of the present invention have been described in detail with reference to the accompanying drawings, but the present invention is not limited to the above embodiments, and various changes can be made within the knowledge of one of ordinary skill in the art without departing from the spirit of the present invention. Furthermore, embodiments of the invention and features of the embodiments may be combined with each other without conflict.

Claims

1. The reflector is characterized by comprising a first light-transmitting substrate, a light-adjusting layer and a second light-transmitting substrate in sequence, wherein the light-adjusting layer comprises a liquid crystal polymer layer and a small-molecule liquid crystal layer, the liquid crystal polymer layer and the small-molecule liquid crystal layer are formed by liquid crystal mixture through photopolymerization induction layering, and the chiral rotation directions of the liquid crystal polymer layer and the small-molecule liquid crystal layer are opposite;

The liquid crystal polymer layer comprises a cholesteric liquid crystal polymer network, and the small-molecule liquid crystal layer is cholesteric liquid crystal; the liquid crystal mixture comprises a polymerizable liquid crystal monomer, a non-polymerizable liquid crystal small molecule, a photoinitiator, a polymerizable chiral dopant and a non-polymerizable chiral dopant, wherein the chiralities of the polymerizable chiral dopant and the non-polymerizable chiral dopant are opposite; the liquid crystal polymer layer comprises polymerizable liquid crystal monomers, polymerizable chiral dopants, photoinitiators and non-polymerizable liquid crystal small molecules as raw materials; the raw materials of the small molecule liquid crystal layer comprise non-polymerizable liquid crystal small molecules and non-polymerizable chiral dopants; the mass part ratio of the polymerizable liquid crystal monomer to the photoinitiator is (30-45) (0.1-1); the mass fraction ratio of the polymerizable liquid crystal monomer to the non-polymerizable liquid crystal small molecules is (30-45): 45-60; the ratio of the polymerizable liquid crystal monomer to the polymerizable chiral dopant is (30-45) in parts by mass: (1-9); the ratio of the non-polymerizable liquid crystal small molecules to the non-polymerizable chiral dopants in parts by mass is (45-60): (1-9).

2. The reflector of claim 1, wherein the non-polymerizable liquid crystal small molecules comprise positive liquid crystals.

3. The reflector of claim 2, wherein the liquid crystal mixture comprises polymerizable liquid crystal monomers, positive liquid crystals, photoinitiators, polymerizable chiral dopants, and non-polymerizable chiral dopants.

4. A reflector according to claim 3, wherein the liquid crystal mixture comprises polymerizable liquid crystal monomers, positive liquid crystals, photoinitiators, right-handed polymerizable chiral dopants and left-handed non-polymerizable chiral dopants.

5. The reflector of claim 2, wherein the liquid crystal polymer layer is formed from polymerizable liquid crystal monomers, a right-handed polymerizable chiral dopant, a photoinitiator, and a positive liquid crystal.

6. The reflector of claim 2, wherein the small molecule liquid crystal layer is a left-handed cholesteric liquid crystal layer composed of positive liquid crystals and a left-handed non-polymerizable chiral dopant.

7. The reflector of claim 3, wherein the ratio of the mass fractions of the polymerizable liquid crystal monomer, the positive liquid crystal, the photoinitiator, the polymerizable chiral dopant, and the non-polymerizable chiral dopant is (30-45): 45-60): 0.1-1): 1-9.

8. The reflector of claim 1, wherein the polymerizable liquid crystal monomer comprises an acrylic monomer.

9. The reflector of claim 8, wherein the polymerizable liquid crystal monomer comprises at least one of a monofunctional acrylate or a difunctional acrylate.

10. The reflector of claim 9, wherein the monofunctional acrylate comprises at least one of HCM-020、HCM-021、HCM-022、HCM-039、HCM-040、HCM-042、HCM-043、HCM-044、HCM-045、HCM-046、HCM-047、HCM-048、HCM-049、HCM-050、HCM-059、HCM-062、HCM-065、HCM-066、HCM-074、HCM-075、HCM-076、HCM-078、HCM-079、HCM-080、HCM-083、HCM-091、HCM-108、HCM-109、HCM-110、HCM-116、HCM-126 or HCM-127.

11. The reflector of claim 9, wherein the difunctional acrylate includes at least one of HCM-002, HCM-008, HCM-006, HCM-009, HCM-026, HCM-028, HCM-053, HCM-072, HCM-087, or HCM-125.

12. The reflector of claim 4, wherein the polymerizable chiral dopant in the right-hand sense comprises at least one of HCM-006 or RM 96.

13. The reflector of claim 4, wherein the non-polymerizable chiral dopant that is left-handed comprises at least one of S811, S1011, S5011, or S6N.

14. The reflector of claim 1, wherein the photoinitiator comprises an ultraviolet light initiator.

15. The reflector of claim 1, wherein the photoinitiator comprises at least one of Irgacure-127, irgacure-1173, irgacure-184, irgacure-819, irgacure-651, irgacure-369, or Irgacure-2959.

16. The reflector of claim 2, wherein the positive liquid crystal comprises at least one of 5CB, E7, or HTW 138200-100.

17. The reflector of claim 1, wherein a side of the first transparent substrate facing the liquid crystal mixture is provided with a first parallel alignment layer, and a side of the second transparent substrate facing the liquid crystal mixture is provided with a second parallel alignment layer.

18. The reflector of claim 17, wherein the dimming layer is located between the first parallel alignment layer and the second parallel alignment layer.

19. The reflector of claim 1, wherein the first transparent substrate is a first transparent conductive substrate and the second transparent substrate is a second transparent conductive substrate.

20. The reflector of claim 17, wherein the reflector comprises the first transparent substrate, the first parallel alignment layer, the liquid crystal polymer layer, the small molecule liquid crystal layer, the second parallel alignment layer, and the second transparent substrate stacked in this order.

21. The reflector of claim 19, further comprising a power supply assembly having two poles electrically connected to the first transparent conductive substrate and the second transparent conductive substrate, respectively.

22. A method of making a reflector as claimed in claim 1, comprising the steps of: