Multicolor display structure based on blue-phase liquid crystal elastomer and preparation method of multicolor display structure

Abstract

The invention provides a multi-color display structure based on a blue-phase liquid crystal elastomer and a preparation method of the multi-color display structure, and relates to the technical field of liquid crystal elastomers. A first part area, a second part area and a third part area of a first face of a liquid crystal box are subjected to one-time ultraviolet exposure, two-time ultraviolet exposure and three-time ultraviolet exposure respectively; therefore, the areas corresponding to the first part area, the second part area and the third part area in the display structure respectively have different elastic moduli, after the display structure is subjected to tensile deformation, the deformation amount of the area with the higher elastic modulus is smaller, and the central wavelength variation amount is minimum. Therefore, the areas corresponding to the first part area, the second part area and the third part area in the display structure can display different colors. In conclusion, the display structure manufactured through the method can achieve multi-color display and separation, the manufacturing technology is simple, and the performance is stable.

Description

Technical Field

[0001] The present invention relates to the technical field of liquid crystal elastomers, and in particular, to a multi-color display structure based on blue phase liquid crystal elastomers and a preparation method thereof. Background Art

[0002] Liquid crystal (LC), as an intermediate phase state between liquid and solid, has both the fluidity of liquid crystal and the anisotropy of crystal. The molecular arrangement of liquid crystal materials is very sensitive to external stimuli, and liquid crystal-based sensors show great potential in practical applications. Among them, blue phase liquid crystal (BPLC) has unique optical properties such as narrowband reflection and three-dimensional Bragg reflection, and can achieve higher sensitivity and resolution in complex visual interactions. It exists in the cooling process from the isotropic state to the cholesteric phase, has thermodynamic stability, and is divided into BPIII, BPII, and BPI according to its appearance order. Under the action of strong chirality, liquid crystal molecules are twisted three-dimensionally in space and arranged along the central direction to form a double twisted cylinder (DTC). Since the DTC cannot completely fill the space, the defect lines generated in the gap region further stabilize the three-dimensional cubic crystal structure.

[0003] However, blue phase liquid crystal is thermodynamically unstable, and its existence range is usually limited to within a few degrees Celsius. To address this problem, in recent years, some researchers have stabilized the blue phase by adding nanoparticles or polymer networks. However, the effect of nanoparticles on expanding the blue phase range is still limited, which may be due to the insufficient stability of the defect region caused by the mobility of the particles. Different from nanoparticles, polymer networks are firm and immobile, enabling them to regenerate stable structures repeatedly after annealing in the isotropic phase. The BPI of polymer-stabilized blue phase can remain stable within a temperature range exceeding 60°C. This result is significantly better than the stabilization method achieved by driving with nanoparticles. When the polymer content is increased to 32 wt.%, a peelable gel can be prepared, and the lattice deformation thereof can cause a change in the reflected color. The blue phase gel exhibits good electro-optical response and can manipulate the optical properties by applying strain, further expanding its application fields. However, the blue phase in the blue phase gel is not truly preserved in the polymer network. Therefore, the blue phase gel has limited photon sensitivity to mechanical deformation, and its multi-domain lattice structure results in low color saturation.

[0004] Therefore, the development of blue phase materials with excellent mechanical and optical properties is of great significance for their applications in information anti-counterfeiting / encryption and wearable fields. At present, stretchable blue phase liquid crystal elastomers (BPLCE) have been developed, showing a maximum deformation ability of 74%, significantly improving the mechanical and optical properties of the materials, and at the same time having advantages such as good flexibility and high-saturation structural colors. This provides an effective path to solve the limitations of current flexible sensor devices. The sensitive force-induced color change ability and multi-dimensional light interaction characteristics of BPLCE enable it to exhibit excellent performance in optical sensing. These characteristics make BPLCE provide new technical solutions for the fields of information anti-counterfeiting / encryption and intelligent wearable devices. However, in related technologies, the color display structure based on blue phase liquid crystal elastomers generally can only display a single color and is difficult to meet the requirements of multi-color display. Summary of the Invention

[0005] The problem to be solved by the present invention is: how to obtain a multi-color display structure based on blue phase liquid crystal elastomers.

[0006] To solve the above problems, the present invention provides a preparation method for a multi-color display structure based on blue phase liquid crystal elastomers, including:

[0007] Step S1: Mix liquid crystal monomers, chiral agents, chain extenders, and photoinitiators evenly and then heat to isotropic to obtain a blue phase liquid crystal prepolymer;

[0008] Step S2: Inject the blue phase liquid crystal prepolymer into a liquid crystal cell; wherein, the liquid crystal cell includes a first substrate and a second substrate arranged in a stacked manner, and the blue phase liquid crystal prepolymer is filled between the first substrate and the second substrate;

[0009] Step S3: Perform a first ultraviolet exposure on the first surface of the first substrate; the first surface includes a first partial area, a second partial area, and a third partial area; wherein, the first surface is the surface of the first substrate away from the blue phase liquid crystal prepolymer;

[0010] Step S4: Use a first mask to cover the first partial area and the second partial area, and perform a second ultraviolet exposure on the exposed part of the first surface;

[0011] Step S5: Remove the first mask, use a second mask to cover the first partial area, perform a third ultraviolet exposure on the exposed part of the first surface, and remove the second mask; to obtain a multi-color display structure.

[0012] Optionally, in step S3, the area ratio of the first partial area, the second partial area, and the third partial area is 1:1:1.

[0013] Optionally, the time of the first ultraviolet exposure is 0.9 s to 1.1 s, the time of the second ultraviolet exposure is 3.5 s to 4.5 s, and the time of the third ultraviolet exposure is 2.5 s to 3.5 s.

[0014] Optionally, in the step S1, the mass ratio of the liquid crystal monomer, the chiral agent, the chain extender, and the photoinitiator is (88 to 89):(3.8 to 4.2):(5.8 to 6.2):(0.8 to 1.2).

[0015] Optionally, in the step S1, the liquid crystal monomer includes liquid crystal monomer RM006 and 4-[(6-acryloyloxy)hexyloxy]-4'-cyanobiphenyl.

[0016] Optionally, the mass ratio of the liquid crystal monomer RM006 to the 4-[(6-acryloyloxy)hexyloxy]-4'-cyanobiphenyl is (44.4 to 44.6):(44.4 to 44.6).

[0017] Optionally, in the step S1, the chiral agent is LC756.

[0018] Optionally, in the step S1, the chain extender is HDDA.

[0019] Optionally, in the step S1, the photoinitiator is I-651.

[0020] The present invention also provides a multicolor display structure based on a blue phase liquid crystal elastomer, which is made by using the preparation method of the multicolor display structure based on the blue phase liquid crystal elastomer as described above.

[0021] Compared with the related art, in the present invention, the first partial region, the second partial region, and the third partial region of the first surface of the liquid crystal cell are respectively subjected to one-time ultraviolet exposure, two-time ultraviolet exposure, and three-time ultraviolet exposure, so that the liquid crystal elastomers generated after ultraviolet exposure of the blue phase liquid crystal prepolymers corresponding to the first partial region, the second partial region, and the third partial region have different crosslinking densities. Therefore, the regions corresponding to the first partial region, the second partial region, and the third partial region in the display structure have different elastic moduli. Specifically, the elastic moduli of the regions corresponding to the first partial region (low modulus), the second partial region (medium modulus), and the third partial region (high modulus) in the display structure increase in sequence. After the display structure is subjected to tensile deformation, the region with a higher elastic modulus has a smaller deformation amount and the smallest change amount of the central wavelength. Therefore, the regions corresponding to the first partial region, the second partial region, and the third partial region in the display structure can display different colors. In summary, the display structure prepared by using the method of the present invention can achieve multicolor display and separation, and has a relatively simple preparation process and stable performance. Brief Description of the Drawings

[0022] Figure 1 It is a schematic process diagram of the preparation method of the multi-color display structure based on blue-phase liquid crystal elastomer in the embodiment of the present invention;

[0023] Figure 2 It is a schematic diagram of the color change of the multi-color display structure based on blue-phase liquid crystal elastomer before and after tensile deformation in the embodiment of the present invention;

[0024] Figure 3 It is a diagram showing the change of the central wavelength with the increase of the tensile deformation rate in the region corresponding to the first part of the display structure obtained in Example 1;

[0025] Figure 4 It is a diagram showing the change of the central wavelength with the increase of the tensile deformation rate in the region corresponding to the second part of the display structure obtained in Example 1;

[0026] Figure 5 It is a diagram showing the change of the central wavelength with the increase of the tensile deformation rate in the region corresponding to the third part of the display structure obtained in Example 1;

[0027] Figure 6 It is a physical diagram of the display structure during uniaxial tensile deformation of the display structure obtained in Example 1. Detailed Description of the Embodiments

[0028] To make the above objects, features, and advantages of the present invention more obvious and understandable, the following detailed description of the specific embodiments of the present invention will be given with reference to the accompanying drawings. Although some embodiments of the present invention are shown in the drawings, it should be understood that the present invention can be implemented in various forms and should not be construed as limited to the embodiments described herein. On the contrary, these embodiments are provided to more thoroughly and completely understand the present invention. It should be understood that the drawings and embodiments of the present invention are only for exemplary purposes and are not used to limit the protection scope of the present invention.

[0029] Unless otherwise defined, all technical and scientific terms used in the present invention have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs. The terms used in the present invention in the specification are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0030] As used herein, the term "comprising" and its variations are open-ended, i.e., "including but not limited to"; the term "based on" means "at least partially based on"; the term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one additional embodiment"; the term "some embodiments" means "at least some embodiments"; the term "optionally" means "optional embodiment". The relevant definitions of other terms will be given in the following description. It should be noted that the concepts of "first", "second", etc. mentioned in the present invention are used to distinguish different objects, rather than to describe a specific order or primary-secondary relationship. In addition, the terms "first" and "second" are only used for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise specified, the meaning of "a plurality" is two or more.

[0031] In view of the problems existing in the above related technologies, this embodiment provides a preparation method for a multicolor display structure based on a blue phase liquid crystal elastomer, including:

[0032] Step S1: After uniformly mixing a liquid crystal monomer, a chiral agent, a chain extender, and a photoinitiator, heat to isotropic to obtain a blue phase liquid crystal prepolymer;

[0033] Step S2: As Figure 1 shown, inject the blue phase liquid crystal prepolymer into a liquid crystal cell; wherein, the liquid crystal cell includes a first substrate and a second substrate which are stacked relatively, and the blue phase liquid crystal prepolymer is filled between the first substrate and the second substrate;

[0034] Step S3: As Figure 1 shown, perform a first ultraviolet exposure on the first surface of the first substrate; the first surface includes a first partial area, a second partial area, and a third partial area; wherein, the first surface is the surface of the first substrate away from the blue phase liquid crystal prepolymer;

[0035] Step S4: As Figure 1 shown, cover the first partial area and the second partial area with a first mask, and perform a second ultraviolet exposure on the exposed part of the first surface;

[0036] Step S5: As Figure 1 shown, remove the first mask, cover the first partial area with a second mask, perform a third ultraviolet exposure on the exposed part of the first surface, and remove the second mask to obtain a multicolor display structure.

[0037] In the embodiments of the present invention, by performing one-time ultraviolet exposure, two-time ultraviolet exposure, and three-time ultraviolet exposure on the first partial region, the second partial region, and the third partial region of the liquid crystal cell respectively, the liquid crystal elastomers generated after ultraviolet exposure of the blue-phase liquid crystal prepolymers corresponding to the first partial region, the second partial region, and the third partial region have different crosslinking densities, so that the regions corresponding to the first partial region, the second partial region, and the third partial region in the display structure have different elastic moduli. Specifically, the elastic moduli of the regions corresponding to the first partial region (low modulus), the second partial region (medium modulus), and the third partial region (high modulus) in the display structure increase in sequence. After the display structure is stretched and deformed, the region with a higher elastic modulus has a smaller deformation amount and the smallest central wavelength change amount. Therefore, the regions corresponding to the first partial region, the second partial region, and the third partial region in the display structure can display different colors. In summary, the display structure prepared by the method of the embodiments of the present invention can achieve multi-color display and separation, and has a relatively simple preparation process and stable performance.

[0038] In some embodiments of the present invention, in the step S3, the area ratio of the first partial region, the second partial region, and the third partial region is 1:1:1. Exemplarily, as Figure 1 shown, the liquid crystal cell is a cuboid, which includes a first substrate and a second substrate stacked relatively. The lengths of the first substrate and the second substrate are both 25 mm, the widths of the first substrate and the second substrate are both 22 mm, the gap between the first substrate and the second substrate is 25 μm, the first surface is a rectangle, and the first surface is composed of a first partial region, a second partial region, and a third partial region. The first partial region, the second partial region, and the third partial region are all rectangles, and the first partial region, the second partial region, and the third partial region can be regarded as trisecting the first surface along its width direction.

[0039] In some embodiments of the present invention, the time of the first ultraviolet exposure is 0.9 s to 1.1 s, the time of the second ultraviolet exposure is 3.5 s to 4.5 s, and the time of the third ultraviolet exposure is 2.5 s to 3.5 s; the wavelength of the ultraviolet light used in the first ultraviolet exposure, the second ultraviolet exposure, and the third ultraviolet exposure is 365 nm, and the intensity is 800 mW / cm 2 to 1000 mW / cm 2 .

[0040] Considering that the reflection wavelength of the prepared display structure blue-shifts as the stretching deformation amount increases, it is necessary to preferentially prepare an initial reflection color of red to ensure a wider color gamut coverage after stretching the display structure. Therefore, in some embodiments of the present invention, in the step S1, the mass ratio of the liquid crystal monomer, the chiral agent, the chain extender, and the photoinitiator is (88 to 89):(3.8 to 4.2):(5.8 to 6.2):(0.8 to 1.2); the liquid crystal monomer includes liquid crystal monomer RM006 and liquid crystal monomer CR-3; the mass ratio of the liquid crystal monomer RM006 and the liquid crystal monomer CR-3 is (44.4 to 44.6):(44.4 to 44.6); the chiral agent is LC756, the chain extender is HDDA, and the photoinitiator is I-651. It should be noted that the liquid crystal monomer CR-3 is 4-[(6-acryloyloxy)hexyloxy]-4'-cyanobiphenyl.

[0041] An embodiment of the present invention also provides a multicolor display structure based on a blue-phase liquid crystal elastomer, which is made by using the preparation method of the multicolor display structure based on a blue-phase liquid crystal elastomer as described above.

[0042] The present invention will be further described below with reference to specific embodiments.

[0043] Example 1

[0044] A1. By weight, 44.5 parts of liquid crystal monomer RM006, 44.5 parts of liquid crystal monomer CR-3, 4 parts of chiral agent LC756, 6 parts of chain extender HDDA, and 1 part of photoinitiator I-651 are mixed evenly and then heated to isotropic (temperature is 28 °C) to obtain a blue-phase liquid crystal prepolymer;

[0045] A2. Inject the blue-phase liquid crystal prepolymer into the liquid crystal cell; wherein, the liquid crystal cell includes a first substrate and a second substrate arranged in a stacked manner, and the blue-phase liquid crystal prepolymer is filled between the first substrate and the second substrate; the liquid crystal cell is a cuboid, which includes a first substrate and a second substrate arranged in a stacked manner, the lengths of the first substrate and the second substrate are both 25 mm, the widths are both 22 mm, and the gap between the first substrate and the second substrate is 25 μm.

[0046] A3. As Figure 1As shown, the first surface of the first substrate is subjected to the first ultraviolet exposure; the first surface includes a first partial region, a second partial region, and a third partial region; wherein, the first surface is the surface of the first substrate away from the blue phase liquid crystal prepolymer, the first surface is rectangular, the first surface is composed of the first partial region, the second partial region, and the third partial region, the first partial region, the second partial region, and the third partial region are all rectangular, and the first partial region, the second partial region, and the third partial region can be regarded as trisecting the first surface along its width direction. The time of the first ultraviolet exposure is 1 s. During this process, the first partial region, the second partial region, and the third partial region are all subjected to the first ultraviolet exposure.

[0047] A4. As Figure 1 As shown, the first mask plate is used to cover the first partial region and the second partial region, and the exposed part (the third partial region) of the first surface is subjected to the second ultraviolet exposure; the time of the second ultraviolet exposure is 4 s. During this process, the third partial region is subjected to the second ultraviolet exposure again.

[0048] A5. As Figure 1 As shown, the first mask plate is removed, the second mask plate is used to cover the first partial region, and the exposed part (the second partial region and the third partial region) of the first surface is subjected to the third ultraviolet exposure. After removing the second mask plate, a multicolor display structure is obtained; the time of the third ultraviolet exposure is 3 s. During this process, the second partial region and the third partial region are subjected to the second ultraviolet exposure again.

[0049] It can be seen from the above steps that the total time of ultraviolet exposure of the first partial region is 1 s, the total time of ultraviolet exposure of the second partial region is 4 s, and the total time of ultraviolet exposure of the third partial region is 8 s.

[0050] Experimental Example

[0051] The elastic moduli of the regions corresponding to the first partial region, the second partial region, and the third partial region in the display structure prepared in Example 1 are detected respectively. After detection, as Figure 2 shown, the minimum elastic modulus E3 of the region corresponding to the first partial region in the display structure is 6.16 MPa, the elastic modulus E2 of the region corresponding to the second partial region in the display structure is 102.05 MPa, and the elastic modulus E1 of the region corresponding to the third partial region in the display structure is 276.98 MPa. As Figure 2 shown, when the display structure prepared in Example 1 is subjected to uniaxial tensile deformation as shown by the arrow direction, the regions corresponding to the first partial region, the second partial region, and the third partial region in the display structure can display different colors. It should be noted that Figure 2The figure corresponding to the right side of F0 in the figure is the state diagram before the display structure is stretched and deformed. Figure 2 The figure corresponding to the right side of F1 in the figure is the state diagram when the stretching deformation amount of the display structure is F1. Figure 2 The figure corresponding to the right side of F2 in the figure is the state diagram when the stretching deformation amount of the display structure is F2.

[0052] When the display structure prepared in Example 1 is subjected to uniaxial stretching deformation in the manner shown by the arrow, the change in the central wavelength of the regions corresponding to the first part region, the second part region, and the third part region in the display structure is as follows Figures 3 to 5 shown. From Figures 3 to 5 it can be seen that as the deformation amount of the display structure increases, the central wavelength of the region corresponding to the first part region in the display structure changes from 642 nm to 521 nm, the central wavelength of the region corresponding to the second part region in the display structure changes from 641 nm to 543 nm, and the central wavelength of the region corresponding to the third part region in the display structure changes from 640 nm to 561 nm; it can be seen that before the stretching deformation, the colors of the regions corresponding to the first part region, the second part region, and the third part region in the display structure are uniform; under the same stretching deformation amount, the degree of color change of the regions corresponding to the first part region, the second part region, and the third part region in the display structure increases in turn, so the regions corresponding to the first part region, the second part region, and the third part region in the display structure can display different colors. Figure 6 The figure is a physical diagram of the display structure when the display structure prepared in Example 1 is subjected to uniaxial stretching deformation. Figure 6 In (a) is the physical diagram of the display structure before stretching deformation. Figure 6 In (b) is the physical diagram of the display structure with a stretching deformation rate of 12%. Figure 6 In (c) is the physical diagram of the display structure with a stretching deformation rate of 30%. From Figure 6 it can be seen that as the deformation amount increases, the display structure gradually changes from a single color display (red) to three color displays (red, yellow, green). It should be noted that Figures 3 to 5 in the series 0 represents the curve corresponding to the stretching deformation rate of 0 of the display structure, and so on. For example, 15% represents the curve corresponding to the stretching deformation rate of 15% of the display structure, and 20% represents the curve corresponding to the stretching deformation rate of 20% of the display structure.

[0053] Although the present invention is disclosed as above, the protection scope of the present invention is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention, and these changes and modifications will all fall within the protection scope of the present invention.

Claims

1. A preparation method of a multicolor display structure based on blue phase liquid crystal elastomer, characterized in that, Including: Step S1: After uniformly mixing a liquid crystal monomer, a chiral agent, a chain extender, and a photoinitiator, heat them to isotropic to obtain a blue phase liquid crystal prepolymer. Step S2: Inject the blue phase liquid crystal prepolymer into a liquid crystal cell; wherein, the liquid crystal cell includes a first substrate and a second substrate stacked relatively, and the blue phase liquid crystal prepolymer is filled between the first substrate and the second substrate. Step S3: Perform a first ultraviolet exposure on the first surface of the first substrate; the first surface includes a first partial region, a second partial region, and a third partial region; wherein, the first surface is the surface of the first substrate away from the blue phase liquid crystal prepolymer. Step S4: Use a first mask to cover the first partial region and the second partial region, and perform a second ultraviolet exposure on the exposed part of the first surface. Step S5: Remove the first mask, use a second mask to cover the first partial region, perform a third ultraviolet exposure on the exposed part of the first surface, and remove the second mask to obtain a multicolor display structure.

2. The preparation method of the multicolor display structure based on blue phase liquid crystal elastomer according to claim 1, wherein In the step S3, the area ratio of the first partial region, the second partial region, and the third partial region is 1:1:

1.

3. The preparation method of the multicolor display structure based on blue phase liquid crystal elastomer according to claim 1, wherein The time of the first ultraviolet exposure is 0.9 s to 1.1 s, the time of the second ultraviolet exposure is 3.5 s to 4.5 s, and the time of the third ultraviolet exposure is 2.5 s to 3.5 s.

4. The preparation method of the multi-color display structure based on blue phase liquid crystal elastomer according to claim 1, wherein, In the step S1, the mass ratio of the liquid crystal monomer, the chiral agent, the chain extender, and the photoinitiator is (88 to 89):(3.8 to 4.2):(5.8 to 6.2):(0.8 to 1.2).

5. The preparation method of the multicolor display structure based on blue phase liquid crystal elastomer according to claim 1, characterized in that In the step S1, the liquid crystal monomer includes liquid crystal monomer RM006 and 4-[(6-acryloyloxy)hexyloxy]-4'-cyanobiphenyl.

6. The preparation method of the multicolor display structure based on blue phase liquid crystal elastomer according to claim 5, wherein, The mass ratio of the liquid crystal monomer RM006 and 4-[(6-acryloyloxy)hexyloxy]-4'-cyanobiphenyl is (44.4 to 44.6):(44.4 to 44.6).

7. The preparation method of the multicolor display structure based on blue phase liquid crystal elastomer according to claim 1, characterized in that, In the step S1, the chiral agent is LC756.

8. The preparation method of the multicolor display structure based on blue phase liquid crystal elastomer according to claim 1, characterized in that, In the step S1, the chain extender is HDDA.

9. The preparation method of the multicolor display structure based on blue phase liquid crystal elastomer according to claim 1, wherein, In the step S1, the photoinitiator is I-651.

10. A multicolor display structure based on a blue phase liquid crystal elastomer, characterized in that, It is made by using the preparation method of the multicolor display structure based on blue phase liquid crystal elastomer according to any one of claims 1 to 9.

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