Double-chiral blue-phase liquid crystal photon paper as well as preparation method and application thereof

Abstract

The invention discloses double-chiral blue-phase liquid crystal photon paper as well as a preparation method and application thereof. The photon paper structurally comprises a first substrate, a first blue phase liquid crystal polymer template and a second blue phase liquid crystal polymer template, wherein the first blue phase liquid crystal polymer template and the second blue phase liquid crystal polymer template are sequentially arranged on the first substrate from bottom to top; wherein the first blue-phase liquid crystal polymer template and the second blue-phase liquid crystal polymer template have opposite chirality. Patterns written or printed on the photon paper can reflect left-handed light and right-handed light at the same time, the light in different rotation directions contains different color information and color change rates, and the polarization anti-counterfeiting and information encryption effects are achieved.

Description

Technical Field

[0001] This invention relates to the field of blue phase liquid crystals. More specifically, it relates to a bipolar blue phase liquid crystal photonic paper, its preparation method, and its applications. Background Technology

[0002] Liquid crystals, possessing both the fluidity of fluids and the anisotropy of solids, exhibit excellent responsiveness and are widely used in optical display devices. The blue phase is one phase of liquid crystals, formed by the self-assembly of liquid crystal molecules and chiral molecules into a cubic lattice structure with a lattice constant of several hundred nanometers. It selectively reflects a specific wavelength in the visible light band, thus displaying bright colors with high saturation and high reflectivity. Its self-assembled structure generally exhibits only one type of chirality: left-handed blue phase liquid crystals reflect left-handed circularly polarized light and transmit right-handed circularly polarized light; right-handed blue phase liquid crystals reflect right-handed circularly polarized light and transmit left-handed circularly polarized light. Blue phase liquid crystals have a narrow temperature range (0.5–2°C), and polymerizable monomers are typically added to broaden the temperature range and solidify the structure, resulting in polymer-stabilized blue phases.

[0003] Blue phase liquid crystal polymer template technology uses organic solvents to wash away unpolymerized components from a cured polymer-stabilized blue phase liquid crystal film, yielding a writable and printable polymer template. The polymer template possesses the same chirality as the unwashed blue phase liquid crystal. This technology allows for the creation of rewritable photonic paper. Compared to photonic paper made of other materials, blue phase liquid crystal photonic paper offers advantages such as circular polarization reflection, high-precision patterning, and high color saturation. Patterns are drawn on the photonic paper using nematic liquid crystal as ink. The ink swells through the template, increasing the interplanar spacing of Bragg reflection and achieving a redshift; diffusion within the template reduces the degree of swelling, achieving a blueshift. This results in a "live" pattern effect where the color changes over time, providing dynamic anti-counterfeiting functionality.

[0004] However, currently used blue phase liquid crystal polymer templates only possess single chirality, and the color information expressed by writing is homogeneous in the direction of reflected light rotation, exhibiting relatively limited information in the chiral dimension. Although liquid crystal devices with both left and right chirality have been developed for blue phase liquid crystals, these devices are limited by the closed system composed of a substrate, and cannot achieve the effect of blue phase liquid crystal polymer network photonic paper that can freely write and print patterns and simultaneously reflect left-handed and right-handed light information. Summary of the Invention

[0005] To address the limitations of printable blue phase liquid crystal photonic paper in terms of its single chirality and limited anti-counterfeiting effect, this invention provides bipolar blue phase liquid crystal photonic paper, its preparation method, and its applications. Patterns written or printed on this photonic paper can simultaneously reflect left-handed and right-handed light, and light with different chiral directions contains different color information and color change rates, thus achieving both circular polarization anti-counterfeiting and information encryption effects.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] On one hand, the present invention provides a bidirectional blue phase liquid crystal photonic paper, the structure of which includes:

[0008] First substrate, and

[0009] A first blue phase liquid crystal polymer template and a second blue phase liquid crystal polymer template are sequentially disposed on the first substrate from bottom to top;

[0010] The first blue phase liquid crystal polymer template and the second blue phase liquid crystal polymer template have opposite chirality.

[0011] Furthermore, the first blue phase liquid crystal polymer template reflects left-handed light, and the second blue phase liquid crystal polymer template reflects right-handed light, or...

[0012] The first blue phase liquid crystal polymer template reflects right-handed light, and the second blue phase liquid crystal polymer template reflects left-handed light.

[0013] Furthermore, the first blue phase liquid crystal polymer template and the second blue phase liquid crystal polymer template are blue phase liquid crystal polymer films with opposite chirality and containing nanoscale pores.

[0014] Furthermore, the structure of the photonic paper also includes an anchoring layer disposed on the first substrate between the first substrate and the first blue phase liquid crystal polymer template.

[0015] Furthermore, the anchoring layer is a layer structure obtained by spin-coating a 3-(methacryloyloxy)propyltrimethoxysilane solution onto the first substrate and then drying and curing it.

[0016] Furthermore, the first substrate is one of a glass plate, a quartz plate, or an ITO plate.

[0017] In another aspect, the present invention provides a method for preparing the biphasic blue phase liquid crystal photonic paper as described above, the method comprising the following steps:

[0018] An anchoring layer is formed on the surface of the first substrate;

[0019] A first liquid crystal cell is provided, wherein the first liquid crystal cell comprises a first substrate having an anchoring layer formed on its surface, a third substrate disposed opposite to the first substrate, and a second spacer disposed between the first substrate and the third substrate to form a closed space together with the first substrate and the third substrate.

[0020] A first liquid crystal mixture is added to the first liquid crystal cell, cooled to the blue phase, and cured by ultraviolet light to obtain a third blue phase liquid crystal polymer film. The film is then eluted with an organic solvent to obtain a third blue phase liquid crystal polymer template containing nanoscale pores.

[0021] A second liquid crystal cell is provided, wherein the second liquid crystal cell comprises a third blue phase liquid crystal polymer template, a second substrate disposed opposite to the third blue phase liquid crystal polymer template, and a first spacer disposed between the third blue phase liquid crystal polymer template and the second substrate, which together form an enclosed space with the third blue phase liquid crystal polymer template and the second substrate.

[0022] A second liquid crystal mixture with a chiral agent having the opposite rotation to the first liquid crystal mixture is added to the second liquid crystal cell. Part of the second liquid crystal mixture penetrates into the pores of the third blue phase liquid crystal polymer film, is cooled to the blue phase, and is cured by ultraviolet light to obtain a bipolar blue phase liquid crystal polymer film. The film is then eluted with an organic solvent to obtain the first blue phase liquid crystal polymer template and the second blue phase liquid crystal polymer template.

[0023] The obtained structure is subjected to surface hydrophobic treatment to obtain the bipolar blue phase liquid crystal photonic paper.

[0024] Furthermore, the thickness of the second spacer is 5–25 μm.

[0025] Furthermore, the thickness of the first spacer is 10–50 μm.

[0026] Furthermore, the thickness ratio of the second spacer to the first spacer is 1:(1.5 to 3.5).

[0027] Furthermore, the thickness ratio of the second spacer to the first spacer is 1:(2-3).

[0028] Furthermore, the bidirectional blue phase liquid crystal polymer film is composed of a first blue phase liquid crystal polymer film and a second blue phase liquid crystal polymer film tightly connected together.

[0029] Furthermore, the organic solvent is selected from N,N-dimethylformamide, acetone, and ethyl acetate.

[0030] Furthermore, the method also includes the step of eluting with an organic solvent and then drying at 25–35°C for 4–6 hours.

[0031] Furthermore, the anchoring layer is a structure obtained by spin-coating a 1 vol% 3-(methacryloyloxy)propyltrimethoxysilane solution on the surface of the first substrate at a rotation speed of 2300-2500 rpm for 30 seconds and curing it at 100°C for 1 hour; the anchoring layer firmly anchors the blue phase liquid crystal polymer film onto the first substrate and will not be washed off by subsequent organic solvents.

[0032] In another aspect, the present invention provides the application of the bipolar blue phase liquid crystal photonic paper described above in circularly polarized anti-counterfeiting.

[0033] Furthermore, the application includes the following steps:

[0034] Anti-counterfeiting patterns are inkjet printed on the bipolar blue phase liquid crystal photonic paper;

[0035] Heat the sample and observe the printed pattern using both left-handed and right-handed circular polarizers.

[0036] Furthermore, the heating temperature is 35–50°C.

[0037] Furthermore, in the inkjet printing, the printing ink composition is one of 5CB, 6CB, or 8CB.

[0038] In the aforementioned application, when the printed pattern is observed using a left-handed and a right-handed circular polarizer alone, patterns with different colors can be observed, and the colors change as the heating time increases. This effect can be applied to dynamic circular polarization anti-counterfeiting.

[0039] The beneficial effects of this invention are as follows:

[0040] The bipolar blue phase liquid crystal photonic paper provided by this invention is a whole formed by tightly connecting two layers of blue phase liquid crystal polymer templates with different chiralities, and can be used in an open system. Colored patterns can be freely written or printed using a single ink. The patterns can simultaneously reflect left-handed and right-handed light, and the wavelengths of the reflected light show independent wavelength changes with heating time, covering the entire visible light band. Using different circular polarizers as decryption cards, different color information can be read. The technical solution of this invention adds a chiral dimension to the information encryption of blue phase liquid crystal photonic paper, increasing information density, and it is rewritable and recyclable, making it a reusable paper material. Furthermore, based on the different heating times and colors displayed by different chiral templates in the patterned areas, the photonic paper can also be applied to fields such as circular polarization anti-counterfeiting. Attached Figure Description

[0041] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0042] Figure 1 A cross-sectional schematic diagram of the biphasic blue phase liquid crystal polymer template described in the implementation method is shown.

[0043] Figure 2 This diagram illustrates a process flow chart of a biphasic blue phase liquid crystal photonic paper preparation method as described in the implementation method.

[0044] Figure 3A cross-sectional schematic diagram of the first liquid crystal cell in the implementation method is shown.

[0045] Figure 4 A cross-sectional schematic diagram of the first liquid crystal cell unit in the implementation method is shown.

[0046] Figure 5 A cross-sectional schematic diagram of the monochiral blue phase liquid crystal polymer template described in the implementation method is shown.

[0047] Figure 6 A cross-sectional schematic diagram of the second liquid crystal cell in the implementation method is shown.

[0048] Figure 7 A cross-sectional schematic diagram of the second liquid crystal cell unit in the implementation method is shown.

[0049] Figure 8 Photographs of the biphasic blue phase liquid crystal polymer film obtained in Example 1 and cross-polarized reflectance photographs are shown.

[0050] Figure 9 The reflectance spectra of the biphasic blue phase liquid crystal polymer film obtained in Example 1 before and after washing are shown.

[0051] Figure 10 The photographs show physical images and cross-polarized reflection images of the biphasic blue phase liquid crystal photonic paper obtained in Example 1.

[0052] Figure 11 The diagram shows the changes in the left-hand and right-hand rotational reflected light spectra of the biphasic blue phase liquid crystal photonic paper printed pattern obtained in Example 1 as a function of heating time.

[0053] Figure 12 The image shows an orthogonally polarized reflection photograph of a pattern printed on biphasic blue phase liquid crystal photonic paper obtained in Example 1 after heating for a period of time.

[0054] Figure 13 The photographs show physical images and cross-polarized reflection images of the biphasic blue phase liquid crystal photonic paper obtained in Example 2.

[0055] Figure 14 The left-hand and right-hand rotational reflection spectra of the biphasic blue phase liquid crystal photonic paper printing pattern obtained in Example 2 are shown.

[0056] Figure 15 The photographs show physical images and cross-polarized reflection images of the biphasic blue phase liquid crystal photonic paper obtained in Example 3.

[0057] Figure 16 The left-hand and right-hand rotational reflection spectra of the biphasic blue phase liquid crystal photonic paper printing pattern obtained in Example 3 are shown. Detailed Implementation

[0058] To more clearly illustrate the present invention, the following description, in conjunction with preferred embodiments and accompanying drawings, further explains the invention. Similar components in the drawings are indicated by the same reference numerals. Those skilled in the art should understand that the specific description below is illustrative rather than restrictive and should not be construed as limiting the scope of protection of the present invention.

[0059] Implementation Methods

[0060] The following is for reference Figures 1 to 7 The preparation method of bipolar blue phase liquid crystal photonic paper is described.

[0061] The bipolar blue phase liquid crystal photonic paper of this invention is a bipolar blue phase liquid crystal polymer template with a hydrophobic surface treatment. A cross-sectional schematic diagram of the bipolar blue phase liquid crystal photonic paper is shown below. Figure 1 As shown, it includes, in sequence, a first substrate 11, an anchoring layer 21, a first blue phase liquid crystal polymer template 51, and a second blue phase liquid crystal polymer template 52.

[0062] In some examples, the first blue phase liquid crystal polymer template 51 reflects left-handed light, and the second blue phase liquid crystal polymer template 52 reflects right-handed light, or

[0063] The first blue phase liquid crystal polymer template 51 reflects right-handed light, and the second blue phase liquid crystal polymer template 52 reflects left-handed light.

[0064] In some examples, the first blue phase liquid crystal polymer template 51 and the second blue phase liquid crystal polymer template 52 are blue phase liquid crystal polymer films with nanoscale pores and opposite chirality.

[0065] In some examples, the anchoring layer 21 is a layer structure obtained by spin-coating a 3-(methacryloyloxy)propyltrimethoxysilane solution onto the first substrate 11 and then drying and curing it.

[0066] In some examples, the first substrate is one of a glass plate, a quartz plate, or an ITO plate.

[0067] In some embodiments, a schematic flowchart of the preparation method of the bipolar blue phase liquid crystal photonic paper of the present invention is shown below. Figure 2 shown. Specifically:

[0068] (1) Step S102: Assemble the first liquid crystal cell and prepare a single-chiral blue phase liquid crystal polymer film that reflects left-handed light.

[0069] A first substrate 11 and a third substrate 13 are provided. The first substrate 11 includes, but is not limited to, any one of a quartz substrate, a common glass substrate, and an ITO substrate.

[0070] The first substrate 11 was cleaned sequentially with soapy water, ethanol, and isopropanol for 30 minutes to obtain a clean first substrate 11. A 1 vol% solution of tri-(methacryloyloxy)propyltrimethoxysilane was prepared and spin-coated onto the surface of the first substrate 11 at a speed of 2300-2500 rpm for 30 seconds. The solution was then cured at 80-100°C for 1 hour to form an anchoring layer 21 on the first substrate 11. The function of the anchoring layer 21 is to firmly anchor the blue phase liquid crystal polymer film onto the first substrate 11, preventing it from being washed off by subsequent organic solvents.

[0071] The third substrate 13 was cleaned sequentially with soapy water, ethanol, and isopropanol for 30 minutes to obtain a clean third substrate 13. A 3 wt% polyvinyl alcohol solution was prepared and spin-coated onto the surface of the third substrate 13 at a speed of 2300-2500 rpm for 30 seconds. After curing at 80-100°C for 1 hour, the substrate was rubbed parallel to the surface with non-woven fabric 10-15 times to form a second parallel alignment layer 23 on the third substrate 13. The function of the second parallel alignment layer 23 is to induce and unify the alignment of liquid crystal molecules, enabling the blue phase liquid crystal to assemble into large-area single domains.

[0072] like Figure 3 As shown, a first liquid crystal cell 101 is formed by using a first substrate 11, an anchoring layer 21, a second spacer 32, a second parallel alignment layer 23, and a third substrate 13, and is sealed with adhesive.

[0073] The second spacer 32 includes, but is not limited to, any one of polyester film and polystyrene microspheres, and the thickness of the second spacer 32 is 5 to 25 μm.

[0074] Weigh 20–60 wt% of non-photopolymerizable nematic liquid crystal, 30–70 wt% of photopolymerizable nematic liquid crystal, 2.5–7 wt% of left-handed dopant, 1–3 wt% of crosslinking agent and 0.5–2 wt% of photoinitiator using a balance, add dichloromethane to dissolve and dry to obtain a mixture of left-handed blue phase liquid crystals.

[0075] The left-handed blue phase liquid crystal mixture was injected into the first liquid crystal cell 101 at 80-120°C using capillary force, and then cooled to the blue phase I state at 40 mW / cm². 2 Irradiation with intense ultraviolet light for 80–120 s causes the internal polymerizable liquid crystal components to crosslink and form a polymer network, resulting in a third blue-phase liquid crystal polymer film 43. The third blue-phase liquid crystal polymer film 43 and the first liquid crystal cell constitute a first liquid crystal cell unit, as shown in the schematic cross-sectional diagram below. Figure 4 As shown.

[0076] In some examples, the non-photopolymerizable nematic liquid crystal includes one or more of 5CB and HTG135200; the photopolymerizable nematic liquid crystal includes one or more of RM105, RM257, and C6M; the left-handed dopant is S5011; the crosslinking agent is TMPTA; and the photoinitiator is I-651.

[0077] (2) Step S201: Prepare a single-chiral liquid crystal polymer template that reflects left-handed light using a single-chiral blue phase liquid crystal polymer film.

[0078] The third substrate 13 with the second parallel alignment layer 23 and the second spacer 32 in the first liquid crystal cell unit are peeled off. The remaining portion is immersed in an organic solvent to completely wash away the unpolymerized components, and then dried at 25-35°C for 4-6 hours. The organic solvent used for elution includes, but is not limited to, any one of N,N-dimethylformamide, acetone, and ethyl acetate, and the immersion time varies depending on the type of solvent. After the unpolymerized liquid crystal components are washed away from the third blue phase liquid crystal polymer film 43, it becomes the third blue phase liquid crystal polymer template 53. A chiral blue phase liquid crystal polymer template is composed of the first substrate 11, the anchoring layer 21, and the third blue phase liquid crystal polymer template 53, as shown in the schematic cross-sectional diagram below. Figure 5 As shown.

[0079] Unpolymerized components can be washed away by soaking in organic solvents, forming nanoscale pores on the polymer film.

[0080] (3)S104. A second liquid crystal cell is formed by assembling a single-chiral blue phase liquid crystal polymer template to prepare a bichiral blue phase liquid crystal polymer film that simultaneously reflects left-handed and right-handed light.

[0081] A second substrate 12 is provided. The substrate includes, but is not limited to, any one of a quartz substrate, a common glass substrate, and an ITO substrate.

[0082] The second substrate 12 was cleaned sequentially with soapy water, ethanol, and isopropanol for 30 minutes to obtain a clean second substrate 12. A 3 wt% polyvinyl alcohol solution was prepared and spin-coated onto the surface of the second substrate 12 at a speed of 2300-2500 rpm for 30 seconds. The same spin-coating method was repeated once. After curing at 80-100°C for 1 hour, the substrate was rubbed 10-15 times with a non-woven fabric to form a first parallel alignment layer 22 on the second substrate 12. In order to prepare a single-domain chiral blue phase liquid crystal polymer film, the rubbing scratches in the first parallel alignment layer 22 should be deeper than those in the parallel alignment layer 23, because the lower polymer network induces the alignment of the upper opposite-chiral liquid crystal, which will affect the growth of the upper blue phase liquid crystal single domains.

[0083] Selectively, a 1 vol% solution of tris-(methacryloyloxy)propyltrimethoxysilane can be spin-coated onto the surface of the third blue phase liquid crystal polymer template 53 at a rotation speed of 2300–2500 rpm for 30 seconds, followed by baking in an oven at 80°C for 2 hours. This step enhances the adhesion between the upper and lower blue phase liquid crystal films and improves film uniformity. It should be noted that the biphasic blue phase liquid crystal polymer photonic paper can be successfully prepared without this step.

[0084] like Figure 6 As shown, a second liquid crystal cell is formed using a first substrate 11, an anchoring layer 21, a third blue phase liquid crystal polymer template 53, a first spacer 31, a first parallel alignment layer 22, and a second substrate 12, and is sealed with adhesive. The spacer includes, but is not limited to, any one of polyester film and polystyrene microspheres, and the thickness of the first spacer 31 is 10–50 μm.

[0085] Weigh 20–60 wt% of non-photopolymerizable nematic liquid crystal, 30–70 wt% of photopolymerizable nematic liquid crystal, 2.5–7 wt% of right-handed dopant, 1–3 wt% of crosslinking agent and 0.5–2 wt% of photoinitiator using a balance, dissolve in dichloromethane and dry to obtain a right-handed blue phase liquid crystal mixture.

[0086] In some examples, the non-photopolymerizable nematic liquid crystal includes one or more of 5CB and HTG135200; the photopolymerizable nematic liquid crystal includes one or more of RM105, RM257, and C6M; the chiral dopant is one or more of R5011 and LC756; the crosslinking agent is TMPTA; and the photoinitiator is I-651.

[0087] The right-handed blue phase liquid crystal mixture is injected into the second liquid crystal cell using capillary force at a preferred temperature of 80°C, and held at this temperature for 10 minutes to allow the liquid crystal mixture to fully penetrate into the pores of the lower template (i.e., the third blue phase liquid crystal polymer template 53). Because the right-handed blue phase liquid crystal penetrating into the lower template is induced to align by the left-handedness of the polymer network, a right-handed blue phase will not form after cooling, and the lower blue phase film will retain the left-handedness of its original structure. The upper liquid crystal is cooled to the blue phase I state at a rate of 40 mW / cm². 2Irradiation with intense ultraviolet light for 120–180 s causes the internal polymerizable liquid crystal components to crosslink and form a polymer network. A second blue-phase liquid crystal polymer film 42 is obtained on the upper layer, and a first blue-phase liquid crystal polymer film 41 (composed of a third blue-phase liquid crystal polymer template 53 and a right-handed blue-phase liquid crystal mixture permeating into the template pores) is obtained on the lower layer. The second liquid crystal cell unit is composed of a first substrate 11, an anchoring layer 21, a first spacer 31, the first blue-phase liquid crystal polymer film 41, the second blue-phase liquid crystal polymer film 42, a first parallel alignment layer 22, and a second substrate 12. A cross-sectional schematic diagram is shown below. Figure 7 As shown. (4) Step S202: Prepare a bipolar blue phase liquid crystal polymer template that simultaneously reflects left-handed and right-handed light using a bipolar blue phase liquid crystal polymer film.

[0088] The second substrate 12 with the first parallel alignment layer 22 and the first spacer 31 are peeled off from the second liquid crystal cell unit. The remaining portion is immersed in an organic solvent to completely wash away the unpolymerized components, and then dried at 25-30°C for 4-6 hours. The organic solvent used for elution includes, but is not limited to, any one of acetone and ethyl acetate, and the immersion time varies depending on the type of solvent. After the unpolymerized liquid crystal components are washed away from the second blue phase liquid crystal polymer film 42, it becomes the second blue phase liquid crystal polymer template 52. After the unpolymerized liquid crystal components are washed away from the first blue phase liquid crystal polymer film 41, it becomes the first blue phase liquid crystal polymer template 51. The biphasic blue phase liquid crystal polymer template is composed of the first substrate 11, the anchoring layer 21, the first blue phase liquid crystal polymer template 51, and the second blue phase liquid crystal polymer template 52, as shown in the cross-sectional schematic diagram below. Figure 1 As shown.

[0089] (5) Step S203: Perform hydrophobic treatment on the surface of the bipolar blue phase liquid crystal polymer template.

[0090] The bipolar blue phase liquid crystal polymer template was placed in a vacuum plasma cleaner and treated with an intensity of 180-220W for 500-700 seconds to make its surface hydrophilic.

[0091] Next, the bisexual blue phase liquid crystal polymer template was placed in a glass vacuum desiccator with fluorosilane added and evacuated for 30 minutes.

[0092] The fluorosilanes include, but are not limited to, one or more of 1H,1H,2H,2H-perfluorooctyltrimethoxysilane, 1H,1H,2H,2H-perfluorodecyltrimethoxysilane, or hexadecyltriethoxysilane.

[0093] More preferably, the ratio of the amount of fluorosilane liquid to the surface area of ​​the blue phase liquid crystal polymer template being treated is 0.3–0.4 μL: 1 cm². 2 .

[0094] Place the glass vacuum dryer into an oven and perform vapor deposition treatment at 30-60℃ for 4-8 hours to obtain writable and printable bidirectional blue phase liquid crystal photonic paper.

[0095] It is important to note that the purpose of this hydrophobic treatment step is to increase the contact angle of the nematic ink on the photonic paper, thereby improving the resolution of the printed pattern. Bipolar blue liquid crystal polymer templates prepared without this step can still be used as writable and printable photonic paper, without affecting their circular polarization anti-counterfeiting function (simultaneously reflecting left- and right-handed rotating light) and their dynamic anti-counterfeiting function (the color of left- and right-handed rotating light changes independently).

[0096] The aforementioned nematic liquid crystal inks include, but are not limited to, one or more of 5CB, 6CB, and 8CB.

[0097] In the above-described printing and color development process, those skilled in the art can control the ink penetration rate by changing the volume of a single ink droplet and the heating temperature, thereby altering the color change rate. Preferably, the ink droplet volume is 10 pL and the heating temperature is 40°C.

[0098] The aforementioned bidirectional blue phase liquid crystal photonic paper allows for the removal of ink from patterns after writing or printing on it, by soaking it in an organic solvent without damaging the integrity of the blue phase liquid crystal polymer network structure. This enables the erasure and rewriting / printing of patterns.

[0099] Example

[0100] Unless otherwise stated, all raw materials and reagents used in the following examples are commercially available products or can be prepared by known methods. Where specific techniques or conditions are not specified in the examples, they are performed using conventional methods or in accordance with techniques or conditions described in the literature in this field, or according to the product instructions. Reagents and instruments whose manufacturers are not specified are all conventional products that can be purchased from legitimate channels.

[0101] Example 1

[0102] Reference Figures 1 to 7 The method described herein is for preparing the biphasic blue phase liquid crystal photonic paper of Example 1. The parameters used in each preparation step are shown below.

[0103] (1) Preparation of a single-chiral blue phase liquid crystal polymer film.

[0104] The first substrate 11 is a common glass sheet, on which a 1 vol% tri-(methacryloyloxy)propyltrimethoxysilane solution is spin-coated at a speed of 2400 rpm and cured at a temperature of 100°C.

[0105] The third substrate 13 is a common glass sheet, on which a 3 wt% polyvinyl alcohol solution is spin-coated at a speed of 2400 rpm and a curing temperature of 100℃.

[0106] The second spacer 32 is a PET film with a thickness of 12.5 μm;

[0107] The formulation of the left-handed blue phase liquid crystal mixture is as follows: 56.4 wt% non-polymerizable nematic commercial mixed liquid crystal monomer HTG135200, 28.8 wt% single double-bond polymerizable monomer RM105, 9.6 wt% two double-bond polymerizable monomer RM257, 3.1 wt% left-handed dopant S5011, 1.6 wt% crosslinking agent TMPTA and 0.5 wt% photoinitiator I-651;

[0108] The temperature at which the left-handed blue phase liquid crystal mixture is poured into the liquid crystal cell is 120°C, and the ultraviolet light polymerization time after the formation of blue phase single domains is 90s.

[0109] (2) Preparation of a single-chiral blue phase liquid crystal polymer template.

[0110] The eluting organic solvent was N,N-dimethylformamide, the soaking time was 10 min, the drying temperature was 25℃, and the drying time was 5 h.

[0111] (3) Preparation of bidirectional blue phase liquid crystal polymer film.

[0112] The second substrate 12 is a common glass sheet, on which a 3 wt% polyvinyl alcohol solution is spin-coated at a speed of 2400 rpm and cured at a temperature of 100°C.

[0113] The first spacer 31 is a PET film with a thickness of 37.5 μm;

[0114] Select the surface of the third blue phase liquid crystal polymer template 53 and spin-coat a 1 vol% tri-(methacryloyloxy)propyltrimethoxysilane solution at a speed of 2400 rpm for 30 s, then place it in an oven at 80 ℃ for 2 h.

[0115] The formulation of the right-handed blue phase liquid crystal mixture is as follows: 33.4 wt% non-polymerizable nematic commercial mixed liquid crystal monomer HTG135200, 44.3 wt% single double-bond polymerizable monomer RM105, 14.4 wt% double-bond polymerizable monomer RM257, 5 wt% right-handed dopant LC756, 2.4 wt% crosslinking agent TMPTA and 0.5 wt% photoinitiator I-651.

[0116] The UV photopolymerization time after the formation of blue phase single domains is 120s.

[0117] The prepared bisexual blue phase liquid crystal polymer film can simultaneously reflect wavelength photographs and cross-polarized reflectance photographs, such as... Figure 8As shown. In the crossed polarization reflection mode of the polarizing microscope, the incident light is linearly polarized. When a left-handed circular polarizer is inserted into the optical path, green left-handed light reflected from the lower layer of the bipolar blue liquid crystal polymer film (i.e., the first blue liquid crystal polymer film 41) can be observed; when a right-handed circular polarizer is inserted into the optical path, red right-handed light reflected from the upper layer of the bipolar film (i.e., the second blue liquid crystal polymer film 42) can be observed; when no circular polarizer is inserted, the entire bipolar blue liquid crystal polymer film displays a mixed color of green and red, i.e., yellow.

[0118] The reflection spectra of the bipolar blue phase liquid crystal polymer film under linearly polarized light, left-handed light, and right-handed light incident light are as follows: Figure 9 As shown before washing. Under linearly polarized light, it can simultaneously reflect left-handed and right-handed light, displaying different colors corresponding to the structural features of the upper and lower layers.

[0119] (4) Preparation of bidirectional blue phase liquid crystal polymer template.

[0120] Acetone was selected as the elution organic solvent, the soaking time was 4 hours, the drying temperature was 25℃, and the drying time was 6 hours.

[0121] The reflectance spectra of the bisexual blue phase liquid crystal polymer template obtained after washing under linearly polarized light, left-handed light, and right-handed light incident light are as follows: Figure 9 As shown after washing. After washing away the unpolymerized components, the blue phase liquid crystal polymer network collapses, the longitudinal lattice spacing decreases, and the Bragg reflection wavelength shifts blue. It can be seen that the template still retains its bichirality characteristics after washing.

[0122] It is important to note that both bipolar blue liquid crystal polymer films and bipolar blue liquid crystal polymer templates can simultaneously reflect left-handed and right-handed light. The difference lies in the wavelength of the left-handed and right-handed reflected light from the bipolar blue liquid crystal polymer film, which can be used for static circular polarization anti-counterfeiting; while the wavelength of the left-handed and right-handed reflected light from the bipolar blue liquid crystal polymer template can be changed by adjusting the swelling degree of the printing ink, which can be used for dynamic circular polarization anti-counterfeiting.

[0123] (5) Preparation of bidirectional blue phase liquid crystal photonic paper.

[0124] The vacuum plasma cleaning intensity is 200W, and the cleaning time is 600s;

[0125] The hydrophobic agent selected is 1H,1H,2H,2H-perfluorooctyltrimethoxysilane liquid;

[0126] The vapor deposition process was carried out at a temperature of 30℃ for 8 hours.

[0127] Physical photographs and cross-polarized reflectance photographs of the prepared biphasic blue phase liquid crystal photonic paper are shown below. Figure 10As shown. The bidirectional blue phase liquid crystal photonic paper is firmly bonded to the substrate, and the surface is flat.

[0128] To further highlight the functionality of the bipolar blue phase liquid crystal photonic paper in this invention, nematic liquid crystal ink 5CB was inkjet-printed onto the resulting photonic paper, and the paper was heated to 40°C. The isotropic ink penetrates and fills the pores of the blue phase polymer network, causing the blue phase lattice to expand, and the printed pattern exhibits a color that changes over time. With increasing heating time, the printed pattern not only reflects both left- and right-handed rotating light simultaneously, but the reflected light also exhibits independent wavelength changes, such as... Figure 11 As shown. The results of the printed pattern observed under different circular polarizers after heating for 780 min are as follows. Figure 12 As shown, the circular pattern consists of an upper pattern reflecting cyan left-handed light and a lower pattern reflecting green right-handed light. When viewed through a left-handed circular polarizer, only the cyan circular pattern is visible, while when viewed through a right-handed circular polarizer, only the green circular pattern is visible. By combining the differences in the results observed under different circular polarizers with the reflection spectrum and polarized photographs, a dynamic circular polarization anti-counterfeiting function is achieved.

[0129] Example 2

[0130] The preparation of bipolar blue phase liquid crystal photonic paper is the same as in Example 1, except that some parameters of the preparation steps in Example 1 are modified as follows:

[0131] The second spacer 32 has a thickness of 12.5 μm.

[0132] The formulation of the left-handed blue phase liquid crystal mixture is as follows: 56.4 wt% non-polymerizable nematic commercial mixed liquid crystal monomer HTG135200, 28.9 wt% single double-bond polymerizable monomer RM105, 9.6 wt% two double-bond polymerizable monomer RM257, 3.1 wt% left-handed dopant S5011, 1.5 wt% crosslinking agent TMPTA and 0.5 wt% photoinitiator I-651.

[0133] The thickness of the first spacer 31 is 25 μm.

[0134] The formulation of the right-handed blue phase liquid crystal mixture is as follows: 60.5 wt% non-polymerizable nematic commercial mixed liquid crystal monomer HTG135200, 24.2 wt% single double-bond polymerizable monomer RM105, 8.1 wt% double-bond polymerizable monomer RM257, 5.2 wt% right-handed dopant LC756, 1.5 wt% crosslinking agent TMPTA and 0.5 wt% photoinitiator I-651.

[0135] The preparation steps and other parameters used are the same as in Example 1.

[0136] Photographs of the bisexual blue phase liquid crystal photonic paper prepared in Example 2 and cross-polarized reflectance photographs are shown below. Figure 13 As shown. The reflectance spectrum after printing the same pattern using nematic ink 5CB and heating at 40°C for 65 minutes is as follows. Figure 14 As shown, this demonstrates the circular polarization anti-counterfeiting feature of the pattern, which can simultaneously reflect left-handed and right-handed light of different wavelengths.

[0137] Example 3

[0138] The preparation of bipolar blue phase liquid crystal photonic paper is the same as in Example 1, except that some parameters of the preparation steps in Example 1 are modified as follows:

[0139] The second spacer 32 has a thickness of 12.5 μm.

[0140] The formulation of the left-handed blue phase liquid crystal mixture is as follows: 56.9 wt% non-polymerizable nematic commercial mixed liquid crystal monomer HTG135200, 28.9 wt% single double-bond polymerizable monomer RM105, 9.6 wt% two double-bond polymerizable monomer RM257, 2.6 wt% left-handed dopant S5011, 1.5 wt% crosslinking agent TMPTA and 0.5 wt% photoinitiator I-651.

[0141] The thickness of the first spacer 31 is 25 μm.

[0142] The formulation of the right-handed blue phase liquid crystal mixture is as follows: 44.5 wt% non-polymerizable nematic commercial mixed liquid crystal monomer HTG135200, 35.9 wt% single double-bond polymerizable monomer RM105, 11.9 wt% double-bond polymerizable monomer RM257, 5.2 wt% right-handed dopant LC756, 2 wt% crosslinking agent TMPTA and 0.5 wt% photoinitiator I-651.

[0143] The preparation steps and other parameters used are the same as in Example 1.

[0144] Photographs of the biphasic blue phase liquid crystal photonic paper prepared in Example 3 and cross-polarized reflectance photographs are shown below. Figure 15 As shown. The reflectance spectrum after printing the same pattern using nematic ink 5CB and heating at 40°C for 130 min is as follows. Figure 16 As shown, this demonstrates the circular polarization anti-counterfeiting feature of the pattern, which can simultaneously reflect left-handed and right-handed light of different wavelengths.

[0145] In summary, through the above three preferred examples, it can be understood that factors such as the thickness of the first and second blue phase liquid crystal polymer films, the content of chiral dopants, and the content of non-photopolymerizable liquid crystal components do not affect the successful preparation of bipolar photonic paper. The parameters can be modified according to requirements to control the wavelength change range and rate, and it can be applied to the field of dynamic circular polarization anti-counterfeiting.

[0146] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all the implementation methods here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A bidirectional blue phase liquid crystal photonic paper, characterized in that, The structure of this photonic paper includes: First substrate, and A first blue phase liquid crystal polymer template and a second blue phase liquid crystal polymer template are sequentially disposed on the first substrate from bottom to top; The first blue phase liquid crystal polymer template and the second blue phase liquid crystal polymer template have opposite chirality.

2. The bipolar blue phase liquid crystal photonic paper according to claim 1, characterized in that, The first blue phase liquid crystal polymer template reflects left-handed light, and the second blue phase liquid crystal polymer template reflects right-handed light, or The first blue phase liquid crystal polymer template reflects right-handed light, and the second blue phase liquid crystal polymer template reflects left-handed light.

3. The bipolar blue phase liquid crystal photonic paper according to claim 1, characterized in that, The first and second blue phase liquid crystal polymer templates are blue phase liquid crystal polymer films with opposite chirality and containing nanoscale pores.

4. The bipolar blue phase liquid crystal photonic paper according to claim 1, characterized in that, The structure of the photonic paper also includes an anchoring layer disposed on the first substrate between the first substrate and the first blue phase liquid crystal polymer template. Preferably, the anchoring layer is a layer structure obtained by spin-coating a 3-(methacryloyloxy)propyltrimethoxysilane solution onto the first substrate and then drying and curing it.

5. The bidirectional blue phase liquid crystal photonic paper according to claim 1, characterized in that, The first substrate is one of glass plate, quartz plate, and ITO plate.

6. The method for preparing biphasic blue phase liquid crystal photonic paper according to any one of claims 1-5, characterized in that, The preparation method includes the following steps: An anchoring layer is formed on the surface of the first substrate; A first liquid crystal cell is provided, wherein the first liquid crystal cell comprises a first substrate having an anchoring layer formed on its surface, a third substrate disposed opposite to the first substrate, and a second spacer disposed between the first substrate and the third substrate to form an enclosed space together with the first substrate and the third substrate. A first liquid crystal mixture is added to the first liquid crystal cell, cooled to the blue phase, and cured by ultraviolet light to obtain a third blue phase liquid crystal polymer film. The film is then eluted with an organic solvent to obtain a third blue phase liquid crystal polymer template containing nanoscale pores. A second liquid crystal cell is provided, wherein the second liquid crystal cell comprises a third blue phase liquid crystal polymer template, a second substrate disposed opposite to the third blue phase liquid crystal polymer template, and a first spacer disposed between the third blue phase liquid crystal polymer template and the second substrate, which together form an enclosed space with the third blue phase liquid crystal polymer template and the second substrate. A second liquid crystal mixture with a chiral agent having the opposite rotation to the first liquid crystal mixture is added to the second liquid crystal cell. Part of the second liquid crystal mixture penetrates into the pores of the third blue phase liquid crystal polymer film, is cooled to the blue phase, and is cured by ultraviolet light to obtain a bipolar blue phase liquid crystal polymer film. The film is then eluted with an organic solvent to obtain the first blue phase liquid crystal polymer template and the second blue phase liquid crystal polymer template. The obtained structure is subjected to surface hydrophobic treatment to obtain the bipolar blue phase liquid crystal photonic paper.

7. The preparation method according to claim 6, characterized in that, The organic solvent is selected from N,N-dimethylformamide, acetone, and ethyl acetate; Preferably, the thickness of the second spacer is 5–25 μm; Preferably, the thickness of the first spacer is 10–50 μm; Preferably, the thickness ratio of the second spacer to the first spacer is 1:(1.5 to 3.5), more preferably 1:(2 to 3).

8. The application of bipolar blue phase liquid crystal photonic paper as described in any one of claims 1-5 in circular polarization anti-counterfeiting.

9. The application according to claim 8, characterized in that, The application includes the following steps: Anti-counterfeiting patterns are inkjet printed on the bipolar blue phase liquid crystal photonic paper; Heat the sample and observe the printed pattern using both left-handed and right-handed circular polarizers.

10. The application according to claim 9, characterized in that, The ink used in the inkjet printing is one of 5CB, 6CB, or 8CB; Preferably, the heating temperature is 35–50°C.

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