Optically anisotropic element and method of use and application thereof

Abstract

This invention relates to the field of optical anti-counterfeiting technology, specifically to an optical anisotropic element and its usage and application. It comprises a first photoalignment layer, a first optical retardation layer, a cholesteric liquid crystal layer, a second photoalignment layer, and a second optical retardation layer, stacked sequentially. The optical anisotropic element of this invention, comprising the sequentially stacked first photoalignment layer, first optical retardation layer, cholesteric liquid crystal layer, second photoalignment layer, and second optical retardation layer, allows for independent display of different invisible patterns on both the front and back sides, significantly increasing information capacity and anti-counterfeiting complexity, and solving the problem of limited information on one side in traditional single-sided anti-counterfeiting methods. The cholesteric liquid crystal layer in this invention is obtained by stacking cholesteric liquid crystal layers with two peak wavelengths, and the absolute value of the difference between the two peak wavelengths is ≥15nm. This further expands the element pattern from simple positive and negative switching to different color switching, further enhancing visual recognition and anti-counterfeiting security.

Description

Technical Field

[0001] This invention relates to the field of optical anti-counterfeiting technology, specifically to an optical anisotropic element and its usage and application. Background Technology

[0002] Generating invisible information based on graphic liquid crystal optical anisotropy technology is an advanced method in the field of anti-counterfeiting. Its core utilizes the phase difference characteristics of liquid crystal materials to exhibit specific optical changes under the action of polarized light, thereby realizing the storage and identification of invisible information. It has been widely used in various high-security anti-counterfeiting scenarios.

[0003] Chinese invention patent application CN107300734A discloses a method for generating invisible information based on a liquid crystal molecule alignment promoting layer and liquid crystal material. This scheme precisely controls the arrangement of liquid crystal molecules to form a large number of liquid crystal pixel regions with different orientations. Combined with a complex layer structure design, the pixel regions are transformed into macroscopically identifiable invisible information, and the corresponding invisible anti-counterfeiting features can be observed through a polarizer. However, this scheme only involves a single invisible information layer structure, resulting in the element only being able to carry a single invisible information, with limited information storage dimensions; the identification method relies on a universal polarizer, which is not practical or widely applicable; functionally, it can only realize optical changes of a single pattern and cannot achieve flipping to switch between different patterns, making it difficult to meet the needs of high-security anti-counterfeiting scenarios for multiple information verification, convenient identification, and dynamic features. Therefore, it is urgent to increase the capacity of invisible information through innovative structural design, optimize the identification method, and improve the anti-counterfeiting level and ease of application of the element. Summary of the Invention

[0004] The first aspect of the present invention provides an optical anisotropic element, comprising a first photoalignment layer, a first optical retardation layer, a cholesteric liquid crystal layer, a second photoalignment layer, and a second optical retardation layer stacked sequentially.

[0005] This invention's optical anisotropic element employs a specific structural design consisting of a first photoalignment layer, a first optical retardation layer, a cholesteric liquid crystal layer, a second photoalignment layer, and a second optical retardation layer stacked sequentially, overcoming the limitations of existing liquid crystal anti-counterfeiting technologies that rely solely on single-information storage. Possibly due to the synergistic effect of the two optical retardation layers, a dual-information storage design is achieved through layered optical control. This not only enriches the information storage dimensions of the element but also provides a technical basis for dual-information comparison in anti-counterfeiting verification, effectively solving the problem of insufficient anti-counterfeiting dimensions in traditional single-sided invisible information. Simultaneously, relying on the optical synergy and directional control characteristics between layers, the front and back of the element can independently carry and display different invisible patterns, significantly increasing information storage capacity while further enhancing anti-counterfeiting complexity, successfully addressing the pain points of traditional single-sided anti-counterfeiting technologies, such as single-information limitations and insufficient anti-counterfeiting reliability. Further research reveals that the cholesteric liquid crystal layer in this invention's optical anisotropic element is obtained by stacking cholesteric liquid crystal layers with two peak wavelengths, and the absolute value of the difference between the two peak wavelengths is ≥15nm. This further expands the element pattern from simple positive and negative switching to different color switching, further enhancing visual recognition and anti-counterfeiting security.

[0006] The cholesteric liquid crystal layer is obtained by stacking cholesteric liquid crystal layers with two peak wavelengths.

[0007] Optionally, the absolute value of the difference between the two peak wavelengths is ≥15nm.

[0008] Optionally, the two peak wavelengths of the cholesteric liquid crystal layer are a levorotatory cholesteric liquid crystal layer and a dextrorotatory cholesteric liquid crystal layer, respectively.

[0009] Both the first optical retardation layer and the second optical retardation layer have at least two regions that are perpendicular to each other in the optical axis direction; the regions that are perpendicular to each other in the optical axis direction constitute a patterned optical retardation layer.

[0010] The regions of the first optical retardation layer that are perpendicular to each other in the optical axis direction constitute a first pattern, and the regions of the second optical retardation layer that are perpendicular to each other in the optical axis direction constitute a second pattern.

[0011] Both the first and second photoalignment layers are composed of photoalignment materials, wherein the photoalignment materials are selected from at least one of III-1 to III-15: III-1: poly[oxy-4-[4-[4-[(E)-2-methoxycarbonyl-vinyl]-phenyl]-phenoxy]-butyl]-]-methyl-methylenesilyl], III-2: poly[oxy-6-[6-[4-[(E)-2-methoxycarbonyl-vinyl]-phenyl]-cyclohexyloxy]-hexyl]-1-methyl-methylenesilyl], III-3: poly[oxy-4-[4-[4-[(E)-2-methoxycarbonyl-vinyl]-phenoxycarbonyl]-phenoxy]-butyl]-methyl-methylenesilyl-co-oxy] -4-[4-[4-[(E)-2-hexyloxycarbonyl-vinyl]-phenoxycarbonyl]-phenoxy]-butyl]-methyl-methylenesilyl], III-4: poly[oxy-4-[4-[4-[(E)-2-methoxycarbonyl-vinyl]-phenoxycarbonyl]-phenoxy]-butyl]-methyl-methylenesilyl-co-oxy-6-[4-[4-[4-[(E)-2-methoxycarbonyl-vinyl]-phenoxycarbonyl]-phenoxy]-hexyl]-methyl-methylenesilyl], III-5: poly[1-[6-[4-[2-methyl-4-[(E)-2-methoxycarbonyl-vinyl]-phenoxycarbonyl]-phenoxy]-hexyloxycarbonyl]-1-methyl-ethylidene], I II-6: Poly[1-[4-[4-[2-methyl-4-[(E)-2-methoxycarbonyl-vinyl]-phenoxycarbonyl]-phenoxy]-butoxycarbonyl]-1-methyl-ethylidene], III-7: Poly[1-[2-[4-[2-methoxy-4-[(E)-2-methoxycarbonyl-vinyl]-phenoxycarbonyl]-phenoxy]-ethoxycarbonyl]-1-methyl-ethylidene], III-8: Poly[1-[3-[4-[2-methoxy-4-[(E)-2-methoxycarbonyl-vinyl]-phenoxycarbonyl]-phenoxy]-propoxycarbonyl]-1-methyl-ethylidene], III-9: Poly[1-[2-[4-[(E)-2-methoxycarbonyl]-[4-[(E)-2-methoxycarbonyl]-[4-[(E)-2-methoxycarbonyl]-[4-[4-[(E)-2-methoxycarbonyl]-[4-[4-[4-[4-[2-methoxycarbonyl]-[4-[4-[(E)-2-methoxycarbonyl]-[4-[4-[4-[4-[4-[2-methoxycarbonyl] ...4-[2-methoxycarbonyl]-[4-[4-[4-[4-[2-methoxycarbonyl]-[4-[4-[4-[ [1-[2-[4-[(E)-2-methoxycarbonyl-vinyl]-phenoxy]-ethoxycarbonyl]-1-methyl-ethylidene-co-1-[2-[4-[(E)-2-methoxycarbonyl-vinyl]-phenoxy]-ethoxycarbonyl]-1-methyl-ethylidene-co-1-[2-[4-[(E)-2-(2-methyl-butoxy)carbonyl-vinyl]-phenoxy]-ethoxycarbonyl-1-methyl-ethylidene-co-1-[2-hydroxy-ethoxycarbonyl]-1-methyl-ethylidene], III-10: Poly[1-[2-[4-[(E)-2-methoxycarbonyl-vinyl]-phenoxy]-ethoxycarbonyl-1-methyl-ethylidene-co-1-[2-hydroxy-ethoxycarbonyl]-1-methyl-ethylidene],III-11: Poly[1-[2-[4-[(E)-2-methoxycarbonyl-vinyl]-phenoxy]-ethoxycarbonyl]-1-methyl-ethylidene-co-1-[2-[4-[(E)-2-octyloxycarbonyl-vinyl]-phenoxy]-ethoxycarbonyl]-1-methyl-ethylidene-co-1-[2-hydroxy-ethoxycarbonyl]-1-methyl-ethylidene], III-12: Poly[1-[2-[4-[(E)-2-methoxycarbonyl-vinyl]-phenoxy]-ethoxycarbonyl]-1-methyl-ethylidene-co-1-[2-[4-[(E)-2-dodecyloxycarbonyl-vinyl]-phenoxy]-ethoxycarbonyl]-1-methyl-ethylidene-co-1-[2-hydroxy-ethoxycarbonyl]-1-methyl-ethylidene], II I-13: Poly[1-[4-[(E)-2-methoxycarbonyl-vinyl]-phenoxycarbonyl]-1-methyl-ethylidene co-1-[4-[(E)-2-hexyloxycarbonyl-vinyl]-phenoxycarbonyl]-1-methyl-ethylidene], III-14: Poly[1-[4-[(E)-2-methoxycarbonyl-vinyl]-phenoxycarbonyl]-1-methyl-ethylidene co-1-[4-[(E)-2-octyloxycarbonyl-vinyl]-phenoxycarbonyl]-1-methyl-ethylidene], III-15: Poly[1-[4-[(E)-2-ethoxycarbonyl-vinyl]-phenoxycarbonyl]-1-methyl-ethylidene co-1-[4-[(E)-2-pentoxycarbonyl-vinyl]-phenoxycarbonyl]-1-methyl-ethylidene].

[0012] This application research found that the photoalignment materials all contain linear photopolymer materials. After stepwise exposure to linearly polarized ultraviolet light, different orientations are generated in different regions of the photoalignment layer. A liquid crystal optical retardation layer is covered on the photoalignment layer. The liquid crystal molecules are arranged along the orientation direction of the photoalignment layer and cross-linked and cured under the action of ultraviolet light to form a birefringent phase retardation layer with optical anisotropy.

[0013] Both the first optical retardation layer and the second optical retardation layer are composed of nematic liquid crystal material, organic solvent and functional additives, wherein the functional additives include at least one of photoinitiator, surfactant, ultraviolet absorber, leveling agent, crosslinking agent and antioxidant.

[0014] Optionally, the nematic liquid crystal material includes at least one of formulas L1 to L11.

[0015] Formula L1; Formula L2; Formula L3; Formula L4; Formula L5; Formula L6; Formula L7; Formula L8; Formula L9; Formula L10; Formula L11.

[0016] The cholesteric liquid crystal layer is composed of nematic liquid crystal material, chiral dopant, organic solvent and functional additives.

[0017] The chiral dopant includes at least one of the following grades: CB15, R811, S811, R1011, S1011, R2011, S2011, R5011, S5011.

[0018] Optionally, the functional additives include photoinitiators, antioxidants, and leveling agents.

[0019] Optionally, the photoinitiator includes at least one of the following brands: Irgacure 184, Irgacure 369, Irgacure 907, Irgacure 1173, Irgacure TPO, Irgacure 819, and Irgacure ITX.

[0020] Optionally, the leveling agent includes at least one of the following brands: BYK-323, BYK-361, BYK-320, BYK-322, BYK-326, BYK-358N, BYK-361N, TEGO Flow 300, EFKA-3232, MOK-2019, MOK-2623, HY-323, HY-361N, LA-D819C, and LA-D887R.

[0021] Optionally, the antioxidant includes at least one of hindered amines and hindered phenols.

[0022] Optionally, the organic solvent includes at least one selected from butanone, cyclohexanone, acetone, methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate, butyl acetate, methyl propyl ketone, cyclopentanone, diisobutyl ketone, dioxane, dioxane, ethylene glycol methyl ether acetate, propylene glycol methyl ether acetate, N-methyl-2-pyrrolidone, N,N-dimethylacetamide, and N-methylpropionamide.

[0023] Optionally, the organic solvent is cyclohexanone.

[0024] The optical anisotropic element further includes a substrate layer, the material of which includes at least one of polyethylene naphthalate, polyethylene terephthalate, triacetyl cellulose (TAC), polypropylene, polycarbonate, polymethyl methacrylate (PMMA), and cyclic olefin copolymer (COP).

[0025] Optionally, the material used for the substrate layer includes an isotropic substrate, including one of TAC, PMMA, and COP.

[0026] The alignment layer and optical retardation layer can be laminated by coating. The coating method can apply the liquid crystal mixture to the substrate using conventional coating techniques such as spin coating, bar coating, or blade coating. Alternatively, conventional printing techniques, including screen printing, offset printing, roll-to-roll printing, letterpress printing, gravure printing, rotary gravure printing, flexographic printing, engraving gravure printing, pad printing, heat-sealing printing, inkjet printing, or printing with the aid of a printing mold or printing plate, can be used to apply the formulation liquid to the substrate or laminate it between layers.

[0027] The optical delay layer includes a waveplate with a phase delay of 3 / 16 to 5 / 16.

[0028] The second aspect of the present invention provides a method for using an optical anisotropic element, comprising the following steps: placing the optical anisotropic element on the surface of a light-emitting polarizing display screen; when the first optical retardation layer is close to the polarizing light source, rotating the optical anisotropic element to reveal a first pattern of the first optical retardation layer; continuing to rotate the element to switch between light and dark or different colors; flipping the optical anisotropic element so that the second optical retardation layer is close to the polarizing light source; rotating the optical anisotropic element to reveal a second pattern of the second optical retardation layer; continuing to rotate the element to switch between light and dark or different colors.

[0029] A second aspect of the present invention provides another method of using an optical anisotropic element, comprising the following steps: irradiating the optical anisotropic element with polarized light emitted from a polarization display screen; when the first optical retardation layer is close to the polarization light source, rotating the polarization light source to reveal a first pattern of the first optical retardation layer; continuing to rotate the element to switch between light and dark or different colors; flipping the optical anisotropic element over; when the second optical retardation layer is close to the polarization light source, rotating the element to reveal a second pattern of the second optical retardation layer; continuing to rotate the element to switch between light and dark or different colors.

[0030] Optionally, the polarization display screen includes the screen of an electronic device.

[0031] The screens of the electronic devices include computer screens, iPad screens, and mobile phone screens. The polarizers built into these displays convert the emitted light into polarized light, thus allowing the polarized display screen to be used as a tool for identifying the anisotropic optical elements of this invention.

[0032] The third aspect of this invention provides an application of an optical anisotropic element in the field of anti-counterfeiting of banknotes, passports, ID cards, product labels, and pharmaceutical packaging.

[0033] The optical anisotropic element identified by the polarization display screen according to the present invention comprises at least one cholesteric liquid crystal layer, which is composed of two cholesteric liquid crystal layers with a peak wavelength difference greater than 15 nm. The two cholesteric liquid crystal layers with a peak wavelength difference greater than 15 nm broaden the reflection peak width and element brightness. Preferably, the two cholesteric liquid crystal layers are a levorotatory cholesteric liquid crystal layer and a dextrorotatory cholesteric liquid crystal layer with a peak wavelength difference greater than 15 nm. The combination of levorotatory and dextrorotatory cholesteric liquid crystal layers expands the element pattern from simple positive and negative switching to different color switching.

[0034] The optical anisotropic element of this invention uses a 3 / 16-5 / 16 waveplate as its optical retardation layer. This layer converts incident linearly polarized light into circularly polarized or approximately circularly polarized light. Two regions perpendicular to the optical axes of the retardation layer respectively convert the incident linearly polarized light into left- or right-handed circularly polarized light. This left- or right-handed circularly polarized light is reflected or transmitted through the cholesteric liquid crystal layer surface, resulting in a contrast of light and shadow or different colors due to varying brightness or hues in the two regions perpendicular to the optical axes of the retardation layer.

[0035] Beneficial effects 1. The optical anisotropic element of the present invention comprises a first photoalignment layer, a first optical retardation layer, a cholesteric liquid crystal layer, a second photoalignment layer, and a second optical retardation layer stacked sequentially. Different invisible patterns can be displayed independently on the front and back sides, significantly improving information capacity and anti-counterfeiting complexity, and solving the problem of single-sided anti-counterfeiting information in traditional single-sided anti-counterfeiting methods.

[0036] 2. The cholesteric liquid crystal layer in the optical anisotropic element of the present invention is obtained by stacking cholesteric liquid crystal layers with two peak wavelengths, and the absolute value of the difference between the two peak wavelengths is ≥15nm. This can further expand the element pattern from simple positive and negative switching to different color switching, thereby further enhancing visual recognition and anti-counterfeiting security.

[0037] 3. The first optical retardation layer and the second optical retardation layer of the present invention each have at least two regions with mutually perpendicular optical axis directions, forming a patterned structure, so that the optical anisotropic element forms a high-contrast invisible pattern under polarized light, without the need for additional dyes or pigments, simplifying the manufacturing process.

[0038] 4. This invention uses electronic devices as polarization displays, eliminating the need for additional dedicated polarizers or detection equipment. It can directly interact with optical anisotropic elements, improving the ease of identification and making it suitable for everyday anti-counterfeiting scenarios, thus lowering the barrier to entry for users.

[0039] 5. The optical retardation layer thickness of this invention is precisely controlled to be a 3 / 16-5 / 16 waveplate, which can efficiently convert linearly polarized light into circularly polarized light, precisely matching the reflection wavelength of the cholesteric liquid crystal layer, and significantly improving pattern contrast and color purity. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of the structure of the optical anisotropic element in Example 1.

[0041] Figure 2 This is a schematic diagram of the structure of the optical anisotropic element in Example 2.

[0042] The structure includes: 1. First photoalignment layer; 2. First optical retardation layer; 31. Dextrorotatory cholesteric liquid crystal layer; 32. Levorotatory cholesteric liquid crystal layer; 4. Second photoalignment layer; 5. Second optical retardation layer. Detailed Implementation

[0043] Example 1 An optical anisotropic element, such as Figure 1 As shown, the layers are a first photoalignment layer 1, a first optical retardation layer 2, a cholesteric liquid crystal layer (dextral cholesteric liquid crystal layer 31), a second photoalignment layer 4, and a second optical retardation layer 5, which are stacked sequentially.

[0044] Both the first optical retardation layer 2 and the second optical retardation layer 5 have at least two regions perpendicular to each other in the optical axis direction. The regions perpendicular to each other in the optical axis direction of the first optical retardation layer 2 form a first pattern, and the regions perpendicular to each other in the optical axis direction of the second optical retardation layer 5 form a second pattern. The optical retardation layer includes a waveplate with a phase retardation of 1 / 4. The optical retardation value of the first optical retardation layer 2 is 115.3 nm, and the optical retardation value of the second optical retardation layer 5 is 136.3 nm.

[0045] The method for fabricating the optical anisotropic element comprises the following steps: S1, Dissolve photoalignment material III-13 in an organic solvent (cyclohexanone) to obtain an alignment solution with a mass concentration of 3%. Coat the alignment solution onto a 25μm PET surface and dry it. First, expose the first alignment region of the first photoalignment layer 1 in the first direction using linearly polarized ultraviolet light through a mask (negative pentagram). Remove the mask and expose the photoalignment layer with linearly polarized ultraviolet light perpendicular to the first exposure direction to form a bidirectionally exposed first photoalignment layer 1 with a dry thickness of 90nm. S2, using an organic solvent (cyclohexanone) to dissolve polymerizable liquid crystal L2 (96% wt), photoinitiator Irgacure 369 (3.5% wt), leveling agent BYK-322 (0.3% wt), and antioxidant 1076 (0.2% wt), a nematic liquid crystal formulation solution with a mass concentration of 20% was obtained. The nematic liquid crystal formulation solution was coated onto the first photoalignment layer 1, and after drying and curing, a first optical retardation layer 2 was formed on the first photoalignment layer 1, with a dry thickness of 1.27 μm.

[0046] S3, polymerizable liquid crystal L2 (92.5% wt), dextrorotatory chiral dopant R5011 (3.5% wt), photoinitiator Irgacure 369 (3.5% wt), leveling agent BYK-322 (0.3% wt), and antioxidant 1076 (0.2% wt) are dissolved in an organic solvent (cyclohexanone) to obtain a dextrorotatory cholesteric liquid crystal formulation solution with a mass concentration of 30%. The cholesteric liquid crystal formulation solution is coated on the first optical retardation layer 2, and after drying and curing, a dextrorotatory cholesteric liquid crystal layer 31 is formed on the first optical retardation layer 2 with a thickness of 3 μm.

[0047] S4, an alignment liquid is coated on the cholesteric liquid crystal layer and dried. First, linearly polarized ultraviolet light is used to expose the first alignment region of the second photoalignment layer 4 in the first direction through a mask (negative guilloché pattern). The mask is removed, and the photoalignment layer is exposed using linearly polarized ultraviolet light perpendicular to the first exposure direction to form a second photoalignment layer 4 exposed in both directions. The dry thickness of the second photoalignment layer 4 is 90 nm.

[0048] S5, a nematic liquid crystal formulation solution with a concentration of 24% (specific composition and ratio are the same as in S2) is coated on the second photoalignment layer 4. After drying and curing, a second optical retardation layer 5 is formed on the second photoalignment layer 4. The dry thickness of the second optical retardation layer 5 is 1.5 μm.

[0049] A method for using an optical anisotropic element comprises the following steps: placing the optical anisotropic element on the surface of a light-emitting polarization display screen; when the first optical retardation layer 2 is close to the polarization light source, rotating the optical anisotropic element reveals a first pattern on the first optical retardation layer 2; continuing to rotate the element causes the first pattern to switch between light and dark; flipping the optical anisotropic element so that the second optical retardation layer 5 is close to the polarization light source, rotating the optical anisotropic element reveals a second pattern on the second optical retardation layer 5; continuing to rotate the element causes the second pattern to switch between light and dark.

[0050] Another method of using an optical anisotropic element is as follows: Illuminate the optical anisotropic element with polarized light emitted from a polarization display screen. When the first optical retardation layer 2 is close to the polarization light source, rotate the polarization light source, and the first pattern of the first optical retardation layer 2 will appear. Continue to rotate the element, and the first pattern will switch between positive and negative light. Flip the optical anisotropic element over. When the second optical retardation layer 5 is close to the polarization light source, rotate the element, and the second pattern of the second optical retardation layer 5 will appear. Continue to rotate the element, and the second pattern will switch between positive and negative light.

[0051] Example 2 An optical anisotropic element comprises a first photoalignment layer 1, a first optical retardation layer 2, a cholesteric liquid crystal layer, a second photoalignment layer 4, and a second optical retardation layer 5, which are stacked sequentially.

[0052] The cholesteric liquid crystal layer is obtained by stacking two cholesteric liquid crystal layers with different peak wavelengths, namely a levorotatory cholesteric liquid crystal layer 32 and a dextrorotatory cholesteric liquid crystal layer 31, and the absolute value of the difference between the two peak wavelengths is 82 nm.

[0053] The optical retardation value of the first optical retardation layer 2 is 136.3 nm (thickness is 1.5 μm), and the optical retardation value of the second optical retardation layer 5 is 161.4 nm (thickness is 1.78 μm).

[0054] That is, Figure 2 As shown, the optical anisotropic element consists of a first photoalignment layer 1, a first optical retardation layer 2, a dextrorotatory cholesteric liquid crystal layer 31, a levorotatory cholesteric liquid crystal layer 32, a second photoalignment layer 4, and a second optical retardation layer 5, which are stacked sequentially.

[0055] The preparation method of the optical anisotropic element is the same as in Example 1, except that step S2-2 is inserted after step S2. Specifically, S2-2 involves using an organic solvent (cyclohexanone) to polymerize liquid crystal L2 (93.15% wt), a left-handed chiral dopant S5011 (2.85% wt), a photoinitiator Irgacure 369 (3.5% wt), a leveling agent BYK-322 (0.3% wt), and an antioxidant 1076 (0.2% wt) to obtain a 30% (w / w) L-cholesterol liquid crystal formulation. The L-cholesterol liquid crystal formulation is then coated onto the right-handed cholesterol liquid crystal layer 31. After drying and curing, a left-handed cholesterol liquid crystal layer 32 is formed on the right-handed cholesterol liquid crystal layer 31, with a thickness of 3 μm.

[0056] The method of using the optical anisotropic element is the same as in Example 1.

[0057] Comparative Example 1 An optical anisotropic element comprises a photoalignment layer, an optical retardation layer, and a cholesteric liquid crystal layer stacked sequentially. The fabrication method of the optical anisotropic element is the same as steps S1-S3 of Example 1.

[0058] The method of using the optical anisotropic element is the same as in Example 1.

[0059] Performance testing methods and data The results of using the optical anisotropic elements in the examples and comparative examples are recorded in Table 1.

[0060] Table 1

Claims

1. An optical anisotropic element, characterized in that, The optical anisotropic element comprises a first photoalignment layer, a first optical retardation layer, a cholesteric liquid crystal layer, a second photoalignment layer, and a second optical retardation layer, which are stacked sequentially.

2. The optical anisotropic element according to claim 1, characterized in that, The cholesteric liquid crystal layer is obtained by stacking cholesteric liquid crystal layers with two peak wavelengths.

3. The optical anisotropic element according to claim 2, characterized in that, The absolute value of the difference between the two peak wavelengths is ≥15nm.

4. The optical anisotropic element according to claim 3, characterized in that, The two peak wavelengths of the cholesteric liquid crystal layer are a levorotatory cholesteric liquid crystal layer and a dextrorotatory cholesteric liquid crystal layer, respectively.

5. The optical anisotropic element according to claim 1 or 4, characterized in that, Both the first optical retardation layer and the second optical retardation layer have at least two regions that are perpendicular to each other in the optical axis direction. The regions of the first optical retardation layer that are perpendicular to each other in the optical axis direction form a first pattern, and the regions of the second optical retardation layer that are perpendicular to each other in the optical axis direction form a second pattern.

6. The optical anisotropic element according to claim 1, characterized in that, The optical delay layer includes a waveplate with a phase delay of 3 / 16 to 5 / 16.

7. A method of using the optical anisotropic element according to claim 5, characterized in that, Includes the following steps: When an optical anisotropic element is placed on the surface of a light-emitting polarized display screen, and the first optical retardation layer is brought close to the polarized light source, rotating the optical anisotropic element reveals the first pattern of the first optical retardation layer. Continuing to rotate the element causes the first pattern to switch between light and dark or different colors. When the optical anisotropic element is flipped over and the second optical retardation layer is brought close to the polarized light source, rotating the optical anisotropic element reveals the second pattern of the second optical retardation layer. Continuing to rotate the element causes the second pattern to switch between light and dark or different colors.

8. A method of using the optical anisotropic element according to claim 5, characterized in that, Includes the following steps: When polarized light emitted from a polarization display screen is irradiated onto an optical anisotropic element, and the first optical retardation layer is brought close to the polarization light source, rotating the polarization light source reveals the first pattern of the first optical retardation layer. Continuing to rotate the element causes the first pattern to switch between light and dark or different colors. When the optical anisotropic element is flipped over, and the second optical retardation layer is brought close to the polarization light source, rotating the optical anisotropic element reveals the second pattern of the second optical retardation layer. Continuing to rotate the optical anisotropic element causes the second pattern to switch between light and dark or different colors.

9. The method of using the optical anisotropic element according to claim 7 or 8, characterized in that, The polarization display screen includes the screen of an electronic device.

10. An application of the optical anisotropic element according to any one of claims 1-6, characterized in that, It is used in the field of anti-counterfeiting of banknotes, passports, ID cards, product labels, and pharmaceutical packaging.

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