A structural color anti-counterfeiting film based on microlens array and preparation method thereof

Abstract

The present invention relates to a structural color anti-counterfeiting film based on a microlens array and a preparation method thereof, belonging to the field of microstructure anti-counterfeiting technology, comprising the following steps: (1) preparing a colloidal crystal microsphere array by a gas-liquid interface assembly method, and transferring the colloidal crystal microsphere array to a cleaned silicon wafer substrate; (2) preparing a PDMS concave array template; (3) preparing a microlens array; (4) preparing a periodic micro-nano cylindrical structure; (5) locally heating and melting and deforming the periodic micro-nano cylindrical structure. The method of the present invention can achieve a novel anti-counterfeiting effect having both a dynamic change effect and an angle-dependent color function, and has not only important scientific research value, but also great application value.

Description

Technical Field

[0001] The invention relates to a structural color anti-counterfeiting film and a preparation method thereof, and in particular to a structural color anti-counterfeiting film based on a microlens array and a preparation method thereof, and belongs to the technical field of microstructure anti-counterfeiting. Background Art

[0002] In recent years, the application of dynamic 3D imaging technology based on microlens arrays has extended to the field of printing and packaging, and has become a hot spot for research and development in the printing and packaging industry. The research on dynamic three-dimensional anti-counterfeiting images has important scientific and practical significance, but it currently faces problems such as low technical maturity, single pattern changes, and difficulty in rapid preparation.

[0003] In response to the above problems, Chinese invention patent CN109285439A proposes a method that adopts a two-level concave-convex structure design, uses different coatings to contrast and highlight the concave-convex structure, and combines a microlens array to effectively improve the security performance of graphic anti-counterfeiting film, which partially solves the current problem of poor printing effect of micro-graphic structure and poor graphic effect.

[0004] Chinese invention patent CN110415602A provides a two-color dynamic anti-counterfeiting film and a preparation method thereof. The anti-counterfeiting film can present two colors at the same time, and at the same time has a dynamic visual effect. Different images will be presented when observed from different angles. It has a good anti-counterfeiting effect and is not easy to be imitated.

[0005] Chinese invention patent CN109979310A proposes a graphic protection structure based on a dynamic anti-counterfeiting film. A graphic layer is compounded on the basis of the dynamic anti-counterfeiting film to protect the graphic layer from wear and tear. At the same time, the dynamic graphics and the graphic layer graphics are compounded together for display, which not only meets the intuitiveness of traditional trademark display, but also enriches the display effect of anti-counterfeiting labels.

[0006] The above technology adopts a colored printing method to solve the problem of contrast of micro-images. Specifically, it is a micro-groove filling method, which makes the micro-image area into a groove structure and then fills the groove with colored ink. However, these preparation methods have very high requirements for ink filling and printing process, and are difficult to control in actual operation, and the change effect is relatively simple.

[0007] Therefore, studying a structural color anti-counterfeiting film based on a microlens array and having both dynamic change effects and rich optical color change effects and a preparation method thereof not only has important scientific research value, but also has great application value. Summary of the invention

[0008] One of the purposes of the present invention is to provide a structural color anti-counterfeiting film based on a microlens array which has both a dynamic change effect and a rich optical color change effect.

[0009] The above object of the present invention is achieved through the following technical solutions:

[0010] A structural color anti-counterfeiting film based on a microlens array is characterized by comprising a polyethylene terephthalate (PET) substrate, a structural color micro-pattern layer on one side and a microlens array layer on the other side; the structural color micro-pattern layer is provided with a deformed periodic micro-nano cylindrical structure.

[0011] Preferably, the period of the periodic micro-nano cylindrical structure is 200-800 nm, the diameter of the cylinder in the periodic micro-nano cylindrical structure is 200-500 nm, and the height of the cylinder is 150-500 nm.

[0012] Preferably, the deformation refers to deformation of the edge of the cylinder.

[0013] Preferably, the deformation of the edge of the cylinder means that the edge of the cylinder forms a certain radius of curvature.

[0014] Preferably, the radius of curvature is 50-150 nm.

[0015] Preferably, the aperture size of the microlenses in the microlens array layer is 30-80 μm, preferably 56 μm; the focal length is 80-100 μm, preferably 90.15 μm.

[0016] Preferably, the polyethylene terephthalate (PET) substrate has a thickness of 70-100 μm, preferably 90 μm.

[0017] Preferably, the unit size of the structural color micro-pattern in the structural color micro-pattern layer is 20-30 μm, preferably 26 μm, and the spacing is 10-30 μm, preferably 20 μm.

[0018] Another object of the present invention is to provide a method for preparing a structural color anti-counterfeiting film based on a microlens array; by combining a patterned structural color film and a microlens array, a new anti-counterfeiting film is formed that has both a dynamic change effect and an angle-dependent color function. This method is simple and efficient and has good application prospects in the field of packaging anti-counterfeiting.

[0019] The above object of the present invention is achieved through the following technical solutions:

[0020] A method for preparing a structural color anti-counterfeiting film based on a microlens array comprises the following steps:

[0021] (1) A silicon wafer substrate is subjected to ultrasonic oscillation in acetone, anhydrous ethanol and deionized water respectively, and after being blown dry with nitrogen, it is placed in an ultraviolet ozone cleaning machine for surface hydrophilic treatment; colloidal crystal microspheres are selected, the particle size of the colloidal crystal microspheres is 2-100 μm, and the colloidal crystal microspheres are dispersed in deionized water to form a colloidal crystal microsphere dispersion liquid, and the mass concentration of the colloidal crystal microsphere dispersion liquid is 0.2-15%; a colloidal crystal microsphere array is prepared by a gas-liquid interface assembly method, and the colloidal crystal microsphere array is transferred to the cleaned silicon wafer substrate to obtain a two-dimensional colloidal crystal film;

[0022] (2) using the two-dimensional colloidal crystal film described in step (1) as a template, mixing the elastomer polydimethylsiloxane (PDMS) and the curing agent in a certain mass ratio, stirring evenly, and obtaining a polydimethylsiloxane (PDMS) precursor polymer, then casting the prepared polydimethylsiloxane (PDMS) precursor polymer on the two-dimensional colloidal crystal film, placing it in a vacuum drying oven after standing, and heating it to cure the polydimethylsiloxane (PDMS) and form a soft film, and removing the two-dimensional colloidal crystal film to obtain a polydimethylsiloxane (PDMS) concave array template;

[0023] (3) spin coating a certain thickness of photoresist on a polyethylene terephthalate (PET) substrate to obtain a photosensitive film; imprinting the polydimethylsiloxane (PDMS) concave array template prepared in step (2) onto the photosensitive film, and then irradiating it with ultraviolet (UV) light for a certain period of time to cure the photosensitive film, and then peeling the polydimethylsiloxane (PDMS) concave array template therefrom to obtain a microlens array;

[0024] (4) Spin coating a certain thickness of photoresist on the other side of the polyethylene terephthalate (PET) substrate in the microlens array obtained in (3), and preparing a periodic micro-nano cylindrical structure by using an ultraviolet nanoimprint method;

[0025] (5) Nanosecond laser pulses are used to act on the periodic micro-nano cylindrical structure, causing the periodic micro-nano cylindrical structure to be locally heated and melted and deformed, thereby causing color changes. At this time, the color of the pattern written directly on the background color changes, thereby achieving the preset effect.

[0026] In the process of achieving different color regulation, color regulation is achieved by precisely controlling the laser energy; the periodic micro-nano cylindrical structure has a certain initial color. When the laser energy is adjusted to a specific value, it is scanned at a certain speed, and the cylindrical structure is locally heated and melted and deformed, thereby causing color changes. At this time, the pattern color is directly written on the background color and changes, thereby achieving the preset effect.

[0027] Preferably, in step (1), the colloidal crystal microspheres are one of polystyrene, silicon dioxide, titanium dioxide or polymethyl methacrylate.

[0028] Preferably, in step (1), the particle size of the colloidal crystal microspheres is 2-100 μm.

[0029] Preferably, in step (2), the mass ratio of the elastomer polydimethylsiloxane (PDMS) to the curing agent is 15:1-5:1, preferably 10:1.

[0030] Preferably, in step (2), the heating temperature of the vacuum drying oven is 60°C-95°C.

[0031] Preferably, in step (2), the heating treatment time is 20 min-40 min.

[0032] Preferably, the photoresist in step (3) is ultraviolet nanoimprint photoresist with a thickness of 5-50 μm.

[0033] Preferably, in step (3), the UV light source has an illumination intensity of 500-1500 mW / m 2

[0034] Preferably, in step (3), the UV light exposure time is 5-50s.

[0035] Preferably, in step (3), the aperture size of the microlenses in the microlens array is in the range of 10-100 μm.

[0036] Preferably, in step (3), the thickness of the PET substrate is 20-200 μm.

[0037] Preferably, in step (3), the focal length of the microlens array is 20-210 μm.

[0038] Preferably, in step (4), the photoresist is ultraviolet light curing glue (UV glue) with a thickness of 100-500nm.

[0039] Preferably, in step (4), in the UV nanoimprinting method, the applied pressure is 2-10 bar, and the UV light intensity is 500-1500 mW / m 2 , the illumination time is 10-50 seconds.

[0040] Preferably, in step (4), the period of the periodic micro-nano cylindrical structure is 200-800 nm, the cylinder diameter is 200-500 nm, and the cylinder height is 150-500 nm.

[0041] Preferably, in step (5), the peak wavelength, half-width and peak intensity of the reflected light, which are important parameters affecting the photonic crystal band gap, are controlled by precisely controlling multiple parameters such as laser energy and action time, thereby achieving patterned color presentation.

[0042] Preferably, in step (5), the wavelength of the pulse laser used for the nanosecond laser pulse is in the range of 266nm-589nm, the pulse width is 3-30ns, the laser energy is 0-1000nJ, and the laser energy control accuracy is 1nJ.

[0043] Preferably, in step (5), the nanosecond laser pulse acts on the periodic micro-nano cylindrical structure for a time of 0-100 ms, and the laser spot diameter is 10-100 μm.

[0044] Preferably, in step (5), the periodic micro-nano cylindrical structure has a certain initial color. When the laser energy is adjusted to 0-1000nJ, it is scanned at a speed of 1-200mm / min, and the cylindrical structure is locally heated and melted and deformed, thereby causing a color change. At this time, the pattern color is directly written on the background color to change, thereby achieving a preset effect.

[0045] Preferably, in step (5), the laser scanning speed is 1-200 mm / min.

[0046] Preferably, in step (5), the size of the structural color pattern unit is 5-50 μm, and the spacing is 10-50 μm.

[0047] Preferably, the deformation refers to deformation of the edge of the cylinder.

[0048] Preferably, the deformation of the edge of the cylinder means that the edge of the cylinder forms a certain radius of curvature.

[0049] Preferably, the radius of curvature is 50-150 nm.

[0050] Beneficial effects:

[0051] The structural color anti-counterfeiting film based on the microlens array and the preparation method thereof provided by the present invention utilize the combination of the patterned structural color film and the microlens array to form a novel anti-counterfeiting film having a dynamic change effect and a function of angle-dependent color. Compared with the prior art, the present invention has many advantages such as being suitable for large-scale batch rapid preparation, low cost, green and environmentally friendly, and having a wide range of applications. It not only has important scientific research value, but also has great application value.

[0052] In order to make the purpose, technical solutions and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments, but it is not intended to limit the protection scope of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1It is a schematic diagram of the cross-sectional structure of the structural color anti-counterfeiting film based on the microlens array in Example 1 of the present invention.

[0054] Figure 2 It is a flow chart of the preparation of the microlens array layer in Example 1 of the present invention.

[0055] Figure 3 This is a flow chart for preparing the structural color anti-counterfeiting film in Example 1 of the present invention.

[0056] Figure 4 It is a schematic diagram of the structure and effect diagram of the structural color anti-counterfeiting film formed in step (4) of preparing the structural color anti-counterfeiting film based on the microlens array in Example 1 of the present invention.

[0057] Figure 5 It is a schematic diagram of the structure and effect diagram of the structural color anti-counterfeiting film formed in step (4) of preparing the structural color anti-counterfeiting film based on the microlens array in Example 3 of the present invention.

[0058] Main reference numerals:

[0059] 1 Microlens array layer 2 PET substrate

[0060] 3 Structural color micro pattern layer 4 Silicon wafer

[0061] 5 Colloidal microspheres 6 Deionized water

[0062] 7 Polydimethylsiloxane (PDMS) 8 Photoresist

[0063] 9 Periodic micro-nano cylindrical structure 10 Laser beam

[0064] 11 Laser 12 First structural color pattern

[0065] 13 Second structural color pattern DETAILED DESCRIPTION

[0066] Unless otherwise specified, the raw materials used in the specific embodiments of the present invention are all common raw materials available on the market, and the equipment and methods used are all common equipment and methods available in the art.

[0067] The method for preparing a structural color anti-counterfeiting film based on a microlens array of the present invention utilizes a composite of a patterned structural color film and a microlens array, adopts a gas-liquid interface assembly method to prepare a colloidal crystal microsphere array, utilizes PDMS to replicate a concave array template, and then utilizes a nanoimprinting method to prepare the microlens array. At the same time, a laser post-processing method for a periodic microstructure surface is utilized to achieve patterned color presentation.

[0068] The present invention can achieve both a dynamic change effect and an anti-counterfeiting effect of an angle-dependent color function.

[0069] Example 1

[0070] A method for preparing a structural color anti-counterfeiting film based on a microlens array comprises the following steps:

[0071] (1) A silicon wafer was ultrasonically vibrated in acetone, anhydrous ethanol and deionized water for 10 minutes respectively, and then dried with nitrogen, and then placed in a UV ozone cleaning machine for surface hydrophilic treatment; colloidal microspheres were polystyrene microspheres with a particle size of 90 μm, which were dispersed in deionized water to form a colloidal crystal microsphere dispersion liquid with a mass concentration of 1%; a colloidal crystal microsphere array was prepared by a gas-liquid interface assembly method, and was transferred to a cleaned silicon wafer substrate to obtain a two-dimensional colloidal crystal film;

[0072] (2) Using the two-dimensional colloidal crystal film obtained in step (1) as a template, the elastomer PDMS and the curing agent are mixed in a mass ratio of 10:1, and stirred evenly to obtain a PDMS precursor polymer. Subsequently, the prepared PDMS precursor polymer is carefully cast on the two-dimensional colloidal crystal film, and after standing, it is placed in a vacuum drying oven and heated at 80° C. for 30 min to solidify the PDMS and form a soft film, and the two-dimensional colloidal crystal film is removed to obtain a PDMS concave array template;

[0073] (3) Spin-coat a 15 μm thick photoresist on the PET substrate, and imprint the PDMS concave array template prepared in step (2) onto the photoresist to obtain a photosensitive film; then, use an intensity of 800 mW / m 2 The photosensitive film was cured after 15 seconds of UV light exposure, and the PDMS concave array template was peeled off to obtain the desired microlens array; the aperture size of the obtained microlens was 56 μm, the thickness of the PET substrate was 90 μm, and the focal length of the microlens array was 90.15 μm;

[0074] (4) Spin-coat a 500 nm thick photoresist on the other side of the PET substrate in the microlens array prepared in step (3), and use a UV nanoimprint method to prepare a periodic micro-nano cylindrical structure with a period of 400 nm, a cylinder diameter of 200 nm, and a cylinder height of 150 nm. The applied pressure of the UV nanoimprint method is 5 bar, and the UV light intensity is 600 mW / m 2 , the illumination time is 30s;

[0075] (5) Using nanosecond laser pulses with a pulse width of 5 ns, a wavelength of 266 nm, a laser energy of 350 nJ, and a spot diameter of 20 μm, the periodic structure is locally heated and melted and deformed. The laser energy control accuracy is 1 nJ and the scanning speed is 30 mm / min.

[0076] In the process of achieving different color regulation, color regulation is achieved by precisely controlling the laser energy; a periodic micro-nano cylindrical structure with a period of 400nm, a cylindrical diameter of 200nm, and a cylindrical height of 150nm is used as the substrate, and the initial color is blue. When the laser energy is adjusted to 350nJ, it is scanned at a speed of 30mm / min. At the same time, the cylindrical structure is locally heated and melted and deformed, so that its edge has a certain curvature radius. After deformation, the curvature radius at the edge is 75nm, which causes color change. At this time, the pattern color is directly written on the background color in green, thereby achieving the preset effect; the structural color pattern unit size is 26μm, and the spacing is 20μm; by precisely controlling multiple parameters such as laser energy and action time, the peak wavelength, half-width and peak intensity of the reflected light, which are important parameters affecting the band gap of the photonic crystal, are controlled, thereby achieving patterned color presentation.

[0077] like Figure 1 , which is a schematic diagram of the cross-sectional structure of a structural color anti-counterfeiting film based on a microlens array in Example 1 of the present invention, wherein 1 is a microlens array layer, the aperture size of the microlens is 56 μm, and the focal length is 90.15 μm, 2 is a PET substrate, and the thickness is 90 μm, and 3 is a structural color micro-pattern layer, and the pattern unit size is 26 μm, and the spacing is 20 μm;

[0078] like Figure 2 As shown in FIG. 1 , it is a flow chart of the preparation of the microlens array layer in Example 1 of the present invention, wherein 4 is a silicon wafer, 5 is a colloidal microsphere, 6 is deionized water, 7 is polydimethylsiloxane (PDMS), and 8 is a photoresist; first, the silicon wafer 4 is ultrasonically oscillated in acetone, anhydrous ethanol and deionized water for 10 minutes, blown dry with nitrogen and then placed in an ultraviolet ozone cleaning machine for surface hydrophilic treatment, a polystyrene microsphere dispersion with a particle size of 90 μm and a concentration of 1% is selected, and a colloidal crystal microsphere array 5 is prepared by a gas-liquid interface assembly method, and is transferred to the cleaned silicon wafer substrate 4 to obtain a two-dimensional colloidal crystal film; the two-dimensional colloidal The crystal film was used as a template, and the elastomer PDMS and the curing agent were mixed in a mass ratio of 10:1. After stirring evenly, the PDMS precursor polymer 7 was obtained. Subsequently, the prepared PDMS precursor polymer 7 was carefully cast on the two-dimensional colloidal crystal film. After standing, it was placed in a vacuum drying oven and heated at 80°C for 30 minutes to solidify the PDMS and form a soft film. The two-dimensional colloidal crystal film was removed to obtain a PDMS concave array template; a 15 μm thick photoresist 8 was spin-coated on the PET substrate, and the prepared PDMS concave array template was imprinted on the photoresist to obtain a photosensitive film; then, the photosensitive film was heated with an intensity of 800 mW / m 2The photosensitive film was cured after irradiation with UV light for 15 seconds, and the PDMS concave array template was peeled off to obtain a microlens array layer; the aperture size of the obtained microlens was 56 μm, the thickness of the PET substrate was 90 μm, and the focal length of the microlens array was 90.15 μm;

[0079] like Figure 3 , which is a flow chart of the preparation of the structural color anti-counterfeiting film in Example 1 of the present invention, wherein 9 is a periodic micro-nano cylindrical structure with a period of 400nm, a cylindrical diameter of 200nm, and a cylindrical height of 150nm; 10 is a laser beam with a pulse width of 5ns, a wavelength of 266nm, and a spot diameter of 20μm; by controlling the laser energy and action time, structural color patterns of different colors are directly written on the periodic structure with background color;

[0080] like Figure 4 1 is a schematic diagram of the structure of the structural color anti-counterfeiting film formed in step (4) of preparing the structural color anti-counterfeiting film based on the microlens array in Example 1 of the present invention and a rendering of the effect thereof, wherein 11 is a laser, 12 is a first structural color pattern (a structural color pattern after being magnified by the microlens array); in the process of achieving specific color regulation, color regulation is achieved by precisely controlling the laser energy according to the pre-customized first structural color pattern 12; a periodic micro-nano cylindrical pattern with a period of 400 nm, a cylindrical diameter of 200 nm, and a cylindrical height of 150 nm is used. The structure is a substrate, and the initial color is blue. A nanosecond laser pulse with a pulse width of 5ns, a wavelength of 266nm, and a spot diameter of 20μm is applied to this periodic structure. When the laser energy is adjusted to 350nJ (the laser energy control accuracy is 1nJ), it is scanned at a speed of 30mm / min, and the cylindrical structure is locally heated and melted and deformed, so that its edge has a certain radius of curvature. The radius of curvature at the edge after deformation is 75nm, thereby causing color change. At this time, the pattern color is directly written on the background color, which is green, thereby achieving the preset effect. The structural color pattern unit size in this embodiment 1 is 26μm and the spacing is 20μm; when the sample is observed perpendicular to the plane where the microlens is located, an enlarged structural color pattern can be found. At the same time, when observed at a certain angle (such as 30 degrees to the normal direction), the color of the structural color pattern changes, that is, when observed perpendicular to the sample surface, the first structural color pattern 12 is green, and when observed at an angle of 30 degrees to the normal direction, the first structural color pattern 12 is blue.

[0081] Example 2

[0082] A method for preparing a structural color anti-counterfeiting film based on a microlens array comprises the following steps:

[0083] (1) A silicon wafer was ultrasonically vibrated in acetone, anhydrous ethanol and deionized water for 10 minutes respectively, and then dried with nitrogen, and then placed in a UV ozone cleaning machine for surface hydrophilic treatment; colloidal microspheres were polystyrene microspheres with a particle size of 90 μm, which were dispersed in deionized water to form a colloidal crystal microsphere dispersion liquid with a mass concentration of 1%; a colloidal crystal microsphere array was prepared by a gas-liquid interface assembly method, and was transferred to a cleaned silicon wafer substrate to obtain a two-dimensional colloidal crystal film;

[0084] (2) Using the two-dimensional colloidal crystal film obtained in step (1) as a template, the elastomer PDMS and the curing agent are mixed in a mass ratio of 10:1, and stirred evenly to obtain a PDMS precursor polymer. Subsequently, the prepared PDMS precursor polymer is carefully cast on the two-dimensional colloidal crystal film, and after standing, it is placed in a vacuum drying oven and heated at 80° C. for 30 min to solidify the PDMS and form a soft film, and the two-dimensional colloidal crystal film is removed to obtain a PDMS concave array template;

[0085] (3) Spin-coat a 15 μm thick photoresist on the PET substrate, and imprint the PDMS concave array template prepared in step (2) onto the photoresist to obtain a photosensitive film; then, use an intensity of 800 mW / m 2 The photosensitive film was cured after 15 seconds of UV light exposure, and the PDMS concave array template was peeled off to obtain the desired microlens array layer; the aperture size of the obtained microlens was 56 μm, the thickness of the PET substrate was 90 μm, and the focal length of the microlens array was 90.15 μm;

[0086] (4) Spin-coat a 500 nm thick photoresist on the other side of the PET substrate in the microlens array prepared in step (3), and use a UV nanoimprint method to prepare a periodic micro-nano cylindrical structure with a period of 300 nm, a cylinder diameter of 150 nm, and a cylinder height of 150 nm. The applied pressure of the UV nanoimprint method is 3 bar, and the UV light intensity is 500 mW / m 2 , the illumination time is 20s;

[0087] (5) Using nanosecond laser pulses with a pulse width of 2 ns, a wavelength of 355 nm, a laser energy of 200 nJ, and a spot diameter of 15 μm, the periodic structure is locally heated and melted to deform the cylindrical structure, so that its edge has a certain curvature radius. After deformation, the curvature radius at the edge is 80 nm. The laser energy control accuracy is 1 nJ, and the scanning speed is 20 mm / min.

[0088] In the process of achieving different color regulation, color regulation is achieved by precisely controlling the laser energy; a periodic micro-nano cylindrical structure with a period of 300nm, a cylindrical diameter of 150nm, and a cylindrical height of 150nm is used as the substrate, and the initial color is purple. When the laser energy is adjusted to 200nJ, it is scanned at a speed of 20mm / min, and the cylindrical structure is locally heated and melted and deformed, so that its edge has a certain curvature radius. After deformation, the curvature radius at the edge is 80nm, thereby causing color change. At this time, the pattern color is directly written on the background color in yellow, thereby achieving the preset effect; the structural color pattern unit size is 25μm, and the spacing is 25μm; by precisely controlling multiple parameters such as laser energy and action time, the peak wavelength, half-width and peak intensity of the reflected light, which are important parameters affecting the band gap of the photonic crystal, are controlled, thereby achieving patterned color presentation.

[0089] In Example 2 of the present invention, the aperture size of the microlens array in the structural color anti-counterfeiting film based on the microlens array is 56 μm, the focal length is 90.15 μm, the thickness of the PET substrate is 90 μm, the pattern unit size in the structural color micro-pattern layer is 25 μm, and the pitch is 25 μm;

[0090] In Example 2 of the present invention, in the process of achieving specific color regulation, color regulation is achieved by precisely controlling laser energy; a periodic micro-nano cylindrical structure with a period of 300nm, a cylinder diameter of 150nm, and a cylinder height of 150nm is used as a substrate, and the initial color is purple. A nanosecond laser pulse with a pulse width of 2ns, a wavelength of 355nm, and a spot diameter of 15μm is applied to the periodic structure. When the laser energy is adjusted to 200nJ (the laser energy control accuracy is 1nJ), the scanning speed is 20mm / min, and the cylindrical structure is locally heated and melted and deformed, so that its edge has a certain curvature radius. After deformation, the curvature radius at the edge is 80nm, thereby causing a color change. At this time, the pattern color is directly written on the background color in yellow, thereby achieving the preset effect. The unit size of the structural color pattern in this embodiment 2 is 25 μm, and the spacing is 25 μm. When the sample is observed in a direction perpendicular to the plane where the microlens is located, an enlarged structural color pattern can be found. At the same time, when observed at a certain angle (such as 30 degrees to the normal direction), the color of the structural color pattern changes, that is, when observed perpendicular to the sample surface, the structural color pattern is yellow, and when observed at an angle of 30 degrees to the normal direction, the structural color pattern is green.

[0091] Example 3

[0092] A method for preparing a structural color anti-counterfeiting film based on a microlens array comprises the following steps:

[0093] (1) A silicon wafer was ultrasonically vibrated in acetone, anhydrous ethanol and deionized water for 10 minutes respectively, and then dried with nitrogen, and then placed in a UV ozone cleaning machine for surface hydrophilic treatment; colloidal microspheres were polystyrene microspheres with a particle size of 70 μm, which were dispersed in deionized water to form a colloidal crystal microsphere dispersion liquid with a mass concentration of 0.6%; a colloidal crystal microsphere array was prepared by a gas-liquid interface assembly method, and was transferred to a cleaned silicon wafer substrate to obtain a two-dimensional colloidal crystal film;

[0094] (2) Using the two-dimensional colloidal crystal film described in (1) as a template, the elastomer PDMS and the curing agent are mixed in a mass ratio of 10:1, and stirred evenly to obtain a PDMS precursor polymer. The prepared PDMS precursor polymer is then carefully cast on the two-dimensional colloidal crystal film. After standing, it is placed in a vacuum drying oven and heated at 80° C. for 30 min to solidify the PDMS and form a soft film. The two-dimensional colloidal crystal film is removed to obtain a PDMS concave array template;

[0095] (3) Spin-coat a 10 μm thick photoresist on the PET substrate, and imprint the PDMS concave array template prepared in step (2) onto the photoresist to obtain a photosensitive film; then, use 800 mW / m 2 The photosensitive film was cured after 10s of UV light exposure, and the PDMS concave array template was peeled off to obtain the desired microlens array layer; the aperture size of the obtained microlens was 40 μm, the thickness of the PET substrate was 80 μm, and the focal length of the microlens array was 80.15 μm;

[0096] (4) Spin-coating a 500 nm thick photoresist on the other side of the PET substrate of the microlens array obtained in step (3) and using an ultraviolet nanoimprint method to prepare a periodic micro-nano cylindrical structure with a period of 400 nm, a cylinder diameter of 200 nm, and a cylinder height of 150 nm; the applied pressure of the ultraviolet nanoimprint method is 5 bar, and the ultraviolet light intensity is 600 mW / m 2 , the illumination time is 30s;

[0097] (5) A laser pulse with a pulse width of 5 ns, a wavelength of 532 nm, and a spot diameter of 20 μm is applied to the periodic structure, causing the periodic micro-nano cylindrical structure to be locally heated and melted and deformed;

[0098] In the process of achieving different color regulation, specific color regulation is achieved by precisely controlling the laser energy according to the pre-customized first structural color pattern 12; a periodic micro-nano cylindrical structure with a period of 400nm, a cylindrical diameter of 200nm, and a cylindrical height of 150nm is used as the substrate, and the initial color is blue. A nanosecond laser pulse with a pulse width of 5ns, a wavelength of 532nm, and a spot diameter of 20μm is applied to the periodic structure. When the laser energy is adjusted to 350nJ (the laser energy control accuracy is 1nJ), the laser is scanned at a speed of 30mm / min, and the cylindrical structure is locally heated and melted and deformed, so that its edge has a certain radius of curvature and the deformation is reduced. The radius of curvature at the rear edge is 75nm, which causes color change. At this time, the pattern color written directly on the background color is green; on this basis, according to the pre-customized second structural color pattern 13, other positions are selected, the laser energy output is controlled to be 580nJ, and the scanning speed is 30mm / min. At the same time, the cylindrical structure is locally heated and melted and deformed, so that its edge has a certain radius of curvature. The radius of curvature at the edge after deformation is 60nm, which causes color change. At this time, the pattern color written directly on the background color is orange, so as to achieve the preset effect; there are two sizes of structural color pattern units, one of which is 20μm with a spacing of 20μm, and the other is 30μm with a spacing of 20μm. The color effects of these two structural color units are also different when observed from different angles, that is, when observed perpendicular to the sample surface, the first structural color pattern 12 is green, and the second structural color pattern 13 is orange. When observed at an angle of 30 degrees to the normal direction, the first structural color pattern 12 is blue, and the second structural color pattern 13 is green.

[0099] In Example 3 of the present invention, the aperture size of the microlens in the microlens array layer is 40 μm, the focal length is 80.15 μm, the thickness of the PET substrate is 80 μm, and the pattern unit sizes of the structural color micro-pattern are two, one is 20 μm with a pitch of 20 μm, and the other is 30 μm with a pitch of 20 μm.

[0100] like Figure 5, which is a schematic diagram of the structure of the structural color anti-counterfeiting film formed in step (4) of preparing the structural color anti-counterfeiting film based on the microlens array in Example 3 of the present invention and a rendering of the effect; in the process of realizing color patterning, according to the pre-customized pattern, the nano-micro-columns are deformed in different areas by laser direct writing, and different energies lead to different degrees of deformation of the nano-micro-columns, thereby showing structural color patterns with different color effects; a periodic micro-nano cylindrical structure with a period of 400nm, a cylindrical diameter of 200nm, and a cylindrical height of 150nm is used as the substrate, and the initial color is blue. When the laser energy is adjusted to 350nJ, it is scanned at a speed of 30mm / min, and the cylindrical structure is locally heated and melted and deformed, so that its edges The edge has a certain curvature radius, and the curvature radius at the edge after deformation is 75nm, which causes color change. At this time, the pattern color written directly on the background color is green; on this basis, according to the pre-customized pattern 13, other positions are selected, the laser energy output is controlled to be 580nJ, and the scanning speed is 30mm / min. At the same time, the cylindrical structure is locally heated and melted and deformed, so that its edge has a certain curvature radius. The curvature radius at the edge after deformation is 60nm, which causes color change. At this time, the pattern color written directly on the background color is orange, thereby achieving the preset effect; the structural color pattern unit size is two, one of which is 20μm with a spacing of 20μm, and the other is 30μm with a spacing of 20μm. Observe that the color effects of these two structural color units are different. When the sample is observed perpendicularly to the plane where the microlens is located, an enlarged structural color pattern can be found. At the same time, when observed at a certain angle (such as 30 degrees to the normal direction), the color of the structural color pattern changes. That is, when observed perpendicularly to the sample surface, the first structural color pattern 12 is green and the second structural color pattern 13 is orange. When observed at an angle of 30 degrees to the normal direction, the first structural color pattern 12 is blue and the first structural color pattern 13 is green.

[0101] It can be seen from the above embodiments that the present invention can achieve a new anti-counterfeiting effect with both a dynamic change effect and an angle-dependent color function, which not only has important scientific research value, but also has great application value.

[0102] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail, but do not limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A structural color anti-counterfeiting film based on a microlens array, characterized in that: It comprises a polyethylene terephthalate substrate, a structural color micro-pattern layer is provided on one side, and a micro-lens array layer is provided on the other side; a deformed periodic micro-nano cylindrical structure is provided on the structural color micro-pattern layer; the deformation refers to deformation of the edge of the cylinder; the deformation of the edge of the cylinder refers to the formation of a certain curvature radius on the edge of the cylinder, and the curvature radius is 50-150nm; the period of the periodic micro-nano cylindrical structure is 200-800nm, the diameter of the cylinder in the periodic micro-nano cylindrical structure is 200-500nm, and the height of the cylinder is 150-500nm; the aperture size of the microlens in the micro-lens array layer is 30-80μm; the focal length is 80-100μm; the thickness of the polyethylene terephthalate substrate is 70-100μm; the unit size of the structural color micro-pattern in the structural color micro-pattern film is 20-30μm, and the spacing is 10-30μm.

2. The method for preparing the structural color anti-counterfeiting film based on the microlens array according to claim 1, comprising the following steps: (1) The silicon wafer substrate is subjected to ultrasonic oscillation in acetone, anhydrous ethanol and deionized water respectively, and after being blown dry with nitrogen, it is placed in a UV ozone cleaning machine for surface hydrophilic treatment; colloidal crystal microspheres are selected, the particle size of the colloidal crystal microspheres is 2-100 μm, and the colloidal crystal microspheres are dispersed in deionized water to form a colloidal crystal microsphere dispersion liquid, and the mass concentration of the colloidal crystal microsphere dispersion liquid is 0.2-15%; the colloidal crystal microsphere array is prepared by a gas-liquid interface assembly method, and the colloidal crystal microsphere array is transferred to the cleaned silicon wafer substrate to obtain a two-dimensional colloidal crystal film; (2) Using the two-dimensional colloidal crystal film described in step (1) as a template, the elastomer polydimethylsiloxane and the curing agent are mixed in a certain mass ratio, and stirred evenly to obtain a polydimethylsiloxane precursor polymer. Subsequently, the prepared polydimethylsiloxane precursor polymer is cast on the two-dimensional colloidal crystal film, and after standing, it is placed in a vacuum drying oven and heated to cure the polydimethylsiloxane and form a soft film, and the two-dimensional colloidal crystal film is removed to obtain a polydimethylsiloxane concave array template; (3) Spin-coating a photoresist of a certain thickness on a polyethylene terephthalate substrate to obtain a photosensitive film; imprinting the polydimethylsiloxane concave array template prepared in step (2) onto the photosensitive film, and then irradiating the photosensitive film with ultraviolet light for a certain exposure time to cure the photosensitive film, and then peeling the polydimethylsiloxane concave array template from the photosensitive film to obtain a microlens array layer; (4) Spin coating a certain thickness of photoresist on the other side of the polyethylene terephthalate substrate in the microlens array obtained in (3), and preparing a periodic micro-nano cylindrical structure by using an ultraviolet nanoimprinting method; (5) Nanosecond laser pulses are used to act on the periodic micro-nano cylindrical structure, causing the periodic micro-nano cylindrical structure to be locally heated and melted and deformed.

3. The method for preparing a structural color anti-counterfeiting film based on a microlens array according to claim 2, characterized in that: In step (1), the colloidal crystal microspheres are one of polystyrene, silicon dioxide, titanium dioxide or polymethyl methacrylate.

4. The method for preparing a structural color anti-counterfeiting film based on a microlens array according to claim 3, characterized in that: In step (2), the mass ratio of the polydimethylsiloxane to the curing agent is 10:1; the heating temperature of the vacuum drying oven is 60° C.-95° C., and the heating time is 20 min-40 min.

5. The method for preparing a structural color anti-counterfeiting film based on a microlens array according to claim 4, characterized in that: In step (3), the photoresist is an ultraviolet nanoimprint photoresist with a thickness of 5-50 μm; the UV light source has an illumination intensity of 500-1500 mW / m 2 , exposure time is 5-50s.

6. The method for preparing a structural color anti-counterfeiting film based on a microlens array according to claim 5, characterized in that: In step (4), the photoresist is a UV curable adhesive with a thickness of 100-500 nm; the applied pressure of the UV nanoimprinting method in step (4) is 2-10 bar, and the UV light intensity is 500-1500 mW / m 2 , the illumination time is 10-50 seconds.

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