Photochromic laser printing film and preparation method and application thereof

Abstract

The invention discloses a photochromic laser printing film and a preparation method and application thereof.The photochromic laser printing film is composed of a base material layer, a photocatalytic discoloration layer and a protective layer, materials of the photocatalytic discoloration layer comprise a photocatalyst and metal ions capable of being reduced, and the colors of the metal ions change before and after being reduced; the photocatalyst is titanium dioxide nanoparticles and / or zinc oxide nanoparticles. The metal ions are reduced by utilizing photo-induced electrons of the semiconductor photocatalyst to form the irreversible metal nanoparticle color development layer, and once color change occurs, the color cannot be restored through illumination or other means, so that the anti-counterfeiting performance is remarkably improved. The preparation method is simple in process, free of release of harmful substances and suitable for large-scale industrial application, the green and environment-friendly requirements are met, the preparation process is easy to integrate with an existing production line, and the production cost is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of photochromic materials, and in particular to a photochromic laser printing film and a preparation method and application thereof. Background Art

[0002] Photochromic materials, as functional materials, exhibit unique color-changing properties under illumination. This property holds broad application prospects in a variety of fields, including anti-counterfeiting technology, information storage, and smart displays. Traditionally, photochromic materials rely on two main categories: organic molecules and inorganic materials. In the organic molecule field, compounds such as spiropyrans and azobenzenes achieve color change through photoisomerization reactions. While these materials offer high color sensitivity and a wide variety of color changes, the reversibility of their color change is a major limitation. Upon cessation of illumination, these organic molecules gradually return to their original state, restoring their color. This reversibility is particularly disadvantageous in anti-counterfeiting applications, as it can be easily counterfeited or reversed, thus reducing the anti-counterfeiting effectiveness. Inorganic photochromic materials, such as WO3 and MoO3, achieve color change through photoinduced redox reactions. While inorganic materials offer certain advantages in stability over organic molecules, they also suffer from relatively low color change efficiency and require high energy to trigger.

[0003] In addition to issues with reversibility and color-changing efficiency, traditional photochromic materials also have other shortcomings. For example, organic photochromic materials are prone to degradation under long-term sunlight or in high-temperature and high-humidity environments, causing color change failure and reducing the material's reliability and service life. Furthermore, many organic photochromic materials release harmful chemicals during preparation and use, posing potential threats to the environment and human health.

[0004] In terms of application areas, existing photochromic materials are mostly used for simple dynamic displays or anti-counterfeiting labels, and their performance is difficult to meet the needs of high-precision, high-security fields. In particular, in situations where a high degree of anti-counterfeiting and security is required, such as identity documents and passports, existing photochromic materials are difficult to effectively integrate with high-precision laser printing technology. The main reason is that their performance is not compatible with high-precision laser printing technology. This involves the synergistic effects of multiple factors, such as material properties (such as stability and environmental tolerance), process bottlenecks (for example, after the assembly of substrate + photochromic coating + protective layer, the physical properties of the photochromic material such as light transmittance and adhesion may affect laser penetration or pattern clarity), and security requirements, thus limiting their application potential in these fields. Summary of the Invention

[0005] In order to solve the above technical problems, the purpose of the present invention is to provide a photochromic laser printing film and its preparation method and application. By utilizing the photogenerated electrons of the photocatalyst to reduce metal ions, an irreversible metal nanoparticle color-developing layer is formed, which solves the reversibility and stability problems of traditional photochromic materials.

[0006] The above-mentioned object of the present invention is achieved through the following technical solutions:

[0007] The first aspect of the present invention provides a photochromic laser printing film, which is composed of a substrate layer, a photocatalytic color-changing layer and a protective layer. The material of the photocatalytic color-changing layer includes a photocatalyst and a reducible metal ion, and the color of the metal ions changes before and after reduction; the photocatalyst is titanium dioxide nanoparticles and / or zinc oxide nanoparticles.

[0008] The present invention utilizes the photogenerated electrons of the photocatalyst to reduce metal ions (such as Ag) in a directional manner. + →Ag 0 、Au 3+ →Au 0 、Cu 2+ →Cu 0 ) to form an irreversible metal nanoparticle color-developing layer; the reduction reaction process is regulated by laser wavelength and intensity to achieve precise development of the pattern (such as one-time printing of ID card information); the present invention sequentially coats a photocatalytic color-changing layer and a protective layer on the surface of the substrate layer to ensure that the color-changing reaction occurs only under laser excitation.

[0009] Furthermore, the photochromic laser printing film includes a substrate layer, a photocatalytic color-changing layer and a protective layer sequentially arranged on one side of the substrate layer.

[0010] Furthermore, the substrate layer is a transparent or translucent polymer film, the material of which is selected from one or more of polytetrafluoroethylene (PTFE), polyethylene terephthalate (PET), polyvinylidene fluoride (PVDF), and polycarbonate (PC), preferably PET. The substrate layer provides mechanical support and has excellent optical transparency.

[0011] In a specific embodiment, the molecular weight of the PTFE is 10 6 Da, the molecular weight of PET is 2×10 4 Da, the molecular weight of PVDF is 2×10 5 Da, the molecular weight of PC is 3×10 4 Da.

[0012] Furthermore, the thickness of the photocatalytic color-changing layer is 20-100 nm.

[0013] Furthermore, the photocatalyst is a semiconductor nanoparticle, and the semiconductor nanoparticle is titanium dioxide nanoparticle and / or zinc oxide nanoparticle (ZnO). The photocatalyst serves as a source of photogenerated electrons.

[0014] Furthermore, the particle size of the photocatalyst is 20-500 nm, preferably 50-100 nm.

[0015] Furthermore, the metal ion that can be reduced is Ag + 、Cu 2+ 、Au 3+ or Fe 3+ .

[0016] Furthermore, the thickness of the protective layer is 20-50 nm. The protective layer is a transparent protective film, the purpose of which is to prevent metal ions from being oxidized under non-light conditions.

[0017] Furthermore, the material of the protective layer is SiO2 and / or Al2O3.

[0018] A second aspect of the present invention provides a method for preparing the photochromic laser printing film according to the first aspect, comprising the following steps:

[0019] (1) uniformly mixing a photocatalyst with a reducible metal ion solution, and obtaining a photocatalytic color-changing layer material after static adsorption under light-proof conditions;

[0020] (2) coating the photocatalytic color-changing layer material obtained in step (1) on the substrate layer, forming a photocatalytic color-changing layer after drying, and preparing a protective layer on the photocatalytic color-changing layer to obtain the photochromic laser printing film.

[0021] The photochromic laser printing film produced by this invention exhibits irreversible color states during actual operation, and the color pattern requires a laser trigger of a specific wavelength, making it difficult to replicate. This invention eliminates the need for organic dyes, reducing chemical pollution, and can be integrated with existing laser printing equipment, lowering production costs.

[0022] Furthermore, in step (1), the photocatalyst is pretreated by calcining the photocatalyst at 300-350° C. in an air atmosphere for 2-6 hours to remove organic impurities adsorbed on the surface of the photocatalyst.

[0023] Furthermore, in step (1), the solvent of the reducible metal ion solution is water and / or an alcohol solvent, and the alcohol solvent can be ethanol, methanol, ethylene glycol, etc., preferably ethanol.

[0024] Furthermore, in step (1), the mass ratio of the metal ions in the reducible metal ion solution to the photocatalyst is: 0 <m金属离子 :m 光催化剂 ≤1, preferably: 0 <m 金属离子 :m 光催化剂 ≤0.05, more preferably: 0 <m 金属离子 :m 光催化剂 ≤0.01.

[0025] Furthermore, in step (1), the static adsorption time is 2-12 hours.

[0026] Furthermore, in step (2), the substrate layer is cleaned and dried to ensure a clean surface.

[0027] Furthermore, in step (2), the drying temperature is 40-60°C.

[0028] Furthermore, in step (2), the drying time is 4-6 hours.

[0029] Furthermore, in step (2), the drying process is performed by vacuum drying.

[0030] Furthermore, in step (2), the coating method is spray coating, spin coating, brush coating or dipping, preferably spray coating. The photocatalytic color-changing layer material is evenly coated on the substrate layer by spray coating or dipping.

[0031] In a specific embodiment, the photocatalytic color-changing layer material obtained in step (1) is in a powder or solution state.

[0032] Furthermore, in step (1), the photocatalyst and the reducible metal ion solution are mixed evenly, and after static adsorption under light-proof conditions, the solvent is removed to obtain a photocatalytic color-changing layer material (powder); in step (2), the solution of the photocatalytic color-changing layer material (powder) obtained in step (1) is coated on the substrate layer, and the photocatalytic color-changing layer is formed after drying.

[0033] Furthermore, in step (2), the solution of the photocatalytic color-changing layer material is prepared by dispersing the photocatalytic color-changing layer material (powder) in a solvent.

[0034] Furthermore, the solvent is a volatile low-toxic organic solvent such as water or ethanol.

[0035] Furthermore, in step (1), the photocatalyst and the reducible metal ion solution are mixed evenly, and a photocatalytic color-changing layer material (solution) is obtained after static adsorption under light-proof conditions; in step (2), the photocatalytic color-changing layer material (solution) obtained in step (1) is coated on the substrate layer, and a photocatalytic color-changing layer is formed after drying.

[0036] Furthermore, in step (3), the method for preparing the protective layer on the photocatalytic color-changing layer is a vapor deposition method or a sol-gel method.

[0037] In a specific embodiment, the method for preparing the photochromic laser printing film comprises the following steps:

[0038] (1) adding a photocatalyst to a reducible metal ion solution and stirring evenly, placing the solution in a dark place after mixing, and statically adsorbing the solution for a certain period of time to obtain a photocatalytic color-changing layer material;

[0039] (2) coating the photocatalytic color-changing layer material obtained in step (1) on the substrate layer, vacuum drying to form a photocatalytic color-changing layer, and covering the surface of the photocatalytic color-changing layer with a protective layer by a vapor deposition method or a sol-gel method to obtain the photochromic laser printing film.

[0040] A third aspect of the present invention provides an application of the photochromic laser printing film described in the first aspect in the field of laser printing.

[0041] The photochromic laser printing film provided by the present invention has high anti-counterfeiting properties, is environmentally friendly and has good stability. It can be seamlessly integrated with laser printing technology and is suitable for fields such as laser printing document anti-counterfeiting, providing a new technical solution for the development of high-security anti-counterfeiting materials.

[0042] Furthermore, a method for using the photochromic laser printing film for laser printing comprises the following steps: placing the photochromic laser printing film under laser irradiation to trigger a photocatalytic reduction reaction to form an irreversible color pattern.

[0043] Under laser irradiation, photocatalysts generate photogenerated electrons that reduce metal ions to metal nanoparticles, resulting in an irreversible color change. This invention achieves irreversibility in the photochromic process through a photocatalytic reduction reaction, solving the problem of traditional photochromic materials being easily counterfeited.

[0044] Furthermore, the photochromic process of the present invention is a permanent color change process. The photochromic laser printing film can change from colorless to light purple, purple, yellow, etc., but is not limited to the color series mentioned above, and the color pattern can be precisely controlled by laser parameters (wavelength, power, scanning speed).

[0045] Furthermore, the wavelength of the laser is 200-420 nm.

[0046] Furthermore, the irradiation time is 100 fs-60 min.

[0047] Compared with the prior art, the present invention has the following beneficial effects:

[0048] (1) The present invention utilizes the photogenerated electrons of semiconductor photocatalysts to reduce metal ions (such as Ag + →Ag 0 、Au 3+ →Au 0 、Cu 2+ →Cu 0 ), forming an irreversible metal nanoparticle color layer. Once the color change occurs, it cannot be restored to its original state by light or other means, which significantly improves the anti-counterfeiting performance. In addition, metal nanoparticles (such as Ag 0 、Au 0 、Cu 0 The color pattern can be stably preserved for more than 1000 hours in a high temperature (80°C) and high humidity (RH=90%) environment, meeting the long-term preservation requirements of identity cards, passports and other documents.

[0049] (2) The material used in the preparation of the present invention has a simple structure and does not require the use of organic dyes. Color development is achieved only through photocatalytic reduction of metal ions. The preparation process is simple and no harmful substances are released, which meets the requirements of green environmental protection. In addition, the preparation process (such as spin coating, spray coating, and vapor deposition) is easy to integrate with existing production lines, reducing production costs and being suitable for large-scale industrial applications.

[0050] (3) The present invention breaks through the reversibility limitation of photochromic materials and opens up new applications of photocatalytic materials in the field of anti-counterfeiting. It can not only be used for document anti-counterfeiting, but can also be expanded to high-density optical storage, smart packaging and other fields, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 These are the actual pictures of the Au / P25 powder in Example 1 before and after illumination; among them, (a) is the actual picture before illumination, and (b) is the actual picture after illumination.

[0052] Figure 2 2 is the XRD pattern of Au / P25 powder before and after irradiation in Example 1.

[0053] Figure 3TEM images and Mapping element distribution maps of the Au / P25 powder before and after illumination in Example 1; wherein, (a) is a bright field TEM image before illumination, (b) is a high-angle annular dark field TEM image before illumination, (c) is a full spectrum of O, Ti, and Au element distribution before illumination, (d) is an Au element distribution map before illumination, (e) is a Ti element distribution map before illumination, (f) is an O element distribution map before illumination, (g) is a bright field TEM image after illumination, (h) is a high-angle annular dark field TEM image after illumination, (i) is a full spectrum of O, Ti, and Au element distribution after illumination, (j) is an Au element distribution map after illumination, (k) is a Ti element distribution map after illumination, and (l) is an O element distribution map after illumination.

[0054] Figure 4 These are the actual pictures of the Au / P25 photochromic laser printing film prepared in Example 1 before and after illumination; wherein, (a) is the actual picture before illumination, and (b) is the actual picture after illumination.

[0055] Figure 5 TEM images and Mapping element distribution maps of the Au / P25 powder after illumination in Example 2; among them, (a) is a bright field TEM image, (b) is a high-angle annular dark field TEM image, (c) is a full spectrum of O, Ti, and Au element distribution, (d) is a Ti element distribution map, (e) is an Au element distribution map, and (f) is an O element distribution map.

[0056] Figure 6 These are the actual pictures of Au / P40 powder, Au / P60 powder and Au / P100 powder in Examples 2-4 before and after illumination; among them, (a) is the actual picture of Au / P40 powder in Example 2 before illumination, (b) is the actual picture of Au / P60 powder in Example 3 before illumination; (c) is the actual picture of Au / P100 powder in Example 4 before illumination, (d) is the actual picture of Au / P40 powder in Example 2 after illumination, (e) is the actual picture of Au / P60 powder in Example 3 after illumination, and (f) is the actual picture of Au / P100 powder in Example 4 after illumination.

[0057] Figure 7 This is the XPS graph of the Au 4f orbital of the Au / P25 powder after irradiation in Example 5.

[0058] Figure 8 These are the actual pictures of the Ag / P25 powder in Example 6 before and after illumination; among them, (a) is the actual picture before illumination, and (b) is the actual picture after illumination.

[0059] Figure 9These are the TEM images and Mapping element distribution maps of the Ag / P25 powder after illumination in Example 6; among them, (a) is a bright field TEM image, (b) is a high-angle annular dark field TEM image, (c) is a full spectrum of O, Ti, and Ag element distribution, (d) is an Ag element distribution map, (e) is a Ti element distribution map, and (f) is an O element distribution map.

[0060] Figure 10 These are the actual pictures of Ag / P40 powder, Ag / P60 powder and Ag / P100 powder in Examples 7-9 before and after illumination; among them, (a) is the actual picture of Ag / P40 powder in Example 7 before illumination, (b) is the actual picture of Ag / P60 powder in Example 8 before illumination; (c) is the actual picture of Ag / P100 powder in Example 9 before illumination, (d) is the actual picture of Ag / P40 powder in Example 7 after illumination, (e) is the actual picture of Ag / P60 powder in Example 8 after illumination, and (f) is the actual picture of Ag / P100 powder in Example 9 after illumination.

[0061] Figure 11 These are the actual pictures of the Ag / P25 photochromic laser printing film prepared in Example 10 before and after illumination; wherein, (a) is the actual picture before illumination, and (b) is the actual picture after illumination.

[0062] Figure 12 These are the actual pictures of the Cu / P25 powder in Example 11 before and after illumination; among them, (a) is the actual picture before illumination, and (b) is the actual picture after illumination.

[0063] Figure 13 These are the actual pictures of the Cu / P25 photochromic laser printing film prepared in Example 11 before and after illumination; wherein, (a) is the actual picture before illumination, and (b) is the actual picture after illumination.

[0064] Figure 14 These are the actual pictures of Fe / P25 powder before and after irradiation in Example 12; among them, (a) is the actual picture before irradiation, and (b) is the actual picture after irradiation.

[0065] Figure 15 These are the actual pictures of the Fe / P25 photochromic laser printing film prepared in Example 12 before and after illumination; wherein, (a) is the actual picture before illumination, and (b) is the actual picture after illumination.

[0066] Figure 16 These are the actual pictures of the Au / ZnO powder in Example 13 before and after illumination; among them, (a) is the actual picture before illumination, and (b) is the actual picture after illumination.

[0067] Figure 17These are the TEM images and Mapping element distribution maps of the Au / ZnO powder after illumination in Example 13; among them, (a) is a bright field TEM image, (b) is a high-angle annular dark field TEM image, (c) is a full spectrum of O, Zn, and Ag element distribution, (d) is an Ag element distribution map, (e) is a Zn element distribution map, and (f) is an O element distribution map.

[0068] Figure 18 These are the actual pictures of the Au / ZnO photochromic laser printing film prepared in Example 13 before and after illumination; wherein, (a) is the actual picture before illumination, and (b) is the actual picture after illumination.

[0069] Figure 19 These are the actual pictures of the Ag / ZnO powder in Example 14 before and after illumination; among them, (a) is the actual picture before illumination, and (b) is the actual picture after illumination.

[0070] Figure 20 These are the actual pictures of the Ag / ZnO photochromic laser printing film prepared in Example 14 before and after illumination; wherein, (a) is the actual picture before illumination, and (b) is the actual picture after illumination.

[0071] Figure 21 These are the actual pictures of the Cu / ZnO powder in Example 15 before and after illumination; among them, (a) is the actual picture before illumination, and (b) is the actual picture after illumination.

[0072] Figure 22 These are the actual pictures of the Cu / ZnO photochromic laser printing film prepared in Example 15 before and after illumination; wherein, (a) is the actual picture before illumination, and (b) is the actual picture after illumination.

[0073] Figure 23 These are the actual pictures of the Fe / ZnO powder in Example 16 before and after illumination; among them, (a) is the actual picture before illumination, and (b) is the actual picture after illumination.

[0074] Figure 24 These are the actual pictures of the Fe / ZnO photochromic laser printing film prepared in Example 16 before and after illumination; wherein, (a) is the actual picture before illumination, and (b) is the actual picture after illumination.

[0075] Figure 25 This is a physical picture of the color change of the P25 mixed solution obtained in Example 17 after being irradiated with light.

[0076] Figure 26TEM images and Mapping element distribution maps of the titanium dioxide powder treated in Comparative Example 1 after illumination; among them, (a) is a bright field TEM image (scale is 200nm), (b) is a bright field TEM image (scale is 100nm), (c) is a high-angle annular dark field TEM image, (d) is the O and Ti element distribution map, (e) is the Ti element distribution map, and (f) is the O element distribution map.

[0077] Figure 27 TEM images and Mapping element distribution maps of the ZnO powder treated in Comparative Example 2 after illumination; among them, (a) is a bright field TEM image, (b) is a bright field TEM image, (c) is a high-angle annular dark field TEM image, (d) is a full spectrum of O and Zn element distribution, (e) is a Zn element distribution map, and (f) is an O element distribution map.

[0078] Figure 28 This is a real picture of the color change of the SnO mixed solution obtained in Comparative Example 3 after light exposure.

[0079] Figure 29 This is a photo of the Au / P25 photochromic laser printing film prepared in Example 1 after ultraviolet light irradiation and high-temperature treatment.

[0080] Figure 30 This is a photo of the Au / P25 photochromic laser printing film prepared in Example 1 after being irradiated with ultraviolet light and then soaked in water.

[0081] Figure 31 This is a photo of the Au / P25 powder in Example 1 after being irradiated with ultraviolet light and then immersed in an acidic aqueous solution.

[0082] Figure 32 This is a photo of the Au / P25 powder in Example 1 after being irradiated with ultraviolet light and then immersed in a neutral aqueous solution.

[0083] Figure 33 This is a photo of the Au / P25 powder in Example 1 after being irradiated with ultraviolet light and then soaked in an alkaline aqueous solution.

[0084] Figure 34 This is a photo of the Ag / P60 powder in Example 8 after being irradiated with ultraviolet light and then immersed in an acidic aqueous solution.

[0085] Figure 35 This is a photo of the Ag / P25 powder in Example 6 after being irradiated with ultraviolet light and then immersed in a neutral aqueous solution.

[0086] Figure 36 This is a photo of the Ag / P25 powder in Example 10 after being irradiated with ultraviolet light and then soaked in an alkaline aqueous solution. DETAILED DESCRIPTION

[0087] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this invention pertains. The terms used in this specification of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0088] The present invention provides a photochromic laser printing film, which is composed of a substrate layer, a photocatalytic color-changing layer and a protective layer. The material of the photocatalytic color-changing layer includes a photocatalyst and reducible metal ions, and the color of the metal ions changes before and after reduction; the photocatalyst is titanium dioxide nanoparticles and / or zinc oxide nanoparticles.

[0089] The present invention also provides a method for preparing the above-mentioned photochromic laser printing film, comprising the following steps:

[0090] (1) uniformly mixing a photocatalyst with a reducible metal ion solution, and obtaining a photocatalytic color-changing layer material after static adsorption under light-proof conditions;

[0091] (2) coating the photocatalytic color-changing layer material obtained in step (1) on the substrate layer, forming a photocatalytic color-changing layer after drying, and preparing a protective layer on the photocatalytic color-changing layer to obtain the photochromic laser printing film.

[0092] The present invention verifies the long-term stability of the photochromic laser printing film in high temperature, high humidity, strong acid and strong alkaline environments, and provides a new technical solution for the development of high-security anti-counterfeiting materials.

[0093] The present invention will be further described below with reference to the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it. However, the embodiments are not intended to limit the present invention.

[0094] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, and the materials and reagents used are all commercially available unless otherwise specified.

[0095] The intensity of the ultraviolet light used in the following examples and comparative examples is 50 mW·cm -2 .

[0096] Example 1

[0097] A method for preparing an Au / P25 photochromic laser printing film comprises the following steps:

[0098] (1) Prepare 100 mg / L chloroauric acid solution with anhydrous ethanol as solvent. Add 5 g of titanium dioxide powder (P25) with a particle size of 25 nm to 500 mL of chloroauric acid solution. The mass ratio of gold ions to P25 is 0.0058. After stirring evenly, stand in the dark and open air for adsorption to allow the solvent to evaporate naturally to obtain Au / P25 powder.

[0099] (2) The Au / P25 powder obtained in step (1) and distilled water are mixed at a solid-liquid ratio of 1:20, and the obtained Au / P25 solution is coated on a PTFE membrane, which is then placed in an oven (50°C) and vacuum-dried for 5 hours to form a photocatalyst color-changing layer after drying. The SiO2 protective layer is then covered on the photocatalyst color-changing layer by a sol-gel method to obtain the Au / P25 photochromic laser printing film.

[0100] The actual picture of Au / P25 powder before and after light exposure in Example 1 is as follows: Figure 1 As shown, the prepared Au / P25 powder is white. After being irradiated with 365 nm ultraviolet light for 20 min, the powder color turns purple.

[0101] The Au / P25 powder in Example 1 was subjected to X-ray diffraction (XRD) tests before and after irradiation. The test results are shown in FIG. Figure 2 As shown in the figure, after UV irradiation, elemental gold is produced in the Au / P25 powder, but its production amount is small, resulting in a weak XRD test signal.

[0102] The Au / P25 powder in Example 1 before and after irradiation was further characterized in detail using transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDS). Figure 3 As shown in the figure, before illumination, Au(III) is in an ionic state and is evenly distributed on the surface of the substrate material P25. After illumination, new spherical particles appear on the substrate material P25. From the mapping element distribution diagram, it can be seen that the spherical particles are elemental gold particles.

[0103] The actual pictures of the Au / P25 photochromic laser printing film prepared in Example 1 before and after illumination are as follows: Figure 4 As shown, the color of the Au / P25 photochromic laser printed film before exposure to light is white, and the color turns purple after exposure to 365 nm ultraviolet light for 20 minutes.

[0104] Example 2

[0105] A method for preparing an Au / P40 photochromic laser printing film is basically the same as that of Example 1, except that the particle size of the titanium dioxide powder (P40) is 40 nm.

[0106] The Au / P40 powder in Example 2 after irradiation (365 nm UV light irradiation for 20 min) was further characterized in detail using transmission electron microscopy (TEM), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Figure 5 As shown in the figure, new spherical particles appear on the base material. From the mapping element distribution diagram, it can be seen that the spherical particles are single-element gold particles.

[0107] Example 3

[0108] A method for preparing an Au / P60 photochromic laser printing film is basically the same as that of Example 1, except that the particle size of the titanium dioxide powder (P60) is 60 nm.

[0109] Example 4

[0110] A method for preparing an Au / P100 photochromic laser printing film is substantially the same as that of Example 1, except that the particle size of the titanium dioxide powder (P100) is 100 nm.

[0111] The actual pictures of Au / P40 powder, Au / P60 powder and Au / P100 powder before and after illumination in Example 2-4 are as follows: Figure 6 As shown, before irradiation, the Au / P40 powder, Au / P60 powder, and Au / P100 powder in Examples 2-4 were all white. After irradiation with 365 nm ultraviolet light for 20 min, the Au / P40 powder turned into light gray-purple, the Au / P60 powder turned into light gray-purple, and the Au / P100 powder turned into off-white.

[0112] Example 5

[0113] A method for preparing an Au / P25 photochromic laser printing film comprises the following steps:

[0114] (1) Prepare 500 mg / L chloroauric acid solution with anhydrous ethanol as solvent. Add 5 g of titanium dioxide powder (P25) with a particle size of 25 nm to 100 mL of chloroauric acid solution. The mass ratio of gold ions to P25 is 0.0058. After stirring evenly, stand in the dark and open air for adsorption to allow the solvent to evaporate naturally to obtain Au / P25 powder.

[0115] (2) The Au / P25 powder obtained in step (1) and distilled water are mixed at a solid-liquid ratio of 1:20, and the obtained Au / P25 solution is coated on a PTFE membrane, which is then placed in an oven (50°C) and vacuum-dried for 5 hours to form a photocatalyst color-changing layer after drying. The SiO2 protective layer is then covered on the photocatalyst color-changing layer by a sol-gel method to obtain the Au / P25 photochromic laser printing film.

[0116] After irradiation by 365 nm ultraviolet light for 20 min, the Au / P25 powder in Example 5 changed to purple, and the Au / P25 powder after irradiation in Example 5 was characterized by X-ray photoelectron spectroscopy (XPS), and the characterization results are shown in Figure 7 As can be seen from the XPS analysis, the purple product is elemental gold nanoparticles.

[0117] Example 6

[0118] A preparation method of an Ag / P25 photochromic laser printing film, comprising the following steps:

[0119] (1) A 200 mg / L silver nitrate solution was prepared, with anhydrous ethanol as the solvent, 5 g of titanium dioxide powder (P25) with a particle size of 25 nm was added to 100 mL of the silver nitrate solution, the mass ratio of silver ions to P25 was 0.0026, and after stirring uniformly, it was placed in the dark and open to adsorb, and the solvent was naturally volatilized to obtain Ag / P25 powder.

[0120] (2) The Ag / P25 powder obtained in step (1) and distilled water were mixed according to a solid-liquid ratio of 1:20, the obtained Ag / P25 solution was coated on a PTFE film, and then it was placed in an oven (50°C) for vacuum drying for 5 h, and after drying, a photocatalyst color-changing layer was formed, and then a SiO2 protective layer was covered on the photocatalyst color-changing layer by a sol-gel method to obtain the Ag / P25 photochromic laser printing film.

[0121] The actual object pictures of the Ag / P25 powder before and after irradiation in Example 6 are shown in Figure 8 The prepared Ag / P25 powder is white, and after irradiation by 365 nm ultraviolet light for 20 min, the powder color changed to tan.

[0122] The TEM picture and the Mapping element distribution picture of the Ag / P25 powder after irradiation in Example 6 are shown in Figure 9 New substances appeared on the base material P25, and the Mapping element distribution picture shows that the newly generated substances are composed of elements Ag and O, and according to the brown appearance state, it is speculated that silver nanoparticles are formed.

[0123] Example 7

[0124] A preparation method of an Ag / P40 photochromic laser printing film, which is basically the same as Example 1, except that the particle size of the titanium dioxide powder (P40) is 40 nm.

[0125] Example 8

[0126] A method for preparing an Ag / P60 photochromic laser printing film is substantially the same as that of Example 1, except that the particle size of the titanium dioxide powder (P60) is 60 nm.

[0127] Example 9

[0128] A method for preparing an Ag / P100 photochromic laser printing film is substantially the same as that of Example 1, except that the particle size of the titanium dioxide powder (P100) is 100 nm.

[0129] The actual pictures of Ag / P40 powder, Ag / P60 powder and Ag / P100 powder before and after light exposure in Examples 7-9 are as follows: Figure 10 As shown, before irradiation, the Ag / P40 in Examples 2-4 was light grayish white, and the Ag / P60 powder and the Ag / P100 powder were both white. After irradiation with 365 nm ultraviolet light for 20 min, the Ag / P40 turned into earthy black, the Ag / P60 turned into earthy yellow, and the Ag / P100 powder turned into light yellow.

[0130] Example 10

[0131] A method for preparing an Ag / P25 photochromic laser printing film comprises the following steps:

[0132] (1) Prepare 50 mg / L silver nitrate solution with anhydrous ethanol as solvent. Add 5 g of titanium dioxide powder (P25) with a particle size of 25 nm to 100 mL of silver nitrate solution. The mass ratio of silver ions to P25 is 0.00065. After stirring evenly, stand in the dark and open air for adsorption for 2 h to obtain Ag / P25 powder.

[0133] (2) The Ag / P25 powder obtained in step (1) is coated on a PTFE membrane, which is then placed in an oven (40° C.) and vacuum-dried for 4 hours to form a photocatalyst color-changing layer. A SiO2 protective layer is then covered on the photocatalyst color-changing layer using a sol-gel method to obtain the Ag / P25 photochromic laser printing film.

[0134] The actual pictures of the Ag / P25 photochromic laser printing film prepared in Example 10 before and after irradiation are as follows: Figure 11 As shown, the color of the Ag / P25 photochromic laser printed film before exposure to light is white, and after exposure to 365nm ultraviolet light for 20 minutes, the color turns to rose red.

[0135] Example 11

[0136] A method for preparing a Cu / P25 photochromic laser printing film comprises the following steps:

[0137] (1) Prepare 100 mg / L copper nitrate solution with anhydrous ethanol as solvent. Add 5 g of titanium dioxide powder (P25) with a particle size of 25 nm to 100 mL of copper nitrate solution. The mass ratio of copper ion to P25 is 0.0007. After stirring evenly, stand in the dark and open air for adsorption to allow the solvent to evaporate naturally to obtain Cu / P25 powder.

[0138] (2) The Cu / P25 powder obtained in step (1) is coated on a PTFE membrane, which is then placed in an oven (50° C.) and vacuum-dried for 5 hours to form a photocatalyst color-changing layer. A SiO2 protective layer is then covered on the photocatalyst color-changing layer using a sol-gel method to obtain the Cu / P25 photochromic laser printing film.

[0139] The actual picture of Cu / P25 powder before and after light exposure in Example 11 is as follows: Figure 12 As shown, the prepared Cu / P25 powder is white. After being irradiated with 365nm ultraviolet light for 20min, the powder color turns into turquoise.

[0140] The actual pictures of the Cu / P25 photochromic laser printing film prepared in Example 11 before and after irradiation are as follows: Figure 13 As shown, the color of the Cu / P25 photochromic laser printed film without light exposure is white, and the color turns to cyan after being irradiated with 365nm ultraviolet light for 20 minutes.

[0141] Example 12

[0142] A method for preparing a Fe / P25 photochromic laser printing film comprises the following steps:

[0143] (1) Prepare a 100 mg / L ferric nitrate solution with anhydrous ethanol as the solvent. Add 5 g of titanium dioxide powder (P25) with a particle size of 25 nm to 100 mL of ferric nitrate solution. The mass ratio of iron ion to P25 is 0.00046. After stirring evenly, stand in the dark and open air for adsorption to allow the solvent to evaporate naturally to obtain Fe / P25 powder.

[0144] (2) The Fe / P25 powder obtained in step (1) is coated on a PTFE membrane, which is then placed in an oven (60°C) and vacuum-dried for 6 hours to form a photocatalyst color-changing layer. A SiO2 protective layer is then covered on the photocatalyst color-changing layer using a sol-gel method to obtain the Fe / P25 photochromic laser printing film.

[0145] The actual pictures of Fe / P25 powder before and after illumination in Example 12 are as follows: Figure 14 As shown, the prepared Fe / P25 powder is white. After being irradiated with 365 nm ultraviolet light for 20 min, the powder color turns light yellow.

[0146] The actual pictures of the Fe / P25 photochromic laser printing film prepared in Example 12 before and after irradiation are as follows: Figure 15 As shown, the color of the Fe / P25 photochromic laser printed film without light exposure is white, and the color turns to light yellow after being irradiated with 365nm ultraviolet light for 20 minutes.

[0147] Example 13

[0148] A method for preparing an Au / ZnO photochromic laser printing film comprises the following steps:

[0149] (1) Prepare 100 mg / L chloroauric acid solution with anhydrous ethanol as solvent, add 5 g ZnO powder with a particle size of 100 nm to 100 mL chloroauric acid solution, and the mass ratio of gold ions to ZnO is 0.0012. After stirring evenly, stand in the dark and open air for adsorption to allow the solvent to evaporate naturally to obtain Au / ZnO powder.

[0150] (2) The Au / ZnO powder obtained in step (1) is coated on a PTFE membrane, which is then placed in an oven (50° C.) and vacuum-dried for 5 hours to form a photocatalyst color-changing layer. A SiO2 protective layer is then covered on the photocatalyst color-changing layer using a sol-gel method to obtain the Au / ZnO photochromic laser printing film.

[0151] The actual pictures of Au / ZnO powder before and after light exposure in Example 13 are as follows: Figure 16 As shown in FIG, the prepared Au / ZnO powder is light grayish white. After being irradiated with 365 nm ultraviolet light for 20 min, the powder color turns grayish purple.

[0152] The TEM image and mapping element distribution diagram of the Au / ZnO powder after illumination in Example 13 are as follows: Figure 17 As shown in the figure, new particulate matter appears on the base material ZnO. From the mapping element distribution diagram, it can be seen that the newly generated substance is mainly composed of the element Ag. Based on its brown appearance, it is speculated that silver nanoparticles are formed.

[0153] The actual pictures of the Au / ZnO photochromic laser printing film prepared in Example 13 before and after illumination are as follows: Figure 18 As shown in FIG, the color of the Au / ZnO photochromic laser printed film before exposure to light is light gray, and the color turns pink after exposure to 365 nm ultraviolet light for 20 minutes.

[0154] Example 14

[0155] A method for preparing an Ag / ZnO photochromic laser printing film comprises the following steps:

[0156] (1) Prepare 100 mg / L silver nitrate solution with anhydrous ethanol as solvent, add 5 g ZnO powder with a particle size of 100 nm to 100 mL of silver nitrate solution, and the mass ratio of silver ion to ZnO is 0.0013. After stirring evenly, stand in the dark and open air for adsorption to allow the solvent to evaporate naturally to obtain Ag / ZnO powder.

[0157] (2) The Ag / ZnO powder obtained in step (1) is coated on a PTFE membrane, which is then placed in an oven (40° C.) and vacuum-dried for 6 hours to form a photocatalyst color-changing layer. A SiO2 protective layer is then covered on the photocatalyst color-changing layer using a sol-gel method to obtain the Ag / ZnO photochromic laser printing film.

[0158] The actual picture of Ag / ZnO powder before and after light exposure in Example 14 is as follows: Figure 19 As shown in FIG, the prepared Ag / ZnO powder is light gray. After being irradiated with 365 nm ultraviolet light for 20 min, the powder color turns yellow.

[0159] The actual pictures of the Ag / ZnO photochromic laser printing film prepared in Example 14 before and after illumination are as follows: Figure 20 As shown, the color of the Ag / ZnO photochromic laser printed film before exposure to light is light gray, and the color turns yellow after exposure to 365 nm ultraviolet light for 20 minutes.

[0160] Example 15

[0161] A method for preparing a Cu / ZnO photochromic laser printing film comprises the following steps:

[0162] (1) Prepare 100 mg / L copper nitrate solution with anhydrous ethanol as solvent, add 5 g ZnO powder with a particle size of 100 nm to 100 mL copper nitrate solution, and the mass ratio of copper ion to ZnO is 0.0007. After stirring evenly, stand in the dark and open air for adsorption to allow the solvent to evaporate naturally to obtain Cu / ZnO powder.

[0163] (2) The Cu / ZnO powder obtained in step (1) is coated on a PTFE membrane, which is then placed in an oven (60° C.) and vacuum-dried for 4 hours to form a photocatalyst color-changing layer. A SiO2 protective layer is then covered on the photocatalyst color-changing layer using a sol-gel method to obtain the Cu / ZnO photochromic laser printing film.

[0164] The actual picture of Cu / ZnO powder before and after light exposure in Example 15 is as follows: Figure 21 As shown, the prepared Cu / ZnO powder is white. After being irradiated with 365 nm ultraviolet light for 20 min, the powder color turns gray.

[0165] The actual pictures of the Cu / ZnO photochromic laser printing film prepared in Example 15 before and after illumination are as follows: Figure 22 As shown, the color of the Cu / ZnO photochromic laser printed film before exposure to light is white, and the color turns to gray after exposure to 365 nm ultraviolet light for 20 minutes.

[0166] Example 16

[0167] A method for preparing a Fe / ZnO photochromic laser printing film comprises the following steps:

[0168] (1) Prepare 100 mg / L ferric nitrate solution with anhydrous ethanol as solvent, add 5 g ZnO powder with a particle size of 100 nm to 100 mL ferric nitrate solution, and the mass ratio of iron ion to ZnO is 0.00046. After stirring evenly, stand in the dark and open air for adsorption to allow the solvent to evaporate naturally to obtain Fe / ZnO powder.

[0169] (2) The Fe / ZnO powder obtained in step (1) is coated on a PTFE membrane, which is then placed in an oven (50° C.) and vacuum-dried for 5 hours to form a photocatalyst color-changing layer. A SiO2 protective layer is then covered on the photocatalyst color-changing layer using a sol-gel method to obtain the Fe / ZnO photochromic laser printing film.

[0170] The actual pictures of Fe / ZnO powder before and after light irradiation in Example 16 are as follows: Figure 23 As shown, the prepared Fe / ZnO powder is white. After being irradiated with 365 nm ultraviolet light for 20 min, the powder color turns yellow.

[0171] The actual pictures of the Fe / ZnO photochromic laser printing film prepared in Example 16 before and after illumination are as follows: Figure 24 As shown, the color of the Fe / ZnO photochromic laser printed film before exposure to light is white, and the color turns yellow after exposure to 365 nm ultraviolet light for 20 minutes.

[0172] Example 17

[0173] Prepare 500 mg / L chloroauric acid solution with anhydrous ethanol as solvent. Add 5 g of titanium dioxide powder (P25) with a particle size of 25 nm to 100 mL of chloroauric acid solution. The mass ratio of gold ions to P25 is 0.0058. After stirring evenly, the obtained P25 mixed solution is irradiated with 365 nm ultraviolet light (with an illumination intensity of 50 mW·cm -2 ) irradiation, such as Figure 25 As shown, with the passage of illumination time (0 min, 1 min, 2 min, 5 min), the color of the solid powder in the solution changed from white to light purple and then to dark purple.

[0174] Comparative Example 1

[0175] 5 g of titanium dioxide powder (P25, white in color) was added to 25 mL of anhydrous ethanol and stirred evenly. The mixture was then left to stand in an open place away from light for adsorption to allow the solvent to evaporate naturally, thereby obtaining treated titanium dioxide powder.

[0176] The TEM image and mapping element distribution diagram of the titanium dioxide powder treated in Comparative Example 1 after illumination are as follows: Figure 26 As shown, the titanium dioxide powder is nanoparticles with no obvious accumulation. -2 ) After irradiation for 20 minutes, the color of titanium dioxide powder did not change.

[0177] Comparative Example 2

[0178] 5 g of ZnO (white in color, with a particle size of 200 nm) was added to 25 mL of anhydrous ethanol and stirred evenly. The mixture was then left to stand in an open place away from light for adsorption, and the solvent was naturally evaporated to obtain treated ZnO powder.

[0179] The TEM image and mapping element distribution diagram of the ZnO powder after treatment in Comparative Example 2 are as follows: Figure 27 As shown in the figure, ZnO powder presents cubic nanoparticles without obvious accumulation. -2 ) After irradiation for 20 minutes, the color of ZnO powder did not change.

[0180] Comparative Example 3

[0181] Prepare 500 mg / L chloroauric acid solution with anhydrous ethanol as solvent. Add 5 g of SnO powder with a particle size of 60 nm to 100 mL of chloroauric acid solution. The mass ratio of gold ions to SnO is 0.0058. After stirring evenly, the obtained SnO mixed solution is irradiated with 365 nm ultraviolet light (with an illumination intensity of 50 mW·cm -2 ) irradiation, such as Figure 28 As shown in the figure, with the passage of illumination time (0 min, 1 min, 2 min, 5 min), the color of the solid powder in the solution did not change significantly.

[0182] Test Example 1

[0183] The heat resistance of the Au / P25 photochromic laser printing film prepared in Example 1 was tested by exposing it to 365 nm ultraviolet light (with an illumination intensity of 50 mW·cm -2 ) After irradiation for 20 minutes, the Au / P25 photochromic laser printed film prepared in Example 1 was placed in an 80°C oven for 5 days and then taken out to test its weight and color change. Figure 29As shown, its quality and color have not changed.

[0184] Test Example 2

[0185] The humidity resistance of the Au / P25 photochromic laser printing film prepared in Example 1 was tested by exposing it to 365 nm ultraviolet light (with an illumination intensity of 50 mW·cm -2 ) After irradiation for 20 minutes, the Au / P25 photochromic laser printing film prepared in Example 1 was immersed in water and its color change was observed. Figure 30 As shown, the color of the Au / P25 photochromic laser printing film prepared in Example 1 can be preserved for a long time in aqueous solution, indicating that it has good moisture resistance.

[0186] Test Example 3

[0187] The acid resistance of Au / P25 powder in Example 1 was tested by irradiating the powder with 365 nm ultraviolet light (with an illumination intensity of 50 mW·cm -2 ) After irradiation for 20 minutes, the Au / P25 powder in Example 1 was immersed in acidic water with pH=3 and its color change was observed. Figure 31 As shown, the color of the Au / P25 powder in Example 1 after illumination can be preserved for a long time in an acidic aqueous solution, and the color does not deteriorate after 5 days, indicating that the color-changed material has good acid resistance.

[0188] Test Example 4

[0189] The humidity resistance of Au / P25 powder in Example 1 was tested by exposing it to 365 nm ultraviolet light (with an illumination intensity of 50 mW·cm -2 ) After irradiation for 20 minutes, the Au / P25 powder in Example 1 was immersed in neutral water with pH = 7 and its color change was observed. Figure 32 As shown, the color of the Au / P25 powder in Example 1 after illumination can be preserved for a long time in a neutral aqueous solution, and the color does not deteriorate after 5 days, indicating that the material has good stability after color change.

[0190] Test Example 5

[0191] The alkali resistance of the Au / P25 powder in Example 1 was tested by exposing it to a 365 nm ultraviolet light (with an illumination intensity of 50 mW·cm -2 ) After irradiation for 20 minutes, the Au / P25 powder in Example 1 was immersed in alkaline water with a pH of 13 and its color change was observed. Figure 33 As shown, the color of the Au / P25 powder in Example 1 after illumination can be preserved for a long time in an alkaline aqueous solution, indicating that the material has good alkali resistance after color change.

[0192] Test Example 6

[0193] The acid resistance of the Ag / P60 powder in Example 8 was tested by exposing it to a 365 nm ultraviolet light (with an illumination intensity of 50 mW·cm -2 ) After irradiation for 20 minutes, the Ag / P60 powder in Example 8 was immersed in acidic water with pH=3 and its color change was observed. Figure 34 As shown, the color of the Ag / P60 powder in Example 8 after illumination can be preserved for a long time in an acidic aqueous solution, indicating that the material has good acid resistance after color change.

[0194] Test Example 7

[0195] The humidity resistance of the Ag / P25 powder in Example 6 was tested by exposing it to 365 nm ultraviolet light (with an illumination intensity of 50 mW·cm -2 ) After irradiation for 20 minutes, the Ag / P25 powder in Example 6 was immersed in neutral water with a pH of 7 and its color change was observed. Figure 35 As shown, the color of the Ag / P25 powder in Example 6 after illumination can be preserved for a long time in a neutral aqueous solution, indicating that the material has good alkali resistance after color change.

[0196] Test Example 8

[0197] The alkali resistance of the Ag / P25 powder in Example 10 was tested by exposing it to a 365 nm ultraviolet light (with an illumination intensity of 50 mW·cm -2 ) After irradiation for 20 minutes, the Ag / P25 powder of Example 10 was immersed in alkaline water with pH=13 and its color change was observed. Figure 36 As shown, the color of the Ag / P25 powder in Example 10 after illumination can be preserved for a long time in an alkaline aqueous solution, indicating that the material has good alkali resistance after color change.

[0198] Obviously, the above embodiments of the present invention are merely examples for the purpose of clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Those skilled in the art will appreciate that other variations or modifications may be made based on the above description. It is not necessary and impossible to enumerate all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the claims of the present invention.

Claims

1. A photochromic laser printing film, characterized in that: The photochromic laser printing film consists of a substrate layer, a photocatalytic color-changing layer and a protective layer. The material of the photocatalytic color-changing layer includes a photocatalyst and reducible metal ions, and the color of the metal ions changes before and after reduction. The photocatalyst is titanium dioxide nanoparticles and / or zinc oxide nanoparticles.

2. The photochromic laser printing film according to claim 1, characterized in that: The substrate layer is a transparent or translucent polymer film, and the material of the polymer film is selected from one or more of polytetrafluoroethylene, polyethylene terephthalate, polyvinylidene fluoride and polycarbonate.

3. The photochromic laser printing film according to claim 1, characterized in that: The particle size of the photocatalyst is 20-500 nm.

4. The photochromic laser printing film according to claim 1, characterized in that: The metal ion that can be reduced is Ag + 、Cu 2+ 、Au 3+ or Fe 3+ .

5. The photochromic laser printing film according to claim 1, characterized in that: The material of the protective layer is SiO2 and / or Al2O3.

6. A method for preparing the photochromic laser printing film according to any one of claims 1 to 5, characterized in that: The following steps are involved: (1) uniformly mixing a photocatalyst with a reducible metal ion solution, and obtaining a photocatalytic color-changing layer material after static adsorption under light-proof conditions; (2) coating the photocatalytic color-changing layer material obtained in step (1) on the substrate layer, forming a photocatalytic color-changing layer after drying, and preparing a protective layer on the photocatalytic color-changing layer to obtain the photochromic laser printing film.

7. The preparation method according to claim 6, characterized in that In step (1), the mass ratio of the metal ions in the reducible metal ion solution to the photocatalyst is: <m 金属离子 :m 光催化剂 ≤1.

8. Use of the photochromic laser printing film according to any one of claims 1 to 5 in the field of laser printing.

9. The use according to claim 8, characterized in that The method for using the photochromic laser printing film for laser printing comprises the following steps: placing the photochromic laser printing film under laser irradiation to trigger a photocatalytic reduction reaction to form an irreversible color pattern.

10. The use according to claim 9, characterized in that The wavelength of the laser is 200-420 nm.

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