A multilayer optically variable ultraviolet fluorescent anti-counterfeiting film and its preparation method

Abstract

This invention relates to the field of anti-counterfeiting film preparation technology, specifically disclosing a multilayer photochromic ultraviolet fluorescent anti-counterfeiting film and its preparation method. The multilayer photochromic ultraviolet fluorescent anti-counterfeiting film comprises a thin film substrate layer, a first photochromic layer, and a second photochromic layer; wherein the first and second photochromic layers are located on opposite sides of the thin film substrate layer; the first and second photochromic layers respectively contain rhodamine B, sodium fluorescein, and europium oxide. This ultraviolet fluorescent anti-counterfeiting film, by having a first and second photochromic layer containing photochromic materials such as rhodamine B, sodium fluorescein, and europium oxide on both sides of the thin film substrate layer, results in a multilayer photochromic ultraviolet fluorescent anti-counterfeiting film with a short ultraviolet irradiation color-changing reaction time; it has broad application prospects.

Description

Technical Field

[0001] This invention relates to the field of anti-counterfeiting film preparation technology, specifically to an ultraviolet fluorescent anti-counterfeiting film based on multilayer optical variation and its preparation method. Background Technology

[0002] With the rapid development of the commodity economy and the deep integration of global trade, anti-counterfeiting technology has become an important means to ensure product safety, maintain brand value, and combat counterfeiting. Traditional anti-counterfeiting technologies, such as holographic images and laser engraving, have gradually revealed their shortcomings, such as ease of replication and high barriers to identification. To address this challenge, developing new anti-counterfeiting materials with high security, ease of identification, and difficulty in replication has become a current research hotspot. For example, Chinese invention patent CN117510930A discloses a method for preparing and applying a flexible ultraviolet fluorescent anti-counterfeiting composite film. The preparation steps include: synthesizing a precursor; preparing hexagonal boron nitride phosphor by high-temperature pyrolysis, washing, and drying of the precursor; and combining the hexagonal boron nitride phosphor with a polymer to obtain a flexible ultraviolet fluorescent anti-counterfeiting composite film. The flexible ultraviolet fluorescent anti-counterfeiting composite film obtained by this invention has good chemical stability, flexibility, extensibility, concealment, and adhesion. It can be well hidden under sunlight, but the pattern can be brightly displayed under ultraviolet light. It can be applied to optical anti-counterfeiting and optical information encryption, and has broad application prospects.

[0003] The inventors discovered in their research that although the ultraviolet fluorescent anti-counterfeiting film prepared by the existing technology can achieve good luminescence under ultraviolet light, its ultraviolet irradiation color-changing reaction time is long and its sensitivity is not high, which needs to be further improved. Summary of the Invention

[0004] In order to overcome at least one of the technical problems existing in the prior art, the present invention first provides a multilayer optically variable ultraviolet fluorescent anti-counterfeiting film and its preparation method.

[0005] The present invention first provides an ultraviolet fluorescent anti-counterfeiting film based on multi-layer optical variable, which includes a thin film substrate layer, a first optical variable layer and a second optical variable layer; wherein the first optical variable layer and the second optical variable layer are respectively located on both sides of the thin film substrate layer;

[0006] The first and second optically variable layers respectively contain rhodamine B, sodium fluorescein, and europium oxide.

[0007] This invention provides a novel multilayer optically variable ultraviolet fluorescent anti-counterfeiting film. This ultraviolet fluorescent anti-counterfeiting film has a first optically variable layer and a second optically variable layer containing optically variable materials such as Rhodamine B, sodium fluorescein, and europium oxide on both sides of the film substrate layer, so that the prepared multilayer optically variable ultraviolet fluorescent anti-counterfeiting film has a shorter ultraviolet irradiation color-changing reaction time.

[0008] Preferably, the weight ratio of Rhodamine B, sodium fluorescein, and europium oxide in the first and second photochromic layers is 3-6:3-6:1-3.

[0009] Most preferably, the weight ratio of Rhodamine B, sodium fluorescein, and europium oxide in the first and second optically variable layers is 5:5:2.

[0010] Preferably, the thin film substrate layer is prepared from the following components in parts by weight: 80-100 parts of polyvinyl chloride resin; 10-20 parts of mica powder.

[0011] Preferably, the thin film substrate layer is prepared from the following components in parts by weight: 85 parts of polyvinyl chloride resin and 15 parts of mica powder.

[0012] Preferably, the mica powder is modified mica powder;

[0013] The modified mica powder is prepared by the following method:

[0014] (1) Take mica powder, soak it in acid, and after soaking, take out the mica powder and wash it until it is neutral to obtain acid-treated mica powder.

[0015] (2) Add acid-treated mica powder to water and disperse it evenly to obtain an acid-treated mica powder dispersion.

[0016] (3) Add hafnium tetrachloride and yttrium chloride to the acid-treated mica powder dispersion and stir until uniform. Then add sodium hydroxide and stir for 3-5 hours. After stirring, separate the solid and liquid to obtain a solid mixture.

[0017] (4) The solid mixture is roasted at 800-1000℃ for 2-4 hours; after roasting, the roasted solid is taken to obtain the modified mica powder.

[0018] In further research, the inventors surprisingly discovered that adding modified mica powder prepared by the above-mentioned method of the present invention to the thin film substrate layer of the multilayer optically variable ultraviolet fluorescent anti-counterfeiting film can significantly shorten the ultraviolet irradiation color-changing reaction time of the multilayer optically variable ultraviolet fluorescent anti-counterfeiting film of the present invention compared with adding unmodified mica powder.

[0019] The inventors also discovered in their research that in step (3) of modifying mica powder, hafnium tetrachloride and yttrium chloride must be added simultaneously to stir and modify the mica powder to obtain modified mica powder. Compared with adding unmodified mica powder, this significantly shortens the ultraviolet irradiation color-changing reaction time of the ultraviolet fluorescent anti-counterfeiting film based on multi-layer optical variation of the present invention. However, in step (3) of modifying mica powder, adding only hafnium tetrachloride or only yttrium chloride to stir and modify the mica powder does not significantly shorten the ultraviolet irradiation color-changing reaction time of the ultraviolet fluorescent anti-counterfeiting film based on multi-layer optical variation of the present invention compared with adding unmodified mica powder.

[0020] Preferably, in step (2), the weight ratio of acid-treated mica powder to water is 1:5 to 15;

[0021] Most preferably, in step (2), the weight ratio of acid-treated mica powder to water is 1:9.

[0022] Preferably, in step (3), the weight ratio of the acid-treated mica powder dispersion to hafnium tetrachloride, yttrium chloride, and sodium hydroxide is 10:0.1~0.2:0.08~0.12:0.1~1.5;

[0023] Most preferably, in step (3), the weight ratio of the acid-treated mica powder dispersion to hafnium tetrachloride, yttrium chloride and sodium hydroxide is 10:0.16:0.1:0.14.

[0024] Preferably, the method for preparing the modified mica powder further includes the following steps:

[0025] The calcined solid is placed in the modification liquid, stirred for 1-3 hours, the solid is separated, and dried to obtain the modified mica powder.

[0026] The modified liquid refers to an aqueous solution containing cocamidopropylamine oxide and sodium dodecyl diphenyl ether disulfonate; wherein the weight ratio of cocamidopropylamine oxide, sodium dodecyl diphenyl ether disulfonate and water is 10-20:5-10:100.

[0027] Most preferably, the weight ratio of cocamidopropylamine oxide, sodium dodecyl diphenyl ether disulfonate, and water is 13:7:100.

[0028] Further research by the inventors revealed that, in the preparation of modified mica powder, the modified mica powder obtained by further modifying the calcined solid in an aqueous solution containing both cocamidopropylamine oxide and sodium dodecyl diphenyl ether disulfonate can significantly shorten the ultraviolet irradiation color-changing reaction time of the ultraviolet fluorescent anti-counterfeiting film based on multilayer optical change according to this invention.

[0029] The inventors also discovered that, in the preparation process of modified mica powder, only by further modifying the calcined solid in an aqueous solution containing both cocamidopropylamine oxide and sodium dodecyl diphenyl ether disulfonate can the ultraviolet irradiation color-changing reaction time of the ultraviolet fluorescent anti-counterfeiting film based on multilayer optical variable of the present invention be significantly shortened. However, the modified mica powder obtained by modifying it in an aqueous solution containing only cocamidopropylamine oxide or only sodium dodecyl diphenyl ether disulfonate cannot significantly shorten the ultraviolet irradiation color-changing reaction time of the ultraviolet fluorescent anti-counterfeiting film based on multilayer optical variable of the present invention.

[0030] The present invention also provides a method for preparing the above-mentioned ultraviolet fluorescent anti-counterfeiting film based on multilayer optical variation, characterized by comprising the following steps:

[0031] (1) The raw material of the substrate layer, polyvinyl chloride resin, is mixed with mica powder to obtain a mixture. The mixture is then put into a twin-screw extruder for melt extrusion and cooled and shaped by a cooling roller to form a thin film substrate layer.

[0032] (2) Spray a dispersion containing Rhodamine B, sodium fluorescein and europium oxide onto both sides of the film substrate layer with a spray gun. After drying, a multilayer optical variable ultraviolet fluorescent anti-counterfeiting film containing a first optical variable layer and a second optical variable layer is obtained.

[0033] Preferably, the dispersion containing rhodamine B, sodium fluorescein, and europium oxide refers to an ethanol dispersion containing rhodamine B, sodium fluorescein, and europium oxide; wherein the weight ratio of rhodamine B, sodium fluorescein, europium oxide, and ethanol is 3-6:3-6:1-3:30-50.

[0034] The most preferred embodiment is that the weight ratio of Rhodamine B, sodium fluorescein, europium oxide and ethanol is 5:5:2:40.

[0035] Preferably, the ethanol refers to an aqueous solution of ethanol with a volume fraction of 95%.

[0036] Preferably, the thickness of the thin film substrate layer is 50–100 μm; the thicknesses of the first optical variable layer and the second optical variable layer are 5–30 μm, respectively.

[0037] Most preferably, the thickness of the thin film substrate layer is 80 μm; the thicknesses of the first optical variable layer and the second optical variable layer are 10 μm, respectively.

[0038] Beneficial effects: This invention provides a novel multilayer optically variable ultraviolet fluorescent anti-counterfeiting film. This ultraviolet fluorescent anti-counterfeiting film has a first optically variable layer and a second optically variable layer containing optically variable materials such as Rhodamine B, sodium fluorescein, and europium oxide on both sides of the film substrate layer, so that the prepared multilayer optically variable ultraviolet fluorescent anti-counterfeiting film has a shorter ultraviolet irradiation color-changing reaction time; it has broad application prospects. Detailed Implementation

[0039] The present invention will be further explained below with reference to specific embodiments, but the embodiments do not limit the present invention in any way.

[0040] The polyvinyl chloride resin used in the following examples is SG-8 polyvinyl chloride resin from Xinjiang Tianye; all other raw materials whose sources are not specified are conventional raw materials that can be purchased by those skilled in the art through conventional channels.

[0041] Example 1: Preparation of a multilayer optically variable ultraviolet fluorescent anti-counterfeiting film

[0042] The ultraviolet fluorescent anti-counterfeiting film based on multi-layer optical variable light includes a thin film substrate layer, a first optical variable layer, and a second optical variable layer; wherein the first optical variable layer and the second optical variable layer are located on both sides of the thin film substrate layer; the thickness of the thin film substrate layer is 80 μm; and the thicknesses of the first optical variable layer and the second optical variable layer are 10 μm each.

[0043] The thin film substrate layer is prepared from the following components in parts by weight: 85 parts polyvinyl chloride resin; 15 parts mica powder;

[0044] The method for preparing the ultraviolet fluorescent anti-counterfeiting film based on multilayer optical variation includes the following steps:

[0045] (1) The raw material polyvinyl chloride resin and mica powder of the film substrate layer are mixed evenly according to the above weight parts to obtain a mixture. The mixture is put into a twin screw extruder for melt extrusion, and then cooled and shaped by a cooling roller to form a film substrate layer with a thickness of 80μm.

[0046] (2) Spray a dispersion containing Rhodamine B, sodium fluorescein and europium oxide onto both sides of the film substrate layer with a spray gun. After drying, a multilayer optical variable ultraviolet fluorescent anti-counterfeiting film containing a first optical variable layer (10 μm thick) and a second optical variable layer (10 μm thick) is obtained.

[0047] The dispersion containing rhodamine B, sodium fluorescein and europium oxide mentioned in step (2) refers to an ethanol dispersion containing rhodamine B, sodium fluorescein and europium oxide; wherein, the weight ratio of rhodamine B, sodium fluorescein, europium oxide and ethanol is 5:5:2:40; the ethanol refers to an aqueous solution of ethanol with a volume fraction of 95%.

[0048] Example 2: Preparation of a multilayer optically variable ultraviolet fluorescent anti-counterfeiting film

[0049] The difference between Example 2 and Example 1 is that the mica powder in the film substrate layer is modified mica powder; otherwise, they are the same as in Example 1.

[0050] The modified mica powder is prepared by the following method:

[0051] (1) Take mica powder and soak it in 5 times its weight of acid. After soaking, take out the mica powder and wash it until it is neutral to obtain acid-treated mica powder. The acid mentioned refers to an aqueous solution of sulfuric acid with a mass fraction of 80%.

[0052] (2) Add acid-treated mica powder to water and disperse it evenly to obtain an acid-treated mica powder dispersion; wherein the weight ratio of acid-treated mica powder to water is 1:9.

[0053] (3) Add hafnium tetrachloride and yttrium chloride to the acid-treated mica powder dispersion and stir until uniform. Then add sodium hydroxide and stir for 4 hours. After stirring, separate the solid and liquid to obtain a solid mixture. The weight ratio of the acid-treated mica powder dispersion to hafnium tetrachloride, yttrium chloride and sodium hydroxide is 10:0.16:0.1:0.14.

[0054] (4) The solid mixture is roasted at 95°C for 3 hours; after roasting, the roasted solid is taken to obtain the modified mica powder.

[0055] Example 3: Preparation of a multilayer optically variable ultraviolet fluorescent anti-counterfeiting film

[0056] The difference between Example 3 and Example 2 lies in the preparation method of the modified mica powder in the membrane substrate layer.

[0057] The modified mica powder is prepared by the following method:

[0058] (1) Take mica powder and soak it in 5 times its weight of acid. After soaking, take out the mica powder and wash it until it is neutral to obtain acid-treated mica powder. The acid mentioned refers to an aqueous solution of sulfuric acid with a mass fraction of 80%.

[0059] (2) Add acid-treated mica powder to water and disperse it evenly to obtain an acid-treated mica powder dispersion; wherein the weight ratio of acid-treated mica powder to water is 1:9.

[0060] (3) Add hafnium tetrachloride and yttrium chloride to the acid-treated mica powder dispersion and stir until uniform. Then add sodium hydroxide and stir for 4 hours. After stirring, separate the solid and liquid to obtain a solid mixture. The weight ratio of the acid-treated mica powder dispersion to hafnium tetrachloride, yttrium chloride and sodium hydroxide is 10:0.16:0.1:0.14.

[0061] (4) The solid mixture was calcined at 95°C for 3 hours; after calcination, a calcined solid was obtained.

[0062] (5) The calcined solid is placed in the modification liquid, stirred for 2 hours, the solid is separated, and dried to obtain the modified mica powder.

[0063] The modified liquid mentioned in step (5) refers to an aqueous solution containing cocamidopropylamine oxide and sodium dodecyl diphenyl ether disulfonate; wherein the weight ratio of cocamidopropylamine oxide, sodium dodecyl diphenyl ether disulfonate and water is 13:7:100.

[0064] Comparative Example 1: Preparation of a multilayer optically variable ultraviolet fluorescent anti-counterfeiting film

[0065] The difference between Comparative Example 1 and Example 2 is that the mica powder in the film substrate layer is modified mica powder; both are the same as in Example 1.

[0066] The modified mica powder is prepared by the following method:

[0067] (1) Take mica powder and soak it in 5 times its weight of acid. After soaking, take out the mica powder and wash it until it is neutral to obtain acid-treated mica powder. The acid mentioned refers to an aqueous solution of sulfuric acid with a mass fraction of 80%.

[0068] (2) Add acid-treated mica powder to water and disperse it evenly to obtain an acid-treated mica powder dispersion; wherein the weight ratio of acid-treated mica powder to water is 1:9.

[0069] (3) Add hafnium tetrachloride to the acid-treated mica powder dispersion and stir until uniform. Then add sodium hydroxide and stir for 4 hours. After stirring, separate the solid and liquid to obtain a solid mixture. The weight ratio of the acid-treated mica powder dispersion to hafnium tetrachloride and sodium hydroxide is 10:0.26:0.14.

[0070] (4) The solid mixture is roasted at 95°C for 3 hours; after roasting, the roasted solid is taken to obtain the modified mica powder.

[0071] Comparative Example 2: Preparation of a multilayer optically variable ultraviolet fluorescent anti-counterfeiting film

[0072] The difference between Comparative Example 2 and Example 2 is that the mica powder in the film substrate layer is modified mica powder; both are the same as in Example 1.

[0073] The modified mica powder is prepared by the following method:

[0074] (1) Take mica powder and soak it in 5 times its weight of acid. After soaking, take out the mica powder and wash it until it is neutral to obtain acid-treated mica powder. The acid mentioned refers to an aqueous solution of sulfuric acid with a mass fraction of 80%.

[0075] (2) Add acid-treated mica powder to water and disperse it evenly to obtain an acid-treated mica powder dispersion; wherein the weight ratio of acid-treated mica powder to water is 1:9.

[0076] (3) Add yttrium chloride to the acid-treated mica powder dispersion and stir until uniform. Then add sodium hydroxide and stir for 4 hours. After stirring, separate the solid and liquid to obtain a solid mixture. The weight ratio of the acid-treated mica powder dispersion to yttrium chloride and sodium hydroxide is 10:0.26:0.14.

[0077] (4) The solid mixture is roasted at 95°C for 3 hours; after roasting, the roasted solid is taken to obtain the modified mica powder.

[0078] Comparative Example 3: Preparation of a multilayer optically variable ultraviolet fluorescent anti-counterfeiting film

[0079] The difference between Comparative Example 3 and Example 3 lies in the preparation method of the modified mica powder in the membrane substrate layer.

[0080] The modified mica powder is prepared by the following method:

[0081] (1) Take mica powder and soak it in 5 times its weight of acid. After soaking, take out the mica powder and wash it until it is neutral to obtain acid-treated mica powder. The acid mentioned refers to an aqueous solution of sulfuric acid with a mass fraction of 80%.

[0082] (2) Add acid-treated mica powder to water and disperse it evenly to obtain an acid-treated mica powder dispersion; wherein the weight ratio of acid-treated mica powder to water is 1:9.

[0083] (3) Add hafnium tetrachloride and yttrium chloride to the acid-treated mica powder dispersion and stir until uniform. Then add sodium hydroxide and stir for 4 hours. After stirring, separate the solid and liquid to obtain a solid mixture. The weight ratio of the acid-treated mica powder dispersion to hafnium tetrachloride, yttrium chloride and sodium hydroxide is 10:0.16:0.1:0.14.

[0084] (4) The solid mixture was calcined at 95°C for 3 hours; after calcination, a calcined solid was obtained.

[0085] (5) The calcined solid is placed in the modification liquid, stirred for 2 hours, the solid is separated, and dried to obtain the modified mica powder.

[0086] The modified liquid mentioned in step (5) refers to an aqueous solution containing cocamidopropylamine oxide; wherein the weight ratio of cocamidopropylamine oxide to water is 20:100.

[0087] Comparative Example 4: Preparation of a multilayer optically variable ultraviolet fluorescent anti-counterfeiting film

[0088] The difference between Comparative Example 4 and Example 3 lies in the preparation method of the modified mica powder in the membrane substrate layer.

[0089] The modified mica powder is prepared by the following method:

[0090] (1) Take mica powder and soak it in 5 times its weight of acid. After soaking, take out the mica powder and wash it until it is neutral to obtain acid-treated mica powder. The acid mentioned refers to an aqueous solution of sulfuric acid with a mass fraction of 80%.

[0091] (2) Add acid-treated mica powder to water and disperse it evenly to obtain an acid-treated mica powder dispersion; wherein the weight ratio of acid-treated mica powder to water is 1:9.

[0092] (3) Add hafnium tetrachloride and yttrium chloride to the acid-treated mica powder dispersion and stir until uniform. Then add sodium hydroxide and stir for 4 hours. After stirring, separate the solid and liquid to obtain a solid mixture. The weight ratio of the acid-treated mica powder dispersion to hafnium tetrachloride, yttrium chloride and sodium hydroxide is 10:0.16:0.1:0.14.

[0093] (4) The solid mixture was calcined at 95°C for 3 hours; after calcination, a calcined solid was obtained.

[0094] (5) The calcined solid is placed in the modification liquid, stirred for 2 hours, the solid is separated, and dried to obtain the modified mica powder.

[0095] The modified liquid mentioned in step (5) refers to an aqueous solution containing sodium dodecyl diphenyl ether disulfonate; wherein the weight ratio of sodium dodecyl diphenyl ether disulfonate to water is 20:100.

[0096] Experimental Example 1

[0097] The ultraviolet fluorescent anti-counterfeiting films based on multilayer optical change prepared in Examples 1-3 and Comparative Examples 1-4 were placed in a test chamber and the ultraviolet irradiation color change reaction time was recorded under the light source of a sunlight simulator. The test results are shown in Table 1.

[0098]

[0099] As can be seen from the experimental results in Table 1, the ultraviolet fluorescent anti-counterfeiting film based on multilayer optical change prepared in Example 1 has an ultraviolet irradiation color-changing reaction time of 15.4 seconds, which shows good sensitivity.

[0100] As can be seen from the experimental results in Table 1, the UV-fluorescent anti-counterfeiting film based on multilayer optical variable prepared in Example 2 has a significantly shorter UV irradiation color-changing reaction time than the UV-fluorescent anti-counterfeiting film based on multilayer optical variable prepared in Example 1. This indicates that adding modified mica powder prepared by the method described in this invention to the thin film substrate layer of the UV-fluorescent anti-counterfeiting film based on multilayer optical variable can significantly shorten the UV irradiation color-changing reaction time of the UV-fluorescent anti-counterfeiting film based on multilayer optical variable of this invention compared to adding unmodified mica powder.

[0101] As can be seen from the experimental results in Table 1, the UV-induced color-changing reaction time of the UV-induced color-changing anti-counterfeiting films based on multi-layer optical variable prepared in Comparative Examples 1 and 2 is reduced compared with that of the UV-induced color-changing anti-counterfeiting film based on multi-layer optical variable prepared in Example 1, but the reduction is not significant. This indicates that in step (3) of modifying mica powder, hafnium tetrachloride and yttrium chloride must be added simultaneously to modify the mica powder. Compared with adding unmodified mica powder, this significantly shortens the UV-induced color-changing reaction time of the UV-induced color-changing anti-counterfeiting film based on multi-layer optical variable of the present invention. However, in step (3) of modifying mica powder, adding only hafnium tetrachloride or only yttrium chloride to modify the mica powder does not significantly shorten the UV-induced color-changing reaction time of the UV-induced color-changing anti-counterfeiting film based on multi-layer optical variable of the present invention compared with adding unmodified mica powder.

[0102] As can be seen from the experimental results in Table 1, the UV-fluorescent anti-counterfeiting film based on multilayer optical variable prepared in Example 3 has a significantly shorter UV irradiation color-changing reaction time than the UV-fluorescent anti-counterfeiting film based on multilayer optical variable prepared in Example 2. This indicates that, in the preparation process of modified mica powder, further modifying the calcined solid by placing it in an aqueous solution containing both cocamidopropylamine oxide and sodium dodecyl diphenyl ether disulfonate can significantly shorten the UV irradiation color-changing reaction time of the UV-fluorescent anti-counterfeiting film based on multilayer optical variable of the present invention.

[0103] As can be seen from the experimental results in Table 1, the UV-induced color-changing reaction time of the multilayer photochromic UV-fluorescent anti-counterfeiting films prepared in Comparative Examples 3 and 4, although reduced compared to the multilayer photochromic UV-fluorescent anti-counterfeiting film prepared in Example 2, is not significantly reduced. This indicates that in the preparation of modified mica powder, only by further modifying the calcined solid in an aqueous solution containing both cocamidopropylamine oxide and sodium dodecyl diphenyl ether disulfonate can the UV-induced color-changing reaction time of the multilayer photochromic UV-fluorescent anti-counterfeiting film of this invention be significantly shortened. However, the modified mica powder obtained by modifying it in an aqueous solution containing only cocamidopropylamine oxide or only sodium dodecyl diphenyl ether disulfonate cannot significantly shorten the UV-induced color-changing reaction time of the multilayer photochromic UV-fluorescent anti-counterfeiting film of this invention.

Claims

1. A multilayer optically variable ultraviolet fluorescent anti-counterfeiting film, characterized in that, It comprises a thin film substrate layer, a first optical variable layer, and a second optical variable layer; wherein the first optical variable layer and the second optical variable layer are located on both sides of the thin film substrate layer; The first and second optical variable layers respectively contain rhodamine B, sodium fluorescein, and europium oxide; The weight ratio of Rhodamine B, sodium fluorescein, and europium oxide in the first and second optical variable layers is 3~6:3~6:1~3; The thin film substrate layer is prepared from the following components in parts by weight: 80-100 parts of polyvinyl chloride resin; 10-20 parts of mica powder.

2. The ultraviolet fluorescent anti-counterfeiting film based on multilayer optical variable as described in claim 1, characterized in that, The first and second optically variable layers contain rhodamine B, sodium fluorescein, and europium oxide in a weight ratio of 5:5:

2.

3. The ultraviolet fluorescent anti-counterfeiting film based on multilayer optical variable as described in claim 1, characterized in that, The thin film substrate layer is prepared from the following components in parts by weight: 85 parts polyvinyl chloride resin; 15 parts mica powder.

4. The ultraviolet fluorescent anti-counterfeiting film based on multilayer optical variable as described in claim 1, characterized in that, The mica powder mentioned is modified mica powder; The modified mica powder is prepared by the following method: (1) Take mica powder, soak it in acid, and after soaking, take out the mica powder and wash it until it is neutral to obtain acid-treated mica powder. (2) Add acid-treated mica powder to water and disperse it evenly to obtain an acid-treated mica powder dispersion; (3) Add hafnium tetrachloride and yttrium chloride to the acid-treated mica powder dispersion and stir until uniform. Then add sodium hydroxide and stir for 3-5 hours. After stirring, separate the solid and liquid to obtain a solid mixture. (4) The solid mixture is calcined at 800~1000℃ for 2~4h; after calcination, the calcined solid is taken to obtain the modified mica powder.

5. The ultraviolet fluorescent anti-counterfeiting film based on multilayer optical variable as described in claim 4, characterized in that, In step (2), the weight ratio of acid-treated mica powder to water is 1:5~15.

6. The ultraviolet fluorescent anti-counterfeiting film based on multilayer optical variable as described in claim 4, characterized in that, In step (2), the weight ratio of acid-treated mica powder to water is 1:

9.

7. The ultraviolet fluorescent anti-counterfeiting film based on multilayer optical variable as described in claim 4, characterized in that, In step (3), the weight ratio of the acid-treated mica powder dispersion to hafnium tetrachloride, yttrium chloride and sodium hydroxide is 10:0.1~0.2:0.08~0.12:0.1~1.

5.

8. The ultraviolet fluorescent anti-counterfeiting film based on multilayer optical variable as described in claim 4, characterized in that, In step (3), the weight ratio of the acid-treated mica powder dispersion to hafnium tetrachloride, yttrium chloride and sodium hydroxide is 10:0.16:0.1:0.

14.

9. The method for preparing the multilayer optically variable ultraviolet fluorescent anti-counterfeiting film according to any one of claims 1 to 8, characterized in that, It includes the following steps: (1) The raw material polyvinyl chloride resin and mica powder of the substrate layer are mixed evenly to obtain a mixture. The mixture is put into a twin-screw extruder for melt extrusion and then cooled and shaped by a cooling roller to form a thin film substrate layer. (2) Spray a dispersion containing Rhodamine B, sodium fluorescein and europium oxide onto both sides of the film substrate layer with a spray gun. After drying, a multilayer optical variable ultraviolet fluorescent anti-counterfeiting film containing a first optical variable layer and a second optical variable layer is obtained.

10. The method for preparing the ultraviolet fluorescent anti-counterfeiting film based on multilayer optical variation as described in claim 9, characterized in that, The dispersion containing rhodamine B, sodium fluorescein and europium oxide mentioned in step (1) refers to an ethanol dispersion containing rhodamine B, sodium fluorescein and europium oxide; wherein the weight ratio of rhodamine B, sodium fluorescein, europium oxide and ethanol is 3~6:3~6:1~3:30~50.

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