Protective film for preventing infrared laser eavesdropping and electromagnetic information leakage

Abstract

The utility model provides a protective film for preventing infrared laser eavesdropping and electromagnetic information leakage. The protective film comprises a first infrared absorption layer, an electromagnetic shielding layer and a second infrared absorption layer. According to the utility model, the ITO material has better absorption capability for infrared light with the wavelength of more than 1200 nm, and the cesium tungsten bronze material has better absorption performance in a near-infrared region with the wavelength of 900-1200 nm than that of the ITO material, so that the near-infrared light can be well absorbed. The combination of the two plating layers can realize the infrared light exceeding rejection rate of 900-2500nm. An ITO and cesium tungsten bronze combined mode is adopted to improve the infrared absorption wavelength coverage range, meanwhile, permalloy has high infrared reflectivity, the permalloy coating is clamped between two infrared absorption materials, infrared reflected light on the surface of the permalloy can be greatly absorbed, the infrared reflectivity of the whole film is reduced, and the infrared absorption effect is improved. Therefore, the information leakage risk is reduced. The permalloy is adopted to provide current carriers, so that the high-frequency electromagnetic shielding effectiveness is improved.

Description

Technical Field

[0001] The utility model relates to the technical field of information security, in particular to a protective film that prevents infrared laser eavesdropping and electromagnetic information leakage. Background Art

[0002] With the development of information technology, infrared laser voice acquisition and information restoration through electromagnetic radiation signals have become important ways of obtaining information due to their advantages such as no implantation and low risk. Therefore, infrared laser prevention and detection and electromagnetic leakage protection have become new directions in optoelectronic information security.

[0003] At present, in order to effectively prevent information leakage, people have the following methods for electromagnetic protection: Metal plating method: such as the prior art with publication number cn202011364235.0, an electromagnetic shielding method, whose technical solution is to plate a metal conductive layer on a film. This method has a certain shielding effect on electromagnetic leakage, and as the metal plating layer thickens, its shielding effect is higher. At the same time, as the shielding metal layer thickens, the film itself reflects more light, resulting in relatively poor lighting performance. At the same time, ordinary metals have poor shielding performance for low-frequency electromagnetic signals. Metal grid method: such as the publication number CN201420372034.9, this method is that nano silver wires are distributed in the resin to form a conductive method similar to a metal grid, thereby reducing its conductive shielding performance.

[0004] For laser protection, there are mainly the following methods: For infrared laser blocking: such as the publication number cn201920263546.4, but this method only considers the blocking factor and has no effect on electromagnetic shielding. Laser intrusion detection: The detection method based on the "cat's eye" effect or short-wave infrared camera also needs to consider timeliness and other issues (such as the publication number: CN 204287480 U); However, in actual scenarios, the active laser voice search system is relatively cumbersome, and there is a possibility of missed reports and false alarms, so there is no special active protection against infrared laser voice leakage through windows.

[0005] With the comprehensive improvement of laser eavesdropping and electromagnetic information signal acquisition technology, it is increasingly important to develop new photoelectric information leakage prevention technologies with more comprehensive performance. The utility model provides a protective film against infrared laser eavesdropping and electromagnetic information leakage. Utility Model Content

[0006] The utility model aims to provide a protective film against infrared laser eavesdropping and electromagnetic information leakage, which has good protective effect against infrared information leakage and electromagnetic information leakage, relatively simple process, and high transmittance to visible light.

[0007] To achieve the above-mentioned purpose, the utility model proposes the following technical solution: a protective film against infrared laser eavesdropping and electromagnetic information leakage, comprising a first infrared absorption layer (1), an electromagnetic shielding layer (2) and a second infrared absorption layer (3) stacked in sequence.

[0008] Preferably, it further comprises a substrate (200), a mounting adhesive layer (210) and a protective layer (220), wherein the protective layer (220), the mounting adhesive layer (210), the second infrared absorption layer (3), the electromagnetic shielding layer (2), the first infrared absorption layer (1) and the substrate (200) are arranged in sequence from top to bottom.

[0009] Preferably, the material of the first infrared absorption layer (1) is ITO, and the thickness of the first infrared absorption layer (1) is between 0.01nm and 1000nm; the electromagnetic shielding layer (2) is Permalloy, and the thickness of the electromagnetic shielding layer (2) is between 0.01 and 100nm; the second infrared absorption layer (3) is cesium tungsten bronze, and the thickness of the second infrared absorption layer (3) is between 0.01nm and 1000nm.

[0010] Preferably, the material of the substrate (200) is PET, PVB or EVA plastic, and the thickness of the substrate (200) is 10 to 100 μm.

[0011] Preferably, the adhesive used for the mounting adhesive layer (210) is an acrylic adhesive, the material of the protective layer (220) is PET, PVB or EVA, and the thickness of the protective layer (220) is 10 to 50 μm.

[0012] Beneficial effects: The technical solution of this application has the following technical effects:

[0013] 1. For traditional protective films, this technical solution uses ITO materials to have good absorption capacity for infrared light above 1200nm, while the absorption performance of cesium tungsten bronze materials in the near-infrared region of 900-1200nm is much stronger than that of ITO, and can absorb near-infrared very well. Therefore, the combination of the two coatings can achieve a blocking rate of 900-2500nm infrared light.

[0014] 2. The combination of ITO and cesium tungsten bronze increases the infrared absorption wavelength coverage. At the same time, Permalloy has a strong reflectivity to infrared. Sandwiching the Permalloy coating between two infrared absorption materials can greatly absorb the infrared reflected light on the surface of the Permalloy, reducing the infrared reflectivity of the overall film, thereby reducing the risk of information leakage.

[0015] 3. By using Permalloy to provide carriers, while improving the high-frequency electromagnetic shielding effectiveness, because of the high magnetic permeability of Permalloy, it can effectively improve the low-frequency electromagnetic shielding effectiveness.

[0016] It should be appreciated that all combinations of the foregoing concepts, as well as additional concepts described in greater detail below, may be considered part of the inventive subject matter of the present disclosure, provided such concepts are not mutually inconsistent.

[0017] The foregoing and other aspects, embodiments and features of the present invention can be more fully understood from the following description in conjunction with the accompanying drawings. Other additional aspects of the present invention, such as the features and / or beneficial effects of the exemplary embodiments, will be apparent from the following description or learned from the practice of the specific embodiments according to the teachings of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The accompanying drawings are not intended to be drawn to scale. In the accompanying drawings, each identical or nearly identical component shown in various figures may be represented by the same reference numeral. For the sake of clarity, not every component is labeled in each figure. Now, embodiments of various aspects of the utility model will be described by way of example and with reference to the accompanying drawings, in which:

[0019] Figure 1 It is a schematic diagram of the structure of the utility model.

[0020] Figure 2 This is a schematic diagram of electromagnetic radiation attenuation of the utility model.

[0021] Figure 3 This is a schematic diagram of infrared blocking of the utility model.

[0022] Figure 4 It is a schematic diagram of the structure of the utility model (including a base 200 layer, a mounting adhesive layer 210 and a protective layer 220).

[0023] Figure 5 This is a schematic diagram of infrared blocking of cesium tungsten bronze of the utility model.

[0024] Figure 6 This is a schematic diagram of ITO infrared blocking of the utility model.

[0025] Figure 7 This is a schematic diagram of infrared blocking of the composite film of the utility model.

[0026] In the figure, the meaning of each figure mark is as follows: 1. first infrared absorption layer; 2. electromagnetic shielding layer; 3. second infrared absorption layer; 4. electromagnetic radiation signal; 5. first transmission signal; 6. second transmission signal; 7. third transmission signal; 8. first reflection signal; 9. second reflection signal; 10. third reflection signal; 11. infrared intrusion signal; 12. first transmitted light; 13. second transmitted light; 14. third transmitted light; 15. fourth transmitted light; 16. first reflected light; 17. second reflected light; 18. third reflected light. DETAILED DESCRIPTION

[0027] In order to better understand the technical content of the utility model, specific embodiments are cited and described as follows in conjunction with the accompanying drawings. In this disclosure, various aspects of the utility model are described with reference to the accompanying drawings, and many illustrative embodiments are shown in the accompanying drawings. The embodiments of the present disclosure are not necessarily defined to include all aspects of the utility model. It should be understood that the various concepts and embodiments introduced above, as well as those described in more detail below, can be implemented in any of many ways, because the concepts and embodiments disclosed in the utility model are not limited to any implementation method. In addition, some aspects disclosed in the utility model can be used alone, or used in any appropriate combination with other aspects disclosed in the utility model.

[0028] The utility model provides a protective film to prevent infrared laser eavesdropping and electromagnetic information leakage, such as Figure 1 and 3 As shown, it includes a protective layer 220, a mounting adhesive layer 210, a second infrared absorption layer 3, an electromagnetic shielding layer 2, a first infrared absorption layer 1 and a substrate 200 which are stacked in sequence from top to bottom. The utility model adopts a protective film formed by combining this specific layered structure to effectively prevent infrared laser information leakage and electromagnetic information leakage.

[0029] Specifically, the functions, compositions and forming methods of each layer structure in the present invention are as follows:

[0030] The substrate 200 is used to provide support for the protective film, and is preferably made of PET, PVB or EVA, and the thickness of the protective layer is 10 to 50 μm.

[0031] The material of the first infrared absorption layer 1 is ITO. The ITO layer has a shielding function. At the same time, ITO has high visible light transmittance, small attenuation between 900-1200nm, and strong infrared absorption above 1200nm. The ITO material includes indium oxide and tin oxide. The mass composition ratio of indium oxide and tin oxide is between 99:1 and 1:99. The thickness of the plated ITO layer is between 0.01nm-1000nm.

[0032] The electromagnetic shielding layer 2 is Permalloy. Conductive Permalloy can make the semiconductor material have a relatively sufficient contact with the metal, increase the contact area between ITO and cesium tungsten bronze, improve its conductivity, and also have a partial shielding function. The material forming the conductive Permalloy is an iron-nickel alloy with a thickness of 0.01 to 10 nm, which is mainly used to provide carriers. The coating layer can be a grid and a plane layer. Permalloy is plated on ITO by coating because Permalloy has good electrical and magnetic properties.

[0033] The second infrared absorption layer 3 is cesium tungsten bronze, wherein the cesium tungsten bronze layer is attached to the Permalloy by coating. The cesium tungsten bronze itself has better conductivity than ITO, and its near-infrared absorption of 900-1200nm is much better than ITO, so it can block near-infrared laser more comprehensively. The sputtering coating thickness of the Cs0.33WO3 layer is between 0.01nm and 1000nm.

[0034] The mounting adhesive layer 210 is an acrylic adhesive, which is coated on the cesium tungsten bronze layer and used to adhere the protective layer. The protective layer 220 is bonded to the mounting adhesive layer and used to protect the protective film. It can be made of PET plastic and has a thickness of 10-50 μm.

[0035] The electromagnetic and infrared protection principles of this utility model are:

[0036] In the absence of doping, the main material of the ITO film is in an ideal state of satisfying the chemical ratio, its valence band is full, the conduction band is empty, and the Fermi level is close to the center of the band gap. Because the band gap width of metal oxides is greater than the incident energy of visible light, metal oxides appear to be transparent in the visible light region.

[0037] The change of the optical bandgap width of ITO film is mainly manifested by the Burstein-Moss effect, in which the change of the optical bandgap width caused by the Burstein-Moss effect is greater than 0, and the increase is linearly related to the 2 / 3 power of the free carrier concentration n, as shown in the following formula:

[0038]

[0039] is the increase in the optical bandgap caused by the Burstein-Moss effect, and h is Planck's constant.

[0040] The optical properties of ITO transparent conductive film mainly depend on its optical constant refractive index n and extinction coefficient k. The square of the complex refractive index ni is defined as the complex dielectric constant εi. There is the following relationship between them:

[0041]

[0042] ε i =(n i ) 2 =ε1+iε2;

[0043]

[0044]

[0045] in:

[0046]

[0047]

[0048] ωp: plasma vibration frequency of free carriers, ε ∞ is the high-frequency dielectric constant, ω is the optical frequency, τ is a constant, c is the speed of light in a vacuum, and v is the speed of light in the medium.

[0049] For ITO film, when the incident wave frequency ω is equal to ωp, the real part of the complex dielectric constant is 0, and the performance of the material changes suddenly. It shows strong reflection for electromagnetic waves with frequencies lower than ωp, and transmission for electromagnetic waves with frequencies higher than ωp. Therefore, ωp determines the lower frequency limit of the transmission area of ​​the ITO film, which depends on the carrier concentration Nc. For practical ITO films, ωp and the corresponding plasma oscillation wavelength can be approximately expressed by the following two equations:

[0050]

[0051]

[0052] λ p is the plasma oscillation wavelength.

[0053] When ε∞ and m≈0.35m0m0 are both determined as the mass of free electrons, the lower limit of the transmission frequency of the ITO film increases with the increase of Nc; the extinction coefficient k that characterizes the spectral absorption increases with the increase of Nc, and decreases with the increase of the carrier mobility μc.

[0054] Considering the plasma oscillation frequency and optical bandgap width of the ITO film, it can be seen that with the increase of free carrier concentration Nc, the lower frequency limit plasma oscillation frequency and the upper frequency limit optical bandgap width of the ITO film transmission zone both increase, but the increase of the upper limit is much smaller than that of the lower limit, which makes the transmission zone of the ITO film narrower with Nc. Therefore, ITO absorbs relatively less below 1200nm and relatively more above 1200nm.

[0055] Cesium tungsten bronze has similar performance to ITO, but its conductivity is stronger and its λp is closer to visible light, which means that cesium tungsten bronze has better protection effect in near infrared 900-1200nm.

[0056] Electromagnetic shielding effectiveness principle:

[0057] The calculation formula is

[0058] SE = SER + SEA + SEM;

[0059] SER – reflection loss on the material surface;

[0060] SEA – absorption loss inside the material;

[0061] SEM - Multiple reflection losses within the material.

[0062] Among them, SER and SEA can be expressed by the following formulas:

[0063]

[0064]

[0065] Where f is the frequency of the incident electromagnetic wave, Hz;

[0066] σ r is the relative conductivity of the material, S / m;

[0067] μ r is the relative magnetic permeability of the material, H / m;

[0068] t is the thickness of the shielding material;

[0069] Since the magnetic permeability of Permalloy is relatively high, the use of metal-plated Permalloy in the shielding layer can effectively improve the low-frequency shielding effectiveness of the film.

[0070] Example

[0071] In addition, the applicant has tested the electromagnetic shielding performance and spectral transmittance performance of the protective film of the utility model, respectively. The electromagnetic shielding performance was tested using a window test method, and the spectral transmittance performance was tested using a spectrophotometer.

[0072] The present invention will be described in detail below with reference to specific embodiments.

[0073] Example 1

[0074] This embodiment discloses a protective film against infrared laser eavesdropping and electromagnetic information leakage, such as Figure 1 As shown, it includes a base layer, an ITO layer, a mounting adhesive layer and a protective layer stacked in sequence. The functions, compositions and molding methods of each layered structure are as follows: the base layer is used to provide support for the protective film, and is preferably made of PET plastic with a thickness of 50 μm.

[0075] The function of the ITO layer is to shield electromagnetic radiation and infrared absorption. The material forming the ITO layer is nano-metal oxide ultra-fine nanoparticles with a diameter of 20nm. The nano-metal oxide ultra-fine nanoparticles are mixed with indium oxide and tin oxide in a mass ratio of 95:5. The ITO layer is attached to the substrate layer by sputtering coating. The thickness of the nano-semiconductor layer is 40nm. The mounting adhesive layer is an acrylic adhesive, which is used to adhere the protective layer. The protective layer is used to protect the protective film and can be made of PET plastic with a thickness of 10μm.

[0076] Example 2

[0077] This embodiment discloses a protective film against infrared laser eavesdropping and electromagnetic information leakage, such as Figure 1 As shown, it includes a base layer, an ITO layer, a conductive Permalloy, a mounting adhesive layer and a protective layer stacked in sequence. The functions, compositions and molding methods of each layer structure are as follows:

[0078] The base layer is used to provide support for the protective film, and is preferably made of PET plastic with a thickness of 50 μm. The function of the ITO layer is to shield electromagnetic radiation and infrared absorption. The material forming the ITO layer is nano-metal oxide ultra-fine nanoparticles with a diameter of 20 nm. The nano-metal oxide ultra-fine nanoparticles are mixed with indium oxide and tin oxide in a mass ratio of 95:5. The ITO layer is attached to the base layer by sputtering coating, and the thickness of the nano-semiconductor layer is 40 nm.

[0079] Conductive Permalloy is used to protect against electromagnetic information leakage. The material used to form the conductive Permalloy is Permalloy. The Fe-Ni alloy is attached to ITO by sputtering to form a conductive and magnetic Permalloy. The thickness of the Permalloy is 10nm. The mounting adhesive layer is an acrylic adhesive, which is used to adhere the protective layer. The protective layer is used to protect the protective film and can be made of PET plastic with a thickness of 10μm.

[0080] Example 3

[0081] This embodiment discloses a protective film against infrared laser eavesdropping and electromagnetic information leakage, such as Figure 1 As shown, it includes a base layer, a conductive permalloy, a cesium tungsten bronze layer, a mounting adhesive layer and a protective layer stacked in sequence. The functions, compositions and molding methods of each layered structure are as follows:

[0082] The base layer is used to provide support for the protective film, and is preferably made of PET plastic with a thickness of 50 μm. The conductive permalloy is used to protect against electromagnetic information leakage. The material forming the conductive permalloy is an iron-nickel alloy, which is attached to the base layer by sputtering to form a conductive and magnetic conductive layer with a thickness of 10 nm.

[0083] The cesium tungsten bronze layer is used for infrared absorption and electromagnetic shielding. The cesium tungsten bronze layer is attached to the permalloy by sputtering. The thickness of the cesium tungsten bronze layer is 40nm. The mounting adhesive layer is an acrylic adhesive, which is used to adhere the protective layer. The protective layer is used to protect the protective film and can be made of PET plastic with a thickness of 10μm.

[0084] Example 4

[0085] This embodiment discloses a protective film to prevent infrared laser information leakage and electromagnetic information leakage, such as Figure 3 As shown, it includes a base layer, an ITO layer, a conductive Permalloy, a cesium tungsten bronze layer, a mounting adhesive layer and a protective layer stacked in sequence. The functions, compositions and molding methods of each layer structure are as follows:

[0086] The base layer is used to provide support for the protective film, and is preferably made of PET plastic with a thickness of 50 μm. The function of the ITO layer is to shield electromagnetic radiation and infrared absorption. The material forming the ITO layer is nano-metal oxide ultra-fine nanoparticles with a diameter of 20 nm. The nano-metal oxide ultra-fine nanoparticles are mixed with indium oxide and tin oxide in a mass ratio of 95:5. The ITO layer is attached to the base layer by sputtering coating, and the thickness of the nano-semiconductor layer is 40 nm.

[0087] Conductive Permalloy is used to protect against electromagnetic information leakage. The material forming the conductive and magnetic conductive layers is an iron-nickel alloy. The iron-nickel alloy is attached to the base layer by sputtering to form the conductive and magnetic conductive layers. The thickness of the conductive and magnetic conductive layers is 10nm.

[0088] The cesium tungsten bronze layer is used for infrared absorption and electromagnetic shielding. The cesium tungsten bronze layer is attached to the metal layer by sputtering or coating. The thickness of the cesium tungsten bronze layer is 40nm. The cesium tungsten bronze target is made of Cs0.33WO3 powder by vacuum calcination and pressing. The Cs0.33WO3 powder cesium tungsten bronze is synthesized by citric acid induced hydrothermal synthesis. The sputtering coating thickness of the Cs0.33WO3 layer is between 0.01nm and 1000nm.

[0089] The mounting adhesive layer is an acrylic adhesive, which is used to adhere the protective layer. The protective layer is used to protect the protective film and can be made of PET plastic with a thickness of 10μm.

[0090] Finally, the applicant used the flange coaxial method and the spectrophotometer to test the electromagnetic shielding performance and spectral transmittance performance of the protective films described in Examples 1-4, respectively. The test results are shown in Table 1 and Table 2 below, respectively:

[0091] Table 1 Electromagnetic shielding performance test

[0092]

[0093] Table 2 Spectral transmittance performance test

[0094]

[0095]

[0096] Although the present invention has been disclosed as above with preferred embodiments, it is not intended to limit the present invention. A person with ordinary knowledge in the technical field to which the present invention belongs may make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be determined by the definition of the claims.

Claims

1. A protective film against infrared laser eavesdropping and electromagnetic information leakage, characterized in that: The invention comprises a first infrared absorption layer (1), an electromagnetic shielding layer (2) and a second infrared absorption layer (3) which are stacked in sequence.

2. The protective film against infrared laser eavesdropping and electromagnetic information leakage according to claim 1, characterized in that: It also comprises a substrate (200), a mounting adhesive layer (210) and a protective layer (220), wherein the protective layer (220), the mounting adhesive layer (210), the second infrared absorption layer (3), the electromagnetic shielding layer (2), the first infrared absorption layer (1) and the substrate (200) are arranged in sequence from top to bottom.

3. The protective film against infrared laser eavesdropping and electromagnetic information leakage according to claim 1, characterized in that: The material of the first infrared absorption layer (1) is ITO, and the thickness of the first infrared absorption layer (1) is between 0.01nm and 1000nm. The electromagnetic shielding layer (2) is Permalloy, and the thickness of the electromagnetic shielding layer (2) is between 0.01 and 100nm. The second infrared absorption layer (3) is cesium tungsten bronze, and the thickness of the second infrared absorption layer (3) is between 0.01nm and 1000nm.

4. The protective film against infrared laser eavesdropping and electromagnetic information leakage according to claim 2, characterized in that: The material of the substrate (200) is PET, PVB or EVA plastic, and the thickness of the substrate (200) is 10-100 μm.

5. The protective film against infrared laser eavesdropping and electromagnetic information leakage according to claim 2, characterized in that: The adhesive used for the installation adhesive layer (210) is an acrylic adhesive, the material of the protective layer (220) is PET, PVB or EVA, and the thickness of the protective layer (220) is 10 to 50 μm.

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