Electromagnetic wave absorber

Abstract

The present application provides a kind of electromagnetic wave absorber, it is characterized in that, including: magnetic metal powder layer, by the composition comprising metal magnetic particle and binder resin is formed;And protective layer, is formed in the upper portion of the above MMP layer, the above metal magnetic particle includes iron silicon aluminum alloy and iron silicon alloy, the performance coefficient A of the above MMP layer according to formula 1 is 4005-5445, the impedance coefficient residual rate X of the above MMP layer according to formula 2 is 16% to 28%.

Description

Technical Field

[0001] This invention relates to an electromagnetic wave absorber for flexible printed circuit board (FPCB) processes, and more specifically, to an electromagnetic wave absorber that, in display panels using hinge materials with magnetic properties, can prevent physical properties from being degraded by strong external magnetic fields and can prevent sensitivity deviations in the digitizer function. Background Technology

[0002] In recent years, flexible printed circuit boards (FPCBs), developed with the miniaturization and lightweighting of electronic products, have been widely used as electronic components in various electronic parts. They have excellent processability, strong heat resistance, bending resistance and chemical resistance, and are also heat resistant.

[0003] On the other hand, with the development of electronic / communication technologies, electromagnetic interference (EMI), which causes equipment malfunctions due to mutual interference of electromagnetic waves, has become a problem. Therefore, electromagnetic wave absorbers are applied to electronic components to prevent the influence of electromagnetic waves.

[0004] Furthermore, foldable mobile devices, such as foldable phones, are now widely used. These devices utilize flexible OLED displays, which improve portability through folding and can be used as a widescreen display when unfolded. Foldable devices include a hinge part that allows the display to fold and unfold. This hinge part is primarily made of lightweight and highly rigid stainless steel to ensure robustness and safety. However, the stainless steel hinge part generates a magnetic field, which can affect the digitizer and degrade its performance. Specifically, the magnetic field generated by the hinge part can interfere with the interaction between the stylus and the digitizer, making it difficult to detect the stylus's accurate position, potentially leading to malfunctions, and causing sensitivity discrepancies between the folded part, which is directly affected by the hinge part, and the non-folded part, which is not directly affected by the hinge part.

[0005] Therefore, there is a need for a technology that, despite being affected by external magnetic fields as described above, can simultaneously meet the requirements of electromagnetic susceptibility (EMS) performance for normal operation and the ability to absorb electromagnetic interference generated in the circuit without compromising physical properties.

[0006] Furthermore, due to the high-performance requirements of portable terminal devices such as smartphones equipped with digitizers (i.e., handwriting tablets), the strength of the magnetic field generated at the hinge is trending towards increase. As mentioned above, there is a further need to develop a technology that can prevent a digitizer sensitivity deviation between the portion located above the hinge that generates the strong magnetic field and is directly affected, and the portion not located above the hinge. Summary of the Invention

[0007] Technical issues

[0008] The object of this invention is to provide an electromagnetic wave absorber that can prevent device malfunction without degrading its physical properties even in a strong magnetic field environment generated by the hinge portion, making it suitable for use in foldable devices including a hinge portion that generates a strong magnetic field. Furthermore, the object of this invention is to provide an electromagnetic wave absorber that can prevent a digitizer sensitivity deviation between the portion located above and directly affected by the hinge portion that generates the strong magnetic field and the portion not located above the hinge portion.

[0009] Furthermore, the object of the present invention is to provide an electromagnetic wave absorber that exhibits the characteristics described above while achieving thin film formation by including a single-layer MMP layer.

[0010] The objectives of this invention are not limited to those described above. Other objectives and advantages of this invention not mentioned herein will be understood through the following description and will become clearer through embodiments of the invention. Furthermore, it will be apparent that the objectives and advantages of this invention can be achieved through the solutions and combinations thereof pointed out in the claims.

[0011] Technical solution

[0012] To solve the technical problems described above, according to an embodiment of the present invention, an electromagnetic wave absorber can be provided, characterized in that it comprises: a magnetic metal powder layer (MMP layer) formed of a composition comprising metallic magnetic particles and a binder resin; and a protective layer formed on the upper part of the MMP layer, wherein the metallic magnetic particles comprise sentust (Fe-Si-Al based alloy) and Fe-Si based alloy, the performance coefficient A of the MMP layer according to Formula 1 is 4005 to 5445, and the impedance coefficient retention rate X of the MMP layer according to Formula 2 is 16% to 28%.

[0013] The MMP layer can be a single layer, and the thickness of the MMP layer can be from 25 μm to 40 μm.

[0014] The aforementioned MMP layer may contain 10 to 90% by weight of the aforementioned metallic magnetic particles.

[0015] The aforementioned iron-silicon-aluminum alloy and iron-silicon alloy can be mixed in a weight ratio of 5:5 to 9.5:0.5.

[0016] The aforementioned adhesive resin may include one selected from the group consisting of epoxy resins, phenoxy resins, acrylic resins, melamine resins, synthetic rubber resins, silicone resins, fluorinated resins, polyamide resins, polyester resins, polyethylene resins, polypropylene resins, polyvinyl chloride resins, and combinations thereof.

[0017] The aforementioned protective layer may be formed from one of the following: polyimide (PI) film, polyethylene terephthalate (PET) film, and polyethylene naphthalate (PEN) film.

[0018] The thickness of the aforementioned protective layer can be from 1 μm to 5 μm.

[0019] The total thickness of the MMP layer and the protective layer can be from 20 μm to 50 μm.

[0020] The electromagnetic wave absorber may further include a coated material layer formed on the lower part of the MMP layer, wherein the coated material layer may be formed from one of the groups selected from polyimide film, polyethylene terephthalate film and polyethylene naphthalate film.

[0021] It may also include an anti-stick substrate layer disposed on the upper part of the above-mentioned protective layer, the anti-stick substrate layer being formed of one of the groups selected from release paper and polyethylene terephthalate film treated with anti-stick properties.

[0022] The effects of the invention

[0023] Even in a strong magnetic field environment generated by the hinge, the electromagnetic wave absorber of the present invention can prevent device malfunction without degrading its physical properties. Furthermore, it can simultaneously prevent digitizer sensitivity deviation between the portion located above and directly affected by the hinge that generates the strong magnetic field and the portion not located above the hinge. Therefore, the above-described electromagnetic wave absorber can be used in foldable devices that include a hinge that generates a strong magnetic field.

[0024] Furthermore, the electromagnetic wave absorber of the present invention can exhibit the excellent physical properties described above while achieving thin film formation by including a single-layer MMP layer.

[0025] The effects of this specification are not limited to those described above, and those skilled in the art will clearly understand from the following description other effects not mentioned. In addition to the effects described above, specific effects of the invention are described while explaining specific aspects for carrying out the invention. Attached Figure Description

[0026] Figure 1 This is a cross-sectional view of an electromagnetic wave absorber according to an embodiment of the present invention.

[0027] Figure 2 A cross-sectional view of an electromagnetic wave absorber according to another embodiment of the present invention is shown.

[0028] Figure 3 This is a cross-sectional view showing an electromagnetic wave absorber according to another embodiment of the present invention.

[0029] Figure 4 The results of sensitivity measurements performed using Example 1 according to Experimental Example 3 are shown.

[0030] Figure 5 The results of sensitivity measurements performed using Comparative Example 6 according to Experimental Example 3 are shown. Brief explanation of the reference numerals in the figures:

[0031] 10: Protective layer;

[0032] 20: MMP layer;

[0033] 30: The layer of material to be coated;

[0034] 40: Anti-stick substrate layer;

[0035] 100: Electromagnetic wave absorber;

[0036] 200: Monitor;

[0037] 300: Metallic tape. Detailed Implementation

[0038] The above-described objects, features, and advantages will be described in detail with reference to this specification, thereby enabling those skilled in the art to readily implement the technical concept of the present invention. In describing the present invention, detailed descriptions of well-known techniques related to the invention will be omitted when it is determined that such descriptions may unnecessarily obscure the spirit of the invention. Hereinafter, preferred embodiments of the invention will be described in detail with reference to the accompanying drawings. The same reference numerals in the drawings are used to denote the same or similar structural elements.

[0039] In the contents not described in this specification, descriptions of contents that can be technically inferred by a person skilled in the art will be omitted.

[0040] In this specification, the presence of any structure "above (or below)" a structural element or "on the upper (or lower) part" of a structural element not only means that any structure is configured to contact the upper (or lower) part of the structural element, but also means that other structures may be inserted between the structural element and any structure provided above (or below) the structural element.

[0041] Unless otherwise expressly defined in the context, the singular expressions used in this specification include the plural expressions. In this invention, terms such as "composed of" or "comprising" should not be construed as necessarily including all structural elements described in the specification, but rather as potentially excluding some structural elements, or potentially including additional structural elements.

[0042] like Figure 1 As shown in the simplified cross-sectional view, the electromagnetic wave absorber of the present invention includes: a magnetic metal powder layer (MMP layer) formed of a composition comprising magnetic metal particles and a binder resin; and a protective layer formed on the upper part of the MMP layer.

[0043] The aforementioned metallic magnetic particles may include iron-silicon-aluminum alloys and iron-silicon alloys. The performance coefficient A of the aforementioned MMP layer according to Formula 1 below may be 4005 to 5445, and the impedance coefficient retention rate X of the aforementioned MMP layer according to Formula 2 below may be 16% to 28%.

[0044] Formula 1:

[0045] Performance factor A = (μ'-1) × thickness of MMP layer (μm)

[0046] In Equation 1 above, μ' represents the permeability of the MMP layer at a frequency of 3 MHz.

[0047] Formula 2:

[0048]

[0049] In Equation 2 above, the impedance coefficient B represents the performance coefficient of the MMP layer in a magnetic field environment of 50 Gauss.

[0050] Electromagnetic wave absorbers require different coefficient of performance values ​​depending on the electronic product in which they are used. The aforementioned electromagnetic wave absorbers include MMP layers with a coefficient of performance A of 4005 to 5445 and are used in mobile devices.

[0051] On the other hand, even if the MMP layer exhibits the performance coefficient A specified according to Equation 1, when it is in an environment with a strong magnetic field, such as the hinge section, the impedance coefficient B changes, which may lead to a change in the impedance coefficient retention rate X.

[0052] The impedance coefficient retention rate X is calculated using Equation 2, which divides the impedance coefficient B (a performance coefficient in a 50 Gauss magnetic field) by the aforementioned performance coefficient A, and then multiplies by 100. This retention rate X indicates whether the device can function properly when subjected to a magnetic field generated by a strong external magnetic force, such as a hinge. The aforementioned MMP layer can exhibit an impedance coefficient retention rate X of 16% to 28%. Therefore, even in display panels that further utilize hinge materials with magnetic properties, such as those for foldable mobile devices, the aforementioned electromagnetic wave absorber can prevent device malfunctions without degrading physical properties.

[0053] The aforementioned electromagnetic wave absorber can simultaneously possess a performance coefficient A of 4005 to 5445 and an impedance coefficient retention rate X of 16% to 28%. Therefore, it can prevent digitizer sensitivity deviation between the portion located above the hinge section that generates the strong magnetic field and is directly affected, and the portion not located above the hinge section. Consequently, it exhibits excellent performance in tasks such as note-taking, drawing, and editing images or photographs using a digitizer.

[0054] MMP layer

[0055] Electromagnetic wave absorbers can exert their electromagnetic wave absorption properties by including an MMP layer. The MMP layer consists of a composition containing metallic magnetic particles and a binder resin, and more specifically, it can be a layer formed by dispersing the metallic magnetic particles in the binder resin.

[0056] Specifically, electromagnetic waves refer to fluctuations caused by electric and magnetic fields. Typically, the magnetic field refers only to EMI (internal electromagnetic field) generated in circuits; therefore, the aim is often to achieve excellent EMI blocking. However, this invention relates to an electromagnetic wave absorber that exhibits superior characteristics against magnetic fields, including the magnetic force (DC magnetic field) generated by the hinge portion of a foldable device.

[0057] The aforementioned electromagnetic wave absorber uses iron-silicon-aluminum alloy and a hybrid alloy of iron-silicon alloy as metallic magnetic particles in the MMP layer. This allows it to exhibit excellent EMS performance against magnetic forces (DC magnetic fields) while shielding EMI (alternating magnetic fields). Furthermore, it can improve the impedance coefficient B and impedance coefficient retention rate X while maintaining the required performance coefficient A of the mobile device.

[0058] Because the aforementioned iron-silicon-aluminum alloy exhibits high magnetic permeability (μ'), the performance coefficient A can be improved. This iron-silicon-aluminum alloy can be composed solely of Fe, Si, and Al.

[0059] Compared to other metallic magnetic particles such as iron-silicon-aluminum alloys, the aforementioned iron-silicon alloys possess high saturation magnetic flux density (Ms) and low permeability (μ'), yet can impart high impedance to magnetic fields induced by magnetic force, such as direct current (DC). These iron-silicon alloys can consist solely of Fe and Si. The saturation magnetic flux density is determined by the Fe content within the magnetic particles.

[0060] When the MMP layer contains many other metallic magnetic particles with high saturation magnetic flux density (Ms), there is a problem that the performance coefficient decreases due to the permeability becoming too low. The aforementioned MMP layer contains the aforementioned iron-silicon-aluminum alloy and a mixture of the aforementioned iron-silicon alloy, so even if it contains a high content of the aforementioned iron-silicon alloy, the desired performance coefficient and impedance coefficient retention rate X can be easily adjusted.

[0061] Although not limited to this, in the aforementioned MMP layer, the content ratio of the aforementioned iron-silicon-aluminum alloy to the aforementioned iron-silicon alloy can be a weight ratio of 5:5 to 9.5:0.5. For example, when the content of the iron-silicon alloy is greater than the aforementioned range, the performance coefficient decreases; when the content of the iron-silicon alloy is less than the aforementioned range, the EMS performance decreases due to the decrease in the impedance coefficient retention rate X.

[0062] Although the MMP layer is not limited to this, the content of the aforementioned metallic magnetic particles can be from 10% to 90% by weight or from 30% to 90% by weight.

[0063] Furthermore, the aforementioned MMP layer may contain 6 to 33 wt% of the aforementioned iron-silicon alloy. When the content of the aforementioned iron-silicon alloy is less than the aforementioned range, there may be a problem of reduced impedance coefficient retention rate X; when the content of the iron-silicon alloy is greater than the aforementioned range, there may be a problem of reduced performance coefficient.

[0064] The aforementioned MMP layer may include an adhesive resin, which may include one selected from the group consisting of epoxy resins, phenoxy resins, acrylic resins, melamine resins, synthetic rubber resins, silicone resins, fluorinated resins, polyamide resins, polyester resins, polyethylene resins, polypropylene resins, polyvinyl chloride resins, and combinations thereof.

[0065] With the increasing demands for high performance in foldable mobile devices, the strength of the magnetic field generated by the hinge is increasing. As a result, existing electromagnetic wave absorbers often fail to provide sufficient shielding. Therefore, attempts have been made to address this issue by including two or more MMP layers and changing the metallic magnetic particles in each layer. However, this leads to increased thickness, which may not align with the trend towards thin-film designs and is also uneconomical.

[0066] The aforementioned electromagnetic wave absorber can achieve thin-film processing using a single-layer MMP layer while exhibiting the aforementioned performance coefficient A and impedance coefficient retention rate X. Therefore, in display panels that further utilize magnetic hinge materials, such as in foldable mobile devices, device malfunctions can be prevented without degrading physical properties. Simultaneously, it prevents digitizer sensitivity deviations between the portion located above and directly affected by the hinge section that generates a strong magnetic field and the portion not located above the hinge section.

[0067] The thickness of the MMP layer can be adjusted according to requirements; for example, the thickness of the MMP layer can be from 25 μm to 40 μm. When the thickness of the MMP layer is less than 25 μm, the residual impedance coefficient decreases due to the reduced Fe-Si particle content, which may lead to a decrease in EMS performance. When it is greater than 40 μm, it may be unusable because it does not conform to the trend of thin film production.

[0068] protective layer

[0069] As described above, in the electromagnetic wave absorber of the present invention, a protective layer 10 for protecting the MMP layer is included on the upper part of the MMP layer 20. Therefore, the impedance of the MMP layer to physical / chemical shocks when exposed can be improved.

[0070] The aforementioned protective layer 10 may be formed from one of the following: polyimide film, polyethylene terephthalate film, and polyethylene naphthalate film.

[0071] Preferably, the thickness of the protective layer 10 is 1 to 5 μm. Even with a thin film protective layer within this range, the electromagnetic wave absorber can exhibit excellent impedance to physical / chemical shocks. For example, when the thickness of the protective layer 10 is less than 1 μm, it is difficult to exert the protective effect of the MMP layer, and when it is greater than 5 μm, the performance as an electromagnetic wave absorber may be reduced.

[0072] Furthermore, from the viewpoint of ensuring that the electromagnetic wave absorber has a suitable thickness while exerting the electromagnetic wave absorption effect, the sum of the thicknesses of the protective layer 10 and the MMP layer 20 is preferably 20 to 50 μm, and more preferably 28 to 43 μm.

[0073] Coated material layer

[0074] Figure 2 This is a cross-sectional view illustrating an electromagnetic wave absorber according to an embodiment of the present invention. Figure 2As shown, the electromagnetic wave absorber of the present invention may further include a coated material layer 30 at the lower part of the MMP layer 20. The coated material layer may be formed from one selected from the group consisting of polyimide film, polyethylene terephthalate film, and polyethylene naphthalate film. For example, the coated material layer may be a thin, non-stick PET.

[0075] Anti-stick substrate layer

[0076] Figure 3 This is a cross-sectional view illustrating an electromagnetic wave absorber according to an embodiment of the present invention. Figure 3 As shown, it may also include an anti-stick substrate layer 40 disposed on the upper part of the above-mentioned protective layer 10. The above-mentioned anti-stick substrate layer 40 may be formed of one of the groups selected from the group consisting of anti-stick paper and polyethylene terephthalate film treated with anti-stick properties.

[0077] The electromagnetic wave absorber of the present invention can be used as an electromagnetic wave shielding sheet for the digitizer of electronic products. The entire preparation method of the above-mentioned electromagnetic wave absorber can be carried out by a roll-to-roll process.

[0078] The structure and function of the present invention will be described in more detail below through preferred embodiments. However, this is presented as a preferred example of the present invention, and the present invention is not to be construed as limited to the above embodiments in any way.

[0079] Example

[0080] Example 1

[0081] A magnetic composition was prepared by mixing 83% by weight (weight ratio: iron-silicon-aluminum alloy: iron-silicon alloy = 9.3:0.7) of metallic magnetic particles containing 77% by weight of iron-silicon-aluminum alloy and 6% by weight of iron-silicon alloy with an acrylic adhesive resin. Furthermore, a 25 μm MMP layer 20 was formed by coating the magnetic composition onto one side of a coating material layer 30 (thin, non-stick PET).

[0082] Then, an electromagnetic wave absorber is prepared by placing the above-mentioned MMP layer on the side of the PET film (protective layer 10) with a 50μm carrier film attached, on which the carrier film is not formed, and then performing a roll-lamping process together.

[0083] Examples and Comparative Examples

[0084] Except for the changes to the metallic magnetic particles of Example 1 as shown in Table 1 below, the electromagnetic wave absorbers of the Examples and Comparative Examples were prepared using the same method as in Example 1.

[0085] Table 1

[0086]

[0087]

[0088] evaluate

[0089] Experiment Example 1: Evaluating Performance Coefficients

[0090] 1) The electromagnetic wave absorbers prepared in the examples and comparative examples were hardened in a hot press with a surface pressure of 50 kgf at a temperature of 150°C for the upper and lower plates, and samples of the above examples and comparative examples (size: 100 mm × 100 mm, thickness: 50 μm) were prepared using a sample cutting machine.

[0091] 2) After setting the Impedance Analyzer E4991A impedance meter to Permeability mode, perform calibration.

[0092] 3) Scan three cycles at a frequency of 3 MHz, then confirm the permeability (μ') value, and then substitute it into the performance coefficient conversion formula of the following equation (1) to convert it into a performance coefficient value. Repeat this three times to obtain the average value, which is shown in Table 2 below.

[0093] Formula 1:

[0094] Performance factor A = (μ'-1) × thickness of MMP layer (μm)

[0095] In Equation 1 above, μ' represents the permeability of the MMP layer at a frequency of 3 MHz.

[0096] Electromagnetic wave absorbers (MMP layers) require different coefficient of performance (COP) values ​​depending on the electronic product in which they are applied. In the case of mobile devices, a COP value of 4005 to 5445 is required.

[0097] Experimental Example 2: Evaluation of Impedance Coefficient B and Impedance Coefficient Residual Rate X

[0098] An environment with a 50 Gauss magnetic field was created using an Impedance Analyzer E4991A, and then calibrated after being set to permeability mode. Furthermore, the coefficients of the MMP layers prepared in the examples and comparative examples according to Equation 1 were determined using the same method as in Example 1.

[0099] This represents the impedance coefficient B, which evaluates whether the device functions properly when subjected to electromagnetic waves generated by an external magnetic force. A higher value indicates that it can function normally without being affected by electromagnetic waves generated by an external magnetic force.

[0100] Furthermore, the residual rate X of the impedance coefficient was determined according to Equation 2 below, and the results are recorded in Table 2 below.

[0101] Formula 2:

[0102] Impedance coefficient retention rate X = (Impedance coefficient B ÷ Performance coefficient A) × 100

[0103] Experiment Example 3: Pen / Digitizer Sensitivity Deviation

[0104] Each electromagnetic wave absorber 100 prepared in the embodiments and comparative examples was attached to the display 200, and metal (Cu) tape 300 was attached to the other side of the electromagnetic wave absorber not attached to the display. Furthermore, similar to the environment of a mobile device, with it connected to the hinge, the inductance was measured using an LCR Meter 4284A inductance meter and a digital oscilloscope voltage meter. (Reference) Figure 5 )

[0105] Sensitivity deviation occurs when the inductance value exceeds the range of 44.8μH to 44.9μH, and is therefore indicated as "O". No sensitivity deviation occurs when the inductance value does not exceed the range of 44.8μH to 44.9μH, and is therefore indicated as "X". The results are shown in Table 2 below.

[0106] Figure 4 The results of sensitivity measurements performed according to Experimental Example 3 using Example 1 show that a constant inductance value is exhibited throughout the electromagnetic wave absorber in the range of 44.8 μH to 44.9 μH.

[0107] on the contrary, Figure 5 The results of sensitivity measurements performed using Comparative Example 6 according to Experimental Example 3 show that, in the portion corresponding to the hinge, the inductance is reduced to outside the range of 44.8 μH to 44.9 μH.

[0108] Table 2

[0109]

[0110] As shown in the table above, it can be confirmed that the embodiments exhibit a performance coefficient A suitable for mobile devices, while simultaneously exhibiting a high impedance coefficient retention rate X. Furthermore, it can be confirmed that no sensitivity deviation occurs even in the presence of a hinge exhibiting strong magnetic force. Conversely, it is confirmed that the comparative examples exceed the performance coefficient A range of the present invention or have a low impedance coefficient retention rate X. Moreover, as... Figure 5 As shown, it was confirmed that in the comparative example, the part where the hinge is located experienced a sensitivity deviation.

[0111] As described above, the present invention has been illustrated, but it is obvious that the present invention is not limited to the embodiments disclosed in this specification, and various modifications can be made by those skilled in the art within the scope of the technical concept of the present invention. Furthermore, even though the effects of the structure according to the present invention have not been explicitly described and explained in the above description of the embodiments, it should be acknowledged that the predictable effects due to this structure are self-evident.

Claims

1. An electromagnetic wave absorber, characterized in that, include: A magnetic metal powder layer, formed of a composition comprising magnetic metal particles and a binder resin; and A protective layer is formed on top of the aforementioned magnetic metal powder layer. The aforementioned metallic magnetic particles include iron-silicon-aluminum alloys and iron-silicon alloys. According to Equation 1 below, the performance coefficient A of the above-mentioned magnetic metal powder layer is 4005 to 5445. According to Equation 2 below, the impedance coefficient retention rate X of the aforementioned magnetic metal powder layer is 16% to 28%. Formula 1: Performance coefficient A = (μ'-1) × thickness of magnetic metal powder layer (μm) In Equation 1 above, μ' represents the magnetic permeability of the magnetic metal powder layer at a frequency of 3 MHz. Formula 2: Impedance coefficient retention rate X = (Impedance coefficient B ÷ Performance coefficient A) × 100 In Equation 2 above, the impedance coefficient B represents the performance coefficient of the magnetic metal powder layer under a magnetic field of 50 Gauss.

2. The electromagnetic wave absorber according to claim 1, characterized in that, The magnetic metal powder layer is a single layer, and the thickness of the magnetic metal powder layer is 25 μm to 40 μm.

3. The electromagnetic wave absorber according to claim 1, characterized in that, The aforementioned magnetic metal powder layer comprises 10 to 90% by weight of the aforementioned magnetic metal particles.

4. The electromagnetic wave absorber according to claim 1, characterized in that, The above-mentioned iron-silicon-aluminum alloy and the above-mentioned iron-silicon alloy are mixed in a weight ratio of 5:5 to 9.5:0.

5.

5. The electromagnetic wave absorber according to claim 1, characterized in that, The aforementioned adhesive resin includes one selected from the group consisting of epoxy resins, phenoxy resins, acrylic resins, melamine resins, synthetic rubber resins, silicone resins, fluorinated resins, polyamide resins, polyester resins, polyethylene resins, polypropylene resins, polyvinyl chloride resins, and combinations thereof.

6. The electromagnetic wave absorber according to claim 1, characterized in that, The aforementioned protective layer is formed from one of the following: polyimide film, polyethylene terephthalate film, and polyethylene naphthalate film.

7. The electromagnetic wave absorber according to claim 1, characterized in that, The thickness of the aforementioned protective layer is 1 μm to 5 μm.

8. The electromagnetic wave absorber according to claim 1, characterized in that, The total thickness of the magnetic metal powder layer and the protective layer is 20 μm to 50 μm.

9. The electromagnetic wave absorber according to claim 1, characterized in that, The electromagnetic wave absorber further includes a coating material layer formed on the lower part of the magnetic metal powder layer, the coating material layer being formed of one of the following: polyimide film, polyethylene terephthalate film, and polyethylene naphthalate film.

10. The electromagnetic wave absorber according to claim 1, characterized in that, It also includes an anti-stick substrate layer disposed on the upper part of the above-mentioned protective layer, the anti-stick substrate layer being formed of one of the groups selected from anti-stick paper and polyethylene terephthalate film subjected to anti-stick treatment.

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