Magnetic composites and RFID tags

Abstract

To provide a magnetic composite body having a ferrite layer which has comparatively thick film thickness, is excellent in various characteristics such as electric insulation property and has good adhesion, and an RFID tag having the magnetic composite body.SOLUTION: A magnetic composite body has a resin base material, and a ferrite layer provided on the surface of the resin base material, wherein the ferrite layer has a spinel type crystal phase as a base phase, thickness (dF) of 2.0 μm or more, and the full width at half maximum (FWHM) of a diffraction line (I311) based on a (311) plane of the spinel type crystal phase in X-ray diffraction analysis using Co-Kα as a radiation source of 1.000° or more and 1.200° or less.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] This invention relates to magnetic composites and RFID tags. [Background technology]

[0002] RFID (Radio Frequency Identification) systems are a technology that uses electromagnetic waves for contactless communication to identify individual objects, and are attracting attention as a key device for realizing a ubiquitous society. A typical RFID system consists of RFID tags, reader / writers, and processing systems. RFID tags mainly consist of an IC chip and an antenna. The reader / writer communicates with the tag using electromagnetic induction or electromagnetic waves, thereby exchanging information with the IC chip embedded in the tag.

[0003] RFID systems are broadly classified into three types based on their operating frequency: HF band (e.g., 13.56 MHz), UHF band (e.g., 915-928 MHz), and microwave (e.g., 2.45 GHz). HF band RFID uses an electromagnetic induction short-range communication system and is used in mobile phone billing systems (such as Osaifu-Keitai®) and IC card transit tickets (such as Suica®). In contrast, UHF band RFID systems use an electromagnetic wave communication system, offering longer communication ranges and wider coverage areas compared to HF band systems. They also have the advantage of recognizing multiple tags simultaneously. Therefore, market expansion is expected in areas such as logistics management, product management, and individual vehicle and person tracking.

[0004] Incidentally, when using RFID, the presence of metal near the tag can degrade its transmission and reception performance (reading performance). For example, when tags are attached to metal objects for logistics management or product management applications, electromagnetic interference from the metal can occur, leading to a decrease in transmission and reception performance. Specifically, electromagnetic waves sent from the reader / writer to the tag are focused by the metal, generating eddy currents and causing losses. As a result, the energy needed to send data back from the tag to the antenna becomes inefficient, leading to a decrease in reading performance, such as reading distance.

[0005] To address these issues, a method has been proposed in which a magnetic sheet containing magnetic powder, such as ferrite powder, is attached to the tag. By placing a magnetic sheet between the tag's antenna and the IC chip, the electromagnetic waves received by the antenna are focused onto the magnetic sheet, thus suppressing the absorption of electromagnetic waves even if metal is nearby. Furthermore, because ferrite powder has high electrical resistance, losses due to eddy currents are small. Therefore, this is believed to lead to improved reading performance.

[0006] For example, Patent Document 1 discloses a polymer thick-film shielding composition comprising a soft ferrite powder dispersed in an organic solvent containing a thermoplastic resin (Claim 1-8 of Patent Document 1). It also describes that the shielding material is used in applications where a radio frequency identification (RFID) circuit needs to be shielded from other metal surfaces, and that the composition is screen-printed onto polyester or other substrates and dried (Claim 0001 of Patent Document 1).

[0007] Patent Document 2 discloses a ferrite composite sheet composed of ferrite particles and resin, having a three-dimensionally linked skeleton of ferrite particles, with the gaps between the skeleton filled with resin (Claim 1-8 of Patent Document 2). It is also stated that this composite sheet is useful for communication devices and communication terminals having a reader / writer communication spiral antenna because it can ensure a good communication distance (Claim 0039 of Patent Document 2).

[0008] Patent Document 3 discloses an RFID tag in which an FeNiZnCo ferrite film having a predetermined composition is disposed in contact with or in proximity to a main member including an antenna conductor (Claims 1 to 13 of Patent Document 3). It is also described that when the ferrite film is used for an RFID tag, even if there is a metal component in the vicinity of the tag, deterioration of transmission / reception performance can be suppressed, contributing to an improvement in recognition rate (

[0023] of Patent Document 3).

[0009] Patent Document 4 discloses manufacturing a ferrite film using the AD method or the ferrite plating method, although it is not for the purpose of an RFID tag, and applying this ferrite film to a radio wave absorber (Claims 1 to 3 of Cited Document 4). Specifically, ferrite raw material powder is blended so that the composition of the ferrite base material becomes Ni 0.5 Zn 0.5 Fe2O4, mixed with a mixer, then supplied to a nozzle, adjusting the pressure in the chamber to 7 Pa, and spraying the aerosolized ferrite raw material powder from the tip of the nozzle onto a substrate made of polyimide resin at a flow rate of 5 liters / min to produce a ferrite base material with a film thickness of 5 μm, and forming 16 holes with a diameter of 2 μm in this ferrite base material by an etching process to obtain a radio wave absorber (

[0020] of Cited Document 4).

Prior Art Documents

Patent Documents

[0010]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0011] Thus, although technologies for applying ferrite magnetic sheets to RFID tags have been proposed conventionally, there is room for improvement in the conventional technologies. Specifically, the magnetic properties and electrical insulation of the magnetic sheet in the UHF band are insufficient, and it is difficult to ensure sufficient reading performance (reading distance) when applying the magnetic sheet to a UHF band RFID tag. For example, in a sheet made of a composite material of ferrite powder and resin as disclosed in Patent Document 1 and Patent Document 2, there is a resin component that is non-magnetic. Since the filling rate of the ferrite component that is a magnetic material is low, there are limitations in enhancing magnetic properties and reading performance. In a UHF band RFID system, since mainly medium to long-distance communication is used, ensuring reading performance is important.

[0012] In addition, when applying a magnetic sheet provided on a base material to an RFID tag, there is a problem that the adhesion between the base material and the magnetic sheet is insufficient. In fields such as logistics management and product management, there are many cases where tags are reused. In such cases, the attachment and detachment of the tag are repeated, and stress is applied to the magnetic sheet each time. If the adhesion of the magnetic sheet is insufficient, the magnetic sheet may peel off from the base material, thereby deteriorating the performance of the tag and, in some cases, rendering it unusable.

[0013] <​​​​​​​​This invention was completed based on such findings, and aims to provide a magnetic composite having a ferrite layer that is relatively thick, has excellent properties such as electrical insulation, and has good adhesion, and an RFID tag equipped with the magnetic composite. [Means for solving the problem]

[0016] The present invention encompasses the following embodiments (1) to (6). In this specification, the expression "~" includes the numerical values ​​at both ends. That is, "X~Y" is synonymous with "X or more and Y or less".

[0017] (1) A magnetic composite comprising a resin substrate and a ferrite layer provided on the surface of the resin substrate, The ferrite layer has a spinel-type crystalline phase as its matrix, and a thickness (d F The ) is 2.0 μm or larger, and in X-ray diffraction analysis using Co-Kα as the radiation source, the diffraction line based on the (311) plane of the spinel-type crystal phase (I 311 A magnetic composite having a full width at half maximum (FWHM) of 1,000° or more and 1,200° or less.

[0018] (2) The magnetic composite according to (1), wherein the ferrite layer contains iron (Fe) and oxygen (O), and further contains at least one element selected from the group consisting of transition metal elements other than iron (Fe), lithium (Li), magnesium (Mg), and aluminum (Al).

[0019] (3) The resin substrate has a thickness (d R A magnetic composite according to (1) or (2) above, wherein the diameter is 10.0 μm or larger.

[0020] (4) The magnetic composite according to (1) or (2) above, wherein the ferrite layer has an arithmetic mean roughness (Ra) of its surface of 0.10 μm or more and 0.30 μm or less.

[0021] (5) The ferrite layer has a surface resistance of 1.00 × 10 9 Ω or more 1.00×10 12The magnetic composite of the above (1) or (2) that is Ω or less.

[0022] (6) An RFID tag including the magnetic composite of the above (1) or (2).

Advantages of the Invention

[0023] According to the present invention, there are provided a magnetic composite including a ferrite layer having a relatively thick film thickness, excellent various properties such as electrical insulation, and good adhesion, and an RFID tag including the magnetic composite.

Brief Description of the Drawings

[0024] [Figure 1] Shows one aspect of the magnetic composite. [Figure 2] Shows another aspect of the magnetic composite. [Figure 3] Shows another aspect of the magnetic composite. [Figure 4] Shows still another aspect of the magnetic composite. <00001�1>Shows an example of applying the magnetic composite to an RFID tag. [Figure 6] Shows an example of the configuration of an aerosol deposition film forming apparatus.

Modes for Carrying Out the Invention

[0025] Specific embodiments of the present invention (hereinafter referred to as "the present embodiment") will be described. Note that the present invention is not limited to the following embodiments, and various modifications can be made without changing the gist of the present invention.

[0026] <<1. Magnetic Composite>> The magnetic composite of the present embodiment includes a resin substrate and a ferrite layer provided on the resin substrate. The ferrite layer has a spinel-type crystal phase as a matrix phase and a thickness (d F ) of 2.0 μm or more. Further, the ferrite layer has a diffraction line (I 311 based on the (311) plane of the spinel-type crystal phase in X-ray diffraction analysis using Co-Kα as a radiation source.The full width at half maximum (FWHM) of the material is between 1.000° and 1.200°. The magnetic composite is described in detail below.

[0027] The resin substrate acts as a support base for the ferrite layer. The resin constituting the resin substrate is not particularly limited. It may be a single resin, or a mixture or copolymer of two or more resins. Preferably, the resin is at least one selected from the group consisting of polycarbonate (PC), polyimide (PI), polyvinyl chloride (PVC), polyoxymethylene (POM), acrylonitrile butadiene styrene (ABS), polyether ether ketone (PEEK), and polyamide (PA). These resins have excellent mechanical strength and excellent electrical insulation properties.

[0028] The specific gravity of the resin constituting the resin substrate is 0.95 g / cm³. 3 Preferably, the specific gravity is 0.95 g / cm³. 3 When the particles are smaller, the collision energy of the raw material particles when they collide with the substrate during film formation is more easily dispersed, making plastic deformation of the raw material particles less likely. Therefore, the formation of a ferrite layer becomes difficult.

[0029] The color tone of the resin substrate is not limited. For example, a colorless, transparent, or light-colored resin can be used. Alternatively, a resin that is colored to the extent that it transmits light may be used. In a magnetic composite made using such a resin as the substrate, the ferrite layer can be seen through the resin when viewed from a surface where the ferrite layer is not formed. Therefore, it is possible to impart a design feature to the composite that cannot be obtained when using a resin that does not transmit light.

[0030] The shape of the resin substrate is not limited. The substrate may be in sheet form, or it may have a shape other than a sheet. For example, a resin substrate with a complex three-dimensional shape may be used. Furthermore, the ferrite layer may be provided on the entire surface of the resin substrate, or on only a part of it. For example, a resin substrate with a complex shape may be used, and a ferrite layer may be provided on a part of this resin substrate. Conventionally, in order to provide a ferrite layer on a resin substrate with a complex shape, it was necessary to punch out a sheet-like resin substrate and then attach a ferrite sheet to the punched-out part. Using the magnetic composite of this embodiment eliminates the need for such work, thus enabling the acquisition of a magnetic composite at low cost. Also, unlike ferrite sheets which consist of an integral mixture of resin and filler, the resin substrate and the ferrite layer are clearly separated, so it is possible to provide a design that was not possible with conventional methods.

[0031] Preferably, the thickness of the resin substrate (d R The substrate thickness is 10.0 μm (0.01 mm or more). If the resin substrate is too thin, it becomes difficult to provide sufficient mechanical strength. A substrate thickness of 35.0 μm (0.035 mm) or more is more preferable, 100 μm (0.1 mm) or more is even more preferable, and 500 μm (0.5 mm) or more is particularly preferable. There is no particular upper limit to the substrate thickness. However, by moderately reducing the thickness, it becomes possible to give flexibility to the magnetic composite. For example, the magnetic composite can be applied to the curved surface of an RFID tag that has a curved surface. In addition, since the tag is made thinner, there is also the advantage that tags can be continuously issued using a label printer. The substrate thickness may be 5000 μm (5 mm) or less, 2000 μm (2 mm) or less, or 1000 μm (1 mm) or less.

[0032] The resin substrate may be in the form of a plate or a sheet. However, it is preferably in the form of a sheet. By using a sheet-shaped resin substrate (resin sheet), it becomes possible to produce a magnetic composite with excellent flexibility. The resin substrate may be composed solely of resin, or it may be a laminate of a non-resin substrate and a resin layer. In this case, the resin layer laminated on top of the non-resin substrate corresponds to the resin substrate. A metal film or the like can be used as the non-resin substrate.

[0033] The ferrite layer in this embodiment uses a spinel-type crystalline phase as its matrix. That is, it is a polycrystalline material mainly composed of spinel-type ferrite. It can also be described as an aggregate of crystalline grains composed of spinel-type ferrite. Spinel-type ferrite is a composite oxide of iron (Fe) having a spinel-type crystalline structure, and has the basic composition of AB2O4 (where A and B are Li, Mg, Mn, Fe, Co, Ni, Cu, and / or Zn, respectively). Furthermore, most spinel-type ferrites exhibit soft magnetism. By using a soft magnetic spinel-type crystalline phase as the matrix, that is, by incorporating a layer mainly composed of spinel-type ferrite, the magnetic properties of the magnetic composite become superior. In addition to spinel, AFe is also used. 12 O 19 There are ferrites with a magnetoplumbite-type hexagonal crystal structure that have basic compositions such as those mentioned above. However, most of these ferrites exhibit hard magnetism, and therefore cannot fully exhibit magnetic properties when applied to magnetic composites.

[0034] In this specification, the main component refers to a component with a content of 50.0% by mass or more. To take advantage of the excellent magnetic properties of spinel-type ferrite, the content of spinel-type ferrite (ferrite phase) in the ferrite layer is preferably 60.0% by mass or more, more preferably 70.0% by mass or more, even more preferably 80.0% by mass or more, and particularly preferably 90.0% by mass or more. The ferrite layer may also contain components other than ferrite. Examples of such components include the α-Fe2O3 phase.

[0035] The type of spinel-type ferrite is not particularly limited. For example, at least one selected from the group consisting of manganese (Mn) ferrite, manganese zinc (MnZn) ferrite, magnesium (Mg) ferrite, magnesium zinc (MgZn) ferrite, nickel (Ni) ferrite, nickel zinc (NiZn) ferrite, nickel copper zinc (NiCuZn) ferrite, cobalt (Co) ferrite, cobalt zinc (CoZn) ferrite, and lithium (Li) ferrite can be used. It may also be a mixed crystal and / or solid solution of multiple types of ferrite.

[0036] Preferably, the ferrite layer is nickel (Ni)-based ferrite, nickel-copper (NiCu)-based ferrite, or nickel-copper-zinc (NiCuZn)-based ferrite. These ferrites have excellent electrical insulation properties because they contain nickel (Ni) with a stable valency. The composition of the ferrite is not limited, but for example, it may be Fe2O3: 46.0~52.0 mol%, NiO: 10.0~20.0 mol%, CuO: 0.0~7.0 mol%, and ZnO: 25.0~35.0 mol%.

[0037] The thickness of the ferrite layer in this embodiment (d FThe thickness is limited to 2.0 μm or more. If the thickness is less than 2.0 μm, the thickness of the ferrite layer tends to become non-uniform, and the film strength decreases. In addition, this tends to lead to a decrease in magnetic properties. Therefore, when a magnetic composite is applied to an RFID tag, there is a risk that the reading performance will decrease. From the viewpoint of improving reading performance, a thickness of 10.0 μm or more is preferred, and 50.0 μm or more is more preferred. There is no upper limit to the thickness. However, it is difficult to deposit an excessively thick ferrite layer while maintaining its density. Also, if the ferrite layer is excessively thick, the internal stress of the ferrite layer becomes too large, and there is a risk that the ferrite layer will peel off. In particular, when imparting flexibility to the magnetic composite, it is desirable for the ferrite layer to be moderately thin. A thickness of 100.0 μm or less is preferred, 50.0 μm or less is more preferred, 20.0 μm or less is even more preferred, and 10.0 μm or less is particularly preferred. Furthermore, it is preferable that the ferrite layer is in direct contact with the resin substrate, that is, that no other layer is interposed between the ferrite layer and the resin substrate.

[0038] Note thickness (d F ) is the total thickness of the ferrite layer provided on the resin substrate. When the ferrite layer is provided on only one of the front or back surfaces of the substrate, the thickness of that ferrite layer is d F This corresponds to d. When ferrite layers are provided on both the front and back surfaces of the substrate, the sum of the thicknesses of the respective ferrite layers is d F It corresponds to this.

[0039] Furthermore, if the substrate is a laminate composed of multiple layers, the thickness of the layer in direct contact with the ferrite layer corresponds to the substrate thickness. If the substrate has irregularities, the arithmetic mean of the thinnest and thickest parts of the substrate where the ferrite layer is formed is the substrate thickness d. R The arithmetic mean of the thinnest and thickest parts of the composite and the thickness d of the substrate are used. R The difference is the thickness d of the ferrite layer. F When ferrite layers are formed on both sides of the composite, the arithmetic mean of the thinnest and thickest parts of the composite and the thickness d of the substrate are used. R The difference between this and the thickness d of the ferrite layer FIt is assumed that, in other words, if ferrite layers of the same thickness are formed on both sides of the substrate, then twice the thickness of the ferrite layer on one side is considered to be d. F It corresponds to this.

[0040] In this embodiment, the ferrite layer is characterized by a full width at half maximum (FWHM) of the diffraction line (I311) based on the (311) plane of the spinel-type crystal phase, as measured by X-ray diffraction analysis using Co-Kα as a radiation source, being limited to 1.000° or more and 1.200° or less. If the FWHM is less than 1.000°, the plastic deformation of the particles in the ferrite layer is insufficient. As a result, the anchoring effect to the substrate weakens, and the ferrite layer becomes more prone to peeling. There is also a risk of increased magnetic loss. On the other hand, if the FWHM exceeds 1.200°, the plastic deformation becomes excessive, resulting in the generation of a large amount of products other than ferrite, which leads to a decrease in magnetic properties.

[0041] Preferably, the ferrite layer contains iron (Fe) and oxygen (O), and further contains at least one element selected from the group consisting of transition metal elements other than iron (Fe), lithium (Li), magnesium (Mg), and aluminum (Al). Examples of transition metal elements other than iron (Fe) include at least one selected from the group consisting of titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), cobalt (Co), nickel (Ni), copper (Cu), and zinc (Zn).

[0042] Preferably, the ferrite layer contains ferrite components. Ferrite components are the components that make up the main component, spinel-type ferrite. For example, if the ferrite layer is mainly composed of manganese-zinc (MnZn) ferrite, the ferrite components are iron (Fe), manganese (Mn), zinc (Zn), and oxygen (O). If the ferrite layer is mainly composed of nickel-copper-zinc (NiCuZn) ferrite, the ferrite components are iron (Fe), nickel (Ni), copper (Cu), zinc (Zn), and oxygen (O). Furthermore, unavoidable impurities are components that are inevitably mixed in during manufacturing, and their content is typically 1000 ppm or less. In particular, it is preferable that the ferrite layer does not contain components other than oxides, especially resin components.

[0043] Preferably, the ferrite layer contains ferrite components, with the remainder being unavoidable impurities. That is, it is preferable that it does not contain organic or inorganic components other than ferrite components in amounts exceeding the amount of unavoidable impurities. The ferrite layer of this embodiment is easily densified without the addition of resin components such as binders or inorganic additives such as sintering aids. By minimizing the content of nonmagnetic materials, the excellent magnetic properties based on ferrite can be fully utilized.

[0044] Preferably, the ferrite layer has a film density of 4.30 g / cm³. 3 This concludes the explanation. By increasing the density of the ferrite layer, it is possible to further improve the magnetic properties and electrical insulation of the ferrite layer. Therefore, when a magnetic composite is applied to an RFID tag, the reading performance can be further improved. In contrast, a ferrite layer with low density becomes porous with internal voids. Therefore, the magnetic properties, especially the real part of the magnetic permeability (μ') and the loss coefficient (tanδ), deteriorate, and there is a risk of decreased electrical insulation. The film density is 4.50 g / cm³. 3 The above is more preferable, 4.60 g / cm³ 3 The above is even more preferable, 4.70 g / cm³ 3 The above is particularly preferred, 4.80 g / cm³ 3The above is the most preferable. There is no particular upper limit to the membrane density. However, it is typically 5.45 g / cm³. 3 The following applies:

[0045] Preferably, the ferrite layer has an arithmetic mean roughness (Ra) of 0.10 μm or more and 0.30 μm or less on its surface. By appropriately controlling the surface Ra, diffuse reflection of electromagnetic waves can be suppressed. Therefore, when the magnetic composite is applied to an RFID tag, the reading performance is further improved. Conversely, if the Ra is excessively large, diffuse reflection of electromagnetic waves increases, leading to a decrease in the reading performance of the RFID tag. Also, because the thickness of the ferrite layer becomes uneven, the electric field may concentrate locally when a high voltage is applied, potentially causing leakage current. An Ra of 0.10 μm or more and 0.25 μm or less is more preferable, and 0.10 μm or more and 0.20 μm or less is even more preferable.

[0046] Preferably, the ferrite layer has a surface resistance of 1.00 × 10⁻⁶. 9 Ω or more 1.00×10 12 It is less than Ω. Surface resistance depends on the resistance of the raw material powder. Increasing the surface resistance improves the electrical insulation of the ferrite layer, which helps to suppress problems such as eddy current generation when the magnetic composite is applied to a device. Therefore, for example, when applied to RFID tags, the reading performance is further improved. From the viewpoint of improved electrical insulation and reading performance, the surface resistance is 1.00 × 10⁻⁶. 10 Ω or more 1.00×10 12 Ω or less is more preferable, and 1.00 × 10 11 Ω or more 1.00×10 12 A value of Ω or less is even more preferable.

[0047] Preferably, the adhesion strength between the ferrite layer and the resin substrate is H or higher on the pencil hardness scale. Here, the adhesion strength on the pencil hardness scale is the maximum hardness at which peeling of the ferrite layer is not observed when evaluated using a pencil hardness test (pencil scratch test) in accordance with the old JIS K5400. Pencil hardness increases in the order of 3B, 2B, B, HB, F, H, 2H, 3H, 4H, 5H, 6H, 7H, 8H, 9H, and 10H, and higher hardness indicates better adhesion. By increasing the adhesion strength, peeling of the ferrite layer when using magnetic composites can be suppressed. An adhesion strength of 4H or higher is more preferable, 5H or higher is even more preferable, and 6H or higher is particularly preferable.

[0048] The form of the magnetic composite is not particularly limited. As shown in Figure 1, the ferrite layer (ferrite film) may be provided on the entire surface of the resin substrate. As shown in Figure 2, the ferrite layer may be provided on only a part of the surface of the resin substrate. The ferrite layer may be provided on both sides of the resin substrate, not just one side. As shown in Figure 3, the ferrite layer with partially varying thickness may be provided on the surface of the resin substrate. Furthermore, as shown in Figure 4, the ferrite layer may be wrapped around the outer circumference of a rod-shaped resin substrate.

[0049] The magnetic composite of this embodiment has a relatively thick film thickness and excellent properties such as electrical insulation. When such a magnetic composite is applied to RFID tags, especially UHF band RFID tags, good reading performance can be provided. Furthermore, the ferrite layer of the magnetic composite has good adhesion. Therefore, it is possible to prevent the ferrite layer from peeling off from the substrate and the resulting deterioration of the tag's performance.

[0050] Thus, while the magnetic composite of this embodiment is suitable for use in RFID tags, it is not limited to RFID tags. Needless to say, a magnetic composite with excellent properties such as electrical insulation and adhesion can be applied to applications other than RFID tags, such as elements or components having coil and / or inductor functions, electronic devices, housings for electronic components, electromagnetic wave absorbers, electromagnetic wave shields, or elements or components having antenna functions.

[0051] <<2. RFID Tags>> The RFID tag of this embodiment is equipped with the magnetic composite described above. The RFID tag may operate at any of the following frequencies: HF band (e.g., 13.56 MHz), UHF band (e.g., 915-928 MHz), or microwave (e.g., 2.45 GHz). However, tags used in the UHF band (UHF band RFID tags) are preferred. The RFID tag equipped with the magnetic composite of this embodiment can maintain good readability even when used under conditions of long communication distance. Furthermore, the RFID tag may be either a passive type without a power supply or an active type with a built-in power supply.

[0052] The configuration of the RFID tag can be a known embodiment. Specifically, the RFID tag comprises a magnetic composite, an IC chip, and an antenna conductor. It is preferable that the ferrite layer is in contact with or in close proximity to the antenna conductor. With this configuration, the antenna effectively receives electromagnetic waves focused on the ferrite layer, thereby further improving reading performance.

[0053] Figure 5 shows an example of the structure of an RFID tag. The RFID tag comprises a resin substrate, a ferrite layer (ferrite film) provided on one surface of the resin substrate, a metal conductor (antenna conductor) provided on one surface of the ferrite layer, and an ID tag chip (IC chip) mounted on the metal conductor. The resin substrate and the ferrite layer constitute a magnetic composite. The metal conductor provided on the surface of the ferrite layer is patterned to form an antenna pattern. The ferrite layer has a higher magnetic permeability than the surrounding space. Therefore, electromagnetic waves tend to concentrate on the ferrite layer. By providing an antenna pattern on the ferrite layer, it is possible to further improve the antenna sensitivity.

[0054] The RFID tag of this embodiment is equipped with the magnetic composite described above, that is, a magnetic composite having a relatively thick film thickness, excellent properties such as electrical insulation, and a ferrite layer with good adhesion. Therefore, it has the advantage of excellent reading performance and suppression of performance degradation due to peeling.

[0055] <<2. Method for Manufacturing Magnetic Composites>> The manufacturing method of the magnetic composite of this embodiment is not limited as long as the above requirements are satisfied. However, a preferred manufacturing method comprises the following steps: a step of preparing a resin substrate and a spinel-type ferrite powder having an average particle size (D50) of 2.5 μm or more and 10.0 μm or less (preparation step); and a step of forming a film of this ferrite powder on the surface of the resin substrate by aerosol deposition (film formation step).

[0056] Thus, by using ferrite powder with a specific particle size as a raw material and forming a film using the aerosol deposition method (AD method), a relatively thick ferrite layer can be produced at a high deposition rate. This ferrite layer is dense, has excellent properties such as electrical insulation, and exhibits excellent adhesion to the substrate. Therefore, it is suitable as a method for manufacturing magnetic composites. Each step will be described in detail below.

[0057] <Preparation process> In the preparation step, a resin substrate and spinel-type ferrite powder are prepared. Details of the resin substrate are as described above. Meanwhile, as the spinel-type ferrite powder, a powder with an average particle size (D50) of 2.5 μm or more and 10.0 μm or less is prepared. Preferably, the average particle size is 2.5 μm or more and 7.0 μm or less. By adjusting the average particle size within the above range, a dense ferrite layer with high adhesion can be obtained in the subsequent film formation step. The 10% cumulative diameter (D10) in the volume particle size distribution is preferably 0.5 μm or more and 2.0 μm or less, and the 90% cumulative diameter (D90) is preferably 8.0 μm or more and 20.0 μm or less.

[0058] The method for producing ferrite powder is not limited. However, preferably, a ferrite raw material mixture is calcined in an atmosphere with a lower oxygen concentration than that of air to produce a calcined product, and the resulting calcined product is pulverized to produce irregularly shaped particles of a specific particle size. Alternatively, the ferrite raw material mixture may be subjected to calcination, pulverization, and / or granulation treatment before calcination. Known ferrite raw materials such as oxides, carbonates, and hydroxides may be used as the ferrite raw material.

[0059] Furthermore, the CV value of the ferrite powder particle size is preferably between 0.5 and 2.5. Here, the CV value indicates the degree of variation in particle size within the powder; it is smaller the more uniform the particle size is and larger the more non-uniform it is. In general grinding methods for obtaining irregularly shaped particles (bead mills, jet mills, etc.), it is difficult to obtain powder with a CV value below 0.5. On the other hand, powder with a CV value greater than 2.5 tends to clog the piping from the raw material supply container to the nozzle. Therefore, the film deposition rate may become unstable as the film deposition time progresses. The CV value is determined according to the following equation (1) using the 10% cumulative diameter (D10), 50% cumulative diameter (D50; average particle size), and 90% cumulative diameter (D90) in the volume particle size distribution.

[0060]

number

[0061] When calcination is performed during the preparation of ferrite powder, for example, it can be done under conditions of 500-1100°C for 1-24 hours in an air atmosphere. When main calcination is performed, for example, it can be done under conditions of 800-1350°C for 4-24 hours in an atmosphere such as air or a reducing atmosphere. Furthermore, a low oxygen concentration is preferable during main calcination. This is because it is possible to intentionally create lattice defects in the spinel crystals of the ferrite powder. When lattice defects are present in the crystal, plastic deformation is more likely to occur starting from these lattice defects when the raw material particles collide with the substrate in the subsequent film formation process. Therefore, it becomes possible to easily obtain a dense ferrite layer with high adhesion.

[0062] The calcined material is preferably crushed using a grinder such as a dry bead mill. Dry grinding subjects the calcined material to mechanochemical treatment, reducing the crystallite size and increasing its surface activity. The highly surface-active powder, combined with the effect of an appropriate particle size, contributes to the densification of the ferrite layer obtained in the subsequent film formation process. By using ferrite powder with a fine crystallite size, a dense ferrite layer can be obtained.

[0063] <Film formation process> In the film formation process (deposition process), ferrite powder is deposited on the surface of the resin substrate using the aerosol deposition method (AD method). The aerosol deposition method (AD method) is a technique in which aerosolized raw material fine particles are rapidly sprayed onto the substrate, and a film is formed by the room-temperature impact solidification phenomenon. Because it utilizes the room-temperature impact solidification phenomenon, it is possible to form a dense film with high adhesion. Furthermore, since fine particles are used as the raw material, it is possible to obtain a thick film at a high deposition rate compared to thin film formation methods such as sputtering and vapor deposition, which separate the raw material to the atomic level. In addition, because film formation is possible at room temperature, there is no need to make the equipment configuration complex, which also has the effect of reducing manufacturing costs.

[0064] Figure 6 shows an example of the configuration of an aerosol deposition apparatus. The aerosol deposition apparatus (20) comprises an aerosolization chamber (2), a deposition chamber (4), a transport gas source (6), and a vacuum evacuation system (8). The aerosolization chamber (2) comprises a vibrator (10) and a raw material container (12) placed on top of it. Inside the deposition chamber (4) are a nozzle (14) and a stage (16). The stage (16) is configured to move perpendicular to the spray direction of the nozzle (14).

[0065] During film formation, a transport gas is introduced from a transport gas source (6) into a raw material container (12), and a vibrator (10) is activated. The raw material container (12) is filled with raw material fine particles (ferrite powder). The vibration mixes the raw material fine particles with the transport gas and aerosolizes them. The film formation chamber (4) is also evacuated by a vacuum exhaust system (8), reducing the pressure inside the chamber. The aerosolized raw material fine particles are transported into the film formation chamber (4) due to the pressure difference and ejected from a nozzle (14). The ejected raw material fine particles collide with the surface of a substrate (base material) placed on a stage (16) and deposit there. At this time, the kinetic energy of the raw material fine particles, which have been accelerated by gas transport, is locally released upon collision with the substrate, resulting in bonding between the substrate and particles, and between particles themselves. This makes it possible to form a dense film. By moving the stage (16) during film formation, it becomes possible to form a film that spreads in the planar direction.

[0066] The reason why a dense ferrite layer can be obtained with the manufacturing method of this embodiment is as follows: Ceramics are generally said to be materials with a high elastic limit and that are difficult to plastically deform. However, when raw material nanoparticles collide with the substrate at high speed during film formation by the aerodeposition method, a large impact force is generated that exceeds the elastic limit, so we believe that the nanoparticles undergo plastic deformation. Specifically, defects such as crystal plane displacement and dislocation movement occur inside the nanoparticles, and in order to compensate for these defects, plastic deformation occurs and the crystal structure becomes finer. In addition, new surfaces are formed and mass transfer occurs. As a result of the combined action of these factors, we believe that the bonding force between the substrate and particles, and between particles themselves, is increased, resulting in a dense film. Furthermore, we believe that during plastic deformation, a portion of the ferrite is decomposed and reoxidized, generating α-Fe2O3, which contributes to increased resistance. We also speculate that in the initial stages of film formation, nanoparticles that collide with the resin substrate penetrate into the substrate, and these penetrating nanoparticles exhibit an anchoring effect, thereby increasing the adhesion between the ferrite layer and the substrate.

[0067] The average particle size of the raw ferrite powder is important for obtaining a dense ferrite layer. In this embodiment, the average particle size (D50) of the ferrite powder is limited to 2.5 μm or more and 10.0 μm or less. If the average particle size is less than 2.5 μm, it becomes difficult to obtain a dense film. This is because powders with a small average particle size have small particle masses. Aerosolized raw material fine particles collide with the substrate at high speed along with the transport gas. The transport gas that collides with the substrate changes direction and flows as exhaust gas. Particles with small particle size and small mass are swept away by the exhaust flow of the transport gas, resulting in a small collision velocity with the substrate surface and a small impact force. If the impact force is small, the plastic deformation received by the fine particles is insufficient, and the crystallite size does not decrease. The deposited film does not become dense, and becomes a compacted powder that is merely compressed powder. Such compacted powders contain many pores and have inferior magnetic and electrical properties. Moreover, the adhesion to the substrate is not high. On the other hand, if the average particle size exceeds 10.0 μm and is excessively large, the impact force on a single particle is large, but the number of contact points between particles decreases. As a result, plastic deformation and packing become insufficient, making it difficult to obtain a dense film.

[0068] The film deposition conditions for the aerosol deposition method are not particularly limited, as long as a dense ferrite layer with high adhesion can be obtained. Air or inert gases (nitrogen, argon, helium, etc.) can be used as the transport gas. However, air is preferred because it is easy to handle.

[0069] The flow rate of the transport gas is not limited as long as the desired magnetic composite can be obtained. However, a flow rate of 6.0 L / min or more is preferred, 7.5 L / min or more is more preferred, and 10.0 L / min or more is even more preferred. If the transport gas flow rate is too low, the energy of the raw material particles upon impact with the substrate is low, and the plastic deformation of the raw material particles does not occur sufficiently during film formation. As a result, the crystallinity of the raw material particles remains, and the full width at half maximum (FWHM) of the X-ray diffraction lines of the resulting ferrite layer becomes small. If the transport gas flow rate is too high, the plastic deformation of the raw material particles occurs sufficiently during film formation, but oxidation occurs more than necessary during plastic deformation. Since a portion of the ferrite layer becomes oxide, the full width at half maximum (FWHM) of the X-ray diffraction lines of the resulting ferrite layer becomes large. Furthermore, a blasting phenomenon occurs on the substrate, and a sufficient film thickness cannot be obtained. The upper limit of the transport gas flow rate is preferably 20.0 L / min or less.

[0070] The internal pressure of the deposition chamber may be, for example, 10-50 Pa before deposition and 50-400 Pa during deposition. However, if the internal pressure during deposition is excessively low, the reading performance may be reduced when the resulting magnetic composite is applied to an RFID tag. Therefore, an internal pressure of 140 Pa or higher during deposition is preferable.

[0071] The scanning speed (movement speed) of the resin substrate (stage) may be, for example, 1.0 to 20.0 mm / second. The arithmetic mean roughness (Ra) of the ferrite layer surface depends on the scanning speed (movement speed) of the substrate (stage). By controlling the scanning speed, the surface Ra can be adjusted to an appropriate range, thereby making it possible to obtain a magnetic composite with excellent reading performance.

[0072] Furthermore, the coating (film formation) may be performed only once or multiple times, as long as the desired film thickness is obtained. However, if the ferrite layer is too thin, the reading performance may decrease when a magnetic composite containing it is applied to an RFID tag. From the viewpoint of ensuring a sufficient ferrite layer thickness, it is preferable to perform the coating multiple times. The number of coatings is, for example, 5 to 100 times, preferably 15 or more times.

[0073] In this way, the magnetic composite of this embodiment can be obtained. In the obtained magnetic composite, the ferrite layer has excellent properties such as electrical insulation. It also has high adhesion to the resin substrate. In fact, the inventors have succeeded in creating a magnetic composite with a ferrite layer having an adhesion strength of 6H on the pencil hardness scale. Moreover, although not limited to these, a magnetic composite with a thin layer of resin substrate is flexible, making it possible to create devices with complex shapes. A magnetic composite with such a ferrite layer is suitable for RFID tags, especially UHF band RFID tags. Furthermore, this magnetic composite can be applied to applications other than RFID tags, for example, elements or components having coil and / or inductor functions, electronic devices, housings for electronic components, electromagnetic wave absorbers, electromagnetic wave shields, or elements or components having antenna functions. [Examples]

[0074] The present invention will be described in more detail using the following examples. However, the present invention is not limited to the following examples.

[0075] (1) Fabrication of magnetic composites [Example 1] In Example 1, a ferrite powder mainly composed of Ni-Zn ferrite was prepared, and the obtained ferrite powder was deposited as a film on a vinyl chloride (resin) substrate to create a magnetic composite. The ferrite powder was prepared and the film was deposited under the following conditions.

[0076] <Preparation of ferrite powder> Iron oxide (Fe2O3), zinc oxide (ZnO), nickel oxide (NiO), and copper oxide (CuO) were used as raw materials. The raw materials were weighed and mixed in a molar ratio of Fe2O3:ZnO:NiO:CuO = 48.5:29.25:16:6.25. Mixing was performed using a Henschel mixer. The resulting mixture was molded using a roller compactor to obtain granules (pre-granulated material).

[0077] Next, the granulated raw material mixture (pre-granulated material) was calcined to produce a calcined product. Calcination was carried out using a rotary kiln under atmospheric conditions of 850°C for 2 hours.

[0078] Subsequently, the calcined material was crushed and granulated to produce granules (the main granules). First, the calcined material was coarsely crushed using a dry bead mill (3 / 16 inch diameter steel beads), then water was added and finely crushed using a wet bead mill (0.65 mm diameter zirconia beads) to form a slurry. The resulting slurry had a solid content concentration of 50% by mass, and the particle size of the crushed powder (slurry particle size) was 2.56 μm. Ammonium polycarboxylate was added to the obtained slurry as a dispersant at a ratio of 50 cc per 25 kg of solid content in the slurry, and then 500 cc of a 10% by mass aqueous solution of polyvinyl alcohol (PVA) was added as a binder. After that, the slurry with the added dispersant and binder was granulated using a spray dryer to obtain the main granules.

[0079] The resulting granules were then fired in an electric furnace under an oxidizing atmosphere at 1100°C for 4 hours to produce a fired product. Subsequently, the fired product was pulverized using a dry bead mill (3 / 16 inch diameter steel beads) to obtain a pulverized fired product.

[0080] <Film formation> A ferrite layer was deposited on the surface of a resin substrate using the obtained pulverized and calcined material. A 0.75 mm thick polyvinyl chloride (PVC) substrate was used as the resin substrate. This PVC substrate was colorless and transparent. The film deposition was carried out by the aerosol deposition method (AD method) under the following conditions.

[0081] - Carrier gas: Air - Gas flow rate: 7.5 L / min - Pressure inside the deposition chamber (before deposition): 30 Pa - Pressure inside the deposition chamber (during deposition): 150 Pa - Board scanning speed: 10 mm / second - Number of coatings: 10 times on each side (both sides) - Distance from substrate to nozzle: 20 mm - Nozzle shape: 10mm x 0.4mm

[0082] [Example 2] In Example 2, the number of coating applications during film formation was changed from 10 times per surface to 20 times per surface. Otherwise, the magnetic composite was fabricated in the same manner as in Example 1.

[0083] [Example 3] In Example 3, the molar ratios of the raw materials—iron oxide (Fe2O3), zinc oxide (ZnO), nickel oxide (NiO), and copper oxide (CuO)—were changed to Fe2O3:ZnO:NiO:CuO = 48.5:33:12.5:6. The conditions for calcination, granulation, and final calcination were also changed as shown in Table 1. Otherwise, the magnetic composite was fabricated in the same manner as in Example 1.

[0084] [Example 4] In Example 4, the molar ratios of the raw materials—iron oxide (Fe2O3), zinc oxide (ZnO), nickel oxide (NiO), and copper oxide (CuO)—were changed to Fe2O3:ZnO:NiO:CuO = 48:32.5:19.5:0. The conditions for calcination, granulation, and final calcination were also changed as shown in Table 1. Otherwise, the magnetic composite was fabricated in the same manner as in Example 1.

[0085] [Example 5] In Example 5, the gas flow rate during film deposition was changed to 10 L / min. This resulted in a change in the chamber pressure during film deposition. Otherwise, the magnetic composite was fabricated in the same manner as in Example 1.

[0086] [Example 6] In Example 6, the gas flow rate during film deposition was changed to 15 L / min. This resulted in a change in the chamber pressure during film deposition. Otherwise, the magnetic composite was fabricated in the same manner as in Example 1.

[0087] [Example 7 (Comparative Example)] In Example 7, a ferrite layer (ferrite-containing resin sheet) was fabricated by a coating method. Specifically, ferrite powder was prepared in the same manner as in Example 1, and 80 parts by mass of the obtained ferrite powder was dispersed and mixed with 20 parts by mass of an acrylic photocurable resin. The resulting mixture was then coated onto a PET film. The coating was performed using an applicator to obtain a coating film with a thickness of 750 μm. Next, the obtained coating film was cured with ultraviolet light to produce a magnetic sheet. The PET film was used to coat the ferrite-containing resin sheet (80 parts by mass of ferrite powder + 20 parts by mass of acrylic photocurable resin). After the ferrite-containing resin sheet was formed, the PET film was removed, and the ferrite-containing resin sheet (resin composition) alone was evaluated.

[0088] [Example 8 (Comparative Example)] In Example 8, the pulverized and calcined material obtained in Example 1 was further pulverized and refined using a wet continuous bead mill (Ashizawa Finetech Co., Ltd., Star Mill LMZ). A film was then deposited using the refined pulverized and calcined material. The magnetic composite was fabricated in the same manner as in Example 1.

[0089] [Example 9 (Comparative Example)] In Example 9, the pulverized and calcined material obtained in Example 1 was further pulverized and refined using a wet continuous bead mill (Ashizawa Finetech Co., Ltd., Star Mill LMZ). The pulverization conditions were increased compared to Example 6 to enhance the degree of refinement. A film was then deposited using the refined pulverized and calcined material. Otherwise, the magnetic composite was fabricated in the same manner as in Example 1.

[0090] [Example 10 (Comparative Example)] In Example 10, the number of coating applications during film deposition was changed from 10 times per surface to 1 time per surface. The substrate scanning speed was also changed to 20 mm / second. Otherwise, the magnetic composite was fabricated in the same manner as in Example 1.

[0091] [Example 11 (Comparative Example)] In Example 11, the gas flow rate during film deposition was changed to 1.3 L / min. This resulted in a change in the chamber pressure during film deposition. Otherwise, the magnetic composite was fabricated in the same manner as in Example 1.

[0092] [Example 12 (Comparative Example)] In Example 12, the gas flow rate during film deposition was changed to 2.5 L / min. This resulted in a change in the chamber pressure during film deposition. Otherwise, the magnetic composite was fabricated in the same manner as in Example 1.

[0093] [Example 13 (Comparative Example)] In Example 13, the gas flow rate during film deposition was changed to 5.0 L / min. This resulted in a change in the chamber pressure during film deposition. Otherwise, the magnetic composite was fabricated in the same manner as in Example 1.

[0094] [Example 14 (Comparative Example)] In Example 14, the calcined material prepared in Example 1 was crushed and classified without pulverization to obtain spherical calcined material with an average particle size of approximately 20 μm. This calcined material was then used to form a film. Otherwise, the magnetic composite was prepared in the same manner as in Example 1.

[0095] For Examples 1 to 14, the manufacturing conditions for ferrite powder and magnetic composites are summarized in Tables 1, 2, and 4.

[0096] [Table 1]

[0097] [Table 2]

[0098] (2) Evaluation For Examples 1 to 14, the various properties of ferrite powder, resin substrate, and magnetic composite were evaluated as follows.

[0099] <Particle size distribution (ferrite powder)> The particle size distribution of ferrite powder was measured as follows. First, 0.1 g of the sample and 20 ml of water were placed in a 30 ml beaker, and 2 drops of sodium hexametaphosphate were added as a dispersant. Next, the mixture was dispersed using an ultrasonic homogenizer (SMT Corporation, UH-150 model). The output level of the ultrasonic homogenizer was set to 4, and dispersion was performed for 20 seconds. After that, the bubbles formed on the surface of the beaker were removed, and the mixture was introduced into a laser diffraction particle size distribution analyzer (Shimadzu Corporation, SALD-7500nano) for measurement. From this measurement, the 10% cumulative diameter (D10), 50% cumulative diameter (D50; average particle size), and 90% cumulative diameter (D90) in the volume particle size distribution were determined. The measurement conditions were a pump speed of 7, an internal ultrasonic irradiation time of 30, and a refractive index of 1.70-050i.

[0100] <True specific gravity (ferrite powder)> The true specific gravity of the ferrite powder was measured by the gas displacement method in accordance with JIS Z8837:2018.

[0101] <Magnetic properties (ferrite powder)> The magnetic properties (saturation magnetization, remanent magnetization, and coercivity) of ferrite powder were measured as follows. First, the sample was packed into a cell with an inner diameter of 6 mm and a height of 2 mm, and set in a vibrating sample magnetic measuring device (Toei Kogyo Co., Ltd., VSM-C7-10A). An applied magnetic field was swept up to 5 kOe, and then the applied magnetic field was decreased to generate a hysteresis curve. From the data of the obtained curve, the saturation magnetization (σs), remanent magnetization (σr), and coercivity (Hc) of the sample were determined.

[0102] <Thickness (resin substrate, ferrite layer)> The cross-sections of the resin substrate and the ferrite layer were observed using a field emission scanning electron microscope (FE-SEM), and images were obtained under conditions of an acceleration voltage of 1.0 kV and a magnification of 1000x. The thickness of the substrate and the ferrite layer was determined at 10 arbitrary points in the obtained images, and the average of these values ​​was used to determine the thickness. For samples in which ferrite layers were deposited on both sides of the substrate, the thickness of the front and back surfaces were determined separately, and the sum of these values ​​was used to determine the thickness (d F) was used.

[0103] <Film density (ferrite layer)> The density of the ferrite layer was measured as follows. First, the mass of the resin substrate alone before forming the ferrite layer was measured. Next, the mass of the resin substrate after forming the ferrite layer was measured, and the difference from the mass of the resin substrate alone was calculated to obtain the mass of the ferrite layer. Also, the film formation area and film thickness of the ferrite layer were measured. The film thickness was determined by observing the cross-section of the ferrite layer with a scanning electron microscope (SEM). Then, the density of the ferrite layer was calculated according to the following formula (2).

[0104]

Number

[0105] <Surface roughness (resin substrate, ferrite layer)> Using a laser microscope (Lasertec Corporation, OPTELICS HYBRID), the arithmetic mean roughness (Ra) of the surfaces of the resin substrate and the ferrite layer was evaluated. For each sample, 10 measurements were performed, and the average value was obtained. The measurements were carried out in accordance with JIS B 0601-2001.

[0106] <XRD (ferrite layer)> For the ferrite layer, analysis by X-ray diffraction (XRD) method was performed. And in the X-ray diffraction profile obtained by the analysis, the full width at half maximum (FWHM) of the diffraction line (I 311 ) based on the (311) plane of the spinel-type crystal phase was determined. The analysis conditions were as shown below.

[0107] -X-ray diffractometer: PANalytical, X’pert MPD (including high-speed detector) -Radiation source: Co-Kα -Tube voltage: 45 kV -Tube current: 40 mA -Scan speed: 0.002° / second (continuous scan) -Scan range (2θ): 15~90°

[0108] <Surface resistance (resin substrate, ferrite layer)> The surface resistance of both the resin substrate and the ferrite layer was measured using a resistivity meter (Mitsubishi Chemical Corporation, Hiresta IP, MCP-HT260). Specifically, a voltage of 100V was applied, and the surface resistance was measured. Ten measurements were taken for each sample, and the average value was calculated.

[0109] <Adhesion (pencil hardness; magnetic composite)> The adhesion between the ferrite layer and the resin substrate was evaluated using a pencil hardness test (pencil scratch test). The measurement was performed in accordance with the old JIS K5400 standard. In each test, the pencil was scratched five times with a pencil of the same hardness rating. The tip of the pencil lead was sharpened after each scratch. Pencil hardness increases in the order of 3B, 2B, B, HB, F, H, 2H, 3H, 4H, 5H, 6H, 7H, 8H, 9H, and 10H, with higher hardness indicating better adhesion.

[0110] <Adhesion (cross-cut; magnetic composite)> The adhesion between the ferrite layer and the resin substrate of a magnetic composite (substrate thickness 750 μm) was evaluated using the cross-cut method. Measurements were performed in accordance with JIS K5600-5-6:1999. Based on the evaluation results, the samples were graded according to the following criteria.

[0111] A: The edges of the cuts are perfectly smooth, and there is no peeling in any of the grid lines. B: Small paint peeling occurs at the intersection of the cuts. The number of affected areas at the cross-cuts does not clearly exceed 5%. C: The paint film is peeling along the edges of the cuts and / or at the intersections. The number of affected areas in the cross-cuts clearly exceeds 5%, but never exceeds 15%. D: The paint film is partially or completely peeled along the edges of the cuts, and / or partially or completely peeled in various parts of the grain. The number of affected areas in the cross-cut is clearly more than 15%, but not more than 35%. E: The paint film is partially or completely peeled along the edges of the cuts, and / or partially or completely peeled in several places. The number of affected areas in the cross-cuts does not clearly exceed 65%. F: The degree of peeling cannot be classified into categories A-E.

[0112] <Antenna performance> A magnetic composite (substrate + ferrite layer) was used to attach an RFID label, and the maximum response distance to an antenna in the UHF band was measured. Specifically, the maximum communication distance in the UHF band was measured in an anechoic chamber for both the magnetic composite and the substrate, and the degree of improvement in communication distance when using the magnetic composite compared to when using only the substrate was calculated as the rate of change in communication distance.

[0113] - Evaluation equipment: Voyantic, Tag Performance Pro - RFID label: Alien Technology, ALN-9816 Pearl - Test frequency: 600-1200MHz

[0114] (3) Evaluation results For Examples 1 to 14, the properties of the ferrite powder and the resin substrate are shown in Tables 3 and 4, respectively. The properties of the magnetic composite are shown in Table 5. In Table 5, the surface resistance is expressed in E notation. That is, the number before "E" represents the mantissa, and the number after "E" represents the exponent.

[0115] As shown in Table 3, the ferrite powders used for film formation in Examples 1-7 and 10-14 had relatively large average particle sizes (D50) of 4.1 μm or more. Furthermore, the true specific gravity was 5.47 g / cm³. 3The ferrite powders exhibited high levels of saturation magnetization (σs; 50.8 emu / g or higher). This indicates that the ferrite reaction proceeded sufficiently in these ferrite powders. Note that the σs of the ferrite powder in Example 3 was slightly lower at 50.8 emu / g, while the σs of the ferrite powder in Example 4 was higher at 59.5 emu / g. This is thought to be due to the different compositions of these ferrite powders compared to the other samples.

[0116] In contrast, the ferrite powders in Examples 8 and 9 have a D50 (1.5~1.8 μm) and a true specific gravity (5.38~5.41 g / cm³). 3 ), and σs (47.8~48.7 emu / g) were relatively small. It is thought that the magnetic properties deteriorated because the crushed and calcined material was further crushed to make it finer, resulting in smaller particle sizes and added crystal strain.

[0117] As shown in Table 5, the magnetic composites of Examples 1-6 have a ferrite layer thickness (d F The film thickness (5.7~16.4 μm) and the full width at half maximum (FWHM; 1.0340~1.1520°) of the X-ray diffraction lines satisfied the requirements of this embodiment. Furthermore, a strong peak based on the spinel-type crystalline phase was observed in the X-ray diffraction profile, indicating that the spinel-type crystalline phase was the matrix phase. In addition, the film density (4.53~4.81 g / cm³) was also found. 3 ) and surface resistance (9.23 × 10 10 These magnetic composites exhibited high magnetic density (Ω or higher) and excellent adhesion (pencil hardness of 5H or higher). Furthermore, they showed a high rate of change in RFID tag communication distance (124-137%) and superior reading performance.

[0118] In contrast, in Example 7, which was fabricated using a coating method, a ferrite layer (ferrite-containing resin sheet) with a large film thickness (750 μm) was obtained, but the FWHM of the obtained ferrite layer was very small at 0.1303°. Furthermore, the rate of change in communication distance was remarkably small at 67%, and the adhesion of the ferrite layer was also poor. It is thought that the large amount of non-magnetic resin resulted in poor magnetic properties, and the low FWHM contributed to the decrease in communication distance (reading performance).

[0119] In Examples 8 and 9, where films were formed using strongly pulverized and calcined materials, a dense ferrite layer could not be obtained. Specifically, the ferrite layer became compacted powder, resulting in a film density of (0.59~0.72 g / cm³). 3 The ) and FWHM (0.5780~0.5980°) were small. As a result, the rate of change in communication distance was small, at 97~99%, indicating poor adhesion of the ferrite layer.

[0120] In Example 10, where the number of coatings during film deposition was small (1), although the FWHM was sufficient at 1.0300°, only a ferrite layer with a thickness of 0.38 μm was obtained. As a result, the communication distance change rate was small at 101%. In Examples 11-13, where the gas flow rate during film deposition was reduced to 1.3-5.0 L / min, only ferrite layers with low FWHMs of 0.8000-0.9840° were obtained, and the communication distance change rate of these ferrite layers remained at 100-104%.

[0121] In Example 14, where a film was deposited using spherical calcined material with an average particle size of approximately 20 μm, a ferrite layer could not be obtained. Specifically, the deposition of the ferrite layer did not proceed, and etching of the substrate occurred. As a result, the communication distance change rate was 99%, resulting in reading performance that was almost identical to that measured with the substrate alone.

[0122] From the above results, it can be seen that the magnetic composite of this embodiment, in which the ferrite layer thickness and FWHM are limited to a predetermined range, has a relatively thick film, excellent properties such as electrical insulation, and good adhesion. Furthermore, it is understood that RFID tags equipped with this magnetic composite have excellent reading performance.

[0123] [Table 3]

[0124] [Table 4]

[0125] [Table 5] [Explanation of Symbols]

[0126] 2. Aerosolization Chamber 4. Film deposition chamber 6. Conveying gas source 8. Vacuum Exhaust System 10 Vibrator 12 Raw material container 14 nozzles 16 stages 20 Aerosol Deposition Film Forming Apparatus

Claims

1. A magnetic composite comprising a resin substrate and a ferrite layer provided on the surface of the resin substrate, The ferrite layer has a spinel-type crystalline phase as its matrix, and a thickness (d Ｆ The ) is 2.0 μm or larger, and in X-ray diffraction analysis using Co-Kα as the radiation source, the diffraction line based on the (311) plane of the spinel-type crystal phase (I ３１１ A magnetic composite having a full width at half maximum (FWHM) of 1,000° or more and 1,200° or less.

2. The magnetic composite according to claim 1, wherein the ferrite layer contains iron (Fe) and oxygen (O), and further contains at least one element selected from the group consisting of transition metal elements other than iron (Fe), lithium (Li), magnesium (Mg), and aluminum (Al).

3. The aforementioned resin substrate has a thickness (d Ｒ The magnetic composite according to claim 1 or 2, wherein the diameter of the ) is 10.0 μm or more.

4. The magnetic composite according to claim 1 or 2, wherein the ferrite layer has an arithmetic mean roughness (Ra) of its surface of 0.10 μm or more and 0.30 μm or less.

5. The ferrite layer has a surface resistance of 1.00 × 10 ９ Ω or more 1.00×10 １２ A magnetic composite according to claim 1 or 2, wherein the ohm value is less than or equal to Ω.

6. An RFID tag comprising the magnetic composite according to claim 1 or 2.

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