Resin molded body

Abstract

This resin molded body includes resin and a coil-shaped conductive member. At least a part of the coil shape is in a tapered shape in which a coil radius gradually increases or decreases. A minimum value of the coil radius is 5.0 μm or more, and a maximum value of the coil radius is 1000.0 μm or less.

Description

Resin molding

[0001] The present disclosure relates to a resin molded article.

[0002] Communication devices such as mobile phones and smartphones enable wireless communication using electromagnetic waves, and with technological advances in this field, the frequency bands of the electromagnetic waves used have been expanding. Specifically, wireless communication systems complying with the IMT-Advanced standard established by the International Telecommunication Union (ITU) are specified, and the frequency band of first-generation mobile communication systems (1G) was approximately 800 MHz, but in fourth-generation mobile communication systems (4G), the frequency band has been expanded to approximately 3 GHz. Furthermore, in the currently adopted fifth-generation mobile communication systems (5G), the frequency band has been expanded to the 28 GHz band to achieve higher speeds, larger capacity, lower latency, and multiple connections. Furthermore, development of sixth-generation mobile communication systems (6G), which use frequency bands of 100 GHz or higher, is currently underway as the next-generation communication system. While the use of electromagnetic waves in high frequency bands has attracted attention, the increasing frequency of electromagnetic waves increases the likelihood of electronic device malfunctions, communication disruptions, information leaks, and health problems, necessitating the control of electromagnetic noise (EMC). Specifically, there is a demand for the development of new materials capable of suppressing both EMI (the cause of the problem) and EMS (the cause of the problem of immunity). One approach to solving this problem is the use of electromagnetic wave control materials that can reduce the effects of electromagnetic waves from the surrounding environment. Electromagnetic wave control materials are available in a variety of forms, including semiconductor packages / modules, housings for electrical / electronic devices, adhesives for semiconductor mounting boards or cables, wallpaper for buildings such as server rooms, and clothing such as aprons for protecting the human body.

[0003] There are various types of electromagnetic wave control materials, and extensive research is underway. Examples include reflective materials that reflect electromagnetic waves by using large metal plates, and absorptive materials that absorb electromagnetic waves by using materials in which conductive materials are mixed with organic materials such as resins and rubbers. For example, research on absorptive materials has shown that using substances with structures one order of magnitude smaller than the wavelength of the electromagnetic waves to be shielded is effective, and materials containing small fillers are being developed as a means of forming such structures. Patent Document 1 discloses a sheet that has excellent electromagnetic wave shielding performance at a frequency of 1 GHz, and is made of a composite having an insulating layer and a conductive layer in which a binder resin contains flaky silver powder with a specific particle size and bulk density. Patent Document 2 also discloses a sheet that can shield electromagnetic waves in the frequency range of 1 MHz to 1 GHz, and is made of a composite in which a binder resin contains ferrite particles that are single-crystal and spherical in shape and have a specific average particle size. Furthermore, Patent Document 3 discloses a sheet made of a composite in which a binder resin contains a specific amount or more of nickel nanowires, which has excellent handleability and flexibility and can shield electromagnetic waves in the frequency band of 18.0 to 26.5 GHz.

[0004] On the other hand, the sheets disclosed in Patent Documents 1 to 3 have a problem in that they cannot handle electromagnetic waves in the frequency band of next-generation wireless communication systems, which is an order of magnitude or more greater than the frequency band used in conventional wireless communication systems. To solve this problem, a sheet using a coil-shaped conductive member is being developed, as disclosed in Patent Document 4.

[0005] JP 2011-86930 A, WO 2017 / 212997 A, JP 2019-67997 A, WO 2022 / 009960 A

[0006] Methods for shielding electromagnetic waves using electromagnetic shielding materials include methods that reduce electromagnetic waves transmitted through the electromagnetic shielding material by absorbing or reflecting them. Materials using coil-shaped conductive materials, such as those disclosed in Patent Document 4, are materials with excellent electromagnetic wave absorption shielding performance, and development has focused on absorption performance. On the other hand, development of shielding materials using coil-shaped conductive materials that focus on electromagnetic wave reflection has not been sufficient, leaving room for improvement. When electromagnetic waves are reflected by a shielding material, the amount of electromagnetic waves transmitted through the shielding material is reduced, but there is concern that the reflected electromagnetic waves may strike electronic devices and cause malfunctions. Simply improving the electromagnetic wave shielding performance can be achieved by increasing the electromagnetic wave absorption rate and reflectance of the shielding material. However, to achieve excellent shielding performance while avoiding problems such as electronic device malfunctions, it is necessary to develop a material that maintains a high electromagnetic wave absorption rate while having a low electromagnetic wave reflectance.

[0007] Therefore, the present disclosure provides a resin molded article that has a high electromagnetic wave absorption rate and a low reflectance rate, and is capable of shielding electromagnetic waves in the high frequency band.

[0008] As a result of extensive research, the present inventors have found that the above-mentioned problems can be solved by using a coil-shaped conductive member having a specific structure, and have arrived at the invention disclosed herein.

[0009] That is, the present disclosure has the following features. [1] A resin molded product comprising a resin and a coil-shaped conductive member, wherein at least a portion of the coil shape is a tapered shape in which the coil radius gradually increases or decreases, the minimum value of the coil radius is 5.0 μm or more, and the maximum value of the coil radius is 1000.0 μm or less. [2] The resin molded product according to [1], wherein the height of the conductive member is 10.0 μm or more and 1000.0 μm or less. [3] The resin molded product according to [1] or [2], wherein the thickness of the wire constituting the coil shape is more than 0.5 μm and 20.0 μm or less. [4] The resin molded product according to any of [1] to [3], wherein the ratio of the maximum value of the coil radius to the height of the conductive member is 0.5 or more and 10.0 or less. [5] The resin molded product according to any of [1] to [4], wherein the number of the conductive members included in the resin molded product is two or more. [6] The resin molded product according to [5], wherein the distance between the central axes of the coil shapes of adjacent conductive members is 5.0 μm or more and 1000.0 μm or less. [7] The resin molded product according to [5] or [6], wherein the winding direction of the coil shape of at least a part of the conductive members is different from the winding direction of any one of the conductive members adjacent to the conductive member. [8] The resin molded product according to any of [1] to [7], which is in the form of a sheet. [9] The resin molded product according to [8], which is an electromagnetic wave shielding sheet.

[0010] The present disclosure makes it possible to provide a resin molded article that has high electromagnetic wave absorption and low reflectance and is capable of shielding electromagnetic waves in the high frequency band.

[0011] FIG. 1 is a diagram schematically showing one embodiment of a conductive member. FIG. 2 is a diagram for explaining the coil radius of the conductive member. FIG. 3 is a diagram for explaining the form of the conductive member. FIG. 4 is a diagram schematically showing an experimental apparatus for evaluating electromagnetic wave shielding properties. FIG. 5 is a diagram schematically showing one embodiment of a resin sheet having a C-shaped conductive member and a columnar conductive member connected to an end of the C-shape. FIG. 6 is a diagram schematically showing one embodiment of a laminated sheet obtained by laminating resin sheets having a C-shaped conductive member and a columnar conductive member connected to an end of the C-shape. FIG. 7 is a diagram schematically showing the basic form of a resin molded body used in simulation experiments in Examples 1 and 2. FIG. 8 is a diagram schematically showing the basic form of a resin molded body used in simulation experiments in Example 3. FIG. 9 is a diagram schematically showing the basic form of a resin molded body used in simulation experiments in Comparative Example 1 and Reference Example 2. FIG. 10 is a diagram showing the evaluation results of the electromagnetic wave shielding properties of the resin molded body in Example 1. FIG. 11 is a diagram showing the evaluation results of the electromagnetic wave shielding properties of the resin molded body in Comparative Example 1. FIG. 12 is a diagram showing the evaluation results of the electromagnetic wave shielding properties of the resin molded body in Example 2. 10 is a diagram showing the evaluation results of the electromagnetic wave shielding properties of the resin molding in Example 3. FIG.

[0012] The embodiments of the present disclosure are described in detail below. However, each configuration and combination thereof in each embodiment is merely an example, and additions, omissions, substitutions, and other modifications of configurations are possible as appropriate within the scope of the present disclosure. The present disclosure is not limited by the embodiments, but only by the scope of the claims. In this disclosure, a numerical range expressed using "to" means a range including the numerical values ​​before and after "to" as the lower and upper limits, and "A to B" means A or greater and B or less. In addition, while multiple embodiments are described in this disclosure, various conditions in each embodiment may be applied to each other to the extent applicable. In addition, the expression "A or B" in this disclosure can be interpreted as "at least one selected from the group consisting of A and B." In addition, in this disclosure, "multiple" means "two or more." The dimensions, materials, shapes, relative arrangements, etc. of the components described in this disclosure are merely examples.

[0013] <Resin molded body> A resin molded body (hereinafter also simply referred to as "resin molded body") according to one embodiment of the present disclosure is a resin molded body including a resin and a coil-shaped conductive member, wherein at least a portion of the coil shape is a tapered shape in which the coil radius gradually increases or decreases, and the minimum value of the coil radius is 5.0 μm or more and the maximum value of the coil radius is 1000.0 μm or less.

[0014] The inventors have focused on developing a coil-shaped conductive material as a structure capable of absorbing strong electromagnetic waves in the terahertz region. The coil shape can be considered as a series of connected pseudo-C-shaped plane structures, and by considering these as a circuit, it has been found that an electromagnetic wave absorption effect can be achieved through LC resonance, with the coil shape itself as inductance L and the gap as capacitance C. It has also been found that absorption can be achieved through the resonance effect of a magnetic field entering the coil.

[0015] In the technical field, when a molded article containing a coil-shaped conductive member is used as an electromagnetic wave shielding molded article, a conductive member with a constant coil radius has conventionally been used. After extensive research, the inventors discovered that by using the above-described conductive member, at least a portion of which is tapered, instead of the conventional conductive member, a resin molded article can be obtained that maintains high electromagnetic wave absorption while exhibiting low electromagnetic wave reflectance. The inventors speculate that this is because the coil diameter gradually changes, causing the coil's response to electromagnetic waves to differ depending on the position in the thickness direction of the structure, thereby achieving a condition in which electromagnetic waves reflected from the lower and upper surfaces of the coil cancel each other out. Therefore, by using the resin molded article according to this embodiment, it is possible to shield high-frequency electromagnetic waves while reducing problems such as malfunction of electronic devices due to electromagnetic wave reflection.

[0016] Furthermore, in the above-described embodiment, a lightweight material such as a polymeric material can be used as the binder for the conductive member, making it easier to reduce the weight compared to conventional electromagnetic wave shielding members that use metal plates. Furthermore, when using a metal plate, electromagnetic waves are generally reflected by the metal surface, making it difficult to reduce reflection. On the other hand, in the above-described embodiment, a polymeric material or the like can be used as the binder for the conductive member, which is easy to prevent reflection of electromagnetic waves and also easy to absorb electromagnetic waves. Therefore, the above-described embodiment makes it easy to suppress reflection of electromagnetic waves from the perspective of materials as well.

[0017] Conventionally, metal cases, primarily stainless steel cases, have been used as electromagnetic wave shielding materials in semiconductor modules. Such stainless steel cases can shield external electromagnetic waves by reflecting them. While reflection can block the entry and exit of electromagnetic waves, the presence of multiple semiconductor elements within the case raises the risk of electromagnetic waves radiated from the semiconductor elements being diffused within the case, potentially causing malfunctions in adjacent semiconductor elements. Furthermore, stainless steel cases are conductive, and in order to prevent the aforementioned short circuit, they must be installed so as not to come into contact with exposed terminals, limiting their space-saving potential. When a conventional stainless steel case is replaced with a resin molded product according to the present embodiment, the resin molded product is an absorber, making it less likely to cause diffuse reflections within the case and reducing the risk of malfunction. Furthermore, its high resistance allows it to be used in contact with exposed terminals, facilitating space savings. Furthermore, the resin molded product according to the present embodiment can be molded by coating or spraying, allowing it to adhere closely to multiple semiconductor elements, including their terminals, thereby achieving extreme space savings while maintaining its absorber performance.

[0018] [Conductive Member] (Configuration of Conductive Member) The conductive member is a coil-shaped member. In the present disclosure, a coil shape refers to a shape formed by lines extending in the direction of the central axis while surrounding the central axis, or a shape formed by lines surrounding the central axis and lines extending in the direction of the central axis. The shape of the conductive member as viewed in the direction of the central axis is not particularly limited, and may be a circle, or a polygon such as a triangle, a square, or a pentagon, or any other shape. The central axis of the conductive member may be a straight line, a curved line, or a line of any shape.

[0019] At least a portion of the coil shape constituting the conductive member has a tapered shape in which the coil radius gradually increases or decreases. The coil shape constituting the conductive member may be partially tapered, or may be entirely tapered. Specifically, a tapered shape refers to a shape in which, in a coil shape with n turns, the coil radius of the kth turn is smaller than the coil radius of the k-1th turn. Here, n represents an integer of 3 or greater, and k represents an integer satisfying 1≦k≦n. Furthermore, the orientation of the coil shape is not limited, and it is sufficient to satisfy the relationship that, when a turn at either end of the coil shape is the first turn, the coil radius of the kth turn is smaller than the coil radius of the k-1th turn.

[0020] Specific examples of the conductive member include those shown in Fig. 1. Examples of the conductive member include a spiral shape as shown in Fig. 1(a) and (b), and a shape composed of a plurality of C-shaped structures and a columnar structure connecting the plurality of C-shaped structures in the central axis direction as shown in Fig. 1(c) and (d). Specifically, Fig. 1(c) and (d) are shapes formed by repeating a structure in which a columnar end is connected to an end of a C-shape, and further, another C-shaped end is connected to the other end of the columnar shape, resulting in a coil shape as a whole.

[0021] The conductive member in FIG. 1( a) and the conductive member in FIG. 1( b) have different orientations, but both are conductive members having an overall tapered shape. In the case of the conductive member in FIG. 1( a), the winding at the end on the X side is the nth winding, and the winding at the end on the Y side is the first winding. In the case of the conductive member in FIG. 1( b), the winding at the end on the Y side is the nth winding, and the winding at the end on the X side is the first winding. Similarly, in the case of the conductive member in FIG. 1( c), the winding at the end on the X side is the nth winding, and the winding at the end on the Y side is the first winding. In the case of the conductive member in FIG. 1( d), the winding at the end on the Y side is the nth winding, and the winding at the end on the X side is the first winding.

[0022] When the coil shape of the conductive member is a shape composed of multiple C-shaped structures and columnar structures connecting the multiple C-shaped structures in the central axis direction, as shown in FIGS. 1(c) and 1(d), the form is not particularly limited. For example, as described in the manufacturing method described below, the C-shaped structures may be made of a conductive thin film, and the columnar structures connecting the multiple C-shaped structures may be made of a columnar conductive member. The C-shape may be a circular ring with a portion missing, as shown in FIGS. 1(c) and 1(d), or the ring may be a polygonal shape such as a triangle or a square, with a portion missing. However, from the viewpoints of availability and ease of manufacturing, a circular ring with a portion missing is preferred. In either form, as long as it has a central axis, the effect of absorbing electromagnetic waves through LC resonance based on external electromagnetic waves can be obtained. The columnar shape is not particularly limited and may be a cylindrical shape or a polygonal shape such as a triangular prism or a square prism. However, from the viewpoints of availability and ease of manufacturing, a cylindrical shape is preferred. The C-shaped structural portion and the columnar structural portion may be made of the same material or different materials, but from the viewpoint of reducing manufacturing costs, it is preferable that they are made of the same material.

[0023] The coil radius in a tapered shape will be explained using FIG. 2. FIG. 2 is a diagram of a coil shape with four turns observed from a direction perpendicular to the central axis C. When the coil shape is viewed from a direction perpendicular to the central axis C, the tapered shape has a configuration as shown in FIG. 2, which is composed of multiple line segments. Specifically, the tapered shape in FIG. 2 is composed of a line segment connecting points (PA-4) and (PB-4), a line segment connecting points (PB-4) and (PA-3), a line segment connecting points (PA-3) and (PB-3), a line segment connecting points (PB-3) and (PA-2), a line segment connecting points (PA-2) and (PB-2), a line segment connecting points (PB-2) and (PA-1), and a line segment connecting points (PA-1) and (PB-1). In this case, when the tapered shape is viewed from a direction perpendicular to the central axis C, if the distance between a line (LA-4) passing through point (PA-4) and parallel to the central axis and a line (LB-4) passing through point (PB-4) and parallel to the central axis is D-4, the coil radius for the fourth winding is (D-4) / 2. Similarly, the coil radius for the third winding is half ((D-3) / 2) of the distance between the line (LA-3) passing through point (PA-3) and parallel to the central axis and the line (LB-3) passing through point (PB-3) and parallel to the central axis, the coil radius for the second winding is half ((D-2) / 2) of the distance between the line (LA-2) passing through point (PA-2) and parallel to the central axis and the line (LB-2) passing through point (PB-2) and parallel to the central axis, and the coil radius for the first winding is half ((D-1) / 2) of the distance between the line (LA-1) passing through point (PA-1) and parallel to the central axis and the line (LB-1) passing through point (PB-1) and parallel to the central axis.

[0024] The minimum coil radius refers to the minimum coil radius in one tapered shape. That is, in FIG. 2, (D-1) / 2 is the minimum coil radius. The minimum coil radius is 5.0 μm or more from the viewpoint of ensuring sufficient electromagnetic wave shielding properties. Furthermore, from the viewpoint of ensuring a higher level of electromagnetic wave shielding properties, the minimum coil radius is preferably 20.0 μm or more, more preferably 40.0 μm or more, even more preferably 50.0 μm or more, and particularly preferably 80.0 μm or more. Furthermore, from the viewpoint of ensuring a higher level of electromagnetic wave shielding properties, the minimum coil radius is preferably 500.0 μm or less, more preferably 450.0 μm or less, even more preferably 400.0 μm or less, particularly preferably 300.0 μm or less, and even more particularly preferably 200.0 μm or less. The minimum value of the coil radius may be, for example, 5.0 μm or more and 500.0 μm or less, 20.0 μm or more and 450.0 μm or less, 40.0 μm or more and 400.0 μm or less, 50.0 μm or more and 300.0 μm or less, or 80.0 μm or more and 200.0 μm or less. In this specification, unless otherwise specified, parameters are treated as their average values. For example, when multiple conductive members are included in the resin molded body, the "minimum value of the coil radius" means the "average value of the minimum values ​​of the coil radii of the multiple conductive members." This also applies to other parameters. The same applies to the examples. For example, the number of turns of the coil shape in Experiment B of the example is 32.8, which is also an average value.

[0025] The maximum coil radius refers to the maximum coil radius in one tapered shape. That is, in FIG. 2, (D-4) / 2 is the maximum coil radius. From the viewpoint of ensuring a higher level of electromagnetic wave shielding properties, the maximum coil radius is preferably 40.0 μm or more, more preferably 60.0 μm or more, even more preferably 80.0 μm or more, and particularly preferably 100.0 μm or more. Furthermore, from the viewpoint of ensuring sufficient electromagnetic wave shielding properties, the maximum coil radius is 1000.0 μm or less. Furthermore, from the viewpoint of ensuring a higher level of electromagnetic wave shielding properties, the maximum coil radius is preferably 700.0 μm or less, more preferably 500.0 μm or less, and even more preferably 300.0 μm or less. The maximum value of the coil radius may be, for example, 40.0 μm or more and 1000.0 μm or less, 60.0 μm or more and 700.0 μm or less, 80.0 μm or more and 500.0 μm or less, or 100.0 μm or more and 300.0 μm or less.

[0026] The increase or decrease in the coil radius is not particularly limited, but from the viewpoint of more highly exhibiting the reflectivity reduction effect, it is preferably 0.5 μm or more, more preferably 1.0 μm or more, even more preferably 2.0 μm or more, and particularly preferably 3.0 μm or more. Also, from the viewpoint of more highly exhibiting the reflectivity reduction effect, it is preferably 100.0 μm or less, more preferably 50.0 μm or less, even more preferably 30.0 μm or less, and particularly preferably 20.0 μm or less. The increase or decrease in the coil radius may be, for example, 0.5 μm or more to 100.0 μm or less, 1.0 μm or more to 50.0 μm or less, 2.0 μm or more to 30.0 μm or less, or 3.0 μm or more to 20.0 μm or less. The increase or decrease is the difference in the radius of adjacent coils, and in FIG. 2, for example, it is a value expressed as (D-2) / 2-(D-1) / 2.

[0027] The number of tapered shapes included in the coil shape constituting one conductive member is not particularly limited, and may be 1 or more, 2 or more, 3 or more, or 6 or less, 5 or less, or 4 or less. The number of tapered shapes may be, for example, 1 to 6, 2 to 5, or 3 to 4. Examples of cases where there are multiple tapered shapes include, when two tapered shapes are considered, a configuration in which the small diameter side of one tapered shape is connected to the large diameter side of the other tapered shape, a configuration in which the large diameter side of one tapered shape is connected to the large diameter side of the other tapered shape, and a configuration in which the two tapers are connected in a non-tapered shape.

[0028] One embodiment of the conductive member is shown in Figure 3. Figure 3 is a diagram of two conductive members observed from a direction perpendicular to the central axis direction of the coil shape constituting the conductive member. In Figure 3, C is the central axis, Dmax is the maximum coil diameter (twice the maximum coil radius), Dmin is the minimum coil diameter (twice the minimum coil radius), H is the height of the conductive member, P is the coil pitch of the coil shape, W is the thickness of the wire constituting the coil shape, and M is the distance between the central axes of the coil shapes of adjacent conductive members. These parameters can be measured by internal observation using CT-X-rays.

[0029] The cross-sectional shape of the wires constituting the coil is not particularly limited, and may be, for example, a circle or a polygon such as a triangle or a rectangle.

[0030] The type of material for the conductive member is not particularly limited as long as it is conductive. Examples include carbon materials such as carbon; alloys of combinations of metal elements such as copper (Cu), aluminum (Al), iron (Fe), gold (Au), silver (Ag), platinum (Pt), magnesium (Mg), zinc (Zn), tungsten (W), titanium (Ti), nickel (Ni), or manganese (Mn); and metal-containing compounds such as oxides, halides, or sulfides of these metal elements or alloys. The conductive member may also be a composite material containing these conductive materials in a resin, or may be a coil-shaped resin having a thin metal film formed on the surface by plating or other treatment. Among these, copper (Cu), iron (Fe), or tungsten (W) are preferred as the material for the conductive member, with tungsten (W) being particularly preferred, because they have a modulus of elasticity suitable for coil processing, good corrosion resistance when incorporated into a resin, and a small coefficient of linear expansion, resulting in good durability of the resin molded body. Furthermore, from the viewpoint of being able to be manufactured using a 3D printer, an embodiment using a composite material in which a conductive material is contained in a resin, or an embodiment in which a metal thin film is provided on the surface of a coil-shaped resin by a process such as plating, is preferred. When a resin is used as the material for the conductive member, the type of resin is not particularly limited, and the type of resin constituting the matrix of the resin molded body described below can be used in the same way, but it is preferable that the type of resin used as the material for the conductive member is different from the type of resin constituting the matrix of the resin molded body.

[0031] The conductive members may be made of a single metal or alloy, or may have a plated coating formed on their surfaces. Furthermore, to minimize short circuits between the conductive members, the surfaces may be coated with insulating resin, or an oxide film may be formed on the surfaces. For example, the oxide film can be formed by subjecting the conductive members to high-temperature heat treatment.

[0032] The number of conductive members in the resin molded body is not particularly limited, but from the viewpoint of ensuring a higher level of electromagnetic wave shielding performance, it is usually 50 pieces / cm ３ or more, and 100 particles / cm ３ It is preferable that the number of particles is 200 or more per cm.３ More preferably, it is 300 particles / cm or more. ３ More preferably, it is 10,000 particles / cm or more. ３ 5000 particles / cm or less ３ Preferably, the number of particles is 3000 or less per cm ３ More preferably, it is 2000 particles / cm or less. ３ It is more preferable that the number of conductive members is not more than: The number of conductive members can be measured by internal observation using CT-X-rays.

[0033] The content of the conductive member in the resin molded body is not particularly limited, and can be appropriately designed depending on the material of the conductive member.

[0034] The arrangement of the conductive members is not particularly limited and may be randomly arranged, but is preferably arranged in a periodic structure. In the present disclosure, the periodic structure refers to an arrangement in which the conductive members are aligned and arranged in the resin molded body, more specifically, an arrangement in which the conductive members are arranged at periodic intervals in the resin. The arrangement is not particularly limited, and examples include an arrangement in which the conductive members are aligned to form a circle or a polygon such as a triangle or a square. This aligned arrangement may be configured in one stage or in two or more stages. Furthermore, when a resin molded body is configured by stacking multiple layers, the arrangement of the conductive members in each layer can be set arbitrarily. For example, the arrangement of the conductive members in all layers may be random, or the arrangement of the conductive members in all layers may be configured in a periodic structure, or a laminate combining these arrangements may be used.

[0035] The height H of the conductive member is not particularly limited, but from the viewpoint of improving shielding performance, it is preferably 5.0 μm or more, more preferably 10.0 μm or more, even more preferably 20.0 μm or more, and particularly preferably 30.0 μm or more. Also, from the viewpoint of ensuring a higher level of electromagnetic wave shielding performance, it is preferably 2000.0 μm or less, more preferably 1000.0 μm or less, even more preferably 300.0 μm or less, and particularly preferably 100.0 μm or less. The height H of the conductive member may be, for example, 5.0 μm or more to 2000.0 μm or less, 10.0 μm or more to 1000.0 μm or less, 20.0 μm or more to 300.0 μm or less, 20.0 μm or more to 100.0 μm or less, or 30.0 μm or more to 100.0 μm.

[0036] The ratio of the maximum coil radius to the height of the conductive member is not particularly limited, but from the viewpoint of ensuring a higher level of electromagnetic wave shielding properties, it is preferably 0.1 or more, more preferably 0.5 or more, even more preferably 0.6 or more, and particularly preferably 0.8 or more, and from the viewpoint of ensuring a higher level of electromagnetic wave shielding properties, it is preferably 20.0 or less, more preferably 10.0 or less, even more preferably 10.0 or less, and particularly preferably 5.0 or less. The ratio may be, for example, 0.1 or more and 20.0 or less, 0.5 or more and 10.0 or less, 0.6 or more and 5.0 or less, or 0.8 or more and 5.0 or less.

[0037] The coil pitch P of the coil shape is not particularly limited and may be equal to or greater than the lower limit of the wire thickness W described below. Furthermore, from the viewpoint of easily adapting to thinner resin molded bodies, it is usually 200.0 μm or less, preferably 150.0 μm or less, more preferably 100.0 μm or less, and even more preferably 70.0 μm or less. The lower limit of the coil pitch is not particularly limited, and the coil pitch may be, for example, 1.0 μm or more and 200.0 μm or less, 10.0 μm or more and 150.0 μm or less, 15.0 μm or more and 100.0 μm or less, or 15.0 μm or more and 70.0 μm or less.

[0038] The thickness W of the wire constituting the coil shape is not particularly limited, but from the viewpoint of improving rigidity and making it difficult to deform during molding by injection molding or the like, it is usually more than 0.1 μm, preferably more than 0.5 μm, more preferably more than 0.7 μm, and even more preferably more than 1.0 μm. Also, from the viewpoint of reducing weight, the thickness W is usually 50.0 μm or less, preferably 20.0 μm or less, more preferably 15.0 μm or less, and even more preferably 10.0 μm or less. The thickness W may be, for example, more than 0.1 μm and less than 50.0 μm, more than 0.5 μm and less than 20.0 μm, more than 0.7 μm and less than 15.0 μm, or more than 1.0 μm and less than 10.0 μm.

[0039] The number of conductive members contained in the resin molded product may be two or more. The upper limit of the number of conductive members is not particularly limited, and the number may be, for example, two or more and ten or less, two or more and eight or less, or two or more and six or less. When the number of conductive members is two or more, the distance M between the central axes of the coil shapes of adjacent conductive members is not particularly limited, but from the viewpoint of preventing contact between the conductive members, it is usually 1.0 μm or more, preferably 5.0 μm or more, more preferably 50.0 μm or more, and even more preferably 200.0 μm or more. Furthermore, from the viewpoint of ensuring a higher level of electromagnetic wave shielding properties, it is usually 2000.0 μm or less, preferably 1000.0 μm or less, more preferably 900.0 μm or less, and even more preferably 750.0 μm or less. The distance M may be, for example, 1.0 μm or more and 2000.0 μm or less, 5.0 μm or more and 1000.0 μm or less, 50.0 μm or more and 900.0 μm or less, or 200.0 μm or more and 750.0 μm or less.

[0040] There are no particular restrictions on the number of turns in the coil shape, but from the viewpoint of ensuring a higher level of electromagnetic wave shielding performance, it is usually 3 or more, preferably 5 or more, more preferably 6 or more, and even more preferably 10 or more, and is usually 100 or less, preferably 50 or less, more preferably 30 or less, and even more preferably 20 or less.

[0041] The winding direction of the coil is not particularly limited and may be either direction. Furthermore, when the number of conductive members contained in the resin molded body is two or more, the winding directions of the coils of all the conductive members may be the same, but from the viewpoint of suppressing the dependency of the characteristics on the polarization of the incident electromagnetic wave, it is preferable that the winding direction of the coil shape of at least some of the conductive members is different from the winding direction of any one of the conductive members adjacent to that conductive member, and more preferably, it is different from the winding direction of all of the conductive members adjacent to that conductive member, as shown in Figure 8.

[0042] The positions of the ends of the wires constituting the coil shape are not particularly limited. For example, when viewed from the direction of the central axis of the coil shape, the angle formed by a line connecting one end of the wires constituting the coil shape to the central axis and a line connecting the other end of the wires constituting the coil shape to the central axis may be 10° or less, or may be approximately 0°. When viewed from the direction of the central axis of the coil shape, the line connecting the end of the wires constituting the coil shape with the larger coil radius to the central axis is defined as line A. In this case, the angle formed by the two lines, line A of at least some of the conductive members and line A of any one of the conductive members adjacent to that conductive member, is not particularly limited, but may be 10° or less, approximately 0°, or may be approximately 90° as shown in FIG. Furthermore, the angle formed by two straight lines, the straight line A of at least some of the conductive members and the straight lines A of all of the conductive members adjacent to that conductive member, may each independently be an angle selected from the group consisting of approximately 0°, approximately 90°, approximately 180°, and approximately 270°, or may be an angle selected from the group consisting of approximately 90°, approximately 180°, and approximately 270°.

[0043] The conductive member may be completely embedded in a matrix such as a resin, or may not be completely embedded (only partially embedded), i.e., part of the conductive member may be exposed to the outside air.

[0044] (Characteristics of Conductive Member) Volume Resistivity The volume resistivity of the conductive member is not particularly limited, as long as it is a value that allows a small current to flow. The inventors conducted research and found that there was almost no change in the resonant frequency between copper, which has a volume resistivity of 1.55 μΩ cm (0°C), and tungsten, which has a volume resistivity of 4.9 μΩ cm (0°C). An example of a value that allows a small current to flow is a volume resistivity of 3352.8 μΩ cm (20°C) when carbon (graphite) is used.

[0045] The thermal conductivity of the conductive member is not particularly limited. The inventors have conducted research and found that there is almost no change in the resonant frequency between copper, which has a thermal conductivity of 394 W / m·K, and tungsten, which has a thermal conductivity of 174.3 W / m·K.

[0046] [Resin] (Resin Composition) The resin type is not particularly limited as long as it can contain the above-mentioned conductive material. It may be a thermosetting resin or a thermoplastic resin. However, since the electromagnetic wave shielding sheet may be subjected to high temperatures depending on its intended use, a thermosetting resin is preferred. Examples of thermosetting resins include thermosetting resins and photocurable resins. Examples of thermosetting resins include thermosetting acrylic resins, unsaturated polyester resins, epoxy resins, melamine resins, phenolic resins, silicone resins, polyimide resins, and urethane resins. Examples of photocurable resins include photocurable epoxy resins, photocurable polyesters, photocurable vinyl compounds, photocurable epoxy (meth)acrylates, and photocurable urethane (meth)acrylates. Among these, unsaturated polyester resins, photocurable polyesters, epoxy resins, and photocurable epoxy resins are preferred, and epoxy resins and photocurable epoxy resins are particularly preferred from the viewpoint of heat resistance. These resins may be used alone or in combination of two or more types in any type and ratio. From the viewpoint of preventing environmental pollution, the resin is preferably a biodegradable material, such as cellulose.

[0047] The resin content in the resin molded product is not particularly limited, but from the viewpoint of ensuring a higher level of electromagnetic wave shielding properties, it is usually 60% by weight or more, preferably 80% by weight or more, more preferably 90% by weight or more, even more preferably 95% by weight or more, and particularly preferably 97% by weight or more, and is usually 99.99% by weight or less, preferably 99.90% by weight or less, more preferably 99.5% by weight or less, and even more preferably 99.0% by weight or less.

[0048] (Resin Properties) Refractive Index The refractive index of the resin is not particularly limited, but from the viewpoint of improving the electromagnetic wave shielding performance, it is usually 1.05 or more and 3.00 or less, and preferably 1.6 or more and 1.7 or less, which is the refractive index of polyester. The refractive index can be measured by a known method.

[0049] The volume resistivity of the resin is not particularly limited, but from the viewpoint of ensuring insulation, the larger the volume resistivity, the better. For example, ６ The upper limit of the volume resistivity is not particularly limited, but it is preferably 10 ２０ Ω cm or less, １８ The volume resistivity of the resin may be Ω·cm or less. After preparing a sheet of the resin, the volume resistivity of the resin can be measured using a known method for measuring the volume resistivity of a sheet.

[0050] [Other Components] The resin molded body may contain materials (other materials) other than the above-mentioned conductive members and resins, such as inorganic fillers other than the conductive members (including conventional coil-shaped conductive members), or resin fillers. For example, the addition of an inorganic filler not only suppresses contact between the conductive members, but also adjusts the linear expansion coefficient of the resin molded body, making it easier to prevent warping, deflection, undulation, etc. of the resin molded body. The content of inorganic fillers other than the conductive members in the resin molded body is not particularly limited, and the inorganic filler may be optionally contained within a range in which the effects of this embodiment can be obtained.

[0051] [Sheet] The shape of the resin molded body is not particularly limited and can be set appropriately depending on the application, but it is preferably used in sheet form from the viewpoint of electromagnetic wave shielding applications. That is, the resin molded body is preferably in sheet form. Specific conditions for forming the resin molded body in sheet form will be described below. The sheet shape is not particularly limited as long as it is a shape that can be recognized as a sheet, and can be changed appropriately depending on the location where the sheet is to be installed. The sheet may be a single-layer sheet or a laminated sheet. When forming a laminated sheet, it may be an embodiment in which a plurality of sheets that are the resin molded body according to this embodiment are laminated, or an embodiment in which other sheets are laminated to impart various functions.

[0052] The thickness of the sheet is not particularly limited, and from the viewpoint of ensuring a higher level of electromagnetic wave shielding properties, it is usually 10.0 μm or more, preferably 20.0 μm or more, more preferably 50.0 μm or more, and even more preferably 80.0 μm or more. Also, from the viewpoint of the recent trend toward smaller, lighter, and thinner electronic devices such as mobile phones, smartphones, and tablets, it is usually 10.0 mm or less, preferably 5.0 mm or less, more preferably 3.0 mm or less, and even more preferably 1.5 mm or less. The lower limit of the sheet thickness is not particularly limited, and the sheet thickness may be, for example, 0.1 mm or more and 10.0 mm or less, 0.5 mm or more and 5.0 mm or less, 1.0 mm or more and 3.0 mm or less, or 1.0 mm or more and 1.5 mm or less.

[0053] The shape of the sheet is flat, but may have an uneven shape within a range that can be regarded as approximately flat, or may be partially curved. Furthermore, the shape of the sheet observed from the surface may be circular or polygonal, such as triangular or rectangular.

[0054] [Characteristics of Resin Molded Body] (Electromagnetic Wave Shielding Performance) In the present disclosure, the electromagnetic wave shielding performance is evaluated by evaluating the power transmittance T(ω) using the following method. This evaluation method is based on terahertz time-domain spectroscopy, which was used in the transmittance measurement experiment. This evaluation is preferably performed using a sheet-shaped resin molded body, and in this case, it is preferable to perform the measurement so that electromagnetic waves are incident in the thickness direction of the sheet. A schematic diagram of a terahertz time-domain spectroscopy device is shown in Figure 4. In terahertz time-domain spectroscopy, the outputs from one or two femtosecond lasers are generally used as pump light and probe light. The pump light acts as light that excites the terahertz wave. The probe light is used to synchronize the timing of measuring the terahertz wave. The electric field component of the terahertz wave in the time domain is measured by changing the arrival times of the pump light and the probe light. The electric field E after the terahertz wave has passed through the sample is ｓａｍ (t) and the electric field E after passing through air without a sample. ｒｅｆ (t) are detected. Using these values, the complex refractive index, complex dielectric constant, transmittance, power spectrum, etc. are derived. The transmittance is derived from the data obtained from the above measurements by Fourier transform. The obtained electric field waveform E ｓａｍ (t), E ｒｅｆ (t) are Fourier transformed to E ｓａｍ (ω), E ｒｅｆ Using these, the power transmittance T(ω) is expressed by the following formula (A).

[0055]

[0056] The transmittance can be measured using a terahertz spectroscopy system (for example, TAS7500TSH manufactured by Advantest Corporation).

[0057] The shielding performance L (dB) can be calculated from the power transmittance T (ω) and the following formula (B): L = 10 × Log １０(T(ω)) (B) The shielding performance L is not particularly limited, but is preferably −15.0 dB or less, and from the viewpoint of preventing malfunction of electronic devices such as computers, it is preferably −20.0 dB or less, more preferably −30.0 dB or less, even more preferably −40.0 dB or less, particularly preferably −60.0 dB or less, and most particularly preferably −80.0 dB or less, and although there is no need to set a lower limit, it is usually −90.0 dB or more. The electromagnetic wave shielding performance is expressed as −20.0 dB (shielding rate: 90%) when the electromagnetic wave amplitude is 1 / 10 of the electromagnetic wave amplitude of the unshielded electromagnetic wave, −40.0 dB (shielding rate: 99%) when it is 1 / 100, −60.0 dB (shielding rate: 99.9%) when it is 1 / 1000, and −80.0 dB (shielding rate: 99.99%) when it is 1 / 10000.

[0058] <Method for manufacturing molded body> Hereinafter, various embodiments relating to the manufacturing method of a resin molded body will be described, but the manufacturing method of the resin molded body described above is not limited to these manufacturing methods. Furthermore, manufacturing conditions that can be mutually applied in each embodiment can be mutually applied. Furthermore, to the extent applicable, the conditions for the above molded body can be applied to the conditions for the manufacturing method below.

[0059] [First manufacturing method] A first manufacturing method of a molded body, which is another embodiment of the present disclosure (also simply referred to as "first manufacturing method" in the description of this embodiment), is a manufacturing method of a resin molded body, including: a composition preparation step of obtaining a liquid composition containing a resin and a coil-shaped conductive member; and a curing step including a treatment of curing the liquid composition, wherein at least a portion of the coil shape is a tapered shape in which the coil radius gradually increases or decreases, the minimum value of the coil radius is 5 μm or more, and the maximum value of the coil radius is 1000 μm or less. The first manufacturing method may include steps other than the composition preparation step and the curing step.

[0060] [Composition Preparation Step] The first manufacturing method includes a composition preparation step of obtaining a liquid composition containing the above-described resin and a conductive member. The method of obtaining a liquid composition containing a resin and a conductive member is not particularly limited, and examples thereof include a method of mixing a liquid resin and a conductive member, or a method of dissolving a resin in a solvent to obtain a solution and then mixing the solution with a conductive member. The mixing method is not particularly limited, and known methods can be applied. The manufacturing method of the conductive member is not particularly limited, and it can be manufactured by known methods, or it can also be manufactured using a 3D printer.

[0061] When a solvent is used, the type of solvent is not particularly limited as long as it can dissolve the resins and other materials that need to be dissolved. If molding is possible without using a solvent, a solvent need not be used. A curing agent may be added depending on the type of resin used, and known curing agents may be used appropriately depending on the resin. The content of the curing agent in the composition may be, for example, 0.05 to 15% by mass. A polymerization initiator may also be added depending on the type of resin used. For example, a thermal radical generator such as a peroxide, e.g., benzoyl peroxide, may be used as the thermal polymerization initiator, and a photoradical generator, photocation generator, or photoanion generator may be used as the photopolymerization initiator.

[0062] A liquid composition according to another embodiment of the present disclosure comprises a resin and a coil-shaped conductive member, wherein at least a portion of the coil shape is a tapered shape in which the coil radius gradually increases or decreases, the minimum value of the coil radius is 5.0 μm or more, and the maximum value of the coil radius is 1000.0 μm or less. The liquid composition is not particularly limited in its manufacturing method, but can be obtained by the method described in the liquid composition manufacturing process. Furthermore, a molded product according to yet another embodiment of the present disclosure is a cured product of the liquid composition. The conditions for the molded product can be similarly applied to the conditions for the molded product described above.

[0063] [Curing Step] The first manufacturing method includes a curing step that includes a treatment for curing the liquid composition. The curing method is not particularly limited and can be changed appropriately depending on the type of resin. For example, a method of curing using heat or light such as ultraviolet light can be used. Furthermore, when the resin used is a thermoplastic resin and the composition is prepared in a melted state by applying heat, the curing method may be a treatment such as leaving it to stand or cooling. The curing temperature and time vary depending on the materials used, and are not particularly limited as long as they are a temperature and time that can cure the composition.

[0064] [Second manufacturing method] A second manufacturing method of a molded body, which is another embodiment of the present disclosure (also simply referred to as "second manufacturing method" in the description of this embodiment), is a manufacturing method of a resin molded body containing a resin and a coil-shaped conductive member, and includes: a C-shaped conductive member-containing resin sheet manufacturing process for manufacturing a plurality of resin sheets each having the resin, a C-shaped conductive member, and a columnar conductive member connected to an end of the C-shape; and a lamination process for laminating the plurality of resin sheets so that an end of the C-shaped conductive member on one sheet and a columnar conductive member on the other sheet are in contact in the central axial direction; and at least a portion of the coil shape has a tapered shape in which the coil radius gradually increases or decreases, the minimum value of the coil radius is 5.0 μm or more, and the maximum value of the coil radius is 1000.0 μm or less.

[0065] The second manufacturing method includes the above-mentioned C-shaped conductive member-containing resin sheet manufacturing step and lamination step, but may further include other steps. An example of the second manufacturing method including these other steps will be described below.

[0066] [Resin composition preparation step] The second production method may include a resin composition preparation step of preparing a resin composition by dissolving the above-mentioned resin and other materials in a solvent and mixing them. The conditions for the resin composition preparation step in the first production method can be applied to this step in the same way.

[0067] [C-shaped conductive member-containing resin sheet preparation process] The second manufacturing method includes a C-shaped conductive member-containing resin sheet preparation process, which involves preparing multiple resin sheets each having a resin, a C-shaped conductive member, and a columnar conductive member connected to the end of the C-shaped member. The method for preparing such a resin sheet is not particularly limited. For example, a mold is prepared in which the C-shaped conductive member and the columnar conductive member are arranged, and the resin composition obtained in the resin composition preparation process is poured into the mold. The resin is cured to obtain a C-shaped conductive member-containing resin sheet 10, as shown in FIG. 5, which has a cured resin composition 11 (also simply referred to as "resin 11"), a C-shaped conductive member 12, and a columnar conductive member 13. Examples of methods for curing the resin include methods using heat or light such as ultraviolet light. Methods commonly used in the manufacture of printed wiring boards can also be used. Specifically, after preparing a resin sheet by curing the resin composition, holes (vias) are drilled using a drill or laser where the columnar conductive members will be placed, and a foil-shaped conductive member is formed on one side of the sheet. A photosensitive resist is then coated or laminated in a pattern such that the foil-shaped conductive member remains in a C-shape after etching, and then etching is performed to laminate the C-shaped conductive member onto the resin sheet. In addition to the method using the photosensitive resist described above, a method of laminating a C-shaped conductive member onto a resin sheet using etching may also be performed by printing an etching resist pattern. A method of subsequently pouring a conductive member paste into the holes and curing it to form columnar conductive members, thereby obtaining a resin sheet containing C-shaped conductive members, is exemplified. It is preferable that no air remains in the columnar-shaped portions because air increases the volume resistivity and may expand, explode, and break at the reflow temperature for mounting semiconductor components. The parameters of the C-shaped conductive member and the columnar conductive member can be appropriately set based on the explanation of each parameter in the configuration of the resin molded body described above. Note that, even in the embodiment using the C-shaped conductive member, the average angle between the plane of the sheet and the central axis is subject to the above-mentioned average angle conditions.

[0068] [Laminating Step] The second manufacturing method includes a laminating step of laminating a plurality of resin sheets, among the plurality of sheets produced in the C-shaped conductive member-containing resin sheet producing step, so that the end of the C-shaped conductive member on one sheet contacts the columnar conductive member on the other sheet in the central axis direction. For example, as shown in Fig. 6, the laminating method includes laminating the plurality of resin sheets so that the end of the C-shaped conductive member on one sheet contacts the columnar conductive member on the other sheet in the central axis direction.

[0069] <Uses of Molded Article> Uses of the above-described molded article include electromagnetic wave shielding, and another embodiment of the present disclosure is an electromagnetic wave shield having the above-described molded article.

[0070] Other embodiments of the present invention include: a semiconductor module having a semiconductor device (e.g., a module in which a semiconductor element is covered with a molding and packaged, such as in an SOP, QFP, QFN, or BGA) comprising the above-described molded article; electronic or telecommunication equipment such as a smartphone, tablet, smart watch, smart security device, monitoring device, or smart home appliance; automotive equipment such as a safety system, mobile media, communication, wireless headset, battery-powered, electric, or hybrid powertrain, or high-voltage battery system; consumer electronics such as a computer circuit, wireless transmitter (including smartphone), electric motor, flat panel display, or liquid crystal display (LCD); medical equipment such as a smart bed, ventilator, CT scan machine, or transducer that must acquire information such as pulse or blood pressure and convert it into an electronic signal; aerospace equipment such as an aircraft, vehicle, elastomer gasket, conductive paint, or EMI shielding display; systems such as a railway system, mass transit system, high-voltage contact switching system, signal transmission system, or control system; or other equipment (equipment other than those described above that may comprise the molded article); The use of the molded article in each of the above embodiments is not particularly limited as long as the molded article is included as a component. Furthermore, in each embodiment, the molded article is particularly preferably used as an electromagnetic wave shielding sheet. That is, the resin molded article is preferably an electromagnetic wave shielding sheet.

[0071] In particular, when used as an electromagnetic wave shielding sheet, it can be used in any application that shields electromagnetic waves. For example, by placing the electromagnetic wave shielding sheet so as to surround electronic devices that may malfunction due to electromagnetic waves, such malfunctions can be suppressed. In particular, the above-mentioned electromagnetic wave shielding sheet is superior to conventional electromagnetic wave shielding sheets in shielding electromagnetic waves in the high-frequency band, and therefore can be applied to a wider range of fields than conventional electromagnetic wave shielding sheets in that it can shield against electromagnetic waves originating from communication devices such as mobile phones and smartphones, which are being deployed at higher frequencies, particularly high frequency bands of 100 GHz or higher, in order to achieve higher speeds, larger capacities, and lower latency. Note that the above-mentioned sheet achieves a particularly strong electromagnetic wave shielding effect when the plane of the sheet is perpendicular to the direction in which electromagnetic waves arrive from outside.

[0072] The present disclosure will be described in more detail below with reference to examples, but the present disclosure should not be construed as being limited to the following examples.

[0073] <Experiment A: Simulation Experiment> A simulation experiment was carried out to evaluate the electromagnetic wave shielding performance L (dB) of a resin molding using ANSYS HFSS (registered trademark), which is full-wave three-dimensional electromagnetic field software manufactured by ANSYS Incorporated.

[0074] As shown in Figures 7 to 9, a model was set up in which the basic form of a rectangular parallelepiped resin molded article in which resin and coil-shaped conductive members were arranged was infinitely arranged in the X-axis and Y-axis directions, and a simulation experiment was conducted in which electromagnetic waves were made incident from direction A to measure the electromagnetic wave shielding performance L (dB). The models of the basic form in Figures 7 to 9 are referred to as Models 1 to 3, respectively. Note that the conditions such as the number of turns of the coil-shaped conductive members shown in Figures 7 to 9 are shown only as examples, and the actual input values ​​were as shown below and in the tables. The simulation experiment was conducted under the conditions shown below and the conditions shown in the tables described below.

[0075] [Size of basic form] Length in X direction Lx: Same as M in Table 1 except for Example 3, and same as twice M (2M) in Example 3 Length in Y direction Ly: Same as M in Table 1 except for Example 3, and same as twice M (2M) in Example 3 Length in Z direction Lz: Same as H in Table 1

[0076] [Resin Conditions] The resin conditions were set as follows: the real part of the dielectric constant ε' and the dielectric loss tangent tanδ. Specifically, the real part of the dielectric constant was a value expressed by the following formula (1), and the dielectric loss tangent was a value expressed by the following formula (2). n' is the real part of the refractive index, and n'' is the imaginary part of the refractive index. These are set assuming average values ​​for common polyesters, and are known calculation formulas. Real part of the dielectric constant ε'=n' ２ -n” ２ (1) Dielectric tangent tanδ = (2n'n") / (n' ２ -n” ２ ) (2)

[0077] [Conditions for the Conductive Member] Maximum coil radius Rmax: See Table 1. Note that the conductive member of Comparative Example 1 is not tapered, and the radius of the coil shape does not change, but in this example, this radius is treated as Rmax. Decrease in coil radius per turn (decrease): See Table 1. Height H of the conductive member: See Table 1. Coil pitch P of the coil shape: See Table 1. Thickness W of the wire constituting the coil shape: See Table 1. Distance M between the central axes of the coil shapes of adjacent conductive members (similar to the lengths of the resin in the X and Y directions): See Table 1. Number of turns in the coil shape: See Table 1. For Examples 1 and 2 and Comparative Example 1, the start point (S in Figures 7 to 9) and end point (E in Figures 7 to 9) of the coil shape were positioned so that the Y-direction position coincided with the center of the coil shape and the X-direction position was in the positive direction of the X-axis (rightward in Figures 7 and 9), as shown in Figures 7 and 9. In Example 3, the positions of the start and end points of the coil shape when viewed from the Z direction were different between adjacent conductive members, as shown in Figure 8. That is, for the four conductive members included in one period of the structure shown in Figure 8, the coil shape of conductive member 1 was angled so that the Y coordinates of the start and end points coincided with the center of the coil shape and the X coordinate was in the positive direction (to the right in Figure 8) from the center of the coil shape. Conductive members 2, 3, and 4 were arranged so that the angles viewed from the center of the coil shape were offset by 90°, 180°, and 270° from the coil shape of conductive member 1. The notation for the start and end points of the coil shape is a convenient notation for indicating the winding direction, with the end point of the coil shape on the negative side of the Z axis (the downward side in Figures 7 to 9) referred to as the start point, and the end point of the coil shape on the positive side of the Z axis (the upward side in Figures 7 to 9) referred to as the end point. The coil shape of all conductive members in Examples 1 and 2 and Comparative Example 1 was wound right-handed. In Example 3, the conductive members were arranged so that the winding method of the coil shape was different between adjacent conductive members, as shown in Figure 8. That is, for the four conductive members included in one period of the structure shown in Figure 8, conductive members 1 and 4 were clockwise wound, and conductive members 2 and 3 were counterclockwise wound. The conductivity of the conductive members was the value for tungsten.Specifically, the plasma frequency of tungsten is 5.17 × 10 as reported in the literature by MA Ordal, RJ Bell, RW Alexander, LL Long, and MR Querry, Appl. Opt. 24, 4493 (1985). ４ cm －１ and scattering frequency 4.87 × 10 ２ cm －１ The calculation was performed using a conductivity with frequency characteristics calculated from the Drude model.

[0078] [Electromagnetic Wave Conditions] The response was calculated when electromagnetic waves with frequencies from 150 GHz to 500 GHz were incident in the direction indicated by arrow A in Figures 7 to 9, that is, from the surface of the coil shape with the smaller outer diameter, moving from the negative direction to the positive direction of the Z axis. Calculations were performed for electromagnetic waves polarized in the Y direction and electromagnetic waves polarized in the X direction in Figures 7 to 9. In this specification, the respective polarizations are referred to as "Y-polarized" and "X-polarized."

[0079] [Evaluation of Electromagnetic Wave Shielding Performance L] The electromagnetic wave shielding performance was evaluated by calculating the shielding performance L (dB) based on the power transmittance T (ω) obtained by performing an electromagnetic field simulation, according to the following formula (B): L = 10 × Log １０ (T(ω)) (B) Furthermore, the power reflectivity R(ω) was also calculated from the electromagnetic field simulation, and combined with the power transmittance T(ω), the power absorption rate A(ω) was calculated based on the following formula (C): A=1-T(ω)-R(ω) (C) The evaluation results of the electromagnetic wave shielding performance L for each resin molded body are shown in Figures 10 to 13 and the following Table 1. Note that the shielding performance L, absorption rate, and reflectivity shown in Table 1 are values ​​evaluated at a frequency of 300 GHz. Furthermore, the absorption rate and reflectivity are expressed as percentages, and the values ​​calculated above are multiplied by 100 to show the values.

[0080]

[0081] The following was found from Table 1 and Figures 10 to 13. Example 1 has a configuration in which the coil radius changes by a reduction of 7 μm, and has shielding performance around 300 GHz. As shown in Figure 10 and Table 1, the shielding performance against Y-polarized light at 300 GHz was excellent at -20.6 dB, and the reflectance was kept low at 29.5%. On the other hand, Comparative Example 1 has a structure in which the coil radius does not change, and conditions were set in which the maximum outer diameter Rmax of the coil was adjusted to obtain a shielding performance spectrum similar to that of Example 1. From the results of Figure 11 and Table 1, the shielding performance against Y-polarized light at 300 GHz was -20.0 dB, a value close to that of Example 1, but the reflectance was 54.3%, nearly double the 29.5% of Example 1. Thus, it was confirmed that reflectance can be suppressed by giving the coil a tapered structure. Example 2 further adjusts the conditions to suppress reflectance more than Example 1. As shown in FIG. 12 and Table 1, the reflectance for Y-polarized light at 300 GHz was 18.9%, which was even lower than in Example 1. As in Examples 1 and 2, the reduction in reflectance for at least one of X-polarized light and Y-polarized light is a sufficient effect. The inventors further investigated and attempted to suppress this polarization dependency by alternating right-handed and left-handed coils and shifting the coil start and end positions by 90°. The results are shown in FIG. 13 and Table 1 as Example 3. The shielding performance at 300 GHz was excellent, at -24.1 dB for Y-polarized light and -24.3 dB for X-polarized light, and the reflectance was also low, at 18.2% for Y-polarized light and 18.4% for X-polarized light. Thus, it was confirmed that by appropriately arranging the tapered coil, excellent shielding performance and even lower reflectance can be achieved.

[0082] <Experiment B: Verification of Simulation Experiment> A sheet-shaped resin molded body was actually fabricated, and its electromagnetic wave shielding performance was evaluated. The results were compared with those of a simulation experiment. The resin molded body according to Experiment B differs from the resin molded body according to the embodiment of the present disclosure. Specifically, instead of a conductive member having at least a tapered coil shape, a conventional conductive member with a constant coil radius was used to fabricate a resin molded body, and its electromagnetic wave shielding performance was evaluated. In Reference Example 1, the electromagnetic waves incident on the resin molded body were linearly polarized. However, since the orientations of the start and end points of the coil in the actually fabricated sheet were uncontrollable and randomly distributed, the polarization direction of the electromagnetic waves relative to the coil could not be specified. In the simulation experiment of Reference Example 2, in order to incorporate the effect of the random distribution of the coil start and end points in Reference Example 1, responses to electromagnetic waves polarized in the Y direction and the X direction were calculated, and then the average was calculated.

[0083] [Actual Sheet Production: Reference Example 1] The following resin material was poured into a mold capable of producing a sheet with an overall size of 30 mm (length) x 30 mm (width) and 60 (vertical) pockets (through holes) with an outer diameter of 350 μm spaced at center-to-center intervals of 500 μm (grid arrangement). The center-to-center distance of the holes was the coil alignment pitch. The grid arrangement of the pockets was aligned at the center of the sheet, i.e., the center of the grid arrangement overlapped with the center of the sheet. The following resin material was then heated at a curing temperature of 120°C for 10 minutes to obtain a cured sheet, which was then placed in an oven and heated at 150°C for 60 minutes to obtain a pocket-containing sheet. The following conductive material members were then arranged in all pockets of this pocket-containing sheet so that the average angle between the central axis of the metal coil and the planar direction of the sheet was 90°. Thereafter, while maintaining the arrangement of the conductive material members, a resin similar to the resin material described above was poured into each pocket of the sheet, and cured under the same curing conditions as those described above. The sheet thus obtained was then ground to a thickness of 2 mm, thereby obtaining a sheet with a thickness of 2 mm.

[0084] (Raw Materials) Resin material: A mixture of cold mounting resin JP-21111001 (polyester resin) manufactured by Storus Co., Ltd. and hardener (M agent) manufactured by Storus Co., Ltd. The mixing ratio was cold mounting resin:hardener = 100 mL:1.5 mL, and the hardening time was 40 minutes at room temperature. Conductive member: A coil-shaped conductive member was used that met the conditions shown in the sheet manufacturing explanation below and the conditions shown in Table 2 below.

[0085] (Production of Sheet) Tungsten coils with an outer diameter of 300 μm, a wire diameter of 30 μm, and a pitch of 60 μm were aligned in a lattice pattern in a resin material with a period of 500 μm. The coils were oriented perpendicular to the in-plane direction of the sheet. After the resin was cured, the sheet was ground to a thickness of 2 mm and a coil length of 2 mm, resulting in a sheet with a thickness of 2 mm.

[0086] [Electromagnetic Wave Shielding Performance] The electromagnetic wave shielding performance was evaluated by measuring the power transmittance T(ω) and the power reflectance R(ω) using a terahertz spectroscopy system (TAS7500TSH manufactured by Advantest Corporation). Then, the shielding performance L (dB) was calculated from the measured power transmittance T(ω) according to the following formula (B): L = 10 × Log １０ (T(ω)) (B) Furthermore, the power absorption rate A(ω) was calculated based on the following formula (C) using the power reflectance R(ω) and the power transmittance T(ω): A=1-T(ω)-R(ω) (C) The evaluation results for the electromagnetic wave shielding performance L of the resin molded article are shown in Table 2. The shielding performance L, absorption rate, and reflectance shown in Table 2 are values ​​evaluated at a frequency of 300 GHz. The absorption rate and reflectance are expressed as percentages, and the values ​​calculated above are multiplied by 100.

[0087] [Simulation Experiment: Reference Example 2] A simulation experiment was carried out to evaluate the electromagnetic wave shielding performance L (dB) of a resin molding using ANSYS HFSS (registered trademark), which is full-wave three-dimensional electromagnetic field software manufactured by ANSYS Incorporated.

[0088] A simulation experiment was conducted in which a model was set up in which the basic form of a rectangular parallelepiped resin molded body in which resin and coil-shaped conductive members were arranged was infinitely arranged in the X-axis and Y-axis directions as shown in Figure 9, and electromagnetic waves were made incident from direction A to measure the electromagnetic shielding performance L (dB). Note that the conditions such as the number of turns of the coil-shaped conductive members shown in Figure 9 are shown only as examples, and the actual input values ​​are as shown in the respective tables. The simulation experiment was conducted under the conditions shown below and the conditions shown in the respective tables described later.

[0089] [Size of basic form] Length in X direction Lx: same as M in Table 2 Length in Y direction Ly: same as M in Table 2 Length in Z direction Lz: same as H in Table 2

[0090] [Resin Conditions] The resin conditions were set as follows: the real part of the dielectric constant ε' and the dielectric loss tangent tanδ. Specifically, the real part of the dielectric constant was a value expressed by the following formula (1), and the dielectric loss tangent was a value expressed by the following formula (2). n' is the real part of the refractive index, and n'' is the imaginary part of the refractive index. These are set assuming average values ​​for common polyesters, and are known calculation formulas. Real part of the dielectric constant ε'=n' ２ -n” ２ (1) Dielectric tangent tanδ = (2n'n") / (n' ２ -n” ２ ) (2)

[0091] [Conditions for conductive member] Coil radius value R (Rmax in FIG. 9): shown in Table 2; Height H of conductive member: shown in Table 2; Coil pitch P of coil shape: shown in Table 2; Thickness W of wire constituting the coil shape: shown in Table 2; Distance M between central axes of the coil shapes of adjacent conductive members (same as the lengths of resin in the X and Y directions): shown in Table 2; Number of turns of coil shape: 32.8; The winding method of the coil shape was the same as in Comparative Example 1.; The conductivity of the conductive member was the same as in Comparative Example 1.

[0092] [Electromagnetic Wave Conditions] The electromagnetic wave conditions were the same as those in Comparative Example 1.

[0093] [Evaluation of Electromagnetic Wave Shielding Properties] As the electromagnetic wave shielding properties, the electromagnetic wave absorptivity and reflectivity were evaluated, and the evaluation was performed in the same manner as in Comparative Example 1. The evaluation results of the absorptivity and reflectivity of the resin molded body are shown in Table 2. The absorptivity and reflectivity shown in Table 2 are values ​​evaluated at a frequency of 300 GHz. The absorptivity and reflectivity are expressed as percentages, and the values ​​calculated above are multiplied by 100 to show the values.

[0094]

[0095] As shown in Table 2, the measured values ​​of reflectivity and absorptivity at 300 GHz were 60.9% and 39.1%, respectively, which were close to the simulated results of 61.7% and 38.3%. As described above, the simulation results closely matched the measured values, demonstrating the effectiveness of the simulation-based characteristic evaluation of the shielding material used in the examples of the present disclosure.

[0096] From the above, it has been found that a resin molded body can be provided that includes a resin and a coil-shaped conductive member, and that has a tapered shape in which the coil radius gradually increases or decreases, and that has a minimum value of 5 μm or more and a maximum value of 1000 μm or less, and that has a high electromagnetic wave absorption rate and a low reflectance rate, and that is capable of shielding high-frequency electromagnetic waves.

[0097] REFERENCE SIGNS LIST 10 C-shaped conductive member-containing resin sheet 11 Resin 12 C-shaped conductive member 13 Pillar-shaped conductive member

Claims

1. A resin molded product comprising a resin and a coil-shaped conductive member, wherein at least a portion of the coil shape is tapered such that the coil radius gradually increases or decreases, the minimum value of the coil radius is 5.0 μm or more, and the maximum value of the coil radius is 1000.0 μm or less.

2. The resin molded article according to claim 1, wherein the height of the conductive member is 10.0 μm or more and 1000.0 μm or less.

3. The resin molded product according to claim 1 or 2, wherein the thickness of the wire constituting the coil shape is more than 0.5 μm and not more than 20.0 μm.

4. A resin molded article according to any one of claims 1 to 3, wherein the ratio of the maximum value of the coil radius to the height of the conductive member is 0.5 or more and 10.0 or less.

5. The resin molded body according to any one of claims 1 to 4, wherein the number of conductive members contained in the resin molded body is two or more.

6. The resin molded article according to claim 5, wherein the distance between the central axes of the coil shapes of adjacent conductive members is 5.0 μm or more and 1000.0 μm or less.

7. The resin molded article according to claim 5 or 6, wherein the winding direction of the coil shape of at least a part of the conductive members is different from the winding direction of any one of the conductive members adjacent to said conductive member.

8. The resin molded article according to any one of claims 1 to 7, which is in the form of a sheet.

9. The resin molding according to claim 8, which is an electromagnetic wave shielding sheet.

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