Molded body

Abstract

Provided is a molded body which contains a binder and a conductive coil, and which is characterized in that the average ratio of the longest side to the shortest side in a smallest cuboid surrounding the conductive coil is 1-2 (inclusive).

Description

Technical Field

[0001] This invention relates to molded articles. Background Technology

[0002] Mobile phones, smartphones, and other communication devices utilize electromagnetic waves for wireless communication. With advancements in this technology, the frequency bands of the electromagnetic waves used are expanding. Specifically, according to the IMT-Advanced standard defined by the International Telecommunication Union (ITU), the frequency band of approximately 800MHz in 1G mobile communication systems expanded to approximately 3GHz in 4G mobile communication systems. Furthermore, in the currently used 5G mobile communication systems, to achieve high speed, large capacity, low latency, and multiple connections, the frequency band has expanded to 28GHz. Now, as the next generation of communication systems, 6G mobile communication systems utilizing frequency bands above 100GHz are under development. Thus, the utilization of high-frequency electromagnetic waves has attracted considerable attention. On the other hand, due to the increasing frequency of electromagnetic waves, problems such as malfunctions of electronic devices, communication failures, information leaks, and health issues can easily occur. Therefore, it is necessary to control electromagnetic noise (EMC). Specifically, there is a need to develop new materials capable of suppressing both electromagnetic interference (EMI) (the perpetrator) and electromagnetic interference suppression (EMS) (the victim). One approach to addressing this problem is to utilize electromagnetic wave control materials that can mitigate the effects of ambient electromagnetic waves. These materials exist in a variety of forms, including semiconductor packages / modules, enclosures for electrical / electronic equipment, adhesive materials for semiconductor mounting substrates or cables, wallpaper for buildings such as server rooms, and even protective clothing for human protection.

[0003] Various types of materials exist for electromagnetic wave control, and extensive research has been conducted. For example, there are reflective materials that reflect electromagnetic waves by using large-area metal plates, and absorptive materials that absorb electromagnetic waves by using conductive components mixed in organic materials such as resins and rubber.

[0004] For example, as a result of progress in research on absorbing materials, it has been reported that it is effective to use materials with structures having a size one order of magnitude smaller than the wavelength of the electromagnetic waves to be shielded, and materials containing small fillers have been developed as a method for forming such structures.

[0005] Patent Document 1 discloses a sheet formed from a composite material that exhibits excellent electromagnetic wave shielding at a frequency of 1 GHz. The composite material comprises an insulating layer and a conductive layer containing small flake-shaped silver powder with a specific particle size and bulk density in an adhesive resin. Patent Document 2 discloses a sheet formed from a composite material capable of shielding electromagnetic waves in the 1 MHz to 1 GHz frequency band. This composite material contains ferrite particles in an adhesive resin; these ferrite particles are single crystals with a specific average particle size and a perfectly spherical particle shape. Furthermore, Patent Document 3 discloses a sheet formed from a composite material that exhibits excellent processability and flexibility and is capable of shielding electromagnetic waves in the 18.0 to 26.5 GHz frequency band. This composite material contains a specific amount or more of nickel nanowires in an adhesive resin.

[0006] On the other hand, the wafers disclosed in Patent Documents 1-3 have the following problem: they cannot handle electromagnetic waves from next-generation wireless communication systems that have a frequency band that is more than an order of magnitude larger than that used in current wireless communication systems. To solve this problem, wafers using conductive components in the shape of coils have also been developed, as disclosed in Patent Document 4.

[0007] Existing technical documents

[0008] Patent documents

[0009] Patent Document 1: Japanese Patent Application Publication No. 2011-86930

[0010] Patent Document 2: International Publication No. 2017 / 212997

[0011] Patent Document 3: Japanese Patent Application Publication No. 2019-67997

[0012] Patent Document 4: International Publication No. 2022 / 009960 Summary of the Invention

[0013] The problem that the invention aims to solve

[0014] While the sheet disclosed in Patent Document 4 has excellent electromagnetic wave shielding performance, it has hardly been studied from the perspective of the sheet's resistance, which may vary depending on the degree of contact between conductive components, and there is still room for improvement.

[0015] For example, when using a molded body such as a sheet with electromagnetic wave shielding properties as a housing to protect components such as semiconductor elements, a module formed by placing this molded body on a substrate to cover semiconductor elements that are susceptible to electromagnetic waves or easily emit electromagnetic waves can be manufactured. This suppresses electromagnetic waves from entering the housing and prevents electromagnetic waves from leaking to the outside of the housing. However, when using such a housing, the terminals of the semiconductor elements are generally exposed. If the housing has high conductivity (i.e., low resistivity), there is a risk of short circuits between the terminals, thus preventing space-saving.

[0016] Therefore, the objective of this invention is to provide a sheet that can maintain high resistivity and shield electromagnetic waves in the high-frequency band.

[0017] Problem Solving Methods

[0018] The inventors conducted in-depth research and discovered that the above-mentioned problems could be solved by using adhesives and conductive coils in a special manner, thus completing the present invention.

[0019] That is, the present invention has the following features.

[0020] [1] A molded body comprising an adhesive and a plurality of conductive coils,

[0021] The average ratio of the longest side to the shortest side in the smallest cuboid surrounding the aforementioned conductive coil is greater than 1 and less than 2.

[0022] [2] According to the molded body described in [1], wherein,

[0023] The adhesives described above contain cellulose nanofibers.

[0024] [3] The molded body according to [1] or [2], wherein,

[0025] The average number of turns of the aforementioned conductive coil is 1.2 or more and 50 or less.

[0026] [4] The molded body according to any one of [1] to [3], wherein,

[0027] The conductive component constituting the aforementioned conductive coil is helical.

[0028] [5] The molded body according to any one of [1] to [4], wherein,

[0029] The content of the conductive coil in the above-mentioned molded body is 0.02 g / cm³. 3 Above and below 5.00 g / cm³ 3 .

[0030] [6] The molded body according to any one of [1] to [5] is an electromagnetic wave shielding sheet.

[0031] [7] A liquid composition comprising an adhesive and a conductive coil,

[0032] The average ratio of the longest side to the shortest side in the smallest cuboid surrounding the aforementioned conductive coil is greater than 1 and less than 2.

[0033] [8] A molded body, which is a cured product of the liquid composition described in [7].

[0034] [9] The molded body according to [8] is an electromagnetic wave shielding sheet.

[0035]

[10] An electromagnetic wave shield having the molded body described in [6] or [9].

[0036]

[11] A semiconductor module having a molded body as described in any one of [1] to [6], [8] and [9].

[0037]

[12] An electronic device having a molded body as described in any one of [1] to [6], [8] and [9].

[0038]

[13] An automotive device having a molded body as described in any one of [1] to [6], [8] and [9].

[0039]

[14] A consumer electronics device having a molded body as described in any one of [1] to [6], [8] and [9].

[0040]

[15] A medical device having a molded body as described in any one of [1] to [6], [8] and [9].

[0041]

[16] An aerospace device having a molded body as described in any one of [1] to [6], [8] and [9].

[0042]

[17] A system having a molded body as described in any one of [1] to [6], [8] and [9].

[0043]

[18] A method for manufacturing a molded article, the method comprising:

[0044] A composition manufacturing process for obtaining a liquid composition containing an adhesive and a conductive coil;

[0045] A freezing process in which the above-mentioned liquid composition is frozen to obtain a frozen finished article; and

[0046] The compression process involves applying a load to the frozen body to compress it, thereby obtaining a molded body.

[0047] Among them, the average ratio of the longest side to the shortest side in the smallest cuboid surrounding the aforementioned conductive coil is greater than 1 and less than 2.

[0048]

[19] According to the method for manufacturing the molded body described in

[18] , wherein,

[0049] Between the freezing process and the compression process, there is an immersion process in which the frozen body is immersed in a liquid containing the components that crosslink the adhesive.

[0050]

[20] According to the manufacturing method described in

[19] , wherein,

[0051] The above-mentioned impregnation process includes a process of impregnating the frozen body with a liquid other than the liquid after removing the liquid containing the components that crosslink the above-mentioned adhesive.

[0052] The effects of the invention

[0053] According to the present invention, a lightweight sheet capable of shielding high-frequency electromagnetic waves can be provided. Attached Figure Description

[0054] Figure 1 This is a schematic diagram illustrating one method of using a conductive coil.

[0055] Figure 2 It is a diagram used to illustrate the shape of a conductive coil.

[0056] Figure 3 This is a schematic diagram illustrating one method of using a conductive coil.

[0057] Figure 4 This is a scanning electron microscope image of a conductive coil (alternative to the attached photograph).

[0058] Figure 5 It is a diagram used to illustrate the shape of a conductive coil.

[0059] Figure 6 This is a schematic diagram illustrating the experimental setup involved in evaluating electromagnetic wave shielding characteristics.

[0060] Figure 7 This is a graph used to illustrate the results of the characteristic evaluation of the slices in Example 1 and Comparative Example 1.

[0061] Figure 8 This is a graph used to show the results of the characteristic evaluation of the sheets in Examples 1 to 3.

[0062] Figure 9 This is a graph used to illustrate the results of the characteristic evaluation of the sheets in Examples 4-6.

[0063] Figure 10 These are graphs used to illustrate the results of the characteristic evaluation of the sheets in Examples 7-11.

[0064] Symbol Explanation

[0065] l Average outer diameter

[0066] m Average pitch width

[0067] n Average length along the central axis

[0068] p Average core diameter

[0069] The average outer diameter of the l' large spiral

[0070] m' Average pitch width of the large spiral

[0071] n' Average length along the central axis of the large spiral

[0072] p' Average outer diameter of the small spiral

[0073] q' Average pitch width of the small helix

[0074] r' Average core diameter

[0075] The central axis of the G spiral

[0076] H. Central axis of the small spiral Detailed Implementation

[0077] The embodiments of the present invention will now be described in detail. However, each embodiment and its combination are merely examples, and appropriate additions, omissions, substitutions, and other modifications can be made without departing from the spirit of the present invention. This disclosure is not limited to the embodiments, but only to the claims.

[0078] In this disclosure, the numerical range represented by "~" refers to the range including the values ​​recorded before and after "~" as the lower and upper limits. "A~B" means above A and below B. In addition, when the numerical ranges represented by "A~B" or "A and below B" are recorded in stages (for example, according to a preferred order), the upper and lower limits of each numerical range can be arbitrarily combined.

[0079] Furthermore, while multiple embodiments are described in this disclosure, various conditions in each embodiment can be applied to each other to the extent applicable.

[0080] In addition, the expression "A or B" in this disclosure can also be replaced with "selected from at least one of A and B".

[0081] In addition, in this disclosure, "multiple" means "two or more".

[0082] The dimensions, materials, shapes, and relative arrangements of the constituent elements described in this embodiment are merely examples. Furthermore, this embodiment will be explained using accompanying drawings as appropriate, but the dimensions in the drawings are also just examples.

[0083] Furthermore, when the term "average" is used in the parameters of the conductive coil, it refers to the value calculated as the average of multiple conductive coils. For example, the average outer diameter of the conductive coil is the value calculated by measuring the outer diameter of each of the multiple conductive coils and using it as the average. There is no particular limitation on the number of objects used for calculating the average; it does not have to be the full number. For example, it can be any arbitrarily selected 10, or it can be any arbitrarily selected 50. It should be noted that the number of conductive coils in the molded body can be less than 10.

[0084] <Composition of Molded Entities>

[0085] As one embodiment of this disclosure, the molded body (also simply referred to as the "molded body") includes an adhesive and a plurality of conductive coils.

[0086] The average ratio of the longest side to the shortest side in the smallest cuboid surrounding the aforementioned conductive coil is greater than 1 and less than 2.

[0087] As a structure capable of absorbing strong electromagnetic waves in the terahertz region, the inventors have developed a conductive coil with a central axis.

[0088] It is known that in the shape of a coil, the simulated C-shaped surface structure can be regarded as a multi-layered structure. If they are regarded as a circuit, the absorption effect of electromagnetic waves based on the LC resonance of the coil shape itself as an inductor L and the resonant cavity gap as a capacitor C can be obtained.

[0089] In addition, it is known that absorption can be obtained based on the resonance effect brought about by the magnetic field entering the coil.

[0090] In this technical field, when using a molded body containing a conductive coil with a central axis as a molded body for electromagnetic wave shielding, conventionally, a conductive coil with a length in the central axis direction that is relatively long compared to the outer diameter of the conductive coil is used. The inventors speculate that this is because the shape of the coil is generally a shape with a long length in the central axis direction, and it is believed that the longer the length of the conductive coil in the central axis direction, the higher the electromagnetic wave shielding performance. Furthermore, it is believed that increasing the length of the conductive coil in the central axis direction can increase the volume and the density of the conductive coil in the molded body, thereby improving the electromagnetic wave shielding performance.

[0091] However, when using conductive coils with long lengths along the central axis, the probability of these coils coming into contact with each other increases. When this happens, the resistivity of the molded body decreases. For example, in a module (semiconductor module) where the molded body is placed on a substrate to cover semiconductor elements, the terminals of the semiconductor elements are generally exposed. If the conductivity of the molded body is high, i.e., if its resistivity is low, there is a risk of short circuits between the terminals. Furthermore, when the conductive coils come into contact, current flows between them, making it difficult to achieve LC resonance. Therefore, there is a tendency for electromagnetic wave shielding performance to decrease.

[0092] Therefore, the inventors conducted in-depth research and manufactured the molded body according to the above embodiment. In this molded body, the average ratio of the longest side to the shortest side in the smallest cuboid surrounding the conductive coil is in the range of 1 to 2. Therefore, compared with the existing molded body, it is less likely for the conductive coils to come into contact, and the above-mentioned problems are less likely to occur.

[0093] Furthermore, when using existing conductive coils, if the coils are arranged randomly without considering their orientation, the aforementioned energization is likely to occur. Therefore, in many cases, it is necessary to ensure that the orientation of the conductive coils is consistent in a certain direction. This process is time-consuming, and therefore, it is problematic from a manufacturing cost perspective. In contrast, in the molded body of the above-described embodiment, such energization problems are less likely to occur. Therefore, the conductive coils can be arranged randomly without considering their orientation, which is also advantageous from a manufacturing cost perspective.

[0094] Furthermore, in the above embodiments, lightweight materials such as polymer materials can be used as adhesives, thus making it easier to achieve a lighter weight compared to existing methods that use metal plates.

[0095] Furthermore, one of the tasks of electromagnetic wave shielding components is to prevent the reflection of electromagnetic waves incident from the side where the shielded electromagnetic wave product is located. However, when a metal plate is used, electromagnetic waves are essentially reflected at the metal surface, making it difficult to prevent reflection. In contrast, in the above-described embodiment, a polymer material that easily prevents electromagnetic wave reflection and thus easily absorbs electromagnetic waves can be used as the adhesive, which is also superior from the viewpoint of electromagnetic wave shielding performance.

[0096] In addition, conventionally, metal housings, primarily stainless steel housings, have been used as electromagnetic wave shielding components in semiconductor modules. Such stainless steel housings can shield electromagnetic waves from the outside by reflecting them. While reflection can block the entry and exit of electromagnetic waves, the presence of multiple semiconductor elements within the housing means that electromagnetic waves emitted from these elements may undergo diffuse reflection within the housing, potentially causing malfunctions in adjacent semiconductor elements.

[0097] In addition, since the stainless steel housing is conductive, it needs to be designed to avoid contact with the exposed terminals in order to prevent short circuits as described above. Therefore, there are limits to space-saving design.

[0098] When the existing stainless steel housing is replaced with the molded body of this embodiment in the same shape, the molded body is an absorber. Therefore, diffuse reflection within the housing is less likely to occur, reducing the risk of malfunction. In addition, due to its high resistance, it can be used in contact with exposed terminals, easily achieving space saving. Furthermore, the molded body of this embodiment can be formed by coating or spraying, thus enabling close bonding with multiple semiconductors, including terminals, achieving maximum space saving while maintaining its performance as an absorber.

[0099] The above-described molded body has no particular limitations in its application and can be suitable for electromagnetic wave shielding sheets, etc. In the following description, the shape of the sheet, especially the shape of the electromagnetic wave shielding sheet, will be specifically described as a molded body. Hereinafter, the term "sheet" may be replaced with "molded body".

[0100] [Conductive coil]

[0101] (The structure of a conductive coil)

[0102] The conductive coil has a coil shape (spiral shape) with a central axis. In this disclosure, coil shape refers to a shape formed by a structure surrounding the central axis and a structure extending along the direction of the central axis, or a shape formed by a structure with one side surrounding the central axis and the other side extending along the direction of the central axis. The structure surrounding the central axis can be a circular circumferential shape or a polygonal circumferential shape. Examples of specific coil shapes include, for instance... Figure 1 (a) shows a spiral shape with a central axis, etc.

[0103] It should be noted that a conductive coil can be not only a conductive coil whose central axis is a straight line, but also a conductive coil whose central axis can be approximated as a straight line. In the case of a conductive coil whose central axis can be approximated as a straight line, the approximate straight line becomes the central axis.

[0104] In addition, there are no particular restrictions on the winding direction of the coil shape; right-hand and left-hand coils can coexist, but it is preferable that they are consistent in any one winding direction.

[0105] The shape of the cross-section of the wire that forms the coil shape is not particularly limited. For example, it can be a circle, or a polygon such as a triangle or a quadrilateral. From the point of view of ease of acquisition and ease of manufacture, a circle is preferred.

[0106] From the viewpoint of easily preventing energization between the conductive coils, there is no particular limitation as long as the average ratio of the longest side to the shortest side (also simply referred to as the "average ratio of the cuboid") in the smallest cuboid surrounding the conductive coils is 1 or more and 2 or less. Preferably, it is 1.7 or less, more preferably 1.5 or less, further preferably 1.2 or less, particularly preferably 1.1 or less, and even more particularly preferably 1.05 or less. The smaller the average ratio, the more preferred, and its lower limit is 1 or more.

[0107] The smallest cuboid that can enclose a conductive coil is Figure 1 The cuboid shown in (b) is indicated by dashed lines.

[0108] The shortest and longest sides of the smallest cuboid surrounding the conductive coil can be determined by observing the sample using a microscope such as an optical microscope. In particular, if the cross-section of the conductive coil is circular, the dimensions of the cuboid can be determined based on the length along the central axis of the conductive coil and the diameter of the circle.

[0109] In addition, if it is not possible to observe the conductive coil contained in the sheet, the conductive coil can be observed directly after it is removed from the sheet. In particular, if the adhesive can be dissolved, the conductive coil removed by dissolving the adhesive can be observed directly.

[0110] Regarding the type of material for the conductive coil, there are no particular restrictions as long as it is conductive. Examples include: carbon materials such as carbon, 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), alloys formed by combinations of these metal elements, or metal-containing compounds such as oxides, halides, or sulfides of these metal elements or alloys. From the viewpoint that the elastic modulus is suitable for coil processing, has good corrosion resistance when contained in an adhesive, has a small coefficient of linear expansion, and therefore has good durability, copper (Cu), iron (Fe), or tungsten (W) are preferred, with tungsten (W) being particularly preferred.

[0111] There are no particular limitations on the content of conductive coils in the sheet, and the preferred range varies depending on the raw materials of the conductive coils. However, from the viewpoint of improving electromagnetic wave shielding, the content per unit volume of the sheet is typically 0.01 g / cm³. 3 The preferred value is 0.02 g / cm³. 3 The above, and more preferably, is 0.15 g / cm³. 3 The above, and more preferably, is 0.2 g / cm³. 3 The above, and especially preferred, is 0.3 g / cm³. 3 The above, and the optimal value, is 0.5 g / cm³. 3 In addition, considering the need to prevent coils from contacting each other as much as possible, the standard is typically 5.00 g / cm³. 3 Below or less than 5.00 g / cm 3 The preferred value is 4.00 g / cm³. 3 The following, or more preferably, is 3.00 g / cm³ 3 The following, and more preferably 2.00 g / cm³ 3 The following, and more preferably, is 1.50 g / cm³. 3 The following, and more preferably, is 0.90 g / cm³. 3 the following.

[0112] The arrangement of the conductive coils is not particularly limited and can be random, but is preferably arranged to form a metamaterial structure. In this disclosure, a metamaterial structure refers to a way in which the conductive coils are arranged neatly in a sheet, and more specifically, to a way in which the conductive coils are arranged at periodic intervals in an adhesive. Furthermore, the method of neat arrangement is not particularly limited, and examples include neatly arranging them into polygonal shapes such as circles, triangles, or quadrilaterals. This neat arrangement can consist of one level or two or more levels. In addition, when multiple layers are stacked to form a sheet, the arrangement of the conductive coils in each layer can be arbitrarily set. For example, the arrangement of the conductive coils in all layers can be random, or the arrangement of the conductive coils in all layers can be set to form a metamaterial structure, or a laminate combining these arrangements can be formed.

[0113] One method of using a conductive coil is shown in Figure 2 . Figure 2 The image above is a view of the conductive coil taken from the direction of its central axis. Figure 2 The following diagram is obtained by viewing the conductive coil from a direction at 90° to the central axis. Figure 2 Where l is the average outer diameter, m is the average pitch width, and n is the average length along the central axis of the conductive coil. These parameters can be determined by internal observation using CT-X-rays.

[0114] The average outer diameter l of the conductive coil (also simply referred to as the "outer diameter of the coil shape") can be selected in a manner that maintains the average ratio of the cuboid described above, and there are no particular limitations. It can be 10 μm or more, 30 μm or more, 100 μm or more, or 300 μm or more. On the other hand, from the viewpoint of being able to reduce the thickness of the molded body, and from the viewpoint that the molded body of this embodiment is easy to absorb electromagnetic waves in a wide frequency band, it is preferable that the average outer diameter l is small. It is usually 10,000 μm or less, preferably 1,000 μm or less, more preferably 800 μm or less, further preferably 750 μm or less, particularly preferably 600 μm or less, and most preferably 500 μm or less.

[0115] The average pitch width m of the coil shape (also referred to as "the pitch width of the coil shape") is not particularly limited as long as it is selected in a way that can maintain the average ratio of the cuboid described above. Its lower limit can be above the lower limit value of the average core wire diameter p described later. In addition, from the viewpoint of suppressing the core wire from becoming sparse and reducing the electromagnetic wave shielding performance, its upper limit is usually 200 μm or less, preferably 150 μm or less, more preferably 100 μm or less, and even more preferably 70 μm or less.

[0116] The average length n of the coil-shaped portion along the central axis of the conductive coil (also simply referred to as "the length of the coil-shaped portion along the central axis of the coil shape") can be selected in a manner that maintains the average ratio of the cuboid described above, and there are no particular limitations. It can be 20 μm or more, 35 μm or more, 50 μm or more, 100 μm or more, or 300 μm or more. On the other hand, from the viewpoint of being able to reduce the thickness of the molded body, and from the viewpoint of the molded body of this embodiment being able to easily absorb electromagnetic waves over a wide frequency band, it is preferable that the average length n is small. It is usually 10,000 μm or less, preferably 1,000 μm or less, more preferably 800 μm or less, further preferably 750 μm or less, particularly preferably 600 μm or less, and most preferably 500 μm or less.

[0117] The average core wire diameter p (also simply referred to as the "core wire diameter of the coil shape") of the conductive coil is not particularly limited. From the viewpoint of improving rigidity and minimizing deformation during molding such as injection molding, it is generally greater than 1 μm, preferably 5 μm or more, more preferably 10 μm or more, and even more preferably 15 μm or more. In addition, it can be less than 1 / 3 of the aforementioned average outer diameter l. Furthermore, from the viewpoint of achieving lightweight, the average core wire diameter p is generally 75 μm or less, preferably 50 μm or less, more preferably 40 μm or less, and even more preferably 30 μm or less.

[0118] The average length of the core wire of each conductive coil (also referred to as "core wire length") is not particularly limited. From the viewpoint of improving shielding performance, it is preferably 1000 μm or more, more preferably 10000 μm or more, further preferably 40000 μm or more, and particularly preferably 100000 μm or more. In addition, from the viewpoint that the average size of each coil becomes larger and the thin film forming of the molded body becomes more difficult, it is preferably 1,000000 μm or less, more preferably 800000 μm or less, further preferably 500000 μm or less, and particularly preferably 300000 μm or less.

[0119] There is no particular limitation on the total core length of the coil contained in each unit volume of the sheet (also referred to as "total core length of the coil as a whole"), but from the viewpoint of improving shielding performance, it is preferably 10 m / cm. 3 The above, and more preferably 20m / cm 3 The above, and more preferably 30m / cm 3 The above, and especially preferred, is 50m / cm. 3 Furthermore, from the viewpoint of preventing the coils from coming into contact with each other, a flow rate of 2000 m / cm is preferred. 3The following, and more preferably, is 1000 m / cm 3 The following, and more preferably, is 500 m / cm 3 the following.

[0120] There is no particular limitation on the average number of turns (also referred to as "number of turns") of the conductive coil. From the viewpoint of ensuring sufficient electromagnetic wave shielding, it is usually 1 or more, preferably 1.2 or more, more preferably 1.5 or more, and even more preferably 3 or more. In addition, it is usually 100 or less, preferably 50 or less, more preferably 30 or less, and even more preferably 20 or less.

[0121] (Double coil)

[0122] Conductive coils such as Figure 3 and Figure 4 As shown, the conductive component constituting the conductive coil can be helical. In this disclosure, such a conductive coil is referred to as a "double coil," and a general conductive coil that does not have this helical shape is referred to as a "single coil." Double coils can be manufactured by known methods (e.g., methods for making single coils into a helical shape), or commercially available products can be used.

[0123] In addition, "the conductive component constituting the conductive coil is helical" can also be expressed as the helical conductive coil further forming a helical shape. Alternatively, it can be expressed as the central axis of the helical conductive coil being formed in a helical manner, and the wire forming the conductive coil being helical.

[0124] Figure 3 This is a schematic diagram illustrating one method of using a two-coil coil. Figure 4 This is a scanning electron microscope image of a dual-coil loop. Hereinafter, in a dual-coil loop, the spiral forming the same spiral shape as a single-coil loop will be called the "large spiral," and the spiral formed on the line constituting the large spiral will be called the "small spiral." In a dual-coil loop, the central axis of the aforementioned coil shape corresponds to the central axis of the large spiral. Figure 3 In this embodiment, G represents the central axis of the large helix, and H represents the central axis of the small helix. In the electromagnetic wave shielding sheet of this embodiment, if an electromagnetic wave passes through the interior of the large helix, it exhibits an absorption effect based on the LC resonance of the large helix. Furthermore, if an electromagnetic wave passes through the interior of the small helix, it also exhibits an absorption effect based on the LC resonance of the small helix. Therefore, electromagnetic waves incident from all directions can be absorbed regardless of the coil's orientation. In the electromagnetic wave shielding sheet of this embodiment, by using a coil with such a structure, sufficient shielding against high-frequency electromagnetic waves can also be ensured.

[0125] The central axis of a large double-coil spiral can be either a straight line or an approximation of a straight line. In the case where the central axis is approximated as a straight line, this approximation becomes the central axis.

[0126] The conditions for the coil structure described above can be applied to both single-coil and double-coil structures. The following shows the conditions that are particularly suitable for double-coil structures.

[0127] There are no particular limitations on the content of the dual coils in the sheet, and the preferred range varies depending on the raw materials of the conductive coils. However, from the viewpoint of improving electromagnetic wave shielding, the content per unit volume of the sheet is typically 0.02 g / cm³. 3 The above is preferably 0.01 g / cm³. 3 The above, and more preferably, is 0.15 g / cm³. 3 The above, and more preferably, is 0.2 g / cm³. 3 The above, and especially preferred, is 0.3 g / cm³. 3 The above, and the optimal value, is 0.5 g / cm³. 3 In addition, considering the need to prevent coils from contacting each other as much as possible, the standard is typically 5.00 g / cm³. 3 Below or less than 5.00 g / cm³ 3 The preferred value is 4.00 g / cm³. 3 The following, or more preferably, is 3.00 g / cm³ 3 The following, and more preferably 2.00 g / cm³ 3 The following, and more preferably, is 1.50 g / cm³. 3 The following, and more preferably, is 0.90 g / cm³. 3 the following.

[0128] In the electromagnetic wave shielding sheet of this embodiment, a dual-coil design is used, which provides superior electromagnetic wave shielding performance for each coil compared to a single-coil design. Therefore, to achieve the same level of electromagnetic wave shielding, the electromagnetic wave shielding sheet of this embodiment can reduce the amount of conductive coils used compared to an electromagnetic wave shielding sheet manufactured using a single coil. Typically, the price per unit volume of conductive coils is higher than that of adhesives; therefore, the electromagnetic wave shielding sheet of this embodiment has lower material costs compared to an electromagnetic wave shielding sheet manufactured using a single coil.

[0129] One method of using a dual coil is shown below. Figure 5 . Figure 5 The top image is a view of the double coil from the direction of the central axis of the large spiral of the double coil, and the bottom image is a view of the double coil from a direction at 90° to the central axis. Figure 5l' is the average outer diameter of the large helix, m' is the average pitch width of the large helix, n' is the average length of the double coils along the central axis of the large helix, p' is the average outer diameter of the small helix, q' is the average pitch width of the small helix, and r' is the average core wire diameter. These parameters can be determined by internal observation using CT-X-rays.

[0130] The average outer diameter l' of the large helix (also simply referred to as the "outer diameter of the large helix") can be selected in a way that maintains the average ratio of the cuboid described above, and there are no particular limitations. It can be 10 μm or more, 30 μm or more, 100 μm or more, or 300 μm or more. On the other hand, from the viewpoint of being able to reduce the thickness of the molded body, and from the viewpoint that the molded body of this embodiment is easy to absorb electromagnetic waves in a wide frequency band, it is preferable to have a small average outer diameter l', which is usually 10,000 μm or less, preferably 1,000 μm or less, more preferably 800 μm or less, further preferably 750 μm or less, particularly preferably 600 μm or less, and most preferably 500 μm or less.

[0131] The average pitch width m' of the large helix (also referred to as "the pitch width of the large helix") can be selected in a way that maintains the average ratio of the cuboid described above, and there are no particular restrictions. Its lower limit can be above the lower limit of the average outer diameter p' of the small helix described later. In addition, from the viewpoint of suppressing the thickening of the core wire and the reduction of electromagnetic wave shielding performance, its upper limit is usually 560 μm or less, preferably 490 μm or less, more preferably 420 μm or less, and even more preferably 350 μm or less.

[0132] The average length n' of the double coils (coil-shaped portion) along the central axis of the large helix (also simply referred to as "the length of the double coils along the central axis of the large helix") can be selected in a manner that maintains the average ratio of the cuboid described above, and there are no particular limitations. It can be 20 μm or more, 35 μm or more, 50 μm or more, 100 μm or more, or 300 μm or more. On the other hand, from the viewpoint of being able to reduce the thickness of the molded body, and from the viewpoint that the molded body of this embodiment is easy to absorb electromagnetic waves in a wide frequency band, it is preferable that the average length n' is small. It is usually 10,000 μm or less, preferably 1,000 μm or less, more preferably 800 μm or less, further preferably 750 μm or less, particularly preferably 600 μm or less, and most preferably 500 μm or less.

[0133] There are no particular restrictions on the average outer diameter p' of the small helix (also referred to as the "outer diameter of the small helix"). It can exceed 3.5 μm, be greater than 3.5 μm, be greater than 35 μm, be greater than 70 μm, or be greater than 105 μm. Alternatively, it can be less than 490 μm, less than 455 μm, less than 350 μm, or less than 175 μm.

[0134] The average pitch width q' of the small helix (also referred to as "the pitch width of the small helix") is not particularly limited. Its lower limit can be above the lower limit of the average core diameter r' described later. In addition, from the viewpoint of suppressing the thinning of the core and the reduction of electromagnetic wave shielding performance, its upper limit is usually 200 μm or less, preferably 150 μm or less, more preferably 100 μm or less, and even more preferably 70 μm or less.

[0135] The average core wire diameter r' (also simply referred to as "core wire diameter") is not particularly limited. From the viewpoint of improving rigidity and minimizing deformation during molding such as injection molding, it is generally greater than 1 μm, preferably 10 μm or more, more preferably 20 μm or more, and even more preferably 30 μm or more. Furthermore, it can be less than one-third of the aforementioned average outer diameter p'. Additionally, from the viewpoint of achieving lightweight design, the average core wire diameter r' is generally less than 140 μm, preferably less than 130 μm, more preferably less than 100 μm, and even more preferably less than 50 μm.

[0136] The average length of the small spiral of each conductive coil (also referred to as the "length of the small spiral") is not particularly limited. From the viewpoint of improving shielding performance, it is preferably 1000 μm or more, more preferably 10000 μm or more, further preferably 40000 μm or more, and particularly preferably 100000 μm or more. In addition, from the viewpoint that the average size of each coil becomes larger and the thin film forming of the molded body becomes more difficult, it is preferably 1,000000 μm or less, more preferably 800000 μm or less, further preferably 500000 μm or less, and particularly preferably 300000 μm or less. The length of the small spiral refers to the length of the double coil when the double coil is stretched into a straight line while maintaining the shape of the small spiral, that is, the length of the central axis of the small spiral.

[0137] There is no particular limitation on the total core wire length of the dual coils per unit volume of the sheet (also referred to as the "total core wire length of the dual coils"). From the viewpoint of improving shielding performance, it is preferably 10 m / cm. 3 The above, and more preferably 20m / cm 3 The above, and more preferably 30m / cm 3 The above, and especially preferred, is 50m / cm.3 Furthermore, from the viewpoint of preventing the coils from coming into contact with each other, a flow rate of 2000 m / cm is preferred. 3 The following, and more preferably, is 1000 m / cm 3 The following, and more preferably, is 500 m / cm 3 the following.

[0138] The average number of turns of the large spiral (also simply referred to as the "number of turns of the large spiral") is not particularly limited. From the viewpoint of ensuring sufficient electromagnetic wave shielding, it is usually 4 or more, preferably 5 or more, more preferably 6 or more, and usually less than 14, preferably 11 or less, more preferably 10 or less, and even more preferably 8 or less. In particular, the fewer the number of turns of the large spiral, the larger the frequency band of electromagnetic waves that can be effectively shielded, and the easier it is to shift to the high frequency band, especially above 100 GHz.

[0139] There is no particular limitation on the average number of turns of the small spiral (also referred to as "the number of turns of the small spiral"). From the viewpoint of ensuring sufficient electromagnetic wave shielding, it is usually 24 or more, preferably 36 or more, more preferably 63 or more, and even more preferably 108 or more. In addition, it is usually 942 or less, preferably 603 or less, more preferably 419 or less, and even more preferably 308 or less.

[0140] The core wire of the conductive coil can be made of a single metallic element or an alloy, or it can have a plated coating on its surface. Furthermore, to minimize the risk of short circuits between conductive coils, the surface can be coated with insulating resin, or an oxide film can be formed on the surface. For example, an oxide film can be formed by subjecting the conductive coil to high-temperature heat treatment.

[0141] (Characteristics of conductive coils)

[0142] Volume resistivity

[0143] There is no particular limitation on the volume resistivity of the conductive coil, as long as the value is suitable for a very small current flow. The inventors conducted research and confirmed that the resonant frequency remained essentially unchanged when using copper with a volume resistivity of 1.55 μΩcm (0°C) and tungsten with a volume resistivity of 4.9 μΩcm (0°C). For example, when using carbon (graphite), the volume resistivity is 3352.8 μΩcm (20°C).

[0144] Thermal conductivity

[0145] There are no particular limitations on the thermal conductivity of the conductive coil. The inventors conducted research and confirmed that the resonant frequency remained essentially unchanged when using copper (394 W / m·K) and tungsten (174.3 W / m·K).

[0146] [Adhesive]

[0147] (Composition of adhesives)

[0148] There are no particular restrictions on the type of adhesive as long as it can bond multiple conductive coils and is non-conductive. Examples include organic materials such as polymers or inorganic materials such as glass. From the viewpoint of ease of molding, organic materials are preferred, and polymer materials are more preferred.

[0149] There are no particular limitations on the form of the adhesive. It can be a sheet formed by cooling and curing molten thermoplastic resin, a sheet formed by molding thermosetting or photocurable resins obtained by polymerizing low-molecular-weight monomers through heating or light exposure, or a sheet formed by solidifying fibers such as nanofibers. In the cases of curing by cooling thermoplastic resin, curing by heating thermosetting resin, and curing by polymerizing low-molecular-weight monomers, the conductive coils tend to be unevenly distributed downwards due to their own weight during the curing process. On the other hand, if fibers such as nanofibers are cured into a specific shape, such uneven distribution of conductive coils during the curing process is less likely to occur. Therefore, it is less likely for the conductive coils to come into contact, and the desired electromagnetic wave shielding performance and insulation properties can be easily obtained.

[0150] Furthermore, if the dielectric constant is large, the apparent wavelength becomes shorter. Therefore, from the viewpoint of being able to achieve shielding at higher frequencies, inorganic materials are preferred, such as glass or ceramics.

[0151] When using resin, it can be either a thermosetting resin or a thermoplastic resin. However, since high temperatures may sometimes be required depending on the application of the electromagnetic wave shielding sheet, a thermosetting resin is preferred. Examples of thermosetting resins include thermosetting resins and photocurable resins. Further examples of thermosetting resins include thermosetting acrylic resins, unsaturated polyester resins, epoxy resins, melamine resins, phenolic resins, silicone resins, polyimide resins, or urethane resins. Examples of photocurable resins include photocurable epoxy resins, photocurable polyesters, photocurable vinyl compounds, photocurable epoxy (meth)acrylates, or photocurable urethane (meth)acrylates. Among these, unsaturated polyester resins, photocurable polyesters, epoxy resins, or photocurable epoxy resins are preferred, especially from the viewpoint of heat resistance, epoxy resins or photocurable epoxy resins are preferred. These resins can be used alone or in combination of two or more types and ratios.

[0152] There are no particular limitations on the types of materials used for nanofibers; examples include cellulose, polypropylene, polyethylene terephthalate, chitin, chitosan, or aromatic polyamides. From the viewpoint of easily ensuring insulation and easily suppressing the settling of coils with a higher specific gravity than adhesives, cellulose nanofibers, polypropylene nanofibers, or polyethylene terephthalate nanofibers are preferred, with cellulose nanofibers being particularly preferred.

[0153] From the perspective of preventing environmental pollution, the adhesive is preferably a biodegradable material. Examples of biodegradable materials include cellulose, with cellulose being the most preferred.

[0154] There is no particular limitation on the content of adhesive in the film. From the viewpoint of ensuring sufficient electromagnetic wave shielding, it is usually 15% by mass or more, preferably 20% by mass or more, more preferably 22% by mass or more, usually 99% by mass or less, preferably 95% by mass or less, more preferably 90% by mass or less.

[0155] In particular, when using nanofibers as a binder, there is no particular limitation on the binder content in the sheet. From the viewpoint of ensuring sufficient electromagnetic wave shielding, it is generally 15% by mass or more, preferably 20% by mass or more, more preferably 22% by mass or more, generally 40% by mass or less, preferably 35% by mass or less, more preferably 30% by mass or less.

[0156] In addition, especially when using resins other than nanofibers as adhesives, the adhesive content in the sheet is not particularly limited. From the viewpoint of ensuring sufficient electromagnetic wave shielding, it is generally 40% by mass or more, preferably 50% by mass or more, more preferably 55% by mass or more, generally 99% by mass or less, preferably 95% by mass or less, more preferably 90% by mass or less.

[0157] When fibers are used as adhesives, cross-linking can occur between the fibers. That is, the adhesive can contain cross-linked fibers, or it can be cross-linked fibers themselves. There are no particular limitations on the type of cross-linking; for example, cross-linking based on covalent bonds or cross-linking based on ionic bonds can be cited.

[0158] The conductive coil can be completely embedded in the adhesive, or it can be partially embedded, meaning that part of the conductive coil is exposed to the external gas.

[0159] (Properties of adhesives)

[0160] Refractive index

[0161] There are no particular restrictions on the refractive index of the adhesive, but from the viewpoint of improving electromagnetic wave shielding, it is generally 1.35 or higher and 1.76 or lower, preferably 1.55 or higher and 1.61 or lower for epoxy resin. The refractive index can be measured by known methods.

[0162] Volume resistivity

[0163] There are no particular limitations on the volume resistivity of the adhesive, but from the point of view of ensuring insulation, a higher resistivity is preferred, for example, 10 is preferred. 6 Above Ω·cm. There is no particular upper limit to this volume resistivity; for example, it can be 10 Ω·cm. 20 Below Ω·cm, it can also be 10. 18 Below Ω·cm. The volume resistivity of the resin can be determined after preparing the sheet-like resin by the same method as for the volume resistivity of the sheet described later.

[0164] [piece]

[0165] (The composition of the film)

[0166] The shape of the sheet is not particularly limited as long as it is identifiable as a sheet, and can be appropriately changed depending on the occasion in which the sheet is set. The sheet can be a single-layer sheet or a stacked sheet. When making a stacked sheet, it can be a method of stacking multiple sheets of this embodiment, or it can be a method of stacking other sheets to provide various functions.

[0167] There is no particular limitation on the thickness of the sheet. From the perspective of miniaturization, lightness and thinness of electronic devices such as mobile phones, smartphones or tablets in recent years, it is usually 10μm or more, preferably 20μm or more, more preferably 50μm or more, and even more preferably 100μm or more. In addition, it is usually 10mm or less, preferably 5mm or less, more preferably 3mm or less, and even more preferably 1.5mm or less.

[0168] The sheet can be planar, but it can also have convex or concave shapes within a range that can be approximated as planar, and it can also be curved in some parts. In addition, the shape of the sheet as observed from the surface can be circular, or it can be polygonal, such as triangular or quadrilateral.

[0169] The sheet can be a block tightly filled with adhesives, conductive coils, and any other components, or it can be a porous body such as a foam.

[0170] There is no particular limit to the number of conductive coils in the film, but from the point of view of ensuring sufficient electromagnetic wave shielding, it is usually 50 coils / cm. 3 The above is preferably 100 pieces / cm. 3 The above, and more preferably 200 pieces / cm3 The above, and further preferred, is 300 pieces / cm. 3 In addition, the usual count is 10,000 pieces / cm. 3 The preferred value is 5000 pieces / cm. 3 The following, and more preferably, is 3000 pieces / cm 3 The following is a further preferred value: 1000 pieces / cm 3 the following.

[0171] The number of the aforementioned conductive coils can be determined by internal observation using CT-X-rays.

[0172] The sheet may also contain materials other than the conductive coils and adhesives mentioned above (other materials), such as inorganic fillers or resin fillers other than the conductive coils. For example, by adding inorganic fillers, not only can the contact between the conductive coils be suppressed, but the coefficient of linear expansion of the sheet can also be adjusted, thereby easily preventing warping, bending, and undulation of the sheet.

[0173] There are no particular restrictions on the content of inorganic fillers other than conductive coils in the film, and they can be contained arbitrarily within the range that can achieve the effects of this embodiment.

[0174] In addition, the sheet can contain air, that is, have voids, or it can be a foam. By making it into a foam, it is possible to achieve lightweighting.

[0175] (Characteristics of the film)

[0176] Electromagnetic wave shielding

[0177] In this disclosure, electromagnetic wave shielding performance is evaluated by assessing the power transmittance T(ω). This evaluation method is based on terahertz time-domain spectroscopy used in transmittance measurement experiments.

[0178] A schematic diagram of the terahertz time-domain spectrometer is shown below. Figure 6 In terahertz time-domain spectroscopy, the outputs from one or two femtosecond lasers are typically used as pump and probe beams. The pump beam acts as the excitation light for the terahertz wave. The probe beam ensures the timing of the terahertz wave measurement is synchronized. By varying the arrival times of the pump and probe beams, the electric field composition of the terahertz wave in the time domain can be measured. The electric field E of the terahertz wave after passing through the sample is then measured. sam (t), and the electric field E after passing through air without a sample. ref (t) is used for detection. These values ​​are then used to derive birefringence, complex permittivity, transmittance, power spectrum, etc.

[0179] Based on the data obtained from the above measurements, the transmittance was derived using Fourier transform. The resulting electric field waveform E was then calculated.sam (t), E ref (t) are subjected to Fourier transforms respectively, becoming E sam (ω) Eref (ω). The power transmittance T(ω) can be expressed using the following equation (A).

[0180] [Mathematical Expression 1]

[0181]

[0182] The aforementioned transmittance can be measured using a terahertz spectrophotometer (e.g., the ADVANTEST TAS7500TSH).

[0183] The shielding performance L (dB) can be calculated based on the power transmittance T (ω) and the following formula (B).

[0184] L = 10 × Log 10 (T(ω)) (B)

[0185] The shielding performance L is not particularly limited, but is typically -10dB or less, preferably -15dB or less. Furthermore, from the viewpoint of preventing malfunctions of electronic devices such as computers, it is preferably -20dB or less, more preferably -30dB or less, further preferably -40dB or less, particularly preferably -60dB or less, and even more particularly preferably -80dB or less. Additionally, a lower limit is not required, but it is typically -90dB or more. It should be noted that for electromagnetic wave shielding performance, -20dB (shielding efficiency: 90%) is expressed when the electromagnetic wave is 1 / 10, -40dB (shielding efficiency: 99%) when it is 1 / 100, -60dB (shielding efficiency: 99.9%) when it is 1 / 1000, and -80dB (shielding efficiency: 99.99%) when it is 1 / 10000.

[0186] Volume resistivity

[0187] The volume resistivity of the sheet can be measured using a resistivity meter (e.g., the Hiresta UX MCP-HT800 manufactured by Nitto Seiko Analytical Technology Co., Ltd.) and the double ring electrode method (two-terminal method), which involves clamping the molded body with a counter electrode and a double ring electrode.

[0188] There are no particular limitations on the volume resistivity of the sheet that can be measured by the above method. As mentioned above, from the viewpoint of preferably preventing current flow between conductive coils, a volume resistivity of 10 is preferred. 4 Ω·cm or more, more preferably 10 6 Ω·cm or higher, and more preferably 10 8Ω·cm or higher, preferably 10 10 Above Ω·cm. This volume resistivity does not require a specific upper limit, but can be, for example, 10 Ω·cm. 20 Below Ω·cm, it can also be 10. 18 Below Ω·cm.

[0189] <Method for manufacturing molded parts>

[0190] The following describes embodiments of various methods for manufacturing molded articles, but the methods described above are not limited to these methods. Furthermore, manufacturing conditions applicable to each embodiment can be applied interchangeably. Additionally, the conditions described above for the molded articles can be applied to the conditions of the following manufacturing methods within their applicable scope.

[0191] <Manufacturing Method 1>

[0192] The method for manufacturing a first molded body, as another embodiment of this disclosure (also referred to as the "first manufacturing method" in the description of this embodiment), is a method for manufacturing a molded body including the following steps:

[0193] A composition manufacturing process for obtaining a liquid composition containing an adhesive and a conductive coil;

[0194] This includes a curing process that solidifies the above-mentioned liquid composition.

[0195] Among them, the average ratio of the longest side to the shortest side in the smallest cuboid surrounding the aforementioned conductive coil is greater than 1 and less than 2.

[0196] The first manufacturing method may also include steps other than the composition preparation step and the curing step described above.

[0197] Furthermore, the first manufacturing method is particularly preferred when thermoplastic resin, thermosetting resin, or photocurable resin is used as the adhesive.

[0198] [Composition Preparation Process]

[0199] The first manufacturing method includes the composition preparation step described above for obtaining a liquid composition comprising an adhesive and a conductive coil. The method for obtaining the liquid composition comprising the adhesive and the conductive coil is not particularly limited; examples include methods such as mixing the liquid adhesive and the conductive coil, or dissolving the adhesive in a solvent to obtain a solution and then mixing the solution with the conductive coil. The mixing method is not particularly limited, and known methods can be used.

[0200] When using solvents, there are no particular restrictions on the type of solvent, as long as it can dissolve the aforementioned adhesive and other materials that need to be dissolved. It should be noted that if molding can be achieved without solvents, then solvents may not be used.

[0201] Additionally, depending on the type of adhesive used, a curing agent may be added. The type of curing agent can be appropriately chosen based on the adhesive used, and is a known type. The content of the curing agent in the composition can, for example, be set to 0.05 to 15% by mass.

[0202] In addition, depending on the type of adhesive used, polymerization initiators can also be added. For example, as a thermal polymerization initiator, thermal free radical generators such as benzoyl peroxide and other peroxides can be used, and as a photopolymerization initiator, photofree radical generators, photocation generators, or photoanion generators can be used.

[0203] As another embodiment of the present invention, the liquid composition is a liquid composition comprising an adhesive and a conductive coil.

[0204] In the smallest cuboid surrounding the conductive coil, the average ratio of the longest side to the shortest side is greater than 1 and less than 2.

[0205] There are no particular restrictions on its manufacturing method, and it can be obtained by the method described in the preparation process of this liquid composition.

[0206] Furthermore, as another embodiment of the present invention, the molded body is a cured product of the above-described liquid composition. The conditions for this molded body can be similarly applied to the conditions for the molded body described above.

[0207] [Curing Process]

[0208] The first manufacturing method includes a curing step that involves solidifying the aforementioned liquid composition. The curing method is not particularly limited and can be appropriately varied depending on the type of adhesive; for example, methods using heat or light such as ultraviolet light can be employed for curing. Furthermore, if the adhesive used is a thermoplastic resin and the aforementioned composition is prepared in a state where it is molten by applying heat, natural placement or cooling treatment can be used as curing methods. The curing temperature and time vary depending on the material used; there are no particular limitations as long as the temperature and time are sufficient to cure the composition.

[0209] <Second Manufacturing Method>

[0210] The second molding method, as another embodiment of this disclosure (also referred to as the "second manufacturing method" in the description of this embodiment), is a method for manufacturing a molding body including the following steps:

[0211] A composition preparation process for obtaining a liquid composition containing an adhesive and a conductive coil;

[0212] A freezing process in which the above-mentioned liquid composition is frozen to obtain a frozen finished article; and

[0213] The compression process involves applying a load to the frozen body to compress it, thereby obtaining a molded body.

[0214] Among them, the average ratio of the longest side to the shortest side in the smallest cuboid surrounding the aforementioned conductive coil is greater than 1 and less than 2.

[0215] The second manufacturing method may also include steps other than the composition preparation step, freezing step and compression step described above.

[0216] Furthermore, the second manufacturing method is particularly preferred when using fibers such as nanofibers as a binder. In this case, the resulting molded body is not a block, but a porous body such as a foam.

[0217] [Composition Preparation Process]

[0218] The second manufacturing method includes a composition preparation step to obtain the liquid composition comprising the adhesive and the conductive coil described above. This composition preparation step can be similarly subject to the conditions of the composition preparation step in the second manufacturing method described above.

[0219] In cases where fibers are used as adhesives, solvents must be used because the fibers need to be dissolved in the solvent.

[0220] [Freezing process]

[0221] The second manufacturing method includes a freezing step of freezing the above-mentioned liquid composition to obtain a cryogenically processed body. The purpose of this step is to efficiently obtain a porous body. It should be noted that, in this disclosure, a cryogenically processed body refers to a substance derived from a composition that has undergone cryogenic treatment. Therefore, even substances derived from a composition in a thawed, unfrozen state are also referred to as cryogenically processed bodies.

[0222] There are no particular limitations on the method of freezing liquid compositions; for example, placing a container containing a liquid composition in a cold storage room.

[0223] There are no particular restrictions on the shape of the frozen body, but from the viewpoint of being able to safely and effectively carry out compression in the compression process described later, a cylindrical shape, or a multi-faceted prism such as a quadrangular prism, pentagonal prism, or hexagonal prism is preferred.

[0224] There are no particular limitations on the freezing temperature, as long as it is sufficient to freeze the liquid composition. For example, it can be -196 to 0°C, -100 to -20°C, or -60 to -30°C.

[0225] There are no particular restrictions on the freezing time, as long as the liquid composition is frozen. For example, it can be more than 1 hour, more than 5 hours, or more than 10 hours. Alternatively, it can be less than 168 hours, less than 72 hours, or less than 24 hours.

[0226] [Immersion Process]

[0227] The second manufacturing method may include an immersion step between the aforementioned freezing step and the subsequent compression step, in which the frozen-treated body is immersed in a liquid containing components that crosslink the adhesive. The purpose of this step is to reduce the volume shrinkage of the frozen-treated body in steps prior to and after the subsequent compression step.

[0228] There are no particular limitations on the method of immersing the cryogenically treated body in a liquid containing a component that crosslinks the adhesive. Examples include: adding the cryogenically treated body to a container containing a liquid containing a component that crosslinks the adhesive, or adding a liquid containing a component that crosslinks the adhesive to a container in which the cryogenically treated body has been added.

[0229] The type of liquid containing the component that crosslinks the adhesive is not particularly limited, as long as it enables the adhesive to crosslink. Furthermore, the type of crosslinking is not particularly limited; examples include covalently based crosslinking and ionicly based crosslinking. Specific examples of liquids containing the component that crosslinks the adhesive include liquids containing polyvalent metal ions and acidic liquids. More specifically, examples include aluminum ion-containing liquids such as aluminum nitrate, aluminum sulfate, aluminum acetate, or aluminum chloride, aqueous solutions of copper nitrate and ferric nitrate, hydrochloric acid, or acetic acid. Especially when the adhesive is cellulose nanofibers, an acidic liquid is preferred, and aluminum nitrate is more preferred.

[0230] Furthermore, the impregnation process may include: after removing the liquid containing the component that crosslinks the adhesive (first liquid), immersing the frozen-processed body in a liquid other than that liquid (second liquid). If the frozen-processed body is compressed or dried while it is in the state of being coated with the liquid containing the component that crosslinks the adhesive, there is a risk of unintended volume shrinkage. Therefore, this process aims to prevent such shrinkage.

[0231] There are no particular limitations on the method for removing the first liquid. Examples include removing the first solution from a container containing the first liquid and the frozen body, or removing the frozen body from a container containing the first liquid and the frozen body.

[0232] There are no particular limitations on the method of immersing the frozen body in the second liquid. Examples include: adding the frozen body to a container containing the second liquid, or adding the second liquid to a container containing the frozen body.

[0233] There are no particular restrictions on the type of the second liquid, as long as it is compatible with the first liquid. Examples include organic solvents with a lower surface tension than water, such as ethanol, acetone, hexane, or pentane. Especially when the binder is cellulose nanofibers, liquids such as ethanol can be used. For example, when the first liquid is water, ethanol or acetone, which are compatible with water, can be used, but hexane, which is incompatible with water, cannot be used.

[0234] It should be noted that the replacement process using the second liquid can be performed more than twice. In this case, a liquid that is compatible with the liquid used in the previous process needs to be used for replacement. For example, when replacing water with hexane, it can be done by performing a two-step replacement, such as water → ethanol → hexane.

[0235] [Thawing process]

[0236] The second manufacturing method may include a step of thawing the frozen body described above. The thawing step may be included between the freezing step and the compression step, or it may be performed simultaneously with the impregnation step. Preferably, it is performed after impregnating the frozen body with a liquid containing a component that crosslinks the adhesive, and preferably before impregnating the frozen body with the second liquid.

[0237] There are no particular restrictions on the method of thawing; examples include heating and natural thawing by leaving the food to thaw.

[0238] There are no particular restrictions on the thawing temperature and thawing time, as long as the frozen mixture can be thawed. They can be set appropriately according to the type of composition.

[0239] [Compression Process]

[0240] The second manufacturing method includes a compression step of applying a load to the frozen-treated body and compressing it to obtain a molded body. The purpose of this step is to shape the frozen-treated body into a desired shape, particularly a sheet shape. There are no particular limitations on the method of compression, and known methods can be used, such as: compression using a press, compression by placing a plate on the frozen-treated body and placing a heavy object such as a weight on it, etc.

[0241] As long as the cryogenically processed body can be shaped into the desired form, there are no particular limitations on the compression pressure, for example, it can be 1~10MPa, 1.5~7MPa, or 2~5MPa.

[0242] There are no particular restrictions on the temperature at which compression can be performed; it can be at room temperature or above room temperature.

[0243] [Drying Process]

[0244] The second manufacturing method may include a drying step after the compression step to dry the molded body. The purpose of this step is to remove volatile components contained in the molded body. Furthermore, in the case of the impregnation step described above, the purpose is to allow the cross-linking of the adhesive components to occur. There are no particular limitations on the drying method; known methods can be used, such as drying the molded body in a dryer.

[0245] As long as the volatile components to be removed can be volatilized, and in the case of the above-mentioned impregnation process, as long as the cross-linking of the components that cross-link the adhesive can be carried out, there are no particular restrictions on the drying temperature and time. For example, the drying temperature can be 5~150°C, 10~100°C, or 15~50°C, and the drying time can be more than 1 hour, more than 5 hours, more than 10 hours, or less than 168 hours, less than 72 hours, or less than 24 hours.

[0246] From the perspective of manufacturing process efficiency, the drying process can be performed simultaneously with the compression process described above. That is, the frozen body can be compressed while being dried using heating or other methods.

[0247] <Applications of Molded Components>

[0248] Examples of uses for the molded body described above include electromagnetic wave shielding bodies, and another embodiment of the present invention is an electromagnetic wave shielding body having the molded body described above.

[0249] Another embodiment of the invention described in this application is as follows: having the above-described molded body

[0250] Semiconductor modules containing semiconductor devices (e.g., modules in which semiconductor elements are encapsulated and covered by a molded body in categories such as SOP, QFP, QFN, and BGA);

[0251] Smartphones, tablets, smartwatches, smart security devices, monitoring equipment, or smart home appliances, and other electronic or electrical communication devices;

[0252] Automotive equipment such as safety systems, mobile media, communications, wireless headsets, battery-powered, electric, hybrid powertrain systems, or high-voltage battery systems; consumer electronics such as computer circuits, wireless transmitters (including smartphones), electric motors, flat panel displays, or liquid crystal displays (LCDs);

[0253] Smart beds, ventilators, scanners, or other medical devices that require acquiring information such as pulse and blood pressure and converting it into electronic signals;

[0254] Aerospace equipment such as aircraft, vehicles, elastomer gaskets, conductive coatings, or EMI shielding displays;

[0255] Railway systems, mass transportation systems, high-voltage contact switch systems, signal transmission systems, or control systems, etc.; or

[0256] Other equipment (equipment capable of forming bodies other than those mentioned above); etc.

[0257] There are no particular limitations on the way the molded body is used in the above embodiments, as long as it is used as a component. In addition, in each embodiment, the molded body is particularly preferably used for electromagnetic wave shielding sheets.

[0258] Especially when used as an electromagnetic wave shielding sheet, it can be used arbitrarily for any purpose of shielding electromagnetic waves. For example, by setting the electromagnetic wave shielding sheet to surround electronic devices that may malfunction due to electromagnetic waves, such malfunctions can be suppressed. In particular, compared with existing electromagnetic wave shielding sheets, the above-described electromagnetic wave shielding sheet has superior shielding of high-frequency electromagnetic waves. Therefore, from the viewpoint of being able to shield electromagnetic waves from communication devices such as mobile phones and smartphones that have been upgraded to higher frequencies, especially to frequencies above 100 GHz, for the purpose of high speed, large capacity, and low latency, it can be applied to a wider range of fields than existing electromagnetic wave shielding sheets. It should be noted that for the above-described sheet, a particularly large electromagnetic wave shielding effect can be obtained when the direction of electromagnetic waves coming from the outside is perpendicular to the plane of the sheet.

[0259] Example

[0260] The following embodiments illustrate this disclosure in more detail. However, this disclosure is not intended to be limited to these embodiments.

[0261] <Materials Used>

[0262] [Adhesive]

[0263] • Adhesive 1: Epoxy resin (a mixture of cold-embedded resin JP-21111001 (polyester resin, refractive index 1.69 at 500 GHz) manufactured by Stell Co., Ltd. and curing agent (M agent) manufactured by Stell Co., Ltd.; the mixing ratio is cold-embedded resin: curing agent = 100 ml: 1.5 ml, and the curing time is 40 minutes at room temperature.)

[0264] • Adhesive 2: Cellulose nanofibers (cellulose nanofibers / aqueous dispersion (cellulose nanofiber content: 1% by mass), RHEOCRYSTA I-2SX, manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd., with a length exceeding 100 μm and less than 3 mm, and a fiber diameter of 3 nm.

[0265] • Adhesive 3: Light-curing resin (Clear Resin V4, manufactured by Formlab)

[0266] [Conductive coil]

[0267] • Single coil: As the single coil in each embodiment, a tungsten single coil with the form shown in the tables below is used (core wire cross-sectional shape: circular, helix circumferential shape: circular).

[0268] • Dual coil: As the dual coil in each embodiment, a tungsten dual coil with the form shown in the tables below is used (core wire cross-sectional shape: circular, large helix circumferential shape: circular, small helix circumferential shape: circular).

[0269] In the tables described below, "total length" refers to "the average length of the coil-shaped portion along the central axis of the conductive coil in a single coil, and "the average length of the double coil along the central axis of the large helix in a double coil."

[0270] Additionally, the “average ratio of the cuboid” in the tables described later refers to “the average ratio of the longest side to the shortest side in the smallest cuboid surrounding the conductive coil.”

[0271] In addition, the values ​​of the parameters related to the shape of the conductive coil in the tables described below are all average values.

[0272] Furthermore, the average core length of each coil in the tables described later can be calculated as follows: In the case of a single coil, the value is obtained by multiplying the coil's outer diameter by pi and then multiplying the resulting value by the number of turns in the coil. In the case of a double coil, the value is obtained by multiplying the outer diameter of the smaller helix by pi and then multiplying the resulting value by the number of turns in the smaller helix. The number of turns in the smaller helix is ​​obtained by multiplying the outer diameter of the larger helix by pi and then multiplying the resulting value by the number of turns in the larger helix, and then dividing the resulting value by the pitch of the smaller helix.

[0273] For cases where a double coil is further shaped into a triple coil or a coil of a special shape, the core wire length can also be calculated mathematically in the same way.

[0274] The total core length of the coils per unit volume is obtained by multiplying the average core length of each coil by the coil number density per unit volume. The coil number density per unit volume can be calculated by dividing the number of coils in the molded body by the volume. The coil number density per unit volume can also be the average of the coil number densities at any location in the molded body.

[0275] <Characteristic Evaluation>

[0276] Electromagnetic wave shielding performance

[0277] The electromagnetic wave shielding performance was evaluated by measuring the power transmittance T(ω) using a terahertz spectrometer (TAS7500TSH, ADVANTEST). A 5mm diameter aperture was used. The sample used for the measurement was a material obtained by cutting the aforementioned sheets into cuboids with 30mm sides and a thickness of 1mm.

[0278] Next, based on the power transmittance T(ω) obtained by measurement, the shielding performance L(dB) was calculated according to the following formula (B).

[0279] L = 10 × Log 10 (T(ω)) (B)

[0280] The evaluation results of the electromagnetic wave shielding performance L of each panel are shown in the respective tables. It should be noted that the shielding performance L shown in each table is a value obtained by evaluating at a frequency of 300 GHz.

[0281] [Volume Resistivity]

[0282] The volume resistivity of the sheet was measured using a resistivity meter (Hiresta UXMCP-HT800 manufactured by Nitto Seiko Analytical Technology Co., Ltd., with an upper limit of 10). 11The Ω·cm was measured using the double ring electrode method (two-terminal method), which involves clamping the molded body with a resitable electrode and a double ring electrode (URSS probe).

[0283] [Shape of the conductive coil]

[0284] The shape of the conductive coil was evaluated using optical microscopy and scanning electron microscopy.

[0285] At this point, the number of conductive coils being measured should be at least 10.

[0286] <Experiment A: Study on the average ratio of the longest side to the shortest side in the smallest cuboid surrounding a conductive coil>

[0287] [Film Production]

[0288] To achieve the content of the twin coils and adhesive shown in Table 1-2, the twin coils were inserted into an acrylic mold with a circular hole having a diameter of 20 mm and a thickness of approximately 1 mm, and then adhesive 1 was filled in. After curing at room temperature for 40 minutes, the cured sheet (20 mm in diameter and the sample thickness described in Table 1-2) was removed from the mold, yielding the sheet samples for evaluation of Example 1 and Comparative Example 1.

[0289] The evaluation results of electromagnetic wave shielding performance and volume resistivity are shown in Table 1-2. Additionally, the coordinate graph obtained from the evaluation of electromagnetic wave shielding performance is plotted in... Figure 7 .

[0290] It should be noted that, in Figure 7 In the coordinate graph, the region above 0 on the vertical axis shows the coordinates of reflectivity (%), transmittance (%), and absorptivity (%), while the region below 0 shows the coordinates of shielding performance (dB). Reflectivity (%), transmittance (%), and absorptivity (%) above 0% are shown, and shielding performance below 0dB is shown. This is in Figures 8-10 The same applies to China.

[0291]

[0292]

[0293] As shown in Tables 1-1 and 1-2, a sheet with excellent electromagnetic wave shielding and insulation properties can be manufactured by using a conductive coil in the smallest cuboid surrounding the conductive coil, where the average ratio of the longest side to the shortest side is less than 2.

[0294] <Experiment B: Study on the Content of Conductive Coils>

[0295] [Film Production]

[0296] The conditions of adhesive 1 and conductive coil were changed to those shown in Tables 2-1 and 2-2. Otherwise, the evaluation sheet samples of Examples 2 and 3 were obtained by the same method as in Example 1 above.

[0297] The evaluation results of electromagnetic wave shielding performance and volume resistivity are shown in Table 2-2. Additionally, the coordinate graph obtained from the evaluation of electromagnetic wave shielding performance is plotted in... Figure 8 .

[0298]

[0299]

[0300] As shown in Tables 2-1 and 2-2, the electromagnetic wave shielding performance improves while maintaining insulation performance as the content of conductive coils increases.

[0301] <Experiment C: Study of Adhesive 2>

[0302] [Film Production]

[0303] The adhesive 2 and conductive coil were weighed according to the mass values ​​shown in Table 3-2, and mixed to obtain a mixed aqueous dispersion. The mass of the adhesive 0.1 g shown in Table 3-2 is the mass of the cellulose nanofibers, which is 10 g based on the mass of the weighed cellulose nanofibers / aqueous dispersion. Next, the mixed aqueous dispersion was filled into a cylindrical plastic container with an inner diameter of 20 mm and a height of 50 mm, and frozen at -45°C for 2 hours to obtain a cryogenically treated body. Next, a hydrogel formed by cross-linking cellulose nanofibers using aluminum ions was prepared by thawing the cryogenically treated body in a 0.1 mol / L aluminum nitrate aqueous solution. The obtained hydrogel was washed with distilled water to remove the aluminum nitrate. Then, the hydrogel was immersed in 99% ethanol to replace the water with ethanol solvent to obtain an alcohol gel. The obtained alcohol gel was dried at 20°C and atmospheric pressure for 24 hours under a load of 3.2 kPa to achieve the thickness shown in Table 3-2 to prepare a foamed body, which yielded the evaluation sheet samples of Examples 4-6.

[0304] The evaluation results of electromagnetic wave shielding performance and volume resistivity are shown in Table 3-2. Additionally, the coordinate graph obtained from the evaluation of electromagnetic wave shielding performance is plotted in... Figure 9 .

[0305]

[0306]

[0307] As shown in Tables 3-1 and 3-2, excellent electromagnetic wave shielding performance can be obtained while maintaining insulation when adhesive 2 is used. In particular, when nanofibers are used as the adhesive, the nanofibers are sandwiched between the conductive coils. Therefore, compared with the case where adhesives other than nanofibers are used, it is easier to suppress the contact between the conductive coils and improve the orientation rate of the conductive coils while maintaining insulation.

[0308] <Experiment D>

[0309] [Film Production]

[0310] To achieve the conductive coil and adhesive content shown in Table 4-2, a conductive coil was inserted into an acrylic mold with a circular hole having a diameter of 20 mm and a thickness of approximately 1 mm, and then adhesive 3 was filled in. The adhesive 3 was then cured by irradiating the mold with ultraviolet light (Formlab, Form Cure) for 1 hour to obtain the first layer (layer 1, diameter 20 mm, thickness 1 mm). Then, a conductive coil and adhesive 3 were inserted into layer 1 in the same amounts as those in layer 1. The adhesive 3 was then cured by irradiating the mold with ultraviolet light (Formlab, Form Cure) for 1 hour to obtain the second layer (layer 2, diameter 20 mm, thickness 1 mm). Finally, a third layer (layer 3, diameter 20 mm, thickness 1 mm) was formed on layer 2 using the same method as layer 2, resulting in a laminate. Then, the laminated sheet (20 mm in diameter and the thickness of the sample recorded in Table 4-2) was removed from the mold to obtain the laminated sheet samples for evaluation in Examples 7-11.

[0311] The evaluation results of electromagnetic wave shielding performance and volume resistivity are shown in Table 4-2. Additionally, the coordinate graph obtained from the evaluation of electromagnetic wave shielding performance is plotted in... Figure 10 .

[0312] It should be noted that in Table 4-1, regarding Example 11 which uses a single coil, the outer diameter of the single coil is shown in the column for the outer diameter of the small helix, and the pitch width of the single coil is shown in the column for the pitch width of the small helix.

[0313]

[0314]

[0315] As shown in Tables 4-1 and 4-2, excellent electromagnetic wave shielding performance can be achieved while maintaining insulation, even when adhesive 3 is used and a single coil is employed. Furthermore, it is evident that longer total core wire length (coil) and longer total core wire length (volume) result in superior electromagnetic wave shielding performance.

Claims

1. A molded body comprising a binder and a plurality of electrically conductive coils, an average ratio of a longest side to a shortest side in a smallest rectangular parallelepiped that encloses the electrically conductive coils is 1 or more and 2 or less.

2. The molded body according to claim 1, wherein the binder comprises cellulose nanofiber.

3. The molded body according to claim 1 or 2, wherein an average number of turns of the electrically conductive coils is 1.2 or more and 50 or less.

4. The molded body according to claim 1 or 2, wherein an electrically conductive member that constitutes the electrically conductive coils is spiral.

5. The molded body according to claim 1 or 2, wherein The content of the electrically conductive coil in the molded body is 0.02 g / cm 3 above and less than 5.00 g / cm 3 .

6. The molded body according to claim 1 or 2, which is an electromagnetic wave shielding sheet.

7. A liquid composition comprising a binder and an electrically conductive coil, an average value of a ratio of a longest side to a shortest side in a smallest rectangular parallelepiped that encloses the electrically conductive coils is 1 or more and 2 or less.

8. A molded body that is a cured product of the liquid composition according to claim 7.

9. The molded body according to claim 8, which is an electromagnetic wave shielding sheet.

10. An electromagnetic wave shielding body having the molded body according to claim 6.

11. A semiconductor module having the molded body according to claim 1 or 2.

12. An electronic device having the molded body according to claim 1 or 2.

13. An automotive device having the molded body according to claim 1 or 2.

14. A consumer electronic device having the molded body according to claim 1 or 2.

15. A medical device having the molded body according to claim 1 or 2.

16. An aerospace device having the molded body according to claim 1 or 2.

17. A system having the molded body according to claim 1 or 2.

18. A method for manufacturing a molded body, the method comprising: a composition preparation step of obtaining a liquid composition comprising a binder and an electrically conductive coil; a freezing step of freezing the liquid composition to obtain a frozen processed product; and a compression step of compressing the frozen processed product by applying a load to the frozen processed product to obtain a molded body, wherein an average value of a ratio of a longest side to a shortest side in a smallest rectangular parallelepiped that encloses the electrically conductive coils is 1 or more and 2 or less.

19. The method for manufacturing a molded body according to claim 18, wherein between the freezing step and the compression step, an immersion step of immersing the frozen processed product in a liquid containing a component that crosslinks the binder is included.

20. The method according to claim 19, wherein in the immersion step, a process of immersing the frozen processed product in a liquid other than the liquid containing the component that crosslinks the binder after the liquid is removed is included.

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