Hollow structural film, circuit board, antenna equipment, and method for producing hollow structural film

Abstract

A hollow structural film 1 which has a hollow structure comprises: a first base part 11 which is in sheet form; a second base part 12 which coincides with the first base part 11 and which is in sheet form; and a plurality of column parts 20 which are provided between the first base part 11 and the second base part 12. The first base part 11 has a first facing surface 11a which faces the second base part 12. The second base part 12 has a second facing surface 12a which faces the first base part 11. At least some of the plurality of column parts 20 constitute a continuous column part 23 which extends from the first facing surface 11a to the second facing surface 12a.

Description

Hollow structure film, circuit board, antenna material, and method for manufacturing hollow structure film

[0001] The present disclosure relates to a hollow structure film, a circuit board, an antenna material, and a method for manufacturing the hollow structure film.

[0002] In recent years, there has been a demand for high-speed transmission and reception of large amounts of data in information and communication devices, etc. In response to this background, increasing the frequency of electrical signals has been considered.

[0003] In particular, when using communication standards equivalent to 5G in the standards for communication systems defined by the International Telecommunication Union (ITU), in Japan, telecommunications carriers are allocated the 4.5 GHz and 28 GHz bands, which are higher frequency bands than the 3.7 GHz band allocated to communication standards prior to 4G.

[0004] In contrast, conventional circuit boards designed primarily for communications using low-frequency bands often have a relatively high dielectric constant. The higher the dielectric constant, the greater the propagation delay of electrical signals. Therefore, a low dielectric constant is preferable to increase the propagation speed of electrical signals and enable high-speed calculations. For these reasons, there is a demand for circuit boards with a lower dielectric constant than conventional ones to enable large-capacity, high-speed communications using circuit boards used in high-frequency bands.

[0005] Furthermore, when the dielectric constant of a circuit board is high, the transmission loss of high-frequency current generated in the circuit tends to be large. Therefore, when attempting communication using the same amount of current, the higher the dielectric constant of the circuit board, the greater the loss of radio waves, resulting in weaker radio waves usable for communication. As a result, the higher the dielectric constant of the circuit board, the more likely it is that inconveniences such as a shorter communication distance will occur.

[0006] Known examples of sheets that can be used for circuit boards and have a dielectric constant lower than conventional ones include sheets manufactured by forming a resin foam containing air bubbles, such as the low dielectric sheet for two-dimensional communication disclosed in Patent Document 1.

[0007] Patent No. 5976714

[0008] There has been a demand for films used in circuit boards that have a low dielectric constant while maintaining strength.

[0009] The present disclosure has been made in consideration of the above points, and aims to provide a film that has a low dielectric constant while ensuring strength.

[0010] Embodiments of the present disclosure relate to the following [1] to

[35] .

[0011] [1] A hollow structure film having a hollow structure, comprising: a sheet-like first base; a sheet-like second base overlapping the first base; and a plurality of support columns provided between the first base and the second base, wherein the first base has a first opposing surface facing the second base, and the second base has a second opposing surface facing the first base, and at least some of the plurality of support columns form continuous support columns extending from the first opposing surface to the second opposing surface.

[0012] [2] The support portion extends in a first direction perpendicular to the thickness direction of the hollow structure film, and in a cross section of the hollow structure film cut through the support portion and perpendicular to the first direction, the angle formed between the surface of the first base and the portion of the surface of the support portion connected to the first base is 90° or more and 150° or less, and in a cross section of the hollow structure film cut through the support portion and perpendicular to the first direction, the angle formed between the surface of the second base and the portion of the surface of the support portion connected to the second base is 90° or more and 150° or less.

[0013] [3] The hollow structure film according to [1] or [2], wherein the hollow structure film comprises a main body portion, the main body portion comprises the first base portion, the second base portion, the plurality of support portions, and a sheet-like central portion located between the first opposing surface and the second opposing surface, and the plurality of support portions are located on the first opposing surface side and the second opposing surface side of the central portion.

[0014] [4] The hollow structure film according to any one of [1] to [3], having a thickness of 50 μm or more and 1000 μm or less.

[0015] [5] At least one of the first base portion, the second base portion, and the support portion has a strength of 940 kg / m ３ a first resin material having a greater density than 925 kg / m ３ The hollow structure film according to any one of [1] to [4], further comprising a second resin material having the following density:

[0016] [6] Storage modulus is 1.0 × 10 5 The hollow structure film according to any one of [1] to [5], wherein the elastic modulus is 100 Pa or more.

[0017] [7] The hollow structure film according to any one of [1] to [6], which contains glass particles.

[0018] [8] The hollow structure film according to [7], wherein the glass particles have hollow portions.

[0019] [9] The hollow structure film according to any one of [1] to [8], which contains a compound having a double bond active to radiation or a thermal radical initiator.

[0020]

[10] The hollow structure film according to any one of [1] to [9], having a porosity of 20% or more.

[0021]

[11] The hollow structure film has a first surface and a second surface located opposite to the first surface, and further comprises a metal layer constituting at least a part of at least one of the first surface and the second surface. [1] The hollow structure film according to any one of [1] to

[10] .

[0022]

[12] The hollow structure film described in

[11] further comprises a metal adjacent layer that joins the metal layer to at least one of the first base and the second base, and the material of the metal adjacent layer is different from the material of the first base and the second base.

[0023]

[13] The hollow structure film according to

[11] or

[12] , further comprising a metal adjacent layer that joins the metal layer to at least one of the first base and the second base, wherein the material of the metal adjacent layer is an adhesive.

[0024]

[14] The hollow structure film according to any one of

[11] to

[13] , further comprising an ionomer layer or an ethylene (meth) acrylic acid copolymer layer that bonds the metal layer to at least one of the first base and the second base.

[0025]

[15] The hollow structure film according to any one of

[11] to

[14] , wherein at least one of the following conditions is satisfied: the transmission loss value of an electric signal having a frequency of 10 GHz applied to the linear wiring formed from the metal layer is greater than -0.30 dB / 3.5 cm; the transmission loss value of an electric signal having a frequency of 20 GHz applied to the linear wiring is greater than -0.60 dB / 3.5 cm; the transmission loss value of an electric signal having a frequency of 30 GHz applied to the linear wiring is greater than -0.90 dB / 3.5 cm; the transmission loss value of an electric signal having a frequency of 40 GHz applied to the linear wiring is greater than -1.30 dB / 3.5 cm; the transmission loss value of an electric signal having a frequency of 50 GHz applied to the linear wiring is greater than -1.80 dB / 3.5 cm; and the transmission loss value of an electric signal having a frequency of 60 GHz applied to the linear wiring is greater than -3.00 dB / 3.5 cm.

[0026]

[16] A circuit board comprising: a hollow structure film according to any one of [1] to

[10] , the hollow structure film having a first surface and a second surface located on the opposite side of the first surface; and a wiring pattern provided on at least one of the first surface and the second surface.

[0027]

[17] An antenna device comprising: the circuit board according to

[16] ; and an antenna element connected to the circuit board.

[0028]

[18] A method for producing a hollow structure film having a hollow structure, comprising: a step of using a mold to produce a pair of single-sided shaped bodies each having a sheet-like base and a plurality of convex portions formed on one side of the base; and a step of overlapping the pair of single-sided shaped bodies so that the convex portions at least partially face each other, and heat-pressing the overlapping bodies together.

[0029]

[19] A hollow structure film having a hollow structure, comprising: a main body portion having a sheet-like first base portion, a sheet-like second base portion overlapping the first base portion, and a plurality of support portions provided between the first base portion and the second base portion, wherein the first base portion has a first opposing surface opposing the second base portion, and the second base portion has a second opposing surface opposing the first base portion, at least some of the plurality of support portions form continuous support portions extending from the first opposing surface to the second opposing surface, and the main body portion includes an insulating inorganic material member, and the maximum width of the inorganic material member is three times or more the minimum width of the inorganic material member.

[0030]

[20] The hollow structure film according to

[19] , wherein the inorganic material member is included in at least one of the first base and the second base.

[0031]

[21] The hollow structure film according to

[19] or

[20] , wherein the inorganic material member is included in at least a part of the plurality of support parts.

[0032]

[22] The hollow structure film according to any one of

[19] to

[21] , wherein the main body further has a sheet-like central portion located between the first opposing surface and the second opposing surface, and the plurality of support portions are located on the first opposing surface side and the second opposing surface side of the central portion.

[0033]

[23] The hollow structure film according to

[22] , wherein the inorganic material member is included in at least the central portion.

[0034]

[24] The hollow structure film according to any one of

[19] to

[23] , wherein the inorganic material member contains glass.

[0035]

[25] The hollow structure film according to any one of

[19] to

[24] , wherein the maximum width of the inorganic material member is 10 μm or more.

[0036]

[26] The hollow structure film according to any one of

[19] to

[25] , wherein the main body contains polyolefin.

[0037]

[27] The hollow structure film according to any one of

[19] to

[26] , having a thickness of 50 μm or more and 1000 μm or less.

[0038]

[28] The hollow structure film according to any one of

[19] to

[27] , having a porosity of 20% or more.

[0039]

[29] The hollow structure film has a first surface and a second surface located opposite to the first surface, and further comprises a metal layer constituting at least a part of at least one of the first surface and the second surface. The hollow structure film according to any one of

[19] to

[28] .

[0040]

[30] The hollow structure film described in

[29] further comprises a metal adjacent layer that joins the metal layer to at least one of the first base and the second base, and the material of the metal adjacent layer is different from the material of the first base and the second base.

[0041]

[31] The hollow structure film according to

[29] or

[30] , further comprising a metal adjacent layer that joins the metal layer to at least one of the first base and the second base, wherein the material of the metal adjacent layer is an adhesive.

[0042]

[32] The hollow structure film according to any one of

[29] to

[31] , further comprising an ionomer layer or an ethylene (meth) acrylic acid copolymer layer that bonds the metal layer to at least one of the first base and the second base.

[0043]

[33] A circuit board comprising: a hollow structure film according to any one of

[19] to

[28] , the hollow structure film having a first surface and a second surface located on the opposite side of the first surface; and a wiring pattern provided on at least one of the first surface and the second surface.

[0044]

[34] An antenna device comprising: the circuit board according to

[33] ; and an antenna element connected to the circuit board.

[0045]

[35] A method for producing a hollow structure film having a hollow structure, comprising: a step of using a mold to produce a pair of single-sided shaped bodies having a sheet-like base and a plurality of convex portions formed on one side of the base, and including an insulating inorganic material member; and a step of overlapping the pair of produced single-sided shaped bodies so that the plurality of convex portions face each other at least in part, and thermocompressing the overlapped bodies, wherein the maximum width of the inorganic material member is three times or more the minimum width of the inorganic material member.

[0046] Effect of the Invention According to the embodiments of the present disclosure, a film having a low dielectric constant while ensuring strength can be provided.

[0047] FIG. 1 is a cross-sectional view of a hollow structure film according to an embodiment. FIG. 2 is a plan view showing a base of a hollow structure film according to an embodiment. FIG. 3 is a diagram showing an example of an image of a cross section of a hollow structure film according to an embodiment. FIG. 4 is a cross-sectional view of a hollow structure film according to an embodiment. FIG. 5 is a cross-sectional view of a hollow structure film according to an embodiment. FIG. 6A is a perspective view of a hollow structure film in which a transmission loss of an electric signal is measured. FIG. 6B is a diagram showing a method for measuring the transmission loss of an electric signal in a hollow structure film. FIG. 6C is a perspective view of an antenna device according to an embodiment. FIG. 7A is a diagram showing a method for manufacturing a hollow structure film according to an embodiment. FIG. 7B is a diagram showing a method for manufacturing a hollow structure film according to an embodiment. FIG. 8A is a diagram showing a method for manufacturing a hollow structure film according to an embodiment. FIG. 8B is a diagram showing a method for manufacturing a hollow structure film according to an embodiment. FIG. 8C is a diagram showing a method for manufacturing a hollow structure film according to an embodiment. FIG. 9 is a plan view showing a base of a hollow structure film according to Modification 1. FIG. 10 is a cross-sectional view of a hollow structure film according to Modification 2. FIG. 11 is a diagram showing a method for manufacturing a hollow structure film according to Modification 3. FIG. 12 is a cross-sectional view showing a hollow structure film according to Modification 3. FIG. 13 is a diagram showing a method for manufacturing a hollow structure film according to Modification 4. FIG. 14 is a cross-sectional view showing a hollow structure film according to Modification 4. FIG. 15 is a diagram showing a method for manufacturing a hollow structure film according to Modification 5. FIG. 16 is a cross-sectional view showing a hollow structure film according to Modification 5. FIG. 17 is a cross-sectional view showing a hollow structure film according to Modification 6. FIG. 18 is a cross-sectional view showing a hollow structure film according to Modification 6. FIG. 19 is a diagram showing a method for manufacturing a hollow structure film according to Modification 6. FIG. 20 is a diagram showing a method for manufacturing a hollow structure film according to Modification 6. FIG. 21A is a plan view showing a hollow structure film according to Modification 7. FIG. 21B is a perspective view showing a one-sided shaped object according to Modification 7. FIG. 22A is a plan view showing a hollow structure film according to Modification 7. FIG. 22B is a plan view showing a hollow structure film according to Modification 7. FIG. 22C is a plan view showing a hollow structure film according to Modification 7.Fig. 22D is a perspective view showing a single-sided shaped object according to Modification 7. Fig. 23A is a plan view showing a hollow structure film according to Modification 8. Fig. 23B is a plan view showing a hollow structure film according to Modification 8. Fig. 23C is a plan view showing a hollow structure film according to Modification 8. Fig. 23D is a perspective view showing a single-sided shaped object according to Modification 8. Fig. 23E is a perspective view showing a single-sided shaped object according to Modification 8. Fig. 23F is a perspective view showing a single-sided shaped object according to Modification 8. Fig. 24 is a diagram showing a method for an evaluation test of antenna performance. Fig. 25 is a diagram showing a method for a measurement test of CTE.

[0048] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings. In the drawings accompanying this specification, the scale and aspect ratios of the actual objects have been appropriately changed and exaggerated for the sake of ease of illustration and understanding.

[0049] Terms used in this specification that specify shapes and geometric conditions, as well as their degrees, such as terms like "parallel," "perpendicular," and "same," and values ​​of lengths and angles, are not to be construed as being bound by strict meanings, but rather as including a range within which similar functions can be expected.

[0050] In this specification, terms such as "film," "sheet," and "plate" are not to be distinguished from one another solely on the basis of differences in name.

[0051] In this specification, when multiple upper limit value candidates and multiple lower limit value candidates are listed for a certain parameter, the numerical range of the parameter may be constructed by combining any one upper limit value candidate with any one lower limit value candidate. As an example, consider the following statement: "Parameter B may be A1 or more, A2 or more, or A3 or more. Parameter B may be A4 or less, A5 or less, or A6 or less." In this example, the numerical range of parameter B may be A1 or more and A4 or less, A1 or more and A5 or less, A1 or more and A6 or less, A2 or more and A4 or less, A2 or more and A5 or less, A2 or more and A6 or less, A3 or more and A4 or less, A3 or more and A5 or less, or A3 or more and A6 or less.

[0052] In this specification, "suppress" means to restrain or prevent something from happening or occurring. "Suppress" does not only mean to completely prevent something from happening or occurring, but also means to reduce the possibility of something happening or occurring or to make something less likely to happen or occur.

[0053] <Hollow Structure Film> Figures 1 to 8C are diagrams illustrating one embodiment. Figure 1 is a cross-sectional view of a hollow structure film 1 according to this embodiment, taken along a cross section parallel to the thickness direction of the hollow structure film 1. The hollow structure film 1 has a hollow structure. As shown in Figure 1, the hollow structure film 1 includes a pair of sheet-like bases 10. The pair of bases 10 includes a first sheet-like base 11 and a second sheet-like base 12 overlapping the first base 11. Furthermore, the hollow structure film 1 includes a plurality of support columns 20 provided between the first base 11 and the second base 12. The hollow structure film 1 includes a main body 1c. In particular, the hollow structure film 1 shown in Figure 1 is made up of the main body 1c. The main body 1c includes the first base 11, the second base 12, and a plurality of support columns 20. As a result, the hollow structure film 1 includes a first base 11, a second base 12, and a plurality of support columns 20 as part of the main body 1c. The first base 11 has a first opposing surface 11a facing the second base 12. The second base 12 has a second opposing surface 12a facing the first base 11. At least some of the support columns 20 extend from the first opposing surface 11a to the second opposing surface 12a. In the example shown in FIG. 1, the hollow structure film 1 further includes a sheet-like central portion 30 that overlaps the first base 11 and the second base 12. In the example shown in FIG. 1, the main body 1c further includes a central portion 30. As a result, the hollow structure film 1 further includes a central portion 30 as part of the main body 1c. The central portion 30 is located between the first opposing surface 11a and the second opposing surface 12a.

[0054] In other words, the main body 1c includes the first base 11, the second base 12, a plurality of support columns 20, and a sheet-like central portion 30 located between the first opposing surface 11a and the second opposing surface 12a. The support columns 20 are located on the first opposing surface 11a side and the second opposing surface 12a side of the central portion 30.

[0055] By providing a plurality of support columns 20 between the first base 11 and the second base 12, the first base 11 and the second base 12 are connected via the support columns 20. Furthermore, the space between the first base 11 and the second base 12 is partitioned by the plurality of support columns 20, and a plurality of hollow sections B are formed between the first base 11 and the second base 12. This forms a hollow structure in the hollow structure film 1. The hollow structure of the hollow structure film 1 reduces the dielectric constant of the hollow structure film 1. This makes it possible to provide a hollow structure film 1 with a low dielectric constant while reducing the limitations on the material of the hollow structure film 1. In particular, a hollow structure film 1 with a low dielectric constant can be provided without using a specific material with a low dielectric constant as the material of the hollow structure film 1.

[0056] The hollow structure film 1 has a first surface 1a and a second surface 1b located on the opposite side to the first surface 1a. In the example shown in Fig. 1, the first base 11 constitutes the first surface 1a. The second base 12 constitutes the second surface 1b. The first base 11 and the second base 12 overlap in the thickness direction of the hollow structure film 1.

[0057] The plurality of support columns 20 are provided between a pair of bases 10, i.e., between the first base 11 and the second base 12. In the example shown in FIG. 1, the plurality of support columns 20 extend in the thickness direction of the hollow structure film 1. At least some of the plurality of support columns 20 extend from the first opposing surface 11a to the second opposing surface 12a. In the example shown in FIG. 1, at least some of the plurality of support columns 20 extend in the thickness direction of the hollow structure film 1 from the first opposing surface 11a to the second opposing surface 12a. The portions of the plurality of support columns 20 extending from the first opposing surface 11a to the second opposing surface 12a are referred to as continuous support columns 23. At least some of the plurality of support columns 20 constitute the continuous support columns 23 extending from the first opposing surface 11a to the second opposing surface 12a. When a straight line L1 extending from the first opposing surface 11a to the second opposing surface 12a can be drawn on a cross section of the hollow structure film 1 cut along a plane parallel to the thickness direction without protruding from the hollow structure film 1, the support section 20 through which the straight line L1 passes is considered to be a continuous support section 23. When the hollow structure film 1 has one or more cross sections in which a continuous support section 23 appears, at least a portion of the multiple support sections 20 in the hollow structure film 1 is considered to extend from the first opposing surface 11a to the second opposing surface 12a. The continuous support section 23 extends from the first opposing surface 11a to the second opposing surface 12a. The multiple support sections 20 may include portions that do not extend from the first opposing surface 11a to the second opposing surface 12a. 1 , the plurality of support columns 20 have first portions 21 that do not extend from the first opposing surfaces 11 a to the second opposing surfaces 12 a, and that extend from the first opposing surfaces 11 a to a first central surface 30 a of the central portion 30, which will be described later. The plurality of support columns 20 have second portions 22 that do not extend from one of the pair of bases 10 to the other, and that extend from the second base 12 to a second central surface 30 b of the central portion 30, which will be described later.

[0058] FIG. 2 is a plan view showing one of the pair of bases 10 (first base 11) of the hollow structure film 1 shown in FIG. 1 , observed from the thickness direction of the hollow structure film 1. The portion of the base 10 connected to the support 20 is referred to as the connection portion 24. The dashed line labeled 20a in FIG. 2 indicates the outline of the connection portion 24 of the first base 11 connected to the support 20. In the example shown in FIG. 2, multiple connection portions 24 extend in a first direction d1 perpendicular to the thickness direction of the hollow structure film 1. Therefore, multiple support portions 20 extend in the first direction d1 perpendicular to the thickness direction of the hollow structure film 1. In the example shown in FIG. 2, the first base 11 does not have any connection portions 24 extending in any direction other than the first direction d1. Therefore, the hollow structure film 1 does not have any support portions 20 extending in any direction other than the first direction d1.

[0059] In the example shown in Fig. 2, the connection portions 24 of the first base 11 are arranged at equal intervals in the thickness direction of the hollow structure film 1 and in a second direction d2 perpendicular to the first direction d1. That is, in the example shown in Fig. 2, the intervals w1 between the connection portions 24 in the second direction d2 are the same. Although not shown, the intervals w1 between the connection portions 24 in the second direction d2 do not have to be the same.

[0060] As an example, the connection portion 24 of the second base 12 extends in the same direction as the extension direction of the connection portion 24 of the first base 11, i.e., in the first direction d1. In this embodiment, the shape of the second base 12 and the portion located closer to the second base 12 than the central portion 30 of the multiple support portions 20 is the same as the shape of the first base 11 and the portion located closer to the first base 11 than the central portion 30 of the multiple support portions 20. The connection portion 24 of the second base 12 may extend in a direction different from the extension direction of the connection portion 24 of the first base 11. The shape of the second base 12 and the portion located closer to the second base 12 than the central portion 30 of the multiple support portions 20 may be different from the shape of the first base 11 and the portion located closer to the first base 11 than the central portion 30 of the multiple support portions 20. Unless otherwise specified, the present specification will describe a hollow structure film 1 in which the connection portion 24 of the second base 12 extends in the same direction as the extension direction of the connection portion 24 of the first base 11. Unless otherwise specified, the present specification will describe a hollow structure film 1 in which the shape of the second base 12 and the portion located closer to the second base 12 than the central portion 30 of the plurality of support portions 20 is the same as the shape of the first base 11 and the portion located closer to the first base 11 than the central portion 30 of the plurality of support portions 20.

[0061] The hollow structure film 1 further includes a sheet-like central portion 30 that overlaps the first base 11 and the second base 12 and is located between the first opposing surface 11a and the second opposing surface 12a. The central portion 30 has a first central surface 30a that faces the first base 11 and a second central surface 30b that faces the second base 12. The central portion 30 constitutes a part of the plurality of support portions 20 that extend from one of the pair of bases 10 to the other. Even when the hollow structure film 1 includes the central portion 30 as shown in FIG. 1 , if a straight line L1 extending from the first opposing surface 11a to the second opposing surface 12a without protruding from the hollow structure film 1 can be drawn on a cross section of the hollow structure film 1 cut along a plane parallel to the thickness direction, the support portion 20 through which the straight line L1 passes is considered to be a continuous support portion 23.

[0062] 1 , the first portion 21 of the support column 20 extends from the first opposing surface 11a of the first base 11 to the first central surface 30a of the central portion 30. That is, the first portion 21 of the support column 20 is connected to the central portion 30. Furthermore, the second portion 22 of the support column 20 extends from the second opposing surface 12a of the second base 12 to the second central surface 30b of the central portion 30. That is, the second portion 22 of the support column 20 is connected to the central portion 30.

[0063] The hollow structure film 1 has the central portion 30, which can increase the strength of the hollow structure film 1. In particular, the first portion 21 of the support portion 20 is connected to the central portion 30, and the second portion 22 of the support portion 20 is connected to the central portion 30, which can increase the strength of the hollow structure film 1.

[0064] In this embodiment, the hollow structure film 1 contains polyolefin. In particular, the main body 1c of the hollow structure film 1 contains polyolefin. In this embodiment, the pair of bases 10, the multiple struts 20, and the central portion 30 each contain a resin. The resin contained in the pair of bases 10, the multiple struts 20, and the central portion 30 may be polyolefin. In this case, any of polyethylene, polypropylene, and polymethylpentene may be used as the polyolefin. The pair of bases 10, the multiple struts 20, and the central portion 30 may each contain polyethylene. Furthermore, these resins may have a partially modified structure. The hollow structure film 1 may contain multiple types of resins. The pair of bases 10, the multiple struts 20, and the central portion 30 may each contain multiple resins with different molecular weights or branched structures within the polymer. A specific example of a partially modified polymer is a polymer obtained by copolymerizing ethylene and acrylic acid (ethylene-acrylic acid copolymer). An example of a film containing multiple resins with different molecular weights is one containing both common high-density polyethylene (HDPE) and low-density polyethylene (LDPE). The material of the main body 1c of the hollow structure film 1 may be a material that can be molded using a mold 90 described below at a heating temperature of less than 330°C. This allows the material to be heated using a common heating device while being molded using the mold 90, thereby producing a single-sided shaped body 80 described below, and then producing the main body 1c from the single-sided shaped body 80.

[0065] A more specific description will be given of the hollow structure film 1 containing multiple types of resin. ３ a first resin material having a greater density than 925 kg / m ３ and a second resin material having a density of 940 kg / m ３ An example of a first resin material having a higher density is high density polyethylene (HDPE). ３An example of the second resin material having the following density is low-density polyethylene (LDPE). The density of the resin is measured in accordance with the items described in "3.5.2 Density" of JIS K6922-1:2018. At least one of the first base portion 11, the second base portion 12, and the support portion 20 may contain the first resin material and the second resin material. At least one of the first base portion 11, the second base portion 12, and the support portion 20 may be formed from a mixture of the first resin material and the second resin material.

[0066] Examples of polyethylene products include Prime Polymer Co., Ltd.'s Hi-Zex (registered trademark) (HDPE), Neozex (registered trademark) (C4-LLDPE), and Ult-Zex (registered trademark) (C6-LLDPE), Dow Chemical Co.'s DOWLEX (registered trademark): 2045.11G (C8 copolymer) (LLDPE), Japan Polyethylene Co., Ltd.'s Novatec (registered trademark) HD ​​(HDPE), Novatec (registered trademark) LL (LLDPE), and Asahi Kasei Corporation's Suntec (registered trademark) HD ​​(HDPE), and Suntec (registered trademark) LD (LDPE). Examples of polypropylene products include Prime Polypro (registered trademark) manufactured by Prime Polymer Co., Ltd. and Japan Polypropylene Corporation's Novatec (registered trademark) PP. Examples of polymethylpentene products include Mitsui Chemicals, Inc.'s TPX (registered trademark).

[0067] In the hollow structure film 1, the pair of bases 10 and the portions of the multiple support columns 20 that are not constituted by the central portion 30 are collectively referred to as the shaped body corresponding portion 13. The resin contained in the shaped body corresponding portion 13 may be different from the resin contained in the central portion 30. In this case, the shaped body corresponding portion 13 may contain a first resin material, and the central portion 30 may contain a second resin material. The shaped body corresponding portion 13 may contain a second resin material, and the central portion 30 may contain the first resin material. In this case, the boundary between the portion of the multiple support columns 20 that is constituted by the central portion 30 and the portion that is not constituted by the central portion 30 is considered to be located at the positions of an imaginary plane F1 extending from the first central plane 30a of the central portion 30 and an imaginary plane F2 extending from the second central plane 30b of the central portion 30.

[0068] The resin contained in the central portion 30 may have a lower melting point than the resin contained in the shaped object corresponding portion 13. In this case, the resin contained in the central portion 30 may be linear low-density polyethylene (LLDPE). The resin contained in the shaped object corresponding portion 13 may be high-density polyethylene (HDPE).

[0069] The hollow structure film 1 of the present embodiment has a hollow structure. This allows the dielectric constant of the hollow structure film 1 to be low without using a specific material with a low dielectric constant. Therefore, even when polyolefin is used as the material for each of the pair of bases 10, the multiple support columns 20, and the central portion 30, the dielectric constant of the hollow structure film 1 can be low. Using polyolefin as the resin contained in a film such as the hollow structure film 1, which can be used as a material for a circuit board (described later), can achieve the following advantages compared to using polyimide as the resin contained in the film. Polyolefin is generally less expensive than polyimide, thereby reducing the cost of manufacturing the film and the circuit board. Additionally, as described later, when a metal layer 40 is bonded to the surface of the resin portion of the film, the metal layer 40 can be more firmly adhered to the resin surface. Furthermore, generally, materials with a low dielectric constant, such as polyimide, often have a high melting point and are difficult to process. In contrast, the hollow structure film 1 of the present embodiment does not require the material to be a specific material with a low dielectric constant. This allows the selection of a material that can be processed by a simple method.

[0070] In the example shown in FIG. 1 , the hollow structure film 1 contains particles 50 that can reduce the amount of shrinkage of the hollow structure film 1 after processing by heating. The particles 50 may increase the heat resistance of the hollow structure film 1. In this embodiment, the particles 50 are dispersed in the resin that is the material of the hollow structure film 1. The particles 50 are contained in the resin-containing portion of the hollow structure film 1. This reduces the amount of shrinkage of the resin-containing portion of the hollow structure film 1 after processing by heating. Furthermore, the heat resistance of the resin-containing portion of the hollow structure film 1 can be increased. At least one of the shaped body corresponding portion 13 and the central portion 30 may contain particles 50. Both the shaped body corresponding portion 13 and the central portion 30 may contain particles 50. At least one of the pair of bases 10, the plurality of support portions 20, and the central portion 30 may contain particles 50. In the example shown in FIG. 1 , each of the pair of bases 10, the plurality of support portions 20, and the central portion 30 contains particles 50. In FIG. 1 and FIGS. 4 to 8C and 10 described below, to avoid cluttering the drawings, only some of the particles 50 contained in the hollow structure film 1 are shown, and the remaining particles 50 are omitted. By including particles 50 in each of the pair of bases 10, the plurality of support columns 20, and the central section 30, the amount of shrinkage of each of the pair of bases 10, the plurality of support columns 20, and the central section 30 after heat processing can be reduced. Furthermore, the heat resistance of each of the pair of bases 10, the plurality of support columns 20, and the central section 30 can be increased. In particular, when the hollow structure film 1 is used in a circuit board 100, the hollow structure film 1 may be required to have heat resistance sufficient to withstand the temperatures encountered during soldering. The hollow structure film 1 containing particles 50 can increase the heat resistance of the hollow structure film 1 to a level that allows it to more stably withstand the temperatures encountered during soldering.

[0071] As an example, the particles 50 are glass particles 51. That is, the hollow structure film 1 may contain glass particles 51. In the example shown in FIG. 1 , the glass particles 51 have a substantially spherical shape. Although not shown, the particles 50 may be particles other than the glass particles 51 that can reduce the amount of shrinkage of the hollow structure film 1 after heat processing. The material of the particles 50 may be, for example, a resin other than polyolefin that has greater heat resistance than polyolefin. The particles 50 may also be an inorganic material other than glass. The particles 50 may be, for example, a flake-shaped filler. A "flake-shaped filler" is, for example, a filler having a flat shape. Although not shown, the hollow structure film 1 may contain fibers, instead of or in addition to the particles 50, that can reduce the amount of shrinkage of the hollow structure film 1 after heat processing. In this case, the material of the particles 50 described above can be used as the material of the fibers. The fibers are included in, for example, the portion of the hollow structure film 1 described above as a portion in which the particles 50 can be included.

[0072] The particles 50 may have hollow portions 52. In the example shown in FIG. 1 , the glass particles 51 have hollow portions 52. When the particles 50 have hollow portions 52, and particularly when the glass particles 51 have hollow portions 52, the amount of shrinkage of the hollow-structure film 1 after processing by heating can be reduced. In addition, the hollow portions 52 can increase the heat resistance of the hollow-structure film 1. Furthermore, the hollow portions 52 can reduce the dielectric constant of the hollow-structure film 1. As an additional effect, the hollow-structure film 1 can also be made lighter.

[0073] The ratio of the mass of the particles 50 contained in the shaped body-corresponding portion 13 to the total mass of the shaped body-corresponding portion 13 is preferably 60% by mass or less. The ratio of the mass of the particles 50 contained in the shaped body-corresponding portion 13 to the total mass of the shaped body-corresponding portion 13 may be 1% by mass or more. When the ratio is 1% by mass or more, the dimensional change of the shaped body-corresponding portion 13 can be made less likely when the shaped body-corresponding portion 13 is heated, for example, when the shaped body-corresponding portion 13 is processed in the manufacturing method of the hollow structure film 1 described below. Furthermore, when the hollow structure film 1 including the shaped body-corresponding portion 13 is used as a product, even when the ambient temperature changes, the dimensional change of the shaped body-corresponding portion 13 can be made less likely. Although not shown, the shaped body-corresponding portion 13 does not have to contain particles 50. The ratio of the mass of the particles 50 contained in the central portion 30 to the total mass of the central portion 30 is preferably 60% by mass or less. The ratio of the mass of the particles 50 contained in the central portion 30 to the total mass of the central portion 30 may be 1 mass % or more. When the ratio is 1 mass % or more, the central portion 30 is less likely to change in dimension when heated in the manufacturing method of the hollow structure film 1 described below. Although not shown, the central portion 30 does not have to contain the particles 50.

[0074] The hollow structure film 1 of the present embodiment may contain a compound having a double bond that is reactive to radiation or a thermal radical initiator.

[0075] In particular, the hollow structure film 1 of this embodiment may contain a compound having a double bond active to radiation. The compound having a double bond active to radiation is, for example, an electron beam crosslinking agent. In this case, the compound is dispersed in the resin that is the material of the hollow structure film 1. The compound is included in the resin-containing portion of the hollow structure film 1. At least one of the shaped body corresponding portion 13 and the central portion 30 may contain the compound. Both the shaped body corresponding portion 13 and the central portion 30 may contain the compound. The hollow structure film 1 containing the compound is manufactured by a hollow structure film manufacturing method including a crosslinking step, which will be described later. Such a hollow structure film 1 can enhance the heat resistance of the hollow structure film 1. In particular, when the hollow structure film 1 is used in a circuit board 100, the hollow structure film 1 may be required to have heat resistance sufficient to withstand the temperatures during soldering. The hollow structure film 1 described above can enhance the heat resistance of the hollow structure film 1 to a level sufficient to withstand the temperatures during soldering.

[0076] The hollow structure film 1 may contain an ionizing radiation-curable compound as a compound having a radiation-reactive double bond. The ionizing radiation-curable compound refers to a compound that crosslinks and cures upon exposure to ionizing radiation and has an ionizing radiation-curable functional group. The ionizing radiation-curable functional group is a group that crosslinks upon exposure to ionizing radiation, such as a functional group (ethylenically unsaturated group) having an ethylenic double bond, such as a (meth)acryloyl group, a vinyl group, or an allyl group. The ionizing radiation refers to electromagnetic waves or charged particle beams that have an energy quantum capable of polymerizing or crosslinking molecules. Examples of ionizing radiation include electron beams (EB) and ultraviolet rays (UV), as well as electromagnetic waves such as X-rays and gamma rays; and charged particle beams such as alpha rays and ion beams. The ionizing radiation-curable compound that crosslinks and cures upon exposure to electron beams corresponds to the electron beam crosslinking agent described above.

[0077] Examples of the ionizing radiation-curable compound include polymerizable monomers and polymerizable oligomers that have conventionally been used as ionizing radiation-curable compounds. As the polymerizable monomer, a (meth)acrylate monomer having a (meth)acryloyl group in the molecule is preferred, and a polyfunctional (meth)acrylate monomer having two or more (meth)acryloyl groups in the molecule is more preferred. The number of (meth)acryloyl groups in the polyfunctional (meth)acrylate monomer is 2 or more, preferably 8 or less, more preferably 6 or less.

[0078] Examples of the polymerizable monomer include bifunctional (meth)acrylates such as ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, bisphenol A tetraethoxy di(meth)acrylate, and bisphenol A tetrapropoxy di(meth)acrylate; trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate; Examples thereof include tri- or higher functional (meth)acrylates such as pentaerythritol tetra(meth)acrylate, dipentaerythritol tri(meth)acrylate, dipentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, and dipentaerythritol hexa(meth)acrylate; and ethylene oxide-modified, propylene oxide-modified, caprolactone-modified, isocyanuric acid-modified, or propionic acid-modified products of these (meth)acrylates.

[0079] Examples of the polymerizable oligomer include (meth)acrylate oligomers having two or more (meth)acryloyl groups in the molecule. Examples of the (meth)acrylate oligomer include urethane (meth)acrylate, epoxy (meth)acrylate, polyester (meth)acrylate, polyether (meth)acrylate, polycarbonate (meth)acrylate, polycaprolactone urethane (meth)acrylate, polycaprolactone diol urethane (meth)acrylate, and acrylic (meth)acrylate. The number of (meth)acryloyl groups in the polymerizable oligomer is two or more, preferably eight or less, more preferably six or less.

[0080] Other examples of the polymerizable oligomer include highly hydrophobic polybutadiene (meth)acrylate oligomers having (meth)acryloyl groups in the side chains of polybutadiene oligomers, and silicone (meth)acrylate oligomers having polysiloxane bonds in the main chains.

[0081] The weight average molecular weight of the polymerizable oligomer may be 500 or more, 1,000 or more, 2,000 or more, or 10,000 or less, 8,000 or less, or 6,000 or less. The weight average molecular weight is an average molecular weight measured by gel permeation chromatography (GPC) analysis and converted into standard polystyrene.

[0082] As the ionizing radiation-curable compound, a monofunctional (meth)acrylate may be appropriately used in combination with a polyfunctional (meth)acrylate for the purpose of reducing the viscosity of the curable composition during coating, etc. Examples of the monofunctional (meth)acrylate include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, and isobornyl (meth)acrylate.

[0083] As described above, the ionizing radiation-curable compound may have an allyl group. The ionizing radiation-curable compound having an allyl group may be triallyl cyanurate, triallyl citrate, or triallyl 1,3,5-benzenetricarboxylate.

[0084] The hollow structure film 1 may contain a thermal radical initiator. By including a thermal radical initiator in the hollow structure film 1, a crosslinking reaction occurs due to the heat generated when the shaped body corresponding portion 13 is heated, for example, when the shaped body corresponding portion 13 is processed in a method for producing the hollow structure film 1, as described below. This crosslinking reaction can increase the heat resistance of the hollow structure film 1. In particular, when the hollow structure film 1 is used in a circuit board 100, the hollow structure film 1 may be required to have heat resistance sufficient to withstand the temperatures encountered during soldering. By including a thermal radical initiator in the hollow structure film 1, the heat resistance of the hollow structure film 1 can be increased to a level sufficient to withstand the temperatures encountered during soldering. The thermal radical initiator contained in the hollow structure film 1 is not particularly limited, but azo compounds such as 2,2-azobis(isobutyronitrile) and 2,2'-azobis(2-methylpropionate)dimethyl, as well as peroxide compounds such as di-tert-butyl peroxide, can be suitably used.

[0085] A thermal radical initiator may be used as a thermal radical polymerization initiator. In other words, the hollow structure film 1 of the present embodiment may contain, in addition to a compound having an active double bond, a compound generally known as a thermal radical polymerization initiator (a cross-linking agent that forms cross-links between molecules of polyethylene, etc., through chemical bonds when heated). When the hollow structure film 1 contains a thermal radical polymerization initiator, the following effects are obtained. As described below, in the process of molding the material for the shaped body corresponding portion 13 in the manufacturing method of the hollow structure film 1, the resin in the mixture that is the material for the shaped body corresponding portion 13 is melted while molding the mixture. The inclusion of a thermal radical polymerization initiator allows bonds to be formed between the resin molecules due to the heat generated when melting the resin. This more reliably ensures the heat resistance required when the hollow structure film 1 is used in a circuit board 100.

[0086] When the hollow structure film 1 of the present embodiment contains the thermal radical polymerization initiator described above, it may further contain a silane coupling agent in addition to the thermal radical polymerization initiator. In this case, the following effects are obtained. As described below, in the process of molding the material for the shaped body-corresponding portion 13 in the manufacturing method of the hollow structure film 1, the resin in the mixture that is the material for the shaped body-corresponding portion 13 is melted and molded. At this time, since the thermal radical polymerization initiator and the silane coupling agent are contained, a crosslinking reaction occurs between the resin and the silane coupling agent due to the heat generated when melting the resin. Furthermore, in a process subsequent to the process of molding the material for the shaped body-corresponding portion 13, the hollow structure film 1 may be stored in a high-temperature, high-humidity environment. In this case, the storage of the hollow structure film 1 in a high-temperature, high-humidity environment causes a reaction between the silane coupling agents. These reactions more reliably ensure the heat resistance required when the hollow structure film 1 is used in the circuit board 100.

[0087] Specific examples of the thermal radical polymerization initiator include di-t-butyl peroxide, dicumyl peroxide, and 2,2'-azobis(2,4-dimethylvaleronitrile).

[0088] The width of the connection portion 24, which is the portion connected to the support portion 20 of the base portion 10, in the second direction d2 is defined as width w2. In this case, the interval w1 between the connection portions 24 in the second direction d2 is preferably 0.5 to 20 times the width w2. By making the interval w1 0.5 times or more the width w2, the size of the hollow portion B can be ensured to be particularly large, and the dielectric constant of the hollow structure film 1 can be particularly low. By making the interval w1 20 times or less the width w2, the strength of the hollow structure film 1 can be particularly high.

[0089] In a hollow structure film 1 having a central portion 30 as shown in FIG. 1 , the distance between the base 10 and the central portion 30 is defined as distance w3. When the distance between the base 10 and the central portion 30 is not constant, the distance between the connection portion 24 of the base 10 and the central portion 30 is defined as distance w3. In this case, it is preferable that the distance w3 is 1 to 10 times the width w2. By making the distance w3 1 or more times the width w2, the size of the hollow portion B can be ensured to be particularly large, and the dielectric constant of the hollow structure film 1 can be particularly low. By making the distance w3 10 or less times the width w2, the strength of the hollow structure film 1 can be particularly increased.

[0090] The cross-sectional view of the hollow structure film 1 shown in FIG. 1 corresponds to a diagram showing a cross-section of the hollow structure film 1, in which multiple support columns 20 extend in the first direction d1, cut along a plane passing through the multiple support columns 20 and perpendicular to the first direction d1. In the cross-section shown in FIG. 1, the angle θ1 formed between the first opposing surface 11a and the portion of the surface 20b of the support column 20 that contacts the hollow portion B and connects to the first base 11 is 90° or more and 150° or less. In addition, in the cross-section shown in FIG. 1, the angle θ2 formed between the second opposing surface 12a and the portion of the surface 20b of the support column 20 that contacts the hollow portion B and connects to the second base 12 is 90° or more and 150° or less. By setting the angle θ1 and the angle θ2 to 90° or more and 150° or less, the size of the hollow portion B can be ensured, the dielectric constant of the hollow structure film 1 can be reduced, and the strength of the hollow structure film 1 can be ensured.

[0091] In the example shown in FIG. 1 , the surface 20b of the support portion 20 that contacts the hollow portion B is a flat surface. Therefore, in the cross-sectional view of the hollow structure film 1 shown in FIG. 1 , the surface 20b appears as a straight line. Although not shown, the surface 20b does not have to be a flat surface. The surface 20b may also be a curved surface. If the surface 20b is not a flat surface, the surface 20b may appear as a curved surface or a broken line in the cross-sectional view of the hollow structure film 1. In this case, the angle formed by the tangent line of the surface 20b, which appears in the cross-sectional view of the hollow structure film 1, at the portion where it connects to the first base 11 and the first opposing surface 11a is considered to be angle θ1. Furthermore, the angle formed by the tangent line of the surface 20b, which appears in the cross-sectional view of the hollow structure film 1, at the portion where it connects to the second base 12 and the second opposing surface 12a is considered to be angle θ2.

[0092] As an example, the porosity of the hollow structure film 1 is 10% or more, and more preferably 20% or more. A porosity of 20% or more in the hollow structure film 1 ensures a particularly large size of the hollow portion B, thereby enabling the hollow structure film 1 to have a particularly low dielectric constant. The porosity of the hollow structure film 1 is preferably 70% or less. A porosity of 70% or less in the hollow structure film 1 prevents a decrease in film strength due to a decrease in the amount of resin contained in the hollow structure film 1. The porosity of the hollow structure film 1 is measured by the following method. A cross section of the hollow structure film 1, as shown in FIG. 1 , is observed, cut along a plane passing through the multiple support columns 20 and perpendicular to the first direction d1. On the cross section, a straight line L2 is drawn that passes through the center in the second direction d2 of one of the multiple connection portions 24 of one of the pair of bases 10 (first base 11) and is parallel to the thickness direction of the hollow structure film 1. Furthermore, one of the multiple connection portions 24 of one of the pair of bases 10 (first base 11) is identified, and the connection portion 24 adjacent in the second direction d2 to the connection portion 24 along which the line L2 is drawn is identified. A line L3 is drawn that passes through the center of the connection portion 24 in the second direction d2 and is parallel to the thickness direction of the hollow structure film 1. Next, the ratio of the area of ​​the hollow portion B between lines L2 and L3 to the area of ​​the entire hollow structure film 1, including the hollow portion B, is calculated. This ratio is calculated at 10 different points on the cross section. The porosity of the hollow structure film 1 is obtained by averaging the ratios calculated at the 10 different points. More specifically, a cross section of the hollow structure film 1 cut along a plane passing through the multiple support columns 20 and perpendicular to the first direction d1 is observed using a scanning electron microscope (SEM) or an optical microscope, and an image of the cross section is obtained. The magnification of the image obtained can be 100x or more. 3 is a diagram showing an example of an image of a cross section of the hollow structure film 1 obtained by a scanning electron microscope (SEM). As shown in FIG. 3, by drawing lines L2 and L3 on the obtained image, the porosity of the hollow structure film 1 can be obtained from the image.

[0093] The hollow structure film 1 may further include a metal layer 40. In this case, the circuit board 100 described later can be manufactured by forming wiring 41 described later from at least a portion of the metal layer 40. The hollow structure film 1 may further include a metal adjacent layer 60. The metal adjacent layer 60 can more firmly bond the metal layer 40 to the base 10. FIG. 4 is a cross-sectional view showing an example of a hollow structure film 1 including the metal layer 40 and the metal adjacent layer 60. The hollow structure film 1 shown in FIG. 4 corresponds to the hollow structure film 1 shown in FIG. 1 in which the metal adjacent layer 60 and the metal layer 40 are laminated in this order on the first surface 1a. FIG. 5 is a cross-sectional view showing an example of a hollow structure film 1 including the metal layer 40 and the metal adjacent layer 60, different from that shown in FIG. 4. The hollow structure film 1 shown in FIG. 5 corresponds to the hollow structure film 1 shown in FIG. 1 in which the metal adjacent layer 60 and the metal layer 40 are laminated in this order on the first surface 1a and the second surface 1b.

[0094] The hollow structure film 1 shown in Figures 4 and 5 has a first surface 1a and a second surface 1b located on the opposite side to the first surface 1a. The metal layer 40 constitutes at least a portion of at least one of the first surface 1a and the second surface 1b. In the example shown in Figure 4, the metal layer 40 constitutes the first surface 1a. In this case, the metal layer 40 may constitute the entire first surface 1a or may constitute a portion of the first surface 1a. In the example shown in Figure 5, the metal layer 40 constitutes both the first surface 1a and the second surface 1b. In this case, the metal layer 40 may constitute the entire first surface 1a or may constitute a portion of the first surface 1a. Furthermore, the metal layer 40 may constitute the entire second surface 1b or may constitute a portion of the second surface 1b.

[0095] The material of the metal layer 40 is not particularly limited as long as the wiring 41 of the circuit board 100, which will be described later, can be formed from at least a portion of the metal layer 40. The material of the metal layer 40 is, for example, copper. The metal layer 40 can be formed by bonding a metal foil to the base 10. By bonding a copper foil to the base 10, the metal layer 40 made of copper can be formed. The thickness of the metal layer 40 is, for example, 0.1 μm or more and 100 μm or less. The thickness of the metal layer 40 may be 2 μm or more and 20 μm or less.

[0096] The metal layer 40 may be formed by a method other than bonding a metal foil such as a copper foil. The metal layer 40 may be formed by a process such as plating or sputtering. When forming the metal layer 40 by plating, a commonly known seed layer may be formed. When forming the metal layer 40 by a process such as plating or sputtering, a plasma treatment known as glow treatment or reverse sputtering may be performed on the surface of the base 10 on which the metal layer 40 is to be formed before forming the metal layer 40. Such a treatment can further increase the adhesion between the base 10 and the metal layer 40.

[0097] The metal adjacent layer 60 is a layer that bonds the metal layer 40 to the base 10. The metal adjacent layer 60 bonds the metal layer 40 to at least one of the first base 11 and the second base 12. The material of the metal adjacent layer 60 is different from the material of the base 10. The material of the metal adjacent layer 60 is different from the materials of the first base 11 and the second base 12. The metal adjacent layer 60 is a resin layer that has good adhesion to metal and can be heat-sealed with polyolefin. Bonding the metal layer 40 to the base 10 with the metal adjacent layer 60 can more firmly bond the metal layer 40 to the base 10. The metal adjacent layer 60 may be an ionomer layer, i.e., a layer of ionomer resin. When the metal adjacent layer 60 is an ionomer layer, the material of the metal adjacent layer 60 is, for example, carboxylic acid copolymerized polyethylene containing metal ions. The metal-adjacent layer 60 may be an ethylene (meth)acrylic acid copolymer layer. That is, the hollow structure film 1 may further include an ionomer layer or an ethylene (meth)acrylic acid copolymer layer that bonds the metal layer 40 to the base 10. The hollow structure film 1 may further include an ionomer layer or an ethylene (meth)acrylic acid copolymer layer that bonds the metal layer 40 to at least one of the first base 11 and the second base 12. This allows the metal layer 40 to be more firmly bonded to the base 10. The thickness of the metal-adjacent layer 60 is, for example, 20 μm or less.

[0098] A specific example of an ionomer is Himilan (registered trademark) manufactured by Mitsui-Dow Polychemical Co., Ltd. A specific example of an ethylene acrylic acid copolymer is Nucrel (registered trademark) manufactured by Mitsui-Dow Polychemical Co., Ltd. The material of the metal adjacent layer 60 is not limited to the resins described above. Resins having the same functions as the resins described above can be suitably used as the material of the metal adjacent layer 60.

[0099] The metal adjacent layer 60 is not limited to the above example. Any resin that exhibits the function of adhering to metal can be suitably used as the metal adjacent layer 60.

[0100] The material of the metal adjacent layer 60 may be an adhesive. The metal adjacent layer 60 may be a layer formed by applying a varnish formed by dissolving a resin and then drying the varnish. In the metal adjacent layer 60 of the above embodiment, an adhesive may be used as the resin used to form the varnish.

[0101] Metallic adjacent layer 60 may be a bonding sheet available in sheet form, such as a bonding sheet commercially available in sheet form.

[0102] Because the hollow structure film 1 of this embodiment has a hollow structure, it is possible to increase the thickness while reducing the dielectric constant. Therefore, the thickness of the hollow structure film 1 of this embodiment can vary. As an example, the thickness of the hollow structure film 1 is 50 μm or more and 1000 μm or less. In this way, the hollow structure film 1 of this embodiment can widen the range of values ​​that can be used as the thickness of the hollow structure film 1.

[0103] The storage modulus of the hollow structure film 1 of this embodiment is, for example, 1.0×10 5 The hollow structure film 1 contains an electron beam crosslinking agent, and as will be described later, the storage modulus of the hollow structure film 1 is increased to 1.0 × 10 Pa or more by irradiating the electron beam crosslinking agent with an electron beam in the manufacturing method of the hollow structure film 1. 5Pa or more. When the storage modulus is equal to or less than the above lower limit, the hollow structure film 1 is less likely to deform during short-term high-temperature processing. Specifically, the hollow structure film 1 is sufficiently less likely to deform when soldered in a solder reflow process. The storage modulus of the hollow structure film 1 is measured using a dynamic viscoelasticity (DMA) measuring device. In measuring the storage modulus of the hollow structure film 1, the measurement mode of the dynamic viscoelasticity measuring device is set to tensile mode, and the storage modulus is measured when the temperature of the hollow structure film 1 is 280°C. The method for measuring the storage modulus of the hollow structure film 1 can be the method for measuring the storage modulus described in the Examples below.

[0104] In the hollow structure film 1 having the metal layer 40 of this embodiment, at least one of the following conditions is satisfied: the transmission loss value of an electric signal with a frequency of 10 GHz applied to the linear wiring 43 formed from the metal layer 40 is greater than −0.30 dB / 3.5 cm; the transmission loss value of an electric signal with a frequency of 20 GHz applied to the linear wiring 43 is greater than −0.60 dB / 3.5 cm; the transmission loss value of an electric signal with a frequency of 30 GHz applied to the linear wiring 43 is greater than −0.90 dB / 3.5 cm; the transmission loss value of an electric signal with a frequency of 40 GHz applied to the linear wiring 43 is greater than −1.30 dB / 3.5 cm; the transmission loss value of an electric signal with a frequency of 50 GHz applied to the linear wiring 43 is greater than −1.80 dB / 3.5 cm; or the transmission loss value of an electric signal with a frequency of 60 GHz applied to the linear wiring 43 is greater than −3.00 dB / 3.5 cm. The transmission loss value of the electrical signal has a negative value. The closer the transmission loss value of the electrical signal is to zero, the smaller the attenuation of the electrical signal applied to the linear wiring 43. Therefore, for example, a transmission loss value greater than -0.30 dB / 3.5 cm (closer to zero) means that the attenuation of the applied electrical signal is smaller than when the transmission loss value is -0.30 dB / 3.5 cm. A "large transmission loss value" means that a transmission loss value with a negative value is close to zero. A "small transmission loss value" means that a transmission loss value with a negative value is far from zero. When simply stating "small transmission loss," it means that the absolute value of a transmission loss value with a negative value is small. When simply stating "large transmission loss," it means that the absolute value of a transmission loss value with a negative value is large.

[0105] In the hollow structure film 1 having the metal layer 40, the transmission loss value of an electric signal having a frequency of 10 GHz applied to the linear wiring 43 formed from the metal layer 40 may be greater than −0.30 dB / 3.5 cm, the transmission loss value of an electric signal having a frequency of 20 GHz applied to the linear wiring 43 may be greater than −0.60 dB / 3.5 cm, the transmission loss value of an electric signal having a frequency of 30 GHz applied to the linear wiring 43 may be greater than −0.90 dB / 3.5 cm, the transmission loss value of an electric signal having a frequency of 40 GHz applied to the linear wiring 43 may be greater than −1.30 dB / 3.5 cm, the transmission loss value of an electric signal having a frequency of 50 GHz applied to the linear wiring 43 may be greater than −1.80 dB / 3.5 cm, and the transmission loss value of an electric signal having a frequency of 60 GHz applied to the linear wiring 43 may be greater than −3.00 dB / 3.5 cm. According to such a hollow structure film 1, even when electrical signals of various frequencies are applied to the wiring formed from the metal layer 40, the transmission loss value can be made large (close to zero).

[0106] The transmission loss of an electrical signal applied to a linear wiring 43 in a hollow structure film 1 having a metal layer 40 is measured by the following method. First, as shown in FIG. 6A, a linear wiring 43 is formed from the metal layer 40 of the hollow structure film 1. FIG. 6A is a perspective view showing a hollow structure film 1 having a linear wiring 43 used to measure the transmission loss of an electrical signal. In FIG. 6A and FIG. 6C described later, the details of the structure of the main body portion 1c of the hollow structure film 1 are omitted, and only the general shape of the main body portion 1c is shown. In FIG. 6A and FIG. 6C described later, the metal adjacent layer 60 is omitted.

[0107] The hollow structure film 1 shown in FIG. 6A has metal layers 40 on the first surface 1a and the second surface 1b. In the hollow structure film 1 shown in FIG. 6A, linear wiring 43 is formed from the metal layer 40 on the first surface 1a. The hollow structure film 1 shown in FIG. 6A is produced from a hollow structure film 1 having a metal layer 40 constituting at least a portion of the first surface 1a and a metal layer 40 constituting at least a portion of the second surface 1b, as shown in FIG. 5. The hollow structure film 1 shown in FIG. 6A can be produced by forming linear wiring 43 from the metal layer 40 constituting at least a portion of the first surface 1a of the hollow structure film 1, as shown in FIG. 5. The method for forming the linear wiring 43 from the metal layer 40 can be the same as the method for forming a wiring pattern from the metal layer 40 in the manufacturing method of the circuit board 100 described below.

[0108] The length w5 of the linear wiring 43 (the dimension of the linear wiring 43 in the direction in which the linear wiring 43 extends) is 3.5 cm or more. The width w6 of the linear wiring 43 (the dimension of the linear wiring 43 in the direction perpendicular to the direction in which the linear wiring 43 extends and parallel to the first surface 1a) is 0.75 mm. The thickness w11 of the insulating portion of the film is 0.25 mm. The thickness w11 of the insulating portion of the film corresponds to the distance between the metal layer 40 on the first surface 1a side and the metal layer 40 on the second surface 1b side. In the hollow structure film 1 of this embodiment, the thickness w11 of the insulating portion corresponds to the thickness of the main body 1c. The film structure shown in FIG. 6A and described above is generally called a microstrip line. The width w6 of the linear wiring 43 is adjusted so that the characteristic impedance of the microstrip line on that particular film is 50 Ω. The calculation formula used to adjust the characteristic impedance of the linear wiring 43 is as follows: That is, the width w6 of the linear wiring 43 is adjusted so that the value of the characteristic impedance calculated from the following formula becomes 50Ω. ｒ " denotes the dielectric constant, "Z0" denotes the characteristic impedance, "h" denotes the thickness w11, "w" denotes the width w6 of the linear wiring 43, and "t" denotes the thickness w12 of the linear wiring 43.

[0109] To measure the transmission loss of an electrical signal applied to the linear wiring 43, first, the hollow structure film 1 including the linear wiring 43 is fixed to a jig 93 as shown in FIG. 6B . A probe 94 connected to a network analyzer via a coaxial cable is attached to the jig 93. By fixing the hollow structure film 1 to the jig 93, the probe 94 comes into contact with the linear wiring 43 as shown in FIG. 6B . Next, an AC electrical signal is applied from the network analyzer to both ends of the linear wiring 43 via the probe 94 attached to the jig 93, and the transmission loss of the electrical signal is measured. The measurement of the transmission loss of the electrical signal is performed under the following conditions. The electrical signal is applied to a 5.0 cm section of the linear wiring 43. During the measurement, a de-embedding process is performed to remove the influence of the jig 93 from the measurement results. In the de-embedding process, the transmission loss of the electrical signal is first measured over a 1.5 cm section of a sample having the same wiring configuration as the linear wiring 43. Next, the de-embedding process is performed based on the measurement results of the transmission loss of the sample. This allows the calculation of a value equivalent to the transmission loss measured by applying an electrical signal to a section of the linear wiring 43 that is 3.5 cm long, from the transmission loss measured by applying an electrical signal to a section of the linear wiring 43 that is 5.0 cm long, with the effects of the transmission loss at both ends of the linear wiring 43 and at the jig 93 removed.

[0110] <Circuit Board> Next, the circuit board 100 of this embodiment will be described. The circuit board 100 of this embodiment includes the hollow structure film 1 of this embodiment. The circuit board 100 of this embodiment further includes a wiring pattern provided on at least one of the first surface 1a and the second surface 1b. In a hollow structure film 1 including a metal layer 40 as shown in FIGS. 4 and 5, by forming wiring 41 from at least a part of the metal layer 40, a circuit board 100 including the hollow structure film 1 and a wiring pattern of wiring 41 can be manufactured. The circuit board 100 manufactured by the above-described method can be considered to be a circuit board 100 including a hollow structure film 1 (hollow structure film 1 shown in FIG. 1) including a main body portion 1c and a wiring pattern of wiring 41.

[0111] When manufacturing a circuit board 100 from the hollow structure film 1 shown in Fig. 4, a wiring pattern of the wiring 41 can be formed from the metal layer 40 constituting the first surface 1a of the hollow structure film 1. When manufacturing a circuit board 100 from the hollow structure film 1 shown in Fig. 5, a wiring pattern of the wiring 41 may be formed from either the metal layer 40 constituting the first surface 1a or the metal layer 40 constituting the second surface 1b of the hollow structure film 1. When manufacturing a circuit board 100 from the hollow structure film 1 shown in Fig. 5, a wiring pattern of the wiring 41 may be formed from both the metal layer 40 constituting the first surface 1a and the metal layer 40 constituting the second surface 1b.

[0112] When manufacturing a circuit board 100 from the hollow structure film 1 shown in Figure 5, a wiring pattern of wiring 41 may be formed on the metal layer 40 constituting the first surface 1a of the hollow structure film 1, but a wiring pattern of wiring 41 may not be formed on the metal layer 40 constituting the second surface 1b of the hollow structure film 1. The circuit board 100 manufactured by this method can be considered to be a circuit board 100 comprising a hollow structure film 1 (hollow structure film 1 shown in Figure 1) including a main body 1c, a wiring pattern of wiring 41 provided on the first surface 1a of the hollow structure film 1, and a metal layer 40 on the second surface 1b of the hollow structure film 1 where no wiring pattern is formed. By having the circuit board 100 include the wiring pattern of wiring 41 provided on the first surface 1a and the metal layer 40 on the second surface 1b where no wiring pattern is formed, unnecessary noise is less likely to be generated when transmitting electrical signals via the wiring 41. The metal layer 40 on the second surface 1b, on which no wiring pattern is formed, is thought to reduce the generation of unnecessary noise for the following reasons. When a current flows through the wiring 41 formed on the first surface 1a, a current flows on the second surface 1b in the opposite direction to the current flowing through the wiring 41, according to Ampere's law. In particular, when high-frequency power is supplied to the wiring 41 formed on the first surface 1a to operate it, a current flows on the second surface 1b in the opposite direction to the current flowing through the wiring 41, according to Ampere's law. This current is called a feedback current. The feedback current functions as a signal ground. In particular, when an antenna loop is formed between the wiring 41 and the ground plane, the feedback current effectively functions as a signal ground by reducing the size of the antenna loop formed. This reduces the generation of unnecessary noise.

[0113] <Antenna Equipment> Next, the antenna equipment 101 of this embodiment will be described. The antenna equipment 101 includes the circuit board 100 described above and an antenna element 102 connected to the circuit board 100. The antenna equipment 101 of this embodiment can also be referred to as an antenna substrate. The terms "equipment" and "substrate" used in this specification are not limited to their strict meanings, but are interpreted to include a range in which similar functions can be expected. The antenna equipment 101 is, for example, a patch antenna. If the antenna equipment 101 is a patch antenna, the circuit board 100 functions as the dielectric substrate of the patch antenna. If the antenna equipment 101 is a patch antenna, the wiring 41 of the patch antenna may be formed to extend to a feed point to pass current, particularly high-frequency current. If the antenna equipment 101 is a patch antenna, the patch antenna may be fed by electromagnetic coupling. In this case, the wiring 41 of the patch antenna does not need to be directly connected to the feed point.

[0114] Fig. 6C is a perspective view showing an example of an antenna device 101 according to this embodiment. The antenna device 101 shown in Fig. 6C includes the circuit board 100 described above and an antenna element 102 connected to the circuit board 100. The antenna element 102 is connected to the wiring 41 forming the wiring pattern of the circuit board 100. In the example shown in Fig. 6C, the wiring 41 of the circuit board 100 and the antenna element 102 are integrated. In the example shown in Fig. 6C, the antenna device 101 includes a hollow structure film 1 (the hollow structure film 1 shown in Fig. 1) including a main body 1c, a wiring pattern of the wiring 41, and the antenna element 102. The wiring pattern of the wiring 41 and the antenna element 102 are provided on the first surface 1a of the hollow structure film 1. In the example shown in FIG. 6C , the antenna device 101 includes a hollow structure film 1, a wiring pattern of wiring 41 provided on the first surface 1a of the hollow structure film 1, and a metal layer 40 on the second surface 1b of the hollow structure film 1, where no wiring pattern is formed. By providing the metal layer 40 on the second surface 1b, the antenna device 101 reduces the generation of unwanted noise when transmitting electrical signals via the wiring 41. The metal layer 40 on the second surface 1b, where no wiring pattern is formed, reduces the generation of unwanted noise for the following reasons: When a current flows through the wiring 41 formed on the first surface 1a, a current (the aforementioned feedback current) flows on the second surface 1b in the opposite direction to the current flowing through the wiring 41 due to Ampere's law. In particular, when high-frequency power is supplied to the wiring 41 formed on the first surface 1a for operation, a feedback current is generated on the second surface 1b. The feedback current functions as a signal ground. In particular, when an antenna loop is formed between the wiring 41 and the ground plane, the feedback current can function effectively as a signal ground by reducing the size of the antenna loop that is formed, thereby making it less likely that unnecessary noise will be generated.

[0115] The antenna element 102 shown in Fig. 6C has a rectangular shape when observed from the thickness direction of the hollow structure film 1. In the example shown in Fig. 6C, the wiring 41 extends from one side of the antenna element 102 to the end side of the antenna equipment 101.

[0116] The antenna equipment 101 shown in Fig. 6C can be manufactured from the hollow structure film 1 shown in Fig. 5. Specifically, the antenna equipment 101 shown in Fig. 6C can be manufactured by forming the wiring pattern of the wiring 41 and the antenna element 102 from the metal layer 40 constituting the first surface 1a of the hollow structure film 1 shown in Fig. 5.

[0117] <Method for Manufacturing Hollow Structure Film> A method for manufacturing a hollow structure film 1 according to this embodiment will be described. Unless otherwise specified, a method for manufacturing a hollow structure film 1 according to this embodiment will be described, in which a metal layer 40 forms the first surface 1a and the second surface 1b, as shown in FIG. 5 . The method for manufacturing a hollow structure film according to this embodiment includes the steps of: using a mold 90 to prepare a pair of single-sided shaped objects 80 each having a sheet-like base 81 and a plurality of protrusions 82 formed on one surface of the base 81; and overlapping the pair of prepared single-sided shaped objects 80 so that the plurality of protrusions 82 at least partially face each other, followed by thermocompression bonding. The method for manufacturing a hollow structure film according to this embodiment further includes a crosslinking step in which a compound having a radiation-active double bond contained in the single-sided shaped object 80 is reacted with a resin. When the compound having a radiation-active double bond is an electron beam crosslinking agent, the crosslinking step involves irradiating the electron beam crosslinking agent contained in the single-sided shaped object 80 with an electron beam to react the compound with the resin. Even if the hollow structure film 1 does not contain an electron beam crosslinking agent, it may be possible to obtain preferable physical properties by irradiating it with an electron beam during the manufacturing process. For example, even if the hollow structure film 1 does not contain an electron beam crosslinking agent, it may be possible to increase the heat resistance of the hollow structure film 1 by irradiating it with an electron beam during the manufacturing process. In this case, the hollow structure film 1 does not need to contain an electron beam crosslinking agent.

[0118] In the process of producing the single-sided shaped object 80, a pair of single-sided shaped objects 80 are produced using a mold 90. At this time, a metal foil 42 is prepared as the material for the metal layer 40. Furthermore, a material for the shaped object corresponding portion 13 is prepared. Furthermore, a material for the metal adjacent layer 60 is prepared. In this embodiment, the shaped object corresponding portion 13 of the hollow structure film 1 to be produced contains a resin. In this case, for example, raw material pellets of the corresponding resin are prepared as the material for the shaped object corresponding portion 13. If the shaped object corresponding portion 13 of the hollow structure film 1 to be produced contains polyethylene, polyethylene raw material pellets are prepared as the material for the shaped object corresponding portion 13. If the shaped object corresponding portion 13 of the hollow structure film 1 to be produced contains particles 50, particles 50 are prepared as the material for the shaped object corresponding portion 13. When the shaped body corresponding portion 13 of the hollow structure film 1 to be manufactured contains a compound having a radiation-active double bond, the compound is prepared as a material for the shaped body corresponding portion 13. When the shaped body corresponding portion 13 contains multiple materials, the multiple materials are mixed to prepare a mixture. When the shaped body corresponding portion 13 of the hollow structure film 1 to be manufactured contains a resin, particles 50, and a compound having a radiation-active double bond, a mixture of the resin, particles 50, and the compound is prepared.

[0119] Next, as shown in FIG. 7A , a mold 90 is used to mold the material of the shaped body corresponding portion 13. When the shaped body corresponding portion 13 of the hollow structure film 1 to be manufactured contains a resin, particles 50, and a compound having a radiation-active double bond, a mixture of the resin, particles 50, and the compound is molded using the mold 90. The mixture is molded while the resin contained in the mixture is melted. The mold 90 has a surface 90a shaped to correspond to the shape of the single-sided shaped body 80 to be manufactured. In particular, the surface 90a of the mold 90 has a shape corresponding to the shape of the surface of the single-sided shaped body 80 to be manufactured, on which the multiple protrusions 82 are formed. By molding the material of the shaped body corresponding portion 13 using such a mold 90, a single-sided shaped body 80 having a sheet-like base 81 and multiple protrusions 82 formed on one side of the base 81 is manufactured from the material of the shaped body corresponding portion 13. In this embodiment, the material of the shaped body corresponding portion 13 and the material of the metal adjacent layer 60 are molded onto the metal foil 42 by co-extrusion using a mold 90. As a result, the metal adjacent layer 60 is produced from the material of the metal adjacent layer 60 on the metal foil 42, which is the metal layer 40, and the single-sided shaped body 80 is produced from the material of the shaped body corresponding portion 13 on the metal adjacent layer 60. In this way, a laminate 83 is produced in which the metal layer 40, the metal adjacent layer 60, and the single-sided shaped body 80 are stacked in this order. Furthermore, another single-sided shaped body 80 is produced by a method similar to the method for producing the single-sided shaped body 80 described above. In this embodiment, another laminate 83 is produced by a method similar to the method for producing the laminate 83 described above.

[0120] When manufacturing a hollow structure film 1 in which the first surface 1a and the second surface 1b are not formed by a metal layer 40 as shown in FIGS. 1 and 4, a single-sided shaped body 80 or a laminate of a metal adjacent layer 60 and a single-sided shaped body 80 may be produced by the following method. Instead of a metal foil 42, a laminate of the material of the shaped body corresponding portion 13, or the material of the shaped body corresponding portion 13 and the material of the metal adjacent layer 60, is formed on a peelable substrate. The substrate is then peeled off. In this case, for example, a polyimide film can be used as the peelable substrate. In particular, Kapton (registered trademark) manufactured by DuPont-Toray Co., Ltd. can be used as the peelable substrate. When a peelable substrate is used, the substrate may be peeled off before the step of thermocompression bonding the pair of single-sided shaped bodies 80, or after the step of thermocompression bonding the pair of single-sided shaped bodies 80. When a peelable substrate is used, the substrate may be peeled off before the crosslinking step or after the crosslinking step. Alternatively, a PET (polyethylene terephthalate) film may be used as the peelable substrate. Specific examples of peelable PET films include COSMOSHINE (registered trademark) and COSMOPEEL (registered trademark) manufactured by Toyobo Co., Ltd.

[0121] Next, a process of heat-pressing the pair of single-sided shaped bodies 80 is performed. In this process, as shown in FIG. 7B , the pair of single-sided shaped bodies 80 are overlapped so that the multiple convex portions 82 face each other at least in part. The pair of single-sided shaped bodies 80 are overlapped so that the surfaces on which the multiple convex portions 82 are formed face each other. In this embodiment, a pair of laminates 83 including the single-sided shaped bodies 80 are overlapped so that the multiple convex portions 82 of the pair of single-sided shaped bodies 80 face each other at least in part.

[0122] The hollow structure film 1 shown in FIG. 5 includes a sheet-like central portion 30 that overlaps the first base portion 11 and the second base portion 12 and is located between the first opposing surface 11a and the second opposing surface 12a. When manufacturing such a hollow structure film 1, a material for the central portion 30 is prepared before the step of thermocompression bonding a pair of single-sided shaped objects 80. In this embodiment, the central portion 30 of the hollow structure film 1 to be manufactured contains a resin. Furthermore, the central portion 30 of the hollow structure film 1 to be manufactured contains particles 50. Furthermore, the central portion 30 of the hollow structure film 1 to be manufactured contains a compound having a radiation-active double bond. In this case, the material for the central portion 30 can be a resin sheet 32 ​​formed into a sheet by dispersing the particles 50 and the compound in a resin. For example, the resin contained in the central portion 30 has a lower melting point than the resin contained in the shaped object-corresponding portion 13. When manufacturing a hollow structure film 1 having a central portion 30, as shown in Figure 7B, when a pair of single-sided shaped bodies 80 are overlapped, a resin sheet 32 ​​is placed between the pair of single-sided shaped bodies 80.

[0123] Next, as shown in FIG. 8A, the pair of single-sided shaped objects 80 are heat-pressed together. This bonds the pair of single-sided shaped objects 80 to each other. As shown in FIG. 7B, when a resin sheet 32 ​​is placed between the pair of single-sided shaped objects 80, the pair of single-sided shaped objects 80 are heat-pressed together as shown in FIG. 8A, and the pair of single-sided shaped objects 80 are bonded to the resin sheet 32 ​​at the multiple convex portions 82. This bonds the pair of single-sided shaped objects 80 via the resin sheet 32. At this time, in the portion of the pair of single-sided shaped objects 80 where the multiple convex portions 82 face each other, portions of the multiple support portions 20 extending from the first opposing surface 11a to the second opposing surface 12a are formed. In particular, in the portion of the pair of single-sided shaped objects 80 where the multiple convex portions 82 face each other, a continuous support portion 23 is formed. This forms a shaped object corresponding portion 13 from the pair of single-sided shaped objects 80. Furthermore, the central portion 30 is formed from the resin sheet 32. Furthermore, a pair of bases 10 (a first base 11 and a second base 12) are formed from the base 81 of the single-sided shaped object 80.

[0124] The heating temperature when the pair of single-sided shaped objects 80 are thermocompression-bonded is higher than the Vicat softening point temperature of the resin contained in the central portion 30. In particular, as described above, when the resin contained in the central portion 30 is linear low-density polyethylene, the heating temperature when the pair of single-sided shaped objects 80 are thermocompression-bonded is higher than the Vicat softening point temperature of the linear low-density polyethylene. This allows the resin sheet 32 ​​to be softened by thermocompression, and the pair of single-sided shaped objects 80 to be bonded to the resin sheet 32. In this case, as described above, the resin contained in the central portion 30 has a lower melting point than the resin contained in the shaped object corresponding portion 13, so that when the resin contained in the central portion 30 is heated to a temperature higher than the Vicat softening point temperature, significant deformation of the single-sided shaped objects 80 due to heating can be suppressed. The heating temperature when the pair of single-sided shaped objects 80 are thermocompression-bonded can be set to or below the Vicat softening point of the resin contained in the single-sided shaped objects 80. A spacer 92 as shown in Fig. 8A may be used when the pair of single-sided shaped bodies 80 are heat-pressed together. The spacer 92 controls the pair of single-sided shaped bodies 80 so that they do not approach each other more than a certain distance when the pair of single-sided shaped bodies 80 are brought closer to each other during heat-pressure bonding. The spacer 92 allows the thickness of the hollow structure film 1 to be manufactured to be adjusted.

[0125] In the step of thermocompression bonding a pair of single-sided shaped objects 80, instead of the method using the spacer 92 described above, the pair of single-sided shaped objects 80 may be thermocompression bonded by the following method. First, the pair of single-sided shaped objects 80 are processed into a film shape having a certain length or more. Next, the pair of single-sided shaped objects 80 are overlapped so that the multiple convex portions 82 face each other at least in part. Next, the pair of single-sided shaped objects 80 are passed between two heated rolls while overlapping each other. In this case, when manufacturing a hollow structure film 1 having a central portion 30, a resin sheet 32 ​​having a certain length or more is prepared and sandwiched between the pair of overlapping single-sided shaped objects 80. In this state, the pair of single-sided shaped objects 80 and the resin sheet 32 ​​are passed between two heated rolls. The pair of single-sided shaped objects 80 may be thermocompression bonded by the above method. When this method using two rolls is adopted, instead of using a spacer 92, the thickness of the hollow structure film 1 produced can be adjusted to a suitable thickness by adjusting the distance between the two rolls.

[0126] Next, a crosslinking step is performed in which a compound having a radiation-active double bond contained in the single-sided shaped object 80 is reacted with a resin. If the compound having a radiation-active double bond contained in the single-sided shaped object 80 is an electron beam crosslinking agent, the electron beam crosslinking agent is irradiated with an electron beam in the crosslinking step to react the compound with the resin. In this case, the conditions for the electron beam irradiation in the crosslinking step are, for example, as follows: The electron beam irradiation dose is, for example, 5 kGy to 500 kGy (0.5 Mrad to 50 Mrad), preferably 10 kGy to 300 kGy (1 Mrad to 30 Mrad). The electron beam irradiation dose is, for example, 200 kGy (20 Mrad). The electron beam acceleration voltage is, for example, 165 kV. When a resin sheet 32 ​​formed by dispersing a compound having a radiation-active double bond in a resin and molding it into a sheet is used as the material for the central portion 30, the compound contained in the resin sheet 32 ​​may be reacted with the resin in the crosslinking step. In this case, the method for reacting the compound contained in the resin sheet 32 ​​with the resin is the same as the method for reacting the compound contained in the single-sided shaped body 80 with the resin. In this way, the hollow structure film 1 shown in FIG. 5 is produced.

[0127] The circuit board 100 having the hollow structure film 1 and the wiring pattern as described above can be manufactured, for example, by the following method. The metal layer 40 is formed so that the entire surface of the hollow structure film 1 on which the wiring pattern is to be formed is covered with the metal layer 40. For example, when manufacturing a laminate 83 in which the metal layer 40 and a single-sided shaped body 80 are laminated as shown in FIG. 7A, the laminate 83 is manufactured so that the entire surface of the single-sided shaped body 80 on which the multiple protrusions 82 are not formed is covered with the metal layer 40. By manufacturing the hollow structure film 1 using this laminate 83, the entire surface of the hollow structure film 1 on which the wiring pattern is to be formed is covered with the metal layer 40. The metal layer 40 can be, for example, a copper layer. As an example, the metal layer 40 is bonded to the single-sided shaped body 80 via the metal adjacent layer 60. The metal layer 40 thus formed is covered with a mask layer and then etched, thereby forming a wiring pattern from at least a portion of the metal layer 40. More specifically, the metal layer 40 is etched using, for example, a patterned dry film resist (DFR) as a mask, thereby forming a wiring pattern from at least a part of the metal layer 40. This allows the production of a circuit board 100 including the hollow structure film 1 and the wiring pattern.

[0128] The circuit board 100 including the hollow structure film 1 and the wiring pattern may be manufactured by the following method. First, as shown in FIG. 8B, a single-sided shaped object 80 is formed. The pair of single-sided shaped objects 80 shown in FIG. 8B has the same shape as the single-sided shaped object 80 included in the laminate 83 shown in FIG. 7A. Next, a process of thermocompression bonding the pair of single-sided shaped objects 80 is performed. In this process, as an example, as shown in FIG. 8B, a resin sheet 32 ​​is placed between the pair of single-sided shaped objects 80. Next, as shown in FIG. 8C, the pair of single-sided shaped objects 80 are thermocompression bonded. This bonds the pair of single-sided shaped objects 80 to each other. Next, a metal layer 40 is formed so as to cover the entire surface of the single-sided shaped object 80 on which the multiple protrusions 82 are not formed. As an example, the metal layer 40 is bonded to the single-sided shaped object 80 via a metal adjacent layer 60. By etching the metal layer 40 thus formed using the method described above or the like, a wiring pattern can be formed from at least a portion of the metal layer 40. This allows the circuit board 100 having the hollow structure film 1 and the wiring pattern as described above to be manufactured.

[0129] The wiring pattern may be formed by attaching pre-formed copper wiring to the base 10. The wiring pattern may also be formed by forming a pattern of a plating seed layer by printing, including inkjet printing, and then plating up.

[0130] The antenna equipment 101 shown in Fig. 6C can be manufactured by forming wiring 41 and an antenna element 102 from a metal layer 40 that constitutes at least a part of the first surface 1a of the hollow structure film 1 as shown in Fig. 5. The method for forming the wiring 41 and the antenna element 102 from the metal layer 40 can be the same as the method for forming a wiring pattern from the metal layer 40 in the manufacturing method of the circuit board 100 described above.

[0131] The wiring pattern may be formed by printing using conductive ink or by processing using a metal 3D printer.

[0132] The hollow structure film 1 of this embodiment includes a sheet-like first base 11, a sheet-like second base 12 overlapping the first base 11, and a plurality of support columns 20 provided between the first base 11 and the second base 12. The first base 11 has a first opposing surface 11a facing the second base 12. The second base 12 has a second opposing surface 12a facing the first base 11. At least some of the support columns 20 form continuous support columns 23 extending from the first opposing surface 11a to the second opposing surface 12a. This forms a plurality of hollow sections B between the first base 11 and the second base 12. For this reason, the hollow structure film 1 has a hollow structure. With this hollow structure film 1, the dielectric constant of the hollow structure film 1 can be reduced while being less subject to limitations on the material of the hollow structure film 1. Furthermore, the hollow structure of the hollow-structure film 1 allows the hollow-structure film 1 to have a low dielectric loss tangent. The dielectric loss tangent indicates the amount of an electrical signal propagating through a dielectric that is converted into heat and lost. The lower the dielectric loss tangent of the hollow-structure film 1, the more likely it is that signal loss will be reduced and the electrical signal transmission rate will be improved when the hollow-structure film 1 is used in a circuit board designed for communication.

[0133] The effect of the low dielectric constant and dielectric loss tangent values ​​of the hollow structure film 1 will be explained in more detail. There is a demand for higher frequencies of electrical signals handled in information and communication devices such as smartphones and tablet terminals. As the frequency of these electrical signals increases, the transmission loss in circuit boards designed for communication increases (negative transmission loss values ​​move away from zero). On the other hand, it is known that transmission loss, particularly dielectric loss, can be reduced (negative transmission loss values ​​approach zero) by lowering the dielectric constant and dielectric loss tangent values ​​of the circuit board. Dielectric loss is expressed by the following formula (1). In formula (1), α ｄ is the dielectric loss, K is the proportionality constant, f is the frequency, ε γ is the relative permittivity, and tanδ is the dielectric loss tangent. γ is the ratio of the dielectric constant of an object, such as a circuit board, to the dielectric constant of a vacuum.

[0134] From equation (1), it can be seen that dielectric loss can be reduced by lowering the dielectric constant and dielectric dissipation factor of the circuit board. In particular, it can be seen that dielectric loss can be reduced by lowering the dielectric constant and dielectric dissipation factor of the circuit board, even when the frequency is increased, i.e., when the electrical signal is at a higher frequency. From the above, by using the hollow structure film 1 of the present embodiment in a circuit board designed for communication, in particular, it is possible to reduce signal loss and improve the transmission rate of electrical signals. Circuit boards that handle high-frequency electrical signals are particularly required to have low dielectric constants and dielectric dissipation factor. For this reason, the hollow structure film 1 of the present embodiment is suitable for use in circuit boards that handle high-frequency electrical signals. The hollow structure film 1 of the present embodiment is suitable for use in circuit boards that handle electrical signals with frequencies of 6 GHz or higher, particularly 26 GHz or higher, and particularly 60 GHz or higher. The hollow structure film 1 of the present embodiment may also be used in circuit boards that handle electrical signals with frequencies of 6 GHz or higher and 39 GHz or lower, particularly 26 GHz or higher and 39 GHz or lower. The hollow structure film 1 of this embodiment may be used for a circuit board that handles electrical signals with frequencies of 60 GHz or more and 80 GHz or less.

[0135] Low-dielectric-constant sheets are also known, such as the low-dielectric sheet for two-dimensional communication disclosed in Japanese Patent No. 5,976,714, which is manufactured by forming a resin foam containing bubbles. Examples of resin foam sheets containing bubbles include Softlon manufactured by Sekisui Chemical Co., Ltd. and SKYBOND® FOAM manufactured by IST Corporation. However, the hollow structure film 1 of the present embodiment is clearly different from sheets made of resin foam in that it includes multiple support columns 20, and in particular, at least a portion of the multiple support columns 20 form continuous support columns 23. The hollow structure film 1 of the present embodiment has greater hardness than sheets made of resin foam due to the presence of multiple support columns 20. In particular, the hollow structure film 1 of the present embodiment has greater indentation hardness than sheets made of resin foam. Thus, the hollow structure film 1 of the present embodiment is clearly different from sheets made of resin foam in terms of physical properties such as hardness. Because a resin foam sheet is flexible and easily bends, it is considered difficult to use it to form a circuit board 100 such as an antenna equipment 101. As described above, the hollow structure film 1 of this embodiment can provide a film with a low dielectric constant while ensuring strength.

[0136] The hollow structure film 1 of this embodiment further includes a sheet-like central portion 30 that overlaps the first base portion 11 and the second base portion 12 and is located between the first opposing surface 11 a and the second opposing surface 12 a, thereby increasing the strength of the hollow structure film 1.

[0137] The hollow structure film 1 of this embodiment includes a main body 1c. The main body 1c includes a first base 11, a second base 12, a plurality of support columns 20, and a sheet-like central portion 30 located between the first opposing surface 11a and the second opposing surface 12a. The support columns 20 are located on the first opposing surface 11a side and the second opposing surface 12a side of the central portion 30. This allows the hollow structure film 1 to have greater strength.

[0138] The hollow structure film 1 of this embodiment contains glass particles 51. This can reduce the amount of shrinkage of the hollow structure film 1 after processing by heating.

[0139] In the hollow structure film 1 of this embodiment, the glass particles 51 have hollow portions 52. This can reduce the amount of shrinkage of the hollow structure film 1 after processing by heating.

[0140] The hollow structure film 1 of this embodiment has a first surface 1a and a second surface 1b located on the opposite side of the first surface 1a. The hollow structure film 1 of this embodiment further includes a metal layer 40 constituting at least a part of at least one of the first surface 1a and the second surface 1b. By forming a wiring pattern on the metal layer 40, wiring 41 can be formed from the metal layer 40.

[0141] The hollow structure film 1 of this embodiment further includes a metal adjacent layer 60 that joins the metal layer 40 to the base 10. This allows the metal layer 40 to be more firmly joined to the base 10.

[0142] The circuit board 100 of this embodiment includes the hollow structure film 1 described above, which has a first surface 1a and a second surface 1b located on the opposite side of the first surface 1a, and a wiring pattern provided on at least one of the first surface 1a and the second surface 1b. This allows the dielectric constant of the circuit board 100 to be low.

[0143] The antenna equipment 101 of this embodiment includes the above-described circuit board 100 and an antenna element connected to the circuit board 100. This allows the dielectric constant of the circuit board 100 to be reduced, thereby reducing transmission loss in the circuit board (negative transmission loss values ​​can be brought closer to zero).

[0144] The effects of this embodiment will be described in relation to the prior art. As a technique for lowering the dielectric constant of a circuit board or the like compared to conventional techniques, a technique for using a material with a low dielectric constant for the circuit board or the like is known (see, for example, JP 2023-121649 A).

[0145] Japanese Patent Application Laid-Open No. 2023-121649 describes a technique for lowering the relative dielectric constant of a material by using a polyimide film as a material applied to high-frequency substrates and the like.

[0146] However, when a material with a low dielectric constant is used to lower the dielectric constant of a film used in a circuit board, it is necessary to use a specific material, which can cause inconveniences. For example, the cost required for manufacturing the circuit board can increase. Therefore, there has been a demand for a film used in a circuit board that has a low dielectric constant while being less subject to material restrictions.

[0147] According to this embodiment, it is possible to provide a film having a low dielectric constant while being less subject to material limitations.

[0148] <Modifications> Next, various modifications of the present embodiment will be described with reference to Figures 9 to 12. In Figures 9 to 12, the same parts as those in the embodiment shown in Figures 1 to 8C are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0149] <Modification 1> In the above-described embodiment, a hollow structure film 1 has been described in which the base 10 has a plurality of connection portions 24 extending in the first direction d1, but does not have any connection portions 24 extending in any direction other than the first direction d1, as shown in FIG. 2 . Furthermore, a hollow structure film 1 has been described in which the base 10 has a plurality of support columns 20 extending in the first direction d1, but does not have any support columns 20 extending in any direction other than the first direction d1. However, the extending directions of the connection portions 24 and the support columns 20 are not limited to the above-described examples. FIG. 9 is a plan view showing the base 10 of Modification 1 as viewed from the thickness direction of the hollow structure film 1, and corresponds to FIG. 2 . In the example shown in FIG. 9 , the base 10 has a plurality of connection portions 24. In the example shown in FIG. 9 , the base 10 has a first connection portion 24a extending in the first direction d1 as the plurality of connection portions 24. In addition, in the example shown in Figure 9, the base 10 has, as the multiple connection portions 24, second connection portions 24b extending in a third direction d3 perpendicular to the thickness direction of the hollow structure film 1 and different from the first direction d1. In the example shown in Figure 9, the third direction d3 is perpendicular to the first direction d1. In other words, the third direction d3 coincides with the second direction d2. Because the base 10 has the first connection portions 24a and the second connection portions 24b as the multiple connection portions 24, the hollow structure film 1 of variant 1 has multiple support columns 20 extending in the first direction d1 and multiple support columns 20 extending in the third direction d3. A hollow structure can be formed and the dielectric constant can be kept low using the base 10 having such connection portions 24 and the hollow structure film 1 having support columns 20.

[0150] The hollow structure film 1 of Modification 1 includes a plurality of support columns 20 extending in the first direction d1 and a plurality of support columns 20 extending in the third direction d3. In such a hollow structure film 1, the above-mentioned angles θ1, θ2, and porosity are measured based on a portion of a cross section taken along a plane that passes through the plurality of support columns 20 and is perpendicular to the first direction d1, where the plurality of support columns 20 extending in the third direction d3 are not visible.

[0151] <Modification 2> In the above-described embodiment, the hollow structure film 1 has been described as having a central portion 30 as shown in FIG. 1 . However, the hollow structure film 1 does not necessarily have to have the central portion 30. FIG. 10 is a cross-sectional view of the hollow structure film 1 of Modification 2, taken along a cross section parallel to the thickness direction of the hollow structure film 1, and corresponds to FIG. 1 . In the example shown in FIG. 10 , the hollow structure film 1 does not have a central portion 30. In the example shown in FIG. 10 , at least some of the multiple support columns 20 extend in the thickness direction of the hollow structure film 1 from the first opposing surface 11 a to the second opposing surface 12 a. In the example shown in FIG. 10 , some of the multiple support columns 20 form continuous support columns 23. The portions of the multiple support columns 20 that do not form the continuous support columns 23 form convex portions 25 that protrude from the first opposing surface 11 a toward the second opposing surface 12 a or from the second opposing surface 12 a toward the first opposing surface 11 a.

[0152] In the hollow structure film 1 in which some of the support columns 20 form the convex portions 25 as shown in Figure 10, the height of the convex portions 25 (the dimension of the convex portions 25 in the thickness direction of the hollow structure film 1) is defined as height w4. In this case, the height w4 is preferably 0.5 to 10 times the width w2 of the connection portion 24 in the second direction d2. By making the height w4 0.5 times or more the width w2, the size of the hollow portion B can be ensured to be particularly large, and the dielectric constant of the hollow structure film 1 can be particularly low. By making the height w4 10 times or less the width w2, the strength of the hollow structure film 1 can be particularly high.

[0153] A hollow structure film 1 without a central portion 30 as shown in FIG. 10 can be manufactured by a method similar to the manufacturing method of the hollow structure film 1 with a central portion 30 of the above-described embodiment, except for the points described below. In the step of heat-pressing a pair of single-sided shaped bodies 80, the pair of single-sided shaped bodies 80 are overlapped without placing a resin sheet 32 ​​between them. The pair of single-sided shaped bodies 80 are then heat-pressed together. This bonds the opposing convex portions 82 of the pair of single-sided shaped bodies 80 together. Bonding the opposing convex portions 82 together forms a continuous support portion 23. This directly bonds the pair of single-sided shaped bodies 80 together. The convex portion 82 of one of the pair of single-sided shaped bodies 80 that does not face the convex portion 82 of the other of the pair of single-sided shaped bodies 80 when the pair of single-sided shaped bodies 80 are overlapped constitutes the convex portion 25 in the manufactured hollow structure film 1. The heating temperature when the pair of single-sided shaped objects 80 are heat-pressed together is adjusted to a temperature at which the pair of single-sided shaped objects 80 can be softened and directly bonded together.

[0154] The hollow structure film 1 of the second modification also forms a hollow structure, making it possible to keep the dielectric constant low.

[0155] <Modification 3> When producing a hollow structure film 1 without a central portion 30, the hollow structure film 1 may be produced using a pair of single-sided shaped bodies 80 described below. FIG. 11 is a diagram showing a single-sided shaped body 80 used in the hollow structure film production method of Modification 3. In the example shown in FIG. 11, the single-sided shaped body 80 comprises a first layer 84 containing a first resin and a second layer 85 overlapping the first layer 84 and containing a second resin. In the example shown in FIG. 11, the surface of the single-sided shaped body 80 on which the multiple convex portions 82 are formed is constituted by the first layer 84. The thickness of the first layer 84 is constant. The second layer 85 constitutes the portions of the multiple convex portions 82 not constituted by the first layer 84, as well as the base 81. The first resin contained in the first layer 84 has a lower melting point than the second resin contained in the second layer 85. With this configuration, when a pair of single-sided shaped objects 80 are heat-pressed together, the first layer 84 can be sufficiently melted while maintaining the shape of the second layer 85. This makes it possible to bond the pair of single-sided shaped objects 80 together while preventing deformation of the overall shape of the single-sided shaped objects 80. The first resin in Modification 3 is, for example, the same as the resin contained in the central portion 30 in the above-described embodiment. The material of the first layer 84 in Modification 3 may be the same as the material of the central portion 30 in the above-described embodiment. That is, the first layer 84 may include particles 50 that may be contained in the central portion 30 in the above-described embodiment. The first layer 84 may include a compound having a radiation-active double bond that may be contained in the central portion 30 in the above-described embodiment. The second resin in Modification 3 is, for example, the same as the resin contained in the shaped object corresponding portion 13 in the above-described embodiment.

[0156] The single-sided shaped body 80 shown in Figure 11 can be produced by co-extrusion molding using a mold similar to the mold 90 shown in Figure 7A, by molding the material of the second layer 85 containing the second resin and the material of the first layer 84 containing the first resin onto the metal foil 42.

[0157] By using a pair of single-sided shaped bodies 80 shown in FIG. 11 , a hollow structure film 1 without a central portion 30, as shown in FIG. 12 , can be produced. The manufacturing method for the hollow structure film 1 in this case can be the same as the manufacturing method for the hollow structure film 1 without a central portion 30 of the above-described variant 2, except for the points described below. The heating temperature when the pair of single-sided shaped bodies 80 are thermocompressed together is adjusted to a temperature that softens the first layer 84 of the single-sided shaped bodies 80 and allows the pair of single-sided shaped bodies 80 to be directly bonded together. As an example, the heating temperature when the pair of single-sided shaped bodies 80 are thermocompressed together is higher than the Vicat softening point temperature of the first resin contained in the first layer 84. This allows the first layer 84 to be softened by thermocompression, allowing the opposing convex portions 82 of the pair of single-sided shaped bodies 80 to be bonded together. In particular, the portions of the opposing convex portions 82 of the pair of single-sided shaped bodies 80 that are formed by the first layer 84 can be bonded together. In this case, as described above, since the first resin has a lower melting point than the second resin, when the first layer 84 is heated to a temperature equal to or higher than the Vicat softening point temperature of the first resin, the second layer 85 can be prevented from being significantly deformed by heating.

[0158] <Modification 4> In the above-described embodiment and each modification, an example has been described in which a hollow structure film 1 is manufactured using two single-sided shaped objects 80. However, the manufacturing method of the hollow structure film 1 is not limited to this. The hollow structure film 1 may also be manufactured using one single-sided shaped object 80. Figure 13 is a diagram showing a manufacturing method of a hollow structure film of Modification 4. Figure 14 is a diagram showing a hollow structure film 1 manufactured by the manufacturing method of a hollow structure film of Modification 4.

[0159] In the example shown in FIG. 13 , a resin sheet 32 ​​is arranged to face the surface of one single-sided shaped object 80 on which multiple convex portions 82 are formed. The hollow structure film manufacturing method of Variation 4 includes a step of heat-pressing the single-sided shaped object 80 and the resin sheet 32 ​​arranged as shown in FIG. 13 together. This allows for the manufacture of a hollow structure film 1 having a pair of bases 10 and multiple support portions 20 as shown in FIG. 14 . At this time, multiple support portions 20 are formed from the multiple convex portions 82 of the single-sided shaped object 80. In the example shown in FIG. 14 , a first base 11 is formed from the base 81 of the single-sided shaped object 80. In the example shown in FIG. 14 , a second base 12 is formed from the resin sheet 32. Although not shown, the second base 12 may be formed from the base 81 of the single-sided shaped object 80, and the first base 11 may be formed from the resin sheet 32.

[0160] A spacer 92 as shown in Fig. 13 may be used when the single-sided shaped object 80 and the resin sheet 32 ​​are heat-pressed together. The spacer 92 controls the single-sided shaped object 80 and the resin sheet 32 ​​so that they do not approach each other more than a certain distance when the single-sided shaped object 80 and the resin sheet 32 ​​are brought closer to each other during heat-pressure bonding. The spacer 92 allows the thickness of the hollow structure film 1 to be manufactured to be adjusted.

[0161] As shown in Fig. 14, the hollow structure film 1 of Modification 4 may include a metal layer 40 constituting at least a part of at least one of the first surface 1a and the second surface 1b of the hollow structure film 1. As shown in Fig. 14, the hollow structure film 1 of Modification 4 may include a metal adjacent layer 60 that bonds the metal layer 40 to the base 10. In this case, the metal layer 40 may be bonded to the single-sided shaped object 80 or the resin sheet 32 ​​via the metal adjacent layer 60 before the step of heat-pressing the single-sided shaped object 80 and the resin sheet 32 ​​together, or may be bonded to the base 10 via the metal adjacent layer 60 after the step of heat-pressing the single-sided shaped object 80 and the resin sheet 32 ​​together.

[0162] According to the hollow structure film manufacturing method and hollow structure film 1 of Modification 4, a hollow structure film 1 having a particularly small thickness can be provided.

[0163] <Modification 5> In the above-described embodiment and each modification, an example has been described in which a hollow structure film 1 is manufactured using two or less single-sided shaped objects 80. However, the manufacturing method of the hollow structure film 1 is not limited to this. The hollow structure film 1 may be manufactured using three or more single-sided shaped objects 80. Figure 15 is a diagram showing the components used in the manufacturing method of the hollow structure film of modification 5, arranged in the order in which they are stacked when manufacturing the hollow structure film 1. Figure 16 is a diagram showing the hollow structure film 1 manufactured by the manufacturing method of the hollow structure film of modification 5.

[0164] In the example shown in FIG. 15 , the components used in the manufacturing method for hollow structure films include four single-sided shaped bodies 80. The four single-sided shaped bodies 80 are stacked in the thickness direction of the base 81. The components used in the manufacturing method for hollow structure films further include three resin sheets 32. The four single-sided shaped bodies 80 and the three resin sheets 32 are stacked so as to be alternately arranged in the thickness direction of the base 81. The manufacturing method for hollow structure films in Variation 4 includes a step of heat-pressing the single-sided shaped bodies 80 and the resin sheets 32 arranged as shown in FIG. 15 . This allows the manufacturing of a hollow structure film 1 having a pair of bases 10 and multiple support portions 20 as shown in FIG. 16 . At this time, multiple support portions 20 are formed from the multiple protrusions 82 of the multiple single-sided shaped bodies 80. In particular, in the portion where the plurality of single-sided shaped bodies 80 are overlapped so that the plurality of convex portions 82 face each other, a continuous support portion 23 is formed that extends from the first opposing surface 11 a to the second opposing surface 12 a of the plurality of support portions 20. A pair of bases 10 are formed from the bases 81 of a pair of single-sided shaped bodies 80 that are located outermost in the thickness direction of the bases 81.

[0165] In the step of thermocompression bonding the single-sided objects 80 and the resin sheets 32, the order in which the single-sided objects 80 and the resin sheets 32 are thermocompression bonded together is not particularly limited. The hollow structure film 1 may be manufactured by simultaneously thermocompression bonding all of the single-sided objects 80 and the resin sheets 32. The hollow structure film 1 may also be manufactured by repeatedly thermocompression bonding adjacent single-sided objects 80 and the resin sheets 32. The hollow structure film 1 shown in FIG. 16 may be manufactured by the following method. The first single-sided object 80a and the second single-sided object 80b shown in FIG. 15 are joined via the first resin sheet 32a. Furthermore, the third single-sided object 80c and the fourth single-sided object 80d shown in FIG. 15 are joined via the second resin sheet 32b. Thereafter, the second single-sided shaped object 80b and the third single-sided shaped object 80c are joined together via the third resin sheet 32c.

[0166] As shown in Fig. 16, the hollow structure film 1 of Modification 5 may include a metal layer 40 constituting at least a part of at least one of the first surface 1a and the second surface 1b of the hollow structure film 1. As shown in Fig. 16, the hollow structure film 1 of Modification 5 may include a metal adjacent layer 60 that joins the metal layer 40 to the base 10. In this case, the metal layer 40 may be joined to one of the single-sided shaped objects 80 via the metal adjacent layer 60 before the step of thermocompression bonding the single-sided shaped object 80 and the resin sheet 32, or may be joined to the base 10 via the metal adjacent layer 60 after the step of thermocompression bonding the single-sided shaped object 80 and the resin sheet 32.

[0167] According to the hollow structure film manufacturing method and hollow structure film 1 of the modified example 5, a hollow structure film 1 having a particularly large thickness can be provided.

[0168] <Modification 6> The main body 1c of the hollow structure film 1 may include an insulating inorganic material member 70. The maximum width of the inorganic material member 70 is three times or more the minimum width of the inorganic material member. Fig. 17 is a cross-sectional view showing an example of the hollow structure film 1 of Modification 6. Fig. 18 is a cross-sectional view showing an example of the hollow structure film 1 of Modification 6 that is different from the example shown in Fig. 17.

[0169] The inorganic material member 70 contains, for example, glass or a metal oxide. The inorganic material member 70 may contain glass. The inorganic material member 70 may contain a metal oxide. The metal oxide contained in the inorganic material member 70 is, for example, aluminum oxide. The inorganic material member 70 may contain boehmite. The inorganic material member 70 may contain a ceramic material. When the inorganic material member 70 contains a ceramic material, a material with a sufficiently small dielectric constant and dielectric loss tangent is used as the ceramic material, taking into consideration the need to sufficiently reduce the dielectric constant and dielectric loss tangent of the entire hollow structure film 1.

[0170] The inorganic material member 70 may be included in at least one of the first base 11 and the second base 12. The inorganic material member 70 may be included in both the first base 11 and the second base 12. The inorganic material member 70 may be included in at least some of the plurality of support members 20. The inorganic material member 70 may be included in all of the plurality of support members 20. In the case where the main body 1c has a central portion 30, the inorganic material member 70 may be included in at least the central portion 30. In the example shown in FIG. 17 , the inorganic material member 70 is included in both the first base 11 and the second base 12. In the example shown in FIG. 18 , the inorganic material member 70 is included in the first base 11, the second base 12, all of the plurality of support members 20, and the central portion 30.

[0171] The inorganic material member 70 may be a sheet-like member as shown in Fig. 17. The sheet-like inorganic material member 70 is, for example, a woven fabric made from fibrous glass, known as glass cloth.

[0172] When the inorganic material member 70 is a sheet-like member, the minimum width of the inorganic material member 70 is the thickness of the sheet-like inorganic material member 70. When the thickness of the sheet-like inorganic material member 70 is not constant, the minimum width of the inorganic material member 70 is the minimum value of the thicknesses of the sheet-like inorganic material member 70 measured at 10 locations. When the inorganic material member 70 is a sheet-like member, the maximum width of the inorganic material member 70 is the maximum value of the dimension of the inorganic material member 70 in a direction parallel to the surface of the sheet-like inorganic material member 70.

[0173] In the example shown in FIG. 17 , a sheet-like inorganic material member 70 is included in both the first base 11 and the second base 12. The surface of the first base 11 opposite the first opposing surface 11a is referred to as the first outer surface 11b. The sheet-like inorganic material member 70 included in the first base 11 is located between the first opposing surface 11a and the first outer surface 11b. The thickness direction of the sheet-like inorganic material member 70 is oriented in the same direction as the thickness direction of the first base 11. The surface of the second base 12 opposite the second opposing surface 12a is referred to as the second outer surface 12b. The sheet-like inorganic material member 70 included in the second base 12 is located between the second opposing surface 12a and the second outer surface 12b. The thickness direction of the sheet-like inorganic material member 70 is oriented in the same direction as the thickness direction of the second base 12.

[0174] Although not shown, when the main body 1c has a central portion 30, the sheet-like inorganic material member 70 may be included in the central portion 30. In this case, the sheet-like inorganic material member 70 may be located between the first central surface 30a and the second central surface 30b. The thickness direction of the sheet-like inorganic material member 70 may be oriented in the same direction as the thickness direction of the central portion 30.

[0175] The inorganic material members 70 may be a plurality of rod-shaped members as shown in FIG. 18 . The plurality of rod-shaped inorganic material members 70 may be, for example, fibrous glass known as glass fiber. In the example shown in FIG. 18 , the plurality of rod-shaped inorganic material members 70 are dispersed inside the main body 1c. The plurality of rod-shaped inorganic material members 70 are oriented in different directions. The maximum width of the rod-shaped inorganic material members 70 is, for example, 100 μm. In the example shown in FIG. 18 , the plurality of rod-shaped inorganic material members 70 are included in the first base 11, the second base 12, all of the plurality of support members 20, and the central portion 30.

[0176] When the inorganic material member 70 is a rod-shaped member, the maximum width of the inorganic material member 70 is the dimension of the inorganic material member 70 in the extension direction of the rod-shaped inorganic material member 70. When the inorganic material member 70 is a rod-shaped member, the minimum width of the inorganic material member 70 is the smallest value of the dimension of the inorganic material member 70 in a direction perpendicular to the extension direction of the rod-shaped inorganic material member 70.

[0177] Although not shown, the inorganic material member 70 may be a plurality of scale-like members. The plurality of scale-like inorganic material members 70 may be, for example, Glass Flake (registered trademark) manufactured by Nippon Sheet Glass Co., Ltd. The plurality of scale-like inorganic material members 70 may be Fine Flake (registered trademark) manufactured by Nippon Sheet Glass Co., Ltd. The plurality of scale-like inorganic material members 70 may be dispersed inside the main body 1c. The plurality of scale-like inorganic material members 70 may be oriented in different directions from each other.

[0178] When the inorganic material member 70 is a scaly member, the minimum width of the inorganic material member 70 is the thickness of the scaly inorganic material member 70. The maximum width of the inorganic material member 70 is the maximum value of the dimension of the inorganic material member 70 in a direction perpendicular to the thickness direction of the scaly inorganic material member 70.

[0179] The maximum width of the scaly inorganic material member 70 is, for example, 200 μm. The minimum width (thickness) of the scaly inorganic material member 70 is, for example, 0.3 μm or more and 6 μm or less. When the inorganic material member 70 is a plurality of scaly members, the material of the inorganic material member 70 can be the same as the material of the inorganic material member 70 described above. The inorganic material member 70 that is a plurality of scaly members may contain glass. The inorganic material member 70 that is a plurality of scaly members may contain aluminum oxide. The inorganic material member 70 that is a plurality of scaly members may contain boehmite.

[0180] Although not shown, the main body 1c may include, as the inorganic material member 70, two or more members selected from the group consisting of a sheet-like member, a plurality of rod-like members, and a plurality of scale-like members.

[0181] Although not shown, the inorganic material member 70 may have a shape other than a sheet, rod, or scale shape. In this case, the maximum width and minimum width of the inorganic material member 70 are defined by the following method. When the dimensions of the inorganic material member 70 are measured in all directions, consider the direction da in which the dimension of the inorganic material member 70 is greatest. The maximum width of the inorganic material member 70 is defined as the dimension of the inorganic material member 70 in the direction da. The minimum width of the inorganic material member 70 is defined as the smallest value of the dimension of the inorganic material member 70 in a direction perpendicular to the direction da.

[0182] The main body 1c including the inorganic material member 70 may further include the above-described glass particles 51. The main body 1c including the inorganic material member 70 may not include the glass particles 51. The maximum width of the glass particles 51 may be less than three times the minimum width of the glass particles.

[0183] The effect of the main body 1c including the inorganic material member 70 will be described. Consider the case where the metal layer 40 is bonded to a portion constituting at least a portion of the main body 1c (such as the base 10, the single-sided shaped body 80, and the resin sheet 32). In this case, the metal layer 40 may peel off from the main body 1c or wrinkles may occur due to the difference in CTE (coefficient of thermal expansion) between the main body 1c and the metal layer 40. In particular, when heat is applied to the metal layer 40 and the main body 1c when bonding the metal layer 40 and the main body 1c, the difference in CTE between the main body 1c and the metal layer 40 may cause the metal layer 40 to peel off from the main body 1c or wrinkles may occur. In particular, when the metal layer 40 is formed of copper foil and the main body 1c contains polyolefin, the difference in CTE between the main body 1c and the metal layer 40 may be large. In this case, the CTE of the metal layer 40 may be smaller than the CTE of the main body portion 1c, which may cause the metal layer 40 to peel off from the main body portion 1c or wrinkles to form in the metal layer 40.

[0184] In contrast, by including the inorganic material member 70 in the main body portion 1c, the CTE of the main body portion 1c can be adjusted. This allows the CTE of the hollow structure film 1, whose dielectric constant is kept low due to its hollow structure, to be adjusted. In particular, by including the inorganic material member 70 in the main body portion 1c of the hollow structure film 1, the CTE of the main body portion 1c can be adjusted so that the difference in CTE between the main body portion 1c and the metal layer 40 is reduced. In particular, by including the inorganic material member 70 in the main body portion 1c, the CTE of the main body portion 1c can be reduced. As an example, by including the inorganic material member 70 in the main body portion 1c, the CTE of the main body portion 1c can be set to 120 ppm / °C or less. By including glass or a metal oxide in the inorganic material member 70, particularly glass, the CTE of the main body portion 1c can be adjusted so that the difference in CTE between the main body portion 1c and the metal layer 40 is reduced. In particular, when the main body portion 1c contains polyolefin, the CTE of the main body portion 1c can be reduced by further including the inorganic material member 70. As described above, by including the inorganic material member 70 in the main body portion 1c, the CTE of the main body portion 1c can be adjusted to reduce the difference in CTE between the main body portion 1c and the metal layer 40, making the metal layer 40 less likely to peel from the main body portion 1c and less likely to wrinkle. In particular, when the metal layer 40 is formed of copper foil and the main body portion 1c contains polyolefin, the metal layer 40 can be less likely to peel from the main body portion 1c and less likely to wrinkle. Furthermore, by reducing the difference in CTE between the main body portion 1c and the metal layer 40, the hollow structure film 1 is less likely to warp due to the difference in CTE between the main body portion 1c and the metal layer 40. This ensures ease of processing of the hollow structure film 1.

[0185] The manufacturing method of the hollow structure film 1 of the sixth modified example can be the same as the manufacturing method of the hollow structure film 1 in the above-described embodiment, except that the single-sided shaped body 80 manufactured in the step of manufacturing a pair of single-sided shaped bodies 80 includes an insulating inorganic material member 70. At least one of the pair of single-sided shaped bodies 80 may include the inorganic material member 70. Both of the pair of single-sided shaped bodies 80 may include the inorganic material member 70. The inorganic material member 70 may be included in the base 81 of the single-sided shaped body 80. The inorganic material member 70 may be included in at least a portion of the plurality of convex portions 82. The inorganic material member 70 may be included in all of the plurality of convex portions 82. When a resin sheet 32 ​​is used in the manufacturing of the hollow structure film 1, the inorganic material member 70 may be included in the resin sheet 32.

[0186] The hollow structure film 1 shown in Fig. 17 can be produced from a pair of single-sided shaped bodies 80, each having a base 81 containing a sheet-like inorganic material member 70, and a resin sheet 32, as shown in Fig. 19. The hollow structure film 1 shown in Fig. 18 can be produced from a pair of single-sided shaped bodies 80, each having a base 81 and a plurality of protrusions 82 all containing rod-like inorganic material members 70, and a resin sheet 32 ​​containing rod-like inorganic material members 70, as shown in Fig. 20.

[0187] The hollow structure film 1 of Modification 6 includes a main body 1c having a sheet-like first base 11, a sheet-like second base 12 overlapping the first base 11, and a plurality of support columns 20 disposed between the first base 11 and the second base 12. The first base 11 has a first opposing surface 11a facing the second base 12. The second base 12 has a second opposing surface 12a facing the first base 11. At least some of the support columns 20 form continuous support columns 23 extending from the first opposing surface 11a to the second opposing surface 12a. The main body 1c includes an insulating inorganic material member 70. The maximum width of the inorganic material member 70 is at least three times the minimum width of the inorganic material member. This makes it difficult for the metal layer 40 to peel off from the main body 1c and wrinkles to form in the metal layer 40.

[0188] In the hollow structure film 1 of Modification 6, the inorganic material member 70 may be included in at least one of the first base 11 and the second base 12. This allows the CTE of the base 10 to be adjusted so that the difference in CTE between the base 10 and the metal layer 40 is small when the base 10 and the metal layer 40 are bonded together. This makes it difficult for the metal layer 40 to peel off from the base 10, and makes it difficult for wrinkles to form in the metal layer 40 bonded to the base 10.

[0189] In the hollow structure film 1 of the sixth modification, the inorganic material member 70 may be included in at least some of the support columns 20. This also makes it possible to adjust the CTE of the main body 1c so as to reduce the difference in CTE between the main body 1c and the metal layer 40. This makes it difficult for the metal layer 40 to peel off from the main body 1c, and makes it difficult for wrinkles to form in the metal layer 40.

[0190] In the hollow structure film 1 of Modification 6, the main body 1c may further have a sheet-like central portion 30 that overlaps the first base 11 and the second base 12 and is located between the first opposing surface 11a and the second opposing surface 12a. In this case, an inorganic material member 70 may be included in at least the central portion 30. This also makes it possible to adjust the CTE of the main body 1c so that the difference in CTE between the main body 1c and the metal layer 40 is small. This makes it difficult for the metal layer 40 to peel off from the main body 1c and makes it difficult for wrinkles to form in the metal layer 40.

[0191] In the hollow structure film 1 of the sixth modification, the inorganic material member 70 may contain glass. This makes it possible to more effectively adjust the CTE of the main body 1c by using the inorganic material member 70 so that the difference in CTE between the main body 1c and the metal layer 40 becomes smaller.

[0192] The maximum width of the inorganic material member 70 may be 10 μm or more. This makes it possible to more effectively adjust the CTE of the main body portion 1 c using the inorganic material member 70 so that the difference in CTE between the main body portion 1 c and the metal layer 40 becomes smaller.

[0193] The manufacturing method of the hollow structure film 1 of the sixth modification includes the steps of: using a mold 90 to prepare a pair of single-sided shaped bodies 80 each having a sheet-like base 81 and a plurality of protrusions 82 formed on one side of the base 81, and each including an insulating inorganic material member 70; and overlapping the pair of single-sided shaped bodies 80 so that the plurality of protrusions 82 face each other at least partially, and then thermocompression bonding the two bodies. The maximum width of the inorganic material member 70 is at least three times the minimum width of the inorganic material member. This manufacturing method allows the manufacture of a hollow structure film 1 whose main body 1c includes the inorganic material member 70.

[0194] The effect of Modification 6 will be described in relation to the prior art. As a sheet that can be used for circuit boards and has a dielectric constant lower than conventional sheets, there are known sheets manufactured by forming a resin foam containing bubbles, such as the low dielectric sheet for two-dimensional communication disclosed in Japanese Patent No. 5976714.

[0195] However, there has been a need to tailor the CTE (coefficient of thermal expansion) of low dielectric constant films used in circuit boards.

[0196] According to the sixth modification, the CTE of the low dielectric constant film can be adjusted.

[0197] <Modification 7> The shapes of the connecting portions 24 and the support portions 20 are not limited to the examples described in the above-mentioned embodiment and each modification. The hollow structure film 1 has a first end 1d and a second end 1e as ends in the first direction d1. In the hollow structure film 1, the connecting portions 24 and the support portions 20 do not have to extend from the first end 1d to the second end 1e.

[0198] In the example shown in Figure 2 above, the base 10 has multiple connection portions 24 extending in the first direction d1, but does not have any connection portions 24 extending in any direction other than the first direction d1. Furthermore, in the example shown in Figure 2 above, the hollow structure film 1 has multiple support columns 20 extending in the first direction d1, but does not have any support columns 20 extending in any direction other than the first direction d1. In the example shown in Figure 2 above, the connection portions 24 and support columns 20 extend from the first end 1d to the second end 1e. However, for hollow structure films 1 that do not have connection portions 24 and support columns 20 extending in any direction other than the first direction d1, the shapes of the connection portions 24 and support columns 20 are not limited thereto. Figure 21A is a plan view showing an example of a hollow structure film 1 of Variation 7 observed from the thickness direction of the hollow structure film 1, and corresponds to Figure 2. 2, showing one of a pair of bases 10 (first base 11) in an example of a hollow structure film 1, as viewed from the thickness direction of the hollow structure film 1. As shown in FIG. 21A, the connection portion 24 and the support portion 20 do not have to extend from the first end 1d to the second end 1e. In the example shown in FIG. 21A, the connection portion 24 and the support portion 20 are not located at the first end 1d. Furthermore, in the example shown in FIG. 21A, the connection portion 24 and the support portion 20 are not located at the second end 1e.

[0199] 21B is a perspective view showing a single-sided shaped object 80 used in the production of the hollow structure film 1 shown in FIG. 21A. In the figures showing the single-sided shaped object 80, including FIG. 21B, the direction that becomes the first direction d1 when the hollow structure film 1 is produced using the single-sided shaped object 80 is shown as the first direction d1. Furthermore, the direction that becomes the second direction d2 when the hollow structure film 1 is produced using the single-sided shaped object 80 is shown as the second direction d2. The hollow structure film 1 shown in FIG. 21A can be produced using the single-sided shaped object 80 shown in FIG. 21B. The single-sided shaped object 80 has a first end 801 and a second end 802 as ends in the first direction d1. In the example shown in FIG. 21B, the convex portion 82 does not extend from the first end 801 to the second end 802. In the example shown in FIG. 21B, the convex portion 82 is not located at the first end 801. Furthermore, in the example shown in FIG. 21B, the protrusion 82 is not located at the second end 802.

[0200] In the example shown in Figure 9 above, the hollow structure film 1 has a third end 1f and a fourth end 1g as ends in the third direction d3. In the example shown in Figure 9 above, the base 10 has a plurality of connection portions 24, including a first connection portion 24a extending in the first direction d1 and a second connection portion 24b extending in the third direction d3. Furthermore, in the example shown in Figure 9 above, the hollow structure film 1 has a plurality of support portions 20 extending in the first direction d1 and a plurality of support portions 20 extending in the third direction d3. In the example shown in Figure 9 above, the first connection portion 24a and the support portions 20 extending in the first direction d1 extend from the first end 1d to the second end 1e. In the example shown in Figure 9 above, the second connection portion 24b and the support portions 20 extending in the third direction d3 extend from the third end 1f to the fourth end 1g. However, for a hollow structure film 1 in which the base 10 has a first connecting portion 24a and a second connecting portion 24b, and which includes a support portion 20 extending in the first direction d1 and a support portion 20 extending in the third direction d3, the shapes of the connecting portion 24 and the support portion 20 are not limited to this. Figures 22A, 22B, and 22C are plan views showing an example of a hollow structure film 1 of Variation 7 as viewed from the thickness direction of the hollow structure film 1, and correspond to Figure 2. As shown in Figures 22A, 22B, and 22C, the first connecting portion 24a and the support portion 20 extending in the first direction d1 do not have to extend from the first end 1d to the second end 1e. As shown in Figures 22A, 22B, and 22C, the second connecting portion 24b and the support portion 20 extending in the third direction d3 do not have to extend from the third end 1f to the fourth end 1g. In the example shown in Figures 22A, 22B, and 22C, the connecting portion 24 and the support portion 20 are not located at the first end 1d. In the example shown in Figures 22A, 22B, and 22C, the connecting portion 24 and the support portion 20 are not located at the second end 1e. In the example shown in Figures 22A, 22B, and 22C, the connecting portion 24 and the support portion 20 are not located at the third end 1f. Furthermore, in the example shown in Figures 22A, 22B, and 22C, the connecting portion 24 and the support portion 20 are not located at the fourth end 1g.

[0201] 22A, the first connecting portion 24a and the second connecting portion 24b may be spaced apart from each other. The support portion 20 extending in the first direction d1 and the support portion 20 extending in the third direction d3 may be spaced apart from each other.

[0202] As shown in Figures 22B and 22C, the first connection portion 24a and the second connection portion 24b may be connected to each other. The support portion 20 extending in the first direction d1 and the support portion 20 extending in the third direction d3 may be connected to each other. In this case, as shown in Figure 22B, the first connection portion 24a and the second connection portion 24b may be connected to each other to form a "+" shape. The support portion 20 extending in the first direction d1 and the support portion 20 extending in the third direction d3 may be connected to each other to form a "+" shape. As shown in Figure 22C, the first connection portion 24a and the second connection portion 24b may be connected to each other to form an L-shape. The support portion 20 extending in the first direction d1 and the support portion 20 extending in the third direction d3 may be connected to each other to form an L-shape.

[0203] The hollow structure films 1 shown in Figures 22A, 22B, and 22C can be manufactured using single-sided shaped objects 80 having corresponding shapes. As an example, the single-sided shaped object 80 used to manufacture the hollow structure film 1 shown in Figure 22A will be described. Figure 22D is a perspective view showing the single-sided shaped object 80 used to manufacture the hollow structure film 1 shown in Figure 22A. In Figure 22D, the direction that becomes the third direction d3 when the hollow structure film 1 is manufactured using the single-sided shaped object 80 is shown as the third direction d3. The single-sided shaped object 80 has a first end 801 and a second end 802 as ends in the first direction d1. The single-sided shaped object 80 has a third end 803 and a fourth end 804 as ends in the third direction d3. In the example shown in FIG. 22D , the single-sided shaped object 80 includes, as the convex portions 82, convex portions 82 extending in the first direction d1 and convex portions 82 extending in the third direction d3. In the example shown in FIG. 22D , the convex portions 82 extending in the first direction d1 do not extend from the first end 801 to the second end 802. In the example shown in FIG. 22D , the convex portions 82 extending in the third direction d3 do not extend from the third end 803 to the fourth end 804. In the example shown in FIG. 22D , the convex portions 82 are not located at the first end 801. In the example shown in FIG. 22D , the convex portions 82 are not located at the second end 802. In the example shown in FIG. 22D , the convex portions 82 are not located at the third end 803. Furthermore, in the example shown in FIG. 22D , the convex portions 82 are not located at the fourth end 804.

[0204] The hollow structure film 1 of the seventh modification also allows a hollow structure to be formed, thereby keeping the dielectric constant low.

[0205] <Modification 8> The shapes of the connection portions 24 and the support portions 20 are not limited to the examples described in the above-described embodiment and each modification. The contour shapes of the connection portions 24 and the support portions 20 observed in the thickness direction of the hollow structure film 1 may be shapes other than rectangular having short and long sides. Figures 23A, 23B, and 23C are plan views showing an example of the hollow structure film 1 of Modification 8 observed in the thickness direction of the hollow structure film 1, and correspond to Figure 2. In the example shown in Figure 23A, the contour shapes of the connection portions 24 and the support portions 20 observed in the thickness direction of the hollow structure film 1 are square. In the examples shown in Figures 23B and 23C, the contour shapes of the connection portions 24 and the support portions 20 observed in the thickness direction of the hollow structure film 1 are circular. Although not shown, the contour shapes of the connection portions 24 and the support portions 20 observed in the thickness direction of the hollow structure film 1 may be elliptical. In the hollow structure film 1, the connection portions 24 and the support portions 20 do not have to extend in the first direction d1.

[0206] Furthermore, the method of arranging the connection portions 24 and the support portions 20 is not particularly limited as long as it is possible to form a continuous support portion 23. In the examples shown in Figures 23A, 23B, and 23C, the connection portions 24 and the support portions 20 are arranged regularly. In the examples shown in Figures 23A, 23B, and 23C, the connection portions 24 and the support portions 20 are arranged at equal intervals. Although not shown, the connection portions 24 and the support portions 20 may also be arranged randomly. The hollow structure film 1 may have an area where the connection portions 24 and the support portions 20 are arranged regularly and an area where the connection portions 24 and the support portions 20 are arranged randomly.

[0207] 23A and 23B, the connecting portions 24 and the support portions 20 may be arranged along a fourth direction d4, which is the direction in which one of the end sides 1h of the hollow structure film 1 extends, and a fifth direction d5 intersecting the fourth direction d4. In the example shown in FIGS. 23A and 23B, the fourth direction d4 and the fifth direction d5 are perpendicular to each other.

[0208] As shown in Fig. 23C, the connecting portions 24 and the support portions 20 may be arranged along a sixth direction d6 and a seventh direction d7 intersecting the sixth direction d6. The sixth direction d6 is a direction non-parallel to the extension direction of the end side 1h of the hollow structure film 1. The seventh direction d7 is a direction non-parallel to the extension direction of the end side 1h of the hollow structure film 1 and non-parallel to the sixth direction d6. In the example shown in Fig. 23C, the sixth direction d6 and the seventh direction d7 are perpendicular to each other.

[0209] The hollow structure films 1 shown in Figures 23A, 23B, and 23C can be manufactured using single-sided shaped objects 80 having corresponding shapes. Figure 22D is a perspective view showing a single-sided shaped object 80 used to manufacture the hollow structure film 1 shown in Figure 23A. Figure 23E is a perspective view showing a single-sided shaped object 80 used to manufacture the hollow structure film 1 shown in Figure 23B. Figure 23F is a perspective view showing a single-sided shaped object 80 used to manufacture the hollow structure film 1 shown in Figure 23C. In the example shown in Figure 23D, the convex portion 82 has the shape of a truncated square pyramid, particularly a regular truncated square pyramid. In the examples shown in Figures 23E and 23F, the convex portion 82 has the shape of a truncated cone.

[0210] 23D and 23E, the protrusions 82 are arranged along an eighth direction d8, which is the direction in which one of the end sides 805 of the single-sided object 80 extends, and a ninth direction d9 that intersects with the eighth direction d8. In the example shown in FIG. 23D and 23E, the eighth direction d8 and the ninth direction d9 are perpendicular to each other.

[0211] In the example shown in Figure 23F, the convex portions 82 are arranged along a tenth direction d10 and an eleventh direction d11 that intersects with the tenth direction d10. The tenth direction d10 is a direction non-parallel to the extension direction of the end edge 805 of the single-sided shaped object 80. The eleventh direction d11 is a direction non-parallel to the extension direction of the end edge 805 of the single-sided shaped object 80 and non-parallel to the tenth direction d10. In the example shown in Figure 23F, the tenth direction d10 and the eleventh direction d11 are perpendicular to each other.

[0212] The hollow structure film 1 of the eighth modification also allows a hollow structure to be formed, thereby keeping the dielectric constant low.

[0213] Next, specific examples of the above-described embodiment and each of the modifications will be described.

[0214] Example 1 A hollow structure film 1 similar to the hollow structure film 1 shown in FIG. 1 was produced except that it did not contain particles 50. First, a pair of single-sided shaped bodies 80 was produced using a mold 90. Kapton (registered trademark) manufactured by DuPont-Toray Co., Ltd. was prepared as a peelable substrate. Furthermore, a mixture of resin and an electron beam crosslinking agent was prepared as the material for the shaped body corresponding portion 13. High-density polyethylene raw material pellets (product name "Hi-Zex (registered trademark) 5000SR" manufactured by Prime Polymer Co., Ltd.) were used as the resin. TAIC (registered trademark) (manufactured by Shinryo Corporation) was used as the electron beam crosslinking agent. The mass ratio of the resin to the total mass of the mixture was 95% by mass. The mass ratio of the electron beam crosslinking agent to the total mass of the mixture was 5% by mass.

[0215] Next, a mold 90 having a surface 90a shaped to correspond to the shape of the single-sided shaped object 80 to be produced was used to mold the material of the shaped object corresponding portion 13 onto a peelable substrate. In this way, a pair of single-sided shaped objects 80 was produced from the material of the shaped object corresponding portion 13. The produced pair of single-sided shaped objects 80 had a sheet-like base 81 and a plurality of convex portions 82 formed on one side of the base 81. The thickness of the single-sided shaped object 80 (the sum of the thickness of the base 81 and the dimensions of the convex portions 82 in the thickness direction of the base 81) was 150 μm.

[0216] Furthermore, a resin sheet 32 ​​was prepared as the material for the central portion 30. The resin sheet 32 ​​was prepared by dispersing an electron beam crosslinking agent in a resin and molding it into a sheet. The resin material contained in the resin sheet 32 ​​was linear low-density polyethylene raw material pellets (product name "DOWLEX (registered trademark): 2045.11G (C8 copolymer)", manufactured by Dow Chemical Company). The electron beam crosslinking agent contained in the resin sheet 32 ​​was the same as the electron beam crosslinking agent contained in the shaped object corresponding portion 13. The ratio of the mass of the resin to the total mass of the resin and the electron beam crosslinking agent was 95% by mass. The ratio of the mass of the electron beam crosslinking agent to the total mass of the resin and the electron beam crosslinking agent was 5% by mass. The thickness of the resin sheet 32 ​​was 50 μm.

[0217] Next, a pair of laminates including the single-sided shaped object 80 and the peelable substrate were overlapped so that the plurality of protrusions 82 of the pair of single-sided shaped objects 80 partially faced each other. As a result, the pair of single-sided shaped objects 80 were overlapped so that the plurality of protrusions 82 partially faced each other. At this time, a resin sheet 32 ​​was placed between the pair of single-sided shaped objects 80.

[0218] Next, the pair of single-sided shaped objects 80 were heat-pressed together. In particular, by heat-pressing the pair of single-sided shaped objects 80, the pair of single-sided shaped objects 80 were bonded to the resin sheet 32 ​​at the multiple protrusions 82. In this way, the pair of single-sided shaped objects 80 were bonded via the resin sheet 32. The heating temperature when heat-pressing the pair of single-sided shaped objects 80 was set to be higher than the Vicat softening point of the resin contained in the central portion 30.

[0219] Next, the releasable substrate was peeled off from the pair of single-sided shaped bodies 80 .

[0220] Next, a crosslinking process was carried out in which the electron beam crosslinking agent contained in the single-sided shaped object 80 was irradiated with an electron beam to react with the resin. The electron beam irradiated had an acceleration voltage of 200 kV, a current value of 5 mA, and an exposure dose of 289 kGy. Furthermore, in the crosslinking process, the electron beam crosslinking agent contained in the resin sheet 32 ​​was irradiated with an electron beam to react with the resin. More specifically, in the crosslinking process, the electron beam crosslinking agent contained in the single-sided shaped object 80 and the electron beam crosslinking agent contained in the resin sheet 32 ​​were simultaneously irradiated with an electron beam to react with the resin simultaneously in the single-sided shaped object 80 and the resin sheet 32. This produced the hollow structure film 1 shown in FIG. 1. The ratio of the width w2 to the spacing w1 of the hollow structure film 1 shown in FIG. 1 was 1:3.

[0221] (Example 2) A hollow structure film 1 was produced in the same manner as in Example 1, except for the following points: The thickness of the single-sided shaped body 80 (the sum of the thickness of the base 81 and the dimension of the protrusion 82 in the thickness direction of the base 81) was 120 μm.

[0222] Example 3 A hollow structure film 1 was manufactured using the same method as in Example 1, except for the following points. As shown in Figure 9, a hollow structure film 1 was manufactured in which the base 10 had multiple connection portions 24, including first connection portions 24a extending in the first direction d1 and second connection portions 24b extending in the third direction d3. The third direction d3 in which the second connection portions 24b extended was perpendicular to the first direction d1 in which the first connection portions 24a extended. The ratio of the width w2 to the spacing w1 of the hollow structure film 1 was 1:10.

[0223] Example 4 A hollow structure film 1 was produced using the same method as in Example 1, except for the following points. One of a pair of single-sided shaped bodies 80 was produced as follows. Using a mold 90, the material of the metal-adjacent layer 60 and the material of the shaped body corresponding portion 13 were molded in this order on a peelable substrate by co-extrusion molding. The material of the metal-adjacent layer 60 was an ethylene-methacrylic acid copolymer (product name "Nucrel (registered trademark) AN4233C", manufactured by Mitsui Dow Polychemical Co., Ltd.). The thickness of the metal-adjacent layer 60 was 30 μm. In this way, the metal-adjacent layer 60 was produced on the peelable substrate from the material of the metal-adjacent layer 60, and the single-sided shaped body 80 was produced on the metal-adjacent layer 60 from the material of the shaped body corresponding portion 13. In this way, a laminate was produced in which the peelable substrate, the metal-adjacent layer 60, and the single-sided shaped body 80 were laminated in this order. The laminate produced as described above and a laminate including a single-sided shaped body 80 and a peelable substrate produced by the same method as in Example 1 were overlapped so that the multiple convex portions 82 of the pair of single-sided shaped bodies 80 partially faced each other. As a result, the pair of single-sided shaped bodies 80 were overlapped so that the multiple convex portions 82 partially faced each other. Next, the pair of single-sided shaped bodies 80 were heat-pressed together. Next, the peelable substrate was peeled from the single-sided shaped body 80 and the metal adjacent layer 60. In this way, a hollow structure film 1 was produced, which corresponds to the hollow structure film 1 shown in Figure 1 in which the metal adjacent layer 60 is provided on one side of the pair of bases 10.

[0224] Example 5 A hollow structure film 1 was produced in the same manner as in Example 1, except for the following points. A mixture of resin and an electron beam crosslinking agent was prepared as the material for the shaped body corresponding portion 13. Linear low-density polyethylene raw material pellets (product name "DOWLEX (registered trademark): 2045.11G (C8 copolymer)", manufactured by Dow Chemical Co.) were used as the resin contained in the mixture. The mass ratio of the resin to the total mass of the mixture was 95 mass%. The mass ratio of the electron beam crosslinking agent to the total mass of the mixture was 5 mass%. A sheet made of ethylene-methacrylic acid copolymer (product name "Nucrel (registered trademark) AN4233C", manufactured by Dow Mitsui Polychemical Co., Ltd.) was used as the resin sheet 32. The resin sheet 32 ​​did not contain particles 50 or an electron beam crosslinking agent.

[0225] Example 6 A hollow structure film 1 was produced using the same method as in Example 1, except for the following points. A mixture of resin, particles 50, and an electron beam crosslinking agent was prepared as the material for the shaped body corresponding portion 13. The resin contained in the mixture was linear low-density polyethylene raw material pellets (product name "DOWLEX (registered trademark): 2045.11G (C8 copolymer)", manufactured by Dow Chemical Company). The particles 50 contained in the mixture were hollow glass particles (glass particles 51 having hollow portions 52, product name "Sphericel (registered trademark) 25P45", manufactured by Potters Ballotini). The mass ratio of the resin to the total mass of the mixture was 85% by mass. The mass ratio of the particles 50 to the total mass of the mixture was 10% by mass. The mass ratio of the electron beam crosslinking agent to the total mass of the mixture was 5% by mass. A sheet made of ethylene-methacrylic acid copolymer (product name "Nucrel (registered trademark) AN4233C", manufactured by Dow Mitsui Polychemicals Co., Ltd.) was used as the resin sheet 32. The resin sheet 32 ​​did not contain particles 50 or an electron beam crosslinking agent.

[0226] Example 7 A hollow structure film 1 was produced using the same method as in Example 1, except for the following points. A mixture of resin, particles 50, and an electron beam crosslinking agent was prepared as the material for the shaped body corresponding portion 13. The resin contained in the mixture was linear low-density polyethylene raw material pellets (product name "DOWLEX (registered trademark): 2045.11G (C8 copolymer)", manufactured by Dow Chemical Company). The particles 50 contained in the mixture were hollow glass particles (glass particles 51 having hollow portions 52, product name "Sphericel (registered trademark) 25P45", manufactured by Potters Ballotini). The mass ratio of the resin to the total mass of the mixture was 75% by mass. The mass ratio of the particles 50 to the total mass of the mixture was 10% by mass. The mass ratio of the electron beam crosslinking agent to the total mass of the mixture was 15% by mass. A sheet made of ethylene-methacrylic acid copolymer (product name "Nucrel (registered trademark) AN4233C", manufactured by Dow Mitsui Polychemicals Co., Ltd.) was used as the resin sheet 32. The resin sheet 32 ​​did not contain particles 50 or an electron beam crosslinking agent.

[0227] (Example 8) A hollow structure film 1 was produced using the same method as in Example 1, except for the following points. Only one laminate including a single-sided shaped object 80 and a peelable substrate was produced. Furthermore, only one laminate including a resin sheet 32 ​​and a peelable substrate was produced. A laminate including a single-sided shaped object 80 and a laminate including a resin sheet 32 ​​were arranged so that the resin sheet 32 ​​faced the surface of the single-sided shaped object 80 on which multiple protrusions 82 were formed. Next, the two layers of the single-sided shaped object 80 and the resin sheet 32 ​​were heat-welded by hot pressing. Next, the peelable substrate was peeled off from the single-sided shaped object 80 and the resin sheet 32. As a result of the above, a hollow structure film 1 equivalent to the hollow structure film 1 shown in Figure 14 from which the metal layer 40 and the metal adjacent layer 60 were removed was produced.

[0228] (Example 9) A hollow structure film 1 was produced using the same method as in Example 1, except for the following points. Four single-sided shaped bodies 80 were produced: a first single-sided shaped body 80a, a second single-sided shaped body 80b, a third single-sided shaped body 80c, and a fourth single-sided shaped body 80d. Furthermore, three resin sheets 32 were produced. Next, the first single-sided shaped body 80a, the resin sheet 32, the second single-sided shaped body 80b, the resin sheet 32, the third single-sided shaped body 80c, the resin sheet 32, and the fourth single-sided shaped body 80d were stacked in this order and heat-sealed. That is, four single-sided shaped bodies 80 and three resin sheets 32 were stacked and heat-sealed as shown in FIG. 15. At this time, the surfaces of the first single-sided shaped body 80a and the second single-sided shaped body 80b on which the multiple convex portions 82 were formed were placed face to face. The surfaces of the second single-sided shaped body 80b and the third single-sided shaped body 80c, each formed by the base 81, were placed face to face. The surfaces of the third single-sided shaped body 80c and the fourth single-sided shaped body 80d on which the multiple convex portions 82 were formed were placed face to face. By stacking and heat-welding four single-sided shaped bodies 80 and three resin sheets 32 as described above, a hollow structure film 1 equivalent to the hollow structure film 1 shown in FIG. 16 from which the metal layer 40 and the metal adjacent layer 60 were removed was produced. In the crosslinking step, an electron beam was irradiated from the side of the first single-sided shaped object 80a at a dose of 289 kGy, and also from the side of the fourth single-sided shaped object 80d at a dose of 289 kGy.

[0229] Comparative Example 1 A commercially available polyimide film (product name "Upilex 125S", manufactured by UBE Corporation) was used as the film of Comparative Example 1. The thickness of the film of Comparative Example 1 was 125 μm.

[0230] Comparative Example 2 A commercially available liquid crystal polymer (product name "R-F705", manufactured by Panasonic Industries Co., Ltd.) was used as a film of Comparative Example 2. The thickness of the film of Comparative Example 2 was 100 μm.

[0231] (Comparative Example 3) High-density polyethylene raw material pellets (product name "Hi-Zex (registered trademark) 5000SR", manufactured by Prime Polymer Co., Ltd.) were hot-pressed with a gap of 200 μm. This produced a smooth film-like sample. This sample was designated the film of Comparative Example 3. Because the gap during hot-pressing was set to 200 μm, the thickness of the film of Comparative Example 3 was 200 μm.

[0232] (1) Porosity Measurement Test Next, a porosity measurement test was performed on the hollow structure films 1 of Examples 1 to 9. In the porosity measurement test, an image of a cross section of the hollow structure film 1 cut along a plane passing through the multiple support sections 20 and perpendicular to the first direction d1 was obtained using a scanning electron microscope (SEM). The above-mentioned lines L2 and L3 were drawn on the obtained image. Next, the ratio of the area of ​​the hollow section B to the area of ​​the entire hollow structure film 1 including the hollow section B between lines L2 and L3 was calculated. This ratio was calculated at 10 different points on the cross section. The ratios calculated at the 10 different points were averaged to obtain the porosity of the hollow structure film 1. The porosity of Comparative Examples 1 to 3, which do not have hollow sections B to begin with, was set to 0.

[0233] (2) Specific Gravity Measurement Test Next, a specific gravity measurement test (the ratio of the density of the object to the density of water at standard atmospheric pressure) was conducted on the hollow structure films 1 of Examples 1 to 9 and the films of Comparative Examples 1 to 3. In the specific gravity measurement test, square samples with sides of 100 mm were cut out from the hollow structure films 1 of each Example and each Comparative Example. Next, the mass of the samples was measured. Furthermore, the thickness of the samples was measured. The sample thickness was measured using the following method. Using an apparatus combining a Nikon Digimicrohead MF-501 and a counter MFC-200, the thickness was measured at 16 points on the surface of the sample on a surface plate. Each measurement point was spaced 3 cm apart. The average of the thicknesses at the 16 points on the surface was taken as the thickness of the sample. The volume of the sample was calculated by multiplying the square of the length of one side of the sample (100 mm) by the thickness. The specific gravity of the hollow structure films 1 of each Example and Comparative Example was calculated from the measured mass and calculated volume.

[0234] (3) Measurement Test of Dielectric Constant and Dielectric Loss Tangent Next, measurements of the dielectric constant and dielectric loss tangent were performed on the hollow structure films 1 of Examples 1 to 9 and the films of Comparative Examples 1 to 3. In the measurement tests of the dielectric constant and dielectric loss tangent, a cavity resonance measurement device (product name "S-Parameter Network Analyzer 8722ES" manufactured by Agilent Technologies Inc.), a cavity resonator, and the program CPMA-V2 installed on a notebook PC were used to measure the dielectric constant and dielectric loss tangent according to the following method. From the hollow structure film 1 of each Example and the film of each Comparative Example, rectangular samples with short sides of 2 mm and long sides of 100 mm were cut out. Next, the measurement device was started up. The sample was then inserted into the cavity of the cavity resonator of the measurement device from one of the short sides, and the dielectric constant and dielectric loss tangent of the sample were measured. The dielectric constant and dielectric loss tangent of the same sample were measured three times, and the average values ​​of the three measurement results were used as the measured values ​​of the dielectric constant and dielectric loss tangent. Furthermore, as a value serving as an index for comparing the magnitude of transmission loss (also referred to as "transmission loss coefficient"), the product of the square root of the relative dielectric constant calculated from the measured dielectric constant and the measured dielectric loss tangent was calculated.

[0235] (4) Heat Resistance Evaluation Test Next, a heat resistance evaluation test was conducted on the hollow structure films 1 of Examples 1 to 9 and the films of Comparative Examples 1 to 3. In the heat resistance evaluation test, rectangular samples with long sides of 20 mm and short sides of 2 mm were cut out from the hollow structure films 1 of each Example and each Comparative Example. The samples were placed on a glass substrate so that only the long sides of 10 mm rested on the glass substrate, and fixed to the glass substrate using tape (product name "Kapton (registered trademark) Adhesive Tape #12", manufactured by Teraoka Seisakusho Co., Ltd.). Next, the samples, while fixed to the glass substrate, were heated by placing them in an oven heated to 290°C for 90 seconds. At this time, the sample was positioned above the surface of the glass substrate. Next, the heated samples were visually observed to evaluate whether the samples had deformed after heating and the degree of deformation after heating. If no deformation was observed, the sample was rated as "○", if slight deformation (such as warping of the sample, in which the portion of the sample protruding from the glass substrate did not sag and break, and the portion of the sample fixed to the glass substrate and the portion protruding from the glass substrate remained connected) was rated as "△", and if severe deformation (such as the portion of the sample protruding from the glass substrate completely sagging, causing the sample to break between the portion fixed to the glass substrate and the portion protruding from the glass substrate) was observed, the sample was rated as "×".

[0236] (5) Copper Foil Adhesion Evaluation Test Next, a copper foil adhesion evaluation test was conducted on the hollow structure films 1 of Examples 1 to 9 and the films of Comparative Examples 1 to 3. In the copper foil adhesion evaluation test, the resistance of the copper foil to load was evaluated using the following method. Rectangular samples with long sides of 100 mm and short sides of 20 mm were cut out from the hollow structure films 1 of each Example and each Comparative Example. The samples were placed on copper foil (10 μm thick, product name "CF-LB9-10", purchased from Hohsen Co., Ltd.). The copper foil was the same size as the sample. That is, the copper foil used had a rectangular shape with long sides of 100 mm and short sides of 20 mm. The copper foil and the sample were placed on the copper foil so that the long side direction of the copper foil and the long side direction of the sample were aligned and the long side of the sample was placed on the copper foil by 20 mm. Furthermore, a metal adjacent layer material (30 μm thick, product name "Nucrel (registered trademark) AN4233C", manufactured by Mitsui Dow Polychemicals Co., Ltd.) was placed between the sample and the copper foil. Subsequently, the overlapping portions of the sample, metal adjacent layer material, and copper foil were heated and pressed at 100 ° C. The pressed portion was formed at the end of the sample. In the pressed portion, a laminate was formed in which the sample, metal adjacent layer, and copper foil were laminated in this order. The portion of the sample not pressed against the copper foil and the portion of the copper foil not pressed against the sample were formed over a length of 80 mm in the long side direction of the sample and copper foil. In this way, the sample was joined to the copper foil. Subsequently, the adhesion of the copper foil was evaluated by the following method. As a test device, a Force Tester MCT-2150 manufactured by A&D Co., Ltd. was prepared, with a pair of parallel clamping jaws for 500N set up in the vertical direction. Next, the portion of the sample that was not crimped against the copper foil was set in one chuck of a pair of parallel clamping jaws. Furthermore, the portion of the copper foil that was not crimped against the sample was set in one chuck of a pair of parallel clamping jaws. Next, one of the pair of parallel clamping jaws was separated from the other at a speed of 5 N / min, thereby applying a load to the bonding surface where the sample and the copper foil were bonded, and it was observed whether peeling occurred at the bonding surface between the sample and the copper foil.Furthermore, if peeling occurred, the peel force (the load applied to the bonding surface between the sample and the copper foil when peeling occurred) was measured. If no peeling occurred or if the peel force when peeling occurred was greater than 10 N / 20 mm, the sample was evaluated as "Good." If the peel force when peeling occurred was 10 N / 20 mm or less, the sample was evaluated as "Poor."

[0237] In addition, in the copper foil adhesion evaluation test, an etchant resistance evaluation test was performed using the following method. A laminate was formed by laminating a sample, a metal adjacent layer, and a copper foil in this order using the same method as in the copper foil load resistance evaluation test, except that a sample, a metal adjacent layer, and a copper foil large enough to allow the step of cutting out a laminate sample described below was used. That is, similar to the copper foil load resistance evaluation test, the metal adjacent layer was placed between the sample and the copper foil and then heated and pressed to form the laminate. A square laminate sample with a side length of 20 mm was cut out from the portion of this laminate where the sample and the copper foil were thermally welded via the metal adjacent layer. A square masking tape with a side length of 5 mm (product name "ELEP MASKING N-300", manufactured by Nitto Denko Corporation) was attached to the center of the copper foil surface of the laminate sample. The laminate sample was then placed in a 1 L glass beaker containing an aqueous iron chloride solution (40% concentration, 42 Baume scale at 15°C, manufactured by Wako Pure Chemical Industries, Ltd.) heated to 50°C, and subjected to a 5-minute etching treatment. The laminate sample was then washed twice with distilled water at room temperature for 1 minute. The laminate sample was then dried. The masking tape was then peeled off from the laminate sample, and the state of the copper foil remaining unetched beneath the masking tape was observed. After the masking tape was peeled off, the copper foil was evaluated as "good" if it remained in the shape of a square with sides of 5 mm and there was no visible peeling or lifting of the copper foil. The evaluation was then evaluated as "poor" if there was visible lifting at the edge of the copper foil or peeling of the copper foil.

[0238] (6) Dynamic Viscoelasticity Evaluation Test Next, a dynamic viscoelasticity evaluation test was conducted on the hollow structure films 1 of Examples 1 to 9 and the films of Comparative Examples 1 to 3 when the sample temperature was elevated. For the dynamic viscoelasticity evaluation test, a dynamic viscoelasticity (DMA) measuring device (product name "RSA-G2") manufactured by TA Instruments Japan, Inc. was prepared. The dynamic viscoelasticity measuring device was set in tension mode. Rectangular samples with short sides of 5 mm were cut out from the hollow structure films 1 of each Example and each Comparative Example. Next, the pair of chucks of the dynamic viscoelasticity measuring device were spaced 10 mm apart. One short side of the sample was set in one of the pair of chucks, and the other short side of the sample was set in the other of the pair of chucks. Next, the dynamic viscoelasticity was measured while the sample temperature was changed from 30°C to 300°C. The temperature increase rate was 5°C / min. In the measurement of dynamic viscoelasticity, a time-varying stress was applied to the sample, and the frequency of the stress change was set to 1 Hz, thereby measuring the storage modulus of the sample, particularly when the sample temperature was 280°C.

[0239] The results of the porosity measurement test, the specific gravity measurement test, the dielectric constant and dielectric loss tangent measurement test, the heat resistance evaluation test, the copper foil adhesion evaluation test, and the dynamic viscoelasticity evaluation test for the hollow structure films 1 of Examples 1 to 9 are shown in Table 1. Additionally, the results of the specific gravity measurement test, the dielectric constant and dielectric loss tangent measurement test, the heat resistance evaluation test, the copper foil adhesion evaluation test, and the dynamic viscoelasticity evaluation test for the films of Comparative Examples 1 to 3 are shown in Table 1.

[0240]

[0241] From the results shown in Table 1, it was found that all of Examples 1 to 9 had smaller dielectric constants, dielectric loss tangents, and transmission loss coefficients than Comparative Examples 1 to 3. Furthermore, it was found that all of Examples 1 to 9 were evaluated as "good" in terms of heat resistance, resistance to load on the copper foil, and etchant resistance. Furthermore, all of Examples 1 to 9 had a storage modulus of 1.0 × 10 5 It was found that the temperature was 1000 Pa or higher.

[0242] Furthermore, in order to evaluate the performance of the antenna equipment 101 manufactured using the hollow structure film 1 and the transmission loss in the hollow structure film 1, hollow structure films 1 of Examples 10 to 11 and films of Comparative Examples 4 to 6 were prepared.

[0243] Example 10 A hollow structure film 1 having a main body 1c as shown in FIG. 16 was manufactured using the same method as in Example 9, except for the following points. The thickness of the main body 1c was 800 μm. Furthermore, two sheets of copper foil (thickness 18 μm, product name "C1100 Electrolytic Copper Foil 18 μm", purchased from Hosen Co., Ltd.) and two sheets of metal adjacent layer material (thickness 30 μm, product name "Nucrel (registered trademark) AN4233C", manufactured by Dow Mitsui Polychemical Co., Ltd.) were prepared. The copper foil, metal adjacent layer material, main body 1c, metal adjacent layer material, and copper foil were then stacked in this order. The copper foil, metal adjacent layer material, main body 1c, metal adjacent layer material, and copper foil were then heat-pressed together at 100°C. This resulted in the production of a hollow structure film 1 having, in this order, a metal layer 40 formed from copper foil, a metal adjacent layer 60, a main body portion 1c, a metal adjacent layer 60, and a metal layer 40 formed from copper foil, as shown in Figure 16.

[0244] (Example 11) A hollow structure film 1 was produced using the same method as in Example 10, except for the following points. A hollow structure film 1 having a configuration corresponding to Modification Example 4 was produced. More specifically, a hollow structure film 1 as shown in Figure 14 was produced. First, one single-sided shaped body 80 and one resin sheet 32 ​​were produced using the same method as in Example 10. The thickness of the single-sided shaped body 80 (the sum of the thickness of the base 81 and the dimensions of the convex portions 82 in the thickness direction of the base 81) was 150 μm. The thickness of the resin sheet 32 ​​was 50 μm. Next, the resin sheet 32 ​​was placed so as to face the surface of the single-sided shaped body 80 on which the multiple convex portions 82 were formed. The single-sided shaped body 80 and the resin sheet 32 ​​were heat-pressed together. In the crosslinking process after thermocompression bonding, the single-sided shaped body 80 and the resin sheet 32 ​​were irradiated with an electron beam at an acceleration voltage of 200 kV, a current value of 5 mA, and an exposure dose of 289 kGy. This produced the main body portion 1c of the hollow structure film 1 shown in FIG. 14 . Furthermore, two copper foils (thickness 18 μm, product name "C1100 Electrolytic Copper Foil 18 μm", purchased from Hohsen Co., Ltd.) were prepared. Next, an olefin resin adhesive was applied to one side of each of the two copper foils. The amount of adhesive applied was adjusted so that the thickness of the adhesive after drying was 2 μm. Next, the main body portion 1c was placed between the two copper foils. At this time, the main body portion 1c was placed between the two copper foils so that the adhesive-coated side of the copper foil faced the surface of the main body portion 1c. The two copper foils and the main body portion 1c were then thermocompressed together at 100°C for 2 minutes. Furthermore, the hot-pressed copper foil and main body 1c were annealed by storing them in an oven at 80° C. for 36 hours, thereby producing a hollow structure film 1 having, in this order, a metal layer 40 formed from copper foil, a metal adjacent layer 60 formed from adhesive, the main body 1c, a metal adjacent layer 60 formed from adhesive, and a metal layer 40 formed from copper foil, as shown in FIG.

[0245] (Comparative Example 4) A commercially available PTFE substrate (product name "RO3003 (registered trademark)" manufactured by Rogers) was purchased and used as a film for Comparative Example 4. The thickness of the PTFE substrate was 800 μm. Copper foil with a thickness of 18 μm was provided on both sides of the PTFE substrate.

[0246] (Comparative Example 5) A commercially available glass epoxy resin film (product name "CS-3355W", manufactured by Risho Kogyo Co., Ltd.) was purchased and used as the film of Comparative Example 5. Copper foil with a thickness of 18 μm was provided on both sides of the glass epoxy resin film.

[0247] (Comparative Example 6) Two commercially available LCP films (product name "R-F705", manufactured by Panasonic Industries Co., Ltd.) were purchased. The thickness of the LCP film was 100 μm. A copper foil having a thickness of 18 μm was provided on one side of the LCP film. Furthermore, a commercially available bonding sheet (product name "R-BM17", manufactured by Panasonic Industries Co., Ltd.) was purchased. The thickness of the bonding sheet was 25 μm. Next, the bonding sheet was placed between the two LCP films. At this time, the bonding sheet was placed between the two LCP films so that the surface of the LCP film opposite the surface on which the copper foil was provided faced the surface of the bonding sheet. Next, the two LCP films and the bonding sheet were bonded together by bonding processing. In this way, the film of Comparative Example 6 was produced. The thickness of the film of Comparative Example 6 was 225 μm. On both sides of the film of Comparative Example 6, copper foil having a thickness of 18 μm was provided, which was derived from the copper foil provided on the LCP film.

[0248] (7) Antenna Performance Evaluation Test Next, antenna components 101 were fabricated from the films of Example 10 and Comparative Example 4, and antenna performance evaluation tests were performed on the fabricated antenna components 101. In fabricating the antenna components 101, a wiring pattern of the wiring 41 and an antenna element 102 of a desired shape were formed from the metal layer 40 constituting one surface of the hollow structure film 1 of each Example or the film of each Comparative Example, thereby fabricating the antenna components 101 as shown in FIG. 6C . The process of forming the wiring pattern of the wiring 41 and the antenna element 102 of a desired shape from the metal layer 40 was performed as follows. First, a weak adhesive sheet was attached to the surface of the metal layer 40. Next, the weak adhesive sheet was cut and removed, leaving a portion, to form a mask layer of a shape corresponding to the wiring pattern of the wiring 41 and the antenna element 102 to be formed. Next, the metal layer 40 was etched using the mask layer. This resulted in the fabrication of the antenna components 101 as shown in FIG. 6C . In Example 10, the dimension w7 (width of the wiring 41) of the wiring 41 shown in FIG. 6C was 3.2 mm. The dimension w8 (length of the wiring 41) of the wiring 41 shown in FIG. 6C was 17.0 mm. The dimension w9 of the antenna element 102 shown in FIG. 6C was 25.0 mm. The dimension w10 (length of the wiring 41) of the antenna element 102 shown in FIG. 6C was 30.0 mm. As shown in FIG. 6C, a pair of slit structures 102b was provided in the portion of the antenna element 102 connected to the wiring 41. The pair of slit structures 102b extended in the direction of extension of the wiring 41. A distance equal to the dimension w7 of the wiring 41 was provided between the pair of slit structures 102b. The dimension w13 (length of the slit structure 102b) of the slit structure 102b shown in FIG. 6C was 11.0 mm. The dimension w14 (width of the slit structure 102b) of the slit structure 102b shown in Figure 6C was set to 1.0 mm. In Comparative Example 4, the dimension w7 was 1.9 mm, the dimension w8 was 17.0 mm, the dimension w9 was 21.0 mm, the dimension w10 was 22.0 mm, the dimension w13 was 8.5 mm, and the dimension w14 was 1.0 mm. After determining the dimensions of the antenna equipment 101 of Example 10 and Comparative Example 4 as described above, a virtual antenna equipment was simulated in which the dimensions w7, w8, w9, w10, w13, w14, etc. were the same as those of the antenna equipment 101 of Example 10.Furthermore, a simulation was performed on a virtual antenna equipment having dimensions such as w7, w8, w9, w10, w13, and w14 that were the same as those of the antenna equipment of Comparative Example 4. Next, the S11 parameter (input reflection coefficient) was calculated when an electrical signal of 3.9 GHz frequency was applied to the antenna element of a virtual antenna equipment having dimensions the same as those of the antenna equipment 101 of Example 10 and a virtual antenna equipment having dimensions the same as those of the antenna equipment of Comparative Example 4. As a result, the S11 parameter of the virtual antenna equipment having dimensions the same as those of the antenna equipment 101 of Example 10 and the virtual antenna equipment having dimensions the same as those of the antenna equipment of Comparative Example 4 was -33.5 dB. From this, it was confirmed that the dimension settings of the antenna equipment 101 in Example 10 and Comparative Example 4 were appropriate settings for comparing the gain and beam width of the antenna equipment 101 between Example 10 and Comparative Example 4, as will be described later.

[0249] In the antenna performance evaluation test, a network analyzer was used to simulate a virtual antenna device that radiates radio waves with equal strength in all directions. The virtual antenna was assumed to be a point with no volume. The virtual antenna device, which is a point with no volume, was then placed on a rotating table 95, similar to the antenna device 101 shown in Figure 24 (described later), and the strength of the radio waves received by the receiving antenna 96 was calculated when a 3.9 GHz electrical signal was applied to the antenna element.

[0250] Furthermore, as shown in FIG. 24 , a turntable 95 rotatable about a rotation axis C1 extending vertically was placed in the anechoic chamber R. Furthermore, a receiving antenna 96 capable of receiving radio waves emitted by the antenna equipment 101 was placed in the anechoic chamber R at a position 3 m horizontally away from the rotation axis C1 of the turntable 95. Next, the fabricated antenna equipment 101 was fixed to a jig (not shown) and placed on the turntable 95 in the anechoic chamber R at a position along the rotation axis C1. At this time, the antenna equipment 101 was placed on the turntable 95 so that the side 102a of the antenna element 102 shown in FIG. 6C faced the receiving antenna 96. In other words, the antenna equipment 101 was placed on the turntable 95 so that the receiving antenna 96 was positioned in the direction of the arrow A1 of the antenna equipment 101 shown in FIG. 6C . The antenna equipment 101 was fixed to the jig so that the jig was electrically connected to the wiring 41.

[0251] Next, an electrical signal was applied from the network analyzer to the antenna element 102 of the antenna equipment 101 via a jig (not shown), causing the antenna element 102 to transmit radio waves. The frequency of the electrical signal applied to the antenna element 102 was set to 3.9 GHz. Next, the frequency of the electrical signal applied to the antenna element 102 was changed to identify the frequency at which the strength of the radio waves received by the receiving antenna 96 was maximized. The difference was calculated by subtracting the radio wave strength calculated as described above for the virtual antenna equipment, which is a point with no volume, from the value of the strength of the radio waves received by the receiving antenna 96 at the frequency at which the strength of the radio waves received by the receiving antenna 96 was maximized. This difference was used as the gain of the antenna equipment 101. The gain of the antenna equipment 101 calculated by the above calculation is expressed in dBi.

[0252] Furthermore, the antenna equipment 101 was rotated by rotating the rotating table while applying to the antenna element 102 an electrical signal of a frequency at which the strength of the radio waves received by the receiving antenna 96, as determined in calculating the gain, was maximized. When performing this operation, the strength of the radio waves received by the receiving antenna 96 is believed to be maximized when the side 102a of the antenna element 102 faces the receiving antenna 96, and to decrease as the rotation angle of the antenna equipment 101 from the position where the side 102a of the antenna element 102 faces the receiving antenna 96 increases. While rotating the antenna equipment 101, the strength of the radio waves detected by the receiving antenna 96 was measured. The difference was calculated by subtracting the radio wave strength calculated as described above for the virtual antenna equipment, which is a point with no volume, from the measured radio wave strength. It is believed that this difference value also changes as the rotation angle of the antenna equipment 101 changes. The magnitude of the change in rotation angle at which the decrease from the maximum value falls within a range of 3 dBi was calculated as the beam width (unit: °).

[0253] A method for calculating the beam width in one specific example will be described. In one specific example, when the antenna unit 101 is rotated clockwise by an angle of 30° or less from a position where the side 102a of the antenna element 102 faces the receiving antenna 96, the drop in the strength of the radio wave detected by the receiving antenna 96 from its maximum value becomes 3 dBi or less. In one specific example, when the antenna unit 101 is rotated counterclockwise by an angle of 30° or less from a position where the side 102a of the antenna element 102 faces the receiving antenna 96, the drop in the strength of the radio wave detected by the receiving antenna 96 from its maximum value becomes 3 dBi or less. In this case, the beam width is calculated to be 60°.

[0254] (8) Transmission Loss Evaluation Test Next, a transmission loss evaluation test was conducted on the films including the metal layer 40 of Example 11 and Comparative Examples 5 and 6. In the transmission loss evaluation test, a linear wiring 43 having a desired shape was first formed from the metal layer 40 constituting one surface of the hollow structure film 1 of each Example or the film of each Comparative Example, as shown in FIG. 6A . The method for forming the linear wiring 43 having a desired shape from the metal layer 40 was the same as the method for forming the wiring pattern of the wiring 41 having a desired shape and the antenna element 102 from the metal layer 40 described in "(7) Antenna Performance Evaluation Test." The length w5 of the linear wiring 43 shown in FIG. 6A was 5.0 cm. The width w6 of the linear wiring 43 shown in FIG. 6A was 0.75 mm.

[0255] As shown in FIG. 6B , the hollow structure film 1 including the linear wiring 43 was fixed to a jig 93 (product name: "Universal Test Fixture 3680V"), and an electrical signal was applied from a network analyzer (product name: "N5247A", manufactured by Keysight Technologies, Inc.) via a probe 94 attached to the jig 93 to measure the transmission loss of the electrical signal. The measurement of the transmission loss of the electrical signal was performed under the following conditions. The electrical signal was applied to a 5.0 cm section of the linear wiring 43. During the measurement, the de-embedding process described in the above embodiment was performed to remove the influence of the jig 93 from the measurement results. A value corresponding to the transmission loss measured by applying an electrical signal to a 3.5 cm section of the linear wiring 43, from which the influence of the transmission loss at both ends of the linear wiring 43 and at the jig 93 was removed by the de-embedding process, was calculated.

[0256] The results of the antenna performance evaluation test for the hollow structure film 1 of Example 10 and the film of Comparative Example 4, and the results of the transmission loss evaluation test for the hollow structure film 1 of Example 11 and the films of Comparative Examples 5 and 6 are shown in Table 2.

[0257]

[0258] The results of the antenna performance evaluation test and the transmission loss evaluation test revealed the following: The hollow structure film 1 of the present invention was found to exhibit superior performance compared to commercially available PTFE substrates, which are generally expected to have high antenna performance, and LCP films, which are generally expected to reduce transmission loss (bringing negative transmission loss values ​​closer to zero). In particular, the hollow structure film 1 of the present invention was found to be able to reduce transmission loss (bringing negative transmission loss values ​​closer to zero), which tends to be high and is a problem in antenna equipment 101 used in high-frequency bands. Furthermore, it was clearly shown that the antenna equipment 101 using the hollow structure film 1 of the present invention exhibits superior antenna performance compared to antenna equipment using conventional films, due to the effect of the hollow structure film 1 described above.

[0259] Furthermore, in order to evaluate the porosity, dielectric constant, dielectric tangent, CTE of the main body 1c of the hollow structure film 1 in which the main body 1c described above includes an inorganic material member 70 as variant example 6, and the ease with which the copper foil peels off from the main body 1c when the copper foil and the main body 1c are joined, hollow structure films 1 of Examples 12 to 14 and a film of Comparative Example 7 were prepared.

[0260] Example 12 A hollow structure film 1 similar to the hollow structure film 1 shown in FIG. 17 was manufactured. First, a pair of single-sided shaped bodies 80 was prepared using a mold 90. Kapton (registered trademark) manufactured by DuPont-Toray Co., Ltd. was prepared as a peelable substrate. Furthermore, a mixture of resin and an electron beam crosslinking agent was prepared as the material for the shaped body corresponding portion 13. High-density polyethylene raw material pellets (product name "Hi-Zex (registered trademark) 5000SR" manufactured by Prime Polymer Co., Ltd.) were used as the resin. This resin corresponds to high-density polyethylene (HDPE). TAIC (registered trademark) (manufactured by Shinryo Corporation) was used as the electron beam crosslinking agent. The ratio of the mass of the resin to the total mass of the resin and the electron beam crosslinking agent was 98% by mass. The ratio of the mass of the electron beam crosslinking agent to the total mass of the resin and the electron beam crosslinking agent was 2% by mass.

[0261] Next, using a mold 90 having a surface 90a shaped to correspond to the shape of the single-sided shaped object 80 to be produced, the material for the shaped object corresponding portion 13 was molded onto a peelable substrate. Thus, a pair of single-sided shaped objects 80 was produced from the material for the shaped object corresponding portion 13. When molding the material for the shaped object corresponding portion 13, a sheet-like inorganic material member 70 was placed on top of the mixture of resin and electron beam crosslinking agent, and then molding was performed. During molding, the mixture of resin and electron beam crosslinking agent and the inorganic material member 70 were press-processed. This press-processing caused a portion of the material derived from the mixture of resin and electron beam crosslinking agent to pass through the interior of the inorganic material member 70 and move to the upper side of the inorganic material member 70. Thus, a pair of single-sided shaped objects 80 was produced, each having a base 81 including a sheet-like inorganic material member 70, as shown in FIG. 19 . In particular, a pair of single-sided shaped bodies 80 were produced, each having a base 81 including a sheet-like inorganic material member 70 and a material surrounding the inorganic material member 70, the base 81 including a material derived from a mixture of resin and an electron beam crosslinking agent. Glass cloth (product name "LU1017:L01Z (vinylsilane-treated)" manufactured by Unitika Co., Ltd.) was used as the sheet-like inorganic material member 70. The produced pair of single-sided shaped bodies 80 had a sheet-like base 81 and a plurality of protrusions 82 formed on one side of the base 81. The thickness of the single-sided shaped body 80 (the sum of the thickness of the base 81 and the dimensions of the protrusions 82 in the thickness direction of the base 81) was 150 μm.

[0262] Furthermore, a resin sheet 32 ​​was prepared as the material for the central portion 30. The resin sheet 32 ​​was a resin sheet 32 ​​formed from a resin material in a sheet shape. The resin material contained in the resin sheet 32 ​​was linear low-density polyethylene raw material pellets (product name "DOWLEX (registered trademark): 2045.11G (C8 copolymer)", manufactured by Dow Chemical Company). This resin corresponds to linear low-density polyethylene (LLDPE). The thickness of the resin sheet 32 ​​was 50 μm.

[0263] Next, a pair of laminates including the single-sided shaped object 80 and the peelable substrate were overlapped so that the plurality of protrusions 82 of the pair of single-sided shaped objects 80 partially faced each other. As a result, the pair of single-sided shaped objects 80 were overlapped so that the plurality of protrusions 82 partially faced each other. At this time, a resin sheet 32 ​​was placed between the pair of single-sided shaped objects 80.

[0264] Next, the pair of single-sided shaped objects 80 were heat-pressed together. In particular, by heat-pressing the pair of single-sided shaped objects 80, the pair of single-sided shaped objects 80 were bonded to the resin sheet 32 ​​at the multiple protrusions 82. In this way, the pair of single-sided shaped objects 80 were bonded via the resin sheet 32. The heating temperature when heat-pressing the pair of single-sided shaped objects 80 was set to be higher than the Vicat softening point of the resin contained in the central portion 30.

[0265] Next, the releasable substrate was peeled off from the pair of single-sided shaped bodies 80 .

[0266] Next, a crosslinking process was performed in which the electron beam crosslinking agent contained in the single-sided shaped object 80 and the resin contained in the single-sided shaped object 80 were irradiated with an electron beam to react with the electron beam crosslinking agent. The electron beam irradiated had an acceleration voltage of 200 kV, a current value of 5 mA, and an exposure dose of 289 kGy. Furthermore, in the crosslinking process, the resin contained in the resin sheet 32 ​​was irradiated with an electron beam to react with the resin. More specifically, in the crosslinking process, the electron beam crosslinking agent and resin contained in the single-sided shaped object 80, and the resin contained in the resin sheet 32 ​​were simultaneously irradiated with an electron beam. This caused the electron beam crosslinking agent and resin in the single-sided shaped object 80 to react, and simultaneously caused the resin in the resin sheet 32 ​​to react. This resulted in the production of the hollow structure film 1 shown in FIG. 17. The ratio of the width w2 to the spacing w1 of the hollow structure film 1 was 1:3.

[0267] Example 13 A hollow structure film 1 was produced by the same method as in Example 12, except for the following points. In Example 13, a hollow structure film 1 similar to the hollow structure film 1 shown in FIG. 18 was produced. In Example 13, when molding the material for the shaped body corresponding portion 13, a sheet-like inorganic material member 70 was not placed inside the mixture of resin and electron beam crosslinking agent. In Example 13, when molding the material for the shaped body corresponding portion 13, multiple rod-like inorganic material members 70 were placed inside the mixture of resin and electron beam crosslinking agent and then molded. When producing a pair of single-sided shaped bodies 80, the amount of rod-like inorganic material members 70 added was 30% by mass relative to the total mass of the resin, electron beam crosslinking agent, and inorganic material members 70. This produced a pair of single-sided shaped bodies 80, in which the base 81 and all of the multiple protrusions 82 contained rod-like inorganic material members 70, as shown in FIG. 20. In Example 13, when the resin sheet 32 ​​was formed into a sheet shape, multiple rod-shaped inorganic material members 70 were placed inside a mixture of the resin and electron beam crosslinking agent, which were the materials for the resin sheet 32, and then the molding was performed. The amount of rod-shaped inorganic material members 70 added when producing the resin sheet 32 ​​was 30% by mass, in terms of the mass ratio to the total mass of the resin, electron beam crosslinking agent, and inorganic material members 70. Glass fiber (product name "SS05DE-413SP", manufactured by Nitto Boseki Co., Ltd.) was used as the rod-shaped inorganic material members 70. In this way, a resin sheet 32 ​​containing rod-shaped inorganic material members 70, as shown in FIG. 20, was produced. A hollow structure film 1 shown in FIG. 18 was produced using a pair of single-sided shaped objects 80 and a resin sheet 32 ​​produced as described above.

[0268] Example 14 A hollow structure film 1 was produced by the same method as in Example 13, except for the following points. In Example 14, a plurality of scaly inorganic material members 70 were used as the inorganic material members 70. With respect to the mixture of resin and electron beam crosslinking agent used as the material for the shaped body corresponding portion 13, the ratio of the mass of the resin to the total mass of the resin and the electron beam crosslinking agent was 60 mass%. When producing a pair of single-sided shaped bodies 80, the amount of scaly inorganic material members 70 added was 40 mass% in terms of the mass ratio to the total mass of the resin, electron beam crosslinking agent, and inorganic material members 70. As the scaly inorganic material members 70, a product named "REF015A" (manufactured by Nippon Sheet Glass Co., Ltd.) was used.

[0269] Comparative Example 7 An electron beam crosslinking agent was dispersed in a resin and molded into a sheet to produce a film, which was designated as the film of Comparative Example 7. High-density polyethylene raw material pellets (product name "Hi-Zex (registered trademark) 5000SR", manufactured by Prime Polymer Co., Ltd.) were used as the resin material contained in the film of Comparative Example 7. This resin corresponds to high-density polyethylene (HDPE). TAIC (registered trademark) (manufactured by Shinryo Corporation) was used as the electron beam crosslinking agent contained in the film of Comparative Example 7. The ratio of the mass of the resin to the total mass of the resin and the electron beam crosslinking agent was 95% by mass. The ratio of the mass of the electron beam crosslinking agent to the total mass of the resin and the electron beam crosslinking agent was 5% by mass. The thickness of the film of Comparative Example 7 was 350 μm.

[0270] (9) Porosity Measurement Test Next, a porosity measurement test was carried out on the hollow structure films 1 of Examples 12 to 14. The porosity measurement test was carried out in the same manner as in "(1) Porosity Measurement Test" for the hollow structure films 1 of Examples 1 to 9. The porosity of Comparative Example 7, which does not have the hollow portion B to begin with, was set to 0.

[0271] (10) Measurement Test of Dielectric Constant and Dielectric Loss Tangent Next, a measurement test of the dielectric constant and dielectric loss tangent was carried out on the hollow structure films 1 of Examples 12 to 14 and the film of Comparative Example 7. The measurement test of the dielectric constant and dielectric loss tangent was carried out in the same manner as in "(3) Measurement Test of Dielectric Constant and Dielectric Loss Tangent" for the hollow structure films 1 of Examples 1 to 9 and the films of Comparative Examples 1 to 3.

[0272] (11) CTE Measurement Test Next, a CTE measurement test was performed on the hollow structure films 1 of Examples 12 to 14 and the film of Comparative Example 7. In the CTE measurement test, the CTE of the main body 1c of the hollow structure films 1 of Examples 12 to 14 and the film of Comparative Example 7 was measured. The CTE measurement was performed using the following method. A thermomechanical analyzer (product name "TMA-60", manufactured by Shimadzu Corporation) was used as the measurement device. First, rectangular samples 97 with short sides 972 of 5 mm and long sides 971 of 14 mm, as shown in FIG. 25, were cut out from the hollow structure films 1 of Examples 12 to 14 and the film of Comparative Example 7. The region of the sample 97 with the short side 972 at one end and a width w15 of 2 mm in the direction of the long side 971 is referred to as the chucking region 98. The sample 97 has a pair of chucking regions 98, a first chucking region 981 and a second chucking region 982. An intermediate region 99 having a width w16 of 10 mm in the direction in which the long side 971 extends is formed between the first chucking region 981 and the second chucking region 982. In measuring the CTE, the first chucking region 981 was fixed to the first jig by sandwiching the entire first chucking region 981 with the first jig. Furthermore, the second chucking region 982 was fixed to the second jig by sandwiching the entire second chucking region 982 with the second jig. Next, a load of 3.0 g was applied to the intermediate region 99 of the sample 97, which was located between the first jig and the second jig, via the first jig and the second jig. With a load of 3.0 g applied to the intermediate region 99 in this manner, the sample 97, the first jig, and the second jig were placed inside a temperature-controlled chamber. The temperature inside the temperature-controlled chamber was then temporarily set to 10°C. The temperature inside the temperature-controlled chamber was then increased at a rate of 10°C / minute, and the amount of elongation of the intermediate region 99 of the sample 97 in the direction in which the long side 971 extended was measured. In particular, the width w16 of the intermediate region 99 when the temperature inside the temperature-controlled chamber reached 25°C and the width w16 of the intermediate region 99 when the temperature inside the temperature-controlled chamber reached 75°C were measured.From the above measurement results, the elongation of the width w16 of the intermediate region 99 was calculated in parts per million (ppm) when the temperature inside the temperature-controlled chamber was increased from 25°C to 75°C. The value obtained by dividing this elongation by 50 (°C) corresponds to the elongation of sample 97 when the temperature is increased by 1°C. This value was calculated as the CTE (ppm / °C).

[0273] (11) Evaluation Test for Copper Foil Peelability Next, a copper foil peelability evaluation test was conducted on the hollow structure films 1 of Examples 12 to 14 and the film of Comparative Example 7. In the copper foil peelability evaluation test, rectangular samples with long sides of 50 mm and short sides of 10 mm were cut out from the main body 1c of the hollow structure film 1 of each Example and the film of the Comparative Example. A metal adjacent layer material (30 μm thick, product name "Nucrel (registered trademark) AN4233C", manufactured by Dow Mitsui Polychemical Co., Ltd.) and copper foil (10 μm thick, product name "CF-LB9-10", purchased from Hosen Co., Ltd.) were laminated on the sample in this order so as to cover the entire sample. Next, the overlapping portions of the sample, metal adjacent layer material, and copper foil were heat-pressed at 100°C. A pressed portion was formed over the entire sample. The pressed portion was then left in a room at room temperature of 25°C for 48 hours. During the heat-pressing or after leaving the sample in the room, it was observed whether the copper foil peeled off from the sample.

[0274] The results of the porosity measurement test for the hollow structure films 1 of Examples 12 to 14 are shown in Table 3. In addition, the results of the dielectric constant and dielectric loss tangent measurement test, CTE measurement test, and copper foil peelability evaluation test for the hollow structure films 1 of Examples 12 to 14 and the film of Comparative Example 7 are shown in Table 3.

[0275]

[0276] From the results shown in Table 3, it was found that all of Examples 12 to 14 had a smaller dielectric constant than Comparative Example 7. It was found that all of Examples 12 to 14 had a smaller CTE than Comparative Example 7. It was found that all of Examples 12 to 14 had a CTE of 120 ppm / °C or less. Furthermore, in the evaluation test for the ease of peeling of the copper foil, no peeling of the copper foil from the sample occurred in all of Examples 12 to 14.

[0277] The components disclosed in the above-described embodiment and each modification may be combined as needed, or some components may be omitted from all the components shown in the above-described embodiment and each modification.

[0278] DESCRIPTION OF SYMBOLS 1 Hollow structure film 1a First surface 1b Second surface 10 Base 20 Support 30 Center 40 Metal layer 50 Particles 51 Glass particles 60 Metal adjacent layer 80 One-sided shaped body 81 Base 82 Convex portion 90 Mold 100 Circuit board 101 Antenna equipment

Claims

1. In a hollow structure film having a hollow structure, comprising a sheet-like first base portion, a sheet-like second base portion overlapping the first base portion, and a plurality of support portions provided between the first base portion and the second base portion, the first base portion has a first opposing surface facing the second base portion, the second base portion has a second opposing surface facing the first base portion, and at least a part of the plurality of support portions constitutes continuous support portions extending from the first opposing surface to the second opposing surface. A hollow structure film.

2. The support portion extends in a first direction perpendicular to the thickness direction of the hollow structure film. In a cross-section obtained by cutting the hollow structure film through the support portion and perpendicular to the first direction, the angle formed by the surface of the first base portion and the portion of the surface of the support portion connected to the first base portion is 90° or more and 150° or less. In a cross-section obtained by cutting the hollow structure film through the support portion and perpendicular to the first direction, the angle formed by the surface of the second base portion and the portion of the surface of the support portion connected to the second base portion is 90° or more and 150° or less. The hollow structure film according to claim 1.

3. The hollow structure film includes a main body portion. The main body portion includes the first base portion, the second base portion, the plurality of support portions, and a sheet-like central portion located between the first opposing surface and the second opposing surface. The plurality of support portions are located on the first opposing surface side and the second opposing surface side of the central portion. The hollow structure film according to claim 1.

4. The thickness is 50 μm or more and 1000 μm or less. The hollow structure film according to claim 1.

5. At least one of the first base portion, the second base portion, and the support portion is a first resin material having a density greater than 940 kg / m ３ and a second resin material having a density of 925 kg / m or less, the hollow structure film according to claim 1. ３ ​ 6. The storage elastic modulus is 1.0 × 10 5 Pa or more, and the hollow structure film according to claim 1.

7. Containing glass particles. The hollow structure film according to claim 1.

8. The glass particles have a hollow portion. The hollow structure film according to claim 7.

9. Containing a compound having a double bond active with respect to radiation or a thermal radical initiator. The hollow structure film according to claim 1.

10. The porosity is 20% or more. The hollow structure film according to claim 1.

11. The hollow structure film has a first surface and a second surface located on the side opposite to the first surface, and further includes a metal layer constituting at least a part of at least one of the first surface and the second surface. The hollow structure film according to any one of claims 1 to 10.

12. The hollow structure film according to claim 11, further comprising a metal adjacent layer that joins the metal layer and at least one of the first base portion and the second base portion, wherein the material of the metal adjacent layer is different from the materials of the first base portion and the second base portion.

13. The hollow structure film according to claim 11, further comprising a metal adjacent layer that joins the metal layer and at least one of the first base portion and the second base portion, wherein the material of the metal adjacent layer is an adhesive.

14. The hollow structure film according to claim 11, further comprising an ionomer layer or an ethylene (meth)acrylic acid copolymer layer that joins the metal layer and at least one of the first base portion and the second base portion.

15. The hollow structure film according to claim 11, wherein at least one of the following conditions is satisfied: the value of the transmission loss of an electrical signal with a frequency of 10 GHz applied to the linear wiring formed from the metal layer is greater than -0.30 dB / 3.5 cm; the value of the transmission loss of an electrical signal with a frequency of 20 GHz applied to the linear wiring is greater than -0.60 dB / 3.5 cm; the value of the transmission loss of an electrical signal with a frequency of 30 GHz applied to the linear wiring is greater than -0.90 dB / 3.5 cm; the value of the transmission loss of an electrical signal with a frequency of 40 GHz applied to the linear wiring is greater than -1.30 dB / 3.5 cm; the value of the transmission loss of an electrical signal with a frequency of 50 GHz applied to the linear wiring is greater than -1.80 dB / 3.5 cm; and the value of the transmission loss of an electrical signal with a frequency of 60 GHz applied to the linear wiring is greater than -3.00 dB / 3.5 cm.

16. A circuit board comprising: the hollow structure film according to any one of claims 1 to 10, the hollow structure film having a first surface and a second surface located on the side opposite to the first surface; and a wiring pattern provided on at least one of the first surface and the second surface.

17. An antenna device comprising: the circuit board according to claim 16; and an antenna element connected to the circuit board.

18. In a method for manufacturing a hollow-structured film having a hollow structure, a step of manufacturing a pair of single-sided shaped articles having a sheet-like base portion and a plurality of convex portions formed on one surface of the base portion using a mold; and a step of overlapping the pair of manufactured single-sided shaped articles such that at least a part of the plurality of convex portions face each other and performing thermocompression bonding. A method for manufacturing a hollow-structured film comprising these steps.

19. In a hollow-structured film having a hollow structure, a main body portion having a sheet-like first base portion, a sheet-like second base portion overlapping the first base portion, and a plurality of support portions provided between the first base portion and the second base portion; the first base portion has a first opposing surface facing the second base portion; the second base portion has a second opposing surface facing the first base portion; at least a part of the plurality of support portions constitutes continuous support portions extending from the first opposing surface to the second opposing surface; the main body portion includes an insulating inorganic material member; and the maximum width of the inorganic material member is three times or more the minimum width of the inorganic material member. A hollow-structured film.

20. The hollow-structured film according to claim 19, wherein the inorganic material member is included in at least one of the first base portion and the second base portion.

21. The hollow-structured film according to claim 19, wherein the inorganic material member is included in at least a part of the plurality of support portions.

22. The main body portion further has a sheet-like central portion located between the first opposing surface and the second opposing surface; and the plurality of support portions are located on the first opposing surface side and the second opposing surface side of the central portion. The hollow-structured film according to claim 19.

23. The hollow-structured film according to claim 22, wherein the inorganic material member is included in at least the central portion.

24. The hollow-structured film according to claim 19, wherein the inorganic material member includes glass.

25. The hollow-structured film according to claim 19, wherein the maximum width of the inorganic material member is 10 μm or more.

26. The hollow-structured film according to claim 19, wherein the main body portion includes polyolefin.

27. The hollow-structured film according to claim 19, having a thickness of 50 μm or more and 1000 μm or less.

28. The hollow-structured film according to claim 19, having a porosity of 20% or more.

29. The hollow structure film has a first surface and a second surface located on the side opposite to the first surface, and further includes a metal layer that constitutes at least a part of at least one of the first surface and the second surface. The hollow structure film according to claim 19.

30. The hollow structure film according to claim 29, further comprising a metal adjacent layer that joins the metal layer and at least one of the first base and the second base, and the material of the metal adjacent layer is different from the materials of the first base and the second base.

31. The hollow structure film according to claim 29, further comprising a metal adjacent layer that joins the metal layer and at least one of the first base and the second base, and the material of the metal adjacent layer is an adhesive.

32. The hollow structure film according to claim 29, further comprising an ionomer layer or an ethylene (meth)acrylic acid copolymer layer that joins the metal layer and at least one of the first base and the second base.

33. A circuit board comprising the hollow structure film according to any one of claims 19 to 28, the hollow structure film having a first surface and a second surface located on the side opposite to the first surface, and a wiring pattern provided on at least one of the first surface and the second surface.

34. An antenna device comprising the circuit board according to claim 33 and an antenna element connected to the circuit board.

35. In a method for manufacturing a hollow structure film having a hollow structure, a step of using a mold to produce a pair of single-sided shaped bodies each having a sheet-shaped base and a plurality of convex portions formed on one surface of the base and including an insulating inorganic material member, and a step of overlapping and thermocompression bonding the pair of produced single-sided shaped bodies such that at least a part of the plurality of convex portions face each other, wherein the maximum width of the inorganic material member is three times or more the minimum width of the inorganic material member. A method for manufacturing a hollow structure film.

Images