Hollow structure film, circuit board, antenna equipment and manufacturing method of hollow structure film

Abstract

To provide a film to be used in a circuit board, the film with a low dielectric constant while difficult to have a restriction by a material.SOLUTION: A hollow structure film 1 has a hollow structure and includes: a first base part 11 having a sheet-like shape; a second base part 12 having a sheet-like shape and overlapping the first base part 11; and a plurality of support pillar parts 20 disposed between the first base part 11 and the second base part 12. The first base part 11 includes a first opposing face 11a opposing the second base part 12. The second base part 12 includes a second opposing face 12a opposing the first base part 11. At least part of the plurality of support pillar parts 20 compose a continuous support pillar part 23 extending from the first opposing face 11a to the second opposing face 12a.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] In recent years, in information communication devices and the like, it has been required to transmit and receive a large amount of data at high speed. In response to such a background, the high-frequency conversion of electrical signals has been studied.

[0003] In particular, when using a communication standard corresponding to 5G in the communication system standards defined by the International Telecommunication Union (ITU), in Japan, higher frequencies such as the 4.5 GHz band and the 28 GHz band, which are higher frequencies than the 3.7 GHz band, which is the frequency band assigned to communication standards prior to 4G, are assigned to communication carriers.

[0004] On the other hand, a conventional circuit board designed mainly based on communication using a low-frequency band may have a relatively high dielectric constant value. The higher the dielectric constant value, the greater the propagation delay of the electrical signal. Therefore, in order to increase the propagation speed of the electrical signal and enable high-speed operation, it is preferable that the dielectric constant is lower. As described above, in order to enable large-capacity and high-speed communication with a circuit board used in a high-frequency band, it is required to make the dielectric constant of the circuit board lower than before.

[0005] In addition, when the dielectric constant of the circuit board is high, the transmission loss of the high-frequency current generated on the circuit tends to increase. Therefore, when attempting communication using the same magnitude of current, the higher the dielectric constant of the circuit board, the greater the radio wave loss, and as a result, the radio wave available for communication becomes weaker. As a result, it is more likely that inconveniences such as a shorter communication distance occur for a circuit board with a higher dielectric constant.

[0006] As a technique for making the dielectric constant of a circuit board or the like lower than before, a technique of using a material with a low dielectric constant for a circuit board or the like is known (for example, see Patent Document 1).

[0007] Patent Document 1 describes a technique for reducing the relative permittivity of a material by using a polyimide film as a material applied to a high-frequency substrate or the like.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0009] When reducing the permittivity of a film used for a circuit board by using a material with a low permittivity as the material, there may be inconveniences caused by having to use a specific material. For example, the cost required for manufacturing the circuit board may increase. Therefore, regarding the film used for the circuit board, it has been required to reduce the permittivity while being less restricted by the material.

[0010] The present disclosure has been made in consideration of the above points, and an object thereof is to provide a film with a low permittivity while being less restricted by the material.

Means for Solving the Problems

[0011] Embodiments of the present disclosure relate to the following [1] to

[17] .

[0012] [1] In a hollow structure film having a hollow structure, 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 a continuous support portion extending from the first opposing surface to the second opposing surface, and the hollow structure film.

[0013] [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 [1].

[0014] [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 [1] or [2].

[0015] [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.

[0016] [5] At least any 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 3 or less. The hollow structure film according to any one of [1] to [4].

[0017] [6] The storage elastic modulus is 1.0×10 5 Pa or more, the hollow structure film according to any one of [1] to [5].

[0018] [7] The hollow structure film according to any one of [1] to [6], comprising glass particles.

[0019] [8] The glass particles have a hollow portion, the hollow structure film according to [7].

[0020] [9] The hollow structure film according to any one of [1] to [8], comprising a compound having a double bond active with respect to radiation or a thermal radical initiator.

[0021]

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

[0022]

[11] The hollow structure film has a first surface and a second surface located on the side opposite to the first surface, The hollow structure film according to any one of [1] to

[10] , further comprising a metal layer constituting at least a part of at least one of the first surface and the second surface.

[0023]

[12] The hollow structure film according to

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

[11] .[[]END]]

[0024]

[13] The hollow structure film according to

[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 and the second base.

[0025]

[14] 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. At least one of these conditions is satisfied, and the hollow structure film according to any one of

[11] to

[13] .

[0026]

[15] 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 side opposite to the first surface, A wiring pattern provided on at least one of the first surface and the second surface, and a circuit board comprising the same.

[0027]

[16] The circuit board according to

[15] , An antenna element connected to the circuit board, and an antenna device comprising the same.

[0028]

[17] In a method for manufacturing a hollow structure film having a hollow structure, Using a mold, a step of producing a pair of single-sided shaped bodies having a sheet-like base and a plurality of convex portions formed on one surface of the base, A step of overlapping the pair of produced single-sided shaped bodies so that the plurality of convex portions face each other at least partially, and thermocompression bonding, and a method for manufacturing a hollow structure film comprising the same.

Advantages of the Invention

[0029] According to an embodiment of the present disclosure, a film with a low dielectric constant can be provided while being less susceptible to material limitations.

Brief Description of the Drawings

[0030]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6A

Figure 6B

Figure 6C

Figure 7A

Figure 7B

Figure 8A

Figure 8B

Figure 8C

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

Figure 16

Figure 17

Figure 18

Figure 19

Figure 20

Figure 21A

Figure 21B

Figure 22A

Figure 22B

Figure 22C

Figure 22D

Figure 23A

Figure 23B

Figure 23C

Figure 23D

Figure 23E

Figure 23F

Figure 24

Figure 25

Mode for Carrying Out the Invention

[0031] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings. In the drawings attached to this specification, for the sake of illustration and ease of understanding, the scale, the aspect ratio in the vertical and horizontal directions, etc. are appropriately changed and exaggerated from those of the actual object.

[0032] Terms used in this specification, such as terms specifying shapes, geometric conditions, and their degrees, for example, terms such as "parallel", "perpendicular", "identical", etc., and values of lengths and angles, etc., shall not be bound by a strict meaning and shall be interpreted to include a range to the extent that similar functions can be expected.

[0033] In this specification, terms such as "film", "sheet", and "plate" are not distinguished from each other based only on the difference in name.

[0034] In this specification, when a plurality of upper limit candidates and a plurality of lower limit candidates are listed for a certain parameter, the numerical range of that parameter may be constituted by combining any one upper limit candidate and any one lower limit candidate. As an example, consider the description "Parameter B may be A1 or more, may be A2 or more, and may be A3 or more. Parameter B may be A4 or less, may be A5 or less, and may be A6 or less." In this example, the numerical range of Parameter B may be A1 or more and A4 or less, may be A1 or more and A5 or less, may be A1 or more and A6 or less, may be A2 or more and A4 or less, may be A2 or more and A5 or less, may be A2 or more and A6 or less, may be A3 or more and A4 or less, may be A3 or more and A5 or less, and may be A3 or more and A6 or less.

[0035] In this specification, "suppression" means to hold back or prevent realization, occurrence, etc., or to interfere with realization, occurrence, etc. "Suppression" means not only to completely prevent realization, occurrence, etc., but also to reduce the possibility of realization, occurrence, etc. or to make it less likely for realization, occurrence, etc. to occur.

[0036] <Hollow structure film> Figs. 1 to 8C are diagrams showing an embodiment. Fig. 1 is a cross-sectional view of the hollow structure film 1 of this embodiment cut 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 Fig. 1, the hollow structure film 1 includes a pair of sheet-like bases 10. The hollow structure film 1 includes, as the pair of bases 10, a sheet-like first base 11 and a sheet-like second base 12 overlapping the first base 11. Further, the hollow structure film 1 includes a plurality of support portions 20 provided between the first base 11 and the second base 12. The hollow structure film 1 includes a main body portion 1c. In particular, the hollow structure film 1 shown in Fig. 1 consists of the main body portion 1c. The main body portion 1c has the first base 11, the second base 12, and the plurality of support portions 20. Thereby, the hollow structure film 1 includes, as a part of the main body portion 1c, the first base 11, the second base 12, and the plurality of support portions 20. The first base 11 has a first opposing surface 11a opposing the second base 12. The second base 12 has a second opposing surface 12a opposing the first base 11. At least a part of the plurality of support portions 20 extends 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 overlapping the first base 11 and the second base 12. In the example shown in Fig. 1, the main body portion 1c further has the central portion 30. Thereby, the hollow structure film 1 further includes, as a part of the main body portion 1c, the central portion 30. The central portion 30 is located between the first opposing surface 11a and the second opposing surface 12a.

[0037] In other words, the main body portion 1c includes the first base 11, the second base 12, the plurality of support portions 20, and a sheet-like central portion 30 located between the first opposing surface 11a and the second opposing surface 12a. The plurality of support portions 20 are located on the first opposing surface 11a side and the second opposing surface 12a side of the central portion 30.

[0038] A plurality of support portions 20 are provided between the first base portion 11 and the second base portion 12, whereby the first base portion 11 and the second base portion 12 are connected via the support portions 20. Further, the space between the first base portion 11 and the second base portion 12 is partitioned by the plurality of support portions 20, and a plurality of hollow portions B are formed between the first base portion 11 and the second base portion 12. Thereby, the hollow structure of the hollow structure film 1 is formed. Since the hollow structure film 1 has a hollow structure, the dielectric constant of the hollow structure film 1 is lowered. For this reason, it is possible to provide the hollow structure film 1 having a low dielectric constant while being less susceptible to restrictions on the material of the hollow structure film 1. In particular, it is possible to provide the hollow structure film 1 having a low dielectric constant without using a specific material having a low dielectric constant as the material of the hollow structure film 1.

[0039] The hollow structure film 1 has a first surface 1a and a second surface 1b located on the side opposite to the first surface 1a. In the example shown in FIG. 1, the first base portion 11 constitutes the first surface 1a. The second base portion 12 constitutes the second surface 1b. The first base portion 11 and the second base portion 12 overlap in the thickness direction of the hollow structure film 1.

[0040] The plurality of support portions 20 are provided between the pair of base portions 10, that is, between the first base portion 11 and the second base portion 12. In the example shown in FIG. 1, the plurality of support portions 20 extend in the thickness direction of the hollow structure film 1. At least a part of the plurality of support portions 20 extends from the first opposing surface 11a to the second opposing surface 12a. In the example shown in FIG. 1, at least a part of the plurality of support portions 20 extends from the first opposing surface 11a to the second opposing surface 12a in the thickness direction of the hollow structure film 1. The portion of the plurality of support portions 20 that extends from the first opposing surface 11a to the second opposing surface 12a is referred to as the continuous support portion 23. At least a part of the plurality of support portions 20 constitutes the continuous support portion 23 that extends from the first opposing surface 11a to the second opposing surface 12a. When a straight line L1 that extends 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 obtained by cutting the hollow structure film 1 with a plane parallel to the thickness direction, the support portion 20 through which the straight line L1 passes is regarded as the continuous support portion 23. When there is one or more cross-sections in which the continuous support portion 23 appears in the hollow structure film 1, it is regarded that at least a part of the plurality of support portions 20 extends from the first opposing surface 11a to the second opposing surface 12a in the hollow structure film 1. The continuous support portion 23 extends from the first opposing surface 11a to the second opposing surface 12a. The plurality of support portions 20 may include portions that do not extend from the first opposing surface 11a to the second opposing surface 12a. In the example shown in FIG. 1, the plurality of support portions 20 have a first portion 21 that extends from the first opposing surface 11a to a first central surface 30a of a central portion 30 described later as a portion that does not extend from the first opposing surface 11a to the second opposing surface 12a. The plurality of support portions 20 further have a second portion 22 that extends from the second base portion 12 to a second central surface 30b of the central portion 30 described later as a portion that does not extend from one of the pair of base portions 10 to the other.

[0041] FIG. 2 is a plan view showing one of a pair of bases 10 of the hollow structure film 1 shown in FIG. 1 (first base 11) as observed from the thickness direction of the hollow structure film 1. The portion of the base 10 connected to the support portion 20 is referred to as a connection portion 24. The broken line marked with reference numeral 20a shown in FIG. 2 indicates the contour of the connection portion 24 of the first base 11 connected to the support portion 20. In the example shown in FIG. 2, a plurality of connection portions 24 extend in a first direction d1 perpendicular to the thickness direction of the hollow structure film 1. For this reason, the plurality of 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 a connection portion 24 extending in a direction other than the first direction d1. For this reason, the hollow structure film 1 does not include a support portion 20 extending in a direction other than the first direction d1.

[0042] In the example shown in FIG. 2, the connection portions 24 of the first base 11 are arranged at equal intervals in a second direction d2 perpendicular to the thickness direction and the first direction d1 of the hollow structure film 1. That is, in the example shown in FIG. 2, the interval w1 between the connection portions 24 in the second direction d2 is the same. Although not shown, the interval w1 between the connection portions 24 in the second direction d2 may not be the same.

[0043] As an example, the connection portion 24 of the second base portion 12 extends in the same direction as the direction in which the connection portion 24 of the first base portion 11 extends, that is, in the first direction d1. In the present embodiment, the shape of the second base portion 12 and the portion located on the second base portion 12 side rather than the central portion 30 of the plurality of support portions 20 is the same as the shape of the portion located on the first base portion 11 side rather than the central portion 30 of the first base portion 11 and the plurality of support portions 20. The connection portion 24 of the second base portion 12 may extend in a direction different from the direction in which the connection portion 24 of the first base portion 11 extends. The shape of the second base portion 12 and the portion located on the second base portion 12 side rather than the central portion 30 of the plurality of support portions 20 may be different from the shape of the portion located on the first base portion 11 side rather than the central portion 30 of the first base portion 11 and the plurality of support portions 20. In this specification, unless otherwise specified, the hollow structure film 1 in which the connection portion 24 of the second base portion 12 extends in the same direction as the direction in which the connection portion 24 of the first base portion 11 extends will be described. In this specification, unless otherwise specified, the hollow structure film 1 in which the shape of the second base portion 12 and the portion located on the second base portion 12 side rather than the central portion 30 of the plurality of support portions 20 is the same as the shape of the portion located on the first base portion 11 side rather than the central portion 30 of the first base portion 11 and the plurality of support portions 20 will be described.

[0044] The hollow structure film 1 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 11a and the second opposing surface 12a. The central portion 30 has a first central surface 30a facing the first base portion 11 and a second central surface 30b facing the second base portion 12. The central portion 30 constitutes a part of the portion of the plurality of support portions 20 that extends from one of the pair of base portions 10 to the other. As shown in FIG. 1, even when the hollow structure film 1 includes the central portion 30, when a straight line L1 that extends 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 obtained by cutting the hollow structure film 1 with a plane parallel to the thickness direction, the support portion 20 through which the straight line L1 passes is regarded as a continuous support portion 23.

[0045] In the example shown in FIG. 1, the first portion 21 of the support portion 20 extends from the first opposing surface 11a of the first base portion 11 to the first central surface 30a of the central portion 30. That is, the first portion 21 of the support portion 20 is connected to the central portion 30. Further, the second portion 22 of the support portion 20 extends from the second opposing surface 12a of the second base portion 12 to the second central surface 30b of the central portion 30. That is, the second portion 22 of the support portion 20 is connected to the central portion 30.

[0046] By providing the central portion 30 in the hollow structure film 1, the strength of the hollow structure film 1 can be increased. In particular, by connecting the first portion 21 of the support portion 20 to the central portion 30 and connecting the second portion 22 of the support portion 20 to the central portion 30, the strength of the hollow structure film 1 can be further increased.

[0047] In this embodiment, the hollow structure film 1 contains a polyolefin. In particular, the main body portion 1c of the hollow structure film 1 contains a polyolefin. In this embodiment, each of the pair of base portions 10, the plurality of support portions 20, and the central portion 30 contains a resin. The resin contained in each of the pair of base portions 10, the plurality of support portions 20, and the central portion 30 may be a polyolefin. In this case, any one of polyethylene, polypropylene, and polymethylpentene may be used as the polyolefin. Each of the pair of base portions 10, the plurality of support portions 20, and the central portion 30 may contain polyethylene. Furthermore, these resins may have a partially modified structure. The hollow structure film 1 may contain a plurality of types of resins. Each of the pair of base portions 10, the plurality of support portions 20, and the central portion 30 may contain a plurality of resins having different molecular weights and branched structures in the polymer. Specific examples of the partially modified polymer include a polymer obtained by copolymerizing ethylene and acrylic acid (ethylene-acrylic acid copolymer). As an example of a case where a plurality of resins having different molecular weights are included, an example in which both general high-density polyethylene (HDPE) and low-density polyethylene (LDPE) are included can be cited. The material of the main body portion 1c of the hollow structure film 1 may be a material that can be molded using the mold 90 described later at a heating temperature of less than 330°C. Thereby, by heating the material using a general heating device and performing molding using the mold 90, the single-sided shaped body 80 described later can be produced, and the main body portion 1c can be produced from the single-sided shaped body 80.

[0048] The case where the hollow structure film 1 contains a plurality of types of resins will be described more specifically. The hollow structure film 1 has a density of 940 kg / m 3 It may contain a first resin material having a greater density and a second resin material having a density of 925 kg / m 3 or less. The first resin material having a density of 940 kg / m 3 or greater corresponds to, for example, high-density polyethylene (HDPE). The second resin material having a density of 925 kg / m 3The second resin material having the following density includes, for example, low-density polyethylene (LDPE). The density of the resin is measured according to the matters described in the item of "3.5.2 Density" in JIS K6922-1:2018. At least one of the first base portion 11, the second base portion 12, and the support portion 20 may include 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 of a mixture of the first resin material and the second resin material.

[0049] Examples of polyethylene products include High Zex (registered trademark) (HDPE), Neo Zex (registered trademark) (C4-LLDPE), Ultra Zex (registered trademark) (C6-LLDPE) manufactured by Prime Polymer Co., Ltd., DOWLEX (registered trademark): 2045.11G (C8 copolymer) (LLDPE) manufactured by The Dow Chemical Company, Novatec (registered trademark) HD (HDPE), Novatec (registered trademark) LL (LLDPE) manufactured by Japan Polyethylene Corporation, Suntech (registered trademark) HD (HDPE), Suntech (registered trademark) LD (LDPE) manufactured by Asahi Kasei Corporation, etc. Examples of polypropylene products include Prime Polypro (registered trademark) manufactured by Prime Polymer Co., Ltd., Novatec (registered trademark) PP manufactured by Japan Polypropylene Corporation, etc. Examples of polymethylpentene products include TPX (registered trademark) manufactured by Mitsui Chemicals, Inc., etc.

[0050] In the hollow structure film 1, the portions not constituted by the central portion 30 among the pair of base portions 10 and the plurality of support portions 20 are also collectively referred to as the shaped body corresponding portions 13. The resin contained in the shaped body corresponding portion 13 and the resin contained in the central portion 30 may be different. In this case, the shaped body corresponding portion 13 may include the first resin material and the central portion 30 may include the second resin material. The shaped body corresponding portion 13 may include the second resin material and the central portion 30 may include the first resin material. In this case, the boundary between the portion constituted by the central portion 30 and the portion not constituted by the central portion 30 among the plurality of support portions 20 is considered to be at the positions of the virtual plane F1 obtained by extending the first central plane 30a of the central portion 30 and the virtual plane F2 obtained by extending the second central plane 30b of the central portion 30.

[0051] The resin contained in the central portion 30 may have a lower melting point than the resin contained in the shaped body 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 body corresponding portion 13 may be high density polyethylene (HDPE).

[0052] The hollow structure film 1 of the present embodiment has a hollow structure. Thereby, the dielectric constant of the hollow structure film 1 can be lowered without using a specific material having a low dielectric constant as the material of the hollow structure film 1. For this reason, even when polyolefin is used as the material of each of the pair of base portions 10, the plurality of support portions 20, and the central portion 30, the dielectric constant of the hollow structure film 1 can be lowered. When polyolefin is used as the resin contained in the film that can be used as the material of a circuit board described later, such as the hollow structure film 1, the following effects can be obtained as compared with the case where, for example, polyimide is used as the resin contained in the film. Generally, since polyolefin is less expensive as a material than polyimide, the cost required for manufacturing the film and the circuit board can be reduced. In addition, as will be described later, when the metal layer 40 is joined to the surface of the portion formed by the resin of the film, the metal layer 40 can be more firmly adhered to the surface of the resin. Furthermore, generally, materials having a low dielectric constant, such as polyimide, often have a high melting point and are difficult to process. On the other hand, in the hollow structure film 1 of the present embodiment, it is not necessary to use a specific material having a low dielectric constant as the material of the hollow structure film 1. Thereby, as the material to be used, a material that can be processed by a simple method can be selected.

[0053] In the example shown in FIG. 1, the hollow structure film 1 includes particles 50 that can reduce the shrinkage amount of the hollow structure film 1 after heat processing. The particles 50 may increase the heat resistance of the hollow structure film 1. In the present embodiment, the particles 50 are dispersed in the resin that is the material of the hollow structure film 1. The particles 50 are included in the portion of the hollow structure film 1 that contains the resin. Thereby, the shrinkage amount of the portion of the hollow structure film 1 that contains the resin after heat processing can be reduced. Further, the heat resistance of the portion of the hollow structure film 1 that contains the resin can be increased. At least one of the shaped body corresponding portion 13 and the central portion 30 may contain the particles 50. Both the shaped body corresponding portion 13 and the central portion 30 may contain the particles 50. At least one of the pair of base portions 10, the plurality of support portions 20, and the central portion 30 may contain the particles 50. In the example shown in FIG. 1, each of the pair of base portions 10, the plurality of support portions 20, and the central portion 30 contains the particles 50. In FIG. 1 and FIGS. 4 to 8C and 10 described later, in order to avoid complication of the drawings, a part of the particles 50 contained in the hollow structure film 1 is illustrated, and the illustration of the other particles 50 is omitted. Since each of the pair of base portions 10, the plurality of support portions 20, and the central portion 30 contains the particles 50, the shrinkage amount of each of the pair of base portions 10, the plurality of support portions 20, and the central portion 30 after heat processing can be reduced. Further, the heat resistance of each of the pair of base portions 10, the plurality of support portions 20, and the central portion 30 can be increased. In particular, when the hollow structure film 1 is used for the circuit board 100, the hollow structure film 1 may be required to have heat resistance that can withstand the temperature during soldering. According to the hollow structure film 1 containing the particles 50, the heat resistance of the hollow structure film 1 can be increased to such an extent that it can stably withstand the temperature during soldering.

[0054] As an example, the particle 50 is a glass particle 51. That is, the hollow structure film 1 may contain the glass particle 51. In the example shown in FIG. 1, the glass particle 51 has a substantially spherical outer shape. Although not shown, the particle 50 may be a particle that can reduce the shrinkage amount of the hollow structure film 1 after heat processing, other than the glass particle 51. The material of the particle 50 may be, for example, a resin other than polyolefin and having heat resistance greater than that of polyolefin. The particle 50 may be an inorganic substance other than glass. The particle 50 may be, for example, a flake-shaped filler. The "flake-shaped filler" is, for example, a filler having a flat shape. Although not shown, the hollow structure film 1 may contain fibers that can reduce the shrinkage amount of the hollow structure film 1 after heat processing, instead of or together with the particle 50. In this case, the material of the above-described particle 50 can be used as the material of the fiber. The fiber is included, for example, in the portion described above as the portion where the particle 50 can be included in the hollow structure film 1.

[0055] The particle 50 may have a hollow portion 52. In the example shown in FIG. 1, the glass particle 51 has the hollow portion 52. The fact that the particle 50 has the hollow portion 52, particularly the fact that the glass particle 51 has the hollow portion 52, can further reduce the shrinkage amount of the hollow structure film 1 after heat processing. In addition, the hollow portion 52 can increase the heat resistance of the hollow structure film 1. Further, the hollow portion 52 can lower the dielectric constant of the hollow structure film 1. As a further effect, the hollow structure film 1 can also be lightened.

[0056] 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 above ratio is 1% by mass or more, when the shaped body corresponding portion 13 is processed in the manufacturing method of the hollow structure film 1 described later, etc., when the shaped body corresponding portion 13 is heated, it is possible to hardly cause a change in the dimensions of the shaped body corresponding portion 13. Also, when the hollow structure film 1 including the shaped body corresponding portion 13 is used as a product, even when the ambient temperature changes, it is possible to hardly cause a change in the dimensions of the shaped body corresponding portion 13. Although not shown, the shaped body corresponding portion 13 may not contain the 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% by mass or more. When the above ratio is 1% by mass or more, when the central portion 30 is heated in the manufacturing method of the hollow structure film 1 described later, etc., it is possible to hardly cause a change in the dimensions of the central portion 30. Although not shown, the central portion 30 may not contain the particles 50.

[0057] The hollow structure film 1 of the present embodiment may contain a compound having a double bond active with respect to radiation or a thermal radical initiator.

[0058] In particular, the hollow structure film 1 of the present embodiment may contain a compound having a double bond that is active with respect to radiation. The compound having a double bond that is active with respect 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 portion of the hollow structure film 1 that contains the resin. 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 method for manufacturing a hollow structure film having a crosslinking step described later. According to such a hollow structure film 1, the heat resistance of the hollow structure film 1 can be increased. In particular, when the hollow structure film 1 is used for the circuit board 100, the hollow structure film 1 may be required to have heat resistance that can withstand the temperature during soldering. According to the above-described hollow structure film 1, the heat resistance of the hollow structure film 1 can be increased to such an extent that it can withstand the temperature during soldering.

[0059] The hollow structure film 1 may contain an ionizing radiation curable compound as a compound having a double bond that is active with respect to radiation. The ionizing radiation curable compound means a compound that crosslinks and cures by irradiating ionizing radiation and has an ionizing radiation curable functional group. The ionizing radiation curable functional group is a group that crosslinks by irradiation with ionizing radiation, and examples thereof include functional groups having an ethylenic double bond (ethylenic unsaturated group) such as a (meth)acryloyl group, a vinyl group, and an allyl group. Ionizing radiation means an electromagnetic wave or a charged particle beam having an energy quantum capable of polymerizing or crosslinking a molecule. Examples of ionizing radiation include electron beams (EB) and ultraviolet rays (UV), electromagnetic waves such as X-rays and γ-rays, and charged particle beams such as α-rays and ion beams. The ionizing radiation curable compound that crosslinks and cures by irradiating an electron beam corresponds to the electron beam crosslinking agent described above.

[0060] Examples of the ionizing radiation-curable compound include polymerizable monomers and polymerizable oligomers that have been conventionally and commonly used as ionizing radiation-curable compounds. As the polymerizable monomer, a (meth)acrylate monomer having a (meth)acryloyl group in the molecule is preferable, and a polyfunctional (meth)acrylate monomer having two or more (meth)acryloyl groups in the molecule is more preferable. The number of (meth)acryloyl groups in the polyfunctional (meth)acrylate monomer is 2 or more, preferably 8 or less, and more preferably 6 or less.

[0061] 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 tetraethoxydi(meth)acrylate, and bisphenol A tetrapropoxydi(meth)acrylate; polyfunctional (meth)acrylates having three or more functions such as trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, 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 products, propylene oxide-modified products, caprolactone-modified products, isocyanuric acid-modified products, or propionic acid-modified products of these (meth)acrylates.

[0062] Examples of the polymerizable oligomers include (meth)acrylate oligomers having two or more (meth)acryloyl groups in the molecule. Examples of the (meth)acrylate oligomers 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 2 or more, preferably 8 or less, more preferably 6 or less.

[0063] Other examples of the polymerizable oligomers include highly hydrophobic polybutadiene (meth)acrylate-based oligomers having (meth)acryloyl groups in the side chains of polybutadiene oligomers, and silicone (meth)acrylate-based oligomers having polysiloxane bonds in the main chains.

[0064] The weight average molecular weight of the polymerizable oligomer may be 500 or more, 1,000 or more, 2,000 or more, 10,000 or less, 8,000 or less, or 6,000 or less. The weight average molecular weight is measured by gel permeation chromatography (GPC) analysis and is the average molecular weight converted to standard polystyrene.

[0065] As the radiation curable compound, a monofunctional (meth)acrylate may be appropriately used in combination with the polyfunctional (meth)acrylate for the purpose of reducing the viscosity of the curable composition during coating. 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.

[0066] As described above, the radiation-curable compound may have an allyl group. The radiation-curable compound having an allyl group may be triallyl cyanurate, triallyl citrate, or triallyl 1,3,5-benzenetricarboxylate.

[0067] The hollow structure film 1 may contain a thermal radical initiator. When the hollow structure film 1 contains a thermal radical initiator, when the shaping body corresponding portion 13 is processed by a method for manufacturing the hollow structure film 1 described later or the like, when the shaping body corresponding portion 13 is heated, a crosslinking reaction occurs due to the heat generated by the heating. By this crosslinking reaction, the heat resistance of the hollow structure film 1 can be greatly increased. In particular, when the hollow structure film 1 is used for the circuit board 100, the hollow structure film 1 may be required to have heat resistance that can withstand the temperature during soldering. According to the hollow structure film 1 containing a thermal radical initiator, the heat resistance of the hollow structure film 1 can be increased to such an extent that it can withstand the temperature 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 dimethyl 2,2'-azobis(2-methylpropionate), and peroxide compounds such as di-tert-butyl peroxide can be preferably used.

[0068] The thermal radical initiator may be used as a thermal radical polymerization initiator. That is, in addition to the compound having an active double bond, the hollow structure film 1 of the present embodiment may contain a compound generally known as a thermal radical polymerization initiator (a crosslinking agent that forms a chemical bond between molecules such as polyethylene when heated). When the hollow structure film 1 contains a thermal radical polymerization initiator, the following effects can be obtained. As will be described later, in the step of molding the material of the shaped body corresponding portion 13 in the method for producing the hollow structure film 1, the resin in the mixture that is the material of the shaped body corresponding portion 13 is melted while the mixture is molded. At this time, due to the inclusion of the thermal radical polymerization initiator, a bond can be formed between the molecules of the resin by the heat when melting the resin. Thereby, the heat resistance required when the hollow structure film 1 is used for the circuit board 100 can be more reliably ensured.

[0069] When the hollow structure film 1 of the present embodiment contains the above-described thermal radical polymerization initiator, in addition to the thermal radical polymerization initiator, it may further contain a silane coupling agent. In this case, the following effects can be obtained. As will be described later, in the step of molding the material of the shaped body corresponding portion 13 in the method for producing the hollow structure film 1, the resin in the mixture that is the material of the shaped body corresponding portion 13 is melted while the mixture is molded. At this time, due to the inclusion of the thermal radical polymerization initiator and the silane coupling agent, a crosslinking reaction occurs between the resin and the silane coupling agent by the reaction due to the heat when melting the resin. Further, in a step after the step of molding the material of the shaped body corresponding portion 13, the hollow structure film 1 may be stored in a high temperature and high humidity environment. In this case, when the hollow structure film 1 is stored in a high temperature and high humidity environment, a reaction occurs between the silane coupling agents. By these reactions, the heat resistance required when the hollow structure film 1 is used for the circuit board 100 can be more reliably ensured.

[0070] Specific examples of the thermal radical polymerization initiator include di-t-butyl peroxide, dicumyl peroxide, 2,2'-azobis(2,4-dimethylvaleronitrile), and the like.

[0071] Let 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, be the width w2. At this time, the interval w1 in the second direction d2 between the connection portions 24 is preferably 0.5 times or more and 20 times or less the width w2. When the interval w1 is 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 made particularly low. When the interval w1 is 20 times or less the width w2, the strength of the hollow structure film 1 can be made particularly large.

[0072] Let the distance between the base portion 10 and the central portion 30 in the hollow structure film 1 having the central portion 30 as shown in FIG. 1 be the distance w3. When the distance between the base portion 10 and the central portion 30 is not constant, let the distance between the connection portion 24 of the base portion 10 and the central portion 30 be the distance w3. At this time, the distance w3 is preferably 1 time or more and 10 times or less the width w2. When the distance w3 is 1 time 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 made particularly low. When the distance w3 is 10 times or less the width w2, the strength of the hollow structure film 1 can be made particularly large.

[0073] The cross-sectional view of the hollow structure film 1 shown in FIG. 1 corresponds to a view showing a cross-section obtained by cutting the hollow structure film 1 in which a plurality of support portions 20 extend in the first direction d1 in a plane passing through the plurality of support portions 20 and perpendicular to the first direction d1. In the cross-section as shown in FIG. 1, the angle θ1 formed by the first opposing surface 11a and the portion connecting to the first base portion 11 of the surface 20b of the support portion 20 in contact with the hollow portion B is 90° or more and 150° or less. In addition, in the cross-section as shown in FIG. 1, the angle θ2 formed by the second opposing surface 12a and the portion connecting to the second base portion 12 of the surface 20b of the support portion 20 in contact with the hollow portion B is 90° or more and 150° or less. When the angle θ1 and the angle θ2 are 90° or more and 150° or less, while ensuring the size of the hollow portion B and lowering the dielectric constant of the hollow structure film 1, the strength of the hollow structure film 1 can be ensured.

[0074] In the example shown in FIG. 1, the surface 20b of the support portion 20 in contact with 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 be a curved surface. When the surface 20b is not a flat surface, in the cross-sectional view of the hollow structure film 1, the surface 20b may appear as a curved surface or a broken line. In this case, the angle formed by the tangent line at the portion where the surface 20b appearing in the cross-sectional view of the hollow structure film 1 is connected to the first base portion 11 and the first opposing surface 11a is regarded as the angle θ1. Further, the angle formed by the tangent line at the portion where the surface 20b appearing in the cross-sectional view of the hollow structure film 1 is connected to the second base portion 12 and the second opposing surface 12a is regarded as the angle θ2.

[0075] As an example, the porosity of the hollow structure film 1 is 10% or more, more preferably 20% or more. By having the porosity of the hollow structure film 1 be 20% or more, 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 made particularly low. It is preferable that the porosity of the hollow structure film 1 is 70% or less. By having the porosity of the hollow structure film 1 be 70% or less, it is possible to suppress a decrease in the strength of the film 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. Observe a cross-section obtained by cutting the hollow structure film 1 through a plurality of support portions 20 and in a plane perpendicular to the first direction d1, as shown in FIG. 1. In the cross-section, draw a straight line L2 passing through the center of one of the plurality of connection portions 24 of one of the pair of base portions 10 (the first base portion 11) in the second direction d2 and parallel to the thickness direction of the hollow structure film 1. Further, identify a connection portion 24 that is adjacent to the connection portion 24 through which the straight line L2 is drawn among the plurality of connection portions 24 of one of the pair of base portions 10 (the first base portion 11) in the second direction d2. Draw a straight line L3 passing through the center of the connection portion 24 in the second direction d2 and parallel to the thickness direction of the hollow structure film 1. Subsequently, calculate the ratio of the area of the hollow portion B to the area of the entire hollow structure film 1 including the hollow portion B between the straight line L2 and the straight line L3. Calculate the ratio at 10 different locations of the cross-section. By averaging the ratios calculated at the 10 different locations, the porosity of the hollow structure film 1 is obtained. More specifically, a cross-section obtained by cutting the hollow structure film 1 through a plurality of support portions 20 and in a plane perpendicular to the first direction d1 is observed with a scanning electron microscope (SEM) or an optical microscope, and an image of the cross-section is acquired. The magnification of the acquired image can be 100 times or more. FIG. 3 is a diagram showing an example of an image of a cross-section of the hollow structure film 1 acquired by a scanning electron microscope (SEM). As shown in FIG. 3, by drawing the straight line L2 and the straight line L3 on the acquired image, the porosity of the hollow structure film 1 can be obtained from the image.

[0076] The hollow structure film 1 may further include a metal layer 40. In this case, a circuit board 100 described later can be manufactured by forming wiring 41 described later from at least a part of the metal layer 40. The hollow structure film 1 may further include a metal adjacent layer 60. The metal adjacent layer 60 can join the metal layer 40 more firmly to the base 10. FIG. 4 is a cross-sectional view showing an example of the 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 one in which the metal adjacent layer 60 and the metal layer 40 are laminated in this order on the first surface 1a of the hollow structure film 1 shown in FIG. 1. FIG. 5 is a cross-sectional view showing another example of the hollow structure film 1 including the metal layer 40 and the metal adjacent layer 60, which is different from FIG. 4. The hollow structure film 1 shown in FIG. 5 corresponds to the one 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 of the hollow structure film 1 shown in FIG. 1.

[0077] The hollow structure film 1 shown in FIGS. 4 and 5 has a first surface 1a and a second surface 1b located on the side opposite to the first surface 1a. The metal layer 40 constitutes at least a part of at least one of the first surface 1a and the second surface 1b. In the example shown in FIG. 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 a part of the first surface 1a. In the example shown in FIG. 5, the metal layer 40 constitutes the first surface 1a and the second surface 1b. In this case, the metal layer 40 may constitute the entire first surface 1a or a part of the first surface 1a. Further, the metal layer 40 may constitute the entire second surface 1b or a part of the second surface 1b.

[0078] The material of the metal layer 40 is not particularly limited as long as wiring 41 of a circuit board 100 described later can be formed from at least a part of the metal layer 40. The material of the metal layer 40 is, for example, copper. The metal layer 40 can be formed by joining a metal foil to the base 10. By joining 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.

[0079] The metal layer 40 may be formed by a method other than the method of joining 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 generally known seed layer may be formed. When forming the metal layer 40 by a process such as plating or sputtering, before forming the metal layer 40 on the surface of the base 10 where the metal layer 40 is to be formed, a plasma treatment known as glow treatment or reverse sputtering may be performed. By such treatment, the adhesion between the base 10 and the metal layer 40 can be made higher.

[0080] The metal adjacent layer 60 is a layer that joins the metal layer 40 and the base 10. The metal adjacent layer 60 joins the metal layer 40 and 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 layer of a resin that has good adhesion to metal and can be heat-sealed to polyolefin. By joining the metal layer 40 and the base 10 with the metal adjacent layer 60, the metal layer 40 can be joined more firmly to the base 10. The metal adjacent layer 60 may be an ionomer layer, that is, a layer of an ionomer resin. When the metal adjacent layer 60 is an ionomer layer, the material of the metal adjacent layer 60 is, for example, a carboxylic acid copolymer polyethylene containing metal ions. The metal adjacent layer 60 may be an ethylene (meth)acrylic acid copolymer polymer layer. That is, the hollow structure film 1 may further include an ionomer layer or an ethylene (meth)acrylic acid copolymer polymer layer that joins the metal layer 40 and the base 10. The hollow structure film 1 may further include an ionomer layer or an ethylene (meth)acrylic acid copolymer polymer layer that joins the metal layer 40 and at least one of the first base 11 and the second base 12. Thereby, the metal layer 40 can be joined more firmly to the base 10. The thickness of the metal adjacent layer 60 is, for example, 20 μm or less.

[0081] Specific examples of ionomers include Himilan (registered trademark) manufactured by Mitsui Dow Polychemical Co., Ltd. Specific examples of ethylene acrylic acid copolymer polymers include Nuclel (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 function as the resins described above can be suitably used as the material of the metal adjacent layer 60.

[0082] The metal adjacent layer 60 is not limited to the above examples. Any resin that exhibits a function of adhering to metal can be suitably used as the metal adjacent layer 60.

[0083] The metal adjacent layer 60 may be a layer formed by applying a varnish formed by dissolving a resin and drying the same. In the metal adjacent layer 60 of the above form, an adhesive may be used as the resin used for forming the varnish.

[0084] The metal adjacent layer 60 may be a bonding sheet available in a sheet form, for example, a commercially available bonding sheet in a sheet form.

[0085] Since the hollow structure film 1 of the present embodiment has a hollow structure, the dielectric constant can be lowered while increasing the thickness. Therefore, the thickness of the hollow structure film 1 of the present embodiment can be diverse. As an example, the thickness of the hollow structure film 1 is 50 μm or more and 1000 μm or less. Thus, according to the hollow structure film 1 of the present embodiment, the numerical range that can be adopted as the thickness of the hollow structure film 1 can be widened.

[0086] The storage elastic modulus of the hollow structure film 1 of the present embodiment is, for example, 1.0×10 5 Pa or more. When the hollow structure film 1 contains an electron beam crosslinking agent and, as will be described later, the electron beam crosslinking agent is irradiated with an electron beam in the manufacturing method of the hollow structure film 1, the storage elastic modulus of the hollow structure film 1 can be made 1.0×10 5 Pa or more. When the storage elastic modulus is equal to or less than the above lower limit value, the hollow structure film 1 is less likely to deform during high-temperature processing for a short time. Specifically, when soldering the hollow structure film 1 by a soldering reflow process, it becomes sufficiently difficult to deform. The storage elastic modulus of the hollow structure film 1 is measured using a dynamic viscoelasticity (DMA) measuring device. In the measurement of the storage elastic modulus of the hollow structure film 1, the measurement mode of the dynamic viscoelasticity measuring device is set to the tensile mode, and the storage elastic modulus when the temperature of the hollow structure film 1 is 280 °C is measured. As a method for measuring the storage elastic modulus of the hollow structure film 1, the method for measuring the storage elastic modulus described in the examples below can be adopted.

[0087] In the hollow structure film 1 including the metal layer 40 according to the present embodiment, at least one of the following conditions is satisfied: the value of the transmission loss of the electrical 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 value of the transmission loss of the electrical signal with a frequency of 20 GHz applied to the linear wiring 43 is greater than -0.60 dB / 3.5 cm; the value of the transmission loss of the electrical signal with a frequency of 30 GHz applied to the linear wiring 43 is greater than -0.90 dB / 3.5 cm; the value of the transmission loss of the electrical signal with a frequency of 40 GHz applied to the linear wiring 43 is greater than -1.30 dB / 3.5 cm; the value of the transmission loss of the electrical signal with a frequency of 50 GHz applied to the linear wiring 43 is greater than -1.80 dB / 3.5 cm; or the value of the transmission loss of the electrical signal with a frequency of 60 GHz applied to the linear wiring 43 is greater than -3.00 dB / 3.5 cm. The value of the transmission loss of the electrical signal has a negative value. The closer the value of the transmission loss of the electrical signal is to zero, the smaller the attenuation of the electrical signal applied to the linear wiring 43. Therefore, for example, the fact that the value of the transmission loss is 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 value of the transmission loss is -0.30 dB / 3.5 cm. "The value of the transmission loss is large" means that the value of the transmission loss having a negative value is close to zero. "The value of the transmission loss is small" means that the value of the transmission loss having a negative value is far from zero. Simply saying "the transmission loss is small" means that the absolute value of the value of the transmission loss having a negative value is small. Simply saying "the transmission loss is large" means that the absolute value of the value of the transmission loss having a negative value is large.

[0088] In the hollow structure film 1 including the metal layer 40, the value of the transmission loss of an electrical signal with 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 value of the transmission loss of an electrical signal with a frequency of 20 GHz applied to the linear wiring 43 may be 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 43 may be 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 43 may be 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 43 may be 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 43 may be greater than -3.00 dB / 3.5 cm. According to such a hollow structure film 1, even when electrical signals with various frequencies are applied to the wiring formed from the metal layer 40, the value of the transmission loss can be increased (close to zero).

[0089] In the hollow structure film 1 including the metal layer 40, the transmission loss of the electrical signal applied to the linear wiring 43 is measured by the following method. First, as shown in FIG. 6A, the linear wiring 43 is formed from the metal layer 40 of the hollow structure film 1. FIG. 6A is a perspective view showing the hollow structure film 1 having the linear wiring 43, which is used for measuring the transmission loss of the 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 not shown, and only the general shape of the main body portion 1c is shown. In FIG. 6A and FIG. 6C described later, the illustration of the metal adjacent layer 60 is omitted.

[0090] The hollow-structured film 1 shown in Fig. 6A is provided with a metal layer 40 on the first surface 1a side and the second surface 1b side. In the hollow-structured film 1 shown in Fig. 6A, a linear wiring 43 is formed from the metal layer 40 on the first surface 1a side. The hollow-structured film 1 shown in Fig. 6A is made from a hollow-structured film 1 having a metal layer 40 that constitutes at least a part of the first surface 1a and a metal layer 40 that constitutes at least a part of the second surface 1b, as shown in Fig. 5. The hollow-structured film 1 shown in Fig. 6A can be created by forming a linear wiring 43 from the metal layer 40 that constitutes at least a part of the first surface 1a of the hollow-structured film 1 as shown in Fig. 5. The method of forming the linear wiring 43 from the metal layer 40 can be the same as the method of forming a wiring pattern from the metal layer 40 in the manufacturing method of the circuit board 100 described later.

[0091] 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-structured film 1 of the present embodiment, the thickness w11 of the insulating portion corresponds to the thickness of the main body portion 1c. The film structure shown in and described above with reference to Fig. 6A 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 existing on the specific film becomes 50 Ω. The calculation formula used for adjusting 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 50 Ω. In the following formula, "ε r " means the dielectric constant, "Z0" means the characteristic impedance, "h" means the thickness w11, "w" means the width w6 of the linear wiring 43, and "t" means the thickness w12 of the linear wiring 43.

Equation

[0092] In the measurement of the transmission loss of the 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, as shown in FIG. 6, the probe 94 comes into contact with the linear wiring 43. Subsequently, an alternating electrical signal is applied to both ends of the linear wiring 43 from the network analyzer 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 section corresponding to a length of 5.0 cm of the linear wiring 43. At the time of measurement, in order to remove the influence of the jig 93 from the measurement result, de-embedding processing is performed. In the de-embedding processing, first, the transmission loss of the electrical signal in a section of 1.5 cm of a sample having the same wiring configuration as the linear wiring 43 is measured. Subsequently, de-embedding processing based on the measurement result of the transmission loss of the sample is performed. As a result, from the transmission loss measured by applying the electrical signal to a section corresponding to a length of 5.0 cm of the linear wiring 43, a value corresponding to the transmission loss measured by applying the electrical signal to a section corresponding to a length of 3.5 cm of the linear wiring 43, from which the influence of the transmission loss at both end portions of the linear wiring 43 and the jig 93 is removed, is calculated.

[0093] <Circuit board> Next, the circuit board 100 of the present embodiment will be described. The circuit board 100 of the present embodiment includes the hollow structure film 1 of the present embodiment. The circuit board 100 of the present embodiment further includes a wiring pattern provided on at least one of the first surface 1a and the second surface 1b. In the hollow structure film 1 including the metal layer 40 as shown in FIGS. 4 and 5, a circuit board 100 including the hollow structure film 1 and the wiring pattern of the wiring 41 can be manufactured by forming the wiring 41 from at least a part of the metal layer 40. The circuit board 100 manufactured by the above method can be regarded as a circuit board 100 including the hollow structure film 1 (the hollow structure film 1 shown in FIG. 1) including the main body portion 1c and the wiring pattern of the wiring 41.

[0094] When manufacturing the circuit board 100 from the hollow structure film 1 shown in FIG. 4, the 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 the circuit board 100 from the hollow structure film 1 shown in FIG. 5, the wiring pattern of the wiring 41 may be formed from one of the metal layer 40 constituting the first surface 1a and the metal layer 40 constituting the second surface 1b of the hollow structure film 1. When manufacturing the circuit board 100 from the hollow structure film 1 shown in FIG. 5, the 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.

[0095] When manufacturing the circuit board 100 from the hollow structure film 1 shown in Fig. 5, a wiring pattern of the wiring 41 is formed from the metal layer 40 constituting the first surface 1a of the hollow structure film 1, and it is not necessary to form a wiring pattern of the wiring 41 from 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 regarded as a circuit board 100 including the hollow structure film 1 (the hollow structure film 1 shown in Fig. 1) including the main body portion 1c, the wiring pattern of the wiring 41 provided on the first surface 1a of the hollow structure film 1, and the metal layer 40 on which no wiring pattern is formed provided on the second surface 1b of the hollow structure film 1. When the circuit board 100 includes the metal layer 40 on which no wiring pattern is formed provided on the second surface 1b together with the wiring pattern of the wiring 41 provided on the first surface 1a, unnecessary noise is less likely to occur when transmitting an electrical signal through the wiring 41. As reasons why unnecessary noise is less likely to occur due to the metal layer 40 on which no wiring pattern is formed provided on the second surface 1b, the following reasons can be considered. When a current flows through the wiring 41 formed on the first surface 1a side, a current in the direction opposite to the current flowing through the wiring 41 is generated on the second surface 1b side due to Ampere's law. In particular, when the wiring 41 formed on the first surface 1a side is fed with a high frequency and operated, a current in the direction opposite to the current flowing through the wiring 41 is generated on the second surface 1b side due to Ampere's law. This current is called a feedback current. The feedback current functions as a signal ground. In particular, when the feedback current forms an antenna loop with the wiring 41 and the ground plane, it effectively functions as a signal ground by reducing the formed antenna loop. As a result, unnecessary noise is less likely to occur.

[0096] <Antenna equipment> Next, the antenna device 101 of the present embodiment will be described. The antenna device 101 includes the circuit board 100 described above and an antenna element 102 connected to the circuit board 100. The antenna device 101 is, for example, a patch antenna. When the antenna device 101 is a patch antenna, the circuit board 100 functions as a dielectric substrate of the patch antenna. When the antenna device 101 is a patch antenna, the wiring 41 of the patch antenna may be formed to extend to the feeding point in order to conduct current, particularly high-frequency current. When the antenna device 101 is a patch antenna, a feeding method by electromagnetic coupling may be adopted for the patch antenna. In this case, the wiring 41 of the patch antenna does not have to be directly connected to the feeding point.

[0097] FIG. 6C is a perspective view showing an example of the antenna device 101 of the present embodiment. The antenna device 101 shown in FIG. 6C includes the above-described circuit board 100 and an antenna element 102 connected to the circuit board 100. The antenna element 102 is connected to a wiring 41 that forms a wiring pattern on 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 portion 1c, a wiring pattern of the wiring 41, and an 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 the wiring 41 provided on the first surface 1a of the hollow structure film 1, and a metal layer 40 on which no wiring pattern is formed provided on the second surface 1b of the hollow structure film 1. By providing the antenna device 101 with the metal layer 40 on which no wiring pattern is formed on the second surface 1b, unnecessary noise is less likely to occur when an electrical signal is transmitted through the wiring 41. The following reasons are considered for the reason that unnecessary noise is less likely to occur due to the metal layer 40 on which no wiring pattern is formed provided on the second surface 1b. When a current flows through the wiring 41 formed on the first surface 1a side, a current (the above-described feedback current) in the direction opposite to the current flowing through the wiring 41 is generated on the second surface 1b side due to Ampere's law. In particular, when the wiring 41 formed on the first surface 1a side is fed with a high frequency and operated, a feedback current is generated on the second surface 1b side. The feedback current functions as a signal ground. In particular, when the feedback current forms an antenna loop with the wiring 41 and the ground plane, the feedback current effectively functions as a signal ground by reducing the formed antenna loop. As a result, unnecessary noise is less likely to occur.

[0098] The antenna element 102 shown in FIG. 6C has a rectangular shape when observed in 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 device 101.

[0099] The antenna device 101 shown in FIG. 6C can be manufactured from the hollow structure film 1 shown in FIG. 5. Specifically, the antenna device 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.

[0100] <Manufacturing method of hollow structure film> The manufacturing method of the hollow structure film 1 of the present embodiment will be described. Unless otherwise specified, the manufacturing method of the hollow structure film 1 of the present embodiment will be described as a manufacturing method of the hollow structure film 1 in which the metal layer 40 constitutes the first surface 1a and the second surface 1b as shown in FIG. 5. The manufacturing method of the hollow structure film having a hollow structure according to the present embodiment includes a step of producing a pair of single-sided shaped bodies 80 each having a sheet-like base 81 and a plurality of convex portions 82 formed on one surface of the base 81, and a step of overlapping the produced pair of single-sided shaped bodies 80 so that the plurality of convex portions 82 face each other at least partially and thermocompression bonding them. The manufacturing method of the hollow structure film according to the present embodiment further includes a crosslinking step of reacting a compound having a double bond active against radiation contained in the single-sided shaped body 80 with a resin. When the compound having a double bond active against radiation is an electron beam crosslinking agent, in the crosslinking step, the electron beam crosslinking agent contained in the single-sided shaped body 80 is irradiated 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, preferable physical properties may be obtained by performing electron beam irradiation in the manufacturing process. For example, even if the hollow structure film 1 does not contain an electron beam crosslinking agent, the heat resistance of the hollow structure film 1 may be increased by performing electron beam irradiation in the manufacturing process. In this case, the hollow structure film 1 may not contain an electron beam crosslinking agent.

[0101] In the step of manufacturing the single-sided shaped body 80, a pair of single-sided shaped bodies 80 are manufactured using a mold 90. At this time, a metal foil 42 to be used as the material of the metal layer 40 is prepared. Further, the material of the shaped-body corresponding portion 13 is prepared. Further, the material of the metal adjacent layer 60 is prepared. In the present embodiment, the shaped-body corresponding portion 13 of the hollow structure film 1 to be manufactured contains a resin. In this case, as the material of the shaped-body corresponding portion 13, for example, raw material pellets of the corresponding resin are prepared. When the shaped-body corresponding portion 13 of the hollow structure film 1 to be manufactured contains polyethylene, polyethylene raw material pellets are prepared as 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 the particles 50, the particles 50 are prepared as 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 compound having a double bond that is active with respect to radiation, the compound is prepared as the material of the shaped-body corresponding portion 13. When the shaped-body corresponding portion 13 contains a plurality of materials, the plurality of materials are mixed to create a mixture. When the shaped-body corresponding portion 13 of the hollow structure film 1 to be manufactured contains a resin, the particles 50, and a compound having a double bond that is active with respect to radiation, a mixture of the resin, the particles 50, and the compound is created.

[0102] Subsequently, as shown in FIG. 7A, using the mold 90, the material of the shaped body corresponding portion 13 is molded. When the shaped body corresponding portion 13 of the manufactured hollow structure film 1 contains a resin, particles 50, and a compound having a double bond active with respect to radiation, the mixture of the resin, the particles 50, and the compound is molded using the mold 90. The molding of the mixture is performed while melting the resin contained in the mixture. The mold 90 has a surface 90a having a shape corresponding to the shape of the single-sided shaped body 80 to be produced. 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 on which a plurality of convex portions 82 are formed. By molding the material of the shaped body corresponding portion 13 with such a mold 90, a single-sided shaped body 80 having a sheet-like base portion 81 and a plurality of convex portions 82 formed on one surface of the base portion 81 is produced. In the present embodiment, by coextrusion molding, using the mold 90, 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. 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 in which the metal layer 40, the metal adjacent layer 60, and the single-sided shaped body 80 are laminated in this order is produced. Further, another single-sided shaped body 80 is produced by the same method as the method for producing the above-described single-sided shaped body 80. In the present embodiment, another laminate 83 is produced by the same method as the method for producing the above-described laminate 83.

[0103] When manufacturing the hollow structure film 1 in which the first surface 1a and the second surface 1b are not constituted by the metal layer 40 as shown in FIGS. 1 and 4, a single-sided shaping body 80, or a laminate of the metal adjacent layer 60 and the single-sided shaping body 80 may be produced by the following method. Instead of the metal foil 42, on a peelable base material, a shaping body corresponding part 13 material, or a laminate of the shaping body corresponding part 13 material and the metal adjacent layer 60 material is formed. Then, the base material is peeled off. In this case, as the peelable base material, for example, a polyimide film can be used. In particular, as the peelable base material, Kapton (registered trademark) manufactured by Toray DuPont Co., Ltd. can be used. When a peelable base material is used, the base material may be peeled off before the step of thermocompression bonding a pair of single-sided shaping bodies 80, or may be peeled off after the step of thermocompression bonding a pair of single-sided shaping bodies 80. When a peelable base material is used, the base material may be peeled off before the crosslinking step, or may be peeled off after the crosslinking step. As another peelable base material, a PET (polyethylene terephthalate) film can also be used. Specific examples of the peelable PET film include, for example, Cosmo Shine (registered trademark) and Cosmo Peel (registered trademark) manufactured by Toyobo Co., Ltd.

[0104] Subsequently, a step of thermocompression bonding a pair of single-sided shaping bodies 80 is performed. In this step, as shown in FIG. 7B, a pair of single-sided shaping bodies 80 are overlapped so that at least a part of the plurality of convex portions 82 face each other. A pair of single-sided shaping bodies 80 are overlapped so that the surfaces on which the plurality of convex portions 82 are formed face each other. In the present embodiment, a pair of laminates 83 including the single-sided shaping bodies 80 are overlapped so that at least a part of the plurality of convex portions 82 of the pair of single-sided shaping bodies 80 face each other.

[0105] 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, before the step of thermocompression bonding a pair of single-sided shaped bodies 80, the material for the central portion 30 is prepared. In the present embodiment, the central portion 30 of the manufactured hollow structure film 1 contains a resin. Further, the central portion 30 of the manufactured hollow structure film 1 contains particles 50. Further, the central portion 30 of the manufactured hollow structure film 1 contains a compound having a double bond that is active with respect to radiation. In this case, as the material for the central portion 30, a resin sheet 32 in which the particles 50 and the compound are dispersed in a resin and formed into a sheet shape can be used. As an example, the resin contained in the central portion 30 has a lower melting point than the resin contained in the shaped body corresponding portion 13. When manufacturing the hollow structure film 1 including the central portion 30, as shown in FIG. 7B, when overlapping a pair of single-sided shaped bodies 80, the resin sheet 32 is disposed between the pair of single-sided shaped bodies 80.

[0106] Subsequently, as shown in FIG. 8A, a pair of single-sided shaped bodies 80 are thermocompression bonded. Thereby, the pair of single-sided shaped bodies 80 are joined to each other. As shown in FIG. 7B, when the resin sheet 32 is disposed between the pair of single-sided shaped bodies 80, by thermocompression bonding the pair of single-sided shaped bodies 80 as shown in FIG. 8A, the pair of single-sided shaped bodies 80 are joined to the resin sheet 32 at a plurality of convex portions 82. Thereby, the pair of single-sided shaped bodies 80 are joined via the resin sheet 32. At this time, at the portion where the plurality of convex portions 82 of the pair of single-sided shaped bodies 80 are overlapped so as to face each other, the portions of the plurality of support portions 20 extending from the first opposing surface 11a to the second opposing surface 12a are formed. In particular, at the portion where the plurality of convex portions 82 of the pair of single-sided shaped bodies 80 are overlapped so as to face each other, a continuous support portion 23 is formed. Thereby, the shaped body corresponding portion 13 is formed from the pair of single-sided shaped bodies 80. Further, the central portion 30 is formed from the resin sheet 32. Further, a pair of base portions 10 (the first base portion 11 and the second base portion 12) are formed from the base portion 81 of the single-sided shaped body 80.

[0107] When heat-sealing a pair of single-sided embossed bodies 80, the heating temperature 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 heat-sealing a pair of single-sided embossed bodies 80 is higher than the Vicat softening point temperature of the linear low-density polyethylene. As a result, the resin sheet 32 can be softened by heat-sealing, and the pair of single-sided embossed bodies 80 can be joined to the resin sheet 32. In this case, as described above, since the resin contained in the central portion 30 has a lower melting point than the resin contained in the embossed body corresponding portion 13, when the resin contained in the central portion 30 is heated to a temperature higher than the Vicat softening point temperature, it is possible to suppress the single-sided embossed body 80 from being greatly deformed by the heating. The heating temperature when heat-sealing a pair of single-sided embossed bodies 80 can be equal to or lower than the Vicat softening point of the resin contained in the single-sided embossed body 80. When heat-sealing a pair of single-sided embossed bodies 80, a spacer 92 as shown in FIG. 8A may be used. The spacer 92 controls the pair of single-sided embossed bodies 80 so that they do not approach each other by more than a certain amount when the pair of single-sided embossed bodies 80 are brought closer to each other during heat-sealing. The thickness of the produced hollow-structured film 1 can be adjusted by the spacer 92.

[0108] In the step of thermocompression bonding a pair of single-sided embossed bodies 80, instead of the method using the spacer 92 described above, the pair of single-sided embossed bodies 80 may be thermocompression bonded by the following method. First, the pair of single-sided embossed bodies 80 is processed into a film shape having a length equal to or greater than a certain length. Subsequently, the pair of single-sided embossed bodies 80 is overlapped so that the plurality of convex portions 82 face each other at least in part. Subsequently, the pair of single-sided embossed bodies 80 is passed between two heated rolls in a state where they are overlapped with each other. In this case, when manufacturing the hollow structure film 1 including the central portion 30, a resin sheet 32 having a length equal to or greater than a certain length is prepared and sandwiched between the pair of overlapped single-sided embossed bodies 80. In this state, the pair of single-sided embossed bodies 80 and the resin sheet 32 are passed between two heated rolls. By the above method, the pair of single-sided embossed bodies 80 may be thermocompression bonded. When adopting the method using these two rolls, instead of using the spacer 92, by adjusting the interval between the two rolls, the thickness of the manufactured hollow structure film 1 can be adjusted to a suitable thickness.

[0109] Subsequently, a crosslinking step is performed in which a compound having a radiation-active double bond and a resin contained in the single-sided shaped body 80 are reacted. When the compound having a radiation-active double bond contained in the single-sided shaped body 80 is an electron beam crosslinking agent, in the crosslinking step, the electron beam crosslinking agent is irradiated with an electron beam to react the compound with the resin. In this case, the conditions of the electron beam irradiated in the crosslinking step are as follows, for example. The irradiation dose of the electron beam is, for example, 5 kGy or more and 500 kGy or less (0.5 Mrad or more and 50 Mrad or less), preferably 10 kGy or more and 300 kGy or less (1 Mrad or more and 30 Mrad or less). The irradiation dose of the electron beam is, for example, 200 kGy (20 Mrad). The acceleration voltage of the electron beam is, for example, 165 kV. When a resin sheet 32 in which a compound having a radiation-active double bond is dispersed in the resin and formed into a sheet shape is used as the material of the central portion 30, in the crosslinking step, the compound contained in the resin sheet 32 may be reacted with the resin. In this case, the method of reacting the compound contained in the resin sheet 32 with the resin is the same as the method of reacting the compound contained in the single-sided shaped body 80 with the resin. Thus, the hollow structure film 1 shown in FIG. 5 is manufactured.

[0110] The circuit board 100 including 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 formed by the metal layer 40. For example, when producing a laminate 83 in which the metal layer 40 and the single-sided shaped body 80 are laminated as shown in FIG. 7A, the laminate 83 is produced so that the entire surface of the single-sided shaped body 80 where a plurality of convex portions 82 are not formed is covered by 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 formed by the metal layer 40. As the metal layer 40, for example, a copper layer can be formed. As an example, the metal layer 40 is joined to the single-sided shaped body 80 via the metal adjacent layer 60. By covering the thus formed metal layer 40 with a mask layer and then etching, a wiring pattern can be formed from at least a part of the metal layer 40. More specifically, a wiring pattern can be formed from at least a part of the metal layer 40 by etching the metal layer 40 using, for example, a dry film resist (DFR) with a pattern formed thereon as a mask. Thereby, the circuit board 100 including the hollow structure film 1 and the wiring pattern can be manufactured.

[0111] 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 body 80 is formed. The pair of single-sided shaped bodies 80 shown in FIG. 8B have the same shape as the single-sided shaped body 80 included in the laminate 83 shown in FIG. 7A. Subsequently, a step of thermocompression bonding the pair of single-sided shaped bodies 80 is performed. In this step, as an example, as shown in FIG. 8B, a resin sheet 32 is disposed between the pair of single-sided shaped bodies 80. Subsequently, as shown in FIG. 8C, the pair of single-sided shaped bodies 80 are thermocompression bonded. Thereby, the pair of single-sided shaped bodies 80 are joined to each other. Subsequently, a metal layer 40 is formed so as to cover the entire surface of the single-sided shaped body 80 where a plurality of convex portions 82 are not formed. As an example, the metal layer 40 is joined to the single-sided shaped body 80 via a metal adjacent layer 60. By etching the thus formed metal layer 40 by the method described above or the like, a wiring pattern can be formed from at least a part of the metal layer 40. Thereby, the circuit board 100 including the hollow structure film 1 and the wiring pattern as described above can be manufactured.

[0112] The wiring pattern may be formed by attaching a copper wiring already formed to the base 10. The wiring pattern may be formed by forming a pattern of a plating seed layer by printing including inkjet and then plating up.

[0113] The antenna device 101 shown in FIG. 6C can be manufactured by forming a 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 of forming the wiring 41 and the antenna element 102 from the metal layer 40 can be the same as the method of forming the wiring pattern from the metal layer 40 in the manufacturing method of the circuit board 100 described above.

[0114] The wiring pattern may be formed by printing using a conductive ink. The wiring pattern may be formed by processing with a metal 3D printer.

[0115] The hollow structure film 1 of the present embodiment includes a sheet-like first base portion 11, a sheet-like second base portion 12 overlapping the first base portion 11, and a plurality of support portions 20 provided between the first base portion 11 and the second base portion 12. The first base portion 11 has a first opposing surface 11a facing the second base portion 12. The second base portion 12 has a second opposing surface 12a facing the first base portion 11. At least a part of the plurality of support portions 20 constitutes a continuous support portion 23 extending from the first opposing surface 11a to the second opposing surface 12a. Thereby, a plurality of hollow portions B are formed between the first base portion 11 and the second base portion 12. For this reason, the hollow structure film 1 has a hollow structure. According to such a hollow structure film 1, it is possible to reduce the restriction on the material of the hollow structure film 1 and lower the dielectric constant of the hollow structure film 1. Further, according to such a hollow structure film 1, the dielectric tangent of the hollow structure film 1 can be lowered by the hollow structure. The dielectric tangent indicates the amount of an electric signal propagating through a dielectric being converted into heat and lost. The lower the value of the dielectric tangent of the hollow structure film 1, the more the signal loss can be reduced and the transmission rate of the electric signal can be improved when the hollow structure film 1 is used for a circuit board designed on the premise of communication.

[0116] The effects of the low values of the dielectric constant and the dielectric tangent of the hollow structure film 1 will be described in more detail. There is a demand for higher frequencies of electric signals handled in information communication devices such as smartphones and tablet terminals. Along with this increase in the frequency of the electric signal, the transmission loss in a circuit board designed on the premise of communication increases (the value of the transmission loss having a negative value moves away from zero). On the other hand, it is known that transmission loss, particularly dielectric loss, can be reduced (the value of the transmission loss having a negative value approaches zero) by lowering the values of the dielectric constant and the dielectric tangent of the circuit board. The dielectric loss is represented by the following formula (1). In formula (1), α d is the dielectric loss, K is a proportionality constant, f is the frequency, ε γ is the relative dielectric constant, and tanδ is the dielectric tangent. The relative dielectric constant ε γ is the ratio of the dielectric constant of an object such as a circuit board to the dielectric constant of a vacuum.

Equation

[0117] From Equation (1), it can be understood that the dielectric loss can be reduced by lowering the values of the dielectric constant and the dielectric tangent of the circuit board. In particular, even when the value of the frequency becomes large, that is, when the electrical signal is high-frequencyized, it can be understood that the dielectric loss can be reduced by lowering the values of the dielectric constant and the dielectric tangent of the circuit board. From the above, in particular, by using the hollow structure film 1 of the present embodiment for a circuit board designed on the premise of communication, the loss of the signal can be reduced and the transmission rate of the electrical signal can be improved. In particular, in a circuit board that handles high-frequency electrical signals, it is required to lower the values of the dielectric constant and the dielectric tangent. For this reason, the hollow structure film 1 of the present embodiment is preferably used in a circuit board that handles high-frequency electrical signals. The hollow structure film 1 of the present embodiment is preferably used, for example, in a circuit board that handles electrical signals with a frequency 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 be used in a circuit board that handles electrical signals with a frequency 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 the present embodiment may be used in a circuit board that handles electrical signals with a frequency of 60 GHz or higher and 80 GHz or lower.

[0118] As a sheet with a low dielectric constant, for example, a sheet manufactured by forming a resin foam containing bubbles, such as the two-dimensional communication low-dielectric sheet disclosed in Japanese Patent No. 5976714, is also known. Examples of sheets that are resin foams containing bubbles include Softron manufactured by Sekisui Chemical Co., Ltd., and SKYBOND (registered trademark) FOAM manufactured by I.S.T. Co., Ltd. However, the hollow structure film 1 of the present embodiment includes a plurality of support portions 20, and in particular, at least a part of the plurality of support portions 20 constitutes a continuous support portion 23, which is clearly different from a sheet made of a resin foam. The hollow structure film 1 of the present embodiment has a greater hardness by having a plurality of support portions 20 compared to a sheet made of a resin foam. In particular, the hollow structure film 1 of the present embodiment has a greater indentation hardness compared to a sheet made of a resin foam. Thus, the hollow structure film 1 of the present embodiment is clearly different from a sheet made of a resin foam in physical properties such as hardness. Since a sheet made of a resin foam is flexible and easily bent, it is considered difficult to use it for forming a circuit board 100 such as the antenna device 101.

[0119] The hollow structure film 1 of the present 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 11a and the second opposing surface 12a. Thereby, the strength of the hollow structure film 1 can be increased further.

[0120] The hollow structure film 1 of the present embodiment includes a main body portion 1c. The main body portion 1c includes the first base portion 11, the second base portion 12, a plurality of support portions 20, and a sheet-like central portion 30 located between the first opposing surface 11a and the second opposing surface 12a. The plurality of support portions 20 are located on the first opposing surface 11a side and the second opposing surface 12a side of the central portion 30. Thereby, the strength of the hollow structure film 1 can be increased further.

[0121] The hollow structure film 1 of the present embodiment contains glass particles 51. Thereby, the shrinkage amount of the hollow structure film 1 after processing by heating can be made smaller.

[0122] In the hollow structure film 1 of the present embodiment, the glass particles 51 have a hollow portion 52. Thereby, the shrinkage amount of the hollow structure film 1 after processing by heating can be made smaller.

[0123] The hollow structure film 1 of the present embodiment has a first surface 1a and a second surface 1b located on the side opposite to the first surface 1a. The hollow structure film 1 of the present embodiment further includes a metal layer 40 that constitutes at least a part of at least one of the first surface 1a and the second surface 1b. Thereby, by forming a wiring pattern on the metal layer 40, a wiring 41 can be formed from the metal layer 40.

[0124] The hollow structure film 1 of the present embodiment further includes a metal adjacent layer 60 that joins the metal layer 40 and the base 10. Thereby, the metal layer 40 can be joined to the base 10 more firmly.

[0125] The circuit board 100 of the present embodiment is the above-described hollow structure film 1, and includes the hollow structure film 1 having a first surface 1a and a second surface 1b located on the side opposite to the first surface 1a, and a wiring pattern provided on at least one of the first surface 1a and the second surface 1b. Thereby, the dielectric constant of the circuit board 100 can be lowered.

[0126] The antenna device 101 of the present embodiment includes the above-described circuit board 100 and an antenna element connected to the circuit board 100. Thereby, the dielectric constant of the circuit board 100 can be lowered. For this reason, the transmission loss in the circuit board can be reduced (the value of the transmission loss having a negative value can be made closer to zero).

[0127] <Modification Example> Next, with reference to FIGS. 9 to 12, various modification examples of the present embodiment will be described. In FIGS. 9 to 12, the same parts as those shown in FIGS. 1 to 8C are denoted by the same reference numerals, and detailed description thereof is omitted.

[0128] <Modification Example 1> In the above-described embodiment, the hollow structure film 1 having a plurality of connecting portions 24 where the base 10 extends in the first direction d1 and not having connecting portions 24 extending in a direction other than the first direction d1 has been described. Further, the hollow structure film 1 having a plurality of support portions 20 extending in the first direction d1 and not having support portions 20 extending in a direction other than the first direction d1 has been described. However, the extending directions of the connecting portions 24 and the support portions 20 are not limited to the above-described examples. FIG. 9 is a plan view showing a state in which the base 10 of Modification 1 is observed from the thickness direction of the hollow structure film 1, and is a figure corresponding to FIG. 2. In the example shown in FIG. 9, the base 10 has a plurality of connecting portions 24. In the example shown in FIG. 9, as a plurality of connecting portions 24, the base 10 has a first connecting portion 24a extending in the first direction d1. In addition, in the example shown in FIG. 9, as a plurality of connecting portions 24, the base 10 has a second connecting portion 24b extending in a third direction d3 that is perpendicular to the thickness direction of the hollow structure film 1 and different from the first direction d1. In the example shown in FIG. 9, the third direction d3 is a direction perpendicular to the first direction d1. In other words, the third direction d3 coincides with the second direction d2. Since the base 10 has the first connecting portion 24a and the second connecting portion 24b as a plurality of connecting portions 24, the hollow structure film 1 of Modification 1 includes 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. Even with such a base 10 having the connecting portion 24 and the hollow structure film 1 including the support portion 20, a hollow structure can be formed and the dielectric constant can be kept low.

[0129] The hollow structure film 1 of Modification 1 includes 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 such a hollow structure film 1, the above-described angle θ1, angle θ2, and porosity are measured based on a portion where the plurality of support portions 20 extending in the third direction d3 do not appear in a cross section cut along a plane passing through the plurality of support portions 20 and perpendicular to the first direction d1.

[0130] <Modification 2> In the above-described embodiment, the hollow structure film 1 having the central portion 30 as shown in FIG. 1 has been described. However, the hollow structure film 1 may not have the central portion 30. FIG. 10 is a cross-sectional view of the hollow structure film 1 of Modification 2 cut along a cross-section parallel to the thickness direction of the hollow structure film 1, and is a figure corresponding to FIG. 1. In the example shown in FIG. 10, the hollow structure film 1 does not have the central portion 30. In the example shown in FIG. 10, at least a part of the plurality of support portions 20 extends in the thickness direction of the hollow structure film 1 from the first opposing surface 11a to the second opposing surface 12a. In the example shown in FIG. 10, a part of the plurality of support portions 20 constitutes the continuous support portion 23. The portions of the plurality of support portions 20 that do not constitute the continuous support portion 23 constitute convex portions 25 that protrude from the first opposing surface 11a toward the second opposing surface 12a or protrude from the second opposing surface 12a toward the first opposing surface 11a.

[0131] In the hollow structure film 1 in which a part of the plurality of support portions 20 constitutes the convex portion 25 as shown in FIG. 10, the height of the convex portion 25 (the dimension of the convex portion 25 in the thickness direction of the hollow structure film 1) is defined as height w4. At this time, it is preferable that the height w4 is 0.5 times or more and 10 times or less the width w2 of the connection portion 24 in the second direction d2. By the height w4 being 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 made particularly low. By the height w4 being 10 times or less the width w2, the strength of the hollow structure film 1 can be made particularly large.

[0132] The hollow structure film 1 without the central portion 30 as shown in FIG. 10 can be manufactured by the same method as the manufacturing method of the hollow structure film 1 with the central portion 30 of the above-described embodiment, except for the points described below. In the step of thermocompression bonding a pair of single-sided shaped bodies 80, the pair of single-sided shaped bodies 80 are overlapped without disposing the resin sheet 32 between the pair of single-sided shaped bodies 80. Then, the pair of single-sided shaped bodies 80 are thermocompression bonded. As a result, a plurality of opposing convex portions 82 of the pair of single-sided shaped bodies 80 are joined to each other. By joining the opposing convex portions 82 to each other, the continuous support portions 23 are formed. Thereby, the pair of single-sided shaped bodies 80 are directly joined to each other. The convex portion 82 of one of the pair of single-sided shaped bodies 80, which does not face the convex portion 82 of the other single-sided shaped body 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 thermocompression bonding the pair of single-sided shaped bodies 80 is adjusted to a temperature at which the single-sided shaped bodies 80 are softened and the pair of single-sided shaped bodies 80 can be directly joined to each other.

[0133] Even with the hollow structure film 1 of Modification 2, a hollow structure can be formed and the dielectric constant can be kept low.

[0134] <Modification 3> When manufacturing the hollow structure film 1 without the central portion 30, the hollow structure film 1 may be manufactured using a pair of single-sided shaping bodies 80 described below. FIG. 11 is a diagram showing the single-sided shaping body 80 used in the manufacturing method of the hollow structure film of Modification 3. In the example shown in FIG. 11, the single-sided shaping body 80 includes 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 shaping body 80 on which a plurality of 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 a portion not constituted by the first layer 84 of the plurality of convex portions 82 and the base portion 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. By adopting such a configuration, when the pair of single-sided shaping bodies 80 are heat-bonded, the first layer 84 can be sufficiently melted while maintaining the shape of the second layer 85. As a result, the pair of single-sided shaping bodies 80 can be joined to each other while making it difficult for the overall shape of the single-sided shaping body 80 to be deformed. 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 contain the particles 50 that can be contained in the central portion 30 in the above-described embodiment. The first layer 84 may contain a compound having a double bond that is active with respect to radiation, which can 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 shaping body corresponding portion 13 in the above-described embodiment.

[0135] The single-sided shaping body 80 shown in FIG. 11 can be produced by co-extrusion molding using a mold similar to the mold 90 shown in FIG. 7A to mold the material of the second layer 85 containing the second resin and the material of the first layer 84 containing the first resin on the metal foil 42.

[0136] By using a pair of single-sided embossed bodies 80 shown in Fig. 11, a hollow-structured film 1 without a central portion 30 as shown in Fig. 12 can be manufactured. The manufacturing method of the hollow-structured film 1 in this case can be manufactured by the same method as the manufacturing method of the hollow-structured film 1 without a central portion 30 in the above-described Modification 2, except for the points described below. The heating temperature when heat-sealing the pair of single-sided embossed bodies 80 is adjusted to a temperature at which the first layer 84 of the single-sided embossed body 80 is softened and the pair of single-sided embossed bodies 80 can be directly joined together. As an example, the heating temperature when heat-sealing the pair of single-sided embossed bodies 80 is higher than the Vicat softening point temperature of the first resin contained in the first layer 84. Thereby, the first layer 84 is softened by heat-sealing, and a plurality of opposing convex portions 82 of the pair of single-sided embossed bodies 80 can be joined together. In particular, portions of the plurality of opposing convex portions 82 of the pair of single-sided embossed bodies 80, which are constituted by the first layer 84, can be joined 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, it is possible to suppress the large deformation of the second layer 85 due to heating.

[0137] <Modification 4> In the above-described embodiments and each modification, an example of manufacturing the hollow-structured film 1 using two single-sided embossed bodies 80 has been described. However, the manufacturing method of the hollow-structured film 1 is not limited to this. The hollow-structured film 1 may be manufactured using one single-sided embossed body 80. Fig. 13 is a diagram showing the manufacturing method of the hollow-structured film of Modification 4. Fig. 14 is a diagram showing the hollow-structured film 1 manufactured by the manufacturing method of the hollow-structured film of Modification 4.

[0138] In the example shown in FIG. 13, the resin sheet 32 is arranged so as to face the surface of one single-sided embossing body 80 on which a plurality of convex portions 82 are formed. The method for manufacturing the hollow structure film of Modification 4 includes a step of thermocompression bonding the single-sided embossing body 80 and the resin sheet 32 arranged as shown in FIG. 13. Thereby, a hollow structure film 1 including a pair of base portions 10 and a plurality of support portions 20 as shown in FIG. 14 can be manufactured. At this time, the plurality of support portions 20 are formed from the plurality of convex portions 82 of the single-sided embossing body 80. In the example shown in FIG. 14, a first base portion 11 is formed from the base portion 81 of the single-sided embossing body 80. In the example shown in FIG. 14, a second base portion 12 is formed from the resin sheet 32. Although not shown, the second base portion 12 may be formed from the base portion 81 of the single-sided embossing body 80, and the first base portion 11 may be formed from the resin sheet 32.

[0139] When thermocompression bonding the single-sided embossing body 80 and the resin sheet 32, a spacer 92 as shown in FIG. 13 may be used. The spacer 92 controls so that the single-sided embossing body 80 and the resin sheet 32 do not approach each other more than a certain level when approaching the single-sided embossing body 80 and the resin sheet 32 with respect to each other when thermocompression bonding the single-sided embossing body 80 and the resin sheet 32. The thickness of the manufactured hollow structure film 1 can be adjusted by the spacer 92.

[0140] The hollow structure film 1 of Modification 4 may include a metal layer 40 that constitutes 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 joins the metal layer 40 and the base portion 10 as shown in FIG. 14. In this case, the metal layer 40 may be joined to the single-sided embossing body 80 or the resin sheet 32 via the metal adjacent layer 60 before the step of thermocompression bonding the single-sided embossing body 80 and the resin sheet 32, or may be joined to the base portion 10 via the metal adjacent layer 60 after the step of thermocompression bonding the single-sided embossing body 80 and the resin sheet 32.

[0141] According to the method for manufacturing the hollow structure film of Modification 4 and the hollow structure film 1, a hollow structure film 1 having a particularly small thickness can be provided.

[0142] <Modification Example 5> In the above-described embodiments and each modification example, an example of manufacturing the hollow structure film 1 using two or less single-sided imparting members 80 has been described. 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 imparting members 80. FIG. 15 is a diagram showing the members used in the manufacturing method of the hollow structure film of Modification Example 5 arranged in the order in which they are stacked when manufacturing the hollow structure film 1. FIG. 16 is a diagram showing the hollow structure film 1 manufactured by the manufacturing method of the hollow structure film of Modification Example 5.

[0143] In the example shown in FIG. 15, the members used in the manufacturing method of the hollow structure film include four single-sided imparting members 80. The four single-sided imparting members 80 are stacked in the thickness direction of the base portion 81. The members used in the manufacturing method of the hollow structure film further include three resin sheets 32. The four single-sided imparting members 80 and the three resin sheets 32 are stacked so as to be alternately arranged in the thickness direction of the base portion 81. The manufacturing method of the hollow structure film of Modification Example 4 includes a step of thermocompression bonding the single-sided imparting member 80 and the resin sheet 32 arranged as shown in FIG. 15. Thereby, a hollow structure film 1 including a pair of base portions 10 and a plurality of support portions 20 as shown in FIG. 16 can be manufactured. At this time, the plurality of support portions 20 are formed from the plurality of convex portions 82 of the plurality of single-sided imparting members 80. In particular, in the portion where the plurality of convex portions 82 of the plurality of single-sided imparting members 80 are overlapped so as to face each other, a continuous support portion 23 extending from the first opposing surface 11a to the second opposing surface 12a of the plurality of support portions 20 is formed. A pair of base portions 10 are formed from the base portions 81 of the pair of single-sided imparting members 80 located on the outermost side in the thickness direction of the base portion 81.

[0144] In the step of thermocompression bonding the single-sided shaped body 80 and the resin sheet 32, the order of thermocompression bonding the plurality of single-sided shaped bodies 80 and the plurality of resin sheets 32 is not particularly limited. The hollow structure film 1 may be manufactured by simultaneously thermocompression bonding all of the plurality of single-sided shaped bodies 80 and the plurality of resin sheets 32. The hollow structure film 1 may be manufactured by repeating the thermocompression bonding of adjacent single-sided shaped bodies 80 and resin sheets 32. The manufacture of the hollow structure film 1 shown in FIG. 16 may be performed by the following method. The first single-sided shaped body 80a shown in FIG. 15 and the second single-sided shaped body 80b are joined via the first resin sheet 32a. Further, the third single-sided shaped body 80c and the fourth single-sided shaped body 80d shown in FIG. 15 are joined via the second resin sheet 32b. Thereafter, the second single-sided shaped body 80b and the third single-sided shaped body 80c are joined via the third resin sheet 32c.

[0145] As shown in FIG. 16, the hollow structure film 1 of Modification 5 may include a metal layer 40 that constitutes 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 and the base 10. In this case, the metal layer 40 may be joined to one of the single-sided shaped bodies 80 via the metal adjacent layer 60 before the step of thermocompression bonding the single-sided shaped body 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 body 80 and the resin sheet 32.

[0146] According to the manufacturing method of the hollow structure film of Modification 5 and the hollow structure film 1, a hollow structure film 1 having a particularly large thickness can be provided.

[0147] <Modification 6> The main body portion 1c of the hollow structure film 1 may include an insulating inorganic material member 70. The ratio of the maximum width to the minimum width of the inorganic material member 70 is 1:3 or more. 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 different from the example shown in FIG. 17 of the hollow structure film 1 of Modification 6.

[0148] 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 having a sufficiently small dielectric constant and dissipation factor is used in consideration of sufficiently lowering the dielectric constant and dissipation factor of the entire hollow structure film 1.

[0149] The inorganic material member 70 may be included in at least one of the first base portion 11 and the second base portion 12. The inorganic material member 70 may be included in both the first base portion 11 and the second base portion 12. The inorganic material member 70 may be included in at least a part of the plurality of support portions 20. The inorganic material member 70 may be included in all of the plurality of support portions 20. When the main body portion 1c has the 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 portion 11 and the second base portion 12. In the example shown in FIG. 18, the inorganic material member 70 is included in the first base portion 11, the second base portion 12, all of the plurality of support portions 20, and the central portion 30.

[0150] The inorganic material member 70 may be a sheet-like member as shown in FIG. 17. The sheet-like inorganic material member 70 is a fabric made of fibrous glass, which is called, for example, glass cloth.

[0151] In the example shown in FIG. 17, the sheet-like inorganic material member 70 is included in both the first base portion 11 and the second base portion 12. The surface of the first base portion 11 on the side opposite to 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 portion 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 portion 11. The surface of the second base portion 12 on the side opposite to 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 portion 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 portion 12.

[0152] Although not shown in the figure, when the main body portion 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.

[0153] The inorganic material member 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 fibrous glass, for example, called glass fiber. In the example shown in FIG. 18, the plurality of rod-shaped inorganic material members 70 are dispersed inside the main body portion 1c. The plurality of rod-shaped inorganic material members 70 are oriented in different directions from each other. The maximum width of the rod-shaped inorganic material member 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 all of the first base portion 11, the second base portion 12, the plurality of support portions 20, and the central portion 30.

[0154] Although not shown, the inorganic material member 70 may be a plurality of flaky members. The plurality of flaky inorganic material members 70 may be, for example, glass flakes (registered trademark) manufactured by Nippon Sheet Glass Co., Ltd. The plurality of flaky inorganic material members 70 may be fine flakes (registered trademark) manufactured by Nippon Sheet Glass Co., Ltd. The plurality of flaky inorganic material members 70 may be dispersed inside the main body portion 1c. The plurality of flaky inorganic material members 70 may be oriented in different directions from each other. The maximum width of the flaky inorganic material member 70 is, for example, 100 μm. The minimum width (thickness) of the flaky inorganic material member 70 is, for example, 0.5 μm or more and 6 μm or less. When the inorganic material member 70 is a plurality of flaky 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 which is a plurality of flaky members may contain glass. The inorganic material member 70 which is a plurality of flaky members may contain aluminum oxide. The inorganic material member 70 which is a plurality of flaky members may contain boehmite.

[0155] Although not shown, the main body portion 1c may contain, as the inorganic material member 70, any two or more selected from the group consisting of a sheet-like member, a plurality of rod-like members, and a plurality of flaky members.

[0156] The main body portion 1c containing the inorganic material member 70 may further contain the above-described glass particles 51. The main body portion 1c containing the inorganic material member 70 may not contain the glass particles 51. The ratio of the maximum width to the minimum width of the glass particles 51 may be less than 1:3.

[0157] The effect of the main body part 1c including the inorganic material member 70 will be described. Consider the case where the metal layer 40 is joined to a part (such as the base part 10, the single-sided shaped body 80, and the resin sheet 32) that constitutes at least a part of the main body part 1c. In this case, due to the difference in CTE (coefficient of thermal expansion, that is, the coefficient of thermal expansion) between the main body part 1c and the metal layer 40, the metal layer 40 may peel off from the main body part 1c or wrinkles may occur in the metal layer 40. In particular, when the metal layer 40 and the main body part 1c are joined and heat is applied to the metal layer 40 and the main body part 1c, due to the difference in CTE between the main body part 1c and the metal layer 40, the metal layer 40 may peel off from the main body part 1c or wrinkles may occur in the metal layer 40. In particular, when the metal layer 40 is formed from a copper foil and the main body part 1c contains a polyolefin, the difference in CTE between the main body part 1c and the metal layer 40 can be large. In this case, the CTE of the metal layer 40 can be smaller than the CTE of the main body part 1c. In this case, the metal layer 40 may peel off from the main body part 1c or wrinkles may occur in the metal layer 40.

[0158] On the other hand, by including the inorganic material member 70 in the main body portion 1c, the CTE of the main body portion 1c can be adjusted. Thereby, the CTE of the hollow structure film 1 having a low dielectric constant due to its hollow structure can 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 becomes small. 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 made 120 ppm / °C or less. By including the inorganic material member 70 containing glass or metal oxide, 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 becomes small. In particular, when the main body portion 1c contains polyolefin, by further including the inorganic material member 70 in the main body portion 1c, the CTE of the main body portion 1c can be reduced. As described above, by including the inorganic material member 70 in the main body portion 1c and adjusting the CTE of the main body portion 1c so that the difference in CTE between the main body portion 1c and the metal layer 40 becomes small, the metal layer 40 can be made less likely to peel off from the main body portion 1c, and wrinkles are less likely to occur in the metal layer 40. 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 made less likely to peel off from the main body portion 1c, and wrinkles are less likely to occur in the metal layer 40. Further, by reducing the difference in CTE between the main body portion 1c and the metal layer 40, warping of the hollow structure film 1 due to the difference in CTE between the main body portion 1c and the metal layer 40 becomes less likely to occur. Thereby, the workability of the hollow structure film 1 can be ensured.

[0159] The manufacturing method of the hollow-structured film 1 of Modification Example 6 can be the same as the manufacturing method of the hollow-structured film 1 in the above-described embodiment, except that the single-sided formed body 80 produced in the step of producing a pair of single-sided formed bodies 80 contains the insulating inorganic material member 70. At least one of the pair of single-sided formed bodies 80 may contain the inorganic material member 70. Both of the pair of single-sided formed bodies 80 may contain the inorganic material member 70. The inorganic material member 70 may be contained in the base portion 81 of the single-sided formed body 80. The inorganic material member 70 may be contained in at least a part of the plurality of convex portions 82. The inorganic material member 70 may be contained in all of the plurality of convex portions 82. When the resin sheet 32 is used in the manufacture of the hollow-structured film 1, the inorganic material member 70 may be contained in the resin sheet 32.

[0160] The hollow-structured film 1 shown in Fig. 17 can be manufactured from a pair of single-sided formed bodies 80 in which a sheet-like inorganic material member 70 is contained in the base portion 81, as shown in Fig. 19, and a resin sheet 32. The hollow-structured film 1 shown in Fig. 18 can be manufactured from a pair of single-sided formed bodies 80 in which rod-shaped inorganic material members 70 are contained in all of the base portion 81 and the plurality of convex portions 82, as shown in Fig. 20, and a resin sheet 32 in which a rod-shaped inorganic material member 70 is contained.

[0161] The hollow-structured film 1 of Modification Example 6 includes a main body portion 1c having a sheet-like first base portion 11, a sheet-like second base portion 12 overlapping the first base portion 11, and a plurality of support portions 20 provided between the first base portion 11 and the second base portion 12. The first base portion 11 has a first opposing surface 11a facing the second base portion 12. The second base portion 12 has a second opposing surface 12a facing the first base portion 11. At least a part of the plurality of support portions 20 constitutes a continuous support portion 23 extending from the first opposing surface 11a to the second opposing surface 12a. The main body portion 1c contains an insulating inorganic material member 70. The ratio of the maximum width to the minimum width of the inorganic material member 70 is 1:3 or more. Thereby, the metal layer 40 can be made difficult to peel off from the main body portion 1c, and wrinkles can be made difficult to occur in the metal layer 40.

[0162] 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 portion 11 and the second base portion 12. Thereby, when the base portion 10 and the metal layer 40 are joined, the CTE of the base portion 10 can be adjusted so that the difference in CTE between the base portion 10 and the metal layer 40 becomes small. Thereby, it is possible to make it difficult for the metal layer 40 to peel from the base portion 10, and it is possible to make it difficult for wrinkles to occur in the metal layer 40 joined to the base portion 10.

[0163] In the hollow structure film 1 of Modification 6, the inorganic material member 70 may be included in at least a part of the plurality of support portions 20. Also by this, 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 becomes small. Thereby, it is possible to make it difficult for the metal layer 40 to peel from the main body portion 1c, and it is possible to make it difficult for wrinkles to occur in the metal layer 40.

[0164] In the hollow structure film 1 of Modification 6, the main body portion 1c may further have 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. In this case, the inorganic material member 70 may be included in at least the central portion 30. Also by this, 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 becomes small. Thereby, it is possible to make it difficult for the metal layer 40 to peel from the main body portion 1c, and it is possible to make it difficult for wrinkles to occur in the metal layer 40.

[0165] In the hollow structure film 1 of Modification 6, the inorganic material member 70 may contain glass. Thereby, using the inorganic material member 70, the CTE of the main body portion 1c can be adjusted more effectively so that the difference in CTE between the main body portion 1c and the metal layer 40 becomes small.

[0166] The maximum width of the inorganic material member 70 may be 10 μm or more. Thereby, using the inorganic material member 70, the CTE of the main body portion 1c can be adjusted more effectively so that the difference in CTE between the main body portion 1c and the metal layer 40 becomes small.

[0167] The manufacturing method of the hollow structure film 1 of Modification 6 includes a step of using a mold 90 to produce a pair of single-sided shaped bodies 80 having a sheet-like base portion 81 and a plurality of convex portions 82 formed on one surface of the base portion 81 and including an insulating inorganic material member 70, and a step of overlapping the produced pair of single-sided shaped bodies 80 so that the plurality of convex portions 82 face each other at least partially and performing thermocompression bonding. The ratio of the maximum width to the minimum width of the inorganic material member 70 is 1:3 or more. By such a manufacturing method, the hollow structure film 1 in which the main body portion 1c includes the inorganic material member 70 can be manufactured.

[0168] <Modification 7> The forms of the connection portion 24 and the support portion 20 are not limited to the examples described in the above-described embodiments and each modification. The hollow structure film 1 has a first end portion 1d and a second end portion 1e as end portions in the first direction d1. In the hollow structure film 1, the connection portion 24 and the support portion 20 do not have to extend from the first end portion 1d to the second end portion 1e.

[0169] In the example shown in FIG. 2 described above, the base portion 10 has a plurality of connecting portions 24 extending in the first direction d1 and does not have connecting portions 24 extending in a direction other than the first direction d1. Further, in the example shown in FIG. 2 described above, the hollow structure film 1 includes a plurality of support portions 20 extending in the first direction d1 and does not include support portions 20 extending in a direction other than the first direction d1. In the example shown in FIG. 2 described above, the connecting portion 24 and the support portion 20 extend from the first end portion 1d to the second end portion 1e. However, regarding the hollow structure film 1 that does not include connecting portions 24 and support portions 20 extending in a direction other than the first direction d1, the forms of the connecting portion 24 and the support portion 20 are not limited thereto. FIG. 21A is a plan view showing a state of observing an example of the hollow structure film 1 of Modification 7 from the thickness direction of the hollow structure film 1, and is a figure corresponding to FIG. 2. That is, FIG. 21A is a plan view showing a state of observing one (the first base portion 11) of a pair of base portions 10 in an example of the hollow structure film 1 from the thickness direction of the hollow structure film 1 by the same expression as FIG. 2. As shown in FIG. 21A, the connecting portion 24 and the support portion 20 do not necessarily extend from the first end portion 1d to the second end portion 1e. In the example shown in FIG. 21A, the connecting portion 24 and the support portion 20 are not located at the first end portion 1d. Further, in the example shown in FIG. 21A, the connecting portion 24 and the support portion 20 are not located at the second end portion 1e.

[0170] FIG. 21B is a perspective view showing a single-sided embossing body 80 used for manufacturing the hollow structure film 1 shown in FIG. 21A. In the figure showing the single-sided embossing body 80 including FIG. 21B, the direction that becomes the first direction d1 when the hollow structure film 1 is manufactured using the single-sided embossing body 80 is shown as the first direction d1. Further, the direction that becomes the second direction d2 when the hollow structure film 1 is manufactured using the single-sided embossing body 80 is shown as the second direction d2. The hollow structure film 1 shown in FIG. 21A can be manufactured using the single-sided embossing body 80 shown in FIG. 21B. The single-sided embossing body 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. Further, in the example shown in FIG. 21B, the convex portion 82 is not located at the second end 802.

[0171] In the example shown in FIG. 9 described above, the hollow structure film 1 has a third end portion 1f and a fourth end portion 1g as end portions in the third direction d3. In the example shown in FIG. 9 described above, the base portion 10 has a first connecting portion 24a extending in the first direction d1 and a second connecting portion 24b extending in the third direction d3 as a plurality of connecting portions 24. Further, in the example shown in FIG. 9 described above, the hollow structure film 1 includes a plurality of strut portions 20 extending in the first direction d1 and a plurality of strut portions 20 extending in the third direction d3. In the example shown in FIG. 9 described above, the first connecting portion 24a and the strut portions 20 extending in the first direction d1 extend from the first end portion 1d to the second end portion 1e. In the example shown in FIG. 9 described above, the second connecting portion 24b and the strut portions 20 extending in the third direction d3 extend from the third end portion 1f to the fourth end portion 1g. However, with respect to the hollow structure film 1 in which the base portion 10 has the first connecting portion 24a and the second connecting portion 24b and includes the strut portions 20 extending in the first direction d1 and the strut portions 20 extending in the third direction d3, the forms of the connecting portion 24 and the strut portions 20 are not limited thereto. FIGS. 22A, 22B, and 22C are plan views showing a state in which an example of the hollow structure film 1 of Modification 7 is observed from the thickness direction of the hollow structure film 1, and correspond to FIG. 2. As shown in FIGS. 22A, 22B, and 22C, the first connecting portion 24a and the strut portions 20 extending in the first direction d1 do not have to extend from the first end portion 1d to the second end portion 1e. As shown in FIGS. 22A, 22B, and 22C, the second connecting portion 24b and the strut portions 20 extending in the third direction d3 do not have to extend from the third end portion 1f to the fourth end portion 1g. In the example shown in FIGS. 22A, 22B, and 22C, the connecting portion 24 and the strut portions 20 are not located at the first end portion 1d. In the example shown in FIGS. 22A, 22B, and 22C, the connecting portion 24 and the strut portions 20 are not located at the second end portion 1e. In the example shown in FIGS. 22A, 22B, and 22C, the connecting portion 24 and the strut portions 20 are not located at the third end portion 1f. Further, in the example shown in FIGS. 22A, 22B, and 22C, the connecting portion 24 and the strut portions 20 are not located at the fourth end portion 1g.

[0172] As shown in Fig. 22A, the first connection portion 24a and the second connection 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.

[0173] As shown in Figs. 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 Fig. 22B, a "+" shape may be formed by connecting the first connection portion 24a and the second connection portion 24b to each other. A "+" shape may be formed by connecting the support portion 20 extending in the first direction d1 and the support portion 20 extending in the third direction d3 to each other. As shown in Fig. 22C, an L-shaped may be formed by connecting the first connection portion 24a and the second connection portion 24b to each other. An L-shaped may be formed by connecting the support portion 20 extending in the first direction d1 and the support portion 20 extending in the third direction d3 to each other.

[0174] The hollow structure film 1 shown in FIGS. 22A, 22B, and 22C can be manufactured using a single-sided embossing body 80 having a corresponding shape for each. As an example, the single-sided embossing body 80 used for manufacturing the hollow structure film 1 shown in FIG. 22A will be described. FIG. 22D is a perspective view showing the single-sided embossing body 80 used for manufacturing the hollow structure film 1 shown in FIG. 22A. In FIG. 22D, the direction that becomes the third direction d3 when the hollow structure film 1 is manufactured using the single-sided embossing body 80 is shown as the third direction d3. The single-sided embossing body 80 has a first end portion 801 and a second end portion 802 as end portions in the first direction d1. The single-sided embossing body 80 has a third end portion 803 and a fourth end portion 804 as end portions in the third direction d3. In the example shown in FIG. 22D, the single-sided embossing body 80 includes a convex portion 82 that extends in the first direction d1 and a convex portion 82 that extends in the third direction d3. In the example shown in FIG. 22D, the convex portion 82 extending in the first direction d1 does not extend from the first end portion 801 to the second end portion 802. In the example shown in FIG. 22D, the convex portion 82 extending in the third direction d3 does not extend from the third end portion 803 to the fourth end portion 804. In the example shown in FIG. 22D, the convex portion 82 is not located at the first end portion 801. In the example shown in FIG. 22D, the convex portion 82 is not located at the second end portion 802. In the example shown in FIG. 22D, the convex portion 82 is not located at the third end portion 803. Further, in the example shown in FIG. 22D, the convex portion 82 is not located at the fourth end portion 804.

[0175] Even with the hollow structure film 1 of Modification 7, a hollow structure can be formed and the dielectric constant can be kept low.

[0176] <Modification 8> The forms of the connection portion 24 and the support portion 20 are not limited to the examples described in the above-described embodiments and each modification. The contour shapes of the connection portion 24 and the support portion 20 observed from the thickness direction of the hollow structure film 1 may be shapes other than a rectangle having a short side and a long side. FIGS. 23A, 23B, and 23C are plan views showing a state in which an example of the hollow structure film 1 of Modification 8 is observed from the thickness direction of the hollow structure film 1, and are figures corresponding to FIG. 2. In the example shown in FIG. 23A, the contour shapes of the connection portion 24 and the support portion 20 observed from the thickness direction of the hollow structure film 1 are square. In the examples shown in FIGS. 23B and 23C, the contour shapes of the connection portion 24 and the support portion 20 observed from the thickness direction of the hollow structure film 1 are circular. Although not shown, the contour shapes of the connection portion 24 and the support portion 20 observed from the thickness direction of the hollow structure film 1 may be elliptical. In the hollow structure film 1, the connection portion 24 and the support portion 20 may not extend in the first direction d1.

[0177] Furthermore, the method of arranging the connection portion 24 and the support portion 20 is not particularly limited as long as the continuous support portion 23 can be formed. In the examples shown in FIGS. 23A, 23B, and 23C, the connection portion 24 and the support portion 20 are regularly arranged. In the examples shown in FIGS. 23A, 23B, and 23C, the connection portion 24 and the support portion 20 are arranged at equal intervals. Although not shown, the connection portion 24 and the support portion 20 may be randomly arranged. The hollow structure film 1 may have a region where the connection portion 24 and the support portion 20 are regularly arranged and a region where the connection portion 24 and the support portion 20 are randomly arranged.

[0178] As shown in FIGS. 23A and 23B, the connection portion 24 and the support portion 20 may be arranged along the fourth direction d4, which is one of the extending directions of the end side 1h of the hollow structure film 1, and the fifth direction d5 that intersects the fourth direction d4. In the examples shown in FIGS. 23A and 23B, the fourth direction d4 and the fifth direction d5 are orthogonal.

[0179] As shown in FIG. 23C, the connecting portion 24 and the support portion 20 may be arranged along a sixth direction d6 and a seventh direction d7 that intersects the sixth direction d6. The sixth direction d6 is a direction non-parallel to the direction in which the end side 1h of the hollow structure film 1 extends. The seventh direction d7 is a direction non-parallel to the direction in which the end side 1h of the hollow structure film 1 extends 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 orthogonal to each other.

[0180] The hollow structure films 1 shown in FIGS. 23A, 23B, and 23C can each be manufactured using a single-sided embossing body 80 having a corresponding shape. FIG. 22D is a perspective view showing the single-sided embossing body 80 used for manufacturing the hollow structure film 1 shown in FIG. 23A. FIG. 23E is a perspective view showing the single-sided embossing body 80 used for manufacturing the hollow structure film 1 shown in FIG. 23B. FIG. 23F is a perspective view showing the single-sided embossing body 80 used for manufacturing the hollow structure film 1 shown in FIG. 23C. In the example shown in FIG. 23D, the convex portion 82 has the shape of a frustum of a square pyramid, particularly a regular frustum of a square pyramid. In the examples shown in FIGS. 23E and 23F, the convex portion 82 has the shape of a frustum of a cone.

[0181] In the examples shown in FIGS. 23D and 23E, the convex portions 82 are arranged along an eighth direction d8, which is one of the extending directions of the end side 805 of the single-sided embossing body 80, and a ninth direction d9 that intersects the eighth direction d8. In the examples shown in FIGS. 23D and 23E, the eighth direction d8 and the ninth direction d9 are orthogonal to each other.

[0182] In the example shown in FIG. 23F, the convex portions 82 are arranged along a tenth direction d10 and an eleventh direction d11 that intersects the tenth direction d10. The tenth direction d10 is a direction non-parallel to the extending direction of the end side 805 of the single-sided embossing body 80. The eleventh direction d11 is a direction non-parallel to the extending direction of the end side 805 of the single-sided embossing body 80 and non-parallel to the tenth direction d10. In the example shown in FIG. 23F, the tenth direction d10 and the eleventh direction d11 are orthogonal to each other.

[0183] The hollow structure film 1 of Modification 8 can also form a hollow structure and suppress the dielectric constant to a low level.

Example

[0184] Next, specific examples of the above-described embodiments and each modification will be described.

[0185] (Example 1) A hollow structure film 1 similar to the hollow structure film 1 shown in FIG. 1 was manufactured except that it did not contain particles 50. At this time, first, a pair of single-sided shaped bodies 80 were produced using a mold 90. At this time, as a peelable base material, Kapton (registered trademark) manufactured by Toray DuPont Co., Ltd. was prepared. Furthermore, as a material for the shaped body corresponding portion 13, a mixture of a resin and an electron beam crosslinking agent was prepared. As the resin, high-density polyethylene raw material pellets (product name "Hifax (registered trademark) 5000SR", manufactured by Prime Polymer Co., Ltd.) were used. As the electron beam crosslinking agent, TAIC (registered trademark) (manufactured by Shinryo Corporation) was used. The ratio of the mass of the resin to the total mass of the mixture was 95% by mass. The ratio of the mass of the electron beam crosslinking agent to the total mass of the mixture was 5% by mass.

[0186] Subsequently, using a mold 90 having a surface 90a with a shape corresponding to the shape of the single-sided shaped body 80 to be produced, the material of the shaped body corresponding portion 13 was molded on the peelable base material. As a result, a pair of single-sided shaped bodies 80 were produced from the material of the shaped body corresponding portion 13. The pair of produced single-sided shaped bodies 80 had a sheet-like base portion 81 and a plurality of convex portions 82 formed on one surface of the base portion 81. The thickness of the single-sided shaped body 80 (the sum of the thickness of the base portion 81 and the dimensions of the convex portions 82 in the thickness direction of the base portion 81) was set to 150 μm.

[0187] Furthermore, a resin sheet 32 to be used as the material for the central portion 30 was produced. As the resin sheet 32, a resin sheet 32 in which an electron beam crosslinking agent is dispersed in the resin and formed into a sheet shape was used. As the material of the resin contained in the resin sheet 32, linear low-density polyethylene raw material pellets (product name "DOWLEX (registered trademark): 2045.11G (C8 copolymerization)", manufactured by Dow Chemical Company) were used. As the electron beam crosslinking agent contained in the resin sheet 32, the same electron beam crosslinking agent as the electron beam crosslinking agent contained in the shaped body corresponding portion 13 was used. 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.

[0188] Subsequently, a pair of laminates including the single-sided shaped body 80 and the peelable base material were overlapped such that a plurality of convex portions 82 of the pair of single-sided shaped bodies 80 faced each other in part. As a result, the pair of single-sided shaped bodies 80 were overlapped such that the plurality of convex portions 82 faced each other in part. At this time, the resin sheet 32 was disposed between the pair of single-sided shaped bodies 80.

[0189] Subsequently, the pair of single-sided shaped bodies 80 were heat-pressed. In particular, by heat-pressing the pair of single-sided shaped bodies 80, the pair of single-sided shaped bodies 80 were joined to the resin sheet 32 at the plurality of convex portions 82. As a result, the pair of single-sided shaped bodies 80 were joined via the resin sheet 32. The heating temperature when heat-pressing the pair of single-sided shaped bodies 80 was made higher than the Vicat softening point of the resin contained in the central portion 30.

[0190] Subsequently, the peelable base material was peeled off from the pair of single-sided shaped bodies 80.

[0191] Subsequently, a crosslinking step was performed in which an electron beam was irradiated onto the electron beam crosslinking agent contained in the single-sided shaped body 80 to react the electron beam crosslinking agent with the resin. The electron beam to be irradiated was an electron beam with an acceleration voltage of 200 kV, a current value of 5 mA, and an irradiation dose of 289 kGy. Further, in the crosslinking step, an electron beam was irradiated onto the electron beam crosslinking agent contained in the resin sheet 32 to react the electron beam crosslinking agent with the resin. More specifically, in the crosslinking step, the electron beam crosslinking agent contained in the single-sided shaped body 80 and the electron beam crosslinking agent contained in the resin sheet 32 were simultaneously irradiated with an electron beam, and the electron beam crosslinking agent and the resin were reacted simultaneously in the single-sided shaped body 80 and in the resin sheet 32. Thereby, the hollow structure film 1 shown in FIG. 1 was manufactured. The ratio of the width w2 to the interval w1 of the hollow structure film 1 shown in FIG. 1 was set to 1:3.

[0192] (Example 2) The hollow structure film 1 was manufactured by the same method 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 convex portion 82 in the thickness direction of the base 81) was set to 120 μm.

[0193] (Example 3) The hollow structure film 1 was manufactured by the same method as in Example 1 except for the following points. A hollow structure film 1 as shown in FIG. 9 was manufactured, in which the base 10 had a plurality of connection portions 24, a first connection portion 24a extending in the first direction d1, and a second connection portion 24b extending in the third direction d3. The third direction d3 in which the second connection portion 24b extended was orthogonal to the first direction d1 in which the first connection portion 24a extended. The ratio of the width w2 to the interval w1 of the hollow structure film 1 was set to 1:10.

[0194] (Example 4) A hollow structure film 1 was produced in the same manner as in Example 1, except for the following points. One of the pair of single-sided shaped bodies 80 was produced as follows. By coextrusion molding, using a mold 90, the material for the metal adjacent layer 60 and the material for the shaped body corresponding part 13 were molded in this order on a peelable base material. The material for the metal adjacent layer 60 was an ethylene-methacrylic acid copolymer (product name "Nuclel (registered trademark) AN4233C", manufactured by Mitsui Dow Polychemical Co., Ltd.). The thickness of the metal adjacent layer 60 was 30 μm. Thus, the metal adjacent layer 60 was produced from the material for the metal adjacent layer 60 on the peelable base material, and the single-sided shaped body 80 was produced from the material for the shaped body corresponding part 13 on the metal adjacent layer 60. In this way, a laminate in which the peelable base material, the metal adjacent layer 60, and the single-sided shaped body 80 were laminated in this order was produced. The laminate produced as described above and the laminate including the single-sided shaped body 80 and the peelable base material produced in the same manner as in Example 1 were overlapped so that a plurality of convex portions 82 of the pair of single-sided shaped bodies 80 faced each other in part. Thus, the pair of single-sided shaped bodies 80 were overlapped so that a plurality of convex portions 82 faced each other in part. Subsequently, the pair of single-sided shaped bodies 80 were heat-bonded. Subsequently, the peelable base material was peeled off from the single-sided shaped body 80 and the metal adjacent layer 60. Thus, a hollow structure film 1 was produced, which corresponded to the one in which the metal adjacent layer 60 was provided on one surface of one of the pair of base portions 10 of the hollow structure film 1 shown in FIG. 1.

[0195] (Example 5) A hollow-structured film 1 was produced in the same manner as in Example 1, except for the following points. As the material for the mold corresponding part 13, a mixture of a resin and an electron beam crosslinking agent was prepared. As the resin contained in the mixture, linear low-density polyethylene raw material pellets (product name "DOWLEX (registered trademark): 2045.11G (C8 copolymerization)", manufactured by Dow Chemical Company) were used. The ratio of the mass of the resin to the total mass of the mixture was 95% by mass. The ratio of the mass of the electron beam crosslinking agent to the total mass of the mixture was 5% by mass. As the resin sheet 32, a sheet made of an ethylene-methacrylic acid copolymer (product name "NUCREL (registered trademark) AN4233C", manufactured by Mitsui Dow Polychemical Co., Ltd.) was used. The resin sheet 32 did not contain the particles 50 and the electron beam crosslinking agent.

[0196] (Example 6) A hollow-structured film 1 was produced in the same manner as in Example 1, except for the following points. As the material for the mold corresponding part 13, a mixture of a resin, the particles 50, and an electron beam crosslinking agent was prepared. As the resin contained in the mixture, linear low-density polyethylene raw material pellets (product name "DOWLEX (registered trademark): 2045.11G (C8 copolymerization)", manufactured by Dow Chemical Company) were used. As the particles 50 contained in the mixture, hollow glass particles (glass particles 51 having a hollow part 52, product name "Sphericel (registered trademark) 25P45", manufactured by Potters Ballotini) were used. The ratio of the mass of the resin to the total mass of the mixture was 85% by mass. The ratio of the mass of the particles 50 to the total mass of the mixture was 10% by mass. The ratio of the mass of the electron beam crosslinking agent to the total mass of the mixture was 5% by mass. As the resin sheet 32, a sheet made of an ethylene-methacrylic acid copolymer (product name "NUCREL (registered trademark) AN4233C", manufactured by Mitsui Dow Polychemical Co., Ltd.) was used. The resin sheet 32 did not contain the particles 50 and the electron beam crosslinking agent.

[0197] (Example 7) A hollow structure film 1 was produced in the same manner as in Example 1, except for the following points. As the material for the shaped body corresponding part 13, a mixture of a resin, particles 50, and an electron beam crosslinking agent was prepared. As the resin contained in the mixture, linear low-density polyethylene raw material pellets (product name "DOWLEX (registered trademark): 2045.11G (C8 copolymerization)", manufactured by The Dow Chemical Company) were used. As the particles 50 contained in the mixture, hollow glass particles (glass particles 51 having a hollow part 52, product name "Sphericel (registered trademark) 25P45", manufactured by Potters Ballotini) were used. The ratio of the mass of the resin to the total mass of the mixture was 75% by mass. The ratio of the mass of the particles 50 to the total mass of the mixture was 10% by mass. The ratio of the mass of the electron beam crosslinking agent to the total mass of the mixture was 15% by mass. As the resin sheet 32, a sheet made of an ethylene-methacrylic acid copolymer (product name "Nuclel (registered trademark) AN4233C", manufactured by Mitsui Dow Polychemical Co., Ltd.) was used. The resin sheet 32 did not contain the particles 50 and the electron beam crosslinking agent.

[0198] (Example 8) A hollow structure film 1 was produced in the same manner as in Example 1, except for the following points. Only one laminate including a one-sided shaped body 80 and a peelable base material was produced. Further, only one laminate including a resin sheet 32 and a peelable base material was produced. The laminate including the one-sided shaped body 80 and the laminate including the resin sheet 32 were arranged such that the resin sheet 32 faced the surface of the one-sided shaped body 80 where a plurality of convex portions 82 were formed. Subsequently, the two layers of the one-sided shaped body 80 and the resin sheet 32 were heat-welded by heat-pressure bonding. Subsequently, the peelable base material was peeled off from the one-sided shaped body 80 and the resin sheet 32. Thus, a hollow structure film 1 corresponding to the one obtained by removing the metal layer 40 and the metal adjacent layer 60 from the hollow structure film 1 shown in FIG. 14 was produced.

[0199] (Example 9) A hollow structure film 1 was produced in the same manner as in Example 1, except for the following points. Four single-sided shaped bodies 80, namely, 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, were produced. Further, three resin sheets 32 were produced. Subsequently, 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 laminated in this order and heat-welded. That is, the four single-sided shaped bodies 80 and the three resin sheets 32 were laminated and heat-welded as shown in FIG. 15. At this time, the surfaces on which a plurality of convex portions 82 were formed of the first single-sided shaped body 80a and the second single-sided shaped body 80b were opposed to each other. The surfaces constituted by the base portions 81 of the second single-sided shaped body 80b and the third single-sided shaped body 80c were opposed to each other. The surfaces on which a plurality of convex portions 82 were formed of the third single-sided shaped body 80c and the fourth single-sided shaped body 80d were opposed to each other. By laminating and heat-welding the four single-sided shaped bodies 80 and the three resin sheets 32 as described above, a hollow structure film 1 corresponding to the one obtained by removing the metal layer 40 and the metal adjacent layer 60 from the hollow structure film 1 shown in FIG. 16 was produced. In the crosslinking step, an electron beam with an irradiation dose of 289 kGy was irradiated from the side of the first single-sided shaped body 80a, and an electron beam with an irradiation dose of 289 kGy was irradiated from the side of the fourth single-sided shaped body 80d.

[0200] (Comparative Example 1) A commercially available polyimide film (product name: "Upilex 125S", manufactured by UBE Industries, Ltd.) was used as the film of Comparative Example 1. The thickness of the film of Comparative Example 1 was 125 μm.

[0201] (Comparative Example 2) A commercially available liquid crystal polymer (product name: "R-F705", manufactured by Panasonic Industry Co., Ltd.) was used as the film of Comparative Example 2. The thickness of the film of Comparative Example 2 was 100 μm.

[0202] (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. As a result, a smooth film-like sample was created. This sample was used as the film of Comparative Example 3. Since the gap during hot pressing was 200 μm, the thickness of the film of Comparative Example 3 was 200 μm.

[0203] (1) Porosity measurement test Next, a porosity measurement test was conducted on the hollow structure films 1 of Examples 1 to 9. In the porosity measurement test, an image of a cross-section obtained by cutting the hollow structure film 1 through a plurality of support portions 20 and on a plane perpendicular to the first direction d1 was acquired by a scanning electron microscope (SEM). On the acquired image, the above-described straight line L2 and straight line L3 were drawn. Subsequently, the ratio of the area of the hollow portion B to the entire area of the hollow structure film 1 including the hollow portion B between the straight line L2 and the straight line L3 was calculated. The ratio was calculated at 10 different locations of the cross-section. By averaging the ratios calculated at the 10 different locations, the porosity of the hollow structure film 1 was obtained. Originally, the porosity of Comparative Examples 1 to 3 that do not have the hollow portion B was set to 0.

[0204] (2) Specific gravity measurement test Next, a measurement test of specific gravity (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, a square sample with a side length of 100 mm was cut out from the hollow structure film 1 of each example and the film of each comparative example. Subsequently, the mass of the sample was measured. Furthermore, the thickness of the sample was measured. The thickness of the sample was measured by the following method. Using a device combining a Nikon digital micrometer head MF-501 and a counter MFC-200, the thickness at 16 points in the plane of the sample was measured on a surface plate. Each measurement point was 3 cm apart from each other. The average of the thicknesses at 16 points in the plane was taken as the thickness of the sample. The volume of the sample was calculated by multiplying the thickness by the square of the length of one side (100 mm) of the sample. From the measured mass and the calculated volume, the specific gravity of the hollow structure film 1 of each example and each comparative example was calculated.

[0205] (3) Measurement Test of Dielectric Constant and Dielectric Loss Tangent Next, a measurement test of dielectric constant and dielectric loss tangent was conducted on the hollow structure films 1 of Examples 1 to 9 and the films of Comparative Examples 1 to 3. In the measurement test of dielectric constant and dielectric loss tangent, as a measuring device, a measuring device using the cavity resonance method (product name: "S-parameter network analyzer 8722ES", manufactured by Agilent Technologies, Inc.), a cavity resonator, and a program CPMA-V2 installed on a notebook PC were used to measure the dielectric constant and dielectric loss tangent by the following method. A rectangular sample with a short side of 2 mm and a long side of 100 mm was cut out from the hollow structure film 1 of each example and the film of each comparative example. Subsequently, the measuring device was started up. Then, the sample was inserted into the cavity of the cavity resonator of the measuring device from one side of the short side, and the dielectric constant and dielectric loss tangent of the sample were measured. The measurement of the dielectric constant and dielectric loss tangent of the same sample was performed 3 times, and the average value of the 3 measurement results was used as the measured value of the dielectric constant and dielectric loss tangent. Furthermore, as a value serving as an index for comparing the magnitudes of transmission losses (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.

[0206] (4) Heat resistance evaluation test Next, a heat resistance evaluation test was carried out 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 a long side of 20 mm and a short side of 2 mm were cut out from the hollow structure films 1 of each example and the films of each comparative example. The sample was placed on a glass substrate so that the long side was placed on the glass substrate by 10 mm, and fixed to the glass substrate using a tape (product name: "Kapton (registered trademark) adhesive tape #12", manufactured by Teraoka Seisakusho Co., Ltd.). Subsequently, the sample was heated by placing it in an oven heated to 290°C for 90 seconds while being fixed to the glass substrate. At this time, the sample was positioned above the surface of the glass substrate. Subsequently, the sample after heating was observed visually to evaluate whether the sample was deformed after heating and the degree of deformation after heating. If no deformation was observed, it was evaluated as "○"; if slight deformation (such as warping of the sample, where the protruding part from the glass substrate of the sample did not droop and break, and the part fixed to the glass substrate of the sample and the protruding part from the glass substrate were maintained in a connected state) was observed, it was evaluated as "△"; if severe deformation (such as the protruding part from the glass substrate of the sample completely drooping, resulting in the sample breaking between the part fixed to the glass substrate and the protruding part from the glass substrate) was observed, it was evaluated as "×".

[0207] (5) Evaluation test of adhesion of copper foil Next, an evaluation test of the adhesion to copper foil was conducted on the hollow structure films 1 of Examples 1 to 9 and the films of Comparative Examples 1 to 3. In the evaluation test of the adhesion to copper foil, an evaluation test of the resistance to the load of copper foil was conducted by the following method. From the hollow structure film 1 of each example and the film of each comparative example, a rectangular sample with a long side of 100 mm and a short side of 20 mm was cut out. The sample was placed on a copper foil (thickness 10 μm, product name "CF-LB9-10", purchased from Takizawa Co., Ltd.). The copper foil had the same size as the sample. That is, the copper foil used had a rectangular shape with a long side of 100 mm and a short side of 20 mm. The copper foil and the sample were placed on the copper foil such 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. Further, a material for the metal adjacent layer (thickness 30 μm, product name "Nucrel (registered trademark) AN4233C", manufactured by Mitsui Dow Chemical Co., Ltd.) was placed between the sample and the copper foil. Subsequently, the portion where the sample, the material for the metal adjacent layer, and the copper foil overlapped was heat-pressed at 100 °C. The pressure-bonded portion was formed at the end of the sample. In the pressure-bonded portion, a laminate in which the sample, the metal adjacent layer, and the copper foil were laminated in this order was formed. The portion of the sample not pressure-bonded to the copper foil and the portion of the copper foil not pressure-bonded to the sample were formed over a length of 80 mm in the long side direction of the sample and the copper foil. In this way, the sample was joined to the copper foil. Subsequently, the adhesion to the copper foil was evaluated by the following method. As a test apparatus, a force tester MCT-2150 manufactured by A&D Co., Ltd. with a pair of parallel clamping type jaws for 500 N set in the vertical direction was prepared. Subsequently, the portion of the sample not pressure-bonded to the copper foil was set in one chuck of the pair of parallel clamping type jaws. Further, the portion of the copper foil not pressure-bonded to the sample was set in one chuck of the pair of parallel clamping type jaws. Subsequently, by separating one and the other of the pair of parallel clamping type jaws at a speed of 5 N / min, a load was applied to the joint surface where the sample and the copper foil were joined, and it was observed whether peeling occurred at the joint surface between the sample and the copper foil.Furthermore, when peeling occurred, the peeling force at the time of peeling (the load applied to the bonding surface between the sample and the copper foil when peeling occurred) was measured. If peeling did not occur or the peeling force at the time of peeling was greater than 10 N / 20 mm, it was evaluated as "○", and if the peeling force at the time of peeling was 10 N / 20 mm or less, it was evaluated as "×".

[0208] In addition, in the evaluation test of the adhesion of the copper foil, the evaluation test of the etchant resistance was carried out by the following method. A laminate in which a sample, a metal adjacent layer, and a copper foil were laminated in this order was formed by the same method as in the evaluation test of the resistance of the copper foil to load, except that a sufficiently large sample, a metal adjacent layer, and a copper foil were used so that the step of cutting out the laminate sample described later could be performed. That is, in the same manner as in the evaluation test of the resistance of the copper foil to load, a metal adjacent layer was disposed between the sample and the copper foil and heat-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 (product name "Elec Masking N-300", manufactured by Nitto Denko Corporation) with a side length of 5 mm was attached to the center of the surface of this laminate sample constituted by the copper foil. After that, the laminate sample was put into a 1 L glass beaker containing an aqueous ferric chloride solution heated to 50 °C (concentration: 40%, Baume degree at 15 °C: 42 Baume, manufactured by Wako Pure Chemical Industries, Ltd.) to perform an etching treatment for 5 minutes. After that, the laminate sample was washed twice with distilled water at room temperature for 1 minute. Subsequently, the laminate sample was dried. Then, the masking tape was peeled off from the laminate sample, and the condition of the copper foil remaining unetched under the masking tape was observed. After peeling off the masking tape, if the copper foil remained in the shape of a square with a side length of 5 mm and there was no visible peeling or lifting on the copper foil, it was evaluated as "○", and if there was visible lifting at the edge of the copper foil or peeling of the copper foil, it was evaluated as "×".

[0209] (6) Evaluation test of dynamic viscoelasticity Next, an evaluation test of the dynamic viscoelasticity when the temperature of the samples became high was conducted on the hollow structure films 1 of Examples 1 to 9 and the films of Comparative Examples 1 to 3. In the evaluation test of the dynamic viscoelasticity, a dynamic viscoelasticity (DMA) measuring device (product name "RSA-G2") manufactured by TA Instruments Japan Co., Ltd. was prepared. The mode of the dynamic viscoelasticity measuring device was set to the tensile mode. Also, rectangular samples with a short side of 5 mm were cut out from the hollow structure films 1 of each example and the films of each comparative example. Subsequently, the distance between a pair of chucks of the dynamic viscoelasticity measuring device was opened by 10 mm. Then, one short side of the sample was set on one of the pair of chucks, and the other short side of the sample was set on the other of the pair of chucks. Subsequently, while changing the temperature of the sample from 30°C to 300°C, the measurement of the dynamic viscoelasticity was carried out. The heating rate was set to 5°C / min. In the measurement of the dynamic viscoelasticity, a stress that changes with time was applied to the sample, and the frequency of the change in the stress was set to 1 Hz. Thereby, the storage elastic modulus of the sample was measured particularly when the temperature of the sample was 280°C.

[0210] The results of the measurement test of the porosity, the measurement test of the specific gravity, the measurement test of the dielectric constant and the dielectric loss tangent, the evaluation test of the heat resistance, the evaluation test of the adhesion of the copper foil, and the evaluation test of the dynamic viscoelasticity for the hollow structure films 1 of Examples 1 to 9 are shown in Table 1. Additionally, the results of the measurement test of the specific gravity, the measurement test of the dielectric constant and the dielectric loss tangent, the evaluation test of the heat resistance, the evaluation test of the adhesion of the copper foil, and the evaluation test of the dynamic viscoelasticity for the films of Comparative Examples 1 to 3 are shown in Table 1.

[0211]

Table 1

[0212] From the results shown in Table 1, it was found that in any of Examples 1 to 9, the dielectric constant, dielectric tangent, and transmission loss coefficient were smaller than those in Comparative Examples 1 to 3. Furthermore, it was found that in any of Examples 1 to 9, the heat resistance, resistance to the load of the copper foil, and etchant resistance were evaluated as "○". Furthermore, in any of Examples 1 to 9, the storage elastic modulus was found to be 1.0×10 5 Pa or more.

[0213] Furthermore, in order to evaluate the performance of the antenna device 101 manufactured using the hollow structure film 1 and the transmission loss in the hollow structure film 1, the hollow structure films 1 of Examples 10 to 11 and the films of Comparative Examples 4 to 6 were prepared.

[0214] (Example 10) Except for the following points, the portion of the main body 1c of the hollow structure film 1 as shown in FIG. 16 was manufactured by the same method as in Example 9. The thickness of the main body 1c was 800 μm. Furthermore, two copper foils (thickness 18 μm, product name "C1100 electrolytic copper foil 18 μm", purchased from Baosen Co., Ltd.) and two materials for the metal adjacent layers (thickness 30 μm, product name "Nucrel (registered trademark) AN4233C", manufactured by Mitsui Dow Chemical Co., Ltd.) were prepared. Subsequently, the copper foil, the material for the metal adjacent layer, the main body 1c, the material for the metal adjacent layer, and the copper foil were stacked and arranged in this order. Subsequently, the copper foil, the material for the metal adjacent layer, the main body 1c, the material for the metal adjacent layer, and the copper foil were heat-pressed at 100°C. As a result, a hollow structure film 1 including a metal layer 40 formed from a copper foil, a metal adjacent layer 60, a main body 1c, a metal adjacent layer 60, and a metal layer 40 formed from a copper foil in this order as shown in FIG. 16 was manufactured.

[0215] (Example 11) A hollow structure film 1 was produced in the same manner as in Example 10, except for the following points. A hollow structure film 1 having a configuration corresponding to Modification 4 was created. More specifically, a hollow structure film 1 as shown in FIG. 14 was created. First, in the same manner as in Example 10, a single-sided shaped body 80 and a single resin sheet 32 were produced. The thickness of the single-sided shaped body 80 (the sum of the thickness of the base portion 81 and the dimension of the convex portion 82 in the thickness direction of the base portion 81) was set to 150 μm. The thickness of the resin sheet 32 was set to 50 μm. Subsequently, the resin sheet 32 was arranged so as to face the surface of the single-sided shaped body 80 on which a plurality of convex portions 82 were formed. The single-sided shaped body 80 and the resin sheet 32 were heat-bonded. In the crosslinking step after the heat-bonding, the single-sided shaped body 80 and the resin sheet 32 were irradiated with an electron beam having an acceleration voltage of 200 kV, a current value of 5 mA, and an irradiation dose of 289 kGy. Thereby, the main body portion 1c of the hollow structure film 1 as shown in FIG. 14 was produced. Further, two copper foils (thickness 18 μm, product name "C1100 electrolytic copper foil 18 μm", purchased from Takizawa Co., Ltd.) were prepared. Subsequently, an olefin resin-based adhesive was applied to one side of each of the two copper foils. The application amount of the adhesive was adjusted so that the thickness after drying of the adhesive would be 2 μm. Subsequently, the main body portion 1c was arranged between the two copper foils. At this time, the main body portion 1c was arranged between the two copper foils so that the surface of the copper foil coated with the adhesive and the surface of the main body portion 1c faced each other. Subsequently, the two copper foils and the main body portion 1c were heat-bonded under the conditions of 100 °C for 2 minutes. Further, the heat-bonded copper foil and the main body portion 1c were annealed by storing them in an oven at 80 °C for 36 hours. Thereby, a hollow structure film 1 including a metal layer 40 formed of a copper foil, a metal adjacent layer 60 formed of an adhesive, a main body portion 1c, a metal adjacent layer 60 formed of an adhesive, and a metal layer 40 formed of a copper foil in this order as shown in FIG. 14 was produced.

[0216] (Comparative Example 4) A commercially available PTFE substrate (product name "RO3003 (registered trademark)", manufactured by Rogers) was purchased and used as the film of Comparative Example 4. The thickness of the PTFE substrate was 800 μm. Copper foils with a thickness of 18 μm were provided on both sides of the PTFE substrate.

[0217] (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 foils with a thickness of 18 μm were provided on both sides of the glass epoxy resin film.

[0218] (Comparative Example 6) Two commercially available LCP films (product name "R-F705", manufactured by Panasonic Industry Co., Ltd.) were purchased. The thickness of the LCP film was 100 μm. Copper foils with a thickness of 18 μm were provided on one side of the LCP film. Further, a commercially available bonding sheet (product name "R-BM17", manufactured by Panasonic Industry Co., Ltd.) was purchased. The thickness of the bonding sheet was 25 μm. Subsequently, 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 to the surface where the copper foil was provided faced the surface of the bonding sheet. Subsequently, the two LCP films and the bonding sheet were joined by bonding process. Thereby, the film of Comparative Example 6 was produced. The thickness of the film of Comparative Example 6 was 225 μm. Copper foils with a thickness of 18 μm, derived from the copper foils provided on the LCP film, were provided on both sides of the film of Comparative Example 6.

[0219] (7) Evaluation Test of Antenna Performance Next, the antenna device 101 was fabricated from the films of Example 10 and Comparative Example 4, and an evaluation test of the antenna performance was conducted on the fabricated antenna device 101. In fabricating the antenna device 101, a wiring pattern of wiring 41 and an antenna element 102 having a desired shape were formed from the metal layer 40 that constitutes one surface of the hollow structure film 1 of each example or the film of each comparative example, thereby manufacturing the antenna device 101 as shown in FIG. 6C. The process of forming the wiring pattern of wiring 41 and the antenna element 102 having a desired shape from the metal layer 40 was carried out as follows. First, a weakly adhesive sheet was bonded to the surface of the metal layer 40. Subsequently, the weakly adhesive sheet was cut, and a part was removed leaving a part, thereby forming a mask layer having a shape corresponding to the shape of the wiring pattern of the wiring 41 and the antenna element 102 to be formed. Subsequently, the metal layer 40 was etched using the mask layer. Thereby, the antenna device 101 as shown in FIG. 6C was manufactured. In Example 10, the dimension w7 (width of the wiring 41) of the wiring 41 shown in FIG. 6C was set to 3.2 mm. The dimension w8 (length of the wiring 41) of the wiring 41 shown in FIG. 6C was set to 17.0 mm. The dimension w9 of the antenna element 102 shown in FIG. 6C was set to 25.0 mm. The dimension w10 (length of the wiring 41) of the antenna element 102 shown in FIG. 6C was set to 30.0 mm. As shown in FIG. 6C, a pair of slit structures 102b were provided at the portion where the antenna element 102 was connected to the wiring 41. The pair of slit structures 102b extended in the extending direction of the wiring 41. An interval 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 set to 11.0 mm. The dimension w14 (width of the slit structure 102b) of the slit structure 102b shown in FIG. 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 devices 101 of Example 10 and Comparative Example 4 as described above, a virtual antenna device in which the dimensions such as w7, w8, w9, w10, w13, and w14 were the same as those of the antenna device 101 of Example 10 was simulated.Furthermore, a virtual antenna device in which dimensions such as dimensions w7, w8, w9, w10, w13, and w14 are the same as those of the antenna device of Comparative Example 4 was simulated. Subsequently, the S11 parameter (input reflection coefficient) when a 3.9 GHz electrical signal was applied to the antenna element of a virtual antenna device having dimensions the same as those of the antenna device 101 of Example 10 and a virtual antenna device having dimensions the same as those of the antenna device of Comparative Example 4 was calculated. As a result, the S11 parameters of the virtual antenna device having dimensions the same as those of the antenna device 101 of Example 10 and the virtual antenna device having dimensions the same as those of the antenna device of Comparative Example 4 were both -33.5 dB. From this, it was confirmed that the setting of the dimensions of the antenna device 101 in Example 10 and Comparative Example 4 is an appropriate setting for comparing the gain and beam width of the antenna device 101 between Example 10 and Comparative Example 4, as described later.

[0220] In the antenna performance evaluation test, a virtual antenna device that radiates radio waves with equal intensity in all directions was simulated using a network analyzer. At this time, the virtual antenna was regarded as a point without volume. Then, the virtual antenna device, which is a point without volume, was placed on the turntable 95 as shown in the antenna device 101 of FIG. 24 described later, and the intensity of the radio wave received by the receiving antenna 96 when a 3.9 GHz electrical signal was applied to the antenna element was calculated.

[0221] Furthermore, as shown in FIG. 24, a turntable 95 rotatable about a rotation axis C1 extending vertically was disposed within the anechoic chamber R. Further, a receiving antenna 96 capable of receiving radio waves emitted by the antenna device 101 was disposed at a position within the anechoic chamber R that was 3 m away from the rotation axis C1 of the turntable 95 in the horizontal direction. Subsequently, the fabricated antenna device 101 was fixed to a jig (not shown) and then disposed at a position on the turntable 95 within the anechoic chamber R through which the rotation axis C1 passed. At this time, the antenna device 101 was disposed on the turntable 95 such that the side 102a shown in FIG. 6C of the antenna element 102 faced the receiving antenna 96. In other words, the antenna device 101 was disposed on the turntable 95 such that the receiving antenna 96 was positioned in the direction of arrow A1 of the antenna device 101 shown in FIG. 6C. The antenna device 101 was fixed to the jig such that the jig was electrically connected to the wiring 41.

[0222] Subsequently, an electrical signal was applied from a network analyzer to the antenna element 102 of the antenna device 101 via a jig (not shown) to cause 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. Subsequently, the frequency of the electrical signal applied to the antenna element 102 was changed to identify the frequency at which the intensity of the radio waves received by the receiving antenna 96 was maximized. From the value of the intensity of the radio waves received by the receiving antenna 96 at the frequency at which the intensity of the radio waves received by the receiving antenna 96 was maximized, the difference obtained by subtracting the intensity of the radio waves calculated as described above for the virtual antenna device that was a point without the above-described volume was calculated. This difference was taken as the gain of the antenna device 101. The unit of the gain of the antenna device 101 calculated by the above calculation is dBi.

[0223] Furthermore, while applying an electrical signal of the frequency at which the intensity of the radio wave received by the receiving antenna 96 is maximized, which is specified in calculating the gain, to the antenna element 102, the antenna equipment 101 was rotated by rotating the turntable. When performing such an operation, the intensity of the radio wave received by the receiving antenna 96 is considered to take the maximum value 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 increases from the position where the side 102a of the antenna element 102 faces the receiving antenna 96. While rotating the antenna equipment 101, the intensity of the radio wave detected by the receiving antenna 96 was measured. From the measured intensity of the radio wave, the difference was calculated by subtracting the intensity of the radio wave calculated as described above for the virtual antenna equipment that is the point without volume described above. It is considered that this difference value also changes as the rotation angle of the antenna equipment 101 changes. Regarding the magnitude of the change in the rotation angle for which the decrease from the maximum value of the difference value is within the range of 3 dBi, the beam width (unit: °) was calculated.

[0224] A method for calculating the beam width in a specific example will be described. In a specific example, when the antenna equipment 101 is rotated clockwise from the position where the side 102a of the antenna element 102 faces the receiving antenna 96 by an angle of 30° or less, the decrease from the maximum value of the intensity of the radio wave detected by the receiving antenna 96 becomes 3 dBi or less. In a specific example, when the antenna equipment 101 is rotated counterclockwise from the position where the side 102a of the antenna element 102 faces the receiving antenna 96 by an angle of 30° or less, the decrease from the maximum value of the intensity of the radio wave detected by the receiving antenna 96 becomes 3 dBi or less. At this time, the beam width is calculated to be 60°.

[0225] (8) Transmission loss evaluation test Next, an evaluation test of transmission loss was conducted on the films provided with the metal layer 40 of Example 11 and Comparative Examples 5 to 6. In the evaluation test of transmission loss, first, a linear wiring 43 having a desired shape as shown in FIG. 6A was 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. The method of forming the linear wiring 43 having a desired shape from the metal layer 40 was the same as the method of forming the wiring pattern of the wiring 41 having a desired shape and the antenna element 102 from the metal layer 40, which was described in the "(7) Evaluation Test of Antenna Performance". The length w5 of the linear wiring 43 shown in FIG. 6A was set to 5.0 cm. The width w6 of the linear wiring 43 shown in FIG. 6A was set to 0.75 mm.

[0226] The hollow structure film 1 provided with the linear wiring 43 was fixed to a jig 93 (product name "Universal Test Fixture 3680V") as shown in FIG. 6B, and an electric signal was applied via a probe 94 attached to the jig 93 from a network analyzer (product name "N5247A", manufactured by Keysight Technologies, Inc.), and the transmission loss of the electric signal was measured. The measurement of the transmission loss of the electric signal was performed under the following conditions. The electric signal was applied to a section corresponding to a length of 5.0 cm of the linear wiring 43. At the time of measurement, in order to remove the influence of the jig 93 from the measurement result, the de-embedding process described in the above-described embodiment was performed. By the de-embedding process, a value corresponding to the transmission loss measured by applying an electric signal to a section of 3.5 cm in length of the linear wiring 43, from which the influence of the transmission loss at both end portions of the linear wiring 43 and the jig 93 was removed, was calculated.

[0227] The results of the evaluation test of antenna performance for the hollow structure film 1 of Example 10 and the film of Comparative Example 4, and the results of the evaluation test of transmission loss for the hollow structure film 1 of Example 11 and the films of Comparative Examples 5 to 6 are shown in Table 2.

[0228]

Table 2

[0229] From the evaluation test of antenna performance and the evaluation test of transmission loss, the following was found. The hollow structure film 1 of this case shows more excellent performance than a commercially available PTFE substrate generally expected to have high antenna performance and an LCP film generally expected to reduce transmission loss (bring the value of transmission loss with a negative value closer to zero). In particular, it was found that the hollow structure film 1 of this case can suppress the transmission loss, which tends to increase and become a problem in the antenna device 101 used in the high-frequency band, to a small value (bring the value of transmission loss with a negative value closer to zero). Furthermore, it became clear that the antenna device 101 using the hollow structure film 1 of this case shows excellent antenna performance compared to the antenna device using the conventional film due to the action of the hollow structure film 1 described above.

[0230] Furthermore, as a modification example 6, in order to evaluate the porosity, dielectric constant, dielectric tangent, CTE of the main body portion 1c, and the ease of peeling of the copper foil from the main body portion 1c when the copper foil and the main body portion 1c are joined, the hollow structure films 1 of Examples 12 to 14 and the film of Comparative Example 7 were prepared.

[0231] (Example 12) A hollow structure film 1 similar to the hollow structure film 1 shown in FIG. 17 was manufactured. At this time, first, a pair of single-sided shaped bodies 80 were produced using a mold 90. At this time, as a peelable base material, Kapton (registered trademark) manufactured by Toray DuPont Co., Ltd. was prepared. Furthermore, as a material for the shaped body corresponding portion 13, a mixture of a resin and an electron beam crosslinking agent was prepared. As the resin, high-density polyethylene raw material pellets (product name "Hizex (registered trademark) 5000SR", manufactured by Prime Polymer Co., Ltd.) were used. The resin corresponds to high-density polyethylene (HDPE). As the electron beam crosslinking agent, TAIC (registered trademark) (manufactured by Shinryo Corporation) was used. 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.

[0232] Subsequently, using a mold 90 having a surface 90a with a shape corresponding to the shape of the single-sided shaped body 80 to be produced, the material of the shaped-body corresponding portion 13 was molded on a peelable base material. As a result, a pair of single-sided shaped bodies 80 were produced from the material of the shaped-body corresponding portion 13. When molding the material of the shaped-body corresponding portion 13, a sheet-like inorganic material member 70 was disposed on the upper side of a mixture of a resin and an electron beam crosslinking agent, and then molding was performed. During molding, the mixture of the resin and the electron beam crosslinking agent and the inorganic material member 70 were press-processed. By this press-processing, a part of the material derived from the mixture of the resin and the electron beam crosslinking agent moved to the upper side of the inorganic material member 70 through the inside of the inorganic material member 70. As a result, a pair of single-sided shaped bodies 80 as shown in FIG. 19, in which the sheet-like inorganic material member 70 is included in the base portion 81, were produced. In particular, a pair of single-sided shaped bodies 80 having a base portion 81 including the sheet-like inorganic material member 70 and the material derived from the mixture of the resin and the electron beam crosslinking agent surrounding the periphery of the inorganic material member 70 were produced. As the sheet-like inorganic material member 70, a glass cloth (product name: "LU1017:L01Z (vinyl silane treatment)", manufactured by Unitika Ltd.) was used. The pair of produced single-sided shaped bodies 80 had a sheet-like base portion 81 and a plurality of convex portions 82 formed on one surface of the base portion 81. The thickness of the single-sided shaped body 80 (the sum of the thickness of the base portion 81 and the dimensions of the convex portions 82 in the thickness direction of the base portion 81) was set to 150 μm.

[0233] Furthermore, a resin sheet 32 to be the material of the central portion 30 was produced. As the resin sheet 32, a resin sheet 32 in which a resin material was formed in a sheet shape was used. As the resin material included in the resin sheet 32, linear low-density polyethylene raw material pellets (product name: "DOWLEX (registered trademark): 2045.11G (C8 copolymerization)", manufactured by Dow Chemical Company) were used. The resin corresponds to linear low-density polyethylene (LLDPE). The thickness of the resin sheet 32 was set to 50 μm.

[0234] Subsequently, a pair of laminates including the single-sided embossing body 80 and a peelable base material were overlapped such that a plurality of convex portions 82 of the pair of single-sided embossing bodies 80 faced each other partially. As a result, the pair of single-sided embossing bodies 80 were overlapped such that the plurality of convex portions 82 faced each other partially. At this time, the resin sheet 32 was disposed between the pair of single-sided embossing bodies 80.

[0235] Subsequently, the pair of single-sided embossing bodies 80 were heat-pressed. In particular, by heat-pressing the pair of single-sided embossing bodies 80, the pair of single-sided embossing bodies 80 were joined to the resin sheet 32 at the plurality of convex portions 82. Thereby, the pair of single-sided embossing bodies 80 were joined via the resin sheet 32. The heating temperature when heat-pressing the pair of single-sided embossing bodies 80 was made higher than the Vicat softening point of the resin contained in the central portion 30.

[0236] Subsequently, the peelable base material was peeled off from the pair of single-sided embossing bodies 80.

[0237] Subsequently, a cross-linking step was performed in which an electron beam was irradiated to the electron beam cross-linking agent contained in the single-sided embossing body 80 and the resin contained in the single-sided embossing body 80 to react the electron beam cross-linking agent with the resin. The electron beam to be irradiated was an electron beam with an acceleration voltage of 200 kV, a current value of 5 mA, and an irradiation dose of 289 kGy. Further, in the cross-linking step, an electron beam was irradiated to the resin contained in the resin sheet 32 to react the resin. More specifically, in the cross-linking step, an electron beam was simultaneously irradiated to the electron beam cross-linking agent and resin contained in the single-sided embossing body 80 and the resin contained in the resin sheet 32. As a result, the electron beam cross-linking agent and the resin were reacted in the single-sided embossing body 80, and at the same time, the resin was reacted in the resin sheet 32. Thereby, the hollow structure film 1 shown in FIG. 17 was manufactured. The ratio of the width w2 to the interval w1 of the hollow structure film 1 was set to 1:3.

[0238] (Example 13) A hollow-structured film 1 was produced in the same manner as in Example 12, except for the following points. In Example 13, a hollow-structured film 1 similar to the one shown in FIG. 18 was produced. In Example 13, when molding the material of the form body corresponding portion 13, the sheet-shaped inorganic material member 70 was not placed inside the mixture of the resin and the electron beam crosslinking agent. In Example 13, when molding the material of the form body corresponding portion 13, a plurality of rod-shaped inorganic material members 70 were placed inside the mixture of the resin and the electron beam crosslinking agent and then molding was performed. When producing the pair of single-sided form bodies 80, the addition amount of the rod-shaped inorganic material member 70 was 30% by mass in terms of the mass ratio to the total mass of the resin, the electron beam crosslinking agent, and the inorganic material member 70. As a result, a pair of single-sided form bodies 80 in which the rod-shaped inorganic material member 70 is included in all of the base portion 81 and the plurality of convex portions 82 as shown in FIG. 20 were produced. In Example 13, when molding the resin sheet 32 into a sheet shape, a plurality of rod-shaped inorganic material members 70 were placed inside the mixture of the resin, which is the material of the resin sheet 32, and the electron beam crosslinking agent and then molding was performed. When producing the resin sheet 32, the addition amount of the rod-shaped inorganic material member 70 was 30% by mass in terms of the mass ratio to the total mass of the resin, the electron beam crosslinking agent, and the inorganic material member 70. As the rod-shaped inorganic material member 70, glass fiber (product name "SS05DE-413SP", manufactured by Nitto Boseki Co., Ltd.) was used. As a result, a resin sheet 32 containing the rod-shaped inorganic material member 70 as shown in FIG. 20 was produced. Using the pair of single-sided form bodies 80 and the resin sheet 32 produced as described above, the hollow-structured film 1 shown in FIG. 18 was produced.

[0239] (Example 14) A hollow-structured film 1 was produced in the same manner 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 member 70. Regarding the mixture of the resin and the electron beam crosslinking agent used as the material of the form 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% by mass. When producing a pair of single-sided form bodies 80, the addition amount of the scaly inorganic material member 70 was 40% by mass in terms of the mass ratio to the total mass of the resin, the electron beam crosslinking agent, and the inorganic material member 70. As the scaly inorganic material member 70, the product name "REF015A" (manufactured by Nippon Sheet Glass Co., Ltd.) was used.

[0240] (Comparative Example 7) A film in which an electron beam crosslinking agent was dispersed in a resin and formed into a sheet shape was produced and used as the film of Comparative Example 7. As the resin material contained in the film of Comparative Example 7, high-density polyethylene raw material pellets (product name "Hizex (registered trademark) 5000SR", manufactured by Prime Polymer Co., Ltd.) were used. The resin corresponds to high-density polyethylene (HDPE). As the electron beam crosslinking agent contained in the film of Comparative Example 7, TAIC (registered trademark) (manufactured by Shinryo Corporation) was used. 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.

[0241] (9) Measurement test of porosity Next, a measurement test of porosity was performed on the hollow-structured films 1 of Examples 12 to 14. The measurement test of porosity was carried out in the same manner as the "(1) Measurement test of porosity" regarding the hollow-structured films 1 of Examples 1 to 9. Originally, the porosity of Comparative Example 7 having no hollow portion B was set to 0.

[0242] (10) Measurement test of dielectric constant and dielectric loss tangent Next, a measurement test of the dielectric constant and the dielectric loss tangent was performed on the hollow structure film 1 of Examples 12 to 14 and the film of Comparative Example 7. The measurement test of the dielectric constant and the dielectric loss tangent was conducted by the same method as the “(3) Measurement test of the dielectric constant and the dielectric loss tangent” for the hollow structure film 1 of Examples 1 to 9 and the films of Comparative Examples 1 to 3.

[0243] (11) Measurement test of CTE Next, a CTE measurement test was conducted on the hollow structure film 1 of Examples 12 to 14 and the film of Comparative Example 7. In the CTE measurement test, the CTE of the main body portion 1c of the hollow structure film 1 of Examples 12 to 14 and the film of Comparative Example 7 was measured. The CTE measurement was performed by the following method. As a measurement device, a thermomechanical analyzer (product name "TMA-60", manufactured by Shimadzu Corporation) was used. First, from the hollow structure film 1 of Examples 12 to 14 and the film of Comparative Example 7, a rectangular sample 97 as shown in FIG. 25, with a short side 972 of 5 mm and a long side 971 of 14 mm, was cut out. A region with a width w15 of 2 mm in the extending direction of the long side 971, with one end being the short side 972 of the sample 97, is referred to as the chucking region 98. The sample 97 has a pair of chucking regions 98, namely the first chucking region 981 and the second chucking region 982. An intermediate region 99 with a width w16 of 10 mm in the extending direction of the long side 971 is formed between the first chucking region 981 and the second chucking region 982. In the CTE measurement, the first chucking region 981 was fixed to the first jig by sandwiching the entire first chucking region 981 with the first jig. Further, the second chucking region 982 was fixed to the second jig by sandwiching the entire second chucking region 982 with the second jig. Subsequently, a load of 3.0 g was applied to the intermediate region 99 of the sample 97 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 way, the sample 97, the first jig, and the second jig were placed inside the temperature control chamber. Subsequently, the temperature inside the temperature control chamber was once set to 10°C. After that, the temperature inside the temperature control chamber was heated at a rate of 10°C / min, and the elongation amount of the intermediate region 99 of the sample 97 in the extending direction of the long side 971 was measured. At this time, in particular, the width w16 of the intermediate region 99 when the temperature inside the temperature control chamber reached 25°C and the width w16 of the intermediate region 99 when the temperature inside the temperature control chamber reached 75°C were measured. From the above measurement results, the elongation rate of the width w16 of the intermediate region 99 was calculated in parts per million (ppm) when the temperature inside the temperature control chamber was raised from 25°C to 75°C.The value obtained by dividing this elongation rate by 50 (°C) corresponds to the elongation rate of Sample 97 when the temperature is increased by 1 °C. This value was determined as the CTE (ppm / °C) value.

[0244] (12) Evaluation test for ease of copper foil peeling Next, an evaluation test for ease of copper foil peeling was conducted on the hollow structure films 1 of Examples 12 to 14 and the film of Comparative Example 7. In the evaluation test for ease of copper foil peeling, rectangular samples with a long side of 50 mm and a short side 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. Onto the sample, a material for the metal adjacent layer (thickness 30 μm, product name "Nucrel (registered trademark) AN4233C", manufactured by Mitsui Dow Polychemical Co., Ltd.) and a copper foil (thickness 10 μm, product name "CF-LB9-10", purchased from Takizawa Co., Ltd.) were laminated in this order so as to cover the entire sample. Subsequently, the portion where the sample, the material for the metal adjacent layer, and the copper foil overlapped was heat-pressed at 100 °C. The pressure-bonded portion was formed over the entire sample. Subsequently, the pressure-bonded portion was left in a room at room temperature of 25 °C for 48 hours. Whether peeling of the copper foil from the sample occurred during heat-pressing or during leaving in the room was observed.

[0245] 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 measurement tests for dielectric constant, dielectric loss tangent, CTE measurement test, and the evaluation test for ease of copper foil peeling for the hollow structure films 1 of Examples 12 to 14 and the film of Comparative Example 7 are shown in Table 3.

[0246]

Table 3

[0247] From the results shown in Table 3, it was found that in any of Examples 12 to 14, the dielectric constant was smaller than that of Comparative Example 7. It was also found that in any of Examples 12 to 14, the CTE was smaller than that of Comparative Example 7. It was found that in any of Examples 12 to 14, the CTE was 120 ppm / °C or less. Furthermore, in any of Examples 12 to 14, in the evaluation test of the ease of peeling of the copper foil, no peeling of the copper foil from the sample occurred.

[0248] It is also possible to appropriately combine a plurality of constituent elements disclosed in the above embodiments and each modification as needed. Alternatively, some constituent elements may be deleted from all the constituent elements shown in the above embodiments and each modification.

Description of Reference Numerals

[0249] 1 Hollow structure film 1a First surface 1b Second surface 10 Base 20 Support pillar portion 30 Central portion 40 Metal layer 50 Particles 51 Glass particles 60 Metal adjacent layer 80 One-sided shaped body 81 Base 82 Protrusion 90 Mold 100 Circuit board 101 Antenna equipment

Claims

1. In a hollow structure film having a hollow structure, 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 facing surface facing the second base portion, the second base portion has a second facing surface facing the first base portion, at least a part of the plurality of support portions constitutes continuous support portions extending from the first facing surface to the second facing 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 facing surface and the second facing surface, the plurality of support portions are located on the first facing surface side and the second facing surface side of the central portion, the hollow structure film according to Claim 1.

4. The hollow structure film according to Claim 1, having a thickness of 50 μm or more and 1000 μm or less.

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. The hollow structure film according to Claim 1, containing glass particles.

8. The glass particles have a hollow portion, the hollow structure film according to Claim 7.

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

10. The hollow structure film according to Claim 1, having a porosity of 20% or more.

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

12. Further provided is a metal adjacent layer that joins the metal layer and at least one of the first base portion and the second base portion. The hollow structure film according to claim 11, 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 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.

14. 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. The hollow structure film according to claim 11, wherein at least one of the conditions is satisfied.

15. A circuit board comprising: a 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.

16. A circuit board according to claim 15; and an antenna element connected to the circuit board. An antenna device comprising the same.

17. 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 portion and a plurality of convex portions formed on one surface of the base portion; and a step of overlapping the pair of produced single-sided shaped bodies such that at least a part of the plurality of convex portions face each other and performing heat-pressure bonding. A method for manufacturing a hollow structure film comprising the same.

Images