JP2024022568A - Radio wave aggregation film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radio wave aggregation film capable of improving receivable radio wave intensity when taking, into a room, radio waves of a wide frequency band of several hundred MHz or more and a high frequency band such as millimeter waves.

SOLUTION: A radio wave aggregation film 1 includes: a light transmissive film-like base material 10; and a mesh-like antenna layer 20 provided on one surface side 10a of the base material 10. The antenna layer 20 is a dipole antenna side 20A and used by being stuck to a window or a wall.

SELECTED DRAWING: Figure 1

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present invention relates to a radio wave concentrating film.

The Internet of Things (IoT) field is expected to grow due to ultra-high-speed communication through fifth generation mobile communication systems (hereinafter referred to as "5G"). In order to realize ultra-high-speed communication using 5G, it is necessary to secure a wide frequency band of several hundred MHz or more. However, in the low frequency bands that have been used in mobile communication systems to date, it is difficult to secure the bandwidth necessary to realize ultra-high-speed communication. Therefore, in 5G, technology has been developed to realize ultra-high-speed communication in high frequency bands that have not been used before. As a result, a radio access technology called New Radio (NR) has been standardized to enable support for wide frequency bands of hundreds of MHz or higher and high frequency bands such as millimeter waves, which are necessary for high-speed, large-capacity communications. Ta.

However, the higher the frequency band, the more direct the emitted radio waves will be, and if there is an obstacle, it will not only be impossible to go backwards, but the range that the radio waves can reach will be narrower. Therefore, there are restrictions on where the receiver can be installed indoors. Furthermore, when bringing radio waves from an outdoor base station indoors, the strength of the radio waves decreases.

As an antenna for bringing radio waves from an outdoor base station indoors, for example, a film antenna that is attached to a window glass or the like is known (see, for example, Patent Document 1). This film antenna includes a base material formed in a sheet shape, a mesh-like first antenna layer provided on the base material and having light-shielding properties and conductivity, and a mesh-like first antenna layer provided on the base material and having light-shielding properties and conductivity. A second antenna layer having a mesh shape. The second antenna layer transmits or receives radio waves of a different frequency from that of the first antenna layer, and the first antenna layer overlaps the second antenna layer when viewed from the normal direction of the base material.

Patent No. 6761591

However, the antenna of Patent Document 1 has a problem in that it is not possible to improve the strength of the radio waves that can be received when taking radio waves in a wide frequency band of several hundred MHz or more or a high frequency band such as millimeter waves into a room.

The present invention has been made in view of the above circumstances, and is capable of improving the strength of radio waves that can be received when bringing radio waves in a wide frequency band of several hundred MHz or more or a high frequency band such as millimeter waves into a room. The purpose is to provide radio wave concentrating films.

The present invention has the following aspects.
[1] A light-transmissive film-like base material,
a mesh antenna layer provided on one surface of the base material,
the antenna layer is a dipole antenna;
A radio wave concentrating film that is used by pasting it on windows or walls.
[2] The dipole antenna includes two radiating sections facing each other, a circuit section connected to each of the radiating sections, and a circuit section connected to each of the circuit sections and provided on the opposite side from the radiating section. The radio wave concentrating film according to [1], comprising a power feeding section and a discharge section extending along the length direction of the circuit section.
[3] The radio wave concentrating film according to [2], wherein the length of the radiating element of the antenna layer is 10 μm or more and 200 mm or less.
[4] The radio wave concentrating film according to [1], wherein the antenna layer is for high frequency transmission and reception.
[5] The radio wave concentrating film according to [1], wherein the base material has a dielectric constant of 3.5 or less.
[6] The radio wave concentrating film according to [1], comprising an adhesive layer provided on the other surface of the base material.
[7] The radio wave concentrating film according to [1], comprising a protective layer covering the antenna layer.

According to the present invention, it is possible to provide a radio wave concentrating film that can improve the strength of radio waves that can be received when bringing radio waves in a wide frequency band of several hundred MHz or more or a high frequency band such as millimeter waves into a room.

FIG. 1 is a plan view showing a radio wave concentrating film according to an embodiment of the present invention. 1 is a cross-sectional view showing a radio wave concentrating film according to an embodiment of the present invention, and is a cross-sectional view taken along line AA in FIG. 1. FIG. 2 is a plan view showing a radio wave concentrating film according to an embodiment of the present invention, and is an enlarged view of the region indicated by α in FIG. 1. FIG.

Hereinafter, a radio wave concentrating film that is an embodiment of the present invention will be described in detail. Note that the drawings used in the following explanations may show characteristic parts enlarged for convenience in order to make the characteristics easier to understand, and the dimensional ratio of each component may not be the same as the actual one. do not have.

[Radio wave concentrating film]
FIG. 1 is a plan view showing a radio wave concentrating film according to an embodiment of the present invention. FIG. 2 is a sectional view showing a radio wave concentrating film according to an embodiment of the present invention, and is a sectional view taken along line AA in FIG. FIG. 3 is a plan view showing a radio wave concentrating film according to an embodiment of the present invention, and is an enlarged view of the area indicated by α in FIG.
The radio wave concentrating film 1 of this embodiment includes a base material 10 and an antenna layer 20 provided on one surface 10a of the base material 10. In FIGS. 1 to 3, one surface 10a of the base material 10 is the upper surface of the base material 10. As shown in FIG. The radio wave concentrating film 1 of this embodiment is used by being attached to a window or a wall.

"Base material"
The base material 10 is a light-transmissive film-like base material.
The light transmittance (transparency) of the base material 10 is preferably higher when the radio wave concentrating film 1 is attached to a window. In this case, the base material 10 preferably has a light transmittance of 70% or more, more preferably 80% or more according to JIS K7105-1981. Note that the light transmittance can be measured, for example, with a turbidimeter manufactured by Nippon Denshoku Industries Co., Ltd. (product number: NDH2000).
Further, the haze value of the base material 10 according to JIS K7136 is preferably 10% or less, more preferably 8% or less, and even more preferably 6% or less.

The material constituting the base material 10 is not particularly limited as long as it is optically transparent, but examples thereof include polyethylene terephthalate (PET), polybutylene terephthalate, polyethylene naphthalate, terephthalic acid-isophthalic acid-ethylene glycol copolymer, and terephthalic acid. - Polyester resins such as cyclohexanedimethanol-ethylene glycol copolymer, polyamide resins such as nylon 6, polyolefin resins such as polypropylene, polymethylpentene, and cycloolefin polymers, acrylic resins such as polymethyl methacrylate, polystyrene, Examples include styrene resins such as styrene-acrylonitrile copolymer, cellulose resins such as triacetylcellulose, imide resins, polycarbonate resins, and polynorbornene resins. These resins may be used alone or in combination of two or more. The material constituting the base material 10 is preferably one that can lower the dielectric constant of the base material 10. By using polynorbornene resin, the dielectric constant of the base material 10 can be lowered and the electromagnetic wave permeability of the base material 10 can be improved.

The base material 10 may be a laminate in which films made of the above-mentioned materials are laminated via an adhesive resin or heat-sealed. When the base material 10 is a laminate, the number of layers is not particularly limited, and is appropriately adjusted depending on the location where the radio wave concentrating film 1 is attached.

As the adhesive resin, for example, acrylic adhesive, urethane adhesive, ether adhesive, ester adhesive, etc. are used.

The resin constituting the base material 10 may contain additives such as a filler, a plasticizer, and an antistatic agent, as necessary.

Even if the surface of the base material 10 has been subjected to a known adhesion treatment such as corona discharge treatment, plasma treatment, ozone treatment, flame treatment, primer treatment, preheating treatment, dust removal treatment, vapor deposition treatment, alkali treatment, etc. good.

The dielectric constant of the base material 10 is preferably 3.5 or less, more preferably 3 or less, and even more preferably 2.5 or less. When the dielectric constant of the base material 10 is below the upper limit value, the dielectric constant of the base material 10 can be lowered and the electromagnetic wave permeability of the base material 10 can be improved.

The dielectric loss tangent of the base material 10 is preferably 0.1 or less, more preferably 0.01 or less, and even more preferably 0.001 or less. When the dielectric constant of the base material 10 is below the upper limit value, conductive loss can be reduced.

The thickness of the base material 10 is not particularly limited, but is preferably, for example, 10 μm or more and 200 μm or less, more preferably 20 μm or more and 150 μm or less. If the thickness of the base material 10 is within the above range, the mechanical strength will be sufficient and warping, loosening, breakage, etc. will be suppressed.

[Antenna layer]
The antenna layer 20 is provided on one surface 10a of the base material 10. Further, the antenna layer 20 has a mesh shape on one surface 10a of the base material 10.

The antenna layer 20 is a dipole antenna 20A. The dipole antenna 20A includes a pair of radiating parts 21 and 22 facing each other, circuit parts 23 and 24 connected to each of the radiating parts 21 and 22, and a pair of radiating parts 21 and 22 connected to each of the circuit parts 23 and 24, respectively. It has power supply parts 25, 26, 27 provided on the opposite side to 22, and a discharge part 28 extending along the length direction of the circuit parts 23, 24. Hereinafter, the radiation part 21 is the first radiation part 21, the radiation part 22 is the second radiation part 22, the circuit part 23 is the first circuit part 23, the circuit part 24 is the second circuit part 24, and the power feeding part 25 is the first power feeding part. 25, the power feeding section 26 is sometimes referred to as a second power feeding section 26, and the power feeding section 27 is sometimes referred to as a third power feeding section 27.

The antenna layer 20, that is, the dipole antenna 20A is for high frequency transmission and reception. Here, high frequency refers to radio waves with a frequency of 20 GHz to 10 THz.
The first radiation section 21 and the second radiation section 22 are opposed to each other. The first radiating section 21 and the second radiating section 22 extend in a band shape from opposing surfaces to opposite sides, respectively.

The length L1 of the first radiating section 21 and the length L2 of the second radiating section 22 are equal. The sum of the length L1 of the first radiating section 21 and the length L2 of the second radiating section 22 is half the wavelength of the high frequency wave (radio wave) received by the dipole antenna 20A. Therefore, the length L1 of the first radiating section 21 and the length L2 of the second radiating section 22 are 1/4 of the wavelength of the high frequency (radio wave) received by the dipole antenna 20A.
The length L1 of the first radiation part 21 and the length L2 of the second radiation part 22 are preferably 10 μm or more and 200 mm or less, and more preferably 15 μm or more and 100 mm or less. When the length L1 of the first radiating section 21 and the length L2 of the second radiating section 22 are within the above range, the dipole antenna 20A can receive high frequency waves.

The width W1 of the first radiating section 21 and the length W2 of the second radiating section 22 are equal. The width W1 of the first radiating section 21 and the length W2 of the second radiating section 22 are adjusted appropriately according to the length L1 of the first radiating section 21 and the length L2 of the second radiating section 22, but are not less than 5 μm. It is preferably 100 mm or less, and more preferably 10 μm or more and 50 mm or less.

The first circuit section 23 is connected to the first radiation section 21 . Here, the first circuit section 23 extends in a belt shape in a direction substantially perpendicular to the direction in which the first radiation section 21 extends.
The second circuit section 24 is connected to the second radiation section 22. Here, the second circuit section 24 extends in a belt shape in a direction substantially perpendicular to the direction in which the second radiation section 22 extends.
The discharge section 28 extends in a strip shape along the first circuit section 23 and the second circuit section 24.

The width W3 of the first circuit section 23 is preferably 2 μm or more and 200 mm or less.
The width W4 of the second circuit portion 24 is preferably 2 μm or more and 200 mm or less.
The width W5 of the discharge portion 28 is preferably 2 μm or more and 200 mm or less.

The distance D1 between the first circuit section 23 and the second circuit section 24 is preferably 2 μm or more and 10 mm or less, and more preferably 2.2 μm or more and 8 mm or less.
The distance D2 between the second circuit section 24 and the discharge section 28 is preferably 2 μm or more and 10 mm or less, and more preferably 2.2 μm or more and 8 mm or less.

The first power feeding section 25 is connected to the first circuit section 23 and is provided on the opposite side from the first radiation section 21 .
The second power feeding section 26 is connected to the second circuit section 24 and is provided on the opposite side from the second radiation section 22.
The third power feeding section 27 is connected to the discharge section 28 and is provided on the opposite side from the first radiating section 21 and the second radiating section 22.

The length L3 of the first power feeding section 25 is preferably 100 μm or more and 5 mm or less, more preferably 120 μm or more and 4.8 mm or less. The width W6 of the first power feeding section 25 is preferably 100 μm or more and 5 mm or less, and more preferably 120 μm or more and 4.8 mm or less.
The length L4 of the second power feeding section 26 is preferably 100 μm or more and 5 mm or less, more preferably 120 μm or more and 4.8 mm or less. The width W7 of the second power feeding section 26 is preferably 100 μm or more and 5 mm or less, more preferably 120 μm or more and 4.8 mm or less.
The length L5 of the third power feeding section 27 is preferably 100 μm or more and 5 mm or less, more preferably 120 μm or more and 4.8 mm or less. The width W8 of the third power feeding section 27 is preferably 100 μm or more and 5 mm or less, more preferably 120 μm or more and 4.8 mm or less.

The thickness of the antenna layer 20, that is, the thickness of the radiation parts 21, 22, the circuit parts 23, 24, the feeding parts 25, 26, 27, and the discharge part 28, is not particularly limited, but is, for example, 1 μm or more and 500 μm or less. It is preferably 1.2 μm or more and 200 μm or less. If the thickness of the antenna layer 20 is within the above range, the mechanical strength will be sufficient and warpage, slack, breakage, etc. will be suppressed.

As shown in FIG. 1, the radiation sections 21 and 22, the circuit sections 23 and 24, and the discharge section 28 form a mesh. Further, the power feeding sections 25, 26, and 27 have a rectangular shape. As shown in FIG. 3, the radiation sections 21, 22, the circuit sections 23, 24, and the discharge section 28 have a mesh-like (honeycomb-like) shape in which rectangular antenna opening areas 29 are spread out without gaps. Specifically, the antenna aperture regions 29 are arranged at a constant pitch in the first direction a1 and the second direction a2, which intersect with each other. That is, the antenna aperture area 29 includes a plurality of antenna conductors 30 each extending linearly in the first direction a1 and arranged at a constant pitch P1 in a direction perpendicular to the first direction a1, and each extending in the second direction a2. It is defined by a plurality of antenna conducting wires 30 that extend linearly in a direction perpendicular to the second direction a2 and are arranged at a constant pitch P2 that is the same as the constant pitch P1. As a result, the antenna opening regions 29 included in the radiation sections 21 and 22, the circuit sections 23 and 24, and the discharge section 28 are all formed in the same square shape (diamond shape).

In order for the antenna layer 20 to have optical transparency, the width (wire diameter) d of the antenna conducting wire 30 defining the antenna aperture region 29 is preferably 0.1 μm or more and 100 μm or less, and 0.5 μm. More preferably, the thickness is 30 μm or less. When the wire diameter d of the antenna conducting wire 30 is equal to or larger than the lower limit value, current loss when receiving radio waves is reduced. Moreover, if the wire diameter d of the antenna conducting wire 30 is less than or equal to the above-mentioned upper limit, the transparency will be reduced and the antenna will be easily recognized.

Further, the size of the antenna aperture region 29, that is, the interval (pitch) P1 between the antenna conductive wires 30 that define the antenna aperture region 29 is preferably 20 μm or more and 5000 μm or less, more preferably 100 μm or more and 2000 μm or less. preferable. When the pitch P1 of the antenna conducting wire 30 is equal to or greater than the lower limit value, the opening becomes wider and transparency becomes higher. When the pitch P1 of the antenna conducting wire 30 is equal to or less than the upper limit value, a current flow path width can be ensured.

Further, it is preferable that the mesh-like radiation parts 21 and 22, the circuit parts 23 and 24, and the discharge part 28 have an aperture ratio ε defined by the following formula (1) of 60% or more and 99% or less, More preferably, it is 80% or more and 99% or less. When the porosity ratio ε is equal to or greater than the lower limit value, transparency can be ensured. When the aperture ratio ε is equal to or less than the upper limit value, a current flow path width can be ensured.

ε=(P1/(P1+d)) ² ×100 (1)
(However, P1 is the pitch of the antenna conducting wire, and d is the width (wire diameter) of the antenna conducting wire.)

The first power feeding portion 25, the second power feeding portion 26, and the third power feeding portion 27 are planar conductive portions that do not have an antenna opening area as described above and are entirely made of a conductive material.

The material constituting the antenna layer 20 is not particularly limited, and examples thereof include copper, gold, silver, aluminum, and the like.

[Adhesive layer]
The radio wave concentrating film 1 of this embodiment may include an adhesive layer 40 provided on the other surface 10b of the base material 10.
The radio wave concentrating film 1 may be attached to a window or wall using the adhesive layer 40.

The thickness of the adhesive layer 40 is preferably 1 μm or more and 30 μm or less, more preferably 5 μm or more and 20 μm or less. When the thickness of the adhesive layer 40 is within the above range, the radio wave concentrating film 1 can be firmly attached to a window or a wall.

The adhesive layer 40 is not particularly limited as long as it can firmly adhere the radio wave concentrating film 1 to a window or wall and has sufficient transparency. Examples of the material constituting the adhesive layer 40 include polyurethane resins such as polyurethane ester resins and two-part curable urethane resins, acrylic resins, polyester resins, epoxy resins, and silicone resins. Further, the adhesive layer 40 may be of an ultraviolet curing type, a thermosetting type, or a non-curing type.

[Protective layer]
The radio wave concentrating film 1 of this embodiment may include a protective layer 50 that covers the antenna layer 20.

The thickness of the protective layer 50 is preferably 2 μm or more and 100 μm or less, more preferably 5 μm or more and 50 μm or less. When the thickness of the protective layer 50 is equal to or greater than the lower limit, the circuit can be sufficiently covered. When the thickness of the protective layer 50 is less than or equal to the upper limit, radio wave transparency can be sufficiently ensured.

The protective layer 50 is not particularly limited as long as it can protect the antenna layer 20 and has sufficient transparency. Examples of the material constituting the protective layer 50 include epoxy resin and acrylic resin such as polymethyl methacrylate.

Next, an example of a method for manufacturing the radio wave concentrating film 1 will be described.
First, a material constituting the adhesive layer 40 is applied to the other surface 10b of the base material 10 so that the adhesive layer 40 has a predetermined thickness. In order to protect the obtained adhesive layer 40, a release sheet is attached to the surface of the adhesive layer 40 opposite to the surface that contacts the base material 10.
Next, a conductive foil for forming the antenna layer 20 is attached to the entire surface of one surface 10a of the base material 10. As the conductive foil, for example, one made of copper, gold, silver, aluminum, etc. is used.
Next, the pattern of the dipole antenna 20A described above is formed on the conductive foil attached to the entire surface of one surface 10a of the base material 10 by etching.
Next, a protective layer 50 is attached onto the antenna layer 20 to cover the antenna layer 20 with the protective layer 50. The protective layer 50 may be attached onto the antenna layer 20 via an adhesive layer, or may be heat-sealed onto the antenna layer 20.
Through the above steps, the radio wave concentrating film 1 is obtained.

A method of using the radio wave concentrating film 1 of this embodiment will be explained.
The radio wave concentrating film 1 is used by being attached to, for example, the indoor side of a window or the outdoor side of a wall.
Further, a receiver is connected to the radio wave aggregation film 1, which can extract information from the received radio waves as needed. The radio wave concentrating film 1 and the receiver may be connected by wire via wiring, or a transmitter may be provided on the radio wave concentrating film 1 and wirelessly connected via the transmitter.
When the antenna layer 20 of the radio wave concentrating film 1 attached to a window or wall receives high-frequency radio waves, the received radio wave signal is sent to a receiver, and the information contained in the signal is extracted as necessary. .

According to the radio wave concentrating film 1 of the present embodiment, the antenna layer 20 is provided with a mesh-like antenna layer 20 provided on one surface 10a of the light-transmitting film-like base material 10, and the antenna layer 20 is a dipole antenna 20A. Since it is used by being attached to a window or wall, it is possible to improve the strength of the radio waves that can be received when bringing radio waves in a wide frequency band of several hundred MHz or higher or a high frequency band such as millimeter waves into a room.

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.

[Examples 1 to 10]
(Preparation of radio wave concentrating film)
A radio wave concentrating film as shown in FIG. 1 was produced in the following manner.
An aluminum film was deposited on a PET base material having an average thickness of 0.1 mm so that the average thickness was 0.05 μm to produce an aluminum-PET base material laminate.
A photosensitive film mask for forming an antenna with each dimension (L1 to L5, W1 to W8, D1, D2) shown in Table 1 shown in FIG. 1 is attached to the surface of the aluminum film of the aluminum-PET base material laminate. Combined.
Next, the aluminum film was subjected to exposure patterning and development treatment to form the aluminum film into a mesh antenna layer to obtain the radio wave concentrating films of Examples 1 to 10.
Table 1 also shows the width d of the antenna conducting wire forming the mesh antenna layer, the pitch P1 of the antenna conducting wire, and the aperture ratio ε.

[Comparative example]
A radio wave concentrating film of a comparative example was obtained in the same manner as in the example except that no antenna opening area was provided.

[evaluation]
(Peak frequency measurement)
A plane wave generated by connecting a horn antenna to a network analyzer (model name: N5251A, manufactured by Keysight Technologies) is irradiated onto the radio wave concentrating films of the examples and comparative examples, and the standing wave ratio (generally VSWR (Voltage Standing Wave Ratio)) is measured. ) was measured. Receivable frequencies were compared, with the frequency at which the VSWR value was lowest as the peak frequency. The results are shown in Table 1.

(Evaluation of transparency)
The transmittance of the radio wave concentrating films of Examples and Comparative Examples was evaluated. A case in which the background could be seen through the antenna layer was evaluated as having transparency, and was evaluated as "〇", and a case in which the antenna layer could be clearly seen was evaluated as "x", indicating that the background was insufficiently transparent. The results are shown in Table 1.

As shown in Table 1, by appropriately setting the lengths L1 and L2 of the radiation part of the antenna layer (dipole antenna), it is possible to receive radio waves in a wide frequency band of several hundred MHz or more and high frequency bands such as millimeter waves. It has become clear that a radio wave concentrating film can be obtained.

INDUSTRIAL APPLICABILITY The present invention can be used to receive radio waves indoors in a wide frequency band of several hundred MHz or higher, or in a high frequency band such as millimeter waves.

1 Radio wave concentrating film 10 Base material 20 Antenna layer 21 First radiation part (radiation part)
22 Second radiation part (radiation part)
23 First circuit section (circuit section)
24 Second circuit section (circuit section)
25 First power feeding section (power feeding section)
26 Second power supply section (power supply section)
27 Third power supply section (power supply section)
28 Discharge section 29 Antenna opening area 30 Antenna conducting wire 40 Adhesive layer 50 Protective layer

Claims (7)

a light-transparent film-like base material,
a mesh antenna layer provided on one surface of the base material,
the antenna layer is a dipole antenna;
A radio wave concentrating film that is used by pasting it on windows or walls. The dipole antenna includes two radiating parts facing each other, a circuit part connected to each of the radiating parts, and a feeding part connected to each of the circuit parts and provided on the opposite side of the radiating part. The radio wave concentrating film according to claim 1, further comprising: a discharge section extending along the length direction of the circuit section. The radio wave concentrating film according to claim 2, wherein the length of the radiation portion is 10 μm or more and 200 mm or less. The radio wave concentrating film according to claim 1, wherein the antenna layer is for high frequency transmission and reception. The radio wave concentrating film according to claim 1, wherein the base material has a dielectric constant of 3.5 or less. The radio wave concentrating film according to claim 1, further comprising an adhesive layer provided on the other surface of the base material. The radio wave concentrating film according to claim 1, further comprising a protective layer covering the antenna layer.

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