Waveguide and antenna element

Abstract

The present invention addresses the problem of providing a waveguide having a small transmission loss and providing an antenna element using the waveguide. A waveguide according to the present invention comprises: a support substrate; a first surface-side spacer disposed on one surface side of the support substrate and having a through groove; a signal conductor layer disposed on the one surface side of the support substrate and disposed in the through groove; and a first surface-side ground conductor layer disposed on the reverse side of the first surface-side spacer from the support substrate and disposed apart from the signal conductor layer, and satisfies the relations of expression (1) (A × 1.2 < B) and expression (2) (B < A × 3.0) where A is the width of the signal conductor layer, and B is the width of the through groove.

Description

Waveguides, antenna elements

[0001] The present invention relates to a waveguide and an antenna element.

[0002] In recent years, with the widespread use of high frequency signals such as microwaves in wireless communications, there has been a demand for improved performance of waveguides that transmit high frequency signals in electronic devices.

[0003] As a technology related to waveguides, Patent Document 1 discloses a technology relating to a laminated stripline resonator that includes a pair of first dielectric layers on which a ground conductor film is formed and a second dielectric layer having a stripline conductor arranged between the first dielectric layers, and that has a gap provided at the interface between at least one of the pair of first dielectric layers and the stripline conductor.

[0004] Japanese Patent Application Laid-Open No. 2002-141715

[0005] As a result of studying waveguides used for transmitting electromagnetic waves, the present inventors have found that waveguides manufactured with reference to the method described in Patent Document 1 have large transmission loss and that there is room for further improvement in transmission loss.

[0006] In view of the above circumstances, an object of the present invention is to provide a waveguide with low transmission loss, and an antenna element using the waveguide.

[0007] As a result of extensive research into the above-mentioned problems, the present inventors have found that the above-mentioned problems can be solved by the following configuration.

[0008] [1] A waveguide comprising: a support substrate; a first-surface-side spacer having a through groove and disposed on one surface side of the support substrate; a signal conductor layer disposed on one surface side of the support substrate and disposed in the through groove; and a first-surface-side ground conductor layer disposed on the opposite side of the first-surface-side spacer from the support substrate and spaced apart from the signal conductor layer, wherein the relationship between the below-described formulas (1) and (2) is satisfied, where A is the width of the signal conductor layer and B is the width of the through groove. [2] The waveguide according to [1], further comprising: a second-surface-side spacer having a through groove and disposed on the other surface side of the support substrate; and a second-surface-side ground conductor layer disposed on the opposite side of the second-surface-side spacer from the support substrate, wherein the through groove of the first-surface-side spacer and the through groove of the second-surface-side spacer are aligned in the surface direction. [3] The waveguide according to [1] or [2], having the signal conductor layer with a line length of 100 mm or more. [4] The waveguide according to any one of [1] to [3], wherein the dielectric loss tangent of the first-surface side spacer is 0.1 or less at a temperature of 25°C and a frequency of 10 GHz. [5] The waveguide according to any one of [1] to [4], wherein the first-surface side spacer contains a (meth)acrylic resin. [6] The waveguide according to any one of [1] to [5], which is used for transmitting electromagnetic waves having a frequency of 3 to 30 GHz. [7] An antenna element using the waveguide according to any one of [1] to [6]. [8] The antenna element according to [7], wherein the first-surface side ground conductor layer has an opening.

[0009] According to the present invention, a waveguide with low transmission loss can be provided, and an antenna element using the waveguide can be provided.

[0010] Fig. 1 is a cross-sectional view schematically showing an example of the configuration of a waveguide of the present invention. Fig. 2 is a cross-sectional view schematically showing an example of the configuration of a waveguide of the present invention. Fig. 3 is a cross-sectional view schematically showing another example of the configuration of a waveguide of the present invention. Fig. 4 is a cross-sectional view schematically showing another example of the configuration of a waveguide of the present invention. Fig. 5 is a plan view schematically showing an example of the configuration of an antenna element. Fig. 6 is a plan view schematically showing the configuration of a mold used to form a first surface side spacer.

[0011] The waveguide of the present invention will be described in detail below with reference to the drawings. The following description of the components is based on a representative embodiment of the present invention, and the present invention is not limited to such an embodiment. Furthermore, the drawings are merely examples for explaining the present invention, and the present invention is not limited by the drawings shown below. In each drawing, the scale of the components has been appropriately changed from the actual scale to make it easier to see and explain.

[0012] As used herein, "the same" includes a generally accepted error range in the technical field. Furthermore, as used herein, terms such as "all," "all," and "the entire surface" include not only 100% but also generally accepted error ranges in the technical field, such as 99% or more, 95% or more, or 90% or more. Regarding angles, "orthogonal" or "vertical" refers to a range of 90°±5°, and "parallel" refers to a range of 0°±5°. Similarly, unless otherwise specified, angles refer to angles within a range of 5 degrees or less from the exact angle. The difference in the above angles is preferably within 4 degrees, more preferably within 3 degrees. As used herein, "main surface" refers to the surface with the largest area on a plate-, sheet-, or film-like member. As used herein, numerical ranges expressed using "to" refer to a range that includes the numerical values ​​before and after "to" as the lower and upper limits. As used herein, when two or more components are present, the "content" of a component refers to the total content of those two or more components. In this specification, "(meth)acrylate" is a general term including acrylate and methacrylate, and means "at least one of acrylate and methacrylate."

[0013] [Waveguide] The waveguide of the present invention comprises a support substrate, a first-surface-side spacer arranged on one surface side of the support substrate and having a through groove, a signal conductor layer arranged on one surface side of the support substrate and arranged in the through groove, and a first-surface-side ground conductor layer arranged on the opposite side of the first-surface-side spacer from the support substrate and arranged spaced apart from the signal conductor layer, and satisfies the relationships of formulas (1) and (2) described below, where A represents the width of the signal conductor layer and B represents the width of the through groove.

[0014] 1 and 2 are cross-sectional views schematically illustrating an example of the configuration of a waveguide according to the present invention. The waveguide 1 shown in FIG. 1 is composed of a support substrate 10, a first-surface spacer 11, a signal conductor layer 13, a first-surface ground conductor layer 14, and a support substrate 15. The first surface S1 and the second surface S2 of the waveguide 1 are both major surfaces of the waveguide 1, with the support substrate 15 disposed on the outermost surface on the first surface S1 side and the support substrate 10 disposed on the outermost surface on the second surface S2 side. The first-surface spacer 11 has a through groove 12 formed therein, penetrating the two major surfaces of the first-surface spacer 11, and a signal conductor layer 13 disposed within the through groove 12. As illustrated, the signal conductor layer 13 is in contact with the surface of the support substrate 10 facing the first-surface spacer 11 and is spaced apart from the first-surface ground conductor layer 14.

[0015] 2 is a cross-sectional view schematically illustrating the cross section of the waveguide 1 taken along line X-X in FIG. 1. As shown in the figure, the signal conductor layer 13 is disposed at the center of the short side of the waveguide 1 and extends in a strip-like shape along a direction parallel to the long side of the waveguide 1. The through groove 12 of the first-surface spacer 11 is disposed at the center of the short side of the waveguide 1 and has an elongated rectangular shape that extends along the direction in which the signal conductor layer 13 extends. The waveguide 1 has a microstrip line structure in which the signal conductor layer 13 and the first-surface ground conductor layer 14 are spaced apart from each other, and thus functions as a transmission line that transmits electromagnetic waves along the direction in which the signal conductor layer 13 extends.

[0016] The waveguide of the present invention is characterized in that, when the width of the signal conductor layer is A and the width of the through groove is B, the following relationships of formulas (1) and (2) are satisfied: Formula (1) A×1.2<B Formula (2) B<A×3.0 In this specification, the width A of the signal conductor layer refers to the distance between two sides of the signal conductor layer in a plane parallel to the main surfaces (first surface and second surface) of the waveguide, along the direction in which the signal conductor layer extends. Furthermore, the width B of the through groove refers to the distance between two sides of the through groove in a plane parallel to the main surfaces of the waveguide, along the direction in which the through groove extends. The detailed mechanism by which the width A of the signal conductor layer and the width B of the through groove satisfy the relationships of formulas (1) and (2) to solve the problems of the present invention has not been clarified, but the inventors speculate as follows. First, in the waveguide of the present invention, the interior of the through groove between the signal conductor layer and the first-surface-side ground conductor layer is occupied by air, which has a low dielectric constant, thereby suppressing loss of electromagnetic waves transmitted through the signal conductor layer. Furthermore, when the width A of the signal conductor layer and the width B of the through groove satisfy the relationship of formula (1) (when the width B of the through hole is more than 1.2 times the width A of the signal conductor layer), the signal conductor layer is positioned at a predetermined distance from the first-surface-side spacer. This narrows the area where the electric field around the signal conductor layer overlaps with the first-surface-side spacer, thereby reducing transmission loss. Furthermore, when the width A of the signal conductor layer and the width B of the through groove satisfy the relationship of formula (2) (when the width B of the through hole is less than three times the width A of the signal conductor layer), distortion of the signal conductor layer is suppressed. This suppresses deviation of the impedance of the signal line from its design value, thereby reducing transmission loss.

[0017] The waveguide of the present invention is not limited to the embodiments shown in Figures 1 and 2. The waveguide may have a second-surface-side spacer having a through groove arranged on the other surface side of the support substrate, and a second-surface-side ground conductor layer arranged on the opposite side of the second-surface-side spacer from the support substrate. Here, the other surface of the support substrate means the surface of the support substrate opposite to the side on which the signal conductor layer and the first-surface-side spacer are arranged.

[0018] FIG. 3 is a cross-sectional view schematically illustrating another example of the configuration of a waveguide according to the present invention. The waveguide 2 shown in FIG. 3 is composed of a support substrate 10, a first-surface spacer 11 having a through groove 12, a signal conductor layer 13, a first-surface ground conductor layer 14, a support substrate 15, a second-surface spacer 21, a second-surface ground conductor layer 24, and a support substrate 25. The components of the waveguide 2 shown in FIG. 3 that are identical in function and operation to those of the waveguide 1 shown in FIG. 1 are not described here. In the waveguide 2, the support substrate 15 is disposed on the outermost surface on the first surface S1 side, and the support substrate 25 is disposed on the outermost surface on the second surface S2 side. The second-surface spacer 21 has a through groove 22 formed therein, penetrating the two main surfaces of the second-surface spacer. Note that no signal conductor layer is disposed within the through groove 22. As shown in the figure, in the thickness direction of the waveguide 2, a through groove 12 is arranged between the signal conductor layer 13 and the first-surface-side ground conductor layer 14, and a support substrate 10 and a through groove 22 are arranged between the signal conductor layer 13 and the second-surface-side ground conductor layer 24. The waveguide 2 shown in Fig. 3 has such a stripline structure, and thus can further reduce transmission loss when transmitting electromagnetic waves, compared to the waveguide 1 shown in Fig. 1 in which a ground conductor layer is arranged only on one surface side of the signal conductor layer.

[0019] 3, the through groove 12 of the first-surface-side spacer 11 and the through groove 22 of the second-surface-side spacer 21 are aligned in the planar direction. Here, "the through groove 12 and the through groove 22 are aligned in the planar direction" means that the width B, length, and shape of the through groove 12 of the first-surface-side spacer 11 in a plane parallel to the main surface of the waveguide are the same as the width B, length, and shape of the through groove 22 of the second-surface-side spacer 21 in the same plane, and that the position of the through groove 12 in the same plane is the same as the position of the through groove 22 in the same plane. Therefore, when viewed from a direction perpendicular to the main surface of the waveguide 2, the through groove 12 of the first-surface-side spacer 11 and the through groove 22 of the second-surface-side spacer 21 completely overlap. In the waveguide having the second-surface-side spacer and the second-surface-side ground conductor layer, the through groove of the second-surface-side spacer does not have to coincide with the through groove of the first-surface-side spacer in the plane, and it is preferable that they at least partially overlap. In particular, by having the through grooves on both surface sides of the signal conductor layer coincide in the plane, transmission loss can be further reduced.

[0020] FIG. 4 is a cross-sectional view schematically illustrating another example of the configuration of a waveguide according to the present invention. The waveguide 3 shown in FIG. 4 is composed of a support substrate 10, a first-surface spacer 11 having a through groove 12, a signal conductor layer 13, a first-surface ground conductor layer 14, a support substrate 15, a second-surface spacer 21, a signal conductor layer 23, a second-surface ground conductor layer 24, and a support substrate 25. Among the components of the waveguide 3 shown in FIG. 4, those of the waveguide 1 shown in FIG. 1 or the waveguide 2 shown in FIG. 2 share common functions and actions, and therefore will not be described here. The second-surface spacer 21 has a through groove 22 formed therein, penetrating the two main surfaces of the second-surface spacer. Unlike the waveguide 2 shown in FIG. 3, a signal conductor layer 23 is disposed within the through groove 22. The signal conductor layer 23 is in contact with the surface of the support substrate 10 on the second-surface-side spacer 21 side, and is spaced apart from the second-surface-side ground conductor layer 24. When transmitting electromagnetic waves using a waveguide 3 having such two signal conductor layers 13 and 23, the generation of noise can be reduced by reversing the phase of the signal transmitted in one signal conductor layer from the phase of the signal transmitted in the other signal conductor layer.

[0021] 4, the signal conductor layer 13 and the signal conductor layer 23 are aligned in the planar direction. In the above-described waveguide having a signal conductor layer disposed in a through groove on each of both sides of the support substrate, the two signal conductor layers do not have to be aligned in the planar direction, and it is preferable that they at least partially overlap. In particular, by having the two signal conductor layers be aligned in the planar direction, noise generated between the two signal conductor layers is canceled out, further reducing noise generation.

[0022] The configuration of the waveguide of the present invention is not limited to the specific embodiment described above. For example, in the above embodiment, the first-surface spacer has one through groove. However, in the waveguide of the present invention, the first-surface spacer may have two or more through grooves. If the first-surface spacer has two or more through grooves, one signal conductor layer may be disposed in each through groove, and a total of two or more signal conductor layers may be disposed on the surface of the support substrate facing the first-surface spacer. Similarly, in the waveguide, the second-surface spacer may have two or more through grooves. If the waveguide has a second-surface spacer and a second-surface ground conductor layer, it is preferable that the second-surface spacer has through grooves that correspond in number, size, and in-plane position to the through grooves in the first-surface spacer. Signal conductor layers may or may not be disposed in the through grooves of the second-surface spacer. When the second-surface-side spacer has two or more through grooves, one signal conductor layer may be disposed in each through groove, and a total of two or more signal conductor layers may be disposed on the surface of the support substrate facing the first-surface-side spacer. Also, two or more signal conductor layers may be disposed in one through groove, but it is preferable that one signal conductor layer is disposed in one through groove.

[0023] For example, in the waveguide 1 shown in FIG. 1 , the support substrate 10, the first-surface-side spacer 11, the first-surface-side ground conductor layer 14, and the support substrate 15 are arranged in this order. However, the positions of the first-surface-side ground conductor layer 14 and the support substrate 15 may be reversed. That is, in the waveguide, the support substrate, the first-surface-side spacer, the support substrate, and the first-surface-side ground conductor layer may be arranged in this order. Even if the support substrate is arranged between the signal conductor layer and the first-surface-side ground conductor layer, the through grooves suppress loss of electromagnetic waves transmitted through the signal conductor layer. Similarly, in the waveguide 2 shown in FIG. 3 , the support substrate 10, the second-surface-side spacer 21, the second-surface-side ground conductor layer 24, and the support substrate 25 are arranged in this order. However, the positions of the second-surface-side ground conductor layer 24 and the support substrate 25 may be reversed. That is, in the waveguide, the support substrate, the second-surface-side spacer, the support substrate, and the second-surface-side ground conductor layer may be arranged in this order.

[0024] In the waveguide of the present invention, the physical properties such as the width A of the signal conductor layer, the width of the ground conductor layer, and the distance between the signal conductor layer and the ground conductor layer are appropriately set based on known techniques so that the characteristic impedance of the waveguide becomes a predetermined value. If a member such as a support substrate is disposed between the signal conductor layer and the ground conductor layer as in the waveguide 2 shown in Figure 3, the physical properties also include the thickness and dielectric characteristics of the member.

[0025] Each component of the waveguide of the present invention will be described in more detail. Hereinafter, the term "spacer" will be used interchangeably to refer to both the first-surface spacer and the second-surface spacer unless otherwise specified. Furthermore, the term "ground conductor layer" will be used interchangeably to refer to both the first-surface ground conductor layer and the second-surface ground conductor layer unless otherwise specified.

[0026] [Supporting Substrate] The supporting substrate is a member capable of supporting the signal conductor layer or the ground conductor layer, and is made of an electrically insulating material. As the supporting substrate, a flexible plastic film or plastic sheet is preferred in that it allows the production of a waveguide with excellent bendability.

[0027] Examples of materials constituting the support substrate include polyesters such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), polyethylene (PE), polypropylene (PP), polystyrene, ethylene vinyl acetate (EVA), polyolefins such as cycloolefin polymer (COP) and cycloolefin copolymer (COC), vinyl resins such as polyvinyl chloride and polyvinylidene chloride, polycarbonate (PC), polyamide, polyimide, acrylic resin, triacetyl cellulose (TAC), and polytetrafluoroethylene (PTFE). Among these, films made of PET, COP, COC, or PC are preferred.

[0028] The thickness of the support substrate is, for example, 5 to 500 μm, and from the viewpoint of flexibility and strength, it is preferably 10 to 100 μm, and more preferably 20 to 50 μm.

[0029] [Spacer] The spacer is a component arranged on the surface side of the support substrate, and has a through groove penetrating the two main surfaces of the spacer at a position in the plane corresponding to the signal conductor layer arranged on at least one surface of the support substrate. By arranging the spacer with the through groove between the signal conductor layer and the ground conductor layer, the signal conductor layer and the ground conductor layer can be kept separated by a constant distance. Furthermore, by having the width B of the through groove and the width A of the signal conductor layer satisfy the relationships of formulas (1) and (2), a waveguide with low transmission loss can be obtained, as described above.

[0030] The width B of the through groove is not particularly limited as long as it satisfies the relationship of formula (1) and formula (2), and may be, for example, 0.5 to 15 mm, preferably 1 to 10 mm. Furthermore, in order to further reduce the transmission loss of the waveguide, it is preferable that the width B of the through groove and the width A of the signal conductor layer satisfy the relationship of formula (3): Formula (3) A×1.5<B<A×2.5

[0031] The width B of the through groove is determined by arbitrarily selecting five locations along the direction in which the signal conductor layer extends in the through groove, measuring the widths of the through groove at the five selected locations using an optical microscope, and calculating the arithmetic average of the measured values.

[0032] The depth of the through groove (i.e., the thickness of the spacer) is adjusted appropriately according to the set value of the characteristic impedance of the waveguide, as described above, and may be, for example, 50 to 5000 μm, preferably 100 to 3000 μm, and more preferably 200 to 2000 μm.

[0033] The shape of the through-path in a plane parallel to the principal surface of the waveguide is not particularly limited as long as the signal conductor layer is disposed within the through-path and the width B and the width A of the signal conductor layer satisfy the formulas (1) and (2). For example, in the waveguide 1 shown in FIG. 2 , a single through groove 12 is formed in a plane parallel to the principal surface of the waveguide 1, extending along a single direction in which the signal conductor layer 13 extends. However, the through groove of the spacer included in the waveguide of the present invention may be composed of multiple rectangular grooves arranged side by side along the direction in which the signal conductor layer extends. Also, in the waveguide 1 shown in FIG. 2 , the through groove 12 extends along a single direction in which the signal conductor layer 13 extends in a plane parallel to the principal surface of the waveguide 1. However, the shape of the through groove in the present invention is not limited to the shape shown in FIG. 2 , and may be bent or branched depending on the shape of the signal conductor layer.

[0034] In order to further reduce the transmission loss of the waveguide, the dielectric loss tangent of the spacer measured under conditions of a temperature of 23° C. and a frequency of 10 GHz is preferably 0.1 or less, more preferably 0.05 or less, and even more preferably 0.02 or less. The lower limit is not particularly limited, and may be, for example, 0.0001 or more.

[0035] The dielectric loss tangent of the spacer can be measured by the following method. First, a sample consisting of at least a portion of the spacer peeled from the waveguide is filled into a PTFE (polytetrafluoroethylene) tube (outer diameter 2.5 mm, inner diameter 1.5 mm, length 10 mm). Using a cavity resonator (e.g., "CP-531" manufactured by Kanto Electronics Application Development Co., Ltd.), the dielectric characteristics are measured by the cavity resonator perturbation method under conditions of a temperature of 23°C and a frequency of 10 GHz. The influence of voids in the PTFE tube is corrected using the Bruggeman equation and the porosity, thereby obtaining the dielectric loss tangent of the sample at a temperature of 23°C and a frequency of 10 GHz. The porosity (volume fraction of voids in the tube) is calculated as follows. The volume of the space inside the tube is determined from the inner diameter and length of the tube. Next, the weight of the tube before and after filling with the sample is measured to determine the mass of the filled sample, and the volume of the filled sample is then determined from the obtained mass and the specific gravity of the sample. The filling rate is calculated by dividing the volume of the sample thus obtained by the volume of the space inside the tube calculated above.

[0036] The material constituting the spacer preferably contains an organic material from the viewpoints of dielectric properties, ease of forming a through groove, and bendability of the waveguide. Examples of the organic material include acrylic resin, polyimide, polyesters such as PET and PEN, polycarbonate, liquid crystal polymer (LCP), and epoxy resin. Among these, the spacer preferably contains acrylic resin, epoxy resin, or liquid crystal polymer, and more preferably contains acrylic resin. Spacer materials are described in detail in Japanese Patent No. 4994136 and Japanese Patent Laid-Open No. 2009-079140, the disclosures of which are incorporated herein by reference.

[0037] The acrylic resin refers to a polymer obtained by polymerizing a polymerizable monomer including a (meth)acrylate monomer. Examples of the (meth)acrylate monomer include monofunctional and polyfunctional (meth)acrylate monomers. The (meth)acrylate monomer and the polymerizable monomer may be an oligomer or polymer having a polymerizable group. Examples of the (meth)acrylate monomer include urethane (meth)acrylate, alicyclic (meth)acrylates such as tricyclodecane dimethanol di(meth)acrylate, (meth)acrylates having a hydroxyl group such as pentaerythritol triacrylate, aromatic (meth)acrylates such as modified bisphenol A di(meth)acrylate, dipentaerythritol di(meth)acrylate, and 3,4-epoxycyclohexylmethyl (meth)acrylate. Urethane (meth)acrylate or alicyclic (meth)acrylate is preferred. Furthermore, in terms of superior curability, it is preferable to include an acrylate as the (meth)acrylate monomer.

[0038] The spacer may be composed of a single layer or a laminate composed of multiple layers. When the spacer has multiple layers, the types of the layers may be the same or different.

[0039] The method for producing the spacer is not particularly limited, and examples include a method of preparing a raw material solution containing the material constituting the spacer or a precursor thereof, pouring the raw material solution into a metal mold having a concave-convex shape corresponding to the spacer and through-groove, and curing the layer of the raw material solution to form the spacer. Here, the concave-convex shape of the metal mold is composed of flat, shallow recesses having a shape corresponding to the outer periphery of the spacer, and convex portions formed on the bottom surface of the recesses in a shape and position corresponding to the through-groove. Such a metal mold can be produced according to a known molding method.

[0040] As an example, the formation of a spacer containing an acrylic resin will be described. The spacer-forming raw material liquid used to form the spacer containing an acrylic resin contains a polymerizable monomer including the above-mentioned (meth)acrylate monomer, and further contains a polymerization initiator, if necessary. The polymerization initiator may be either a photopolymerization initiator or a thermal polymerization initiator, with a photopolymerization initiator being preferred. As the photopolymerization initiator, a compound that generates an active species that polymerizes a polymerizable monomer upon irradiation with light can be used. As the photopolymerization initiator, a cationic polymerization initiator or a radical polymerization initiator can be used, and an appropriate photopolymerization initiator is selected depending on the polymerizable monomer. The spacer-forming raw material liquid may contain a solvent, if necessary.

[0041] When forming a spacer containing an acrylic resin, a preferred method is to pour a raw material liquid containing a polymerizable monomer including a (meth)acrylate monomer and a photopolymerization initiator into the recess of the mold, and then expose (irradiate) the raw material liquid layer to light to cure the layer, thereby forming the spacer. The exposure light may be ultraviolet light, visible light, or the like, and is appropriately selected depending on the polymerizable monomer. The exposure time and exposure dose are also appropriately selected depending on the type of polymerizable monomer and exposure light.

[0042] Methods for producing spacers include a method of printing the above-mentioned raw material liquid in a pattern on the surface of a temporary substrate, a method of forming a coating layer of the above-mentioned raw material liquid on the surface of a temporary substrate, then exposing the pattern to light, developing it, and removing the coating layer corresponding to the through grooves, and an imprint method in which a coating layer of the above-mentioned raw material liquid is formed on the surface of a temporary substrate, then a heated mold is pressed against the coating layer to form through grooves, and the coating layer is cured by light and / or heat.

[0043] [Signal Conductor Layer] A signal conductor layer is disposed on at least one surface side of the support substrate, in the through groove of the first-surface-side spacer. The signal conductor layer is separated from the ground conductor layer by the spacer. Furthermore, by satisfying the relationship between the width A of the signal conductor layer and the width B of the through groove in formulas (1) and (2), a waveguide with low transmission loss can be obtained, as described above.

[0044] The width A of the signal conductor layer satisfies the relationship between formulas (1) and (2) and is appropriately adjusted to match the set value of the characteristic impedance of the waveguide, as described above. The width A of the signal conductor layer may be, for example, 0.1 to 5 mm, and preferably 0.5 to 3 mm.

[0045] The thickness of the signal conductor layer is not particularly limited, but is preferably 0.2 to 200 μm, more preferably 0.5 to 50 μm, in that it provides a better effect of suppressing loss due to the skin effect.

[0046] The width A and thickness of the signal conductor layer are determined by arbitrarily selecting five locations along the direction in which the signal conductor layer extends, cutting the waveguide at the five selected locations, observing the cross section using an optical microscope, and arithmetically averaging the measured values ​​of width and thickness obtained from the observed image.

[0047] In terms of further reducing the transmission loss of the waveguide, when the direction perpendicular to the direction in which the signal conductor layer extends in a plane parallel to the main surface of the waveguide is defined as the "width direction," the positional deviation D between the center of the signal conductor layer in the width direction and the center of the through groove in the width direction is preferably 30% or less, and more preferably 10% or less, with respect to the width A of the signal conductor layer. Of these, it is even more preferable that the center of the signal conductor layer in the width direction and the center of the through groove in the width direction coincide with each other, that is, the positional deviation D is 0%.

[0048] The shape of the signal conductor layer in a plane parallel to the principal surface of the waveguide is not particularly limited as long as the signal conductor layer is disposed in the through-path and the width B and the width A of the signal conductor layer satisfy the formulas (1) and (2). For example, in the waveguide 1 shown in Fig. 2, the signal conductor layer 13 extends along one direction parallel to the principal surface of the waveguide 1, but in the waveguide of the present invention, the shape of the signal conductor layer is not limited to the shape shown in Fig. 2 and may be bent or branched.

[0049] The line length of the signal conductor layer in the waveguide is selected appropriately depending on the application of the waveguide, etc., but is preferably 50 mm or more, more preferably 100 mm or more, and even more preferably 250 mm or more. When the line length of the signal conductor layer is within the above range, the total amount of transmission loss increases, and the effects of the present invention are more effectively exhibited. The upper limit of the line length of the signal conductor layer is not particularly limited, and may be, for example, 1000 mm or less. Note that the line length of the signal conductor layer means the length of the path from one end of the signal conductor layer in the waveguide to the other end. When the signal conductor layer has a branched structure, it means the length of the longest path from one end of the signal conductor layer (e.g., a signal input end) to the other end (e.g., a signal output end) of the signal conductor layer.

[0050] The material constituting the signal conductor layer is not particularly limited as long as it is a conductive material, but a metallic material containing a metal with high conductivity is preferred. Examples of metals contained in the signal conductor layer include copper, silver, palladium, gold, platinum, aluminum, chromium, nickel, cadmium, lead, selenium, manganese, tin, vanadium, lithium, cobalt, and titanium, as well as alloys of two or more of these metals. The signal conductor layer preferably contains at least one metal selected from the group consisting of copper, silver, gold, platinum, and aluminum, and more preferably contains copper or silver.

[0051] The signal conductor layer can be formed by a known method. For example, a method can be used in which a metal layer is formed on the entire surface of a support substrate, a resist pattern is further formed on the surface of the metal layer, and the metal layer in the openings of the resist pattern is removed. Methods for forming a metal layer on the entire surface of a support substrate can include gas phase methods such as sputtering, ion plating, and vacuum deposition, as well as plating. Another method for forming the signal conductor layer can be used in which an ink or paste containing fine particles of the above metal is printed on the surface of the support substrate by a known printing method such as inkjet printing.

[0052] [Ground Conductor Layer] In the waveguide of the present invention, the ground conductor layer is disposed so as to be separated from the signal conductor layer by a spacer.

[0053] The thickness of the ground conductor layer is not particularly limited, but is preferably 0.2 to 200 μm, more preferably 0.5 to 50 μm, in that it is more effective in suppressing loss due to the skin effect.

[0054] For example, in the waveguide 1 shown in Fig. 1, the ground conductor layer 14 is formed across the entire width of the waveguide 1, but in the waveguide of the present invention, the width of the ground conductor layer may be shorter than the width of the waveguide. That is, the ground conductor layer may be formed on only a part of the width of the waveguide. The width and thickness of the ground conductor layer can be measured in accordance with the method for measuring the width A and thickness of the signal conductor layer.

[0055] The materials constituting the ground conductor layer, including preferred embodiments, are the same as those constituting the signal conductor layer. The ground conductor layer can be formed by a known method, such as the method described above for forming the signal conductor layer.

[0056] The waveguide of the present invention may have other components in addition to the support substrate, spacer, signal conductor layer, and ground conductor layer. Examples of such other components include an adhesive layer and a protective layer. When incorporated into an electronic device, the waveguide may have a connection portion for transmitting electromagnetic waves, which are signals, to other components (such as other circuits and other transmission lines). The waveguide may have electronic components in addition to the connection portion.

[0057] [Method for Manufacturing Waveguide] The method for manufacturing the waveguide is not particularly limited as long as it can produce a waveguide having the above-described configuration, and known methods can be used. For example, the waveguides shown in FIGS. 1 and 2 can be manufactured by bonding a support substrate with a signal conductor layer, a spacer having a through groove, and a support substrate with a ground conductor layer together, either directly or via an adhesive layer, so that the signal conductor layer is positioned in the through groove of the spacer. Similarly, the waveguide shown in FIG. 3 or the waveguide shown in FIG. 4 can be manufactured by bonding a support substrate with a ground conductor layer, a spacer having a through groove, a support substrate with a signal conductor layer, a spacer having a through groove, and a support substrate with a ground conductor layer together, either directly or via an adhesive layer, so that the signal conductor layer is positioned in the through groove of the spacer. The support substrate with a signal conductor layer and the support substrate with a ground conductor layer can be manufactured, for example, according to or in accordance with the method for forming the signal conductor layer described above.

[0058] [Uses of Waveguide] The waveguide of the present invention is used for transmitting electromagnetic waves. In particular, the waveguide of the present invention is preferably used for transmitting high-frequency electromagnetic waves. Specifically, the frequency of the electromagnetic waves is preferably 3 to 30 GHz, more preferably 2 to 25 GHz, and even more preferably 5 to 20 GHz.

[0059] The waveguide of the present invention can be used as a part of various electronic devices that utilize electromagnetic waves (more preferably high-frequency electromagnetic waves). For example, the waveguide of the present invention can be used as a transmission line that transmits electromagnetic waves from one side to another, an antenna element that receives and transmits electromagnetic waves, and other components.

[0060] 5 is a plan view schematically illustrating an example of the configuration of an antenna element (planar antenna element) using the waveguide of the present invention. The antenna element 4 includes a support substrate 40, a first-surface spacer 41 having a through groove 42, a line 43 formed of a signal conductor layer, and a first-surface ground conductor layer 44. The characteristics, functions, and preferred embodiments of each component of the antenna element 4 have been described above. The line 43 includes an end 43a connected to an external circuit of the antenna element 4, two ends 43b including the terminations of the line 43, and a branch portion 43c located between the ends 43a and 43b. A rectangular opening 45 is formed in the first-surface ground conductor layer 44 in a region including a position facing the end 43b of the line 43.

[0061] In the antenna element 4, when an electromagnetic wave is supplied from the end 43a to the line 43, the electromagnetic wave is transmitted through the branch portion 43c to the end 43b, and then radiated from the end 43b. The electromagnetic wave radiated from the end 43b of the line 43 passes through the opening 45 in the first-surface-side ground conductor layer 44 and is emitted to the outside of the antenna element 4. The antenna element 4 also has the function of receiving external electromagnetic waves at the end 43b of the line 43 through the opening 45 and transmitting the received electromagnetic waves to an external circuit through the line 43. By using the waveguide of the present invention in the antenna element 4 having such a structure, transmission loss between the end 43a and the end 43b of the line 43 during reception and transmission of electromagnetic waves can be further reduced. Furthermore, in the antenna element 4 shown in FIG. 5, the first-surface-side ground conductor layer 44 has an opening 45 at a position facing the end 43b of the line 43 from which the electromagnetic wave is radiated, thereby improving the antenna characteristics. The size and shape of the end 43b of the line 43 are appropriately set using a known method such as simulation so as to obtain the desired antenna characteristics.

[0062] The antenna element using the waveguide of the present invention is not limited to the embodiment shown in FIG. 5 . For example, in the antenna element, the number of antenna units located at the end of the line and receiving or transmitting electromagnetic waves is not limited to two, but may be three or more. When there are three or more antenna units, the ground conductor layer (the first-surface ground conductor layer and the second-surface ground conductor layer) may have three or more openings corresponding to the number of antenna units. Furthermore, the ground conductor layer may not have any openings. The antenna element using the waveguide of the present invention may be an arrayed antenna element having multiple antenna units. In such an arrayed antenna element, the line has a number of branch structures corresponding to the number of antenna units to transmit electromagnetic waves to the multiple antenna units. When the waveguide of the present invention is used, the total amount of transmission loss can be reduced even if the line length of the line made of the signal conductive layer is increased due to the multiple branch structures.

[0063] Although the embodiments of the present invention have been described above, these are merely examples of the present invention, and various configurations other than those described above can be adopted as long as they do not impair the effects of the present invention.

[0064] The present invention will be explained in more detail below with reference to examples. Note that the materials, amounts used, ratios, treatment contents, and treatment procedures shown in the following examples can be appropriately changed without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below.

[0065] Example A1 - Formation of Signal Conductor Layer - A cycloolefin polymer film (40 μm thick) was prepared as a support substrate. The support substrate was cut into a size of 100 mm x 200 mm, and the surface was subjected to ultrasonic cleaning (45 kHz). The cut support substrate was then placed inside a sputtering device. After reducing the pressure inside the device, argon gas (0.27 Pa) was introduced, and sputtering was performed using copper as a target, forming a copper layer with a thickness of 1000 nm on the support substrate.

[0066] The photosensitive transfer member (negative transfer material 1) described in JP 2020-204757 A was cut to a size of 100 mm x 200 mm, and the cover film was peeled off from the photosensitive transfer material. The support substrate and the photosensitive transfer material were bonded together so that the surface of the photosensitive resin layer exposed by peeling off the cover film was in contact with the copper layer to obtain a laminate. This bonding was performed under conditions of a roll temperature of 100 ° C, a linear pressure of 1.0 MPa, and a linear speed of 4.0 m / min.

[0067] Next, a photomask having a pattern complementary to the signal conductor layer to be formed was laminated on the temporary support side of the photosensitive transfer material of the obtained laminate. After that, an ultra-high pressure mercury lamp ("MAP-1200L" manufactured by Nippon Kaken Co., Ltd., dominant exposure wavelength: 365 nm) was irradiated at 100 mJ / cm through this photomask. ２ The photosensitive resin layer of the photosensitive transfer material was exposed by irradiation. The temporary support of the photosensitive transfer material was peeled off from the exposed laminate. The laminate was then subjected to shower development for 30 seconds using a 1.0% aqueous sodium carbonate solution at a liquid temperature of 25°C, forming a resist pattern. The copper layer of the resulting laminate was then etched for 30 seconds at 23°C using a copper etching solution ("Cu-02" manufactured by Kanto Chemical Co., Inc.). The resist pattern was then peeled off using propylene glycol monomethyl ether acetate. This resulted in the production of a laminate having a support substrate and a signal conductor layer disposed on one surface of the support substrate. The formed signal conductor layer was disposed at the center of the direction along the short side of the support substrate and had a strip shape with a width A of 2.5 mm and a length (line length) of 200 mm. The signal conductor layer had a thickness of 1000 nm.

[0068] - Formation of First-Surface-Side Ground Conductor Layer - A cycloolefin polymer film (40 μm thick) was prepared as a support substrate. The support substrate was cut into a size of 100 mm x 200 mm, and the surface was subjected to ultrasonic cleaning (45 kHz). The cut support substrate was then placed inside a sputtering device. After reducing the pressure inside the device, argon gas (0.27 Pa) was introduced, and sputtering was performed using copper as a target, forming a copper layer with a thickness of 1000 nm on the support substrate.

[0069] - Formation of spacers on the first surface side - Spacers on the first surface side were produced with reference to the method for forming a resin layer in Example 1 of WO 2018 / 084289. First, a spacer-forming raw material solution having the composition shown below was prepared.

[0070] (Composition of raw material solution) Urethane (meth)acrylate (U-4HA, manufactured by Shin-Nakamura Chemical Co., Ltd.) 42 parts by mass Tricyclodecane dimethanol diacrylate (A-DCP, manufactured by Shin-Nakamura Chemical Co., Ltd.) 42 parts by mass Photopolymerization initiator (Irgacure TPO, manufactured by BASF) 1 part by mass

[0071] A mold was prepared for forming the first-surface spacers. FIG. 6 is a plan view schematically illustrating the configuration of the mold used to form the first-surface spacers. As shown in the figure, the mold 50 had an outer frame 51, a recess 52 surrounded by the outer frame 51, and a convex portion 53 located at the center of the recess 52 and protruding toward the front of the page. The outer periphery of the recess 52 was rectangular, measuring 100 mm in width and 198 mm in length. The convex portion 53 was rectangular, measuring 3.5 mm in width and 196 mm in length, and was positioned at the center of the recess 52 in the width and length directions, with each side of the convex portion 53 parallel to each side of the outer periphery of the recess 52. As a result, both ends of the convex portion 53 in the length direction were spaced 1.0 mm from the outer periphery of the recess 52. The depth of the recess 52 and the height of the convex portion 53 were 500 μm. After the prepared raw material liquid was filled into the recess 52 of the mold 50, ultraviolet light was applied at 500 mJ / cm using a 200 W / cm air-cooled metal halide lamp (manufactured by Eye Graphics Co., Ltd.). ２ The layer of the raw material liquid was photocured by irradiating the material. The obtained cured layer containing the acrylic resin was peeled from the mold to produce a first-surface spacer having a thickness of 500 μm and a rectangular through-groove having a width B of 3.5 mm and a length of 196 mm. A portion of the first-surface spacer was sampled, and the dielectric loss tangent of the spacer was measured using the method described above. The dielectric loss tangent of the spacer at a temperature of 23° C. and a frequency of 10 GHz was 0.01.

[0072] -Fabrication of Waveguide- The fabricated components were bonded together in the following order: a support substrate with a first-surface-side ground conductor layer, a first-surface-side spacer, and a support substrate with a signal conductor layer, to fabricate a waveguide A1 having the configuration shown in Figures 1 and 2. That is, in the process of bonding the components together, the support substrate with a first-surface-side ground conductor layer was positioned so that the first-surface-side ground conductor layer faced the first-surface-side spacer, and the support substrate with a signal conductor layer was positioned so that the signal conductor layer was positioned within the through groove of the first-surface-side spacer. Within the through groove of the fabricated waveguide A1, the signal conductor layer was not biased in the width direction (short side direction), and the center of the signal conductor layer and the center of the through groove coincided in the width direction. That is, the positional deviation D between the center of the signal conductor layer and the center of the through groove in the width direction was 0% of the width A of the signal conductor layer.

[0073] [Example A2, Comparative Example A1, Comparative Example A2] Each waveguide was fabricated according to the method described in Example A1, except that in the first-surface-side spacer formation step, a mold was used in which the width of the convex portion was changed so that the width B of the through hole was the value listed in Table 1 below. In all of the waveguides of Example A2, Comparative Example A1, and Comparative Example A2, the center of the signal conductor layer and the center of the through groove coincided in the width direction. That is, the positional deviation D between the center of the signal conductor layer and the center of the through groove in the width direction was 0% of the width A of the signal conductor layer.

[0074] Example B1 - Formation of signal conductor layer - A laminate having a support substrate and a signal conductor layer disposed on one surface side of the support substrate was produced in accordance with the method described in the signal conductor layer formation step of Example A1, except that in the step of forming the signal conductor layer, a photomask having a pattern shape such that a strip-shaped signal conductor layer having a width A of 1.35 mm and a length (line length) of 200 mm was formed.

[0075] - Formation of first-surface-side ground conductor layer and second-surface-side ground conductor layer - According to the method described in the step of forming the first-surface-side ground conductor layer in Example A1, a first-surface-side ground conductor layer and a second-surface-side ground conductor layer each having a copper layer with a thickness of 1000 nm on a support substrate were fabricated.

[0076] - Formation of first-surface spacers and second-surface spacers - The first-surface spacers and second-surface spacers were each produced according to the method described in the first-surface spacer formation process of Example A1, except that a mold was used in which the width of the convex portion was changed so that the width B of the through hole would be the value listed in Table 2 below.

[0077] -Fabrication of Waveguide- The fabricated components were bonded together in the following order: support substrate with first-surface-side ground conductor layer, first-surface-side spacer, support substrate with signal conductor layer, second-surface-side spacer, and support substrate with second-surface-side ground conductor layer, to fabricate waveguide B1 having the configuration shown in Figure 3. In the process of bonding the components, the support substrate with first-surface-side ground conductor layer was positioned so that the first-surface-side ground conductor layer faced the first-surface-side spacer, the support substrate with signal conductor layer was positioned so that the signal conductor layer was located in the through groove of the first-surface-side spacer, and the support substrate with second-surface-side ground conductor layer was positioned so that the second-surface-side ground conductor layer faced the second-surface-side spacer. Within the through groove of the first-surface-side spacer of the fabricated waveguide B1, the center of the signal conductor layer and the center of the through groove in the width direction coincided. That is, the positional deviation D between the center of the signal conductor layer and the center of the through groove in the width direction was 0% of the width A of the signal conductor layer.

[0078] [Example B2, Comparative Example B1, Comparative Example B2] Waveguides were each produced according to the method described in Example B1, except that in the process of forming the first-surface spacer and the second-surface spacer, the first-surface spacer and the second-surface spacer were produced using a mold in which the width of the convex portion was changed so that the width B of the through hole was the numerical value listed in Table 2 below. In all of the waveguides of Example B2, Comparative Example B1, and Comparative Example B2, the center of the signal conductor layer in the width direction and the center of the through groove of the first-surface spacer coincided. That is, the positional deviation D between the center of the signal conductor layer and the center of the through groove in the width direction was 0% of the width A of the signal conductor layer.

[0079] [Evaluation] The S parameters of the fabricated waveguide were measured using a vector network analyzer at a temperature of 25°C to determine the transmission loss when transmitting an electromagnetic wave with a frequency of 10 GHz. The obtained transmission loss value (unit: dB) was evaluated based on the following evaluation criteria. (Evaluation criteria) A: Transmission loss is -1.0 dB or less. B: Transmission loss is more than -1.0 dB.

[0080]

[0081]

[0082] As shown in Tables 1 and 2, it was confirmed that a waveguide that does not satisfy either of the above formulas (1) and (2) has a large transmission loss, whereas a waveguide according to the present invention that satisfies both the above formulas (1) and (2) has a smaller transmission loss.

[0083] REFERENCE SIGNS LIST 1, 2, 3 Waveguide 4 Antenna element 10, 15, 25, 40 Support substrate 11 First surface side spacer 12, 22, 42 Through groove 13, 23 Signal conductor layer 14 First surface side ground conductor layer 21 Second surface side spacer 24 First surface side ground conductor layer 41 Spacer 43 Line 43a, 43b End 43c Branch portion 44 Ground conductor layer 45 Opening 50 Mold 51 Outer frame 52 Recess 53 Convex portion S1 First surface S2 Second surface

Claims

1. A waveguide comprising: a supporting substrate, a first surface side spacer disposed on one surface side of the supporting substrate and having a through groove, a signal conductor layer disposed on one surface side of the supporting substrate and disposed within the through groove, and a first surface side ground conductor layer disposed on the opposite side of the first surface side spacer to the supporting substrate and disposed spaced apart from the signal conductor layer, the waveguide satisfying the relationships of the following formulas (1) and (2) where A is the width of the signal conductor layer and B is the width of the through groove. Formula (1) A x 1.2<B Formula (2) B<A x 3.0 2. A waveguide as described in claim 1, further comprising: a second surface side spacer having a through groove arranged on the other surface side of the supporting substrate; and a second surface side ground conductor layer arranged on the opposite side of the second surface side spacer to the supporting substrate, wherein the through groove of the first surface side spacer and the through groove of the second surface side spacer are aligned in the planar direction.

3. The waveguide according to claim 1 or 2, wherein the signal conductor layer has a line length of 100 mm or more.

4. A waveguide according to claim 1 or 2, wherein the dielectric tangent of the first surface side spacer at a temperature of 25° C. and a frequency of 10 GHz is 0.1 or less.

5. The waveguide according to claim 1 or 2, wherein the first surface side spacer comprises a (meth)acrylic resin.

6. The waveguide according to claim 1 or 2, which is used for transmitting electromagnetic waves having a frequency of 3 to 30 GHz.

7. An antenna element using a waveguide according to claim 1 or 2.

8. The antenna element according to claim 7, wherein the first surface side ground conductor layer has an opening.

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