Transparent antennas and RF tags

Abstract

A transparent antenna comprising a transparent substrate, an antenna portion disposed on the transparent substrate, and a bonding portion electrically bonded to the antenna portion, wherein the bonding portion comprises a first conductive pattern and a first opening portion where the first conductive pattern is not formed, the antenna portion comprises a second conductive pattern and a second opening portion where the second conductive pattern is not formed, and the surface free energy E1 of the first conductive pattern is 60 mJ / m 2 Hereinafter, the surface free energy E0 of the transparent substrate at the first opening is greater than the surface free energy E1.

Description

Technical Field

[0001] The present invention relates to a transparent antenna and an RF tag. Background Art

[0002] For example, in automobiles, film antennas installed on windshields are known as antennas for receiving various radio waves such as TV and FM radio waves, and radio waves related to position coordinate information transmitted by GPS (global positioning system) satellites used in car navigation systems.

[0003] Film antennas are also used for radio frequency identification (RFID), which is widely used in a variety of industries, including transportation, handling, manufacturing, waste management, mail tracking, carry-on baggage verification on airplanes, and toll management on toll roads. RFID tags and labels are useful for tracking deliveries from suppliers to customers and through the customer's supply chain.

[0004] As such a film antenna, a technique has been proposed in which an antenna is formed using a conductive pattern to improve the invisibility of the conductive pattern (see, for example, Patent Documents 1 to 5).

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 2011-66610

[0008] Patent Document 2: Japanese Patent Application Laid-Open No. 2011-91788

[0009] Patent Document 3: Japanese Patent Application Laid-Open No. 2017-175540

[0010] Patent Document 4: Japanese Patent Application Laid-Open No. 2003-209421

[0011] Patent Document 5: Japanese Patent Application Laid-Open No. 2016-105624 Summary of the Invention

[0012] Problems to be solved by the invention

[0013] As described in the above-mentioned prior art, miniaturization of the conductive pattern improves its invisibility. However, miniaturization of the conductive pattern may make it difficult to bond the conductive pattern constituting the antenna to the IC chip electrically connected thereto.

[0014] Patent Document 4 discloses that when bonding an IC chip, a sub-antenna pattern is formed around the IC chip to create an IC chip mark. Bonding is then performed so that the sub-antenna pattern of the IC chip mark is electrically connected to a main antenna pattern formed on a substrate. Patent Document 5 also discloses using an anisotropic conductive paste (ACP) to bond the IC chip to the conductive pattern that constitutes the antenna.

[0015] However, particularly when the antenna pattern includes conductive thin wires with a line width of 5 μm or less to improve the invisibility of the pattern, it may be difficult to bond the conductive pattern constituting the antenna to an IC chip electrically connected thereto.

[0016] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a transparent antenna having excellent bonding properties to a semiconductor element and an RF tag including the transparent antenna.

[0017] Solutions for solving problems

[0018] The present inventors conducted intensive research to solve the above problems and found that the above problems can be solved by adjusting the surface free energy of the conductive pattern in contact with the anisotropic conductive adhesive and the surface free energy of the transparent substrate, thereby completing the present invention.

[0019] That is, the present invention is as follows.

[0020] [1] A transparent antenna comprising a transparent substrate, an antenna portion disposed on the transparent substrate, and a bonding portion electrically bonded to the antenna portion.

[0021] The bonding portion includes a first conductive pattern and a first opening where the first conductive pattern is not formed.

[0022] The antenna portion includes a second conductive pattern and a second opening portion where the second conductive pattern is not formed.

[0023] The surface free energy E1 of the first conductive pattern is 60 mJ / m 2 the following,

[0024] The surface free energy E0 of the transparent substrate at the first opening is greater than the surface free energy E1.

[0025] [2] The transparent antenna according to [1], wherein the second conductive pattern includes second conductive thin wires having a line width W2 of 0.25 μm or more and 5.0 μm or less.

[0026] [3] The transparent antenna according to [1] or [2], wherein:

[0027] The height T1 of the first conductive pattern is greater than or equal to 0.05 μm and less than or equal to 1.0 μm.

[0028] The height T2 of the second conductive pattern is greater than or equal to 0.05 μm and less than or equal to 1.0 μm.

[0029] [4] The transparent antenna according to any one of [1] to [3], wherein:

[0030] The first conductive pattern has first conductive thin wires, and the second conductive pattern has second conductive thin wires.

[0031] The pitch P1 of the first conductive thin wires is smaller than the pitch P2 of the second conductive thin wires.

[0032] The pitch P1 is not less than 1.0 μm and not more than 10 μm.

[0033] The pitch P2 is not less than 20 μm and not more than 1000 μm.

[0034] [5] The transparent antenna according to any one of [1] to [4], wherein:

[0035] The area ratio S1 of the first conductive pattern per unit area is greater than the area ratio S2 of the second conductive pattern per unit area.

[0036] The above-mentioned occupied area ratio S1 is 30% or more and 90% or less,

[0037] The above-mentioned occupied area ratio S2 is 0.1% or more and 10.0% or less.

[0038] [6] The transparent antenna according to any one of [1] to [5], wherein:

[0039] The difference between the surface free energy E0 and the surface free energy E1 (E0-E1) is 10 to 30 mJ / m 2 .

[0040] [7] An RF tag comprising:

[0041] The transparent antenna according to any one of [1] to [6]; and

[0042] A semiconductor element is electrically connected to the connecting portion of the transparent antenna.

[0043] [8] The RF tag according to [7], wherein:

[0044] The semiconductor element is electrically bonded to the bonding portion via an anisotropic conductive adhesive.

[0045] Effects of the Invention

[0046] According to the present invention, a transparent antenna having excellent bonding properties to a semiconductor element and an RF tag including the transparent antenna can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 It is a plan view showing a linear form of the RF tag according to this embodiment.

[0048] Figure 2 yes Figure 1 Magnified view of S1a.

[0049] Figure 3 It is a plan view showing a ring-shaped RF tag according to this embodiment.

[0050] Figure 4 yes Figure 3 Magnified view of S1b.

[0051] Figure 5 This is a schematic cross-sectional view showing a state in which a semiconductor element is bonded to a bonding portion of the RF tag according to the present embodiment via an anisotropic conductive adhesive.

[0052] Figure 6 yes Figure 2 and Figure 4 Magnified image of S2 (a).

[0053] Figure 7 yes Figure 2 and Figure 4 Magnified image of S3 (a).

[0054] Figure 8 It is a schematic cross-sectional view of the RF tag according to this embodiment. DETAILED DESCRIPTION

[0055] Hereinafter, an embodiment of the present invention (hereinafter referred to as the "present embodiment") will be described in detail. However, the present invention is not limited thereto and various modifications may be made without departing from the spirit of the present invention. It should be noted that in the drawings, the same elements are denoted by the same reference numerals and repeated descriptions are omitted. In addition, positional relationships such as up and down, left and right, etc., are based on the positional relationships shown in the drawings unless otherwise specified. Furthermore, the dimensional ratios in the drawings are not limited to the ratios shown in the drawings.

[0056] Transparent Antenna

[0057] The transparent antenna of this embodiment includes a transparent substrate, an antenna portion disposed on the transparent substrate, and a bonding portion electrically bonded to the antenna portion. The bonding portion includes a first conductive pattern and a first opening portion where the first conductive pattern is not formed. The antenna portion includes a second conductive pattern and a second opening portion where the second conductive pattern is not formed. The surface free energy E1 of the first conductive pattern is 60 mJ / m2 Hereinafter, the surface free energy E0 of the transparent substrate at the first opening is greater than the surface free energy E1.

[0058] Figure 1 A top view of an RF tag 100 having a transparent antenna 10 according to the present embodiment is shown. The transparent antenna 10 according to the present embodiment includes a transparent substrate 11, a collector portion 12 formed on the transparent substrate 11, and an antenna portion 13. The collector portion 12 is electrically connected to the antenna 13 and is a portion that collects electricity generated by the antenna portion 13 in response to a predetermined frequency toward the semiconductor element 14. In addition, the junction portion 121 refers to the portion of the collector portion 12 that is bonded to the semiconductor element 14. In the following, there is no need to distinguish between the collector portion 12 and its junction portion 121, and descriptions related to both may sometimes be expressed as "collector portion 12 (junction portion 121)." In addition, even when simply referred to as "collector portion 12," it does not mean the portion of the collector portion 12 other than the junction portion 121.

[0059] Figure 2 Show Figure 1 A magnified view of S1a. Figure 2 In the embodiment, the collector portion 12 has a joint portion 121 formed by two or more front ends facing each other. The joint portion 121 is electrically connected to the semiconductor element 14 by means of an anisotropic conductive adhesive or the like. In addition, the antenna portion 13 is electrically connected to the joint portion 121, and can receive radio waves of a specified frequency and transmit electrical signals to the semiconductor element 14, or can transmit radio waves of a specified frequency according to the output of the semiconductor element 14. It should be noted that Figure 2 , the shape of the collector portion 12 is not limited thereto. As an example, Figure 2 The collector portion 12 has an area equal to or several times the projected area of ​​the semiconductor element in a plan view, and is preferably substantially covered when the semiconductor element 14 is bonded to the bonding portion 121. In this case, the collector portion 12 can be said to be substantially composed of only the bonding portion 121.

[0060] Figure 1 , a linear transparent antenna 10 and an RF tag 100 are shown, each having two antenna sections 13 and a collector section 12 having a junction section 121 disposed therebetween. However, the configuration of the collector section 12 (junction section 121) and the antenna section 13 is not limited thereto. For example, Figure 3 Thus, the transparent antenna 10 and RF tag 100 of this embodiment may be loop-shaped transparent antennas 10 and RF tag 100 in which the collector portion 12 is loop-shaped and the antenna portion 13 is provided around the loop-shaped collector portion 12 .

[0061] Figure 4 Show Figure 3 The enlarged image of S1b. Figure 4 As shown, the ring-shaped collector portion 12 has a junction portion 121 formed by facing the front ends of the ring. The junction portion 121 is the front end of the collector portion 12 and is a region that is bonded to the semiconductor element 14.

[0062] The transparent antenna of this embodiment is not limited to the λ / 2 dipole antenna configuration, and may have other antenna configurations such as a grounded λ / 4 monopole antenna. Accordingly, the current collecting portion 12 (joint portion 121 ) and the antenna portion 13 may adopt various configurations.

[0063] Next, the bonding properties of the semiconductor element will be described. As described above, the bonding portion 121 is electrically bonded to the semiconductor element 14 using an anisotropic conductive adhesive or the like. The anisotropic conductive adhesive primarily comprises: a resin binder containing a precursor such as an epoxy resin, and, for example, 10 to 30% by weight of conductive particles such as Ni, Ag, Au, and Pt with a particle size of 3 μm to 10 μm dispersed in the resin binder. By sandwiching these between electrodes and applying pressure while heating, the resin binder is spread, and the conductive particles are electrically bonded to the electrodes. Depending on the bonding process, anisotropic conductive adhesives are known to be film-type, paste-type, or liquid-type.

[0064] In this type of bonding, the anisotropic conductive adhesive needs to be spread to a thickness that allows the conductive particles to electrically bond with the electrodes. Therefore, it is ideal that the anisotropic conductive adhesive fully wets and diffuses the bonding area. However, if the anisotropic conductive adhesive seeps into the surrounding area of ​​the semiconductor element and wets and diffuses excessively, in addition to causing the RF tag to have a poor appearance, it may also cause unintended electrical bonding. Especially when using a transparent antenna, if a metallic part originating from the anisotropic conductive adhesive is generated in the surrounding area of ​​the semiconductor element, the metallic part will be particularly conspicuous, resulting in a loss of commercial value such as transparency. In addition, due to the miniaturization of semiconductor elements, there is a tendency that it is more difficult to adjust the amount of anisotropic conductive adhesive used, and the yield rate is easily reduced due to bleeding.

[0065] In contrast, in this embodiment, the surface free energy of the bonding portion 121 is adjusted to improve the electrical bonding reliability of the anisotropic conductive adhesive and suppress the appearance defects caused by the leakage of the anisotropic conductive adhesive. Specifically, a bonding portion 121 having a first conductive pattern and a first opening portion without the first conductive pattern is used. Furthermore, the surface free energy E1 of the first conductive pattern is set to 60 mJ / m 2 Hereinafter, the surface free energy E0 of the transparent substrate at the first opening is adjusted to be greater than the surface free energy E1.

[0066] Thus, the bonding portion 121 can be formed with a portion (the first opening 301 ) that is easily wetted by the anisotropic conductive adhesive and a portion (the first conductive pattern 300 ) that is not easily wetted by the anisotropic conductive adhesive. Figure 5 FIG. 1 is a schematic cross-sectional view showing a state where a semiconductor element 14 is bonded to a bonding portion 121 using an anisotropic conductive adhesive. Figure 5 As shown, the anisotropic conductive adhesive easily wets the first opening 301, making it easier for the conductive particles 21 to bond the first conductive pattern 300 to the semiconductor element 14. This reduces bonding defects and further improves the stability of wire bonding. Furthermore, the anisotropic conductive adhesive does not easily wet the first conductive pattern 300, preventing the anisotropic conductive adhesive from seeping beyond the first conductive pattern 300 and allowing the location where the anisotropic conductive adhesive stops spreading between patterns to be precisely controlled.

[0067] From the above viewpoints, the difference between the surface free energy E0 and the surface free energy E1 (E0-E1) is preferably 10 to 30 mJ / m 2 , more preferably 15 to 25 mJ / m 2 , more preferably 17 to 22 mJ / m 2 By making the difference (E0-E1) 10mJ / m 2 As a result, there is a tendency that the difference between the portion that is easily wetted by the anisotropic conductive adhesive and the portion that is not easily wetted becomes larger, and the anisotropic conductive adhesive bleeding is further suppressed. 2 As a result, there is a tendency to further suppress bonding failure caused by excessive reduction in wettability of the first conductive pattern 300 .

[0068] From the same viewpoint, the surface free energy E0 is preferably 45 to 100 mJ / m 2 , more preferably 50 to 90 mJ / m 2 , more preferably 60 to 80 mJ / m 2 By making the surface free energy E0 45mJ / m 2 As a result, the first opening 301 is easily filled with anisotropic conductive adhesive, and the bonding reliability of the semiconductor element 14 tends to be further improved. 2 As a result, there is a tendency that the wettability between the opening of the transparent substrate and the anisotropic conductive adhesive is ensured, the entrapment of air bubbles can be prevented, and the bonding stability is further improved.

[0069] Furthermore, from the same point of view, the surface free energy E1 is 60mJ / m 2Below, preferably 10 to 60 mJ / m 2 , more preferably 20 to 60 mJ / m 2 , more preferably 30 to 60 mJ / m 2 By making the surface free energy E1 10mJ / m 2 As a result, there is a tendency to further suppress the bonding failure caused by excessive reduction in wettability of the first conductive pattern 300. In addition, by setting the surface free energy E1 to 60 mJ / m 2 Hereinafter, the bleeding of the anisotropic conductive adhesive is further suppressed.

[0070] The detailed mechanism by which the bleeding of the anisotropic conductive adhesive is suppressed when the surface free energy E1 is within the above range is not clear, but it can be inferred as follows: The surface tension of the resin binder containing the precursor such as epoxy resin constituting the anisotropic conductive adhesive is about 40 mJ / m 2 ~50mJ / m 2 If E1 is too small compared to this value, the anisotropic conductive adhesive will not wet the first conductive pattern easily, resulting in reduced electrical bonding properties. On the other hand, if E1 is too large compared to the surface tension of the resin binder, the anisotropic conductive adhesive may wet the first conductive pattern too well, potentially causing unintended anisotropic conductive adhesive bleed-out. However, the reasons for suppressing anisotropic conductive adhesive bleed-out are not limited to the above.

[0071] Here, the surface free energy defined in this embodiment will be explained. Generally speaking, molecules within a resin are stabilized by interactions with surrounding molecules. However, molecules on the resin surface have less stabilization from surrounding molecules than those forming the surface. Therefore, molecules on the surface have greater free energy than those within. This energy is referred to as surface free energy.

[0072] According to the theoretical formula of Kaelbel and Uy, the surface free energy γ of the material surface is calculated according to the dispersion component (γ d ) and polar components (γ p ), can be expressed by the following formula (1). In addition, the surface free energy γ of the solid SV and the surface free energy of the liquid γ LV It can be expressed by the following formulas (2) and (3). It is known that when the contact angle obtained by dropping a certain solvent on the surface of a solid substrate is defined as θ, the relationship of the following formula (4) holds.

[0073] γ=γ d +γ p (1)

[0074] γ SV =γ SV d +γ SV p (2)

[0075] γ LV =γ LV d +γ LV p (3)

[0076] γ LV (1+cosθ) / 2=(γ SV d ×γ LV d ) 0.5 +(γ SV p ×γ LV p ) 0.5 (4)

[0077] In order to determine the two unknown components of the surface free energy of the solid, two liquids with known surface free energies are used to measure the contact angle θ between the solvent and the surface forming the bonding portion 121. Then, by substituting these into the above equation (4) and solving the simultaneous equations, the dispersion component (γ) of the surface free energy of the surface forming the bonding portion 121 can be determined. SV d ) and polar components (γ SV p ), the surface free energy γ of the solid can be obtained by formula (2) SV .

[0078] It should be noted that, as described later, the surface free energy E0 can be adjusted by providing a layer on the substrate surface or selecting the components that constitute this layer. Furthermore, in addition to the conductive components such as conductive metals and conductive polymers that constitute the conductive pattern, the surface free energy E1 can also be adjusted by the types and ratios of non-conductive components such as metal oxides, metal compounds, and organic compounds that constitute the copper wire pattern. It should be noted that even if the same ink composition is used to form the conductive pattern, the state of the non-conductive components contained in the conductive pattern will vary depending on the firing method. Therefore, the surface free energy E1 can be adjusted by the firing method in addition to the ink composition.

[0079] It should be noted that, in this embodiment, the improvement of bonding properties refers to the improvement of the bonding reliability and the suppression of appearance defects.

[0080] 〔Transparent substrate〕

[0081] In this embodiment, a transparent substrate 11 is used. Here, "transparent" means that the visible light transmittance is preferably 80% or higher, more preferably 90% or higher, and even more preferably 95% or higher. The visible light transmittance can be measured according to JIS K7361-1:1997.

[0082] The transparent substrate 11 may be formed of one material or may be a laminate of two or more materials. In addition, when the substrate is a multilayer structure having two or more materials laminated thereon, the substrate may be an organic substrate or an inorganic substrate laminated thereon, or an organic substrate and an inorganic substrate laminated thereon.

[0083] Examples of the transparent substrate 11 include a single-layer sheet having a core layer, a laminated sheet having a core layer and a first outermost layer, a laminated sheet having a core layer and a second outermost layer, a laminated sheet having a first outermost layer and a second outermost layer, and a laminated sheet having a core layer and a first outermost layer and a second outermost layer. Furthermore, the laminated sheet may further include another layer between the core layer and the first outermost layer, between the core layer and the second outermost layer, or between the first outermost layer and the second outermost layer.

[0084] It should be noted that when the transparent substrate 11 is a single-layer sheet with a core layer, the current collector 12 (joining portion 121) and antenna portion 13 are formed on the surface of the core layer. Furthermore, when the transparent substrate 11 is a laminated sheet, the first outermost layer refers to the layer forming the surface on which the current collector 12 (joining portion 121) and antenna portion 13 are to be formed, and the second outermost layer refers to the back surface of the first outermost layer. From the perspective of adjusting the surface free energy E0, the transparent substrate 11 of this embodiment preferably has a first outermost layer. The following describes the structure of each layer in detail.

[0085] (core layer)

[0086] The material constituting the core layer is not particularly limited, but preferably a material that contributes to improving the mechanical strength of the substrate. The material of this core layer is not particularly limited, and examples thereof include transparent inorganic substrates such as quartz glass, borosilicate glass, soda lime glass, and lead glass; and transparent organic substrates such as acrylates, methacrylates, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycarbonate, polyarylate, polyvinyl chloride, polyethylene, polypropylene, polystyrene, nylon, aromatic polyamide, polyetheretherketone, polysulfone, polyethersulfone, polyimide, and polyetherimide. Among these, the use of polyethylene terephthalate improves productivity (cost reduction) in the manufacture of transparent antennas. Furthermore, the use of polyimide improves heat resistance of the transparent antenna. When using polyimide, it is more preferable to use so-called transparent polyimide, which has excellent visible light transmittance. Furthermore, by using polyethylene terephthalate, polyethylene naphthalate, or quartz glass, there is a tendency for the adhesion between the transparent substrate and the conductive thin wires to be further improved.

[0087] The core layer may be formed from one material or may be laminated with two or more materials. In addition, when the core layer is a multilayer laminated with two or more materials, the substrate may be an organic substrate or an inorganic substrate laminated with each other, or an organic substrate and an inorganic substrate laminated with each other.

[0088] The thickness of the core layer is preferably 5 μm or more and 500 μm or less, and more preferably 10 μm or more and 100 μm or less.

[0089] (First outermost layer)

[0090] When the transparent substrate 11 is a laminate, the first outermost layer is a layer constituting the surface on which the collector portion 12 (joining portion 121) and the antenna portion 13 are to be formed. The material constituting the first outermost layer is not particularly limited, but preferably contributes to improving the adhesion between the core layer and the collector portion 12 (joining portion 121) and the antenna portion 13. In addition, when the transparent substrate 11 is in a form having a first outermost layer and a second outermost layer and not having a core layer, the first outermost layer preferably contributes to improving the adhesion between the second outermost layer and the collector portion 12 (joining portion 121) and the antenna portion 13. It should be noted that when the transparent substrate 11 has a first outermost layer, the surface free energy E0 becomes the surface free energy of the first outermost layer.

[0091] The components contained in this first outermost layer are not particularly limited, and examples thereof include silicon compounds (such as (poly)silanes, (poly)silazanes, (poly)silothianes, (poly)siloxanes, silicon, silicon carbide, silicon oxide, silicon nitride, silicon chloride, silicates, zeolites, silicides, etc.), aluminum compounds (such as aluminum oxide, etc.), magnesium compounds (such as magnesium fluoride), etc.

[0092] Among them, silicon compounds are preferred, and siloxanes are more preferred. By using such components, the surface free energy E0 of the transparent substrate surface where the bonding portion 121 is to be formed is increased, and the transparency and durability of the transparent antenna are also further improved.

[0093] The silicon compound is not particularly limited, and examples thereof include condensates of polyfunctional organosilanes and polycondensates obtained by hydrolyzing polyfunctional organosilanes or oligomers thereof with polyvinyl acetate.

[0094] The polyfunctional organosilane is not particularly limited, and examples thereof include difunctional organosilanes such as dimethyldimethoxysilane, dimethyldiethoxysilane, diethyldimethoxysilane, diethyldiethoxysilane, diphenyldimethoxysilane, and diphenyldiethoxysilane; trifunctional organosilanes such as methyltrimethoxysilane, methyltriethoxysilane, and phenyltrimethoxysilane; and tetrafunctional organosilanes such as tetramethoxysilane and tetraethoxysilane.

[0095] The first outermost layer can be formed by applying a composition containing the components contained in the first outermost layer to the core layer and drying the composition. Alternatively, the first outermost layer can be formed by a vapor phase film forming method such as PVD or CVD. The composition used to form the first outermost layer may contain a dispersant, a surfactant, a binder, etc. as needed.

[0096] The thickness of the first outermost layer is preferably from 0.01 μm to 100 μm, more preferably from 0.01 μm to 10 μm, and even more preferably from 0.01 μm to 1 μm. By setting the thickness of the first outermost layer within the above range, there is a tendency that, in addition to further improving the aforementioned adhesion, the transparency and durability of the transparent antenna are also further improved.

[0097] By laminating the first outermost layer on the core layer, the surface free energy E0 can be adjusted. Furthermore, when the metal component in the ink is sintered using a firing method such as plasma to form the current collecting portion 12 (joining portion 121) and the antenna portion 13, etching of the core layer in areas not covered by the current collecting portion 12 (joining portion 121) and the antenna portion 13 due to the plasma or other means can be prevented. In particular, the use of such firing methods as plasma or other means is preferred because it allows the surface free energy E0 of the openings of the transparent substrate 11 to be set to a predetermined value.

[0098] Furthermore, the first outermost layer preferably has an antistatic function to prevent disconnection of the current collecting portion 12 (joining portion 121) and the antenna portion 13 due to static electricity. To impart the antistatic function to the first outermost layer, the first outermost layer preferably contains at least one of a conductive inorganic oxide and a conductive organic compound.

[0099] (Second outermost layer)

[0100] When the transparent substrate 11 is a laminate, the second outermost layer refers to the back surface of the first outermost layer. The components contained in the second outermost layer are not particularly limited, and examples thereof include melamine compounds, alkyd compounds, fluorine compounds, silicone compounds, polyethylene wax, fatty acids, and fatty acid esters. Preferred are melamine compounds, alkyd compounds, fluorine compounds, and silicone compounds, with melamine compounds and alkyd compounds being more preferred. The use of such components tends to further improve the transparency and durability of the transparent antenna.

[0101] The thickness of the second outermost layer is preferably 0.01 μm to 100 μm, more preferably 0.01 μm to 10 μm, and even more preferably 0.01 μm to 1 μm. When the thickness of the second outermost layer is within the above range, the transparency and durability of the transparent antenna 10 tend to be further improved.

[0102] (Other layers)

[0103] The other layer disposed between the core layer and the first outermost layer, between the core layer and the second outermost layer, or between the first outermost layer and the second outermost layer is not particularly limited, and an easy-adhesion layer may be mentioned, for example. The easy-adhesion layer is used to improve the adhesion between the core layer and the first outermost layer, between the core layer and the second outermost layer, or between the first outermost layer and the second outermost layer.

[0104] 〔Joint〕

[0105] The junction 121 is the tip of the collector 12 and is the region where it is bonded to the semiconductor element 14. The junction 121 (collector 12) is electrically bonded to the antenna 13 and includes a first conductive pattern 300 and a first opening 301 where the first conductive pattern 300 is not formed. Here, the first conductive pattern 300 is a continuous pattern, providing conductivity from any point in the pattern to any other point. It should be noted that the collector 12 may include one or more electrically independent first conductive patterns 300.

[0106] Figure 2 and Figure 4 Show Figure 1 The S1a part and Figure 3 A magnified view of S1b. Figure 2 and Figure 4 , an example is shown in which the collector portion 12 (joining portion 121 ) formed of the first conductive pattern 300 including thick conductive thin wires and the antenna portion 13 formed of the second conductive pattern 400 including thinner conductive thin wires are electrically joined.

[0107] Figure 6 As one embodiment of the joint 121, Figure 2 and Figure 4 An enlarged view of the S2 section. Figure 6 In the figure, the first conductive pattern 300 is shown as a grid pattern formed by a plurality of first conductive fine lines intersecting in a grid-like pattern. However, the first conductive pattern 300 is not limited to this and may be any other pattern in which the first conductive fine lines intersect while maintaining conductivity. Furthermore, the first conductive pattern 300 may be a regular pattern or an irregular pattern. Furthermore, the first conductive fine lines may be straight lines or curved lines.

[0108] The shape of the first opening 301 is not particularly limited, and examples thereof include a triangle; a quadrilateral such as a square, a rectangle, or a rhombus; a pentagon; a hexagon; or a combination of multiple polygons.

[0109] The configuration of the collector portion 12 is not particularly limited, and examples thereof include a configuration in which the collector portion 12 is provided with a size substantially shielded by the semiconductor element 14 so as to connect a plurality of antenna portions 13 (see FIG. Figure 1 ); The semiconductor element 14 is bonded to a portion of the annular collector portion 12, and the antenna portion 13 is provided on the outer periphery of the annular collector portion 12 (reference Figure 3 ); The collector portion 12 is provided at any position of the antenna portion 13. The bonding position (bonding portion 121) of the semiconductor element 14 in the collector portion 12 is not particularly limited, but is preferably a position facing the front end of the collector portion 12.

[0110] [Antenna section 13]

[0111] The antenna portion 13 is electrically bonded to the collector portion 12 (bonding portion 121) and has a second conductive pattern 400 and a second opening 401. The second opening 401 is formed between the patterns and does not form the second conductive pattern 400. The antenna portion 13 exists in the form of an antenna area capable of transmitting and receiving specified electromagnetic waves. Here, the second conductive pattern 400 refers to a continuous pattern having conductivity from any point in the pattern to any other point. It should be noted that the antenna portion 13 can have multiple electrically independent second conductive patterns 400.

[0112] The antenna unit 13 has various shapes depending on its type. The type of antenna unit 13 is not particularly limited, and examples thereof include electric field antennas such as dipole antennas and patch antennas that generate current by changing the electric field, and magnetic field antennas such as loop antennas that generate current by changing the magnetic field.

[0113] The antenna portion 13 can utilize any known shape. For example, linear dipole antennas are not limited to straight lines; various known shapes can be used, including zigzag, meander, helical, and spiral shapes. Furthermore, patch antennas can have any shape, including polygonal and circular, or even shapes with cutouts. Furthermore, the antenna portion 13 can also be a combination of various shapes.

[0114] Furthermore, the antenna portion 13 preferably includes a second conductive pattern having second conductive thin wires. Figure 7 As one embodiment of the antenna unit 13, Figure 2 and Figure 4 An enlarged view of the S3 section. Figure 7 In the figure, the second conductive pattern 400 is shown as a grid pattern formed by a plurality of second conductive fine lines intersecting in a grid-like pattern. However, the second conductive pattern 400 is not limited to this and may be any other pattern in which the second conductive fine lines intersect while maintaining conductivity. Furthermore, the second conductive pattern 400 may be a regular or irregular pattern. Furthermore, the second conductive fine lines may be straight or curved.

[0115] The shape of the portion where the second conductive pattern 400 is not formed, i.e., the second opening 401, is not particularly limited, and examples thereof include triangles; quadrilaterals such as squares, rectangles, and rhombuses; pentagons; hexagons; or shapes formed by combining multiple polygons.

[0116] Figure 1 and Figure 3 This is an example of the configuration of an RF tag when the antenna unit 13 is an electric field antenna. Figure 1 In the embodiment, two antenna parts 13 are formed around the smaller collector part 12 which is substantially shielded by the semiconductor element 14. Figure 3 In the embodiment, the antenna portion 13 is formed so as to surround the ring-shaped power collecting portion 12 . Figure 1 and Figure 3 In the embodiment, the antenna portion 13 has a rectangular shape. Figure 1 and Figure 3 In the embodiment, antenna portion 13 is not formed by applying a solid conductive layer to a flat surface, but rather by using a mesh pattern composed of second openings 401 and second conductive pattern 400. This ensures that antenna portion 13 functions as an electric field antenna while maintaining transparency in the region where the antenna portion is formed.

[0117] (First Conductive Pattern 300 and Second Conductive Pattern 400)

[0118] The first conductive pattern 300 and the second conductive pattern 400 contain a conductive component. There is no particular limitation on the conductive component, and examples thereof include conductive metals and conductive polymers. In addition, the first conductive pattern 300 and the second conductive pattern 400 may contain a non-conductive component. There is no particular limitation on the conductive metal, and examples thereof include gold, silver, copper, and aluminum. Among them, silver or copper is preferred, and relatively inexpensive copper is more preferred. By using such a conductive metal, there is a tendency for the transparent antenna to have better conductivity. In addition, as the conductive polymer, known substances can be used, and examples thereof include polyacetylene, polythiophene, and the like.

[0119] The non-conductive component is not particularly limited, and examples thereof include metal oxides, metal compounds, and organic compounds. More specifically, these non-conductive components include components derived from the components contained in the ink described below, and are metal oxides, metal compounds, and organic compounds that remain in the conductive fine wires after firing.

[0120] The content ratio of the conductive component in the first conductive pattern 300 and the second conductive pattern 400 is preferably 50% by mass or more, more preferably 60% by mass or more, and even more preferably 70% by mass or more. The upper limit of the content ratio of the conductive component is not particularly limited and is 100% by mass. In addition, the content ratio of the non-conductive component in the first conductive pattern 300 and the second conductive pattern 400 is preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably 30% by mass or less. The lower limit of the content ratio of the non-conductive component is not particularly limited and is 0% by mass.

[0121] (Line width W)

[0122] The line width W of the first and second conductive thin lines in the first conductive pattern 300 and the second conductive pattern 400 is the line width W when the conductive thin lines are projected onto the surface of the transparent substrate 11 from the side of the transparent substrate 11 on which the conductive patterns are arranged. In the case of a conductive thin line having a trapezoidal cross-section with a longer base on the interface side with the transparent substrate 11, the line width W is the width of the surface of the conductive thin line in contact with the transparent substrate 11.

[0123] The line width W1 of the first conductive fine wire is preferably 0.5 to 200 μm, more preferably 1 to 150 μm, and even more preferably 2 to 100 μm. By making the line width W1 of the first conductive fine wire within the above range, there is a tendency for the bonding to be further improved and the antenna characteristics such as gain to be further improved. In addition, by making the line width W1 of the first conductive fine wire be less than 200 μm, there is a tendency for the visual recognition of the first conductive pattern 300 to be further reduced and the transparency of the collector 12 (junction 121) to be further improved.

[0124] The line width W2 of the second conductive fine wire is preferably 0.25 to 7.5 μm, more preferably 0.25 to 5.0 μm, further preferably 0.25 to 4.0 μm, and particularly preferably 0.50 to 3.0 μm. By making the line width W2 of the second conductive fine wire 0.25 μm or more, there is a tendency for the conductivity of the antenna portion 13 to be further improved. In addition, the reduction in conductivity caused by oxidation, corrosion, etc. on the surface of the conductive fine wire can be fully suppressed. On the other hand, by making the line width W2 of the second conductive fine wire 10.0 μm or less, there is a tendency that the visual recognition of the second conductive pattern 400 is further reduced and the transparency of the antenna portion 13 is further improved.

[0125] It should be noted that, when the line width W1 and / or the line width W2 in the first conductive pattern 300 and / or the second conductive pattern 400 is not a fixed value but a plurality of values, it is preferred that all the line widths W1 and / or the line widths W2 satisfy the above range.

[0126] (Height T)

[0127] The height T1 of the first conductive fine wire and the height T2 of the second conductive fine wire are each independently preferably 0.05 to 1.0 μm, more preferably 0.07 to 0.8 μm, and further preferably 0.1 to 0.5 μm. By making the heights T1 and T2 greater than 0.05 μm, there is a tendency for the conductivity to be further improved. In addition, there is a tendency to fully suppress the reduction in conductivity caused by oxidation, corrosion, etc. on the surface of the conductive fine wire. On the other hand, by making the heights T1 and T2 less than 1.0 μm, there is a tendency to exhibit high transparency at a wide viewing angle.

[0128] It should be noted that, in the first conductive pattern 300 and / or the second conductive pattern 400 , when the height T1 and / or the height T2 are not fixed values ​​but multiple values, it is preferred that all the heights T1 and / or the heights T2 satisfy the above range.

[0129] (Pitch P)

[0130] The pitch P1 of the first conductive thin wires is preferably 0.5 to 25 μm, more preferably 1.0 to 10 μm, and even more preferably 2.0 to 7.0 μm. By setting the pitch P1 within the above range, there is a tendency for further improved bonding and antenna characteristics such as gain to be further improved. It should be noted that the pitch P is the distance between the conductive thin wires.

[0131] The pitch P2 of the second conductive thin wires is preferably 20 to 1000 μm, more preferably 40 to 750 μm, and even more preferably 60 to 300 μm. When the pitch P2 is 20 μm or greater, the transparency of the antenna portion 13 tends to be further improved. Furthermore, when the pitch P2 is 1000 μm or less, the conductivity tends to be further improved.

[0132] The pitch P1 of the first conductive fine wires is preferably smaller than the pitch P2 of the second conductive fine wires. The difference (P2-P1) is preferably 30 to 1000 μm, more preferably 50 to 500 μm, and even more preferably 100 to 300 μm. By making the difference (P2-P1) within the above range, there is a tendency to reduce the visual recognition of the joint and further improve the appearance design.

[0133] It should be noted that, when the pitch P1 and / or the pitch P2 in the first conductive pattern 300 and / or the second conductive pattern 400 is not a fixed value but a plurality of values, it is preferred that all the pitches P1 and / or the pitches P2 satisfy the above range.

[0134] (Occupancy rate S)

[0135] The area occupancy ratio S1 of the first conductive pattern 300 is preferably 30 to 90%, more preferably 30 to 80%, further preferably 40 to 80%, and particularly preferably 50 to 80%. By setting the area occupancy ratio S1 within the above range, there is a tendency for further improved bonding and antenna characteristics such as gain to be further improved.

[0136] The area occupancy ratio S2 of the second conductive pattern 400 is preferably 0.1 to 10.0%, more preferably 0.5 to 5.0%, and even more preferably 1.0 to 3.0%. When the area occupancy ratio S2 is 0.1% or greater, the characteristics of the antenna portion 13 tend to be further improved. Furthermore, when the area occupancy ratio S2 is 10.0% or less, the transparency of the antenna portion 13 tends to be further improved.

[0137] The first conductive pattern's area ratio S1 is preferably greater than the second conductive pattern's area ratio S2. The difference (S1-S2) is preferably 3-50%, more preferably 9-50%, and even more preferably 15-50%. By keeping the difference (S1-S2) within this range, the visual recognition of the joint portion tends to be reduced, while the design quality tends to be improved.

[0138] It should be noted that the "area ratio S occupied by the conductive pattern" can be calculated by using the following formula for the area on the transparent substrate where the conductive pattern is formed. The area on the transparent substrate where the conductive pattern is formed is: Figure 4 The range shown as S2 and S3 does not include edge portions where the conductive pattern is not formed.

[0139] Conductive pattern area ratio S

[0140] =(area occupied by the conductive pattern / area of ​​the transparent substrate 11)×100

[0141] The line width, height, pitch, and area occupancy of the conductive pattern can be confirmed on the surface or cross-section of the transparent antenna using an electron microscope, laser microscope, optical microscope, or the like. Methods for adjusting the line width and pitch of the conductive pattern to the desired range include adjusting the grooves of the plate used in the transparent antenna manufacturing method described below and adjusting the average particle size of the metal particles in the ink.

[0142] (shape)

[0143] The cross-sectional shapes of the first conductive fine wire and the second conductive fine wire can be defined by the width W and height T of the conductive fine wire. With the height T of the conductive fine wire as a reference, the height from the interface between the transparent substrate 11 and the conductive fine wire is defined as 0.50T and 0.90T. In addition, the width of the conductive fine wire at the height of 0.50T is defined as W. 0.50 , the width of the conductive thin line at a height of 0.90T is set to W 0.90 At this time, W 0.50 / W0 is preferably 0.70 to 0.99, more preferably 0.75 to 0.99, and even more preferably 0.80 to 0.95. 0.90 / W 0.50 It is preferably 0.50 to 0.95, more preferably 0.55 to 0.90, and even more preferably 0.60 to 0.85. 0.50 / W0 is preferably greater than W 0.90 / W 0.50That is, it is preferred that the width of the conductive fine wire decreases from a height position at a thickness of 0.50T from the interface of the conductive fine wire on the transparent substrate 11 side toward a height position at a thickness of 0.90T from the interface of the conductive fine wire on the transparent substrate 11 side.

[0144] As described later, the transparent antenna of this embodiment can be formed using ink through printing. The conductive thin wires formed by this method have the characteristic shape described above. Other methods for forming the conductive thin wires include nanoimprinting, photolithography, and other methods using other wiring. However, the conductive thin wires produced by these methods differ from those formed by printing in the aforementioned shape.

[0145] (Sheet resistance)

[0146] The sheet resistance of the first conductive pattern 300 and the second conductive pattern 400 is preferably greater than 0.1Ω / sq and less than 1000Ω / sq, more preferably greater than 0.1Ω / sq and less than 500Ω / sq, further preferably greater than 0.1Ω / sq and less than 100Ω / sq, further preferably greater than 0.1Ω / sq and less than 20Ω / sq, and even more preferably greater than 0.1Ω / sq and less than 10Ω / sq.

[0147] The sheet resistance of a transparent antenna can be measured using the following method. First, the portion of the transparent antenna on which the conductive pattern is disposed is cut into a rectangular shape to obtain a measurement sample. Collecting portions for measuring the sheet resistance, which are electrically connected to the conductive pattern, are formed at both ends of the obtained measurement sample, and the resistance R (Ω) between the collecting portions provided at the two ends is measured. The sheet resistance R (Ω) can be calculated using the following formula using the above resistance R (Ω), the length L (mm) in the width direction corresponding to the distance between the collecting portions of the measurement sample, and the length D (mm) in the depth direction. s (Ω / sq).

[0148] R s =R / L×D

[0149] There is a tendency that increasing the height of the conductive thin wires reduces the sheet resistance of the transparent antenna 10. Alternatively, it can be adjusted by selecting the type of metal material constituting the conductive thin wires.

[0150] (Visible light transmittance)

[0151] The visible light transmittance VT1 of the first conductive pattern 300 is preferably 30 to 80%, more preferably 40 to 75%, and even more preferably 45 to 70%. The visible light transmittance can be measured by calculating the transmittance in the visible light range (360 to 830 nm) according to the total light transmittance specified in JIS K7361-1:1997.

[0152] The visible light transmittance VT2 of the second conductive pattern 400 is preferably 80% or more and 100% or less, and more preferably 90% or more and 100% or less.

[0153] There is a tendency that the visible light transmittance of the transparent antenna 10 is improved by reducing the line width of the conductive pattern or increasing the occupied area ratio.

[0154] [Method for manufacturing transparent antenna]

[0155] Examples of methods for manufacturing a transparent antenna include a method comprising the following steps: a patterning step of forming a pattern on the transparent substrate 11 using ink containing a metal component; and a firing step of firing the ink to form the current collecting portion 12 (joining portion 121) and the antenna portion 13. Furthermore, from the perspective of adjusting the surface free energy of the first opening 301, a surface treatment step of treating the surface of the transparent substrate 11 may be included.

[0156] 〔Surface treatment process〕

[0157] In the surface treatment step, from the viewpoint of adjusting the surface free energy, a first outermost layer may be provided on one surface of the core layer or the surface roughness of the transparent substrate 11 may be adjusted.

[0158] The method for forming the first outermost layer is not particularly limited, and examples thereof include methods of forming a film of the components constituting the first outermost layer on one surface of the core layer using a vapor phase film forming method such as PVD or CVD. Another example of a method of forming the first outermost layer by applying a composition containing the components forming the first outermost layer to one surface of the core layer and drying the composition is also included.

[0159] Generally, there are no particular limitations on methods for increasing the surface roughness of the smooth transparent substrate 11. Examples include providing an easy-adhesion layer having a large surface roughness between the core layer and the first outermost layer, and forming the first outermost layer on the easy-adhesion layer. Thus, the first outermost layer will reflect the surface roughness of the easy-adhesion layer.

[0160] [Pattern Formation Process]

[0161] The pattern forming process is a process for forming a pattern using ink containing a metal component. The pattern forming process is not particularly limited as long as it involves a plate-based printing method using a plate with grooves having the desired conductive pattern. For example, the process includes: applying ink to the surface of a transfer medium; placing the ink-coated transfer medium surface against the raised surface of a relief plate, pressing and contacting the surface to transfer the ink on the transfer medium surface to the raised surface of the relief plate; and placing the transfer medium surface, where ink remains, against the surface of a transparent substrate 11, pressing and contacting the surface to transfer the ink remaining on the transfer medium surface to the surface of the transparent substrate 11. Note that if the transparent substrate 11 has a first outermost layer, the ink is transferred to the surface of the first outermost layer.

[0162] (ink)

[0163] The ink used in the pattern forming step comprises a conductive component and a solvent, and may optionally contain a surfactant, a dispersant, a reducing agent, etc. When the conductive component is a metal component, the metal component may be contained in the ink in the form of metal particles or a metal complex.

[0164] The average primary particle size of the metal particles is preferably less than 100 nm, more preferably less than 50 nm, and further preferably less than 30 nm. In addition, the lower limit of the average primary particle size of the metal particles is not particularly limited, and more than 1 nm can be listed. By making the average primary particle size of the metal particles less than 100 nm, the line width W of the obtained conductive fine wire can be further narrowed. It should be noted that "average primary particle size" refers to the particle size of one metal particle (so-called primary particle), which is different from the particle size of the aggregate (so-called secondary particle) formed by the aggregation of multiple metal particles, that is, the average secondary particle size.

[0165] The metal particles are not particularly limited, and examples thereof include metal oxides such as copper oxide, metal compounds, and core / shell particles having a copper core and a copper oxide shell. The form of the metal particles can be appropriately determined from the perspectives of dispersibility and sinterability.

[0166] The surfactant is not particularly limited, and examples thereof include fluorine-based surfactants. The use of such surfactants tends to improve the coating properties of the film on the transfer medium (blanket) and the smoothness of the applied ink, resulting in a more uniform coating. It should be noted that the surfactant is preferably configured to disperse the metal component and not easily leave residue during firing.

[0167] The dispersant is not particularly limited, and examples thereof include dispersants that form non-covalent bonds or interactions with the metal component surface, and dispersants that form covalent bonds with the metal component surface. Examples of functional groups that form non-covalent bonds or interactions include dispersants having a phosphate group. The use of such dispersants tends to further improve the dispersibility of the metal component.

[0168] Furthermore, examples of solvents include alcohol solvents such as monohydric alcohols and polyhydric alcohols; alkyl ether solvents; hydrocarbon solvents; ketone solvents; ester solvents, etc. These can be used alone or in combination of one or more. Examples include the combined use of monohydric alcohols having less than 10 carbon atoms and polyhydric alcohols having less than 10 carbon atoms. By using such solvents, there is a tendency that the coating properties of the ink on the transfer medium (blanket), the transfer properties of the ink from the transfer medium to the relief plate, the transfer properties of the ink from the transfer medium to the transparent substrate, and the dispersibility of the metal component are further improved. It should be noted that the solvent is preferably a structure that can disperse the metal component and is not likely to remain during firing.

[0169] 〔Firing process〕

[0170] In the firing process, for example, the metal component in the ink transferred to the surface of the transparent substrate 11 is sintered to form the collector portion 12 (joining portion 121) and the antenna portion 13. The firing method is not particularly limited as long as the metal component is welded to form a sintered film of the metal component. Firing can be carried out, for example, using a firing furnace, or using plasma, a heating catalyst, ultraviolet rays, vacuum ultraviolet rays, electron beams, infrared lamp annealing, flash lamp annealing, laser, etc. In the case where the resulting sintered film is easily oxidized, it is preferably fired in a non-oxidizing atmosphere. In addition, in the case where metal oxides and the like are difficult to reduce using only a reducing agent that may be contained in the ink, it is preferably fired in a reducing atmosphere.

[0171] A non-oxidizing atmosphere refers to an atmosphere that does not contain oxidizing gases such as oxygen, and there are inert atmospheres and reducing atmospheres. Inert atmospheres refer to atmospheres filled with inert gases such as argon, helium, neon, and nitrogen. In addition, a reducing atmosphere refers to an atmosphere in which reducing gases such as hydrogen and carbon monoxide are present. These gases can be filled into a firing furnace to form a closed system and the ink coating film (dispersion coating film) can be fired. In addition, the firing furnace can be made into a circulation system, and the dispersion coating film can be fired while circulating these gases. When the dispersion coating film is fired in a non-oxidizing atmosphere, it is preferred that the firing furnace be temporarily vacuumed to remove the oxygen in the firing furnace, and replaced with a non-oxidizing gas. In addition, firing can be carried out in a pressurized atmosphere or in a reduced pressure atmosphere.

[0172] The firing temperature is not particularly limited, but is preferably 20°C or higher and 400°C or lower, more preferably 50°C or higher and 300°C or lower, and even more preferably 80°C or higher and 200°C or lower. By setting the firing temperature to 400°C or lower, a substrate with low heat resistance can be used, which is preferred. In addition, by setting the firing temperature to 20°C or higher, there is a tendency for the formation of the sintered film to be fully carried out and the conductivity to be improved, which is preferred. It should be noted that the obtained sintered film contains a conductive component derived from the metal component, and in addition, it may contain a non-conductive component depending on the components used in the ink and the firing temperature.

[0173] [RF Tag]

[0174] The RF tag 100 of the present embodiment includes the transparent antenna 10 described above and a semiconductor element 14 electrically bonded to a bonding portion 121 of the transparent antenna 10 . Figure 7 A cross-sectional view of the RF tag 100 of this embodiment is shown in FIG. Figure 7 As shown, the semiconductor element 14 is preferably electrically bonded to the bonding portion 121 via an anisotropic conductive adhesive 15 such as an anisotropic conductive paste or an anisotropic conductive film.

[0175] Figure 1 and 2 , an RF tag 100 is shown. This RF tag 100 is a passive tag that does not have a built-in battery and uses the radio waves received from the reader / writer as its energy source. The RF tag 100 of this embodiment can also be an active tag that further has a built-in battery (not shown) and uses the power from the battery as a power source for transmission and reception and internal circuits; or a semi-passive tag that has other sensors built in and uses the battery as a power source for the sensors. It should be noted that in this embodiment, the RF tag refers to a tag that can transmit and receive specific frequencies by having the above-mentioned transparent antenna 10. Therefore, even if it is called an IC tag, as long as it meets the above-mentioned structure, it is included in the RF tags of this embodiment.

[0176] The semiconductor element 14 may be a known element depending on the application of the RF tag 100. The configuration of the semiconductor element 14 is not particularly limited, and the semiconductor element 14 may include functional units such as a storage unit, a power rectifier unit, a receiver unit, a controller unit, and a transmitter unit.

[0177] The following describes an example of the operation of each functional unit and the passive RF tag 100 of this embodiment. First, the antenna 13 of the RF tag 100 receives radio waves from a reader / writer, generating an electromotive force through electromagnetic induction and other means. This electromotive force activates the semiconductor element 14 of the RF tag 100. At this point, the power rectifier converts the AC input to the antenna 13 into DC, supplying power to the circuitry of the semiconductor element 14. Simultaneously, the receiver demodulates the carrier wave received from the reader / writer into a signal train and transmits this signal train to the control unit. Based on the signal train received from the receiver, the control unit reads and writes information to the storage unit or transmits the processed information results in the form of a signal train to the transmitter. The storage unit stores various information depending on the RF tag's intended use, such as product information. Finally, the transmitter demodulates the signal train received from the control unit into a carrier wave and transmits it from the antenna 13. The reader / writer's antenna receives this carrier wave and processes the information. It should be noted that in this embodiment, RFID refers to a system consisting of an RF tag and a reader / writer.

[0178] The frequency bands that the RF tag 100 of this embodiment can operate in are not particularly limited. Examples include the LF band (medium wave band): 120-130 kHz, the HF band (short wave band): 13.56 MHz, the UHF band (ultra-high frequency band): 900 MHz, and the microwave band: 2.45 GHz. The type of antenna unit 13 can be appropriately adjusted depending on the frequency band used. For example, a loop antenna can be used when using the HF band, while a dipole antenna can be used when using the UHF band.

[0179] The transmission and reception method that can be used by the RF tag 100 of this embodiment is not limited to the above-mentioned radio wave method, and the following methods can be used: an electromagnetic coupling method in which high frequency is applied to the coils respectively provided on the transmitting side / receiving side so that the generated mutual induction carries information; an electromagnetic induction method in which the magnetic field generated near the antenna carries information and exchanges information.

[0180] The diameter d of the conductive fine particles contained in the anisotropic conductive adhesive is preferably 3.0 to 10 μm, more preferably 4.0 to 9.0 μm. When the diameter d of the conductive fine particles is within the above range, the bonding property tends to be further improved.

[0181] Furthermore, the pitch P1 of the first conductive pattern formed in the current collecting portion 12 (joining portion 121 ), the thickness T1 thereof, and the diameter d of the conductive fine particles preferably satisfy the following formula (1).

[0182] (P1 / 2) 2 <(d / 2) 2 -(d / 2-T1) 2 Formula (5)

[0183] Example

[0184] Hereinafter, the present invention will be described in more detail using Examples and Comparative Examples. However, the present invention is not limited to the following Examples at all.

[0185] [Example 1]

[0186] A polyethylene terephthalate (PET) film (manufactured by Toyobo Co., Ltd., product name COSMOSHINE A4100, film thickness 50 μm) having an easy-adhesive layer formed on one side was used as the core layer. A composition consisting of 2 wt% silicon oxide nanoparticles, 1 wt% of a conductive organosilane compound, 65 wt% of 2-propanol, 25 wt% of 1-butanol, and 7 wt% of water was applied to one side without the easy-adhesive layer, and the film was dried to form a silicon oxide-containing film having a thickness of 50 nm containing silicon oxide as the first outermost layer, thereby obtaining substrate A.

[0187] Next, 20 parts by mass of cuprous oxide nanoparticles having a particle size of 21 nm, 4 parts by mass of a dispersant (BYK-Chemie, product name: Disperbyk-145), 1 part by mass of a surfactant (AGC Seimi Chemical, product name: S-611), and 75 parts by mass of ethanol were mixed and dispersed to prepare an ink having a cuprous oxide nanoparticle content of 20% by mass.

[0188] Ink is then applied to the surface of a transfer medium. This surface is then placed against a plate with a conductive groove pattern, pressed against it, and brought into contact with it. This causes a portion of the ink on the transfer medium surface to transfer to the plate's raised surfaces. Subsequently, the surface of the transfer medium with the remaining ink is placed against a substrate A, and pressed against it, transferring the desired conductive pattern of ink to the first outermost layer of the substrate A.

[0189] Next, the conductive patterned ink (dispersion coating film) was fired at room temperature using a Nova Centrix Pulseforge 1300 flash lamp annealing. The antenna portion's conductive pattern was a square grid with a line width W2 of 3.0 μm, a height T2 of 0.5 μm, an opening pitch P2 of 60 μm, and an area occupancy S2 of 10%. The bonding portion's conductive pattern was a square grid with a line width W1 of 1.0 μm, a height T1 of 0.5 μm, an opening pitch P1 of 3.0 μm, and an area occupancy S1 of 56%.

[0190] In addition, the antenna part is Figure 1The dipole antenna shown in the figure has two rectangular conductive patterns with a longitudinal dimension of 49 mm in the long side direction and a lateral dimension of 10 mm in the short side direction, arranged with their short sides facing each other and at a spacing of 2 mm, and a gap between the joints formed between the two conductive patterns is set to 150 μm.

[0191] It should be noted that regarding the conductive thin wires of the bonding portion and the antenna portion, W 0.50 / W0 is greater than W 0.90 / W 0. 50. In addition, the surface free energy E1 is 57mJ / m 2 , the surface free energy E0 is 76mJ / m 2 .

[0192] [Example 2]

[0193] A transparent dipole antenna was obtained in the same manner as in Example 1 except that the conductive pattern of the bonding portion was formed in a square grid shape, the line width W1 was set to 3 μm, the opening pitch P1 was set to 6 μm, and the area occupation ratio S1 was set to 75%.

[0194] [Example 3]

[0195] A transparent dipole antenna was obtained in the same manner as in Example 2 except that a quartz glass substrate having a thickness of 0.1 mm was used as the substrate.

[0196] [Example 4]

[0197] A transparent dipole antenna was obtained in the same manner as in Example 2 except that polyethylene naphthalate (PEN) (manufactured by TOYOBO FILM SOLUTIONS, product name TEONEX Q51-A4, film thickness 50 μm) was used as the substrate.

[0198] [Example 5]

[0199] A transparent dipole antenna was obtained in the same manner as in Example 2 except that polyethylene naphthalate (PEN) (manufactured by TOYOBO FILM SOLUTIONS, product name TEONEX Q51-A4, film thickness 50 μm) was used as the substrate and the firing step was carried out using a plasma firing machine.

[0200] [Comparative Example 1]

[0201] A transparent antenna was obtained by the same operation as in Example 1 except that the first outermost layer was not formed. The surface free energy E1 was 57 mJ / m 2 , the surface free energy E0 is 47mJ / m 2 .

[0202] [Comparative Example 2]

[0203] As in Example 1, the same conductive patterned ink as in Example 1 was transferred to the first outermost layer of Substrate A. Subsequently, the same composition as used for the first outermost layer (2% by weight of silicon oxide nanoparticles, 1% by weight of a conductive organosilane compound, 65% by weight of 2-propanol, 25% by weight of 1-butanol, and 7% by weight of water) was applied and dried to form a conductive pattern. A 50 nm thick silicon oxide-containing film was formed on both surfaces of Substrate A. Flash lamp annealing was then performed as in Example 1. The electrode surface was covered with the silicon oxide-containing film. Although no electrical continuity was achieved, the filling and bleeding properties of the conductive adhesive could be evaluated.

[0204] [Reference Example 1]

[0205] A transparent dipole antenna was obtained in the same manner as in Example 1 except that the conductive pattern of the bonding portion was formed in a square grid shape, with a line width W1 of 10 μm, an opening pitch P1 of 3 μm, and an area occupation ratio S1 of 95%.

[0206] [Determination of the dispersion term γSD and polar term γSP of surface free energy]

[0207] The following describes a method for measuring the dispersion terms γSD and γSP of surface free energy.

[0208] The surface of the substrates prepared in the Examples and Comparative Examples where the bonding portion 121 was to be formed was used as the measurement sample. The dispersion term γSD and the polar term γSP of the surface free energy were calculated as the average of three measurements. First, 2 μL each of pure water and diiodomethane, two solvents with known surface tension γL, dispersion term γLD, and polar term γLP, were added dropwise to the measurement sample.

[0209] Using a digital microscope (VHX-100 manufactured by KEYENCE), droplets of two solvents added to the measurement sample were observed and photographed from the horizontal direction. The contact angle between the measurement sample and the droplet was directly measured using the measurement software included with the digital microscope to obtain the contact angles of the two solvents.

[0210] The contact angle θ, the surface tension of water and diiodomethane γ LV , the dispersion term γ of surface tension LV d , the polar term of surface tension γ LV p Substituting into the following equation (4), solving the resulting simultaneous equations, the dispersion term γ of the surface free energy of the measurement sample is obtained. SV d , γSV p .

[0211] γ LV (1+cosθ) / 2=(γ SV d ×γ LV d ) 0.5 +(γ SV p ×γ LV p ) 0.5 (4)

[0212] Line width, spacing, and area occupancy rate

[0213] The line width, space, and area occupancy rate were calculated from the planar photographs taken with an optical microscope.

[0214] [RF Tag]

[0215] A semiconductor element was bonded to the bonding portion of the transparent antenna obtained as described above using an anisotropic conductive paste (TAP0644F manufactured by KYOCERA Corporation) to obtain an RF tag.

[0216] [Poor bonding reliability and appearance]

[0217] The joints of Examples 1 to 5, Comparative Examples 1 and 2, and Reference Example 1 were observed from the back side of the transparent substrate using a digital microscope (VHX-100, manufactured by KEYENCE). The joints of Examples 1 to 5 showed no air bubbles trapped in the substrate openings, ensuring bonding reliability. The antenna, joint, and semiconductor element were electrically connected and conductive, enabling reception of electromagnetic waves with a frequency of 800 MHz to 1000 MHz (Joint Reliability: Rated 0 in Table 1). Furthermore, in Examples 1 to 3, the anisotropic conductive paste did not protrude from the joints into the antenna, resulting in excellent appearance (Appearance: Rated 0 in Table 1). In Examples 4 and 5, slight protrusion of the anisotropic conductive paste from the joints into the antenna was observed, but this did not significantly detract from the appearance of the transparent RF tag (Appearance: Rated △ in Table 1).

[0218] On the other hand, in Comparative Example 1, air bubbles were observed trapped in the joint, indicating poor bonding reliability (evaluated as "×" in Table 1). Furthermore, anisotropic conductive paste was observed to overflow from the joint toward the antenna portion, impairing the aesthetic appeal of the transparent RF tag (evaluated as "×" in Table 1). Furthermore, in Comparative Example 1, with this connectivity, variations in antenna characteristics were expected.

[0219] In Comparative Example 2, air bubbles were observed in the joint. Given the electrical conductivity of the joint, good joint reliability would be expected (joint reliability evaluation (○) in Table 1). However, significant overflow of the anisotropic conductive paste from the joint to the antenna portion was observed, impairing the appearance of the transparent RF tag (Appearance: × in Table 1).

[0220] No bubbles were observed in the joint of Reference Example 1, ensuring bonding reliability. The antenna, joint, and semiconductor element were electrically connected and conductive, enabling reception of electromagnetic waves with a frequency range of 800 MHz to 1000 MHz (bonding reliability: evaluated as 0 in Table 1). However, significant overflow of the anisotropic conductive paste from the joint into the antenna was observed, impairing the aesthetic appeal of the transparent RF tag (Appearance: × in Table 1). Because the conductive pattern area of ​​the joint was excessively large, it is speculated that the anisotropic conductive paste easily leaked along the conductive pattern into the antenna.

[0221] [Table 1]

[0222]

[0223] Industrial applicability

[0224] The present invention has industrial applicability as an RF tag that can be used for RFID, particularly as an RF tag used in applications requiring a design that utilizes transparency.

[0225] Description of Reference Numerals

[0226] 10…transparent antenna, 11…transparent substrate, 12…collecting portion, 121…joining portion, 13…antenna portion, 14…semiconductor element, 15…anisotropic conductive adhesive, 21…conductive fine particles, 22…resin binder, 100…RF tag, 300…first conductive pattern, 301…first opening, 400…second conductive pattern, 401…second opening.

Claims

1. A transparent antenna comprising a transparent substrate, an antenna portion disposed on the transparent substrate, and a bonding portion electrically bonded to the antenna portion. The bonding portion includes a first conductive pattern and a first opening portion where the first conductive pattern is not formed. The antenna portion includes a second conductive pattern and a second opening portion where the second conductive pattern is not formed. The surface free energy E1 of the first conductive pattern is 60 mJ / m 2 the following, The surface free energy E0 of the transparent substrate at the first opening is greater than the surface free energy E1.

2. The transparent antenna according to claim 1, wherein The surface free energy E1 of the first conductive pattern is 10 to 60 mJ / m 2 the following.

3. The transparent antenna according to claim 1, wherein: The surface free energy E1 of the first conductive pattern is 20 to 60 mJ / m 2 the following.

4. The transparent antenna according to claim 1, wherein The surface free energy E1 of the first conductive pattern is 30 to 60 mJ / m 2 the following.

5. The transparent antenna according to claim 1, wherein The transparent substrate is selected from a single-layer sheet with a core layer, a laminated sheet with a core layer and a first outermost layer, a laminated sheet with a core layer and a second outermost layer, a laminated sheet with a first outermost layer and a second outermost layer, and a laminated sheet with a core layer and a first outermost layer and a second outermost layer.

6. The transparent antenna according to claim 1, wherein The first conductive pattern includes first conductive thin wires having a line width W1 of 0.5 μm or more and 200 μm or less.

7. The transparent antenna according to claim 1, wherein: The second conductive pattern includes second conductive thin wires having a line width W2 of 0.25 μm or more and 5.0 μm or less.

8. The transparent antenna according to claim 7, wherein: The line width W2 is greater than or equal to 0.25 μm and less than or equal to 4.0 μm.

9. The transparent antenna according to claim 7, wherein: The line width W2 is greater than or equal to 0.50 μm and less than or equal to 3.0 μm.

10. The transparent antenna according to any one of claims 1 to 9, wherein The height T1 of the first conductive pattern is greater than or equal to 0.05 μm and less than or equal to 1.0 μm. A height T2 of the second conductive pattern is greater than or equal to 0.05 μm and less than or equal to 1.0 μm.

11. The transparent antenna according to claim 10, wherein: The height T1 of the first conductive pattern is greater than or equal to 0.07 μm and less than or equal to 0.8 μm. A height T2 of the second conductive pattern is greater than or equal to 0.07 μm and less than or equal to 0.8 μm.

12. The transparent antenna according to claim 10, wherein: The height T1 of the first conductive pattern is greater than or equal to 0.1 μm and less than or equal to 0.5 μm. A height T2 of the second conductive pattern is greater than or equal to 0.1 μm and less than or equal to 0.5 μm.

13. The transparent antenna according to any one of claims 1 to 9, wherein: The first conductive pattern has first conductive thin lines, and the second conductive pattern has second conductive thin lines. The pitch P1 of the first conductive thin wires is smaller than the pitch P2 of the second conductive thin wires. The pitch P1 is greater than or equal to 1.0 μm and less than or equal to 10 μm. The pitch P2 is greater than or equal to 20 μm and less than or equal to 1000 μm.

14. The transparent antenna according to claim 13, wherein: The pitch P1 is greater than or equal to 2.0 μm and less than or equal to 7.0 μm.

15. The transparent antenna according to claim 13, wherein The pitch P2 is greater than or equal to 40 μm and less than or equal to 750 μm.

16. The transparent antenna according to claim 13, wherein: The pitch P2 is greater than or equal to 60 μm and less than or equal to 300 μm.

17. The transparent antenna according to claim 13, wherein: The pitch P2 of the second conductive thin wires minus the pitch P1 of the first conductive thin wires is 30 to 1000 μm.

18. The transparent antenna according to claim 13, wherein The pitch P2 of the second conductive thin wires minus the pitch P1 of the first conductive thin wires is 50 to 500 μm.

19. The transparent antenna according to claim 13, wherein: The pitch P2 of the second conductive thin wires minus the pitch P1 of the first conductive thin wires is 100 to 300 μm.

20. The transparent antenna according to any one of claims 1 to 9, wherein The area ratio S1 of the first conductive pattern per unit area is greater than the area ratio S2 of the second conductive pattern per unit area. The occupied area ratio S1 is 30% or more and 90% or less, The above-mentioned occupied area ratio S2 is 0.1% or more and 10.0% or less.

21. The transparent antenna according to claim 20, wherein: The area ratio S1 of the first conductive pattern per unit area minus the area ratio S2 of the second conductive pattern per unit area is 3 to 50%.

22. The transparent antenna according to claim 20, wherein The area ratio S1 of the first conductive pattern per unit area minus the area ratio S2 of the second conductive pattern per unit area is 9 to 50%.

23. The transparent antenna according to claim 20, wherein The area ratio S1 of the first conductive pattern per unit area minus the area ratio S2 of the second conductive pattern per unit area is 15 to 50%.

24. The transparent antenna according to any one of claims 1 to 9, wherein The difference between the surface free energy E0 and the surface free energy E1 (E0-E1) is 10-30 mJ / m 2 .

25. The transparent antenna according to any one of claims 1 to 9, wherein The difference between the surface free energy E0 and the surface free energy E1 (E0-E1) is 15-25 mJ / m 2 .

26. The transparent antenna according to any one of claims 1 to 9, wherein The difference between the surface free energy E0 and the surface free energy E1 (E0-E1) is 17-22 mJ / m 2 .

27. An RF tag comprising: The transparent antenna according to any one of claims 1 to 26; and A semiconductor element is electrically connected to the connecting portion of the transparent antenna.

28. The RF tag according to claim 27, wherein The semiconductor element is electrically bonded to the bonding portion via an anisotropic conductive adhesive.

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