JP5444988B2 - antenna - Google Patents

Description

  The present invention relates to an antenna for receiving terrestrial and satellite broadcasting, transmission / reception of a wireless LAN, and transmission / reception via an external network, and more particularly to a transparent antenna with reduced antenna visibility.

Recently, various types of broadcasting such as terrestrial digital broadcasting have been provided, and transmission / reception of wireless LANs and transmission / reception via external networks has been widespread, and the demand for small antennas tends to increase.
The antenna is attached to a casing or a display screen of a mobile phone, a window glass of a building or a car, an RFID (radio frequency identification) tag, and the like, and transmits and receives radio waves according to each purpose.
Further, the antenna is required not to impair the appearance and design of the object to be attached. Therefore, the antenna is required to have a low visibility and not obstruct the field of view in any of the above applications, that is, a highly transparent one.

  Patent Document 1 discloses a transparent antenna for a display having an antenna pattern formed in a planar shape on the surface of a substrate (base material). Further, as a method for forming the antenna pattern, a method of printing a conductive resin paste on a substrate by a technique such as screen printing is described. However, when an antenna pattern is formed on a substrate by the above method, the antenna pattern is thinned and the pattern shape faithful reproducibility is insufficient, and sufficient transparency and high conductivity (reduced surface resistance value). ) Is difficult to achieve.

  On the other hand, there is also a method of forming an antenna pattern by bonding a metal foil to a substrate with a transparent adhesive and then chemically etching the metal foil into a mesh shape by a photolithography method. According to this method, the antenna pattern is thinned, the pattern shape is faithfully reproducible, and sufficient transparency and high conductivity (reduction in surface resistance value) can be achieved. However, copper (copper foil) is generally used as the metal material of the metal foil, and there is a problem that the cost is increased by using the copper foil.

WO2006 / 106982

In order to reduce the cost of the transparent antenna, it is conceivable to use an aluminum foil that is cheaper than the copper foil.
Therefore, the present inventors have studied a transparent antenna using an aluminum foil that is cheaper than a copper foil as a metal material of the metal pattern layer, aiming at cost reduction. However, as a result of examination, it has been found that there are actually the following problems to be solved before practical use. The following problems are not noticeable when the line width and thickness of the pattern are about 100 μm or more. In order to pursue high transparency, it has been found that the line width and thickness of the pattern become particularly obvious when the pattern is refined to a dimension of about 10 to 20 μm or smaller.

(A) The activity of aluminum itself is high, and an aluminum oxide film is present on the surface, which becomes a corrosion-resistant film and inhibits chemical etching.
(B) When a portion of the oxide film in the region in contact with the etching solution is removed, etching proceeds rapidly to the portion where the removed portion has not yet been removed, making uniform and stable etching difficult. It is.
(C) As a result of the above (a) and (b), the contour of the line portion of the metal pattern layer has a zigzag shape. In this way, the aluminum foil is inferior to the copper foil in terms of line pattern accuracy.

  As a result, the aluminum foil cannot obtain a fine pattern (for example, a line width of about 10 to 20 μm and a pattern thickness of about 10 to 20 μm) without the problem of knurls and disconnection as compared with the copper foil. And the jaggedness which generate | occur | produces in the outline of the line part of an aluminum pattern layer becomes the nonuniformity of the area ratio of the opening part which implement | achieves light transmittance, and a disconnection leads to the fall of electroconductivity (increase in surface resistance value).

  Here, with reference to FIG. 8 and FIG. 9, unstable etching when an aluminum foil is formed into an aluminum pattern layer by chemical etching and a pattern accuracy defect caused thereby will be described.

FIG. 8A shows a state before corrosion due to etching proceeds, and FIG. 8B shows a state where corrosion due to etching is in progress. FIGS. 8A and 8B show a state in which the aluminum foil 74 exposed in the region where the resist pattern 72 is not formed is etched with the etching solution 71.
8 (a) and 8 (b), the aluminum foil laminate 75 is formed of aluminum oxide on the upper surface and lower surface of the aluminum layer 73, that is, both the front and back surfaces, with the transparent adhesive layer 4 on the upper surface of the substrate 1. An aluminum foil 74 having a coating 3 is provided.

  Then, as shown in FIG. 8B, when the etching proceeds, the oxide film 3 on the exposed portion of the aluminum foil 74 that contacts the etching solution 71 in the non-formed portion of the resist pattern 72 is uniform over the entire exposed portion. Etching does not proceed, etching is partially preceded, and the aluminum layer 73 is etched from the corrosion preceding portion 76.

  As a result, when the etching is completed, pattern accuracy defects such as burrs and disconnections frequently occur in the lines of the aluminum pattern layer 2 as conceptually shown in the plan view of FIG.

  The present invention has been made in view of the above problems, and eliminates the pattern accuracy defect of an aluminum pattern layer formed by chemical etching, which occurs when the material of the metal pattern layer is changed from copper to inexpensive aluminum. An object of the present invention is to provide an antenna using a transparent antenna that is inexpensive and can be used as a component.

As a result of intensive studies, the inventors have determined that the aluminum oxide film thickness on the surface opposite to the substrate side of the aluminum pattern layer formed on one surface of the substrate is within a specific range. The present inventors have found that the above problems can be solved and have completed the present invention.
That is, the antenna according to the present invention has a transparent antenna layer laminated on one surface of a substrate, and the transparent antenna layer has an aluminum pattern layer having a thickness of 1 to 100 μm and at least the base of the aluminum pattern layer. It is characterized by comprising an aluminum oxide film having a thickness of 2 mm or more and 13 mm or less formed on the surface opposite to the material side.

According to the present invention, by regulating the aluminum oxide film on at least the surface opposite to the substrate side to a specific thickness (thinness), stable etching can be performed when forming the aluminum pattern layer by chemical etching. Etching quality is improved. For this reason, defects such as nicks and breaks in the line contour of the aluminum pattern layer are eliminated, and the pattern accuracy is improved. Consequently, it is possible to suppress variations in conductivity (surface resistance value) and haze (cloudiness value). it can. As a result, an antenna including a transparent antenna that is inexpensive in terms of material can be put into practical use by using aluminum that is less expensive than copper.
Also, in terms of manufacturing, the aluminum oxide film can be chemically etched as it is, so that the removal process is unnecessary, and the manufacturing process is complicated and the cost is high.

In the antenna according to the present invention, the substrate is preferably a transparent substrate from the viewpoint of visibility. If it comprises in this form, all the layers including a base material will function as a transparent antenna.
Further, the antenna according to the present invention is at least selected from a car navigation antenna configured as a transparent transparent antenna through all layers on a windshield or rear glass of an automobile and a security system antenna configured as a transparent antenna on a window glass of a building. As one, it can be suitably used.

According to the antenna of the present invention, the aluminum oxide film on the surface opposite to the substrate side is regulated to a specific thickness (thinness), so that the aluminum pattern layer is stable when formed by chemical etching. Etching becomes possible and etching quality is improved. For this reason, defects such as nicks and breaks in the line contour of the aluminum pattern layer are eliminated, and the pattern accuracy is improved. Consequently, it is possible to suppress variations in conductivity (surface resistance value) and haze (cloudiness value). it can. As a result, a transparent antenna that is inexpensive in terms of material can be put into practical use by using aluminum that is less expensive than copper.
Also, in terms of manufacturing, the aluminum oxide film can be chemically etched as it is, so that the removal process is unnecessary, and the manufacturing process is complicated and the cost is high.

It is sectional drawing which shows one form of the antenna by this invention. It is a circuit diagram (conceptual diagram) showing the structure of a dipole antenna. FIGS. 3A to 3D are explanatory views showing an embodiment using an antenna according to the present invention. It is explanatory drawing showing one Embodiment of the antenna by this invention. It is an enlarged view of the antenna shown in FIG. FIG. 6 is an enlarged view of an A-A ′ cross section in FIG. 5. In the antenna of this invention, it is explanatory drawing showing the usage condition of a film-form antenna. It is sectional drawing explaining the cause which a pattern precision defect produces at the time of etching an aluminum pattern layer. It is a top view explaining notionally the pattern accuracy defect of an aluminum pattern layer.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view illustrating a basic form of an antenna including a transparent antenna layer according to the present invention as a constituent element. In the cross-sectional view shown in FIG. 1, for ease of explanation, the scale in the thickness direction (vertical direction in the figure) is greatly enlarged and exaggerated than the scale in the plane direction (left and right direction in the figure), and the substrate Compared to 1, the thickness of the aluminum pattern layer 2 and the aluminum oxide film 3 is greatly enlarged and exaggerated. An antenna 10 shown in FIG. 1 is an embodiment of the antenna according to the present invention, and an aluminum pattern layer 2 is provided on one surface of a substrate 1 via a transparent adhesive layer 4. An aluminum oxide film 3 is formed on the surface of the aluminum pattern layer 2 on the substrate side (hereinafter also referred to as the lower surface) and on the surface opposite to the substrate side (hereinafter also referred to as the upper surface). The thickness of the oxide film on at least the surface (upper surface) opposite to the substrate side is 13 mm or less.
The transparent adhesive layer 4 is formed on the entire surface of the substrate 1 including the opening of the aluminum pattern layer.

The antenna of the present invention is not particularly limited, but a typical example is a half-wave dipole antenna. FIG. 2 shows a conceptual diagram of the antenna of the present invention when used as a transmitting antenna. In FIG. 2, a half-wave dipole antenna 20 includes a pair of conductive portions (antennas) 21 and a power supply portion 22 connected to the conductive portions 21 via a power supply line 23 (a signal to be transmitted is supplied as an alternating current (voltage)). And an oscillation circuit, a modulation circuit, an amplification circuit, etc.).
When the antenna of the present invention is used as a receiving antenna, a receiving circuit (consisting of a tuning circuit, an amplifier circuit, a frequency conversion circuit, a demodulation (detection) circuit, etc.) is connected instead of the power feeding unit 22 in FIG.
Further, in the half-wave dipole antenna 20, when the frequency is 2.45 GHz, the wavelength is about 122.4 mm. Accordingly, since the length (L1 + L2) of the conductive portion is ½ times the wavelength, it is about 61.2 mm, and the length of one conductive portion 21 is about 30.6 mm.
In addition, although the dimension of the width W of the electroconductive part 21 is not specifically limited, For example, it is about 5-50 mm.
The present invention is described in detail below.

[Base material]
The substrate 1 is not particularly limited, and known materials and thicknesses can be appropriately selected and used in consideration of required physical properties such as heat resistance and mechanical strength. For example, when an aluminum pattern layer is directly formed on a substrate on which the antenna of the present invention is provided, the substrate is not particularly limited as long as it can withstand an etching solution used in chemical etching described later, and is transparent. But it may be opaque.
For example, when it is necessary to conceal the appearance, color tone, or design of the object on which the antenna of the present invention is provided by the antenna of the present invention, the substrate 1 is selected to be opaque. In this case, if a desired appearance, color tone, or design (pattern, pattern, character, etc.) is given to the outer surface of the base material, the appearance and color tone on the base material 1 through the transparent antenna layer 10. Since the design can be visually recognized, the appearance, color tone, and design can be imparted to the object by attaching the antenna of the present invention.
In particular, when the antenna of the present invention is used by being attached to a display unit (window) of a mobile phone, a window of a vehicle such as an automobile, or a window of a building, a display image or a scene on the other side of the window is displayed. It must be visible. In this case, a transparent substrate having high transparency (light transmittance) in the visible region is selected as the substrate. Further, when configured as described above, all the layers (transparent substrate 1 / transparent antenna layer 10) of the antenna 100 of the present invention function as a transparent antenna.

  The transparent substrate may be appropriately selected from known materials and thicknesses, and may be a transparent inorganic plate such as glass or ceramics, or a rigid plate-like material such as a resin plate. However, a flexible resin film (or sheet) is preferable in consideration of suitability for continuous processing with a roll-to-roll having excellent productivity. The roll-to-roll refers to a processing method in which the material is unwound from a take-up (roll), supplied, appropriately processed, and then taken up and stored.

  Examples of the resin used as the material for the resin film and resin plate include polyester resins such as polyethylene terephthalate and polyethylene naphthalate, acrylic resins such as polymethyl methacrylate, polyolefin resins such as cycloolefin polymers, and triacetyl cellulose. Cellulose resins such as, polycarbonate resins, polyimide resins and the like. Among these, polyethylene terephthalate is preferably a biaxially stretched film in terms of heat resistance, mechanical strength, light transmittance, cost, and the like.

  The thickness of the substrate is basically not particularly limited and can be appropriately selected depending on the application. When utilizing a flexible resin film, it is 12-500 micrometers, for example, Preferably it is about 25-200 micrometers. Moreover, when utilizing the board | plate of resin or a transparent inorganic substance, it is about 500-5000 micrometers, for example.

It should be noted that known additives such as ultraviolet absorbers, colorants, fillers, plasticizers, antistatic agents and the like can be appropriately added to the resin used as the material of the base material as necessary.
In addition, the surface of the substrate may be appropriately subjected to known easy adhesion treatment such as corona discharge treatment, primer treatment, and ground treatment on the surface thereof.

[Aluminum pattern layer]
The aluminum pattern layer 2 is a main part of the transparent antenna layer 2 and is a part that develops a function as an antenna. A pattern layer made of aluminum on a base material. The layer itself is opaque, but it is highly conductive (reduced surface resistance) and transparent by forming a pattern in which non-formation parts of the layer such as openings are provided. It is a layer that balances the properties. Moreover, the aluminum pattern layer 2 of the present invention has an aluminum oxide film 3 having a specific thickness, that is, 13 mm or less on at least the surface (upper surface) opposite to the substrate side. The aluminum pattern layer 2 having the aluminum oxide film 3 on at least the upper surface has transparency and constitutes a transparent antenna layer 10. Here, if the substrate 1 is selected to be transparent, the antenna 100 of the present invention becomes a transparent antenna having transparency through all layers.

  The aluminum of the aluminum pattern layer is mainly composed of aluminum, and may be an aluminum alloy in addition to pure aluminum metal. These are collectively referred to as aluminum in the present invention. If the purity of the aluminum is low, the conductivity is lowered (the surface resistance value is increased). Therefore, the purity is preferably high, and the purity of the aluminum is preferably 99.0% or more. Such an aluminum pattern layer using aluminum having a purity of 99.0% or more is a foil conforming to the aluminum foil defined by JIS H4160 (aluminum and aluminum alloy foil) and JIS H4170 (high purity aluminum foil). It can be formed by using

  The aluminum pattern layer is not formed from an aluminum foil, but may be formed by forming aluminum on a base material from an aluminum vapor deposition film formed by vapor deposition, for example, vacuum vapor deposition.

  The thickness of the aluminum pattern layer may be appropriately selected from the viewpoints of high conductivity (reduction in surface resistance value), workability, mechanical strength, and the like. Specifically, it is 1 to 100 μm, preferably 5 to 20 μm, more preferably. Is 8-15 μm. If the thickness is small, the conductivity, mechanical strength, and the like are lowered. If the thickness is thick, the workability is lowered.

  The pattern shape of the aluminum pattern layer in plan view is, for example, high conductivity (reduction of surface resistance value) such as mesh (lattice or mesh) shape, stripe (stripe or parallel line group) shape, spiral (spiral or spiral) shape, etc. ) And light transmittance. Among them, a mesh shape and a square lattice shape are typical, and in addition, examples of the lattice shape include a rectangular lattice, a rhombus lattice, a hexagonal lattice, and a triangular lattice. The mesh has a plurality of openings having these shapes, and the openings are line portions (line portions or line portions) that define the openings. The line portions are usually line-shaped with a uniform width, and usually the openings and the spaces between the openings are all the same shape and the same size.

  The line width of the line portion of the pattern is 5 to 50 μm, for example, and 5 to 30 μm, which is finer in terms of the effect of the present invention.

(Pattern formation)
In order to form the pattern of the aluminum pattern layer, it can be formed by chemical etching after laminating an aluminum layer such as an aluminum foil before pattern formation on one surface of the substrate. For pattern formation of the resist pattern during chemical etching, a known pattern formation method such as a photolithography method (pattern exposure method) or a printing method may be appropriately selected. Among these, the photolithography method is a preferable method compared to the printing method in that a highly accurate pattern such as a line width required for the transparent antenna and its uniformity can be stably formed.

As an etching solution for chemically etching the aluminum pattern layer, a known etching solution may be appropriately selected and used. For example, an acidic etching solution containing ferric chloride.
Etching is performed including the aluminum oxide film in the resist pattern non-formation part on the upper surface of the aluminum layer. It is not particularly necessary to remove the aluminum oxide film on the upper surface as a pretreatment for etching. Then, the aluminum oxide film 3 on the upper surface and the lower surface corresponding to the resist pattern forming portion remains as the oxide film 3 on the upper surface and the lower surface of the aluminum pattern layer 2.

[Aluminum oxide film]
An aluminum oxide film is a layer containing an oxide of aluminum (usually considered as Al ₂ O ₃ ). When an aluminum pattern layer is formed using an aluminum foil, the aluminum oxide film is the upper surface of the foil. In the present invention, when a pattern is formed by chemical etching, the thickness of the etched side, that is, the upper surface side is defined. The upper limit of the thickness of the aluminum oxide film on at least the upper surface of the aluminum pattern layer is 13 mm, preferably 12 mm, more preferably 10 mm, and still more preferably 8 mm.
By setting the upper limit of the thickness of the aluminum oxide film on the upper surface as described above, even if the oxide film is still present, stable chemical etching is possible, and copper has been changed to inexpensive aluminum. The pattern accuracy defect can be avoided.

  By the way, the aluminum foil manufactured normally is manufactured by the rolling method. By manufacturing and storing at a normal temperature (20 ° C., around 50% RH) such as an aluminum lump rolling process, a foil manufacturing process through an annealing process, and subsequent storage in the air, the surface of active aluminum is irreversibly An oxide film is formed. The oxide film is not a thin film as in the present invention, but a film having a thickness of 15 mm or more, usually about 20 to 100 mm.

Further, the lower limit of the thickness of the aluminum oxide film on the upper surface of the aluminum pattern layer is 0 (zero), that is, the oxide film does not have to exist from the viewpoint of not inhibiting chemical etching.
However, the aluminum oxide film is said to be a passive film, and during the process of processing, transporting and storing the aluminum foil, oxidation or corrosion progresses (inadvertently or undesirably) inside the aluminum foil. It has a function to prevent this. Therefore, in this respect, it is better to form an oxide film as a dense aluminum passivating film with a thickness of at least about 2 to 3 mm on the upper surface of the aluminum pattern layer.

  The aluminum pattern layer having no aluminum oxide film on the upper surface is formed in a vacuum or in an inert gas by forming the aluminum layer before pattern formation on the substrate, and before forming the oxide film, This is possible if the upper surface is coated with a resin to prevent oxidation. Then, if a predetermined pattern is formed by chemical etching, an aluminum pattern layer having no aluminum oxide film on the upper surface is obtained.

  There are various methods for reducing the thickness of the aluminum oxide film as described above, but when an aluminum foil is used, the aluminum foil is made by a rolling method and then manufactured by annealing. Therefore, it can adjust to the target thickness by adjusting rolling conditions and annealing conditions.

  For example, when removing the rolling oil adhering to the surface of the aluminum foil after rolling during annealing, the gas composition of the annealing atmosphere is controlled so that the surface is not oxidized (the oxygen concentration is lowered), aluminum There are methods such as removing the aluminum oxide film on the foil surface with chemicals. Although there is a method of not annealing, it is not preferable to omit the annealing step because the rolling oil adversely affects the photolithography method.

  The thickness of the aluminum oxide film is measured by X-ray photoelectron spectroscopy (XPS) which is a kind of Hunter Hall method or X-ray fluorescence analysis.

  The aluminum oxide film is usually formed on both the front and back surfaces of the foil, that is, both the upper surface and the lower surface, from the foil manufacturing process. Among these, since it is the oxide film on the upper surface that affects the chemical etching for pattern formation of the aluminum pattern layer, the present invention defines at least a specific thickness (thinness) for the aluminum oxide film on the upper surface. . It should be noted that the aluminum oxide film on the lower surface usually needs to be specified in terms of pattern accuracy because the contribution to the generation of burrs in the mesh shape during chemical etching is negligible compared to the aluminum oxide film on the upper surface. There is no. However, if the film thickness is too thick, an adverse effect on the mesh shape due to the aluminum oxide film remaining in the opening may occur, and the transparency of the opening may be reduced. For this reason, it is recommended that the aluminum oxide film on the lower surface is preferably less than the minimum visible light wavelength of 380 nm (3800 mm), more preferably 200 nm (2000 mm) or less. For example, the film thickness of the aluminum oxide film on the lower surface is set to 13 mm or less similarly to the upper surface. As one form of the present invention, by adjusting the film thickness of the aluminum oxide film on the lower surface before chemical etching and the processing conditions of chemical etching, the minimum wavelength of visible light is less than 380 nm (for example, 3 to 3). A transparent aluminum oxide film having a thickness of 13 Å) can be left to protect the transparent adhesive layer or the substrate exposed to the opening during chemical etching from coloring by the corrosive liquid.

(Blackening treatment layer)
In addition, you may form a blackening process layer in the surface of an aluminum pattern layer.
The blackening treatment layer is a layer for improving external light absorption and contrast by suppressing light reflection by the aluminum pattern layer and the oxide film on the surface thereof. The blackening treatment layer is provided when external light absorption and contrast improvement are required. The blackening treatment layer is provided on the surface of the aluminum pattern layer, and when there is an oxide film on the surface, it is provided on the surface of the oxide film to reduce the light reflectance.

  Here, the surface means a surface such as an upper surface, a lower surface, or a side surface. The surface on which the blackening treatment is performed to form the blackening treatment layer is a surface according to requirements, such as only the upper surface of the aluminum pattern layer, the upper surface and both side surfaces, only the lower surface, and all surfaces of the upper surface, both side surfaces, and the lower surface. What is necessary is the same as the known blackening process. Among these, the surface in contact with the transparent adhesive in the presence of the transparent adhesive layer is the lower surface. Further, when the transparent antenna of the present invention is used with the upper surface side directed toward the viewer, it is preferable to form a blackening treatment layer at least on the upper surface.

  As the blackening treatment layer, a known layer may be appropriately employed. For example, as the blackening treatment layer, an inorganic material such as a metal, an organic material such as a black resin, or the like can be used. The inorganic material is, for example, a metal compound such as a metal or an alloy, a metal oxide, or a metal sulfide, and can be formed by a known blackening process such as a plating method. Moreover, as black resin, it can form as a layer which contained the black coloring agent in resin, for example.

[Transparent adhesive layer]
The transparent adhesive layer 4 is a layer for fixing the aluminum pattern layer to the substrate. For example, when the aluminum pattern layer is formed from an aluminum foil, the transparent adhesive layer 4 is used for bonding and fixing the aluminum foil to the substrate. . In addition, a transparent adhesive bond layer can be abbreviate | omitted when forming from the aluminum layer which laminated | stacked the aluminum pattern layer directly on the base material by aluminum vapor deposition.

  As the transparent adhesive layer, a transparent adhesive may be used as long as it does not impair the light transmission through the opening of the aluminum pattern layer, and a known transparent adhesive may be used as appropriate. For example, urethane adhesive, acrylic adhesive, epoxy adhesive, rubber adhesive, and the like. Among these, urethane adhesives, for example, two-component curable urethane adhesives are preferable in terms of adhesive strength. As the two-component curable urethane-based adhesive, an adhesive using a polyol as a main component and a polyisocyanate curing agent can be used. Examples of the polyol include acrylic polyol, polyester polyol, polyurethane polyol, polyether polyol, and polyester polyurethane polyol. Examples of polyisocyanate curing agents include tolylene diisocyanate curing agents, xylylene diisocyanate curing agents, hexamethylene diisocyanate curing agents, and the like. A plurality of polyols and polyisocyanate curing agents may be used.

  A transparent adhesive layer can be formed by laminating an aluminum foil and a base material via an adhesive after applying a transparent adhesive to an aluminum foil, a base material, or both by a known forming method. . The forming method includes a coating method and a printing method.

[Other layers]
In the antenna of the present invention, other layers, for example, known layers such as a surface protective layer for flattening the unevenness on the upper surface side of the aluminum pattern layer and protecting the surface can be laminated.
The surface protective layer can be formed by applying a liquid composition containing a resin to the concavo-convex surface of the aluminum pattern layer formed on one surface of the substrate. The liquid composition is not particularly limited as long as it contains a transparent resin, and a known resin may be appropriately employed. For example, a thermoplastic resin, a thermosetting resin, an ionizing radiation curable resin, or the like. For example, thermoplastic resins are acrylic resins, polyester resins, thermoplastic urethane resins, vinyl acetate resins, etc., and thermosetting resins are urethane resins, epoxy resins, curable acrylic resins, etc. Examples of the radiation curable resin include acrylate resins that are cured by ultraviolet rays or electron beams. Among these, an ionizing radiation curable resin that can be coated and formed in a solvent-free or solvent-free state is a preferable resin in that it easily fills the unevenness of the aluminum pattern layer.

The surface resistance value of the aluminum pattern layer of the antenna according to the present invention can be 0.005 to 10Ω / □, more preferably 0.05 to 5Ω / □, and the antenna has sufficient conductivity and high sensitivity. It can be.
The surface resistance value can be measured by a 4-terminal 4-probe method using a resistivity meter / Loresta EPMCP-T360 type (manufactured by Mitsubishi Chemical Analytech).
Moreover, the visible light transmittance of the transparent antenna layer 10 portion of the antenna according to the present invention can be set to 70% or more, and has sufficient transparency. Therefore, even if the antenna is attached to an object, it is not noticeable, and the appearance and design of the object are not impaired. Furthermore, the substrate 1 of the antenna 100 according to the present invention can be selected to be transparent (visible light transmittance of 70% or more), and a so-called transparent antenna that is transparent through all layers can be configured. In this case, the visible light transmittance through all layers of the antenna 100 is preferably 70% or more, and more preferably 80% or more.
The visible light transmittance can be measured with an ultraviolet-visible near-infrared spectrophotometer MPC-3100 (manufactured by Shimadzu Corporation).

[Usage]
Applications of the antenna according to the present invention include, for example, (1) mobile phone antenna: antenna 100 is attached to a part of housing 31 of mobile phone 30 (see FIG. 3A), and telephone / Internet communication function (2) Car navigation antenna: It is configured as a transparent antenna that is transparent through all layers on the windshield or rear glass of automobiles. (2) Car navigation antenna: Receives radio waves such as TV and radio broadcasts and GPS (global positioning system). An antenna 100 (hereinafter simply referred to as “transparent antenna 100”) is attached (see FIG. 3B), and the transparent antenna is connected to the TV tuner of the car navigation device 42 to receive radio waves from GPS satellites. (3) Antenna for security system: Transparent to window glass 51 of building 50 An antenna 100 configured as an antenna is attached (see FIG. 3C), and when the window glass is broken, a signal is transmitted from the transparent antenna to the receiving device, thereby detecting an abnormality, and (4 ) Product management antenna: In an RFID (radio frequency identification) tag 60 including the IC chip 61 and the antenna 100 (see FIG. 3D), when the antenna receives a calling radio wave from the reader / writer, it is stored in the memory of the IC chip. For example, the transparent antenna transmits information to the reader / writer so that product entry / exit, inventory, sales management, and the like are performed.
Hereinafter, an example in which the transparent antenna according to the present invention is used as an antenna for a mobile phone will be described in detail.

FIG. 4 is a schematic diagram showing a state in which the transparent antenna 100 of the present invention is attached to the display screen 32 of the mobile phone 30. 5 is an enlarged view of the transparent antenna shown in FIG. 4, and FIG. 6 is an enlarged view of the AA ′ cross section in FIG.
The cellular phone 30 is of a two-fold type, and includes a display screen (subwindow) 32 on the outer surface in a folded state. The transparent antenna 10 is attached to the entire display range of the display screen 32.
In addition, a feeding electrode (not shown) of the transparent antenna 100 is connected to a transmission / reception unit in the mobile phone 30 through an input / output terminal provided on the outer frame of the display screen 32.

As shown in FIG. 6, an aluminum pattern layer 34 having an oxide film 3 on the upper surface is provided on one surface of a base material 33, and a surface protective layer 35 is provided on the surface of the aluminum pattern layer 34. 34 is formed so as to flatten the unevenness.
A part of the surface protective layer 35 is provided with a through hole part 36, and the electrode part 37 is exposed through the through hole part 36. An input / output terminal provided on the outer frame of the display screen 32 and an antenna wire are connected to the exposed electrode portion 37.
Further, an adhesive-type transparent adhesive layer 38 is provided on the surface of the substrate 33 opposite to the aluminum pattern layer 34, and a release sheet 39 is bonded to the surface of the transparent adhesive layer 38. .
When the transparent antenna 100 is attached to the display screen 32 of the mobile phone 30 as a retrofit, the release sheet 39 is peeled off to expose the transparent adhesive layer 38, and the transparent antenna 100 is displayed through the transparent adhesive layer 38. Affix to the front of the screen 32.

In addition, the transparent antenna 100 has a desired length L, and transmits / receives a desired radio wave even if it is bent halfway if there is no pattern accuracy defect such as disconnection in the line part outline of the aluminum pattern layer of the transparent antenna. Can do.
Accordingly, when the width of the display screen 32 is shorter than the length of the transparent antenna 100, as shown in FIG. 7, the transparent antenna 100 is folded in a zigzag manner to reduce the installation area and fit within the display screen. Then, it may be attached to the display screen 32.
In FIG. 7, the length of the transparent antenna 100 is a length measured along the spelling pattern from one end a to the other end b of the transparent antenna 100.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has any configuration that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits the same effects. Are included in the technical scope.

  Hereinafter, the present invention will be described more specifically with reference to examples. These descriptions do not limit the present invention.

Example 1
First, a continuous strip-shaped rolled aluminum foil having a thickness of 12 μm was prepared as a metal foil for the aluminum pattern layer 2. The thickness of the aluminum oxide film on the surface of the aluminum foil was measured by fluorescent X-ray analysis (XPS).
Further, as a base material (transparent base material) 1, a continuous belt-like uncolored transparent biaxially stretched polyethylene terephthalate film having a polyester resin primer layer formed on one side was prepared.

  Next, the primer layer surface of the transparent substrate and the glossy surface of the aluminum foil are cured with respect to 12 parts by mass of a transparent two-component curable urethane resin-based adhesive (polyester polyurethane polyol having an average molecular weight of 30,000 as a main component). (Including 1 part by mass of xylylene diisocyanate-based prepolymer as an agent) and then cured at 50 ° C. for 3 days to form a continuous belt-like layer having a transparent adhesive layer 4 having a thickness of 7 μm between the aluminum foil and the transparent substrate. An aluminum foil laminated sheet was obtained.

  Next, the aluminum foil of the aluminum foil laminated sheet was subjected to a chemical etching process using a photolithography method to form a mesh-shaped aluminum pattern layer 2 composed of openings and line portions.

  Specifically, the etching is performed by applying a photosensitive etching resist on the entire surface of the aluminum foil of the laminated sheet, then exposing and exposing a desired mesh pattern, developing, hardening, baking, and opening the mesh. After forming a resist pattern in which the resist layer is not formed on the region corresponding to, the aluminum foil of the resist layer non-formed portion is removed by etching with an acid aqueous etchant containing ferric chloride, An aluminum pattern layer having a mesh-shaped opening was formed, and then water washing, resist stripping, washing, and drying were sequentially performed.

  As for the shape of the mesh, the line width of the linear line portion having a square opening and a non-opening portion was 20 μm, the line interval (pitch) was 300 μm, and the height of the line portion was 12 μm. Further, the obtained cross-sectional form was as shown in FIG. In this way, a transparent antenna sheet having a width dimension of 605 mm was obtained and wound into a roll.

  As for the pattern accuracy of the obtained aluminum pattern layer, the variation in the line width of the mesh (evaluated by 3 × (standard deviation of width distribution)) is 4.5 μm, and the surface unevenness (appearance on unevenness) by visual observation is There was no problem in appearance, and there was no disconnection of the mesh constituent lines.

Next, a 2.45 GHz band half-wave dipole antenna having a pair of transparent antennas as shown in FIG. 2 having a length of 30 mm and a width of 40 mm was prepared using the transparent antenna sheet.
As a result of measuring the antenna characteristics of the antenna, antenna characteristics equivalent to the standard dipole antenna were obtained. The surface resistance of the antenna was 0.5Ω / □, and the (visible light) transmittance was 77%.

(Comparative Example 1)
A transparent antenna sheet was obtained in the same manner as in Example 1 except that the thickness of the aluminum oxide film on the surface of the aluminum foil was 15 mm.
With respect to the pattern accuracy of the obtained aluminum pattern layer, the mesh line was frequently disconnected (line width variation 22 μm), the surface unevenness was conspicuous visually, and the surface resistance value varied greatly.
Next, a 2.45 GHz half-wave dipole antenna having a pair of transparent antennas having a length of 30 mm and a width of 40 mm was prepared using the transparent antenna sheet.
As a result of measuring the antenna characteristics of the antenna, it was inferior to the antenna characteristics of the standard dipole antenna.

DESCRIPTION OF SYMBOLS 1 Base material 2 Aluminum pattern layer 3 Aluminum oxide film (oxide film)
4 Transparent adhesive layer 10 Transparent antenna layer 20 Half-wave dipole antenna 21 Conductive part (transparent antenna)
22 Power Supply Unit 23 Power Supply Line 30 Mobile Phone 31 Housing 32 Display Screen (Sub Window)
33 Substrate 34 Aluminum pattern layer 35 Surface protective layer 36 Through-hole portion 37 Electrode portion 38 Transparent adhesive layer 39 Release sheet 41 Front glass 42 Car navigation device 50 Building 51 Window glass 60 RFID tag 61 IC chip 62 IC chip label 71 Etching solution 72 Resist pattern 73 Aluminum layer 74 Aluminum foil 75 Aluminum foil laminate 76 Corrosion preceding part 100 Antenna (transparent antenna)
L1, L2 Length of conductive part W Width of conductive part a One end of antenna b Other end of antenna

Claims (3)

A transparent antenna layer is laminated on one surface of a base material, and the transparent antenna layer has an aluminum pattern layer having a thickness of 1 to 100 μm and at least a surface of the aluminum pattern layer opposite to the base material side. An antenna comprising an aluminum oxide film having a thickness of 2 mm or more and 13 mm or less.   The antenna according to claim 1, wherein the substrate is a transparent substrate.   The car navigation antenna configured as a transparent antenna that is transparent through all layers on the windshield or rear glass of an automobile and the security system antenna configured as a transparent antenna on a window glass of a building are at least one selected from claim 1 or 2. The antenna according to 2.

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