Manufacturing method of transparence antenna

Abstract

To obtain a high transparence performance and a high antenna radiation efficiency even in the case where an antenna conductor and a ground conductor are formed by a conductive material of a mesh pattern.SOLUTION: Viscoelasticity of a conductive paste is adjusted to 500 to 2000 Pa s when a shear rate is 0.1 s-1, and to 1 to 20 Pa s when the shear rate is 250 s-1. The conductive paste after the adjustment is developed onto a screen plate, and thereafter the conductive paste is printed in a screen to a transparence base material. By heating the conductive paste of a mesh pattern printed to the transparence base material, a conductive mesh layer in which the conductive paste is sintered to the transparence base material is formed. In the conductive mesh layer to be sintered, a line width of the conductive mesh layer is 50 to 200 μm, an arrangement pitch of an open of the conductive mesh layer is 900 to 1100 μm, and a visible light transmittance of the conductive mesh layer exceeds 50%, and a sheet resistance of the conductive mesh layer is 10×10-2 Ω / sq or less.SELECTED DRAWING: Figure 7

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a transparent antenna.

Background Art

[0002] In recent years, various communication systems using wireless technologies such as mobile phones, Internet communication, radio broadcasting, and GPS (Global Positioning System) have been developed. To support these communication systems, an antenna capable of transmitting and receiving electromagnetic waves used in each communication system is required. In addition, in order to achieve higher speed and larger capacity of wireless communication, the frequency band used is becoming higher, such as the frequency band for the fifth-generation mobile communication system (5G). Therefore, the antenna needs to have the ability to stably transmit and receive radio waves even when such high-frequency radio waves are used for mobile phones, Internet communication, etc.

[0003] For example, the display display unit of a mobile communication terminal such as a smartphone or a tablet terminal, the window of a house, etc. are good radio wave passing parts, so it is desirable to install a transparent antenna that is difficult to visually recognize at the passing part. However, when a transparent conductive material such as ITO (Indium Tin Oxide) is used as the antenna material, the transparent conductive material has disadvantages of high electrical resistance and transmission loss, and low antenna radiation efficiency. Therefore, it has been proposed to form an antenna by a mesh pattern having a large number of openings made of thin wires of a conductive material, and the technique is disclosed in Patent Document 1. According to this antenna, the transparency of the antenna is maintained by the openings of the mesh pattern.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, when using the antenna with the above-described mesh pattern, the larger the area of the opening of the mesh pattern is to increase the light transmittance and make the antenna less visible, the more the antenna radiation efficiency deteriorates. Thus, improving the antenna radiation efficiency and improving the transparency of the antenna are in a trade-off relationship, which makes antenna design difficult.

[0006] Also, screen printing is suitable for efficiently forming the antenna with the mesh pattern in the required area and thickness. However, in screen printing using a conductive material, printing defects such as the thickness of thin lines, disconnection, and bleeding are likely to occur when forming the mesh pattern, and it is difficult to accurately and stably form a desired mesh pattern.

[0007] Therefore, an object of the present invention is to provide a method for manufacturing an antenna that hardly causes printing defects when forming an antenna that can obtain high transparency of the antenna and high antenna radiation efficiency by screen-printing a mesh pattern composed of thin lines of a conductive material.

Means for Solving the Problems

[0008] The present invention has the following configuration. A method for manufacturing a transparent antenna in which a mesh pattern antenna is formed on a transparent substrate, (1) Prepare the transparent substrate and a conductive paste as a printing material for the antenna, and adjust the viscoelasticity of the conductive paste so that it is 500 to 2000 Pa·s at a shear rate of 0.1 s -1 and 1 to 20 Pa·s at a shear rate of 250 s -1 (2) After spreading the conductive paste on a screen plate having holes corresponding to the mesh pattern of the antenna, screen-print the conductive paste filled in the holes onto the transparent substrate while pressing the screen plate against the transparent substrate, and (3) After the screen printing, heat the transparent substrate at a temperature of 100 to 250 °C for 1 to 30 minutes to cure the conductive paste. (3) In the above (2), heating the conductive paste of the mesh pattern printed on the transparent substrate to form a conductive mesh layer in which the conductive paste is fired on the transparent substrate, which are sequentially included, In the above (3), the fired conductive mesh layer has a line width of 50 to 200 μm, an array pitch of openings of the conductive mesh layer of 900 to 1100 μm, a visible light transmittance of the conductive mesh layer exceeding 50%, and a sheet resistance of the conductive mesh layer of 10×10 -2 Ω / sq or less. Method for manufacturing a transparent antenna.

Effect of the Invention

[0009] According to the present invention, when forming an antenna that can obtain high transparency of the antenna and high antenna radiation efficiency by screen-printing a mesh pattern composed of thin lines of a conductive material, it is possible to make it difficult to cause printing defects.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

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Figure 9

DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The transparent antenna of the embodiment described in this specification is used for the propagation of signals in a high-frequency band (for example, 0.3 GHz to 300 GHz) such as microwaves and millimeter waves. Such a high-frequency band includes the UHF band of 0.3 to 3 GHz, the SHF band of 3 to 30 GHz, and the EHF band of 30 to 300 GHz. Specific examples of the high-frequency devices constituting the transparent antenna in the present embodiment include planar antennas and planar waveguides (planar transmission lines).

[0012] In addition, the transparent antenna of the present embodiment may be used, for example, in wireless communication standards such as the fifth-generation mobile communication system (so-called 5G) and Bluetooth (registered trademark), and wireless LAN (Local Area Network) standards such as IEEE802.11ac. Further, when the transparent antenna of the present embodiment is used in a vehicle, it can also be used in an in-vehicle radar system that irradiates radar, vehicle-to-vehicle communication, and V2X (Vehicle to Everything) communication systems such as road-vehicle communication.

[0013] In the following description, "~" indicating a numerical range means that it includes the numerical values described on both sides. For example, when ψ is in the range of numerical value α to numerical value β, the range of ψ is a range including numerical value α and numerical value β (α ≤ ψ ≤ β). Also, "transparent" in this specification means transparent to visible light unless otherwise specified. For example, "transparent" means that the light transmittance is 92% or more in the visible light wavelength range of wavelengths 380 to 780 nm. The light transmittance is the value of the measured visible light transmittance defined in JIS R3106 (1998).

[0014] FIG. 1 is a schematic cross-sectional view of the antenna in the first embodiment. The antenna 100 includes a transparent substrate 11, an antenna conductor 13 provided on the first main surface 11a of the transparent substrate, a ground conductor 15 provided on the second main surface 11b, and an antenna terminal portion 17. Note that the antenna 100 shown here is an example, and the configuration of the antenna 100 is not limited to this. The antenna conductor 13 and the ground conductor 15 are both composed of a conductive mesh layer formed of a mesh pattern of thin wires of a conductive material. The antenna conductor 13 transmits and receives radio waves. The ground conductor 15 functions as a ground plane and controls the directivity of the antenna. The ground conductor 15 may be larger than the antenna conductor 13 and may be provided on the entire other surface of the transparent substrate 11. The antenna terminal portion 17 is electrically connected to the antenna conductor 13 and supplies power to the antenna conductor 13. In this specification, the antenna conductor 13 and the ground conductor 15 are also collectively referred to as the antenna portion 19.

[0015] The transparent substrate 11 is a plate-like or sheet-like substrate mainly composed of a dielectric. The transparent substrate 11 is, for example, glass or resin, and particularly preferably glass. Examples of the glass material include soda lime silica glass, borosilicate glass, aluminosilicate glass, or alkali-free glass. As the resin material, a transparent resin is preferable, and examples thereof include polyimide (PI), polyphenylene ether (PPE), polycarbonate (PET), acrylic resin, or fluororesin. The shape of the transparent substrate 11 can be arbitrarily designed according to the location where the antenna 100 is disposed. The thickness of the transparent substrate 11 is preferably 100 μm to 2 mm. When the transparent substrate 11 is in a sheet shape, its thickness is preferably 200 μm to 1.2 mm from the viewpoint of excellent antenna holding strength.

[0016] Examples of the conductive material for forming the antenna conductor 13 and the ground conductor 15, which are the antenna portion 19, include gold, silver, copper, platinum, aluminum, chromium, etc. The antenna portion 19 of this configuration is formed by printing a conductive paste (silver paste) containing silver particles in a solvent on the transparent substrate 11 using silver as the conductive material. Examples of the solvent include Bi 2 O 3,B 2 O 3 Those containing a binder such as etc. can be used.

[0017] Also, in this embodiment, the antenna conductor 13 is formed on the first main surface 11a of the transparent substrate 11, and the ground conductor 15 is formed on the second main surface 11b. However, at least one of the antenna conductor 13 and the ground conductor 15 may be provided inside the transparent substrate 11. Further, when the transparent substrate 11 is a laminated glass including a pair of glass plates and a resin layer provided between the pair of glass plates, at least one of the antenna conductor 13 and the ground conductor 15 may be provided between the glass plate and the resin layer constituting the laminated glass.

[0018] FIG. 2 is a schematic diagram showing an example of the mesh pattern of the conductive mesh layer in the antenna conductor 13 and the ground conductor 15. FIG. 3 is a partially enlarged view of the mesh pattern shown in FIG. 2. The conductive mesh layer is composed of a large number of thin lines 21. The mesh pattern shown here is a lattice pattern including a plurality of openings 23 formed by the thin lines 21 intersecting each other. The opening 23 is an area surrounded by the thin lines 21, and its shape is not limited to the square shown in FIGS. 2 and 3, and may be a quadrilateral such as a rectangle, trapezoid, parallelogram, rhombus, etc., a polygon such as a triangle, pentagon, hexagon, etc., or an arbitrary geometric shape such as a circle or ellipse. Also, not all of the openings 23 need to have the same shape, and a shape in which a plurality of the above-mentioned shapes are mixed, shapes with different sizes from each other, etc. may be used. Furthermore, the opening 23 may have a random shape. By making it a random shape, the generation of interference fringes (moiré fringes) can be prevented.

[0019] The line width W (FIG. 3) of the thin line 21 is 50 to 200 μm, more preferably 100 to 150 μm, and even more preferably 100 to 125 μm.

[0020] When the sum of the line width W of the fine wire 21 and the length Ws of one side of the opening 23 is defined as the array pitch Pt (= W + Ws) of the openings in the conductive mesh layer, the array pitch Pt is 900 to 1100 μm, preferably 950 to 1050 μm, more preferably 950 to 1000 μm. From the above, the length Ws of one side of the opening 23 is preferably 700 to 1000 μm.

[0021] Also, the ratio (W / Pt) of the line width W of the fine wire 21 to the above-described array pitch Pt of the openings is preferably 100 / 1100 to 200 / 900, more preferably 100 / 1050 to 150 / 950, and even more preferably 100 / 1000 to 125 / 950.

[0022] By setting the line width W, the array pitch Pt, and the parameters using these within the above ranges, the visible light transmittance of the antenna 100 in which the antenna conductor 13 and the ground conductor 15 are formed on the transparent substrate 11 becomes good, and the sense of incongruity in appearance is less likely to occur. Specifically, the visible light transmittance of the conductive mesh layer exceeds 50%. The visible light transmittance of this conductive mesh layer is more preferably 60% or more, even more preferably 70% or more, even more preferably 80% or more, and even more preferably 90% or more. The larger the visible light transmittance of the conductive mesh layer, the more the above-described visible light transmittance can be improved, and the less visible the antenna portion 19 becomes. The visible light transmittance can be measured by an ultraviolet-visible-near-infrared spectrophotometer UH4150 (manufactured by Hitachi High-Tech Corporation).

[0023] Also, the sheet resistance of the conductive mesh layer is 10×10 -2 Ω / sq or less, preferably 5×10 -2 Ω / sq or less, and even more preferably 1×10 -2 Ω / sq or less. Thereby, a decrease in the maximum gain of the antenna can be suppressed.

[0024] Here, the antenna radiation efficiency of the antenna 100 will be described. The antenna radiation efficiency of the antenna 100 deteriorates when the antenna unit 19 is meshed. Therefore, the meshing of the antenna unit 19 needs to be performed within a range that can suppress the deterioration of the antenna radiation efficiency as much as possible while maintaining the necessary visible light transmittance.

[0025] FIG. 4 is a graph showing how the frequency characteristics of the antenna radiation efficiency change depending on the conductivity of the antenna unit 19. According to FIG. 4, it is recognized that the antenna radiation efficiency deteriorates as the conductivity of the antenna unit 19 decreases. For example, when the frequency is 4 GHz, the antenna radiation efficiency deteriorates particularly significantly when the conductivity is reduced from 58.6 MS / m to 3 MS / m or less. Therefore, in order to suppress the deterioration of the antenna radiation efficiency to less than -1 dB compared to the case where the conductivity is 58.6 MS / m, it is preferable to set the conductivity of the antenna unit 19 to 3 Ms / m or more. By doing so, the transmission loss per 50 mm of the antenna can be made 1.0 dB or less.

[0026] FIG. 5 is a schematic diagram showing an example of a shape when an outer frame line 25 is provided at the outer edge of the mesh pattern. The outer frame line 25 provided at the outer edges of the antenna conductor 13 and the ground conductor 15 suppresses the deterioration of the antenna radiation efficiency. For example, according to the simulation analysis of the antenna characteristics, at a frequency of 4 GHz, when the effective conductivity of the antenna unit 19 is 3 MS / m, in order to keep the deterioration of the antenna radiation efficiency within 0.5 dB, when the outer frame line 25 is not provided, it is necessary to make the arrangement pitch Pt of the openings 23 700 μm or less. On the other hand, when the outer frame line 25 is provided, it is expected that the arrangement pitch Pt of the openings 23 will be sufficient if it is 1100 μm or less. Thus, by providing the outer frame line 25 at the outer edge of the mesh pattern, the allowable dimension of the arrangement pitch Pt of the openings 23 can be expanded, and thereby the visible light transmittance can be increased more. The line width of the outer frame line 25 is preferably 50 to 200 μm, more preferably 50 to 150 μm, and even more preferably 50 to 100 μm.

[0027] FIG. 6 is a schematic diagram showing the spiral antenna section 19. The planar shapes of the antenna conductor 13 and the ground conductor 15 shown in FIG. 1 on the transparent base material 11 may be spiral. Due to its structure, the spiral antenna has many characteristic parameters, and various radiation directivities can be realized by selecting these characteristic parameters.

[0028] Next, the manufacturing method of the above-described antenna 100 will be described. The mesh pattern of the antenna section 19 can be formed by screen printing. Generally, screen printing includes a paste spreading step of spreading a paste, which is a printing material, on a screen plate and spreading the paste on a screen plate having holes of a specific pattern, and a printing step of transferring the paste spread on the screen plate to a printing object through the holes of the screen plate. The screen printing method is a well-known technique, and here, the configuration of the screen printing apparatus and its operation, etc. will be briefly described.

[0029] FIG. 7 is a flowchart showing the procedure of the antenna manufacturing method. The manufacturing process of the antenna 100 of this configuration includes a step (S1) of preparing the transparent base material 11 and the conductive paste, a step (S2) of adjusting the viscoelasticity of the conductive paste, a step (S3) of screen-printing the conductive paste on the surface of the transparent base material 11 in a mesh pattern, and a step (S4) of baking the printed conductive paste. Further, it may include a step (S5) of performing a blackening process as necessary. Hereinafter, each step will be described in detail.

[0030] (Screen Printing and Its Preparation) First, in step S1, the transparent base material 11 and the conductive paste (silver paste) are prepared, and in step S2, the conductive paste is adjusted to a viscoelasticity (shear viscosity) suitable for the screen printing in step S3 and the baking process in step S4. Here, the shear viscosity of the conductive paste that becomes the printing material of the antenna section 19 is adjusted to 500 to 2000 Pa·s at a shear rate of 0.1 s -1 and to 1 to 20 Pa·s at a shear rate of 250 s -1 .

[0031] In the screen printing of step S3, the paste spreading step and the printing step described above are performed. In the paste spreading step, the conductive paste whose shear viscosity has been adjusted in step S2 is placed on a screen plate having holes formed corresponding to the mesh pattern of the antenna portion 19, and a scraper is moved on the screen plate to spread the conductive paste over the screen plate. In the printing step, on the screen plate on which the conductive paste has been spread, a squeegee is moved on the transparent substrate 11 while pressing the screen plate. As a result, the conductive paste filled in the holes of the screen plate is transferred to the transparent substrate 11, and the conductive paste is printed on the transparent substrate 11 in a mesh pattern.

[0032] In the above-described screen printing, the shear rate acting on the conductive paste due to the pressing operation by the squeegee reaches about 250 s -1 Even in that case, it is preferable to make the shear viscosity of the conductive paste relatively small so that the conductive paste is transferred to the transparent substrate through the holes of the screen plate and good screen printing is possible. Specifically, the shear viscosity of the conductive paste is in the range of 1 to 30 Pa·s, preferably 1 to 20 Pa·s, more preferably 1 to 15 Pa·s described above.

[0033] The shear viscosity of the above-described conductive paste (hereinafter also referred to as silver paste) can be adjusted by changing the average particle size and concentration of the silver particles contained in the silver paste. The particle size of the silver particles can be adjusted, for example, by bead mill crushing or the like. Further, the concentration of the silver particles contained in the silver paste (for example, mass percentage concentration) can be adjusted, for example, by the amount of the solvent or binder. The average particle size of the silver particles can be measured, for example, by SEM observation, and the mass percentage concentration of the silver particles can be measured, for example, by ICP analysis or the like.

[0034] The average particle size of the adjusted silver particles is preferably 0.1 to 10 μm, more preferably 0.1 to 5 μm, and even more preferably 0.1 to 1 μm. Further, the mass percentage concentration of silver particles in the adjusted silver paste is preferably 50 to 95% by mass, more preferably 60 to 90% by mass, and even more preferably 70 to 90% by mass to obtain good conductivity.

[0035] The shape of the silver particles is not particularly limited. Examples of the shape of the silver particles include flake (scaly) shape, spherical shape, dendritic (dendrite) shape, and a shape in which spherical primary particles are aggregated three-dimensionally (aggregated shape).

[0036] Typically, the silver paste can be prepared by dispersing a thermoplastic resin, silver powder, an organic solvent, and, if necessary, other components using a three-roll mill or the like. As the organic solvent, those in which the binder is soluble and which can disperse the silver powder well are preferred. Specific examples include ethyl diglycol acetate (EDGAC), butyl glycol acetate (BMGAC), butyl diglycol acetate (BDGAC), cyclohexanone, toluene, isophorone, γ-butyrolactone, benzyl alcohol, Solvesso 100, 150, 200 manufactured by Exxon Chemical, propylene glycol monomethyl ether acetate, a mixture of dimethyl esters of adipic acid, succinic acid, and glutaric acid [for example, DBE manufactured by DuPont Co., Ltd.], terpineol, and the like. The content of the organic solvent is preferably 5 parts by weight or more and 40 parts by weight or less, more preferably 10 parts by weight or more and 35 parts by weight or less, based on 100 parts by weight of the total weight of the paste. The silver paste may contain other components. Examples of the other components include a dispersant, a surface conditioner, an antifoaming agent, and a rheology control agent.

[0037] (Firing treatment) The firing process of Project 4 volatilizes the solvent contained in the silver paste and solidifies the silver particles on the transparent substrate 11. This firing process is preferably carried out in a pre-firing step (the first stage) for volatilizing the solvent and a main firing step (the second stage) for solidifying the silver particles. The firing process is not limited to the above two stages. Depending on the conditions, the pre-firing step may be omitted, or other processes may be added. Through this firing process, the silver paste of the printed mesh pattern adheres to the transparent substrate 11 while maintaining the mesh pattern, and a conductive mesh layer is formed on the transparent substrate 11.

[0038] The pre-firing temperature in the first stage is preferably 100 to 300 °C, more preferably 150 to 250 °C. The pre-firing time is preferably 5 to 30 minutes, more preferably 10 to 20 minutes. The main firing temperature in the second stage is preferably 450 to 650 °C, more preferably 500 to 600 °C. The main firing time is preferably 15 to 90 minutes, more preferably 30 to 60 minutes.

[0039] In this firing process, since the silver paste is heated in a stationary state, it is preferable to make the shear viscosity of the silver paste relatively large so that the shape of the silver paste is less likely to change. Specifically, when the shear rate generated in the silver paste is 0.1 s -1 , the shear viscosity of the silver paste is set to 500 to 3000 Pa·s, preferably 1500 to 2500 Pa·s, more preferably 1800 to 2000 Pa·s as described above.

[0040] Figure 8 is a graph showing the change in shear viscosity with respect to the shear rate of various conductive pastes. PTa to PTe shown here are commercially available conductive pastes. For all conductive pastes, the shear viscosity is low when the shear rate exceeds 3 s -1 , but when the shear rate is 3 s -1 or higher, it has the characteristic that the increase in shear viscosity becomes significant.

[0041] (Blackening treatment) When the conductive mesh layer serving as the antenna unit 19 is made of a metal such as silver, the appearance of the antenna may deteriorate due to metal reflection. To prevent this, the metal surface may be blackened so that the antenna unit 19 is concealed.

[0042] Examples of the blackening treatment include a treatment of overcoating the conductive mesh layer with a black ink such as carbon black, a treatment of immersing the silver metal surface in an aqueous solution of sodium hypochlorite or palladium chloride to oxidize it, etc. When the conductive mesh layer is immersed in sodium hypochlorite, it is immersed at room temperature for 30 to 60 minutes. When using carbon black, overcoating is performed by screen printing so as to trace the pattern formed with the conductive paste.

[0043] As described above, the conductive mesh layer formed after firing has a line width of 100 to 150 μm, and the array pitch of the openings of the conductive mesh layer is 950 to 1000 μm. By doing so, the visible light transmittance of the conductive mesh layer exceeds 50%. The visible light transmittance of the conductive mesh layer is also preferably such that the reflectance of the conductive mesh layer after the blackening treatment with respect to visible light is 1 to 10%, more preferably 1 to 5%. The reflectance with respect to visible light can be measured by an ultraviolet-visible-near-infrared spectrophotometer UH4150 (manufactured by Hitachi High-Tech Corporation).

[0044] Furthermore, the sheet resistance of the conductive mesh layer, as a predicted resistance value assuming a solid part, is 10×10 -2 Ω / sq or less, preferably 5×10 -2 Ω / sq or less, more preferably 3×10 -2 Ω / sq or less, still more preferably 1×10 -2 Ω / sq or less, and thereby the transmission loss in a 50-mm-long microstrip line can be preferably 1 dB or less, more preferably 0.7 dB or less, still more preferably 0.5 dB or less. The value of the sheet resistance can be measured by Hall effect measurement.

[0045] By performing the above steps S1 to S4 or S5, a conductive mesh layer having a designed shape can be stably formed. As a result, the conductive mesh layer has a line width W of 100 to 150 μm, an array pitch Pt of the openings of the conductive mesh layer of 950 to 1000 μm, a visible light transmittance of the conductive mesh layer exceeding 50%, and a sheet resistance of the conductive mesh layer of 10×10 -2 Ω / sq or less. As a result, even when the antenna of the mesh pattern is formed of a conductive material, both the high transparency of the antenna and the high antenna radiation efficiency can be more reliably and stably enjoyed.

Example

[0046] Hereinafter, regarding Examples 1 to 8 having different characteristics of the silver paste, printing conditions, firing conditions, and blackening treatment, the results of measuring the shape and characteristics of the formed antenna will be described. The respective conditions and measurement results are summarized in Table 1. The overall shape of the antenna was a spiral type having the outer frame line shown in FIG. 6. Further, FIG. 9 is an explanatory diagram showing the test results for Examples 1, 4, 5, and 8. Examples 1 and 2 are examples, and Examples 3 to 8 are comparative examples.

[0047]

Table 1

[0048] The conditions common to Examples 1 to 8 are as follows. (Base material) Material: Borosilicate glass Plate thickness: 0.7 mm (Silver paste) Binder: Bi 2 O 3 5 to 20%, B 2 O 3 1 to 5% (Screen printing) Screen printing machine: Microtech MT320 Squeegee moving speed: 30 mm / sec. Squeegee pressure: 0.25 MPa Clearance between the transparent substrate and the screen plate: 2.3 mm Mesh count of the screen version: #640

[0049] For each example, evaluation was carried out by the following measurement methods. (Sheet resistance) The sheet resistance was measured by Hall effect measurement.

[0050] (Visible light transmittance, visible light reflectance) The visible light transmittance and visible light reflectance were measured by an ultraviolet-visible-near-infrared spectrophotometer UH4150 (manufactured by Hitachi High-Tech Corporation).

[0051] <Example 1> US202AT manufactured by Dainippon Chemical Industry Co., Ltd. was used as the silver paste PT1. As a result of measuring the average particle size of the silver particles contained in the silver paste by SEM observation, it was 0.2 μm. Further, as a result of measuring the mass percentage concentration of the silver particles by ICP analysis, it was 65 to 80 mass%.

[0052] With the line width W of the mesh pattern being 100 μm, the arrangement pitch Pt of the openings of the mesh pattern being 1000 μm, and the frame line width of the outer frame line being 100 μm, the mesh pattern of the antenna was formed by screen printing. For the mesh pattern of the silver paste after printing, the first-stage pre-firing was carried out at 200 °C for 10 minutes, and then the second-stage full firing was carried out at 500 °C for 30 minutes. Carbon black was overcoated on the fired conductive mesh layer for blackening treatment.

[0053] As a result of measuring the shape of the conductive mesh layer formed under the above conditions, the line width W of the mesh pattern was 110 to 120 μm, the arrangement pitch Pt of the openings was 980 to 990 μm, the aperture ratio (line width W / arrangement pitch Pt) was 81%, the film thickness of the fired conductive mesh layer was 5 μm, and the sheet resistance was 5.4×10 -2 (Ω / sq). Also, the radio wave transmission characteristics at 4 GHz were -1.11 dB / 100 mm, the visible light transmittance of the conductive mesh layer was 60%, and the visible light reflectance was 6%. The aperture ratio (W / Pt) is a value obtained by dividing the arrangement pitch area by the unit area consisting of the arrangement pitch and the line width.

[0054] <Example 2> Example 2 is the same as Example 1, except that the blackening treatment in Example 1 was replaced with treatment with sodium hypochlorite (NaClO) instead of carbon black paste. As a result, almost the same results as in Example 1 were obtained.

[0055] <Example 3> Example 3 is the same as Example 1, except that the array pitch Pt of the openings in the printing conditions of Example 1 was changed from 1000 μm to 2000 μm, and the silver paste PT1 in Example 1 was changed to a silver paste PT2 (GPMG5311 manufactured by Murata Manufacturing Co., Ltd.) with an average particle size of silver particles of 2 μm, and the mass percentage concentration of silver particles was set to 82% by mass. This silver paste PT2 has a shear viscosity of 210 Pa·s at a shear rate of 0.1 s -1 and has a shear viscosity that is about 1 / 9 smaller than that of silver paste PT1. The firing treatment was the same as in Example 1, except that the main firing was carried out at 630 °C for 5 minutes. As a result, the array pitch Pt of the openings in the fired conductive mesh layer of the mesh pattern increased to 1980 - 1990 μm. The aperture ratio (W / Pt) of the fired conductive mesh layer increased to 89%, and the visible light transmittance increased to 70%. Also, the radio wave transmission characteristics at 4 GHz were -1.4 dB / 100 mm.

[0056] <Example 4> Example 4 is the same as the conditions of Example 3, except that the blackening treatment of Example 3 was not carried out. As a result, poor adhesion of the silver paste occurred during the main firing. Also, compared with Example 1, the line width of the conductive mesh layer increased, the aperture ratio and film thickness after firing decreased, and the sheet resistance increased. The radio wave transmission characteristics at 4 GHz are the same as in Example 3, and the visible light transmittance of the conductive mesh layer decreased to 50%. As shown in FIG. 9, the thin lines in Examples 1 to 4 above were all printed in the designed shape.

[0057] <Example 5> Example 5 is the same as Example 1 except that the array pitch Pt of the printing conditions is changed from 1000 μm to 300 μm and the blackening treatment is not performed. As a result, the radio wave transmission characteristic at 4 GHz was -1.09 dB / mm. Also, the visible light transmittance of the conductive mesh layer was 6%, and the visible light reflectance was 90%. This is because, as shown in FIG. 10, the thin lines did not overlap with each other to form a lattice-like mesh pattern.

[0058] <Example 6> Example 6 is the same as Example 4 except that the array pitch Pt of the printing conditions is changed from 1000 μm to 300 μm. As a result, the radio wave transmission characteristic at 4 GHz was -1.09 dB / mm. Also, similar to Example 5, the thin lines of the conductive mesh layer did not overlap with each other to form a lattice-like mesh pattern, and the visible light transmittance was 6%, and the visible light reflectance was 90%.

[0059] <Example 7> Example 7 is the same as Example 1 except that the array pitch Pt of the printing conditions is changed from 1000 μm to 2000 μm and the blackening treatment is not performed. As a result, the array pitch Pt of the openings increased to 1980 - 1990 μm, the aperture ratio of the conductive mesh layer increased to 89%, and the sheet resistance was 4.9×10 -2 Ω / sq. Also, the visible light transmittance of the conductive mesh layer was 70%, and the visible light reflectance was 26%.

[0060] <Example 8> Example 8 is the same as Example 4 except that the line width W of the printing conditions is changed from 100 μm to be formed on one side so as to cover the entire surface of the transparent substrate with silver paste. As a result, the film thickness of the conductive mesh layer after firing was 3 μm, and the radio wave transmission characteristic at 4 GHz was -0.43 dB / 100 mm. Also, the aperture ratio was 0%, and as shown in FIG. 10, the antenna became opaque. Also, the visible light transmittance of the conductive mesh layer was 0%, and the visible light reflectance was 100%.

[0061] Thus, the present invention is not limited to the above-described embodiments, and it is also contemplated by the present invention that those skilled in the art can make changes and applications based on combining each configuration of the embodiments with each other, the description in the specification, and well-known techniques, and such changes and applications are included in the scope for which protection is sought.

[0062] As described above, the following matters are disclosed in this specification. [1] A method for manufacturing a transparent antenna in which a mesh pattern antenna is formed on a transparent substrate, comprising: (1) preparing the transparent substrate and a conductive paste as a printing material for the antenna, and adjusting the viscoelasticity of the conductive paste to 500 to 2000 Pa·s at a shear rate of 0.1 s -1 and 1 to 20 Pa·s at a shear rate of 250 s -1 ; (2) spreading the conductive paste on a screen plate having holes corresponding to the mesh pattern of the antenna, and then screen-printing the conductive paste filled in the holes onto the transparent substrate while pressing the screen plate against the transparent substrate; and (3) heating the conductive paste of the mesh pattern printed on the transparent substrate in (2) to form a conductive mesh layer in which the conductive paste is fired on the transparent substrate, in that order, wherein the conductive mesh layer fired in (3) has a line width of 50 to 200 μm, an array pitch of openings of the conductive mesh layer of 900 to 1100 μm, a visible light transmittance of the conductive mesh layer exceeding 50%, and a sheet resistance of the conductive mesh layer of 10×10 -2 Ω / sq or less, a method for manufacturing a transparent antenna. [2] The method for manufacturing a transparent antenna according to [1], wherein the conductive paste contains silver particles. [3] The method for manufacturing a transparent antenna according to [2], wherein the mass percentage concentration of the silver particles in the conductive paste is 50 to 95% by mass. [4] The method for manufacturing a transparent antenna according to [2], wherein the average particle size of the silver particles in the conductive paste is 0.1 to 1.0 μm. [5] The method for manufacturing a transparent antenna according to [1], wherein the transparent substrate is glass or resin. [6] The method for manufacturing a transparent antenna according to [1], wherein the thickness of the transparent substrate is 100 to 2000 μm. [7] The method for manufacturing a transparent antenna according to [1], further comprising a blackening treatment for blackening the surface of the conductive mesh layer. [8] The method for manufacturing a transparent antenna according to [7], wherein the blackening treatment includes a treatment of applying or dipping an organic material containing carbon black to the conductive mesh layer. [9] The method for manufacturing a transparent antenna according to [7], wherein the blackening treatment includes a treatment of forming an oxide film on the surface of the conductive mesh layer.

[10] The method for manufacturing a transparent antenna according to [7], wherein the reflectance of the conductive mesh layer after the blackening treatment is 0 to 10%.

[11] The method for manufacturing a transparent antenna according to [1], wherein the antenna includes an antenna conductor formed on a first main surface of the transparent substrate and a ground conductor formed on a second main surface of the transparent substrate.

[12] The method for manufacturing a transparent antenna according to [1], wherein the transmission loss per 50 mm of the transparent antenna is 1.0 dB or less.

Explanation of Reference Numerals

[0063] 11 Transparent substrate 11a First main surface 11b Second main surface 13 Antenna conductor 15 Ground conductor 17 Antenna terminal portion 19 Antenna portion 21 Fine wire 23 Opening 25 Outer shape frame wire 100 Antenna

Claims

1. A method for manufacturing a transparent antenna in which an antenna with a mesh pattern is formed on a transparent substrate, (1) Prepare the transparent substrate and the conductive paste that is the printing material of the antenna, and adjust the viscoelasticity of the conductive paste so that it is 500 to 2000 Pa·s at a shear rate of 0.1 s －１ and 1 to 20 Pa·s at a shear rate of 250 s －１ respectively. (2) After spreading the conductive paste on a screen plate having holes corresponding to the mesh pattern of the antenna, while pressing the screen plate against the transparent substrate, screen-printing the conductive paste filled in the holes onto the transparent substrate, and (3) Heating the conductive paste of the mesh pattern printed on the transparent substrate in (2) to form a conductive mesh layer in which the conductive paste is fired on the transparent substrate, in this order, The conductive mesh layer fired in the above (3) has a line width of 50 to 200 μm, an array pitch of openings of the conductive mesh layer of 900 to 1100 μm, a visible light transmittance of the conductive mesh layer exceeding 50%, and a sheet resistance of the conductive mesh layer of 10×10 －２ Ω / sq or less, a method for manufacturing a transparent antenna.

2. The conductive paste contains silver particles, The method for manufacturing a transparent antenna according to Claim 1.

3. The mass percentage concentration of the silver particles in the conductive paste is 50 to 95% by mass, The method for manufacturing a transparent antenna according to Claim 2.

4. The average particle size of the silver particles in the conductive paste is 0.1 to 1.0 μm, The method for manufacturing a transparent antenna according to Claim 2.

5. The transparent substrate is glass or resin, The method for manufacturing a transparent antenna according to Claim 1.

6. The thickness of the transparent substrate is 100 to 2000 μm, The method for manufacturing a transparent antenna according to Claim 1.

7. Further including a blackening treatment for blackening the surface of the conductive mesh layer, The method for manufacturing a transparent antenna according to Claim 1.

8. The blackening treatment includes a treatment of applying or dipping an organic material containing carbon black to the conductive mesh layer, The method for manufacturing a transparent antenna according to Claim 7.

9. The blackening treatment includes a treatment of forming an oxide film on the surface of the conductive mesh layer, The method for manufacturing a transparent antenna according to Claim 7.

10. The reflectance of the conductive mesh layer after the blackening treatment is 0 to 10%, The method for manufacturing a transparent antenna according to Claim 7.

11. The antenna includes an antenna conductor formed on the first main surface of the transparent substrate and a ground conductor formed on the second main surface of the transparent substrate, The method for manufacturing a transparent antenna according to Claim 1.

12. The transmission loss per 50 mm of the transparent antenna is 1.0 dB or less, The method for manufacturing a transparent antenna according to Claim 1.

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