JP5636735B2 - Transparent antenna element and transparent antenna - Google Patents

Description

  The present invention relates to an optically transparent element for a transparent antenna and a transparent antenna that can transmit and receive electromagnetic waves with a conductive layer formed in a predetermined pattern.

Along with the development of electronic technology, various communication systems using wireless technology such as mobile phones, car navigation systems mounted on automobiles, and security systems using window glass break sensors have been developed. In order to cope with these wireless systems, an antenna capable of transmitting, receiving, or transmitting / receiving corresponding to the electromagnetic waves of each system is required.
For example, in addition to telephone / Internet communication functions, mobile phone antennas are required to support a wide variety of communication frequencies such as television and radio broadcasting, GPS (Global Positioning System), RFID (Radio Frequency Identification), and infrared communication. Multiple antennas are needed. In order to mount this on a single mobile phone, the space allocated per antenna becomes increasingly narrow, and there is a problem that the reception sensitivity cannot be satisfied.
As a method for solving this type of problem, a transparent antenna configured to allow visible light to pass therethrough has been proposed so that it can be mounted on a display screen of a mobile phone to which a conventional antenna is not attached (Patent). Reference 1).

  In addition, a transparent antenna has been proposed in which an antenna can be installed on the surface of a wireless device or wireless terminal or on a display window so that the antenna can be moved away from electronic components inside the device, and the influence on the antenna can be reduced. (See Patent Document 2).

WO2006 / 106982 pamphlet JP 2008-306552 A WO2008 / 149969 pamphlet

The display-use transparent antenna described in Patent Document 1 has a sheet-like transparent substrate having insulating properties and an antenna pattern formed in a planar shape on the surface of the transparent substrate, and the conductive portion of the antenna pattern has a mesh structure. It is a transparent antenna for displays which consists of a conductive thin film.
However, a specific network structure of the conductive part is formed by forming a transparent anchor layer in which an electroless plating catalyst is dispersed on the surface of a transparent substrate, and then performing electroless plating and electroplating to form the conductive layer. After that, a pattern is formed by exposure using a photomask coated with a photoresist and corresponding to a predetermined antenna pattern. In this method, the number of steps for forming the pattern is large, and a conductive layer is formed on the entire surface of the transparent substrate, and then unnecessary portions are etched. Therefore, the conductive portions to be etched are wasted, and the plating solution In addition, there is a problem that the cost of the exposure processing liquid is increased and the cost is increased and the demand for cost reduction cannot be met.

  In addition, since the transparent antenna described in Patent Document 2 has a transparent conductive film formed of a tin-doped indium oxide (ITO) thin film, an electric resistance (hereinafter also simply referred to as resistance) has a small thickness. Therefore, if the film thickness is increased, transparency and flexibility are not achieved, so that transparency and conductivity are not compatible. In addition, there is inherently a problem of resource depletion of rare metals such as indium.

On the other hand, as a technique requiring a transparent conductive film, there is an electromagnetic wave shielding material for shielding electromagnetic waves leaking on the front side (observer side) of the plasma display panel.
The present applicant transfers a conductive material composition onto a transparent substrate by intaglio printing, and in an electromagnetic wave shielding material formed with a conductive pattern, the pattern breakage based on the transfer failure of the conductive material composition Have proposed an electromagnetic shielding material that does not cause defects such as poor shape, insufficient transfer rate, and low adhesion (see Patent Document 3).
When the present inventors applied the conductive mesh of this electromagnetic wave shielding material to a transparent antenna, flexibility, adhesion to a transparent substrate, and light transmittance are satisfactory, but the resistance value needs to be further reduced. It has been found.

  The present invention has been made in view of the above-mentioned problems, and (i) a low resistance value, (ii) rich flexibility, and (iii) a conductive portion and a transparent substrate. An object of the present invention is to provide a transparent antenna element and a transparent antenna that have high adhesion, and (iv) have a high light transmittance in the visible light region, and have a high transition rate and can reduce manufacturing costs.

As a result of intensive studies to solve the above problems, as a transparent antenna element, a transparent conductive mesh pattern developed as a highly conductive electromagnetic shielding material, control of the distribution of the conductive particle density in the conductive mesh pattern, and conductive particles The present invention was completed by knowing that it can be applied to a transparent antenna by, for example, fusing together.
That is, the present invention
(1) A transparent antenna element having a transparent substrate, a primer layer formed on the transparent substrate, and a convex pattern layer made of a conductive composition formed in a predetermined pattern on the primer layer. In the primer layer, the portion where the convex pattern layer is formed is thicker than the portion where the convex pattern layer is not formed, and the conductive composition is conductive. The conductive particle distribution in the convex pattern layer is relatively sparse in the vicinity of the primer layer and dense in the vicinity of the top of the convex pattern layer. A transparent antenna element, characterized in that
(2) A transparent antenna element having a transparent substrate, a primer layer formed on the transparent substrate, and a convex pattern layer made of a conductive composition formed in a predetermined pattern on the primer layer. In the primer layer, the portion where the convex pattern layer is formed is thicker than the portion where the convex pattern layer is not formed, and the conductive composition is conductive. Comprising particles and a binder resin, and the interval between the conductive particles in the convex pattern layer is relatively large in the vicinity of the primer layer and small in the vicinity of the top of the convex pattern layer, A transparent antenna element characterized by
(3) In the observation by an electron micrograph, the conductive particles in the cross section of the convex pattern layer include those in which a plurality of conductive particles are partially fused (1) or (2) And (4) the transparent antenna element according to any one of (1) to (3),
Is to provide.

The element for transparent antenna obtained by the present invention forms a conductive mesh portion by intaglio printing and achieves low resistance, so that (i) low resistance and (ii) flexibility (flexibility) (Iii) high adhesion between the conductive portion and the transparent substrate, (iv) high light transmittance in the visible light region, and cost reduction.
Therefore, even if it is attached to a display such as a mobile phone, a window glass of a vehicle, a window glass of a building, etc., which requires transparency in the visible light range, it is not visually recognized, has a good appearance and is transparent at low cost. Can be used as an antenna. In particular, in a cellular phone, although the main body size is small, since the proportion of the display is relatively large, the area of the display can be used effectively.
In addition, the transparent antenna obtained by the present invention can be used as an antenna for moving equipment such as automobiles and vehicles, because it has a high light transmittance and can secure transparency even when pasted on the front or rear window glass. As the rod antenna does not obstruct the field of view that hinders the vehicle's obstruction, it is not necessary to provide a protruding portion on the vehicle body. A good-looking design is possible.
Furthermore, in a security system using a window glass breaking sensor, if the transparent antenna of the present invention is directly attached to the window glass as an antenna for the system, the field of view is not obstructed, the construction is simple, and the cost is low. Can promote the spread of the system.
In addition, since the transparent antenna of the present invention has high light transmittance and excellent transparency, even if it is used in a wide area, it does not impair visibility, so that it can be used as a highly sensitive antenna.

It is a typical top view which shows an example of the element for transparent antennas of this invention. It is an enlarged view of the A-A 'cross section in FIG. It is typical sectional drawing which expands and shows a part of FIG. It is a schematic diagram which shows the form which fills the dent of the electroconductive material composition in a recessed part with a primer layer, and the electroconductive material composition transfers. It is explanatory drawing of the process of transcribe | transferring an electroconductive material composition on a primer layer. It is a cross-sectional SEM photograph of the convex pattern layer in the element for transparent antennas of this invention. It is a cross-sectional SEM photograph of the convex pattern layer in which the conductive particles are partially fused. It is explanatory drawing of the fusion path | route in the cross-sectional SEM photograph of the convex pattern layer of FIG. It is a schematic diagram of a λ / 2 dipole antenna using the element for transparent antenna of the present invention. It is explanatory drawing of the aspect which comprised the element for transparent antennas of this invention in the meander shape. It is explanatory drawing of the example which used the transparent antenna of this invention for the display part of the mobile telephone. It is explanatory drawing of the example which used the transparent antenna of this invention for the rear window of the motor vehicle. It is explanatory drawing of the measuring method of the frequency characteristic and directivity of the transparent antenna of this invention. It is a conceptual diagram of the electroconductive particle density distribution in a convex pattern layer. 6 is a schematic diagram of a λ / 2 dipole antenna using the transparent antenna element of Example 2. FIG.

  Next, embodiments of the present invention will be described in detail, but the present invention is not limited to the following embodiments, and various modifications can be made within the scope of the gist of the present invention.

[Elements for transparent antennas]
FIG. 1 is a schematic plan view showing an example of the transparent antenna of the present invention, and FIG. 2 is an enlarged view of an AA ′ cross section in FIG. FIG. 3 is a schematic cross-sectional view showing a part of FIG. 2 further enlarged. The element 10 for a transparent antenna according to the present invention has a transparent substrate 1, a primer layer 2 formed on the transparent substrate 1, and a predetermined pattern represented by a mesh shape with a conductive composition on the primer layer 2. It has the convex pattern layer 3 formed, it has the metal layer 4 formed on the convex pattern layer 3 as needed, and further has the protective layer 9 as needed. Although not shown, an adhesive layer made of an adhesive or the like may be formed on the side surface of the transparent substrate 1 opposite to the convex pattern layer 3 as necessary. In FIG. 1, reference numeral 7 is a conductive (antenna) pattern portion, and reference numeral 8 is an electrode portion.
Hereinafter, the configuration of the present invention will be described in detail. The pattern of the conductive portion constituting the transparent antenna element of the present invention is hereinafter referred to as “conductive pattern”.

(Transparent substrate)
The transparent substrate 1 may be appropriately selected from known materials and thicknesses in consideration of required physical properties such as transparency (light transmittance) in the visible light region, heat resistance, and mechanical strength, such as glass and ceramics. A plate-like rigid body such as a transparent inorganic plate or a resin plate may be used. 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 and supplied from a winding (roll), appropriately processed, and then wound and stored in the winding.

Examples of resins for resin films and resin plates include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), ethylene glycol-1,4 cyclohexanedimethanol-terephthalic acid copolymer, ethylene glycol-terephthalic acid-isophthalic acid copolymer. Polymers, polyester resins such as polyester thermoplastic elastomers, acrylic resins such as polymethyl methacrylate, polyolefin resins such as polypropylene and cycloolefin polymers, cellulose resins such as triacetyl cellulose, polycarbonate resins, polyimides ( PI) based resin and the like. Among them, polyethylene terephthalate is a transparent base material whose biaxially stretched film is preferable in terms of heat resistance, mechanical strength, light transmittance, cost, and the like.
Examples of the transparent inorganic material include soda glass, potassium glass, borosilicate glass, lead glass, and other transparent ceramics such as PLZT, quartz, and the like.

The thickness of the transparent substrate is basically not particularly limited and is appropriately selected depending on the application. When a flexible resin film is used, it is, for example, about 12 to 500 μm, preferably about 25 to 200 μm. In the case of using a resin or transparent inorganic plate, the thickness is, for example, about 500 to 5000 μm.
Moreover, in order to ensure the adhesiveness with the primer layer 2 described below, a surface treatment for improving the adhesiveness, an easy-adhesion layer, a base layer, and the like may be separately provided on the surface of the transparent substrate 1.

(Primer layer)
The primer layer 2 improves the transfer property of ink (conductive composition) from the plate to the printing material (transparent substrate) during the printing of the convex pattern layer 3, and the conductive composition after the transfer. This is a layer for improving the adhesion between the substrate and the substrate. That is, both the transparent base material and the convex pattern layer have good adhesion, and it is also a transparent layer for ensuring the light transmittance of the opening (the convex pattern layer non-formed part).
Furthermore, the primer layer 2 is a layer that is provided on the transparent substrate 1 in a state where fluidity can be maintained, and is formed as a layer that solidifies from a liquid while in contact with the intaglio during intaglio printing. This layer is solidified when a transparent antenna is formed.

The material constituting the primer layer is not particularly limited. However, in the present invention, an ionizing radiation curable composition containing a liquid (fluid) ionizing radiation polymerizable compound in an uncured state is applied and cured ( A layer formed by solidification) is preferably used. Hereinafter, this material will be mainly described in detail.
As the ionizing radiation polymerizable compound, monomers and / or prepolymers that are polymerized and cured by a reaction such as crosslinking with ionizing radiation are used.
Such monomers include, for example, methyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, isobornyl (meth) acrylate, dicyclopentenyl (meth) as radical polymerizable monomers. ) Monofunctional (meth) acrylates such as acrylate, dipropylene glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate , Pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) a Polyfunctional (meth) acrylates of various (meth) acrylates such relations and the like. Here, the expression (meth) acrylate means acrylate or methacrylate. Examples of the cationic polymerizable monomer include alicyclic epoxides such as 3,4-epoxycyclohexenylmethyl-3 ′, 4′-epoxycyclohexene carboxylate, glycidyl ethers such as bisphenol A diglycidyl ether, 4-hydroxybutyl vinyl ether And vinyl ethers, and oxetanes such as 3-ethyl-3-hydroxymethyloxetane.

Such prepolymers (or oligomers) include, for example, urethane (meth) acrylate, epoxy (meth) acrylate, polyester (meth) acrylate, triazine (meth) acrylate, and silicon (meth) acrylate as radical polymerizable prepolymers. And various (meth) acrylate prepolymers such as polythiol prepolymers such as trimethylolpropane trithioglycolate and pentaerythritol tetrathioglycolate, and unsaturated polyester prepolymers. Other examples of the cationic polymerizable prepolymer include novolac type epoxy resin prepolymer and aromatic vinyl ether type resin prepolymer.
These monomers or prepolymers may be used alone or in combination of two or more types of monomers, two or more types of prepolymers, or one type of monomer, depending on the required performance, coating suitability, etc. A mixture of the above and one or more prepolymers can be used.

When ultraviolet rays or visible rays are employed as the ionizing radiation, a photopolymerization initiator is usually added. As a photopolymerization initiator, in the case of a radical polymerizable monomer or prepolymer, a compound such as a benzophenone-based, thioxanthone-based, benzoin-based, or acetophenone-based compound, or in the case of a cationic polymerization-based monomer or prepolymer, Metallocene, aromatic sulfonium and aromatic iodonium compounds are used. These photopolymerization initiators are added in an amount of about 0.1 to 5 parts by mass with respect to 100 parts by mass of the composition comprising the monomer and / or prepolymer.
In addition, as the ionizing radiation, ultraviolet rays or electron beams are typical, but in addition, electromagnetic waves such as visible rays, X-rays and γ rays, or charged particle beams such as α rays and various ion rays are used. You can also

  When using a material system that peels heavily after curing the primer layer on the plate surface (if it has a good adhesion to the plate), release the plate surface or apply a release material However, considering the processing cost and the life of mold release capability, a mold release agent is added to the primer layer as necessary. The release agent used in the present invention means that in the production of a transparent antenna, the primer layer on the transparent substrate that has undergone the primer curing step reduces the force (peeling force) required for peeling from the plate surface so that it can be peeled off smoothly. An additive for improving the peelability. Examples of such release agents include higher fatty acid esters, phosphate esters, silicone resin release agents, fluororesin release agents, and the like of mono- or polyhydric alcohols.

The higher fatty acid ester is preferably a partial ester or complete ester of a monovalent or polyhydric alcohol having 1 to 20 carbon atoms and a saturated fatty acid having 10 to 30 carbon atoms. Examples of partial esters or complete esters of mono- or polyhydric alcohols and saturated fatty acids include stearic acid monoglyceride, stearic acid monosorbate, behenic acid monoglyceride, pentaerythritol monostearate, pentaerythritol tetrastearate, propylene glycol monostearate Examples thereof include rate, stearyl stearate, palmityl palmitate, butyl stearate, methyl laurate, isopropyl palmitate, 2-ethylhexyl stearate and the like.
Among these, stearic acid esters such as stearic acid monoglyceride and pentaerythritol tetrastearate are particularly preferable from the viewpoints of transparency and releasability.
These release agents can be used alone or in combination of two or more.
The release agent is preferably added in an amount of 0.1 to 5 mass%, particularly preferably 0.5 to 3 mass%, based on the total amount of the ionizing radiation curable composition forming the primer layer. If it is less than 0.1% by mass, the releasability from the plate surface of the primer layer is not improved, and even if it is added in excess of 5% by mass, the release performance is saturated and it is not economical.

  The ionizing radiation curable composition may contain a solvent, but in that case, since a drying step is required after coating, it is a type that does not contain a solvent (non-solvent type or solvent-free type) in consideration of cost. preferable. When a solvent is added for the purpose of improving the appearance or coating applicability, drying is necessary. However, if the amount of the solvent is about several percent, it may be dried after curing. The amount of residual solvent is preferably as small as possible, but may not be completely zero as long as there is no influence on physical properties and durability.

  The thickness of the primer layer 2 (TB; evaluated by the thickness of the non-formed portion of the convex pattern layer 3 as shown in FIG. 3) is not particularly limited, but usually the thickness after curing is about 1 μm to 100 μm. It is formed. Further, the thickness (TB) of the primer layer 2 is usually the sum of the convex pattern layer 3 and the primer layer 2 (total thickness. In FIG. 3A, the top of the convex pattern layer 3 and the transparent layer are transparent. It is about 1 to 50% of the altitude difference from the surface of the substrate 1.

(Convex pattern layer made of conductive composition)
In the element for transparent antenna in the present invention, the convex pattern layer 3 made of a conductive composition is provided on the primer layer 2 in a predetermined pattern. The pattern shape is typically a mesh shape (mesh or lattice), but other shapes such as a stripe shape (parallel line group or stripe pattern) and a spiral shape are also used. In the case of a mesh shape, the unit cell shape may be a triangle such as a regular triangle or an unequal side triangle, a square such as a square, rectangle, trapezoid or rhombus, a polygon such as a hexagon or octagon, a circle or an ellipse. Used. In addition, for the purpose of reducing moire, a random mesh pattern or a pseudo-random mesh pattern can be used. The line width and the inter-line pitch may be dimensions that are usually employed. For example, the line width can be 5 to 50 μm, and the line-to-line pitch can be 100 to 500 μm. The aperture ratio (ratio of the total area of the openings in the total area of the convex pattern layer) is usually about 50 to 95%.
The line width is preferably 30 μm or less, more preferably 20 μm or less, from the viewpoint of further miniaturization in order to obtain a highly transparent material.

Further, the thickness of the convex pattern layer 3 varies depending on the resistance value of the convex pattern layer 3, but from the balance between the performance of the transparent antenna and the suitability of adhesion of other members onto the convex pattern layer, In the measurement at the part (the top of the projection pattern), it is usually 2 μm or more and 50 μm or less, preferably 5 μm or more and 20 μm or less.
The convex pattern layer 3 is obtained by forming a conductive composition (also referred to as conductive ink or conductive paste) containing conductive particles and a binder resin on the primer layer 2 by an intaglio printing method described later. be able to. In particular, as shown in the conceptual diagram of FIG. 14, the convex pattern layer 3 has the conductive particles Cp distributed in a specific distribution state as described later and as illustrated in FIGS. 14 and 6 to 8. Then, as shown in FIG. 8, in at least a part of the conductive particles Cp, a path serving as a current path is formed which is formed by connecting or fusing adjacent conductive particles Cp. It is characterized by. Between these conductive particles Cp, a binder resin R is interposed in a gap except for a contact or fusion between adjacent conductive particles, and the conductive particles Cp in the convex pattern layer 3 are bound to each other. It becomes.
Further, in order to stably form a metal layer by electrolytic plating on the surface of the convex pattern layer, it is preferable that the convex pattern layer made of the conductive composition has a lower surface resistivity. Specifically, it is preferable that the surface resistivity is 1.5Ω / □ or less. Furthermore, without forming a metal layer on the surface of the convex pattern layer, and for exhibiting sufficient transparent antenna properties in a region where the line width frequently used as a transparent antenna mesh is 25 μm or less and the line thickness is 20 μm or less. The lower the surface resistivity of the convex pattern layer made of the conductive composition, the better. Specifically, the surface resistivity may be 1Ω / □ or less, more preferably 0.8Ω / □ or less. In order to set the surface resistivity of the convex pattern layer to 0.8 Ω / □ or less, a metal such as silver, gold, or copper having a low volume resistivity is selected as the material of the conductive particles as described later. That the conductive particles have an average particle size of 1 μm or less, the conductive particles have a mixed particle size of small particles and large particles, and the top of the convex pattern layer. It is effective to increase the density of the conductive particles in the substrate and to transfer the convex pattern layer onto the primer layer and then treat it with water in a high temperature or with an acid. is there. Of these, one or more means may be used in combination.
In addition, in order to make the surface resistivity 1.0 Ω / □ or less, the convex pattern layer may be appropriately subjected to metal plating made of a low resistivity metal as described later.

The apparent value of the volume resistivity (volume electrical resistivity) indicating the conductivity of the conductive composition itself varies depending on the shape to be printed. For example, compared to the volume resistivity when a commercially available conductive paste is formed in a solid shape (a shape without an opening), the apparent volume resistivity when formed as a pattern is calculated by the following formula: The smaller the shape, the larger.
(Formula): Apparent volume resistivity [Ω · cm] = Surface resistivity of pattern portion [Ω / □] ×
Pattern portion thickness [cm] x pattern occupancy rate-Pattern portion thickness: thickness of pattern formation portion-total thickness of pattern non-formation portion (opening)-Pattern occupancy rate: area of pattern formed portion of unit area For example, the volume resistivity when a commercially available dry-curing silver paste is solidly applied and dried is usually on the order of 10 ⁻⁵ [Ω · cm] or less. Volume resistivity often increases by an order of magnitude or more. This is due to a reduction in the filling rate of silver particles and the chance of contact between the particles. For example, even when the pattern occupancy is the same, the resistance increases as the line width or thickness approaches the particle size of the conductive particles. Here, if the above-mentioned various means are used, this increase in volume resistivity can be suppressed. In particular, the apparent volume resistivity is reduced to a value of 80 to 50% by performing the treatment by temperature and humidity (electrical resistance reduction treatment process) as compared to before the treatment.
Further, even by acid treatment, the apparent volume resistivity is reduced to a value of 80 to 50% compared to before the treatment.

The conductive particles constituting the conductive composition include particles of low resistivity metal such as gold, silver, platinum, copper, nickel, tin, and aluminum, or high resistivity metal particles and resin particles as core particles. Examples thereof include particles whose surfaces such as non-metallic inorganic particles are coated with a low resistivity metal such as gold or silver, graphite particles, conductive polymer particles, and conductive ceramic particles.
The shape of the conductive particles can be selected from various polyhedron shapes such as a regular polyhedron shape, a truncated polyhedron shape, a spherical shape, a spheroid shape, a scale shape, a disc shape, a dendritic shape, and a fibrous shape. In particular, a polyhedral shape, a spherical shape, or a spheroid shape is preferable. These materials and shapes may be appropriately mixed and used.
Since the size of the conductive particles is arbitrarily selected depending on the type, it cannot be specified unconditionally, but those having an average particle diameter of about 0.01 to 10 μm can be preferably used. In order to obtain a good transparent antenna property by reducing the electrical resistance of the resulting convex pattern layer [preferably, the surface resistivity (simply abbreviated as surface resistance) is 0.8Ω / □ or less as described above]. The average particle size is preferably small. From this viewpoint, the average particle size is preferably 0.1 to 1 μm. In general, particles having an average particle diameter as small as several tens of nanometers, which are called “nanoparticles”, lead to high costs, and when a binder resin is added, the performance decreases and the stability as an ink also decreases. As for the particle size distribution, in order to reduce the electric resistance of the resulting convex pattern layer, the distribution width is relatively large as shown in FIG. It is better to consist of a mixed system of particles and relatively small particle size particles. For example, a mixed system of small particle diameter particles having a particle diameter of 0.01 μm to 1 μm and large particle diameter particles having a particle diameter of 5 to 10 μm is preferable. The mixing ratio of both particles in such a mixed system is such that the number of small particles: the number of large particles: 1: 9 to 9: 1, in particular, the number of small particles: the number of large particles: 5: 5. A range of ˜9: 1 is preferred. Naturally, if particles larger than the line width and thickness of the pattern are mixed, defects such as omissions and streaks occur frequently during printing, so the average size or the maximum particle size of the large particle size varies depending on the pattern design. come.
In addition to mixing a plurality of types of particles having different average particle sizes, particles having a certain particle size distribution may be used from the beginning.

The reason why the surface resistivity of the conductive composition (convex pattern layer) is reduced when the particle size of the conductive particles is a mixed system of small particle size particles and large particle size particles is that When the cross-section of the convex pattern layer formed is observed with a microscope, there is no contact between the large particle size particles, presuming that a distribution in which small particle size particles are filled in the gaps in which the large particle size particles are distributed is observed. It is considered that the gap between the portions is reinforced by the contact of the small particle diameter particles interposed therein, and the total electrical contact area between the large and small particles dispersed in the conductive composition is increased. That is, in general, the electrical resistance R of an object is represented by the formula R = ρL / S, where S is the cross-sectional area of the object, L is the length, and ρ is the volume resistivity. The increase in the total contact area between the particles corresponds to an increase in the equivalent cross-sectional area S in the entire aggregate of conductive particles in the convex pattern layer.
The distribution of the conductive particles in the convex pattern layer can be selected from various forms according to desired characteristics and manufacturing suitability, but from one end in the convex pattern layer to the other end. It is necessary to secure at least one path through which current can flow. For this purpose, it is necessary that at least one path as shown in FIG. 8 is formed in which adjacent conductive particles are in contact with each other with a distance of 0 between them and a fused structure is connected. As a particularly preferable form for forming such a path, as shown in the electron micrograph of FIG. 8 , in the vicinity of the top of the convex pattern layer (in the direction away from the primer layer), there is a relative space between the particles. On the other hand, in the vicinity of the bottom of the convex pattern layer (in the direction approaching the primer layer), there is a distribution in which the interval between particles is relatively large.
for that purpose,
(I) As conceptually shown in FIG. 14, the particle number density in the convex pattern layer, that is, the number of particles per unit volume is relatively high (densely) near the top, In the vicinity of the primer layer, the particle number density is distributed so as to be low (sparse or coarse).
(Ii) The particle number density in the convex pattern layer is constant, and the particle diameter is distributed so as to be relatively large near the top and small near the primer layer.
(iii) Relatively, the particle number density is increased and the particle diameter is increased in the vicinity of the top, and the particle number density is decreased and the particle diameter is decreased in the vicinity of the primer layer.
Any one of the distribution forms is adopted. 7 and 8 correspond to the form (iii).

The distribution of the number density of the conductive particles in the convex pattern layer will be described in detail.
In the present invention, as conceptually shown in FIG. 14, the distribution of the conductive particles Cp inside the conductive convex pattern layer 3 is relatively sparse in the vicinity of the primer layer 2, It is preferable that the distribution is dense in the vicinity of the apex P.
That is, inside the convex pattern layer 3 (convex portion), the conductive particles Cp are not uniformly distributed uniformly, but the distribution of the conductive particles Cp is relatively higher than the top portion P (top portion) of the convex portion. An internal structure having a distribution in which the vicinity of the primer layer 2 is dense and the vicinity of the primer layer 2 far from the top P is sparse is preferable.
The term “dense” refers to the number density (volume density) of the conductive particles Cp in the unit volume as viewed from the number of particles. That is, the number density of the conductive particles Cp inside the convex portion is a distribution that is greater near the top portion P than near the primer layer 2.

The ratio of the number density of the conductive particles Cp at the top P of the convex pattern layer 3 when the number density of the conductive particles Cp in the region adjacent to the interface with the primer layer is 1 is large. This is advantageous in obtaining the effect of the distribution of the number density of the conductive particles.
On the other hand, as the ratio of the number density is increased, the manufacturing conditions are restricted and the difficulty in the realization is increased, and the physical limit of density increase due to the particle size of the conductive particles (close-packed structure is reduced). There is also a possibility of higher density than that). In consideration of these, as described above, when considering the material and average particle diameter of the conductive particles, the line width of the convex pattern layer, the manufacturing method, and good transparent antenna performance, the ratio of the number density, that is, [[ The number density of the conductive particles Cp at the top portion P / “number density of the conductive particles Cp in the region adjacent to the interface with the primer layer”] is preferably in the range of about 1.5 to 10.

The distribution state of the conductive particles Cp in the convex pattern layer 3 is determined to have no dependency on the direction in which the convex pattern layer 3 extends on the transparent substrate 1. That is, the cross-sectional view of the convex portion of the convex pattern layer 3 shown in FIG. 14 is a cross-sectional view of the main cut surface that is a plane orthogonal to the direction in which the convex portion extends and perpendicular to the sheet surface of the transparent substrate 1. Yes, the direction perpendicular to the paper surface is the direction in which the convex pattern layer extends (extending direction). In the extending direction, the number density of particles in a unit volume is the same as long as the position in the main cutting plane is the same. Is considered constant. This is because the convex pattern layer 3 is continuously manufactured by applying the same conductive resin composition to the intaglio by the method described later.
Therefore, the number density of the conductive particles Cp in such a unit volume is evaluated by the number density (area density) of the conductive particles Cp in the unit area on the main cut surface of the arbitrary convex pattern layer 3. I can do it.
That is, as shown in FIG. 14, in the main cut surface, if the distribution of the surface density of the conductive particles Cp is larger near the top P than the region adjacent to the interface of the primer layer 2, It may be determined that the volume density of the conductive particles Cp is also a distribution that is larger in the vicinity of the top P than in the vicinity of the primer layer 2.

Further, the distribution of the conductive particles in the convex pattern layer can also be measured by measuring the distribution in the thickness direction of the distance between the adjacent conductive particles in the convex pattern layer (hereinafter referred to as “particle interval”). Can be expressed. Here, as the layer in the thickness direction, the outermost layer (hereinafter referred to as “conductive particle interval of the outermost layer”) as a top formed by a conceptual line connecting conductive particles existing along the contour line of the conductive pattern layer. ), And the innermost layer (hereinafter, also referred to as “the innermost conductive particle interval”) formed by a concept line connecting conductive particles existing in the vicinity of the primer layer. It can be a layer. And measure the distance between the conductive particles in these layers, that is, the distance between the conductive particles in the outermost layer and obtain the average, and measure the distance between the conductive particles in the innermost layer and obtain the average. Can be used as an index of the distribution of the conductive particles in the conductive pattern layer. As the number of measurement data of the conductive particle interval in each layer, data of 3 or more, preferably about 10, is taken and averaged. The conductive particle interval is measured by taking a micrograph of the main cut surface and measuring the interval between two adjacent conductive particles.
Further, the distance between the conductive particles is the distance between the side edge portions in the conductive pattern layer, and the distance between the conductive particles in the outermost layer in the central portion whose width corresponds to w / 2 with the vertex as the center. Since the conductive particle interval of the innermost layer significantly represents the difference in the distribution of the conductive particles in the conductive pattern layer, these values can be used as the difference in the conductive particle interval.
As an average electroconductive particle space | interval which shows high electroconductivity, the range whose outermost layer is 0-0.5 micrometer and innermost layer is 0.5-3 micrometers is suitable.

In order to realize such a sparse or dense particle density difference, that is, to make the conductive particles Cp unevenly distributed on the top P (outermost layer) of the convex pattern layer, for example, as shown in FIG. A specific intaglio printing method is adopted, and the pressure contact force for press-bonding the transparent substrate 1 having the primer fluidized layer 2c formed thereon to the plate surface is strengthened, and the conductive composition 3c has a low viscosity and is in the intaglio recess. It is good to solidify after releasing from the plate surface without solidifying.
In addition, the specific gravity difference between the conductive particles Cp and the binder resin, the viscosity of the conductive composition 3c before solidification (resin material and resin amount, solvent amount, amount of other additives, shape of conductive particles, particle size distribution, content Etc.) and solidification (curing) conditions, etc., and these may be determined experimentally as appropriate.
Note that the specific gravity difference between the conductive particles Cp and the binder resin is usually the specific gravity of the conductive particles Cp that are metal particles> the specific gravity of the binder resin. ) In the same direction (downward) as the direction of gravity, the conductive composition layer 3c may be solidified.

The following can be mentioned as effects when there is a difference in density of conductive particles or a difference in conductive particle spacing between the vicinity of the top of the convex pattern layer and the interface of the primer layer as described above.
(I) Electrical contact between the conductive particles Cp is more easily performed when the number density is larger or the conductive particle interval is smaller. Therefore, when there is a sparse distribution or a difference in the distance between the conductive particles in the number density of the conductive particles Cp in this way, even if the average concentration of the conductive particles Cp in the convex pattern 3 is the same, the same number As compared with the case where the number density of the conductive particles Cp is uniformly distributed or the distance between the conductive particles is evenly distributed, the volume at the portion where the number density is large or where the distance between the conductive particles is small The decrease in resistivity contributes to a decrease in volume resistivity as a whole, and the conductivity performance is improved.
(ii) The adhesiveness between the convex pattern layer 3 and the primer layer 2 is improved by the small number density of the conductive particles Cp in the vicinity of the boundary with the primer layer 2 or the large interval between the conductive particles.
(iii) For example, when a transparent antenna is attached to a display screen of a mobile phone or the like, light incident from the transparent substrate 1 side (the lower side in FIG. 3 or FIG. 14) of the transparent antenna element 10 is convex. When the light is reflected at the interface between the patterned pattern layer 3 and the primer layer 2, the diffuse reflection component increases and the specular reflection component decreases. Therefore, it is possible to reduce a decrease in image contrast due to multiple reflection of image light incident from the image display device between the interface and the screen.
(iv) Further, when the transparent antenna element 10 is installed with the transparent substrate 1 side facing the observer side, the number density of the conductive particles Cp in the vicinity of the boundary with the primer layer 2 is small, The specular reflection component of the external light at the interface is reduced, and the whitening of the convex pattern layer 3 in the presence of the external light and the reduction in the contrast of the image due to this can be reduced. Furthermore, the convex pattern layer constituting the transparent antenna is preferable because it becomes inconspicuous in the presence of extraneous light.

In order to exhibit this effect more effectively, it is more preferable to select a polyhedral, spherical, or spheroid shape as the conductive particle shape rather than a scale shape. Since a surface close to a mirror surface is hardly formed on the primer layer side surface, it is preferable. In addition, when a scale-like material is adopted as the conductive particle shape, the orientation direction of the scale-like conductive particles in the vicinity of the primer layer side in the convex pattern layer (for example, the first of the scales) It is preferable to distribute the random surface (defined as the normal direction of a wide surface) in a random manner because specular reflection is reduced.
In addition, even when the conductive particle shape is a polyhedron shape, a spherical shape, or a spheroid shape, it is preferable in terms of reducing specular reflection light to make the orientation direction random.
At the same time, the conductive particles in the vicinity of the apex are densely gathered, the electrical contact between the particles is improved, the electric resistance is lowered, and the gain characteristic as a transparent antenna is improved.
Of course, such high-density conductive particles have a high visible light reflectance, but the conductive particles should be positioned on the side that is not in contact with the image observer's eyes (opposite to the observer). As a result, there is no worry about a decrease in image contrast or the like. When the conductive particle layer is installed and used so as to be positioned on the image observer side, the convex pattern layer surface may be subjected to blackening treatment or the like as necessary.
In addition, the structure in which particles are densely present near the top of the convex pattern layer is advantageous in that if this mesh is used as an element for a transparent antenna, the resistance value can be reduced and an antenna having a high gain can be obtained. have.

The density distribution of the conductive particles in the convex pattern layer is controlled. As shown in FIG. 6, the distribution is relatively sparse in the vicinity of the primer layer, and the vicinity of the top of the convex pattern layer ( In order to make it dense in the outermost layer), or in the vicinity of the primer layer (innermost layer), the orientation direction of the particles becomes messy, and the top of the convex pattern layer is oriented in parallel or substantially in parallel. For example, in the method for manufacturing a transparent antenna of the present invention using an intaglio printing method as described later (see FIG. 4), a recess on the upper surface of the conductive composition filled in the recess of the plate surface (reference numeral 6 in FIG. 4A). In addition, the pressure for pressing the fluidized primer layer 2c on the transparent substrate is set high, the viscosity of the conductive composition in the uncured state is set low, and the conductive composition Without solidifying the object in the intaglio recess , It is effective to allowed to solidify after the release from the plate surface.
In addition, as described above, it is experimentally determined and determined from various conditions that affect the density distribution and orientation state of the conductive particles.
Although content of the electroconductive particle in an electroconductive composition is arbitrarily selected according to the electroconductivity of an electroconductive particle or the form of particle | grains, for example, among 100 mass parts of solid content of an electroconductive composition, it is electroconductive. The particles can be contained in the range of 40 to 99 parts by mass, preferably 90 to 97 parts by mass. In the present specification, the average particle diameter refers to a value measured by a particle size distribution meter or TEM (transmission electron microscope) observation. In the case of an aspherical shape such as a polyhedral shape or a fibrous shape, the particle diameter is usually defined by the diameter of the circumscribed sphere, the diagonal length, or the side length of the longest side.

As the binder resin constituting the conductive composition, any of thermosetting resins, ionizing radiation curable resins, and thermoplastic resins can be used. In addition, when performing the below-mentioned electrical resistance reduction process, the water-insoluble resin which does not melt | dissolve with an acid or warm water is used. Examples of such a binder resin include thermosetting resins such as melamine resin, polyester-melamine resin, epoxy-melamine resin, phenol resin, polyimide resin, thermosetting acrylic resin, thermosetting polyurethane resin, thermosetting resin. Resin such as polyester resin can be exemplified, and as the ionizing radiation curable resin, the above-mentioned materials can be exemplified as the material for the primer layer, and these are used alone or in combination of two or more. Examples of the resin include resins such as thermoplastic polyester resin, polyvinyl butyral resin, thermoplastic acrylic resin, thermoplastic polyurethane resin, and vinyl chloride-vinyl acetate copolymer. These may be used alone or in combination of two. Mix and use above. In addition, when using a thermosetting resin, you may add a curing catalyst as needed. When using an ionizing radiation curable resin, a photopolymerization initiator may be added as necessary.
Further, in order to obtain fluidity suitable for filling the concave portion of the plate, these resins are usually used as a varnish dissolved in a solvent. There are no particular restrictions on the type of solvent used as the conductive paste, and it can be used by appropriately selecting from the solvents generally used in printing inks. However, it can inhibit stable curing of the primer layer 2 or can be a primer after curing. Those which do not swell, whiten or dissolve the layer are preferred. The content of the solvent is usually about 10 to 70% by mass, but it is preferably as small as possible within a range where necessary fluidity is obtained. In addition, when an ionizing radiation curable resin is used, a solvent is not necessarily required because it is inherently fluid.

  Also, in order to improve the fluidity and stability of the conductive composition, as long as the conductivity and adhesion to the primer layer are not adversely affected, a filler, a thickener, an antistatic agent, and a surfactant are appropriately used. Antioxidants, dispersants, anti-settling agents and the like may be added.

  FIG. 4 shows that the recess 6 of the conductive material composition 15 (3c) in the recess 64 of the intaglio plate surface 63 is filled with the uncured and fluid primer layer 2c, and the conductive material composition 15 (3c) It is a schematic diagram which shows the form to transfer. As shown in FIGS. 4C and 3, when the form of the cured primer layer 2 and the form of the conductive material layer 3 after the transfer process are observed, the conductive material layer 3 c of the primer layer 2 is transferred. The thickness TA of the portion A is larger than the thickness TB of the portion B where the conductive material layer 3c is not transferred. In the side edges 5 and 5 of the portion A having a large thickness, the conductive material layer 3 wraps around the portion B having a small thickness. In such a form, the primer layer 2 side of the transparent base material 1 on which the primer layer 2c retaining fluidity is formed and the concave portion 64 side after the resin filling step are crimped as shown in FIGS. 4 (A) and 4 (B). As a result, the flowable primer layer 2c is filled in the recesses 6 that are likely to be formed on the conductive material composition in the recesses 64, so that the form after transfer is a transparent group as shown in FIG. The thickness TA of the portion A where the conductive material layer 3 is formed in the primer layer 2 provided on the material 1 is larger than the thickness TB of the portion B where the conductive material layer 3 is not formed, Further, the side edges 5 and 5 of the portion A having a large thickness are in a form in which the conductive material layer 3 wraps around the portion B having a small thickness. That is, normally, the thickness TA of the primer layer in the portion A where the convex pattern layer is formed becomes thicker toward the center of the portion as shown in FIG. That is, in the cross section of the transparent antenna pattern portion (for example, FIG. 3), the cross-sectional shape of the primer layer 2 is a so-called bell such as a semicircle or semi-ellipse that is convex in a direction away from the transparent substrate 1. A so-called mountain shape such as a mold shape, a triangle shape, a trapezoidal shape, a pentagonal shape, or the like, or a similar shape thereto.

  In addition, in the transparent antenna element of the present invention, the interface between the primer layer and the convex pattern layer in the convex pattern layer forming portion is as shown in Patent Document 3, (a) the primer layer and the convex pattern layer (B) a cross-sectional configuration having a layer in which a component constituting the primer layer and a component constituting the convex pattern layer are mixed, and (c) ) It has a feature that it exhibits any one or two or more cross-sectional forms in which the component contained in the primer layer is present in the conductive composition constituting the convex pattern layer.

4 and 5 show a method of manufacturing the transparent antenna element 10 (see FIG. 2) of the present invention in which the convex pattern layer 3 is formed on one surface of the transparent substrate 1. As shown in FIG. 5, a transparent base material preparing step for preparing a transparent base material 1 that can maintain fluidity until cured and that has a primer layer 2 c to which a release agent is added is formed on one surface; After applying a conductive material composition 15 (3c) that forms a cured product having conductivity after curing to a plate-like or cylindrical plate surface 63 in which a recess corresponding to the shape pattern layer is formed, the inside of the recess Scraping off the conductive material composition adhering to the other and filling the concave portion 64 with the conductive material composition 15 (3c), the concave portion 64 side of the plate surface 63 after the filling step and the transparent substrate preparing step Pressure-bonding the primer layer 2c side of the transparent base material 1 so that the conductive material composition 15 (3c) and the primer layer 2c in the recess 64 are closely contacted with no gap, and the primer layer 2c is bonded after the pressure-bonding step. Primer curing process and primer A transfer step of transferring the conductive material composition 15 in the recess of the (3c) on the primer layer 2 by peeling the transparent substrate 1 from the printing plate 63 after the curing step,
After the transfer step, at least a curing step of forming the conductive layer 3 by curing the conductive composition layer 3c formed in a predetermined pattern on the primer layer 2 is provided.
In addition, hardening of this primer layer 2c and hardening of the electroconductive composition 3c can also be performed simultaneously.
In that case, the primer curing step and the curing step for forming the conductive layer are combined in one step.

(Electrical resistance reduction treatment process)
The conductive composition is transferred from the concave portion through the primer layer onto the transparent substrate to form the convex pattern layer 3, and then (i) treated in the presence of moisture and at a temperature higher than room temperature. Or (ii) by contacting with an acid, the volume resistivity of the convex pattern layer is lowered and the performance of the transparent antenna is improved. This phenomenon is observed particularly when the conductive particles are silver or particles containing silver. Hereinafter, this phenomenon is also referred to as an electrical resistance reduction treatment step. Unlike the so-called baking treatment, this electrical resistance reduction treatment step is not a long-time heat treatment that damages a general film substrate such as PET, and nano-sized particles known as printing inks for low-temperature baking. Instead of this dispersion liquid, it is possible to use a conductive ink having general properties including a binder such as a resin.
In the electrical resistance reduction treatment step in the presence of moisture at room temperature or higher in (i), after the transfer (intaglio printing) step, the transparent antenna is allowed to stand at a temperature higher than room temperature for an appropriate period of time in contact with moisture. To do. The conditions in the presence of moisture may be left in air containing water vapor, sprayed (sprayed) with water particles in the form of mist or raindrops, or immersed in liquid water. In the case of leaving in air containing water vapor, the relative humidity of the left air (atmosphere) is 70% RH or more, preferably 85% or more. The temperature in such a high temperature state (atmospheric temperature when left in air containing water vapor, and water temperature when immersed in water) is 30 ° C. or higher, preferably 60 ° C. or higher. However, if the temperature is too high, the resin binder and the transparent base material may be altered or changed.

The treatment time is 48 hours after the start of treatment, and the surface resistance value decreases with time. However, after 48 hours, the treatment time is substantially constant, so it is preferable that the treatment time be about 48 hours.
By such an electrical resistance reduction treatment step, the surface resistivity of the entire convex pattern layer is reduced to about 80 to 50% before treatment (the apparent volume resistivity is also about 80 to 50% before treatment). .
Further, although the volume resistivity is decreased regardless of the particle shape and size of the conductive composition and the type of the resin binder, the surface resistance after pattern formation is obtained by using the conductive paste according to the claims of the present invention. The value is smaller than when using a conductive paste other than those described, and the absolute value of the surface resistivity after processing can be reduced, and it can be reduced to 0.8Ω / □ or less after processing in general pattern design. It is. Moreover, also when forming the metal layer mentioned later by electroplating, a plating process speed | rate can be raised by lowering | hanging a surface resistance value by this process, and productivity improves.
The reason why the volume resistivity is reduced by the electrical resistance reduction process is not yet elucidated at this time. For example, silver is used as the conductive particles, and the state change of the silver particles before and after the treatment is measured by SEM (scanning electron microscope). When observed, the change in the shape of silver particles, partial fusion, a decrease in the distance between particles, and the like are observed, which are presumed to be the direct cause of volume resistivity reduction.

Considering the reason why the volume resistivity is reduced by the electrical resistance reduction treatment process, FIG. 6 is an SEM photograph of a cross section of the untreated convex pattern layer obtained by using silver particles. Although silver particles have large and small particle diameters, they are generally independent, and a boundary between both particles is recognized at a contact portion between adjacent particles. Further, a plurality of particles are not connected and integrated (connected or also connected). On the other hand, FIG. 7 is a SEM photograph of a cross section processed for 48 hours at 80 ° C. × 90 RH%. Among adjacent particles, the boundary of the contact portion between adjacent particles disappears, and the adjacent particles It can be seen that there are things that are fused and integrated. Then, it is observed that a plurality of particles are fused to form a connected path, and the path is shown by a solid line in FIG. The connection path of the plurality of particles is linear, bent, and / or curved, and there is one or more paths that are connected from one side end to another side end. In view of this, it is considered particularly desirable. In addition, a binder resin is present in a void portion where the conductive particles are not fused or in contact with each other, and contributes to bonding between the particles.
In addition, in the treatment with an acid described later, in observation with an SEM photograph, the connecting portion does not reach from one side end portion to the other side end portion, but the volume resistivity of 0.3Ω / □ is Has been achieved.

For this reason, the connection in which a plurality of particles are fused (also referred to as “cluster”) is preferably a fusion part (cluster) whose length is continuous to about 1/2 of the line width of the convex pattern layer. For example, although fusion cannot always be confirmed by a cross-sectional photograph of the part, it is assumed that there is a high probability that a path connected from one side end part to another side end part exists in the part of the other cross section. It is considered that the volume resistivity can be reduced. Note that the surface resistance increases when a pattern that has not been subjected to the electrical resistance reduction treatment is subjected to a wiping test with alcohol, but the phenomenon that the pattern after the implementation hardly changes is observed. It is presumed that a bond is formed, and it is thought that the cluster formation as described above is supported.
The reason why fusion between particles occurs due to high-temperature moist heat treatment or treatment with acid and the volume resistivity decreases is as follows. Promotion of metal diffusion between silver particles by washing the particle surface, resin with moisture or acid Considering shrinkage of the binder, reduction of the solvent component, or solidification again in such a form that the dissolved metal envelops between the surfaces of adjacent particles or fills the gaps between the particles. However, the true reason has not been confirmed yet.
It has been confirmed that the volume resistivity is not reduced simply by heat treatment at 80 ° C. It has also been confirmed that the volume resistivity decrease rate is small unless the substrate is sufficiently dried after the acid treatment.

Next, treatment with an acid will be described. In the present invention, the treatment with acid means that the conductive composition is transferred from the inside of the intaglio recess to the transparent substrate via the primer layer to form a convex pattern layer, and then brought into contact with the acid to form a convex shape. This refers to a process for reducing the volume resistivity of the pattern layer.
The acid in the present invention is not particularly limited, and can be selected from various inorganic acids and organic acids. Examples of inorganic acids include hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid and the like. Examples of the organic acid include acetic acid, citric acid, succinic acid, propionic acid, lactic acid, and benzenesulfonic acid. These may be strong acids or weak acids. Preferred are acetic acid, hydrochloric acid, sulfuric acid, and aqueous solutions thereof, more preferred are hydrochloric acid, sulfuric acid, and aqueous solutions thereof, and particularly preferred in the case of silver conductive particles are hydrochloric acid and aqueous solutions thereof.

  The treatment time with the acid is sufficient for several minutes or less, and even if the treatment time is made longer, the effect of improving the conductivity may not be increased or the effect of improving the conductivity may be deteriorated. The treatment time with the acid is preferably 15 seconds to 60 minutes, more preferably 15 seconds to 30 minutes, still more preferably 15 seconds to 2 minutes, and particularly preferably 15 seconds to 1 minute.

  A normal temperature is sufficient for the treatment temperature of the acid. When processing at high temperature, acid vapor is generated and the surrounding metal equipment is deteriorated, or when a thermoplastic resin film is used as the transparent substrate, the transparent substrate is whitened, and the transparency Is unfavorable because it may damage the process. A preferable treatment temperature is 40 ° C. or lower, more preferably 30 ° C. or lower, and further preferably 25 ° C. or lower.

  The method of treating with an acid is not particularly limited. For example, the convex pattern layer is immersed in an acid or an acid solution, an acid or an acid solution is applied on the convex pattern layer, an acid, A method of applying an acid solution vapor to the convex pattern layer or spraying (spraying) a mist or raindrop acid or acid solution is used. Among these, there is a method of bringing the convex pattern layer into contact with the acid liquid, such as immersing the convex pattern layer in an acid solution, or applying an acid or an acid solution on the convex pattern layer. It is preferable because of its excellent conductivity improving effect. That is, as the acid treatment conditions, it is preferable to immerse the convex pattern layer in an acid solution at a temperature of 40 ° C. or lower, or to apply an acid or an acid solution on the convex pattern layer. .

When an acid solution is used, the acid concentration is preferably 10 mol / L or less, more preferably 5 mol / L or less, and further preferably 1 mol / L or less. If the concentration of the acid solution is high, the workability may decrease and the productivity may deteriorate, or if a thermoplastic resin film is used as the transparent substrate, the transparent substrate will be whitened to improve transparency. Since it may damage, it is not preferable. In addition, even when the acid concentration is too low, the effect of the treatment with the acid cannot be obtained, so that it is preferably 0.05 mol / L or more, more preferably 0.1 mol / L or more.
In addition, when using the solution of an acid, since there is a concern about the bad influence by the residue of an acid, it rinses after a process and a drying process is needed. When hot water or steam is used, the rinsing step can be omitted.
As the treatment with an acid, in addition to making contact with one kind of acid only once, it is possible to make contact with two or more kinds of acids once in total, twice or more. For example, when dipped in hydrochloric acid first and then dipped in citric acid, the effect of reducing electrical resistance is greater than when dipped only in hydrochloric acid and dipped only in citric acid.
Further, only one of the acid treatment (above (i)) and the treatment in the presence of water at room temperature or higher (above (ii)) may be used, but both treatments may be performed sequentially. For example, first, when dipped in acid and then dipped in water at room temperature or higher, the effect of reducing electrical resistance is greater than that of simply dipping in acid or dipping in water at room temperature or higher.

(Convex pattern layer)
In the form in which the convex pattern layer has a mesh shape in particular (this form is also referred to as a conductive mesh (pattern layer)), a line portion composed of two or more parallel line groups having different directions intersects each other, An opening (pattern non-formed part) is formed surrounded by these line parts. Even when three or more parallel line groups (line parts) cross, the basic design points and effects are the same. I will explain. Further, the crossing angle of each line group, that is, the crossing angle θ between the first direction line part and the second direction line part can be selected from the range of 0 ° <θ <180 °, but θ = 90 ° is usually widely used. It has been.
In the mesh shape as the element for a transparent antenna of the present invention, the light transmittance including the transparent substrate, the primer layer, the mesh opening, and the protective layer is preferably 70% or more, and preferably 80% or more. More preferred. The aperture ratio of the mesh is also determined from the above-mentioned range of 50 to 95% in consideration of the light transmittance.

(Metal layer (plating layer))
The transparent antenna element according to the present invention is a metal made of a low resistivity metal in order to further improve the conductivity when the convex mesh pattern layer 3 made of a conductive composition alone is insufficient for the desired conductivity. The layer 4 can be formed as needed, and is formed on the convex pattern layer 3 by plating. As plating methods, there are methods such as electrolytic plating and electroless plating, but electroplating can increase the plating rate several times by increasing the amount of current compared to electroless plating, which significantly improves productivity. This is preferable.
In the case of electrolytic plating, power is supplied to the convex pattern layer 3 from an electrode such as an energizing roll brought into contact with the surface on which the convex pattern layer 3 is formed. The convex pattern layer 3 can be electroplated. Since it has conductivity (for example, 100Ω / □ or less), electrolytic plating can be performed without any problem. The material constituting the metal layer is a low resistivity metal, that is, a metal having high conductivity, and a metal that can be easily plated. Specific examples include copper, silver, gold, chromium, nickel and the like. In addition, the film thickness of such a metal layer shall be about 0.5-5 micrometers, and normally shall be 1-3 micrometers.
Since the metal layer 4 generally has a volume resistivity that is one digit or more smaller than that of the convex pattern layer 3, the amount of the conductive material required is larger than when the convex pattern layer alone secures the transparent antenna property. There is an advantage that can be reduced.

  In addition, after forming a metal (plating) layer, you may blacken the metal layer or provide a protective layer as needed. Examples of the blackening treatment include blackening nickel plating and copper-cobalt alloy plating, but are not necessarily limited to these treatments. The protective layer is a layer that covers and protects the surface of the convex pattern layer. For example, it can be formed using an acrylic ultraviolet curable resin. When the metal used for the convex pattern layer or metal layer is a metal that easily rusts, such as copper, it is preferable to perform a rust prevention treatment, and a general rust prevention agent such as a chromate treatment agent can be used. May also serve as a blackening treatment or protective layer formation.

[Transparent antenna]
A transparent antenna has a length, width, and shape (conductivity) designed as an antenna, depending on the purpose of transmission, reception, transmission / reception, etc., and the frequency and electric field strength of an electromagnetic wave used. The outer contour shape of the convex pattern layer made of the composition is determined, and the feeding point of the transmission / reception circuit is connected to the transparent antenna element having the predetermined shape, so that the function as an antenna can be exhibited.
As a type of antenna to which the transparent antenna of the present invention can be applied, a dipole antenna or a monopole antenna in which two conductive patterns (elements) are symmetrically provided at a feeding point can be cited.
A dipole antenna has a theoretical gain of 2.14 dBi (sometimes referred to as 2.15 dBi), and the transparent antenna of the present invention is also targeted for a gain comparable to that of a dipole antenna.

FIG. 9 schematically shows a case where a half-wavelength (λ / 2) dipole antenna is configured using a conductive mesh as the transparent antenna element of the present invention. The half-wavelength dipole antenna shown in the figure is a transmission / reception feeding point 20 (corresponding to an AC power source that supplies a signal to be transmitted as an AC current (voltage), and includes an oscillation circuit, a modulation circuit, an amplification circuit, and the like). Symmetrical transparent antenna elements (elements; hereinafter also simply referred to as elements) 21 and 22 made of conductive mesh are connected via a feeder line. The lengths L ₁ and L ₂ of the elements 21 and 22 made of conductive mesh are made to correspond to the wavelength of 123 mm converted from the frequency when the frequency of the electromagnetic wave to be transmitted or received is 2.45 GHz (2450 MHz) as an example. 30 mm each. The heights H ₁ and H ₂ of the conductive mesh elements 21 and 22 were 40 mm.
The element lengths L ₁ and L ₂ are approximately λ / 4 (= 30.8 mm) when the wavelength λ (= 123 mm) corresponding to the frequency of 2.45 GHz, and the total length of the element (L ₁ + L ₂ ). Is approximately λ / 2 (= 61.5 mm).
These transparent antenna elements 21 and 22 are composed of a mesh-like convex pattern layer made of a conductive composition (and other transparent base materials and the like are also attached), and the outer contour shape in plan view thereof is a predetermined antenna. Make a pattern (in this case a rectangle).
When the transparent 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 feeding point 20 in FIG. Is done.

FIG. 10 shows a case where the element 31 is provided with a plurality of slits 32 having a length L ′ in a conductive mesh portion having a length L to ensure the required antenna length by meandering. In this way, the required antenna length can be ensured even when the installation space or part is limited. In this case, the meandering element 31 has a length along the meandering pattern of the developed element 31 by slitting, so that the length of the received radio wave, for example, the UHF wave λ is approximately λ / 4. Is set to be Therefore, the outer contour dimension (vertical and horizontal) of the meandering antenna pattern 31 is compressed more than λ / 4.
FIG. 11 shows a state where a transparent antenna composed of meandering elements 31 and 31 ′ is installed on the display unit 101 of the mobile phone 100. In the drawing, the left meandering element 31 ′ is the left and right object of the right meandering element 31. A feeding point (not shown) is provided on the housing side outside the display unit 101.
In addition, you may form the frame part which consists of conductors in the upper end part of a transparent antenna element, a lower end part, a left end part, or a right end part, or a 4-circumferential end part as needed. When connecting a ground wire, a director, a reflector, and a feeder line to the transparent antenna element, these ground wires and the like are connected through the frame portion. As the conductor of the frame portion, the same conductive composition as that of the convex pattern layer may be used, or another conductive composition, metal, or the like may be used. The frame is usually a layer without an opening.

  FIG. 12 shows a case where the transparent antenna of the present invention is used as a λ / 2 dipole antenna in the rear window of an automobile.

  Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited to these examples.

Example 1
[Preparation of intaglio]
First, as the intaglio roll 62, an intaglio roll (intaglio cylinder) having a square lattice mesh pattern with a line width of 18 μm and a line pitch of 270 μm and a target plate depth of 10 μm was prepared.
In addition, the intaglio roll uses a cylinder in which a copper layer is formed on the surface of an iron hollow cylinder (iron core) as a material, and after forming a concave portion of the mesh pattern on the surface of the copper layer, the surface is chrome plated. Was used.

[Preparation of transparent substrate]
Next, as the transparent substrate 1, a long roll wound biaxially stretched transparent polyethylene terephthalate (PET) film having a width of 1000 mm and a thickness of 100 μm subjected to an easy adhesion treatment on one side was used. In addition, an uncured liquid primer composition comprising a urethane acrylate ultraviolet curable resin composition to which 1% by mass of stearic acid ester was added as a release agent was prepared. The PET film set in the supply unit was fed out, and the primer composition was coated on the easy-adhesion treated surface of the PET film to a thickness of 14 μm by a diagonal gravure reverse roll coating method to prepare a transparent substrate.

[Manufacture of transparent antenna elements (conductive mesh)]
A transparent antenna element was manufactured by the apparatus shown in FIG. First, using the intaglio roll 62 prepared above, a silver paste ink (consisting of a substantially spherical shape and having a particle size of 0.1) which is an uncured and fluid conductive composition 15 (3c) filled in a filling container 68. 93 parts by mass of silver particles having an average particle diameter of 1 μm are dispersed in 4 parts by mass in an acrylic binder resin in a mixed system of particles having a particle diameter of ˜0.5 μm and particles having a particle diameter of 1 to 3 μm, and diluted with a mixed solvent of methyl ethyl ketone and toluene. ) Is coated on the plate portion by the pick-up roll 61, and the plate surface 63 from which the excess ink is scraped off by the doctor blade 65 and the primer layer side of the transparent substrate (PET film) on which the primer layer is formed are pressure-bonded by the nip roll 66. Next, between the ultraviolet irradiation zone equipped with a high-pressure mercury lamp (not shown, but above the intaglio roll 62 at the site indicated as “UV zone” in FIG. 5) While traveling, the UV curable resin of the primer layer is cured and then released from the plate surface 63 via the nip roll 67, and the plate pattern on the plate cylinder surface is transferred onto the PET film via the primer layer. Thus, a transparent antenna element having a conductive mesh portion was produced by drying and curing at 80 ° C. with the convex pattern layer 3 having a mesh shape. The transparent substrate was an endless roll, and was printed by a roll-to-roll method at a printing speed of 10 m / min.
Here, the roll-to-roll method refers to a processing method in which a roll (winding) is unwound and subjected to a predetermined processing, and then wound around the roll again.

The thickness of the convex pattern layer after printing (measured with reference to the primer layer in the non-mesh portion) is 9 μm, and the transition rate calculated by the ratio of the plate depth to the printing thickness is (mesh pattern thickness 9 μm / plate depth). 10 μm) × 100 = 90%, but in reality, there is a volume shrinkage due to solvent drying of the silver paste ink, so it is estimated that the transition is almost 100%.
Furthermore, the form of the interface between the primer layer 2 and the convex pattern layer 3 is such that the thickness TA of the primer layer 2 immediately below the convex pattern layer 3 is the thickness TB at the non-convex pattern layer forming portion. The interface protruded thicker than that, and the interface was alternately arranged in a non-linear manner.
As a result of magnifying and observing such an intricate structure with an electron microscope, the conductive particles (silver particles) in the convex pattern layer are randomly distributed up and down at the interface with the primer layer 2 to form the interface. Admitted to do. The distribution of the conductive particles should be denser and denser as it goes to the top of the convex pattern layer, and conversely becomes coarser as it goes to the primer layer side. Admitted.
Furthermore, a mixed region where the components of both layers were mixed was also observed in the vicinity of the interface.
In the main cutting plane perpendicular to the mesh wire flange, the number of conductive particles per unit cross-sectional area is 1 / μm ^{2 on} average in the portion adjacent to the primer layer, and 3 / μm ^{2 on} average near the top. Met.

The convex pattern layer 3 after curing of the conductive composition has an electron micrograph of its cross section shown in FIG. 6, and the individual silver fine particles are almost independent. From this cross sectional photograph, the convex pattern layer 3 As a result of measuring the distance between the conductive particles at the top and the distance between the conductive particles in the vicinity of the interface with the primer layer and calculating the average of each, the average distance between the conductive particles at the top is 0.5 μm, The average distance between the conductive particles in the vicinity of the interface was 1.5 μm.
That is, the distribution of the conductive particles should be denser as it goes to the top of the convex pattern layer, and vice versa. Was recognized. The surface resistivity was 1.2Ω / □.

Next, the transparent antenna element was left in an atmosphere at an air temperature of 80 ° C. and a relative humidity of 90% for 48 hours to perform an electrical resistance reduction treatment step, and then a room temperature atmosphere (at an air temperature of 23 ° C. and a relative humidity of 50%). ).
The conductive particles of the convex pattern layer after the electrical resistance reduction treatment are those in which the interface disappears between adjacent conductive particles as shown in a cross-sectional electron micrograph of FIG. It was confirmed that when the fused portions are connected, the continuous pattern is continuous over the entire width of the convex pattern layer as shown by the broken line in FIG.

Next, the surface (electrical) resistance of the convex pattern layer of the obtained transparent antenna element was measured.
The measurement was performed in a room temperature atmosphere (temperature 23 ° C., relative humidity 50%). The surface resistivity was 0.45Ω / □.
Next, a copper layer was applied to the surface of the convex pattern layer of the obtained transparent antenna element so as to have a thickness of 2 μm by electrolytic plating using a copper sulfate bath. The surface (electrical) resistance after copper plating was 0.1Ω / □.

[Performance evaluation as a transparent antenna]
The transparent antenna element obtained in the above embodiment was cut into L ₁ = L ₂ = 30 mm and h ₁ = h ₂ = 40 mm in the shape of λ / 2 dipole antenna shown in FIG. After attaching the double-sided adhesive tape, it was connected to the feeding point 20, and the frequency characteristics and directivity were measured by the following method. The light transmittance of this transparent antenna element was 80%.
(Measurement method of antenna characteristics)
As shown in FIG. 13, in a anechoic chamber equipped with a radio wave absorber, a transparent antenna sample is attached at a height of 1,5 m to a support made of foamed polystyrene installed on a rotary table,
Using this as the transmitting antenna, using a method of measuring with a standard antenna (made of stainless steel) on the receiving side installed at a height of 1.5 m at a distance of 3 m from this, measure the gain in the 2300 MHz to 2600 MHz band, Further, the rotating table was rotated, and the directivity in the direction from 0 to 360 degrees in the horizontal plane at 2450 MHz (2.45 GHz) was measured.
(Measurement result)
As a result of measurement by the above method, the gain was equivalent to that of the standard dipole antenna, and the directivity was equivalent to that of the standard dipole antenna, which was sufficiently practical.

Example 2
[Preparation of intaglio]
As the intaglio roll 62, an intaglio roll having a square lattice mesh pattern with a line width of 20 μm and a line pitch of 270 μm and a target plate depth of 10 μm was prepared.

[Preparation of transparent substrate]
As in Example 1, a transparent substrate was prepared by coating the primer composition 2c on the easy-adhesion treated surface of the PET film to a thickness of 14 μm by the oblique gravure reverse roll coating method.

[Manufacture of transparent antenna elements (conductive mesh)]
In FIG. 5, except that the plate pattern line width is 20 μm, the same intaglio roll as in Example 1 was used, and the printing speed of 10 m / min was applied to the same transparent substrate as in Example 1 in the same manner as in Example 1. Printing was performed by a roll-to-roll method in min.
The interface form between the primer layer and the conductive layer had a structure in which the layers were interleaved in a non-linear manner. The surface resistivity after printing was 1.2Ω / □.
Next, after printing, the transparent antenna element is left in an atmosphere at an air temperature of 80 ° C. and a relative humidity of 90% for 48 hours to perform an electrical resistance reduction treatment process, and then a room temperature atmosphere (at an air temperature of 23 ° C. and a relative humidity). 50%), and the surface (electrical) resistance of the convex pattern layer of the transparent antenna element was measured. The surface resistivity was 0.45Ω / □.
Next, a copper layer was applied to the surface of the convex pattern layer of the obtained transparent antenna element so as to have a thickness of 2 μm by electrolytic plating using a copper sulfate bath. The surface (electrical) resistance after copper plating was 0.1Ω / □.

[Performance evaluation as a transparent antenna]
The transparent antenna element obtained in Example 2 above was cut into the shape of a λ / 2 dipole antenna shown in FIG. 15 and L ₃ = L ₄ = 41.0 mm, h ₃ = h ₄ = 6 mm, and these were cut into a glass substrate. A transparent double-sided pressure-sensitive adhesive tape was affixed to the power supply point 20 via an electrode pad pad, and frequency characteristics and directivity were measured by the following method. The light transmittance of this transparent antenna element was 80%.
(Measurement method of antenna characteristics)
The gain in the 2300 MHz to 2600 MHz band is measured by the same measurement method as in Example 1, and the turntable is rotated, and the directivity in the direction of rotation angle 0 to 360 degrees in the horizontal plane at 2450 MHz (2.45 GHz) is obtained. It was measured.
(Measurement result)
As a result of measurement by the above method, the gain was equivalent to that of the standard dipole antenna, and the directivity was equivalent to that of the standard dipole antenna, which was sufficiently practical.

Comparative Example 1
In Example 2, the silver paste ink is composed of a silver powder having an average particle diameter of 1 to 5 μm as a conductive powder, a thermoplastic acrylic resin as a binder resin, and a conductive material composition having a solid content of about 88.5%. By using silk screen printing, a mesh having the same dimensions as in Example 2, that is, a square lattice mesh pattern having a line width of 20 μm and a line pitch of 270 μm and a thickness of 10 μm was produced.
When the cross section of the convex pattern layer 3 after curing of the conductive composition was observed with an electron microscope, the individual silver fine particles were almost independent, the distance between the conductive particles at the top of the convex pattern layer 3, and As a result of measuring the distance between the conductive particles in the vicinity of the interface with the transparent substrate and obtaining the average of both, the average distance between the conductive particles at the top and the average distance between the conductive particles in the vicinity of the interface with the transparent substrate are both It was 1.0 μm.
That is, the distribution of the conductive particles was found to be distributed at a uniform particle number density both at the top of the convex pattern layer and in the vicinity of the transparent substrate side interface. In addition, there are some places where adjacent particles are in contact with each other, but a boundary was observed between adjacent particles.
When the surface resistivity of this transparent antenna element was measured, the surface resistance after release release curing (printing finished) was 5 Ω / □, and the surface resistance was reduced by the same wet heat environment static treatment as in Examples 1 and 2. Although it decreased to 2.5Ω / □, it did not reach 0.4Ω / □.

[Measurement results of antenna characteristics]
As a result of measurement using the same method as in the above example, the gain was about 30% of the standard dipole antenna, and the directivity was insufficient as compared with the standard dipole antenna.

Since the transparent antenna element of the present invention has both transparency and transmission / reception functions, it can be used for various transparent antennas.
The transparent antenna of the present invention can be used by being attached to a site where transparency is required. In particular, it can be attached to the front of the display of mobile communication devices such as mobile phones and used for receiving terrestrial and satellite broadcasts.
It can also be used to receive radio waves such as GPS satellite position information radio waves, televisions, radios, and vehicle radios by attaching to window glass of automobiles, buses, trucks, railway vehicles, vehicles of new transportation systems, and the like. It can also be used by attaching to the glass of the cabin of various construction machines such as excavators and cranes.
Furthermore, it can be used as a transparent antenna for building windows for receiving terrestrial waves and satellite broadcasts, or for transmitting and receiving radio waves of alarm systems, by being attached to window glass in houses and various buildings and partitions.
Alternatively, it can be attached to various products and used for distribution inventory management, anti-theft management, etc.

1 transparent substrate 2 primer layer (2c: uncured primer layer)
3 Convex pattern layer (3c: conductive material composition layer)
DESCRIPTION OF SYMBOLS 4 Metal layer 5 Side edge 6 Recess 7 Transparent antenna pattern part 8 Ground part 9 Protective layer 10 Element for transparent antenna 11 Interface between primer layer and convex pattern layer 15 Conductive material composition 20 Feeding point 21, 22 For transparent antenna Element (Element)
31, 31 'Transparent antenna element (element)
32 Slit 40, 41, 42 Element for transparent antenna (element)
61 Pickup Roll 62 Intaglio Roll 63 Plate Surface 64 Recess 65 Doctor Blade 66 Nip Roll 67 Nip Roll 68 Filling Container 100 Mobile Phone 101 Display A A portion where the conductive material layer is formed TA A thickness B A conductive material layer is formed No part TB B thickness Cp Conductive particle pad Electrode pad R Binder resin

Claims (3)

Transmission / reception to / from a transparent antenna element having a transparent substrate, a primer layer formed on the transparent substrate, and a convex pattern layer made of a conductive composition formed in a predetermined pattern on the primer layer A transparent antenna with a circuit feed point connected to it,
In the transparent antenna element, a thickness of a portion of the primer layer where the convex pattern layer is formed is thicker than a thickness of a portion where the convex pattern layer is not formed, and the conductive composition The object comprises conductive particles and a binder resin, and the distribution of the conductive particles in the convex pattern layer is relatively sparse in the vicinity of the primer layer, and the convex pattern layer A transparent antenna characterized by being dense in the vicinity of the top . Transmission / reception to / from a transparent antenna element having a transparent substrate, a primer layer formed on the transparent substrate, and a convex pattern layer made of a conductive composition formed in a predetermined pattern on the primer layer A transparent antenna with a circuit feed point connected to it,
In the transparent antenna element, a thickness of a portion of the primer layer where the convex pattern layer is formed is thicker than a thickness of a portion where the convex pattern layer is not formed, and the conductive composition The object comprises conductive particles and a binder resin, and the interval between the conductive particles in the convex pattern layer is relatively large in the vicinity of the primer layer, and in the vicinity of the top of the convex pattern layer. A transparent antenna characterized by being small. 2. The transparent antenna element according to claim 1, wherein in the observation with an electron micrograph, the conductive particles in the cross section of the convex pattern layer include those in which a plurality of conductive particles are partially fused. 2. The transparent antenna according to 2.