JP2011253852A - Electromagnetic wave shield material, complex filter and image display device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electromagnetic wave shield material which has a large conductivity in spite of having a conductive pattern layer formed from a conductive ink, and which is reduced in reflection of external light from the side of a transparent base, and has an untinted adhesive layer made of acrylic resin on the side of the conductive pattern layer.SOLUTION: An electromagnetic wave shield material includes: a transparent base; a primer layer formed on the transparent base; a conductive pattern layer formed on the primer layer and having a given pattern; and an adhesive layer made of a carboxyl group-containing acrylic resin and stacked on the side where the conductive pattern layer is formed. The conductive pattern layer contains metal particles and a binder resin. The distribution of the metal particles in the conductive pattern layer is relatively rough near the primer layer and dense near the top of the conductive pattern layer. The adhesive layer made of carboxyl group-containing acrylic resin contains 1H-benzotriazol.

Description

  The present invention relates to an electromagnetic wave shielding material, a composite filter, and an image display device using the same, which are disposed on the front surface of an image display device (display).

As an image display device (also referred to as a display device) such as a monitor of a television or a personal computer, for example, a cathode ray tube (CRT) display device, a liquid crystal display device (LCD), a plasma display device (PDP), an electroluminescent (EL) display Devices and the like are known. Among these display devices, plasma display devices that are attracting attention in the field of large-screen display devices use plasma discharge for light emission. Therefore, unnecessary electromagnetic waves in the 30 MHz to 1 GHz band leak to the outside and other devices ( For example, remote control devices, information processing apparatuses, etc.) may be affected. Therefore, it is common to provide a film-like electromagnetic shielding material for shielding electromagnetic waves that transmit and leak visible light on the front side (observer side) of the plasma display panel used in the plasma display device.
In the specification of the present application, “electromagnetic wave” means an electromagnetic wave having a frequency in the kHz to GHz band (so-called radio wave) centered on a frequency band of 30 MHz to 1 GHz. Higher frequency infrared rays, visible rays, ultraviolet rays, etc. are referred to as infrared rays, visible rays, ultraviolet rays, etc., respectively.

Conventionally, as a front filter of a plasma display, for example, a mesh-like metal thin film is formed on a transparent substrate by sputtering, electrolytic plating, and pattern etching on a transparent substrate, as described in Patent Document 1, for example. A composite filter in which an electromagnetic wave shielding filter obtained by laminating an acrylic resin-based pressure-sensitive adhesive layer and an optical filter such as an antireflection filter are further laminated thereon has been used.
However, since this electromagnetic wave shielding filter (electromagnetic wave shielding material) creates a mesh shape by etching, many materials are thrown away and it is difficult to reduce the cost.

On the other hand, Patent Document 2 discloses an electromagnetic wave shielding material with reduced cost and improved productivity by printing a conductive ink on a transparent substrate on a transparent substrate by a specific printing method. A composite filter is described that is bonded to an optical filter via an acrylic resin adhesive layer on the mesh pattern side.
This specific printing method is to press the conductive ink composition filled in the recesses of the intaglio plate with a transparent substrate made of an ultraviolet curable resin and having a primer layer that can maintain fluidity until cured. Through the pressure-bonding process that adheres the primer layer and the conductive ink in the recess without gaps, the primer layer is cured, and the transparent substrate is peeled off from the plate surface to cure most of the conductive ink composition in the recess. Thus, an electromagnetic wave shielding material that is transferred onto the primer layer and that does not cause defects such as pattern disconnection, shape failure, insufficient transfer rate, and low adhesion due to poor transfer of the conductive ink composition can be obtained.

JP 2007-36107 A WO2008 / 149969 pamphlet

However, the electromagnetic wave shielding material by the method of Patent Document 2 and the composite filter using the same also have the following problems.
(I) The conductivity (electromagnetic wave shielding property) is lower than that of an electromagnetic wave shielding material in which a metal thin film mesh is formed.
(Ii) Either the front or back side of the electromagnetic wave shielding material has a metallic luster of the mesh pattern, and reflects external light to reduce the contrast of the image, or reflects image light to reduce the image contrast. This is particularly a problem because the substrate side cannot be treated with blackening plating or the like.
(Iii) In the acrylic resin of the pressure-sensitive adhesive layer, the carboxyl group contained for improving the adhesion with the metal-containing layer reacts with the metal particles on the surface of the conductive pattern layer, and the metal rusts and changes color. Along with this, there is a problem that the pressure-sensitive adhesive changes color and the pressure-sensitive adhesive layer is colored.
An object of this invention is to provide the electromagnetic wave shielding material which solved these subjects, and the composite filter using the same.

As a result of diligent studies to solve the above problems, it has a primer layer formed on a transparent substrate, preferably made of an ultraviolet curable resin, and a conductive pattern layer formed in a predetermined pattern on the primer layer. In the electromagnetic wave shielding material, the distribution of the metal particles in the conductive pattern layer is configured so that the distribution is relatively sparse in the vicinity of the primer layer and is close in the vicinity of the top of the conductive pattern, or adjacent thereto. The interval between the metal particles is relatively large in the vicinity of the primer layer and small in the vicinity of the top of the conductive pattern layer, and a specific distance is set in the acrylic resin pressure-sensitive adhesive layer. It has been found that it can be solved by containing an antioxidant. The present invention has been completed based on such findings.
That is, the present invention
(1) It has a transparent substrate, a primer layer formed on the transparent substrate, and a conductive pattern layer formed in a predetermined pattern on the primer layer, and carboxyl is formed on the conductive pattern layer forming side. An electromagnetic wave shielding material formed by laminating a pressure-sensitive adhesive layer made of a group-containing acrylic resin, wherein the conductive pattern layer comprises metal particles and a binder resin, and the distribution of the metal particles in the conductive pattern layer is The pressure-sensitive adhesive layer is relatively sparse in the vicinity of the primer layer, dense in the vicinity of the top of the conductive pattern layer, and made of a carboxyl group-containing acrylic resin, and contains 1H-benzotriazole. An electromagnetic shielding material characterized by
(2) It has a transparent substrate, a primer layer formed on the transparent substrate, and a conductive pattern layer formed in a predetermined pattern on the primer layer, and carboxyl is formed on the conductive pattern layer forming side. An electromagnetic wave shielding material formed by laminating a pressure-sensitive adhesive layer comprising a group-containing acrylic resin, wherein the conductive pattern layer comprises metal particles and a binder resin, and the adjacent metal particles in the conductive pattern layer are adjacent to each other. Is relatively large in the vicinity of the primer layer and small in the vicinity of the top of the conductive pattern layer, and the pressure-sensitive adhesive layer made of a carboxyl group-containing acrylic resin contains 1H-benzotriazole. Electromagnetic shielding material, characterized by
(3) The composite filter formed by laminating an optical functional layer on one or both sides of the electromagnetic shielding material of (1) or (2), and (4) the composite filter of (3) is provided on the front side of the display panel. Installed image display device,
Is to provide.

In the electromagnetic wave shielding material obtained by the present invention, the distribution of the metal particles in the conductive pattern layer is relatively sparse in the vicinity of the primer layer and dense in the vicinity of the top of the conductive pattern layer. Alternatively, since the interval between the adjacent metal particles is relatively large in the vicinity of the primer layer and small in the vicinity of the top of the conductive pattern layer, the distance between the top of the conductive pattern layer is increased. Since the electrical contact between the metal particles is intensively ensured, there is an effect of exhibiting high electromagnetic shielding properties despite the limited amount of metal particles added.
In addition, the distribution of the metal particles in the vicinity of the primer layer is large or the distance between adjacent metal particles is large. Therefore, even when the transparent substrate side is directed outward (observer side), the light reflection of the conductive pattern layer Is reduced and the image contrast is good.
Furthermore, since the pressure-sensitive adhesive layer contains 1H-benzotriazole, coloring of the conductive pattern layer is also prevented.

It is typical sectional drawing which shows 1 form of the electromagnetic wave shielding material by this invention. It is typical sectional drawing which shows the composite filter which has an optical function layer on the surface or back surface of the electromagnetic wave shielding material by this invention, or both front and back.

  Hereinafter, embodiments of the present invention will be described in detail.

[Electromagnetic wave shielding material]
FIG. 1 is a schematic cross-sectional view showing an example of the electromagnetic wave shielding material of the present invention. In FIG. 1, for convenience of explanation, the ratio of the vertical and horizontal scales is appropriately increased or decreased from the actual one. Further, the metal particles in the conductive pattern layer 10 are also shown exaggerated from the actual ones.
The electromagnetic wave shielding material 100 of the present invention comprises a transparent substrate 40, a primer layer 30 formed on the transparent substrate 40, and metal particles 1 and a binder resin 2 formed in a predetermined pattern on the primer layer 30. And a conductive pattern layer 10 to be included. The distribution of the metal particles in the conductive pattern layer is relatively sparse in the vicinity of the primer layer and dense in the vicinity of the top of the conductive pattern layer, or adjacent metal particles Is relatively large in the vicinity of the primer layer, and is small in the vicinity of the top of the conductive pattern layer, and is laminated on the conductive pattern layer forming side. Consists of a carboxyl group-containing acrylic resin adhesive 3 containing 1H-benzotriazole 4.
Hereinafter, the configuration of the electromagnetic wave shielding material 100 of the present invention will be described in detail.

(Transparent substrate)
The transparent substrate 40 may be appropriately selected from known materials and thicknesses in consideration of required physical properties such as transparency in the visible light region (light transmittance), heat resistance, and mechanical strength, and is not particularly limited. However, in consideration of suitability for continuous processing with a roll-to-roll having excellent productivity, a flexible resin film (or sheet) is preferable. The roll-to-roll refers to a processing method in which the material is unwound from a take-up (roll), supplied, processed appropriately, and then taken up and conveyed or stored.

Examples of the resin for the resin film or sheet include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), ethylene glycol-1,4 cyclohexanedimethanol-terephthalic acid copolymer, ethylene glycol-terephthalic acid-isophthalic acid copolymer. 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, polyamides (nylon) ) Series resin. 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.
If the electromagnetic shielding material and the display filter do not require flexibility, a transparent inorganic material plate such as glass or quartz can be used as the transparent substrate 1.

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.
Moreover, in order to ensure adhesiveness with the primer layer 2 described below, a surface treatment for improving adhesiveness, an easy-adhesion layer, a base layer, and the like may be separately provided on the surface of the transparent substrate.

(Primer layer)
The primer layer 30 is a layer for improving the adhesion between the conductive composition and the printing material. That is, both the transparent substrate and the conductive pattern layer have good adhesion, and are also a transparent layer for ensuring the light transmittance of the opening (conductive pattern layer non-formed part).
Furthermore, in the electromagnetic wave shielding material manufacturing method, the primer layer 30 has a main purpose of transferring ink (conductive composition) from a plate to a printing material (transparent substrate) when the conductive pattern layer 10 is printed. Is a layer for improving the adhesion between the conductive composition after transfer and the printed material, and is provided on the transparent substrate 40 in a state where fluidity can be maintained, and is in contact with the intaglio during intaglio printing It is a layer that solidifies from a liquid state during the process.

As a material constituting such a primer layer, in the present invention, an ionizing radiation curable resin composition containing a liquid (fluid) ionizing radiation curable compound in an uncured state is applied and cured (solidified) by irradiation with ionizing radiation. ) Is used. In addition, an ionized radiation curable resin is cured from an uncured resin having the ability to be cured by a crosslinking reaction or a polymerization reaction by ionizing radiation irradiation, and a cured product obtained by curing the ionizing radiation curable resin (cured material) is cured by ionizing radiation. Called resin. As the ionizing radiation, electromagnetic waves such as ultraviolet rays, visible rays, X rays and γ rays, or charged particle beams such as electron rays and α rays are used. Among these, ultraviolet rays are particularly preferable because they are convenient for handling. In particular, when ultraviolet rays are employed as the ionizing radiation, the ionizing radiation curable resin or the like is referred to as an ultraviolet curable resin or the like.
As the ionizing radiation curable compound, a monomer and / or a prepolymer which is cured by a reaction such as polymerization or crosslinking with ionizing radiation is used.
Examples of such monomers include radically polymerizable monomers such as methyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, isobornyl (meth) acrylate, and dicyclopentenyl (meth) ) 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.

  For curing with ultraviolet light or visible light, a photopolymerization initiator is added. As a photopolymerization initiator, in the case of a radically polymerizable monomer or prepolymer, a benzophenone-based, thioxanthone-based, benzoin-based, acetophenone-based compound, or in the case of a cationic polymerization-based monomer or prepolymer, Metallocene, aromatic sulfonium and aromatic iodonium compounds are used. Specifically, it is assumed that the reaction wavelength band is in a wavelength band of less than 400 nm, which is a normal absorption wavelength of the photopolymerization initiator, and 1-hydroxy-cyclohexyl-phenyl-ketone [Ciba Specialty Chemicals, trade name “Irgacure 184”], 2-hydroxy-2-methyl-1-phenyl-propan-1-one [manufactured by Ciba Specialty Chemicals, trade name “Darocur 1173”] and the like, and the reaction wavelength band is more than usual. As a photopolymerization initiator having a long wavelength and having spectral sensitivity of 400 nm or more, 2-methyl-1 [4- (methylthio) phenyl] -2-morpholinopropan-1-one [Ciba Specialty Chemicals Co., Ltd.] Product name “Irgacure 907”] and the like.

  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 physical properties and durability are not affected.

  The thickness of the primer layer 30 (evaluated by the thickness in the vicinity of the central portion of the non-formed portion of the conductive pattern layer 10) is not particularly limited, but is usually formed to be about 1 μm to 100 μm after curing. . In addition, the thickness of the primer layer 30 is usually the sum of the conductive pattern layer 10 and the primer layer 30 (total thickness. Altitude difference between the top of the conductive pattern layer 10 and the surface of the transparent substrate 40). It is about 1 to 50%.

(Conductive pattern layer)
The electromagnetic wave shielding material 100 in the present invention is mainly a material in which the conductive pattern layer 10 is provided in a predetermined pattern on the primer layer 30 formed on the transparent substrate 40 (hereinafter also referred to as “conductive member”). A member.
The pattern shape is typically a mesh (mesh or lattice) shape, but other shapes such as a stripe (parallel line group or stripe pattern) shape, a spiral shape, and the like 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, a random mesh pattern or a pseudo-random mesh pattern can be used for the purpose of reducing moire. 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 electromagnetic wave shield pattern) is usually about 50 to 95%. In addition to the mesh electromagnetic shield pattern, there may be a case where a grounding pattern such as all adjacent solids is provided on the entire periphery or a part of the periphery of the mesh while maintaining electrical continuity therewith.
Note that the line width is required to be further refined in order to obtain a more highly transparent line. From this viewpoint, it is preferably 30 μm or less, particularly 20 μm or less.

Further, although the thickness of the conductive pattern layer 10 varies depending on the resistance value of the conductive pattern layer, the central portion of the conductive pattern layer 10 has a balance between the electromagnetic shielding performance and the suitability for adhesion of other members onto the conductive pattern layer. In the measurement at (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 conductive pattern layer 10 is formed by forming a conductive composition (conductive ink or conductive paste) containing the metal particles 1 and the binder resin 2 on a substrate or a transparent primer layer by a printing method described later. Obtainable.

The metal particles 1 constituting the conductive composition are particles of a low resistivity metal such as gold, silver, platinum, copper, nickel, tin, and aluminum.
The shape of the metal 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.
The size of the metal particles is arbitrarily selected depending on the type, and thus cannot be specified unconditionally. However, those having an average particle size of about 0.01 to 10 μm can be preferably used. In order to obtain a good electromagnetic wave shielding property by lowering the electric resistance of the obtained conductive pattern layer (preferably, having a surface resistivity of 0.8Ω / □ or less), it is preferable that the average particle diameter is small. Is preferably an average particle size of 0.1 to 1 μm. In addition, regarding the particle size distribution, in order to reduce the electric resistance of the obtained conductive pattern, the particle size distribution is relatively small compared with particles having a relatively large particle size rather than a narrow distribution width and close to a single particle size. It is better to consist of a mixed system with particles of a particle size.
The content of the metal particles in the conductive composition is arbitrarily selected according to the conductivity of the metal particles and the form of the particles. However, suitable electromagnetic shielding performance is exhibited, and the mechanical strength of the conductive pattern layer is maintained. And in order to combine printability, metal particles can be contained in the range of 40-99 mass parts among 100 mass parts of solid content of an electroconductive composition, for example. 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.
When measuring the particle diameter by observation, when the particle shape is a sphere, the diameter is the particle diameter. When the particle shape is non-spherical, the diameter of the circumscribed sphere of the particle is used as the particle diameter.

The distribution of the metal particles 1 in the conductive pattern layer of the electromagnetic wave shielding material of the present invention is in the vicinity of the top of the conductive pattern layer (direction away from the primer layer) as conceptually illustrated in the cross-sectional view of FIG. Is relatively small in the interval between adjacent particles, and the particle number density, that is, the number of particles per unit volume is high (dense), while near the bottom of the conductive pattern layer (direction approaching the primer layer) ) Is a distribution in which the interval between adjacent particles is relatively large and the particle number density is low (sparse).
The ratio of the number density of the metal particles in the vicinity of the top of the conductive pattern layer when the number density of the metal particles 1 in the region adjacent to the interface with the primer layer is 1 is preferably in the range of about 1.5 to 10.
Moreover, in order to express high conductivity and exhibit good electromagnetic wave shielding properties, the average particle spacing between adjacent metal particles is 0.5 to 3 μm in the region adjacent to the interface with the primer layer, in the vicinity of the top. A range of 0 to 0.5 μm is preferable.
Because of this distribution, the metal particles gather densely near the top of the conductive pattern layer, the electrical contact between the particles is good, the electrical resistance is lowered, and the electromagnetic wave shielding effect is enhanced. Further, since the distribution of the metal particles is sparse in the vicinity of the primer layer, the light reflection of the conductive pattern layer is reduced and the image contrast is good even when the transparent substrate side is directed outward.
In particular, when the conductive pattern layer 10 is formed of a wire rod pattern such as a mesh or a stripe, the distribution state of the metal particles 1 in the conductive pattern layer 10 does not depend on the extending direction of the wire rod pattern ( The particle number density in the unit volume is constant in the extending direction). Therefore, in the case of the conductive pattern layer 10 including such a wire rod pattern, the number density of the metal particles 1 in the unit volume is in the unit area in the main cutting plane (cross section orthogonal to the extending direction) of the wire rod pattern. The number density (surface density) of the metal particles 1 can be evaluated. That is, as shown in FIG. 1, if the surface density of the number of metal particles 1 is larger in the vicinity of the top portion than the vicinity of the primer layer 30 in the main cutting plane, that is, the volume density of the number of metal particles 1. It may be determined that the distribution near the top is larger than that near the primer layer 30.
The surface density of the metal particles 1 is measured by taking a microscopic (enlarged) photograph of the main cut surface of the conductive pattern layer 10 and showing a specific position (point) between the vicinity of the primer layer and the vicinity of the top on the photograph. The number of metal particles within an appropriate measurement area as a center is counted and divided by the measurement area to obtain the surface density of the number of metal particles at the specific position.
Similarly, the distance between adjacent metal particles 1 in the conductive pattern layer 10 does not depend on the extending direction of the wire pattern. For this reason, in the case of the conductive pattern layer 10 including such a wrinkle pattern, it can be evaluated by the particle spacing in the unit area on the main cut surface of the wrinkle pattern. That is, as shown in FIG. 1, if the distance between adjacent metal particles 1 in the main cut surface is a distribution that is smaller in the vicinity of the top portion than in the vicinity of the primer layer 30, that is, including the extending direction. Similarly, regarding the distribution of the distance between adjacent particles in the dimensional space, it may be determined that the distribution near the top is smaller than that near the primer layer 30.
The distance (distance) between the adjacent metal particles 1 is measured by taking a microscopic (enlarged) photograph of the main cut surface of the conductive pattern layer 10 and specifying the area from the vicinity of the primer layer to the vicinity of the top on the photograph. For the metal particle 1 located at the point, the distance from 3 to 10 other metal particles is measured in order from the shortest distance from the metal particle, and the average value of this is used to determine the specific particle present at the position. The distance between adjacent metal particles.

In order to control the density distribution of the metal particles 1 in the conductive pattern layer so that the distribution is relatively sparse near the primer layer and dense near the top of the conductive pattern, or adjacent In order to make the interval between the metal particles 1 relatively large in the vicinity of the primer layer and small in the vicinity of the top of the conductive pattern layer, for example, an intaglio printing method described later is used. In the applied electromagnetic shielding material manufacturing method, in the recess of the upper surface of the conductive composition filled in the concave portion of the plate surface, the pressure for pressing the primer layer in a fluid state on the transparent substrate is set high, and the uncured state It is effective to set the viscosity of the conductive composition at a low value, and to solidify after releasing from the plate surface without solidifying the conductive composition in the intaglio recess.
In addition, the density distribution and orientation state of these metal particles 1 are the kind of the binder resin 2 of the conductive composition, the material and particle diameter and particle shape of the metal particles, the blending ratio of the binder resin and the metal particles, the metal particles and the resin. It depends on the specific gravity difference with the binder and the coating conditions and solidification conditions of the conductive composition. In practice, conditions that match the desired density distribution and orientation of the metal particles are determined experimentally from various conditions that affect the density distribution and orientation state of these metal particles. Regarding the specific gravity difference between the metal particles 1 and the binder resin 2, in general, when a normal metal is used as the metal particles and an organic polymer compound is used as the binder resin, “the specific gravity of the metal particles> the specific gravity of the binder resin”. Therefore, when the number density of the metal particles is distributed as described above by using only the specific gravity difference, the conductive pattern layer 10 is solidified from the fluid state with the top portion in the same direction as the direction of gravity (downward). It is effective to squeeze.

As the binder resin 2 constituting the conductive composition, a thermosetting resin, an ionizing radiation curable resin, or a thermoplastic resin 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. Resins such as polyester resins can be exemplified, and examples of the ionizing radiation curable resin include those described above as the material of the primer, and these are used singly or in combination of two or more. Examples of the thermoplastic resin include thermoplastic polyester resins, polyvinyl butyral resins, thermoplastic acrylic resins, thermoplastic polyurethane resins, vinyl chloride-vinyl acetate copolymers, and the like. A mixture of two or more types is used. 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 is no restriction | limiting in particular in the kind of solvent used as an electrically conductive paste, It can select from the solvent generally used for printing ink, and can use it. The content of the solvent is usually about 10 to 70% by mass, but is preferably as small as possible within a range where necessary fluidity can be obtained. In addition, when an ionizing radiation curable resin is used, a solvent is not necessarily required because it is inherently fluid.

(Method for forming conductive pattern layer)
In order to form the conductive pattern layer 10 having a predetermined pattern, the conductive composition is printed by intaglio printing described in Patent Document 2.
This printing method uses a doctor blade or the like to fill only a concave portion of an intaglio plate with a conductive composition, and a transparent base material on which a liquid primer layer has been formed on one side thereof, with the primer layer in contact with the intaglio plate. The primer layer is brought into contact, for example, by pressure bonding with a pressure roller, and after the primer layer is solidified from a liquid state to a solid state in a contact state, the transparent substrate is separated from the intaglio plate to release the plate, The conductive composition is transferred onto a solidified primer layer on a transparent substrate and printed.

After printing, that is, after release, the conductive pattern layer 10 that is still liquid is appropriately subjected to a drying operation, a heating operation, a cooling operation, a chemical reaction operation, and the like, and solidified by being solidified. To complete. For example, a drying operation removes unnecessary volatile components such as a solvent in the conductive composition, and a heating operation promotes a necessary chemical reaction such as drying and thermal curing of the conductive composition, so that a cooling operation is performed. In order to accelerate the solidification of the conductive composition and primer layer of thermoplastic resin that has been heated and melted, the chemical reaction operation may be performed by other means such as ionizing radiation irradiation that does not involve heating. To make progress.
Further, the conductive composition may be semi-cured and solidified on the plate and completely cured after the release.

In general, in intaglio printing, when a conductive composition is supplied to a plate surface, the excess of the composition is scraped off with a doctor blade or the like to fill the concave portion of the plate with the composition, a dent is formed on the surface of the filled composition. Occurs. This dent is thought to be due to volumetric shrinkage due to solvent drying in the composition, rheological behavior of the composition during scraping, and the like. Due to the concave portions, there were problems such as poor adhesion to the transparent substrate and a decrease in the transfer rate of the composition onto the transparent substrate.
On the other hand, in the intaglio printing described in Patent Document 2, printing is performed through a liquid and fluid primer layer even when a depression (dent) is formed in the upper part of the conductive composition filled in the intaglio depression. The primer layer can be poured into the recess and brought into close contact, and then the primer layer is solidified and then the transparent base material is released from the intaglio. Therefore, the primer layer is predetermined via the primer layer 30 solidified on the transparent base material. The conductive pattern layer 10 of the pattern can be formed even with a thin line without occurrence of printing failure such as disconnection or shape failure due to insufficient transfer or insufficient ink adhesion. In the intaglio printing process, as a result of the primer layer flowing in and filling the depressions formed in the surface of the ink filled in the intaglio depressions as described above, the resulting conductive member has a thickness of the primer layer of the conductive pattern layer. The thickness of the portion where is formed becomes thicker than the thickness of the portion where the conductive pattern layer is not formed.

After the conductive composition is transferred from the intaglio depression to the transparent substrate through the primer layer and solidified to form a conductive pattern layer, (i) as hot water treatment, By performing the treatment at a high temperature and / or (ii) contacting with an acid as the acid treatment, the volume resistivity and further the surface resistivity of the conductive pattern are lowered, and the conductive performance is improved.
The hot water treatment (i) is performed by immersing the conductive member in hot water having a water temperature of 30 to 100 ° C., flowing hot water over the conductive member, or in an atmosphere having a relative humidity of 60% or more at an air temperature of 30 to 100 ° C. The method of exposing to is preferable, and the treatment time is about 5 minutes to 20 seconds.
In the acid treatment of (ii), the acid is not particularly limited, and can be selected from various inorganic acids and organic acids, but is preferably hydrochloric acid, sulfuric acid, citric acid or an aqueous solution thereof, and the treatment time with the acid is several minutes. The following is sufficient, and the processing temperature is sufficient at room temperature. The method of treating with an acid is not particularly limited, but the method of immersing a conductive member in an acid solution is preferable because of its excellent conductivity improving effect, and the acid concentration is preferably 1 mol / L or less, more preferably 0. .1 mol / L or more. As the acid treatment, one type of acid may be used for contact once, or two or more types of acids may be used for sequential contact with another acid. In particular, when the electromagnetic wave shielding material is first immersed in hydrochloric acid and then immersed in citric acid, the electrical resistance reducing effect is better than when immersed in hydrochloric acid alone or in citric acid only once.
Among these electrical resistance reduction treatments, it is preferable to perform the hot water treatment (i) subsequently after the acid treatment (ii) from the viewpoint of the electrical resistance reduction effect and workability.
By this electrical resistance reduction treatment, the surface resistivity of the entire conductive pattern is reduced to about 80 to 30% before the treatment (the apparent volume resistivity is also about 80 to 30% before the treatment).

The reason why the surface resistivity is reduced by the electrical resistance reducing process is that the metal particles 1 adjacent to each other with an interval of 0 are observed by the electrical resistance reducing process from the observation of the cross section of the conductive pattern layer 10 by an electron micrograph. It is presumed that at least a part of each other forms a part having a continuous (fused) connection. Here, the fusion refers to a state in which the boundary surface (line) of the portion in contact with the adjacent metal particles at the interval 0 disappears and the adjacent particles are integrated in the contact portion in the electron microscope observation. On the other hand, in the state before performing the above-described electrical resistance reduction treatment, the boundary surface (line) is present in the portion in contact with the interval 0 of the adjacent metal particles in the electron microscope observation, and is simply in contact. Stays.
In addition, even after the electrical resistance reduction treatment is performed, the binder resin 2 exists in the gap between the metal particles 1 in the conductive pattern layer 10, and the metal particles 1 are separated from each other by the metal particles 1. In the region excluding the region where the two are fused, they are joined together. In other words, as shown in the sectional view of FIG. 1, the conductive pattern layer 10 includes a plurality of metal particles 1 dispersed in the binder resin 2, and at least a part of the metal particles 1. In the middle, adjacent metal particles 1 are fused together, and a path through which the fused metal particles 1 are connected to each other can be formed.

(Adhesive layer)
In the electromagnetic wave shielding material 100 of the present invention, an adhesive layer 20 is provided on the conductive pattern layer 10 side of the conductive member.
The pressure-sensitive adhesive layer is an acrylic pressure-sensitive adhesive, and an acrylic pressure-sensitive adhesive containing a carboxyl group is used for good adhesion to the optical functional layer provided thereon. The pressure-sensitive adhesive layer is added with a rust preventive agent in order to prevent the conductive pattern layer 10 (the metal particles 1 therein) from being colored.
There is no restriction | limiting in particular as kind of this rust preventive agent, For example, 1H-benzotriazole, 1H-benzotriazole sodium salt, 1H-benzotriazole potassium salt, 1H-tolyltriazole, 1H-benzotriazole amine salt, etc. Benzotriazole compounds, phenyltetrazole compounds, 2-aminobenzothiazole, 2-aminopyridine, 2-aminopyrimidine, 2-aminoquinoline, 2-aminoquinazoline, 4-aminoquinazoline, 2-aminoquinoxaline, 8-amino Purine, 2-aminobenzimidazole, aminotriazine or aminotriazole and substituted derivatives thereof are used.
Among these, benzotriazole compounds are preferable. Among these, 1H-benzotriazole is more preferable because of its rust prevention performance and ease of handling.

As the acrylic pressure-sensitive adhesive containing a carboxyl group, a copolymer having at least a monomer of (meth) acrylic acid alkyl ester and a monomer having a carboxyl group as a copolymerization component is used. In the present specification, (meth) acrylic acid means acrylic acid or methacrylic acid, and (meth) acrylate means acrylate or methacrylate.
In the copolymer, monomers of (meth) acrylic acid alkyl ester include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, (meth) acrylic. One or more of (meth) acrylic acid alkyl ester monomers having an alkyl group having about 1 to 18 carbon atoms such as octyl acid and lauryl (meth) acrylate are used.
As the monomer having a carboxyl group, one or more vinyl monomers having a carboxyl group such as (meth) acrylic acid, itaconic acid, crotonic acid, maleic acid, fumaric acid and the like are used.
In addition, the copolymer includes (meth) acrylic acid alkyl ester having a hydroxyl group such as 2-hydroxyethyl (meth) acrylate, 2-hydroxy-3-phenyloxypropyl (meth) acrylate, styrene, vinyl acetate as other monomers. One or more vinyl monomers such as a halogenated vinyl compound may be used.

  The content of the 1H-benzotriazole in the pressure-sensitive adhesive layer is preferably 0.1 to 20% by mass, and more preferably 0.5 to 5% by mass.

The 1H-benzotriazole-containing pressure-sensitive adhesive layer 20 of the present invention is formed by applying a coating solution comprising a pressure-sensitive adhesive solution prepared by dissolving the pressure-sensitive adhesive and 1H-benzotriazole in a suitable solvent on the conductive pattern layer 10. It is formed by drying after forming a coating film.
Alternatively, the pressure-sensitive adhesive layer 20 that has been coated and dried in advance on the release sheet is laminated on the conductive pattern layer 10 so that the pressure-sensitive adhesive layer side faces the conductive pattern layer side, Thereafter, it can also be formed by a method of peeling and removing only the release sheet (so-called transfer coating method).
Examples of the solvent include aliphatic hydrocarbons such as hexane, heptane, and cyclohexane; aromatic hydrocarbons such as toluene and xylene; halogenated hydrocarbons such as methylene chloride and ethylene chloride, methanol, ethanol, propanol, butanol, and 1-methoxy. Examples include alcohols such as 2-propanol; ketones such as acetone, methyl ethyl ketone, 2-pentanone, methyl isobutyl ketone, and isophorone; esters such as ethyl acetate and butyl acetate; and cellosolv solvents such as ethyl cellosolve.

  The thickness of the 1H-benzotriazole-containing pressure-sensitive adhesive layer 20 is preferably in the range of 5 to 800 μm, more preferably in the range of 10 to 500 μm, and particularly preferably in the range of 20 to 300 μm. Note that the pressure-sensitive adhesive layer completely prevents the conductive pattern layer 10 from being uneven in the conductive member from the viewpoints of ensuring sufficient adhesion with the adherend and preventing air bubbles from remaining in the concave portions of the conductive pattern layer 10. It is preferable to coat so that the surface of the pressure-sensitive adhesive layer becomes a flat surface.

[Composite filter]
By providing the optical functional layer 200 on the pressure-sensitive adhesive layer 20 (front surface) of the electromagnetic wave shielding material 100 thus obtained, on the transparent substrate side (back surface) of the electromagnetic wave shielding material 100, or on both surfaces thereof, A composite filter 1000 is obtained.
The pressure-sensitive adhesive layer 20 serves as an adhesive layer or a flattening layer when an optical functional layer is provided thereon, and when the optical functional layer is provided only on the transparent substrate side, the composite filter is attached to the image display device main body. Or you may play the role which adhere | attaches on an image display apparatus board | substrate.
As the optical functional layer 200, a conventionally known layer is used, and examples thereof include a near infrared absorption layer, a neon light absorption layer, an ultraviolet absorption layer, an antireflection layer, an antiglare layer, and a thin film microlouver layer.
As an optical functional layer formation method, in the case of an antireflection layer, a method of laminating an antireflection layer formed on a support made of a transparent resin sheet in advance, or directly reflecting on another optical functional layer constituting layer Any method of coating the prevention layer may be used. Moreover, when using absorption pigment | dyes, such as a near-infrared absorption layer and a neon light absorption layer, you may paste together the resin film containing these absorption pigment | dyes, or these absorption pigment | dyes are contained in the said adhesive layer 20. The pressure-sensitive adhesive layer can also have the function.
The composite filter 1000 is a single product or a laminate of various other functional layers as a display filter, and the optical functional layer including an antireflection layer or an antiglare layer is directed to the viewer side with the front surface of the display panel. And an image display device provided with the composite filter of the present invention is obtained. Examples of other functional layers include an impact resistant layer, an antistatic layer, a hard coat layer, an antifouling layer, an antibacterial layer, and an antifungal layer.

[Use]
The composite filter of the present invention can be used for various applications. In particular, PDPs and CRTs used for various display units such as television receivers, measuring instruments and instruments, office equipment, medical equipment, amusement equipment, computing equipment, telephones, electrical signs (lighting billboards), etc. It is suitable for a front filter of an image display device such as LCD, EL, etc., and particularly suitable for a PDP. In addition, it can also be used for electromagnetic shielding applications such as windows for buildings such as houses, schools, hospitals, offices, stores, etc., windows for vehicles such as vehicles, airplanes and ships, and windows for various home appliances such as microwave ovens. It is.

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

Example 1
(1) Preparation of pressure-sensitive adhesive layer-forming coating solution 1 part by weight of 1H-benzotriazole is added to 100 parts by weight of an acrylic pressure-sensitive adhesive having an acid value of 6.8 (trade name: SK2094, manufactured by Soken Chemical Co., Ltd.). Further, 40 parts by mass of MIBK was added and stirred and mixed to prepare a coating solution for forming an adhesive layer.
(2) Production of Conductive Member First, as the transparent substrate 40, a colorless transparent biaxially stretched polyethylene terephthalate (PET) of a long roll wound with a width of 1000 mm and a thickness of 100 μm having a melamine resin-based easy adhesion layer formed on one side. A film was prepared. The PET film set in the supply part was drawn out, and the UV curable resin composition for the primer layer was applied and formed on the surface of the easy adhesion layer so as to have a thickness of 5 μm. The application method employs a normal gravure reverse roll coating method, and the UV curable resin composition includes a monofunctional acrylate monomer 44 comprising 35 parts by mass of an epoxy acrylate prepolymer, 12 parts by mass of a urethane acrylate prepolymer, and phenoxyethyl acrylate. 9 parts by mass of trifunctional acrylate monomer composed of ethylene oxide-modified isocyanuric acid triacrylate, and 1 mass of 1-hydroxy-cyclohexyl-phenyl-ketone (manufactured by Ciba Specialty Chemicals, trade name: Irgacure 184) as a photoinitiator A part-added product was used.
Next, the PET film on which the uncured primer layer is formed is used for an intaglio roll that performs a transfer process. Prior to that, a square lattice mesh with an opening line width of 20 μm, a line pitch of 300 μm, and a plate depth of 20 μm. The conductive composition is applied to the plate surface of the intaglio roll on which the concave portions to be patterned are formed with a pick-up roll, and the conductive composition other than the concave portions is scraped off with a doctor blade to fill the conductive composition only in the concave portions. I let you. A concave portion was formed on the surface of the conductive composition filled in the concave portion. A PET film on which an uncured and liquid primer layer is formed is supplied between the intaglio roll filled with the conductive composition in the recess and the nip roll, and the pressing force (biasing force) of the nip roll against the intaglio roll ) To allow the primer layer to flow into the recess of the conductive composition existing in the recess, to bring the conductive composition and the primer layer into close contact with each other without any gap, and to partly adhere the primer to the conductive composition in the recess. It penetrated inside. In addition, the used conductive composition used the silver paste of the following compositions.
93 parts by mass of flaky silver powder having an average particle diameter of about 2 μm as metal particles 1, 7 parts by mass of thermoplastic polyester urethane resin as binder resin 2, and 25 parts by mass of butyl carbitol acetate as a solvent were mixed and mixed thoroughly. Then, it knead | mixed with 3 rolls and produced the electrically conductive composition.
Next, the transfer process performed is as follows. First, the PET film on which the primer layer is formed is sandwiched between the intaglio roll and the nip roll in a state where the primer layer faces the plate surface side of the intaglio roll. Between the intaglio roll and the nip roll, the primer layer of the PET film is pressed against the plate surface. Since the uncured primer layer has fluidity, the uncured primer layer pressed against the plate surface also flows into the recess filled with the conductive composition, and the conductive composition generated on the inner surface of the recess. Fill the dent of the object.
Thereafter, the intaglio roll is further rotated and irradiated with ultraviolet rays by a UV lamp comprising a D bulb manufactured by Fusion UV Systems Japan (irradiation dose 700 mJ / cm ² ), and an uncured primer comprising a cured product of the ultraviolet curable resin composition. The layer is cured. Due to the curing of the primer layer, the conductive composition in the recesses of the intaglio roll is brought into close contact with the primer layer, and then the film is peeled from the intaglio roll by the nip roll on the outlet side, and the conductive composition is formed on the cured primer layer 2. A layer is transferred. The transfer film thus obtained is passed through a drying zone at 110 ° C. with the conductive composition layer side facing down, whereby the solvent of the silver paste is evaporated and solidified, and the mesh pattern is formed on the primer layer 2. A conductive pattern layer 3 was formed. At this time, the thickness of the pattern portion where the conductive pattern layer 10 exists (thickness difference between the mesh pattern portion where the conductive pattern layer is formed and the other portion) is 19 μm, and the depth of the plate The thickness was 95%, and the silver paste in the concave portion of the plate was transferred with a high transfer rate. When the inside of the concave portion after the transfer was observed, no plate residue of the paste was observed, and no disconnection or shape defect of the mesh pattern was observed.
As a result of magnifying and observing the main cut surface of the conductive pattern layer with an electron microscope, the distribution of metal particles (silver particles) in the conductive pattern layer becomes denser toward the top of the conductive pattern layer, On the contrary, it was found that the distribution was so dense that it became sparser toward the primer layer side. The number of metal particles per unit cross-sectional area in the main cutting plane perpendicular to the mesh wire ridge is 1 / μm ^{2 on} average in the portion adjacent to the primer layer, and 3 / μm ^{2 on} average in the vicinity of the top. there were.
In addition, the distance between the adjacent metal particles at the top of the conductive pattern layer (distance) and the distance between adjacent metal particles in the vicinity of the interface with the primer layer were measured by electron microscope observation, and the average was obtained. The average metal particle interval at the top was 0.5 μm, and the average metal particle interval near the interface with the primer layer was 1.5 μm.
When the surface electrical resistance of the conductive pattern layer of the obtained conductive member was measured (performed in a room temperature atmosphere (temperature 23 ° C., relative humidity 50%)), the surface resistivity was 1.0Ω / □.
Subsequently, the electrical resistance reduction process was performed by the following method.
The conductive member obtained above was immersed in an acid treatment tank filled with 25% hydrochloric acid aqueous solution containing 1% by mass of hydrochloric acid for 30 seconds to be acid-treated, taken out from the acid treatment tank, and pure water having a water temperature of 90 ° C. A hot water treatment was performed by immersing in a warm water tank made of water for 30 seconds, and then dried to such an extent that moisture was removed to obtain a conductive member subjected to an electrical resistance reduction treatment.
The surface resistivity of the conductive member subjected to this electrical resistance reduction treatment was 0.5Ω / □, and a decrease in surface resistivity was confirmed.

(3) Formation of pressure-sensitive adhesive layer For forming the 1H-benzotriazole-containing pressure-sensitive adhesive layer prepared in (1) above on the conductive pattern layer side of the conductive member subjected to the electrical resistance reduction treatment prepared in (2). The pressure-sensitive adhesive forming coating solution was subjected to a Meyer bar No. 5 so that the thickness after drying was 25 μm. 16 was applied. Subsequently, it was heat-dried at 90 ° C. for 1 minute to form a pressure-sensitive adhesive layer containing 1H-benzotriazole.
As described above, the electromagnetic wave shielding material 100 of Example 1 having the configuration as shown in the sectional view of FIG. 1 was obtained.

(4) Moisture and heat resistance test When the electromagnetic wave shielding material 100 of Example 1 was subjected to a moisture and heat resistance test [leaving for 72 hours in an atmosphere with a relative humidity of 90% RH and a temperature of 80 ° C.], the conductive pattern layer could be visually identified. There was no appreciable coloration.

Comparative Example 1
In Example 1, a coating liquid for forming an adhesive that does not contain 1H-benzotriazole was prepared, and this was applied to the conductive pattern layer side of the conductive member subjected to the electrical resistance reduction treatment. Similarly, the electromagnetic wave shielding material of Comparative Example 1 was obtained.
When the moisture and heat resistance test was performed, the conductive pattern layer was colored green.

DESCRIPTION OF SYMBOLS 1 Metal particle 2 Resin binder 3 Acrylic resin adhesive 4 1H-benzotriazole 10 Conductive pattern layer 20 Adhesive layer 30 Primer layer 40 Transparent base material 100 Electromagnetic wave shielding material 200 Optical function layer 1000 Composite filter

Claims (4)

A transparent substrate, a primer layer formed on the transparent substrate, and a conductive pattern layer formed in a predetermined pattern on the primer layer, and a carboxyl group-containing acrylic on the conductive pattern layer forming side An electromagnetic shielding material formed by laminating an adhesive layer made of resin,
The conductive pattern layer comprises metal particles and a binder resin, the distribution of the metal particles in the conductive pattern layer is relatively sparse in the vicinity of the primer layer, and the conductive pattern Dense near the top of the layer,
And the adhesive layer which consists of a carboxyl group-containing acrylic resin contains 1H-benzotriazole, The electromagnetic wave shielding material characterized by the above-mentioned. A transparent substrate, a primer layer formed on the transparent substrate, and a conductive pattern layer formed in a predetermined pattern on the primer layer, and a carboxyl group-containing acrylic on the conductive pattern layer forming side An electromagnetic shielding material formed by laminating an adhesive layer made of resin,
The conductive pattern layer comprises metal particles and a binder resin, and the interval between the adjacent metal particles in the conductive pattern layer is relatively large in the vicinity of the primer layer, and the conductive pattern layer Small near the top of the pattern layer,
And the adhesive layer which consists of a carboxyl group-containing acrylic resin contains 1H-benzotriazole, The electromagnetic wave shielding material characterized by the above-mentioned.   The composite filter formed by laminating | stacking an optical function layer on the one or both surfaces of the electromagnetic wave shielding material of Claim 1 or Claim 2.   The image display apparatus which installed the composite filter of Claim 3 in the front side of the display panel.

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