JP2009004432A - Electromagnetic wave shielding member and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an electromagnetic wave shielding member in which a mesh pattern thin film having high conductivity and sufficiently high film strength is formed on a transparent substrate while using a mesh pattern formed by printing a conductive paste as a base, and to provide a manufacturing method thereof. <P>SOLUTION: In the electromagnetic wave shielding member having a conductive material formed in a mesh pattern on a transparent substrate, the conductive material has a structure in which a plating metal couples metal fine particles in a metal fine particle binding body having a porosity of 20-80% formed by binding the metal fine particles via a binder resin and a surface resistance value is 10 Ω/SQARE or low. The manufacturing method of the electromagnetic wave shielding member has a step in which the metal fine particle binding body having a porosity of 20-80% formed by binding the metal fine particles via a binder resin is formed into a mesh pattern using a printing method, and a step in which the resulted product is subjected to plating process. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electromagnetic wave shielding member disposed on the front surface of various displays and a manufacturing method thereof.

In order to shield electromagnetic waves generated from various displays (image display devices) such as a PDP (plasma display panel) and a CRT (CRT) display, an electromagnetic shielding member is disposed on the front surface of the display.
Examples of such an electromagnetic shielding member include a silver sputtered thin film and a copper mesh. A silver sputtered thin film is expensive and has poor transparency because it covers the entire surface (transparency and conductivity are difficult to achieve at the same time). Although the copper mesh has good compatibility between transparency and conductivity (ie, electromagnetic wave shielding), the copper foil is laminated with a transparent base material and then etched by a photolithography method to produce a mesh shape. Since many are very complicated and more metal materials are thrown away, it is difficult to reduce the cost. Therefore, there is a demand for shortening and simplifying the process. In addition, waste liquid treatment such as a corrosive liquid after use is also required.

As a method for producing a conductive mesh in which the metal material to be discarded is reduced, the following method for forming a metal layer with a plated metal has been proposed.
One is to form a metal thin film layer with a minimum thickness on a transparent substrate by sputtering, create a mesh pattern by photolithography, and apply a metal thick film layer by electrolytic plating on the metal thin film of the mesh pattern. Although it is the method of laminating | stacking (patent document 1), a process will become more complicated than the said copper foil etching method.
The other is a method in which a catalyst layer is printed in a pattern on a transparent substrate, and then a metal layer is provided on the pattern by electroless plating (Patent Document 2). However, the deposition rate of electroless plating is slower than that of electrolytic plating, and it is necessary to lengthen the electroless plating time in order to deposit a metal layer for obtaining desired conductive performance. Further, there is a method of performing electroplating after performing the minimum electroless plating that can be electroplated, but in this case, the number of steps increases as a result, which is complicated.

Japanese Patent No. 3502979 Japanese Patent No. 3363083

  Under such circumstances, the present invention is based on a mesh pattern made by printing an electrically conductive paste, to obtain an electromagnetic shielding member having a mesh pattern thin film with high conductivity and strong film strength formed on a transparent substrate, And it aims at providing the manufacturing method.

  As a result of investigations for achieving the above object, the present inventors printed a conductive paste such as a metal paste in a mesh pattern on a transparent substrate, dried the solvent, and had a porosity of 20 to 80%. The porous conductive fine particle binder is obtained, and this is then impregnated in the plating bath, so that the plating solution enters the voids, and the plating metal is deposited and grown on the surface of the conductive fine particles. The conductive fine particles are connected or enveloped by the plated metal, and are integrated so that the entire mesh pattern exhibits high conductivity on a macroscopic scale, thereby exhibiting high electromagnetic shielding properties and strong membrane strength. The inventors have found that an electromagnetic wave shielding member having a patterned thin film formed on a transparent substrate can be obtained, thereby completing the present invention.

That is, the present invention
(1) An electromagnetic wave shielding member in which a conductive material is formed in a mesh pattern on a transparent substrate, the conductive material having a porosity of 20 to 80% in which conductive fine particles are bound by a binder resin. In the conductive fine particle binder, the plated metal connects the conductive fine particles, and the surface resistance value thereof is 10Ω / □ or less;
(2) The electromagnetic wave shielding member according to the above (1), wherein the conductive fine particles are gold, silver, copper, iron, nickel or aluminum gold fine particles, and the plated metal is gold, silver, copper, chromium or nickel. ;
(3) The electromagnetic wave according to claim 1 or 2, wherein the conductive material comprises 1 to 50 parts by mass of a binder resin and 0.1 to 300 parts by mass of a plated metal with respect to 100 parts by mass of the conductive fine particles. Shielding member;
(4) Using a printing method, a conductive fine particle binder having a porosity of 20 to 80% and having a porosity of 20 to 80% is formed on a transparent substrate in a mesh pattern. A method of producing an electromagnetic wave shielding member, characterized by being plated;
(5) The printing method uses a metal paste having a solid content of 60 to 90% on a transparent substrate, the binder resin being 1 to 50 parts by mass with respect to 100 parts by mass of metal fine particles as conductive particles. The method for producing an electromagnetic wave shielding member according to the above (4), which is printed and the solvent is dried;
Is to provide.

The electromagnetic wave shielding member of the present invention is a conductive fine particle formed by connecting and enveloping the conductive fine particles in a porous conductive fine particle binder having a predetermined porosity formed in a mesh pattern. Is a structure in which a mesh pattern thin film having high electromagnetic shielding properties and strong film strength is formed on a transparent substrate.
That is, since the conductive mesh in the electromagnetic wave shielding member of the present invention is a conductive fine particle binder that connects and envelops the conductive fine particles with a plated metal, a thick plated metal layer is formed in the manufacturing process. Compared with the conventional method to be formed, a predetermined conductivity can be reached with a small amount of plating metal and a short plating time. In the present invention, conductive fine particles that bear most of the conductivity of the mesh pattern are formed on a substrate at a higher speed than plating by printing, and the fine particles are connected by metal deposition (plating). Therefore, the manufacturing time can be shortened as a whole. Therefore, according to the present invention, a high-performance electromagnetic shielding member can be obtained by a simplified process.
Also, instead of forming a plating layer on the conductive fine particle layer, it is necessary to connect the conductive fine particles (mainly to grow metal in the space inside the printed mesh pattern). The increase in thickness is small, and the adhesive layer does not fill the mesh shape when bonded to an adhesive layer for providing an antireflection layer (AR layer), an antiglare layer (AG layer) or the like thereon. The problem that white turbidity easily occurs due to air bubbles (voids) is less likely to occur.

The electromagnetic wave shielding member of the present invention is obtained by forming a conductive material in a mesh pattern on a transparent substrate, and the conductive material (conductive mesh) is a conductive fine particle made of a conductive material such as metal. In the conductive fine particle binder having a predetermined porosity, which is bonded with a binder resin, the plated metal connects the conductive fine particles. Further, the electromagnetic wave shielding member of the present invention is formed by pattern printing a conductive paste on a transparent substrate, drying a solvent, and forming a conductive fine particle binder having a predetermined porosity in a mesh pattern. Manufactured by plating.
Hereinafter, the present invention will be described in detail.

(Transparent substrate)
As the transparent substrate, a transparent substrate at least in the visible region can be used. Polyester resins such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), acrylic resins such as polymethyl methacrylate, polypropylene, cycloolefin A polyolefin resin such as a resin, a transparent resin film or plate such as polycarbonate (PC) or polyimide (PI), or a plate such as soda glass, potassium glass, or borosilicate glass can be used.
Moreover, the transparent base material may have an undercoat layer for imparting various functions as appropriate on the conductive paste application side. Examples of imparting various functions include adhesion improvement, durability improvement, printability improvement, solvent resistance improvement and the like by corona discharge treatment and easy adhesion primer coating treatment.
The thickness of the transparent substrate is not particularly limited as long as it depends on the use, but when it is made of a transparent resin film, it is usually about 10 to 500 μm and is a transparent resin plate or glass plate. In the case, about 1 to 5 mm is usually preferable.

[Conductive mesh]
The conductive mesh constituting the electromagnetic wave shielding member of the present invention is obtained by printing a conductive paste on a transparent base material in a mesh pattern and drying the solvent, and the conductive fine particles are bound by a binder resin. It is produced by subjecting a porous conductive fine particle binder having a porosity of 5 to a plating treatment.
Here, the porosity of the conductive fine particle binder is required to be 20 to 80%, and preferably 30 to 70%. When the porosity is less than 20%, the exposed conductive fine particles are reduced in the conductive fine particle binder, and a desired conductivity cannot be obtained even after a predetermined time of plating treatment, and metal ions are supplied into the binder. Becomes difficult. When the porosity exceeds 80%, the conductive mesh after the plating process is weak and brittle.
In the conductive mesh of the present invention, in a conductive fine particle binder having a predetermined porosity in which conductive fine particles are bound by a binder resin, plating metal is deposited on the surface of the exposed conductive fine particles and grows. The conductive fine particles are connected, covered, and enveloped by a metal to form a structure in which the conductive fine particles are integrated. In the conductive mesh of the present invention, the constituent ratio of the conductive fine particles, the binder resin, and the plating metal, which are the constituent components, is 1 to 50 parts by mass of the binder resin with respect to 100 parts by mass of the conductive fine particles. Preferably, the amount is 3 to 30 parts by mass, the plating metal is more preferably 0.1 to 300 parts by mass, and more preferably 1 to 200 parts by mass. If the binder resin ratio is too large, the exposed fine conductive particles are reduced in the conductive fine particle binder and the desired plated metal connector cannot be obtained. If the binder resin ratio is too small, the film strength of the conductive mesh is weak. Become. In addition, if the plating metal ratio is too small, the metal fine particles cannot be sufficiently connected, so that the desired conductivity cannot be obtained, and even if the plating metal ratio is too large, the conductivity is saturated and there is no further significant improvement. Become.

The mesh pattern of the conductive mesh in the present invention is not particularly limited as the shape of the opening, for example, a triangle such as a regular triangle, a square such as a square, a rectangle, a rhombus, a trapezoid, a polygon such as a hexagon, The shape is a circle or an ellipse, and forms a pattern such as a lattice pattern, a honeycomb pattern, or a random mesh pattern.
And it is preferable from the point of light transmittance that the width | variety of the line part of a mesh is 5 micrometers-50 micrometers, pitch is 100-500 micrometers, and an aperture ratio is 60-95%.

  The thickness of the conductive mesh of the present invention is as thin as possible within a range that can ensure a desired conductivity and a predetermined film strength, which is costly and eliminates air bubbles at the time of adhesive bonding on the cost. It is preferable from the viewpoint. The thickness is preferably about 1 to 50 μm, and more preferably about 1 to 20 μm.

[Conductive paste]
The conductive paste used for manufacturing the conductive mesh of the present invention is as follows, in which conductive fine particles are uniformly dispersed in a solution in which a binder resin is dissolved in a solvent.
Examples of the conductive fine particles include metal particles such as gold, silver, platinum, copper, iron, tin, nickel, and aluminum, composite metal particles, carbon particles such as graphite particles and carbon black, or these metals on the surface of resin particles. Or those coated with graphite can be used. These may be used alone or in combination. For example, black carbon particles may be mixed with metal particles to improve display contrast. Here, metals such as gold, silver, and nickel exhibit conductivity that can be energized immediately after pattern printing, but metals that are easily oxidized in the air, such as copper, iron, and aluminum, are subjected to electrochemical treatment and chemicals after pattern printing. Conductivity that can be energized can be developed by performing treatment or the like. In particular, in the case of copper powder, the resistance of the oxide film on the surface is high, and the resistance of the binder is extremely high because the oxide films of the particles are in contact with each other. Therefore, it is essential to remove the oxide film on the surface by chemical treatment, etc., but this oxide film can be easily removed by immersing it in an acidic solution. It is only necessary to pass a bath. In this case, if copper powders are bonded by metal deposition, re-insulation by air oxidation does not proceed.
The particle size of the conductive fine particles is preferably small enough to make a paste, and a particle size of 100 μm or less is preferable, but is preferably sufficiently smaller than the line width of the mesh pattern, and more preferably 10 μm or less. . The shape is not particularly limited, such as spherical, spheroid, polyhedral, lump, scale, disk, fiber, or needle shape, and particles having various shapes, particle sizes, and the like may be used by appropriately mixing them. Good. In the case of a shape other than a sphere, the particle diameter is the maximum long diameter in the case of a spheroid, the diameter of a circumscribed sphere in the case of a polyhedron, or the maximum diagonal length, and in the longitudinal direction (long) in the case of a fibrous or needle shape. Axis length) etc. are evaluated.
The binder resin may be any resin that has adhesiveness to the conductive fine particles and the transparent substrate and can maintain a stable coating film against the plating solution, such as an acrylic resin, a polyester resin, an ethylene-vinyl acetate resin, and a urethane resin. A phenol resin, an epoxy resin, or the like can be used.
As the solvent, an organic solvent which dissolves the binder resin and has a boiling point of about 100 to 250 ° C. can be used. If the boiling point is too low, the solvent is volatilized during paste preparation or pattern printing and the paste properties and the like change, resulting in inconvenience. If the boiling point is too high, drying after printing takes too much time.

The conductive paste used in the present invention is a solid composed of 50 parts by mass of binder resin with respect to at least 100 parts by mass of conductive fine particles in order to obtain a conductive fine particle binder having a porosity of 20 to 80%. The conductive paste is preferably 60 to 90%.
Examples of the conductive paste used in the present invention as described above include commercially available silver pastes such as FA-333 (manufactured by Fujikura Kasei Co., Ltd.), and commercially available pastes such as ACP-051 (manufactured by Asahi Chemical Research Laboratories). Copper paste can also be used, but to adjust the porosity of the conductive fine particle binder and to adjust the coating suitability of the paste, the shape and particle size of the conductive fine particles can be adjusted, and the binder ratio can be adjusted. The solid content is preferably adjusted for use. In addition, these pastes include, for example, adjustment of paste coating suitability, improvement of paste stability, improvement of strength of conductive fine particle binders and improvement of adhesion to base materials, adjustment of voids of conductive fine particle binders, conductivity A filler or an additive may be added separately according to various purposes such as color adjustment of the fine particle binder.
The filler can be selected from various shapes such as a spherical shape, a block shape, a scale shape, a disk shape, and a fiber shape. The filler may remain in the coating film during plating, or may dissolve (decompose) during plating to form a void.

[Printing method]
The printing method for printing the conductive paste in a mesh pattern on the transparent substrate does not particularly limit the effect of the present invention, and may be appropriately selected and used depending on the properties of the conductive paste.
When using nanometer-sized metal fine particles, the viscosity of the conductive paste is generally low, and ink jet printing, gravure printing, flexographic printing, etc. are suitable. When using metal fine particles of submicron to micron size, the conductive paste is generally Viscosity is high, and gravure printing, flexographic printing, screen printing and dispenser are suitable.
After printing, for example, by drying with hot air at about 80 to 150 ° C. to volatilize the solvent, conductive fine particle binders having a predetermined porosity formed in a mesh pattern on the transparent substrate are obtained.

[Plating treatment]
The metal fine particle binder having a predetermined porosity formed in a mesh pattern on the transparent substrate obtained above is immersed in a plating bath to deposit the metal, whereby the conductive fine particles are plated. It is possible to obtain the conductive mesh of the present invention that is enveloped and integrated with a metal.
As the plating bath, ordinary electroless and electrolytic plating baths can be used. Examples of the plating metal that can be used include gold, silver, platinum, copper, chromium, and nickel. When metal fine particles are used as the conductive fine particles, the plating metal and the metal fine particles in the conductive paste may be the same type of metal or different metals.
Here, if metal deposition preferentially occurs on the surface of the conductive fine particle binder, the entrance of the ion supply path to the void inside the binder becomes narrow, and the metal to be deposited inside the binder Since the supply of ions is insufficient, precipitation that connects the conductive fine particles inside hardly occurs. In order to prevent this, it is necessary to supply abundantly metal ions consumed for metal deposition inside the binder, and the plating solution is vigorously stirred. Illustrates methods such as stimulating, spraying fresh plating solution strongly onto the binder, improving the penetration of plating solution into the binder with a surfactant, etc., and increasing the gap in the binder. it can. In addition, in the case of electrolytic plating, it is also possible to suppress selective deposition on the surface by adjusting the energization conditions, such as a method of changing the current density stepwise, pulse plating, etc. This method can be exemplified.
The methods exemplified above may be used alone or in combination. However, the method is not limited to these methods, and as a result, a method that enables bonding of conductive fine particles inside the binder. If it is.
Moreover, in the case of plating, you may perform the reduction | restoration provision process by a catalyst or a reducing agent, and an activation process as needed. These treatments may be performed according to known methods known for each plating.
In the case of the electroless plating of the present invention, the necessary plating time is usually 5 to 150 minutes in order to obtain a conductive mesh having a thickness of about 0.1 to 5 μm.
In the case of the electrolytic plating of the present invention, in order to obtain a conductive mesh having a thickness of about 0.1 to 5 μm, the current density is usually 0.1 to 5 A / dm ² and the plating time is 1 to 30 minutes. is there.
After the plating treatment, the electromagnetic wave shielding member of the present invention is obtained by washing with water and drying.
In addition, when the electroconductive mesh pattern after plating contains the material which is easy to rust in air | atmosphere, you may perform a rust prevention process as needed. Further, in order to improve the contrast of the display, a coloring process may be further performed.
As the rust prevention treatment, for example, known materials such as chromate treatment, coating of a resin film having an appropriate barrier property against oxygen and water vapor such as acrylic resin, and treatment methods can be applied.

Hereinafter, the present invention will be described more specifically with reference to examples.
Example 1
By a silk screen printing method on a biaxially stretched PET substrate having a thickness of 100 μm and a size of 500 mm × 500 mm, 5 parts by weight of Byron 200 (manufactured by Toyobo Co., Ltd.) (polyester binder resin) is DBE (DuPont). A conductive paste in which 67.5 parts by mass of silver powder having a particle diameter of 5 μm was uniformly dispersed in a solution dissolved in 27.5 parts by mass of a dibasic acid ester (solvent) manufactured by a company was printed in a lattice pattern. This was dried with hot air at 120 ° C. to evaporate DBE, and on a PET substrate, a lattice pattern with a line width of 30 μm, a pitch of 150 μm, and a thickness of 15 μm had a porosity of 41% (mercury porosimeter (manufactured by Shimadzu Corporation). An intermediate member on which a metal fine particle binder as measured in Autopore IV9520) was formed was obtained. Subsequently, this was impregnated in an electroless copper plating solution (ATS Adcopper IW) manufactured by Okuno Pharmaceutical Co., Ltd. and plated for 5 minutes. The thickness of the conductive mesh of the electromagnetic wave shielding member obtained by washing with water and drying was 15 μm, and the surface resistance was 0.02Ω / □. In the conductive mesh, plated copper was present at a ratio of 1.5 parts by mass with respect to 100 parts by mass of silver powder.
When the cellophane (registered trademark) peel test (JIS H8504) was performed on the conductive mesh of the obtained electromagnetic wave shielding member, there was no cohesive failure of the conductive mesh layer.
Example 2
Example 1 except that a conductive paste in which 76 parts by mass of silver powder having a particle size of 1 μm was uniformly dispersed in a solution in which 9 parts by mass of Byron 200 (binder resin) was dissolved in 15 parts by mass of DBE (solvent) was used. Thus, an electromagnetic wave shielding member was produced. Here, the porosity of the metal fine particle binder was 20%. Moreover, the thickness of the conductive mesh of the obtained electromagnetic wave shielding member is 15 μm, the surface resistance is 0.4Ω / □, and the plated copper is a ratio of 1.6 parts by mass with respect to 100 parts by mass of the silver powder in the conductive mesh. Existed.
When the cellophane (registered trademark) peel test was performed on the conductive mesh of the obtained electromagnetic wave shielding member, there was no cohesive failure of the conductive mesh layer.
Example 3
Example 1 except that a conductive paste in which 99 parts by mass of silver powder having a particle size of 3 μm was uniformly dispersed in a solution in which 1 part by mass of Byron 200 (binder resin) was dissolved in 22 parts by mass of DBE (solvent) was used. Thus, an electromagnetic wave shielding member was produced. Here, the porosity of the metal fine particle binder was 75%. Moreover, the thickness of the conductive mesh of the obtained electromagnetic wave shielding member is 15 μm, the surface resistance is 5Ω / □, and the plated copper is present in a proportion of 1.1 parts by mass with respect to 100 parts by mass of the silver powder. did.
When the cellophane (registered trademark) peel test was performed on the conductive mesh of the obtained electromagnetic wave shielding member, there was no cohesive failure of the conductive mesh layer.

Comparative Example 1
Example 1 except that a conductive paste in which 50 parts by mass of silver powder having a particle diameter of 1 μm was uniformly dispersed in a solution in which 30 parts by mass of Byron 200 (binder resin) was dissolved in 20 parts by mass of DBE (solvent) was used. Thus, an electromagnetic wave shielding member was produced. Here, the porosity of the metal fine particle binder was 4%. Moreover, the thickness of the conductive mesh of the obtained electromagnetic wave shielding member is 15 μm, the surface resistance is 157 Ω / □, and the plated copper is present in a ratio of 0.03 parts by mass with respect to 100 parts by mass of the silver powder. did.
When the cellophane (registered trademark) peel test was performed on the conductive mesh of the obtained electromagnetic wave shielding member, there was no cohesive failure of the conductive mesh layer.
Comparative Example 2
Example 1 except that a conductive paste in which 199 parts by mass of silver powder having a particle size of 3 μm was uniformly dispersed in a solution in which 1 part by mass of Byron 200 (binder resin) was dissolved in 200 parts by mass of DBE (solvent) was used. Thus, an electromagnetic wave shielding member was produced. Here, the porosity of the metal fine particle binder was 83%. Moreover, the thickness of the conductive mesh of the obtained electromagnetic wave shielding member is 15 μm, the surface resistance is 83Ω / □, and the plated copper is present in a proportion of 0.5 parts by mass with respect to 100 parts by mass of the silver powder. did.
When the cellophane (registered trademark) peel test was performed on the conductive mesh of the obtained electromagnetic wave shielding member, cohesive failure of the conductive mesh layer occurred.

Claims (5)

  An electromagnetic wave shielding member in which a conductive material is formed in a mesh pattern on a transparent substrate, and the conductive material is formed of conductive fine particles having a porosity of 20 to 80% obtained by binding conductive fine particles with a binder resin. An electromagnetic wave shielding member characterized in that, in the adherend, a plated metal connects the conductive fine particles, and a surface resistance value thereof is 10 Ω / □ or less.   The electromagnetic wave shielding member according to claim 1, wherein the conductive fine particles are metal fine particles of gold, silver, copper, iron, nickel, or aluminum, and the plating metal is gold, silver, copper, chromium, or nickel.   The electromagnetic wave shielding member according to claim 1 or 2, wherein the conductive material is composed of 1 to 50 parts by mass of binder resin and 0.1 to 300 parts by mass of plated metal with respect to 100 parts by mass of conductive fine particles.   On a transparent substrate, a conductive fine particle binder having a porosity of 20 to 80% formed by binding conductive fine particles with a resin binder is formed in a mesh pattern using a printing method, and this is plated. The manufacturing method of the electromagnetic wave shielding member characterized by the above-mentioned.   The printing method is performed on a transparent substrate using a metal paste having a solid content of 60 to 90% and a binder resin of 1 to 50 parts by mass with respect to at least 100 parts by mass of metal fine particles as conductive fine particles, The method for producing an electromagnetic wave shielding member according to claim 4, wherein the solvent is dried.