KR101160731B1 - Electromagnetic wave shielding film and method for producing same - Google Patents

Abstract

The present invention relates to an electromagnetic wave blocking film and a method of manufacturing the same. The electromagnetic wave blocking film is a conductive thin film comprising a support and a filament grid thereon, wherein the filament grid is formed of metal silver and metal copper plated on the metal silver, wherein the amount of the metal copper is equal to the total mass of the silver and copper. 55-90 mass%, the line width of the grid is 5-25 µm, the open porosity is 85% -95%, and the surface resistance is 0 or more and 5 Ω / sq or less. The method includes applying a silver salt-containing layer and a protective layer thereof on a support, exposing the layer in a grid pattern, such that the exposed portions form metallic silver portions and the unexposed portions form translucent portions. Performing a development treatment, thickening the metal silver portion, activating the thickened metal silver portion, and then plating the activated metal silver portion with a metal to form a conductive metal portion. The film of the present invention has low surface resistance and excellent shielding effect, and the method for producing the film is simple and suitable for industrial production.

Description

Electromagnetic wave shielding film and method for producing same

The present invention relates to a shielding film, and more particularly to an electromagnetic wave shielding film and a manufacturing method thereof.

In recent years, the informatization of society has been rapidly developed and the equipment related to the information of the world has been rapidly developed and popularized. Various electronic equipment, communication devices and display devices such as CRT, LCD, EL, PDP, FED are widely used in televisions, personal computers and guiding display devices in stations and airports to provide various information. Therefore, electromagnetic interference generated by such electronic devices, electronically controlled game machines (such as pachinko (ie, a kind of gambling pinball machine) and automatic gambling machines) as well as communication devices such as mobile phones (EMI) ) Causes more and more serious problems.

Electromagnetic disturbances affect the accuracy of the operation of adjacent electronic equipment, cause malfunctions and adversely affect human health. Therefore, the requirements for electromagnetic shielding materials have become increasingly strict. In order to satisfy such requirements, various transparent conductive films (electromagnetic shielding films) have been developed. For example, various shielding films are disclosed in JP9-53030, JP11-126024, JP2000-294980, JP-2000-357414, JP2000-329934, JP2001-38843, JP2001-47549, JP2001-51610, JP2001-57110 and JP2001-60416. However, all these shielding films generally have shielding efficiency deficiencies.

In these electromagnetic wave shielding film material manufacturing methods, methods such as a sputtering method, an etching method and a silver salt diffusion transfer method are generally employed. Sputtering refers to a method in which a material used to form a layer having a high refractive index, such as metallic silver and indium tin oxide (ITO), is directly sputtered onto a glass substrate or a PET film which is subsequently bonded to the glass substrate. The application of electromagnetic shielding films made according to the sputtering method is limited and not widely used because of the low transmittance and relatively high surface resistance of the films. Etching refers to a method in which a copper foil is laminated with a transparent thin PET film and the foil is then subjected to a photolithography process to obtain a copper grid consisting of a mesh formed by filaments. The etching process is complicated and expensive. The silver salt diffusion transfer method involves applying a catalytic nuclei such as palladium and rhodium to a transparent thin PET film, applying a silver halide emulsion thereon, performing physical development, and then copper or nickel. The method of forming a metal film by plating. Since the residues of the catalyst nuclei absorb light, the film formed by the silver salt diffusion transfer method has problems such as low transmittance.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an electromagnetic shielding film having low surface resistance and high shielding efficiency.

Still another object of the present invention is to provide a method of manufacturing the electromagnetic wave shielding film of the present invention.

In order to achieve the above object, the present invention provides the following technical solution.

The present invention provides an electromagnetic shielding film, which is a conductive thin film consisting of a support and a filament grid on the support, the filament grid being formed of metal silver and metal copper plated on the metal silver, wherein the amount of the metal copper is silver And 55-90 mass% of the total mass of copper, the line width of the grid is 5-25 μm, the open porosity is 85% -95%, and the surface resistance is 0 or more and 5 Ω / sq or less. do.

The filament grid of the electromagnetic shielding film has a thickness of 2.5-8 μm.

The invention also provides a method of making an electromagnetic wave shielding film, which comprises applying a silver salt-containing layer and a protective layer thereof on a support, exposing the silver salt-containing layer and the protective layer in a grid pattern, Performing development such that the exposed portion forms a metallic silver portion, and the unexposed portion forms a light-transmitting portion, thickening the metallic silver portion, thickening metallic silver Activating the portion, and then plating the activated metal silver portion with copper to form a conductive metal portion, wherein the amount of metal copper is 55-90 mass% of the total mass of silver and copper.

According to the method the thickening of the metallic silver part is carried out with silver or copper.

According to the method the activation step is carried out using an aqueous solution of heavy metal ions.

According to the method the activation step is carried out using an aqueous solution of palladium ions, gold ions or silver ions.

According to the method the plating with copper is carried out by a chemical plating process.

Supports applicable to the present invention include polyethylene terephthalate resin, diacetate resin, triacetate resin, polyethylene, polypropylene, polystyrene, polyvinyl chloride resin, poly (ether-ketone), polysulfone, poly (ether-sulfone) It may be a single-layer or multi-layer thin film formed from one or more materials selected from the group consisting of polycarbonate, polyamide, acrylic resin, cellulose triacetate and the like. In view of all factors such as light transmittance, heat resistance and cost, polyethylene terephthalate (PET) films are most preferred to be used to form supports (also called "substrates").

Silver halide emulsions useful in the present invention may be prepared according to any of the methods for preparing silver halide emulsions in the field of photosensitive photographic materials. Silver halide emulsions are generally prepared by mixing and emulsifying an aqueous solution of silver nitrate with an aqueous solution of a halide such as sodium chloride or potassium bromide in the presence of gelatin.

In the silver halide composition applicable to the present invention, silver chloride is preferred, that is, the composition may contain at least 50% chloride ions, which may also contain iodine ions and bromine ions. The particle size of the silver halide is preferably 0.1-1000 nm, more preferably 1-200 nm. The shape of the silver halide crystal is not particularly limited and may be cube, octahedral or spherical or flat granular; Or silver chloride is a twin crystal with a flaky shape.

To achieve higher contrast, metal ions, in particular transition metal ions such as rhodium and iridium, need to be doped in a silver halide emulsion. Rhodium and iridium ions can form coordination compounds with different ligands, including cyanide ions, halogen ions, thiocyanate ions, nitrosyl ions, water and hydroxide ions. The content of metal ions is preferably 10 ^-10 -10 ^-2 moles per mole of silver, and more preferably 10 ^-9 -10 ^-3 per mole of silver.

In the present invention, the silver salt-containing layer and the protective layer may be any one such as dip coating, extrusion coating, slide coating, curtain coating, rod coating, air knife coating, roller coating, photogravure coating or spray coating, and the like. It can be formed by coating means. Continuous and uniform coatings in the present invention are obtained by employing the coating means.

The exposure light source applicable to the present invention may be a UV lamp or a high pressure mercury lamp or the like. The grid pattern may be moved to the silver halide film by the light source means, or the grid pattern may be moved to the silver halide film by the laser scanning method.

In the present invention, the silver halide emulsion layer needs to be developed after exposure. General developing techniques used in traditional photographic materials can be used. The developer is not particularly limited, but a developer having high contrast such as commercially available D-19, D-72, D-11, D-8 and G-48 is preferable. After exposure and development, a metal silver portion and a light transmissive portion are formed.

The metal silver portion of the present invention is then plated with metal after the thickening and activation process to form a conductive metal portion. The metal particles for forming the conductive metal portion may be particles of copper, aluminum, nickel, iron, gold, cobalt, palladium and the like. However, in consideration of the conductivity and the cost comprehensively, the conductive metal portion is preferably formed of copper.

The process of thickening applied to the present invention may be a process of thickening silver or a process of thickening copper. The process of thickening silver is a process in which metal silver ions are reduced to metallic silver by a reducing agent in a soluble silver salt solution, whereby fine silver particles are obtained, and the metallic silver obtained therebetween is slowly deposited at an appropriate position. The deposition rate of such metallic silver is much higher in the metal part than in the non-silver transparent part, and basically the amount of silver deposited at one location is proportional to the amount of silver already present at that location. Therefore, in the process of thickening silver, the metallic silver may be plated or deposited on the silver-filament patterned portion without substantially depositing on the transparent portion of the support. The purpose of the process of thickening copper is the same as the purpose of the process of thickening silver, which is to thicken the silver-filament patterned portion. Thickening solutions used in the process of thickening copper include divalent copper ions (Cu ²⁺ ); Acid radical ions such as sulfate ions, nitrate ions, acetate ions and the like; Halogen ions such as chlorine ions, bromine ions and iodine ions. The process of thickening silver or the process of thickening copper is generally carried out at room temperature for 10 seconds to 30 minutes, preferably 1 minute to 20 minutes.

The purpose of the activation process is to generate an active point suitable for chemical copper plating on the surface of the patterned silver filament on the transparent support to accelerate the speed of chemical copper plating. The activation process can be carried out by methods well known in the art, such as a two-step treatment method of sensitization-activation and a colloidal palladium activation method. The two-stage treatment method of sensitization-activation is a method comprising two steps: first aqueous tin chloride solution is used to perform the sensitization treatment, and then an aqueous solution of palladium chloride, gold chloride or silver nitrate is used for the activation treatment. . In the present invention, the activation process can be carried out directly with heavy metal ions, i.e. palladium chloride, gold chloride or silver nitrate, since the metal silver part has been thickened in the previous process of thickening silver or copper thickening.

In the present invention, chemical plating is employed to deposit metal to form conductive metal portions. Traditional chemical plating techniques can be used, such as plating techniques for printed circuit boards. Most preferably the chemical plating is chemical copper plating, which is a process of placing a transparent support in a copper plating bath and performing plating, and since the silver filament has undergone the subsequent treatment, the transparent support is patterned. Has a sufficiently active point on the filament. The copper plating bath for chemical copper plating generally contains copper salts, complexing agents, reducing agents and other additives. The copper salt provides the copper ions to be deposited and soluble copper salts such as copper sulfate, copper acetate or copper chloride can be used. The reducing agent reduces soluble copper ions to metallic copper in the plating bath, and the metallic copper is deposited in a silver filament pattern on a transparent support to form metallic copper plating. Materials such as formaldehyde, sodium borohydride and sodium hypophosphite can be used as reducing agents. Complexing agents are used to transform copper ions into complex ions to prevent the generation and precipitation of cupric hydroxide under alkaline conditions. The formation of complex ions is suitable for smelting metal grains and increasing deposition rates, as well as improving the stability of the solution and the performance of chemical plating. Complexing agents generally include tartrate, EDTA, citrate, triethanolamine, cyclohexanediaminetetraacetic acid, ethylene diamine and the like. One type of complexing agent is generally used but mixtures of complexing agents may also be used. The main disadvantage of chemical copper plating baths is instability, as a result of which stabilizers such as α, α'-bipyridine, tripyridine, thiourea or mercaptobenzothiazole are generally introduced into the plating bath. Also nonionic surfactants or anionic surfactants (such as polyethylene glycol (M = 1000), polyoxyethylene alkylphenol ethers) may be added to improve the performance of the plating.

Formaldehyde is generally used as reducing agent in conventional processes for chemical copper plating; But it is toxic and volatile, which will pollute the environment and harm human health.

Both formaldehyde and sodium hypophosphite have been studied with reducing agents used in the present invention. And as a result, the oxidation reaction of sodium hypophosphite simply occurs at the catalyst surface and the reaction is not promoted by the deposited copper, so that a small amount of nickel ions need to be added to the plating bath as autocatalyst in order to continue the autocatalytic reaction. have.

In the present invention, the metal part after the developing step and the conductive metal part after the plating process need to be further subjected to oxidation treatment. The oxidation treatment, for example, has the effect of removing a small amount of metal deposited on the transparent portion, so that the transparent portion can have a transmittance of almost 100%.

In order to enhance the contrast of the conductive metal parts and at the same time prevent discoloration, the copper surface needs to go through a blackening process. The blackening process can take advantage of the method used in the field of printed circuit boards. For example, the copper surface can be treated in an aqueous solution at 95 ° C. for 2 minutes, the aqueous solution comprising sodium chloride (31 g / L), sodium hydroxide (15 g / L) and trisodium phosphate (12 g / L) do.

In the electromagnetic shielding film produced according to the above method, if the filament width of the filament pattern is decreased and the open porosity is increased, the light transmittance will increase while the conductivity will decrease; On the contrary, if the filament width is increased, the light transmittance will decrease while the conductivity will increase. The filament width is therefore preferably 5-25 μm, and the filaments are preferably arranged in a grid pattern, the filaments intersecting horizontally or vertically with each other.

After plating, the conductive metal part consists mainly of metal copper and metal silver and the remainder is a small amount of metal palladium and / or metal nickel. The content of metal copper amounts to 50-90 mass% with respect to the total amount of metal.

Immediately after plating, the thickness of the filament pattern can be adjusted according to the desired characteristics but is preferably 2.5-8.0 μm. If the thickness is smaller than 2.5 mu m, sometimes the desired surface resistance will not be obtained; And if the thickness is larger than 8.0 mu m, it is acceptable, but it is difficult to obtain the effect of lowering the surface resistance and further decrease the efficiency of the plating process.

 In addition, the electromagnetic shielding film according to the present invention can obtain a shielding effect of 30dB or more in a wide range of 30MHz-1000MHz, or an excellent shielding effect in a frequency band of 1000MHz or more range.

Technical effect

Advantages of the electromagnetic wave shielding film according to the present invention include low surface resistance, excellent shielding effect. The method of manufacturing the electromagnetic shielding film is simple and suitable for industrial production.

The invention is illustrated more specifically below by showing specific examples thereof. However, the scope of the present invention is not limited to the following examples and should not be interpreted.

Example 1

1. Preparation of Silver Halide Emulsion

Silver halide emulsions were prepared according to methods employed in the field of photosensitive photographic materials. The silver halide emulsion comprises silver bromoiodide, the silver bromide content is 98 mol% and the silver iodide content is 2 mol%. The average particle size of the emulsion was 0.09 μm and the emulsion was doped with K ₂ IrCl ₆ and K ₃ RhBr ₆ . Gold-sulfur sensitization of the emulsion was further performed with potassium tetrachloroaurate and sodium thiosulfate. The emulsion was then applied onto a PET film with a silver coating amount of 4.0 g / m ² and then dried.

2. Exposure, development

After coating and drying the samples were exposed to ultraviolet light in a grid mold with a line width / spacing of 285 μm / 15 μm. The following photographic developer is used for later development, and the F-5 fixative is used for further fixation. After fixation the samples were rinsed with deionized water to give a silver grid image with a line width / spacing of 15 μm / 285 μm.

Composition of the developing solution:

100 g of anhydrous sodium sulfite

Hydroquinone 30.0 g

Phenidone 1.5g

Sodium hydroxide 25.0g

3.5 g potassium bromide

1.0 g of benzotriazole

Added so that the total volume of water is 1.0 l

3. Thickening Treatment

First Stock Solution:

Silver Nitrate 91.5g

Added so that the total volume of water is 1.0 l

Second Stock Solution:

Ammonium Thiocyanate 160.0g

Sodium Thiosulfate 160.0g

Added so that the total volume of water is 1.0 l

100 ml of the first stock solution was added to 100 ml of the second stock solution with slow stirring. Then, 25 ml of a 10% pyrogallol solution containing 5-10% sodium sulfite and 50 ml of 10% ammonia was added to obtain a thickening solution. The silver grid sample obtained after the above-described exposure and development process was immersed in the thickening solution for 5.0 minutes and rinsed with water.

4. Activation Treatment

After thickening, the samples were activated for 0.5 minutes in 0.5% aqueous palladium chloride solution and then rinsed with water to undergo chemical copper plating.

5. Chemical Copper Plating

In the following plating baths where the pH was adjusted to 12.5 with sodium hydroxide after activation, the samples were chemically copper plated. The plating was performed at 25 ° C. for 5 minutes, washed with water and then dried to obtain a shielding film sample according to the present invention. The results are shown in Table 1.

Composition of plating bath for chemical copper plating:

ingredient Content (mM / L) Copper sulfate 60 Triethanolamine 180 Potassium Ferrocyanide 0.002 Bipyridine 0.013 Formaldehyde solution 235 Methanol 210

Example 2

1. Preparation of Silver Halide Emulsion

Silver halide emulsions were prepared according to methods employed in the field of photosensitive photographic materials. The silver halide emulsion contains silver chlorobromide, the content of silver chloride is 70 mol% and the content of silver bromide is 30 mol%. The average particle size of the emulsion was 0.23 μm and the emulsion was doped with K ₂ IrCl ₆ and K ₃ RhBr ₆ . Gold-sulfur sensitization of the emulsion was further carried out with potassium tetrachloride and sodium thiosulfate. Then, the emulsion was applied to the PET film with a silver coating amount of 3.0 g / m ² and then dried.

2. Exposure, development

After coating and drying, the samples were exposed to ultraviolet light in a grid mold with a line width / spacing of 200 μm / 12 μm. The following photographic developer is used for later development, and the F-5 fixative is used for further fixation. After fixation the samples were rinsed with deionized water to give a silver grid phase with a line width / spacing of 12 μm / 200 μm.

Developing solution composition:

100 g of anhydrous sodium sulfite

Hydroquinone 12.0 g

Metol 2.0 g

75 g sodium carbonate

4.0 g of potassium bromide

0.02 g of potassium iodide

Added to 1.0 l of water

3. Thickening Treatment

(1) 45 g of copper sulfate

    10 g sodium chloride

    Water 1.0ℓ

45 g of copper sulfate and 10 g of sodium chloride were added to 1.0 L of water, and the mixture was stirred to obtain a thickening solution. The silver grid sample obtained after the exposure and development process was immersed in the thickening solution for 3.0 minutes and rinsed with water.

(2) The following solutions should be used immediately after mixing.

Solution A:

28 g of tin chloride

250 ml of water

Solution B:

22 g sodium hydroxide

750 ml of water

Solution B was added to Solution A just before use and after treatment with the copper solution, the sample obtained was immersed in a mixture of Solution A and Solution B for 3.0 minutes and rinsed with water.

4. Activation Treatment

After thickening, the samples were activated for 2 minutes in an aqueous 2% silver nitrate solution and then rinsed with water to undergo chemical copper plating.

5. Chemical Copper Plating

The process is carried out according to the same process as in Example 1. The results are shown in Table 1.

Example 3

1. Preparation of Silver Halide Emulsion

The manufacturing process was carried out according to the same procedure as in Example 2.

2. Exposure, development

After drying, the samples were exposed to ultraviolet light with a grid mold having a line width / spacing of 320 μm / 25 μm. The developer described in Example 1 is used for subsequent development, and the F-5 fixative is used for further fixing. After fixation the samples were rinsed with deionized water to give a silver grid phase with a line width / spacing of 25 μm / 320 μm.

3. Thickening Treatment

The thickening process is carried out according to the same procedure as in Example 2.

4. Activation Treatment

After thickening, the samples were activated for 3 minutes in 0.1% aqueous palladium chloride solution and then rinsed with water to undergo chemical copper plating.

5. Chemical Copper Plating

Samples were chemically copper plated in the following plating baths with pH adjusted to 9.0 with sodium hydroxide after activation. The plating was carried out at 35 ° C. for 30 minutes, washed with water and then dried to obtain a film sample according to the invention. The results are shown in Table 1.

Composition of plating bath for chemical copper plating

ingredient Content (mM / L) Copper sulfate 24 Sodium citrate 67 Sodium hypophosphite 270 Boric acid 300 Nickel sulfate 2

Example 4

1. Preparation of Silver Halide Emulsion

The manufacturing process was carried out according to the same procedure as in Example 2.

2. Exposure, development

After coating and drying, the samples were exposed to ultraviolet light in a grid mold with a line width / spacing of 200 μm / 5 μm. The developer described in Example 1 is used for subsequent development, and the F-5 fixative is used for further fixing. After fixation the samples were rinsed with deionized water to give a silver grid phase with a line width / spacing of 5 μm / 200 μm.

3. Thickening Treatment

The thickening process is performed according to the same procedure as in Example 1.

4. Activation Treatment

After thickening, the sample was activated for 3 minutes in an aqueous 1% silver nitrate solution and then rinsed with water to allow the sample to undergo chemical copper plating.

5. Chemical Copper Plating

Samples were chemically copper plated in the following plating baths with pH adjusted to 9.5 with sodium hydroxide after activation. The plating was carried out at 40 ° C. for 30 minutes, rinsed with water and then dried to obtain a film sample according to the invention. The results are shown in Table 1.

Composition of plating bath for chemical copper plating

ingredient Content (mM / L) Copper sulfate 50 Sodium citrate 67 Sodium hypophosphite 270 Boric acid 400 Nickel sulfate 2 Bipyridine 0.128

Table 1: Sample Performance

Example Copper content
(mass%) Line width (μm) Open porosity (%) Surface resistance
(Ω / sq) Thickness of grid
(Μm) Example 1 89.5 15 90 0.8 7.9 Example 2 69 12 88 1.2 5.2 Example 3 72 25 86 1.0 4.1 Example 4 55 5 95 4.1 2.5

Performance test method

1. Surface resistance is measured with a resistance tester;

2. The line width of the conductive metal grid of the sample was measured by light microscopy and scanning electron microscopy, and then the open porosity was calculated accordingly.

Claims (10)

A conductive thin film consisting of a support and a filament grid on the support, wherein the filament grid is formed of metal silver and metal copper plated on the metal silver, wherein the amount of the metal copper is 55-90 mass% of the total mass of the silver and copper The line width of the grid is 5-25㎛, the porosity is 85% -95%, the surface resistance is 0 to 5Ω / sq, characterized in that the electromagnetic shielding film. The method according to claim 1, The filament grid of the electromagnetic shielding film has a thickness of 2.5-8㎛ electromagnetic shielding film, characterized in that. The method according to claim 1, The support is polyethylene terephthalate resin, diacetate resin, triacetate resin, polyethylene, polypropylene, polystyrene, polyvinyl chloride resin, poly (ether-ketone), polysulfone, poly (ether-sulfone), polycarbonate, polyamide And a single-layer thin film or a multi-layer thin film formed from at least one of acrylic resin or cellulose triacetate. Applying a silver salt-containing layer and its protective layer on a support, exposing the silver salt-containing layer and the protective layer in a grid pattern, the exposed portion forming a metal silver portion, the unexposed portion being Performing a development treatment to form a light transmissive portion, thickening the metal silver portion, activating the thickened metal silver portion, and then plating the activated metal silver portion with copper to form a conductive metal portion. The method of claim 1, wherein the amount of the metal copper is 55-90 mass% of the total mass of silver and copper. The method of claim 4, And the step of thickening the metal silver portion is performed with silver or copper. The method of claim 4, The activation is characterized in that the electromagnetic wave shielding film production method using an aqueous solution of heavy metal ions. The method of claim 4, The activation step is characterized in that the electromagnetic wave shielding film production method using an aqueous solution of palladium ions, gold ions or silver ions. The method of claim 4, Plating with copper is a method of manufacturing an electromagnetic shielding film, characterized in that performed by a chemical plating process. The method of claim 4, The silver salt-containing layer and protective layer are selected from the group consisting of dip coating, extrusion coating, slide coating, curtain coating, rod coating, air knife coating, roller coating, photogravure coating and spray coating. Method for producing an electromagnetic wave shielding film, which can be formed by a coating means. delete