JP2008066574A - Electromagnetic wave shield film and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing an electromagnetic shielding film capable of being simply manufactured without using means with a large environmental load such as a plating method, and to provide an electromagnetic wave shielding film manufactured by the manufacturing method. <P>SOLUTION: The electromagnetic wave shielding film is yielded by forming a geometrical pattern containing metal particulate on a transparent supporter and making surface resistivity of the geometrical pattern 10<SP>6</SP>Ω/sq. or less by subjecting the formed geometrical pattern to heat treatment. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electromagnetic wave shielding film used for a plasma display device and a manufacturing method thereof.

In a plasma display device, an electromagnetic wave shielding film is attached to the front surface of the display device for the purpose of shielding electromagnetic waves leaking from the front surface of the display device. In order to maintain the display quality of the display device, an electromagnetic shielding film having a conductive grid pattern (hereinafter sometimes referred to as “mesh”) is used on the surface of the transparent substrate.
The lattice-like pattern needs to have sufficient conductivity for shielding electromagnetic waves, and is required to have a small line width for display quality.

In order to form such a lattice pattern, a method of attaching a conductive mesh to a transparent substrate is known (for example, see Patent Document 1). The conductive mesh is made of conductive fibers knitted in a lattice shape. As the conductive fibers, for example, polyester fibers or the like on which a metal thin film is formed are used.
However, the electromagnetic shielding plate using such a conductive mesh needs to use a conductive mesh that is knitted in the manufacturing process. However, since this conductive mesh is easily expanded and contracted, it is not easy to handle. There was a problem. In addition, when the electromagnetic wave shield plate is used as a front protective plate, it is necessary to increase the visible light transmittance. For this purpose, it is necessary to increase the lattice spacing of the conductive mesh and reduce the fiber diameter. Therefore, it was necessary to use a conductive mesh that is more easily expanded and contracted and more difficult to handle. Furthermore, such conductive meshes that are easily stretched and contracted also have a problem that they are likely to be accompanied by a shift in the lattice spacing or distortion of the lattice pattern when bonded to a transparent substrate.

As a method for solving such a problem, a method of bonding an etching sheet obtained by etching a metal foil in a lattice shape to the surface of a transparent substrate is also known (for example, see Patent Document 2).
However, in order to manufacture a front plate applied to a display with a large screen size such as a plasma display or a large cathode ray tube (CRT) using an etching sheet, a metal foil having a large area corresponding to the screen size is formed in a grid pattern. In order to achieve this, a large film forming apparatus (such as a sputtering apparatus) or a large etching apparatus is required. Therefore, it cannot be said that the method can be easily manufactured.

  In addition, a method is known in which a lattice pattern is formed by a printing method using a conductive paint, and then sufficient conductivity is imparted using a plating method (see, for example, Patent Document 3). This method has sufficient conductivity and can obtain a lattice pattern having a considerably small line width.

Furthermore, a method is known in which a fine lattice pattern is formed using a silver salt photography technique, and a sufficient conductivity is imparted thereto using a plating method (see, for example, Patent Document 4). This method is a technique capable of obtaining very excellent conductivity and line width.
JP-A-10-241578 JP 2000-137442 A JP 2004-87904 A JP 2004-221565 A

  However, the method using the above plating method has a complicated process and generates a waste liquid, which has a large environmental load.

  The present invention has been made in view of the above, and a method for producing an electromagnetic shielding film that can be easily produced without using a means having a large environmental load such as a plating method, and an electromagnetic shielding film produced by the production method. It is an object to provide this and to achieve the object.

Specific means for achieving the above object are as follows.
<1> A geometric pattern containing metal fine particles is formed on a transparent support, and the formed geometric pattern is heat-treated so that the surface resistivity of the geometric pattern is 10 ⁶ Ω / □ or less. It is the electromagnetic wave shielding film produced by.

<2> The electromagnetic wave shielding film according to <1>, wherein the metal fine particles have an average particle diameter of 5 nm to 500 nm.
<3> The electromagnetic wave shielding film according to <1> or <2>, wherein the transparent support is a polyester support.

<4> A geometric pattern forming step of forming a geometric pattern containing metal fine particles on a transparent support, and heat-treating the formed geometric pattern, thereby reducing the surface resistivity of the geometric pattern to 10 ^6. It is a manufacturing method of the electromagnetic wave shielding film which has a heat treatment process made into below omega / square.

<5> The geometric pattern forming step includes a photosensitive layer forming step of forming a photosensitive layer containing metal fine particles on a transparent support, an exposure step of exposing the formed photosensitive layer, and a photosensitive layer after exposure. The method for producing an electromagnetic wave shielding film according to <4>, further comprising a development step of performing alkali development.
<6> The photosensitive layer further contains a binder (preferably containing at least one of an alkali-soluble polymer, a monomer, and an oligomer), and a photopolymerization initiator and / or a photopolymerization initiator system. It is the manufacturing method of the electromagnetic wave shielding film as described in <5>.

<7> The method for producing an electromagnetic wave shielding film according to <4>, wherein the geometric pattern forming step includes a printing step of printing on a transparent support using an ink containing metal fine particles. is there.
<8> The method for producing an electromagnetic wave shielding film according to <7>, wherein the ink further contains a binder.

<9> The method for producing an electromagnetic wave shielding film according to any one of <4> to <8>, wherein an average particle diameter of the metal fine particles is 5 nm to 500 nm.
<10> The method for producing an electromagnetic wave shielding film according to any one of <4> to <9>, wherein the transparent support is a polyester support.

  According to the present invention, it is possible to provide a method for producing an electromagnetic wave shielding film that can be easily produced without using a means having a large environmental load such as a plating method, and an electromagnetic wave shielding film produced by the production method. it can.

Hereinafter, the electromagnetic wave shielding film of the present invention and the manufacturing method thereof will be described in detail.
≪Electromagnetic wave shielding film and manufacturing method thereof≫
The method for producing an electromagnetic wave shielding film of the present invention includes a geometric pattern forming step for forming a geometric pattern containing metal fine particles on a transparent support, and heat treatment of the formed geometric pattern. And a heat treatment step for setting the surface resistivity of the pattern to 10 ⁶ Ω / □ or less.
Moreover, the electromagnetic wave shielding film of this invention is produced by the said manufacturing method.
Hereinafter, the surface resistivity of the geometric pattern, the geometric pattern forming process, the heat treatment process, and the like will be described in detail.

<Surface resistivity of geometric pattern>
In the present invention, the surface resistivity is a value obtained by converting a resistance value against a current flowing on the surface of a substance per 1 cm of a sample width and 1 cm of a length. The surface resistivity measurement method and the like are described in, for example, “Static Handbook, edited by the Electrostatic Society, published by Ohmsha, 1998”.
In the present invention, the direction of the “length” of the sample refers to a direction parallel to a straight line connecting two points used for measuring the surface resistivity in the plane of the sample, and the direction of the “width” of the sample. Denotes a direction perpendicular to the direction of the “length” in the plane of the sample.

The surface resistivity of the geometric pattern in the present invention can be measured using, for example, a solid sample for measuring surface resistivity made of the same material as the geometric pattern. Here, a solid film (non-patterned thin film) formed to have a length of 110 cm, a width of 40 cm, and a film thickness of 0.4 μm is used as the solid sample.
In the measurement of the surface resistivity, first, two copper electrodes having a rectangular bottom shape with a width of 2 mm * a length of 1 mm are pressed against the surface of the solid sample at a pressure of 500 g at intervals of 100 cm. Next, the current value when a voltage of 100 V is applied to the two electrodes is measured, and the resistance value is obtained using the Ohm law. By multiplying the obtained resistance value by 1/500, the surface resistivity in the present invention can be obtained.
In addition, said measurement shall be performed in the same atmosphere, after previously storing the solid sample for surface resistivity measurement in the atmosphere of 25 degreeC and 30% RH, and storing it for 24 hours.

In the present invention, the surface resistivity of the geometric pattern after the heat treatment step described below needs to be 10 ⁶ Ω / □ or less, preferably 10 ² Ω / □ or less, More preferably, it is 10 ¹ Ω / □ or less. If the surface resistivity exceeds 10 ⁶ Ω / □, the ability to leak static electricity or shield electromagnetic waves may be insufficient.
In addition, by setting the surface resistivity to 10 ⁶ Ω / □ or less, it is possible to produce an electromagnetic wave shielding film having a geometric pattern with a small line width (for example, a preferable lattice pattern described later).

<Geometric pattern formation process>
The manufacturing method of the electromagnetic wave shielding film of this invention has a geometric pattern formation process which forms the geometric pattern containing a metal microparticle on a transparent support body.
The geometric pattern is not particularly limited as long as it is a geometric pattern formed on a transparent support, but from the viewpoint of suppressing the decrease in the transmittance of the display device and maintaining good display quality, for example, A lattice pattern having a line width of 3 to 100 μm and a lattice interval of 40 to 1000 μm is preferable.
The geometric pattern contains at least one metal fine particle, but preferably contains a binder as the other component. Furthermore, you may contain a photoinitiator and / or a photoinitiator system, surfactant, a dispersing agent etc. as needed. The binder here refers to a polymer, a monomer that is polymerized to become a polymer, and an oligomer that is polymerized to become a polymer.

(Metal fine particles)
The “metal fine particles” in the present invention are metal or alloy fine particles. The metals and alloys are described on pages 327 and 417 of the 4th edition of Iwanami Physical and Chemical Dictionary (published by Iwanami Shoten in 1987), respectively.
Metal fine particles and alloy fine particles that can be preferably used in the present invention include platinum, gold, silver, palladium, copper, nickel, tin, titanium, platinum / gold alloy, gold / silver alloy, silver / palladium alloy, and silver / tin alloy. And silver / copper alloys. Of these, palladium, silver, copper, silver / palladium alloy, and silver / copper alloy are particularly preferable.
The shape of the metal fine particles used in the present invention is not particularly limited, and a spherical shape, an indeterminate shape, a rod shape, a plate shape, or the like can be used. Of these, amorphous ones are preferable in that the effect of heat treatment is easy.
The particle size of the metal fine particles used in the present invention is preferably in the range of 5 to 500 nm, but more preferably in the range of 10 to 150 nm. When the particle size of the metal fine particles is within the above range, higher conductivity can be stably obtained when heat treatment is performed.
When the shape is other than a spherical shape, a circle having the same area as the image taken by the electron microscope is considered and this diameter is set as the particle size of the particle.

When the geometric pattern of the present invention further contains a binder, the ratio of metal fine particles / binder in the geometric pattern is preferably in the range of 0.4 / 0.6 to 0.9 / 0.1 in volume ratio, A range of 0.5 / 0.5 to 0.75 / 0.25 is more preferable. If the volume ratio is within the above range, conductivity can be obtained more effectively, and the strength of the geometric pattern can be kept higher.
The volume of the metal fine particles here is calculated from the mass and specific gravity.

(Transparent support)
There is no restriction | limiting in particular as a transparent support body in this invention, Well-known support bodies, such as polyester, a polystyrene, a polycarbonate, can be used.
Here, “transparent” means that the minimum value of the light transmittance at a wavelength of 300 nm to 600 nm is 80% or more.
Among these, polyester is preferable, and polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, polybutylene naphthalate, and the like can be used. Among these, polyethylene terephthalate is particularly preferable from the viewpoints of cost and mechanical strength.
The polyester of the present invention is preferably stretched in order to improve mechanical strength, and biaxially stretched is particularly preferable. Although there is no restriction | limiting in particular in a draw ratio, 1.5-7 times, More preferably, about 2-5 times are preferable. For example, a biaxially stretched product that is stretched about 2 to 5 times in the longitudinal and transverse directions is preferable. When the draw ratio is within the above range, higher mechanical strength can be obtained, and thickness uniformity can be kept better.
The thickness of the transparent support of the present invention is preferably 30 to 400 μm, more preferably about 35 to 350 μm. If the thickness of the transparent support is within the above range, the dimensional stability can be kept better, which is advantageous in terms of cost.

(Undercoat layer)
In the present invention, it is preferable to provide an undercoat layer between the transparent support and the geometric pattern from the viewpoint of improving the adhesiveness with the geometric pattern.
As the undercoat layer, those using a rubber polymer such as SBR, an acrylic polymer, a polyester polymer, a polyurethane polymer or the like as a binder are preferable.
For the undercoat layer, if necessary, crosslinking agents such as isocyanate, epoxy, oxazoline, carbodiimide, fine particles such as silica, polymethyl methacrylate, polystyrene, nonionic, anionic, betaine, and cationic surfactants In addition, other known slip agents, charge control agents, dyes, and the like may be added.
The undercoat layer can be provided, for example, by coating on a support. The method for providing the undercoat layer is not particularly limited, and a method similar to the method for forming the photosensitive layer described later can be used.

The method for forming the geometric pattern is not particularly limited, but there are a method of forming by a photolithography method using a photosensitive layer containing metal fine particles, a method of forming by a printing method using ink containing metal fine particles, and the like. Can be mentioned. Among the above, the method of forming a geometric pattern by photolithography is particularly preferable in that a fine pattern can be easily formed.
Hereinafter, a method for forming a geometric pattern by a photolithography method and a method for forming a geometric pattern by a printing method will be described.

(Geometric pattern formation by photolithography method)
When forming a geometric pattern by photolithography, the geometric pattern forming step includes a photosensitive layer forming step of forming a photosensitive layer containing metal fine particles on a transparent support, and an exposure step of exposing the formed photosensitive layer. And a developing step for alkali-developing the exposed photosensitive layer.

-Photosensitive layer formation process-
The photosensitive layer forming step is not particularly limited. For example, a photosensitive composition containing at least one metal fine particle is coated on a transparent support by a known coating method, and dried to form the photosensitive layer. Can be formed. In this invention, it is preferable to apply | coat with the slit-shaped nozzle which has a slit-shaped hole in the part which discharges a liquid. Specifically, JP-A-2004-89851, JP-A-2004-17043, JP-A-2003-170098, JP-A-2003-164787, JP-A-2003-10767, JP-A-2002-79163. Slit nozzles and slit coaters described in Japanese Patent Laid-Open No. 2001-310147 and the like are preferably used.

The photosensitive layer (or photosensitive composition) preferably further contains a binder, a photopolymerization initiator and / or a photopolymerization initiator system, in addition to the metal fine particles. The binder that can be contained in the photosensitive layer (or photosensitive composition) more preferably contains at least one of an alkali-soluble polymer, a monomer, and an oligomer.
Hereafter, each said component is demonstrated.

(1) Alkali-soluble polymer As an alkali-soluble polymer, the polymer which has polar groups, such as a carboxylic acid group and a carboxylate group, in a side chain is preferable. Examples thereof include JP-A-59-44615, JP-B-54-34327, JP-B-58-12577, JP-B-54-25957, JP-A-59-53836, and JP-A-59-53836. A methacrylic acid copolymer, an acrylic acid copolymer, an itaconic acid copolymer, a crotonic acid copolymer, a maleic acid copolymer, a partially esterified maleic acid copolymer as described in JP-A-59-71048 A coalescence etc. can be mentioned. Moreover, the cellulose derivative which has a carboxylic acid group in a side chain can also be mentioned. In addition, a polymer having a hydroxyl group added to a cyclic acid anhydride can also be preferably used. Further, as particularly preferred examples, copolymers of benzyl (meth) acrylate and (meth) acrylic acid described in US Pat. No. 4,139,391, benzyl (meth) acrylate, (meth) acrylic acid and other monomers And a multi-component copolymer. These polymers having a polar group may be used alone, or may be used in the state of a composition used in combination with an ordinary film-forming polymer.

(2) Monomer and / or oligomer The monomer and / or oligomer is preferably a monomer and / or oligomer that has two or more ethylenically unsaturated double bonds and undergoes addition polymerization upon irradiation with light. Examples of such monomers and / or oligomers include compounds having at least one addition-polymerizable ethylenically unsaturated group in the molecule and having a boiling point of 100 ° C. or higher at normal pressure. Examples include monofunctional acrylates and monofunctional methacrylates such as polyethylene glycol mono (meth) acrylate, polypropylene glycol mono (meth) acrylate and phenoxyethyl (meth) acrylate; polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) ) Acrylate, trimethylolethane triacrylate, trimethylolpropane tri (meth) acrylate, trimethylolpropane diacrylate, neopentyl glycol di (meth) acrylate, pentaerythritol tetra (meth) acrylate, pentaerythritol tri (meth) acrylate, di Pentaerythritol hexa (meth) acrylate, dipentaerythritol penta (meth) acrylate, hexane Multifunctional such as all di (meth) acrylate, trimethylolpropane tri (acryloyloxypropyl) ether, tri (acryloyloxyethyl) isocyanurate, tri (acryloyloxyethyl) cyanurate, glycerin tri (meth) acrylate, trimethylolpropane and glycerin Polyfunctional acrylates and polyfunctional methacrylates such as those obtained by adding ethylene oxide or propylene oxide to alcohol and then (meth) acrylated can be mentioned.

Further, urethane acrylates described in JP-B-48-41708, JP-B-50-6034 and JP-A-51-37193; JP-A-48-64183, JP-B-49-43191 Polyfunctional acrylates and methacrylates such as polyester acrylates and epoxy acrylates which are reaction products of epoxy resin and (meth) acrylic acid can be mentioned.
Among these, trimethylolpropane tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, and dipentaerythritol penta (meth) acrylate are preferable.
In addition, “polymerizable compound B” described in JP-A-11-133600 can also be mentioned as a preferable example.

  These monomers and / or oligomers may be used alone or in admixture of two or more. The content of the photosensitive layer (or photosensitive composition) with respect to the total solid content is generally 5 to 50% by mass. 10 to 40% by mass is preferable. The total content of the monomer and / or oligomer and the alkali-soluble polymer is preferably 30 to 90% by mass with respect to the total solid content of the photosensitive layer (or photosensitive composition). 40-80 mass% is more preferable, and 50-70 mass% is especially preferable. The ratio of (monomer and / or oligomer) / (alkali-soluble polymer) is preferably 0.5 to 1.2, more preferably 0.55 to 1.1, and particularly preferably 0.6 to 1.0. .

(3) Photopolymerization initiator and / or photopolymerization initiator system As the photopolymerization initiator and / or photopolymerization initiator system in the present invention, vicinal polyketalide disclosed in US Pat. No. 2,367,660 is disclosed. Nyl compounds, acyloin ether compounds described in US Pat. No. 2,448,828, aromatic acyloin compounds substituted with α-hydrocarbons described in US Pat. No. 2,722,512, US Pat. No. 3,046,127 And a polynuclear quinone compound described in U.S. Pat. No. 2,951,758, a combination of a triarylimidazole dimer and p-aminoketone described in U.S. Pat. No. 3,549,367, and a benzothiazole compound described in Japanese Patent Publication No. 51-48516 And trihalomethyl-s-triazine compounds, U.S. Pat. No. 4,239,850 That are covered trihalomethyl - triazine compound include a trihalomethyl oxadiazole compounds described in U.S. Pat. No. 4,212,976. In particular, trihalomethyl-s-triazine, trihalomethyloxadiazole, and triarylimidazole dimer are preferable.
In addition, “polymerization initiator C” described in JP-A-11-133600 can also be mentioned as a preferable example.
These photopolymerization initiators and / or photopolymerization initiator systems may be used singly or as a mixture of two or more types, but it is particularly preferable to use two or more types. When at least two kinds of photopolymerization initiators are used, the polymerization can be promoted more effectively.
The content of the photopolymerization initiator and / or photopolymerization initiator system with respect to the total solid content of the photosensitive layer (or photosensitive composition) is generally 0.5 to 20% by mass, and 1 to 15% by mass. % Is preferred.

In addition, although the above-mentioned thing is used as this photoinitiator, Among these, as a high exposure sensitivity, the combination of a diazole type photoinitiator and a triazine type photoinitiator is mentioned, Among them, 2-trichloromethyl-5- (p-styrylmethyl) -1,3,4-oxadiazole and 2,4-bis (trichloromethyl) -6- [4- (N, N-diethoxycarbonyl) The combination of (methyl) -3-bromophenyl] -s-triazine is the best. The ratio of these photoinitiators is a diazole / triazine mass ratio, preferably 95/5 to 20/80, more preferably 90/10 to 30/70, most preferably 80/20 to 60 /. 40.
These photopolymerization initiators are described in JP-A-1-152449, JP-A-1-254918, and JP-A-2-153353.
Moreover, the same effect is acquired also by mixing a coumarin type compound with the said photoinitiator. As the coumarin compound, 7- [2- [4- (3-hydroxymethylpiperidino) -6-diethylamino] triazinylamino] -3-phenylcoumarin is the best. The ratio of these photopolymerization initiator and coumarin compound is the mass ratio of photopolymerization initiator / coumarin compound, preferably 20/80 to 80/20, more preferably 30/70 to 70/30, most preferably. Is 40/60 to 60/40.

(4) Other Additives The photosensitive layer further includes known dispersants and other additives described in JP-A-2006-23696 (solvents, surfactants, thermal polymerization inhibitors, ultraviolet absorbers, Etc.).

-Exposure process and development process-
The exposure step is a step of exposing the photosensitive layer formed on the transparent support in the photosensitive layer forming step.
Specifically, a predetermined mask is disposed above the photosensitive layer formed on the transparent support, and the photosensitive layer is exposed from above the mask through the mask. As a light source for exposure, any light source capable of irradiating light in a wavelength region capable of curing the photosensitive layer (for example, 365 nm, 405 nm, etc.) can be appropriately selected and used. Specifically, an ultrahigh pressure mercury lamp, a high pressure mercury lamp, a metal halide lamp, etc. are mentioned. As an exposure amount, it is about 5-5000 mJ / cm < ² > normally, Preferably it is about 10-1000 mJ / cm < ² >.

The development step is a step of alkali developing the photosensitive layer exposed in the exposure step (for example, using a developer).
The developer can be used without particular limitation as long as the transparent support is low in solubility, and for example, a known developer such as that described in JP-A-5-72724 can be used. Can do. In addition, the developer preferably has a photosensitive layer that exhibits a dissolution type development behavior. For example, a developer containing a compound having a pKa of 7 to 13 at a concentration of 0.05 to 5 mol / L is preferable, but is further miscible with water. A small amount of an organic solvent having
Examples of organic solvents miscible with water include methanol, ethanol, 2-propanol, 1-propanol, butanol, diacetone alcohol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol mono-n-butyl ether, and benzyl alcohol. , Acetone, methyl ethyl ketone, cyclohexanone, ε-caprolactone, γ-butyrolactone, dimethylformamide, dimethylacetamide, hexamethylphosphoramide, ethyl lactate, methyl lactate, ε-caprolactam, N-methylpyrrolidone and the like. The concentration of the organic solvent is preferably 0.1% by mass to 30% by mass.
Further, a known surfactant can be further added to the developer. The concentration of the surfactant is preferably 0.01% by mass to 10% by mass.

As a development method, any of paddle development, shower development, shower & spin development, dip development and the like may be used.
Here, the shower development will be described. The uncured portion can be removed by spraying a developer onto the exposed photosensitive layer by shower. Further, after the development, it is preferable to remove the development residue while spraying a cleaning agent or the like with a shower and rubbing with a brush or the like.
The liquid temperature of the developer is preferably 20 ° C. to 40 ° C., and the pH of the developer is preferably 8 to 13.

After the development step and before the heat treatment step, post-exposure may be performed from the viewpoint of increasing the degree of polymerization.
The post-exposure can be performed by exposing the entire surface using a super high pressure mercury lamp or the like from above the surface of the transparent support on which the geometric pattern is formed. Moreover, you may expose from both surfaces of a transparent support body.
In this case, the post exposure amount is preferably 100 to 800 mJ / cm ² .

(Geometric pattern formation by printing method)
When forming a geometric pattern by a printing method, the geometric pattern forming step includes a printing step of printing on a transparent support using an ink containing metal fine particles (and preferably a binder). The
The printing method is not particularly limited, and a known printing method can be used. For example, a gravure printing method, a screen printing method, and the like are preferable.

As the binder that can be contained in the ink, for example, the polymer described in the above “-photosensitive layer forming step” can be suitably used.
Further, the ink further contains a known dispersant and other additives described in JP-A-2006-23696 (solvent, surfactant, thermal polymerization inhibitor, ultraviolet absorber, etc.). May be.

<Heat treatment process>
In the present invention, the geometric pattern formed on the transparent support by the geometric pattern forming step described above is used in order to impart conductivity to the geometric pattern and make the surface resistivity 10 ⁶ Ω / □ or less. A heat treatment step for heat treatment is required.

For the heat treatment in the present invention, a known method such as a method using an infrared heater or a heating roll or a method of exposing to a heated atmosphere can be used.
The heat treatment conditions vary depending on the material of the support and the type of metal fine particles, but are in the range of 150 to 450 ° C., more preferably 180 ° C. to 350 ° C., 10 seconds to 20 minutes, more preferably 20 seconds to 5 minutes. Preferably it is done. If the conditions of heat processing are in the said range, electroconductivity can be expressed more effectively, damage to the support body by heat | fever can be suppressed more, and the preparation time of an electromagnetic wave shield film can be shortened more.

  Further, in the present invention, at least the pattern containing the metal fine particles may be heat-treated. Therefore, in order to prevent thermal damage to the transparent support, the back surface (the surface on which the geometric pattern is formed among the surfaces of the transparent support) The geometric pattern may be heat-treated while the transparent support is cooled from the opposite surface.

From the viewpoint of suppressing thermal damage of the transparent support more effectively among the above conditions,
As a transparent support, a polyester support having a thickness of 35 to 350 μm, particularly a polyethylene terephthalate support, is used. As a treatment in the heat treatment step, a back surface of the transparent support (transparent support) Of these surfaces, a mode in which heat treatment is performed for 10 seconds to 20 minutes in a thermostatic bath at 180 to 350 ° C. in a state of being in close contact so that the surface opposite to the surface on which the geometric pattern is formed is in contact is preferable. .

<Others>
In the electromagnetic wave shielding film and the manufacturing method thereof of the present invention, the above-described conditions and materials can be appropriately selected and used from the viewpoint of more effectively achieving the effects of the present invention.

  For example, from the viewpoint of more effectively suppressing the thermal damage of the transparent support, maintaining the strength of the geometric pattern, and reducing the surface resistivity, the transparent support is a polyester support having a thickness of 35 to 350 μm, particularly polyethylene. A terephthalate support is used, silver particles having a particle size of 10 to 150 nm are used as metal fine particles, an alkali-soluble acrylic polymer is used as a binder, and the volume ratio of metal fine particles / binder is 0.5 / 0.5 to 0.75 / 0. .25, a geometric pattern is formed on the transparent support, and as a heat treatment process, a cooling roll cooled to 0 to 40 ° C. is placed on the back surface of the transparent support. In a state where it is in close contact so that the surface opposite to the surface on which the geometric pattern is formed is in contact, it is placed in a thermostatic bath at 180 to 350 ° C. for 10 seconds to 20 minutes. Manner of performing are particularly preferred.

A protective layer may be provided on the geometric pattern.
As the protective layer, for example, a layer using polyvinyl alcohol as a binder can be used.

The electromagnetic wave shielding film of the present invention can be used for plasma display devices of various sizes.
Especially, it is suitable for the use of a large display device of 32 inches or more, and is particularly suitable for the use of a plasma display of 40 inches or more.

  EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited to these Examples. In the examples, “%” is based on mass.

[Example 1]
An undercoat layer coating solution having the following composition is applied to one side of a biaxially stretched polyethylene terephthalate support with a thickness of 100 μm by wet application of 4.4 cc / m ² and dried at 180 ° C. for 5 minutes to form an undercoat layer. did.

<Composition of coating solution for undercoat layer>
Polyester resin binder (Dainippon Ink & Chemicals, Finetex ES-650, solid content 29%) ... 40.5 parts by mass Surfactant A (Sanyo Chemical Industries, Sandet BL, 9.0 mass parts / surfactant B (Sanyo Kasei Kogyo Co., Ltd., NAROACTY HN-100, solid content 5%, nonionic) ... 15.5 mass Parts / silica fine particle dispersion (manufactured by Nippon Aerosil Co., Ltd., OX-50 aqueous dispersion, solid content 10%)... 2.3 mass parts / colloidal silica dispersion (Nissan Chemical Co., Ltd., Snowtex) -XL, solid content 10%) ... 3.0 parts by mass, slip agent (manufactured by Chukyo Yushi Co., Ltd., carnauba wax dispersion cellosol 524, solid content 3%) ... 7.6 parts by mass, distilled water ... 922.1 parts by mass

  On the undercoat layer formed above, a photosensitive layer coating solution having the following composition was applied so that the dry film thickness was 0.4 μm, and then dried at 100 ° C. for 5 minutes to form a photosensitive layer. A photosensitive material having an undercoat layer and a photosensitive layer in this order on a transparent support was obtained.

<Composition of photosensitive layer coating solution>
Monomer (dipentaerythritol hexaacrylate) 15 parts by mass Polymer (styrene / methacrylic acid = 70/30 (molar ratio), weight average molecular weight 18,000) 15 parts by mass Silver nanoparticles ( Acetone solution (solid content 60% by mass)
... 1225 parts by mass / initiator (2,4-bis (trichloromethyl) -6- [4- (N, N-diethoxycarbonylmethyl) -3-bromophenyl] -s-triazine) 0 .45 parts by mass · Fluorosurfactant (Dainippon Ink Chemical Co., Ltd., MegaFuck F780F, 30% by weight methyl ethyl ketone solution) ... 1.0 part by mass

The photosensitive layer of the photosensitive material thus obtained was exposed through a mask with an ultrahigh pressure mercury lamp at an exposure amount of 500 mJ / cm ² . Subsequently, development was performed at 35 ° C. for 20 seconds using an alkaline developer (Fuji Photo Film Co., Ltd. CD-1) to form a lattice pattern (geometric pattern) having a line width of 7 μm and a lattice spacing of 50 μm.
Thereafter, the sample on which the geometric pattern is formed is in close contact with the cooling roll cooled to 25 ° C. so that the back surface of the sample (the surface opposite to the surface on which the lattice pattern is formed) is in contact. It put into the 280 degreeC thermostat and heat-processed for 5 minutes, and obtained the electromagnetic wave shield film.

Separately, a solid sample for measuring the surface resistivity was prepared in the same manner as the method for producing the electromagnetic wave shielding film except that the exposure (entire exposure) was performed without using a mask, and the surface resistivity was measured by the following method. did. The solid film in the solid sample had a length of 110 cm, a width of 40 cm, and a film thickness of 0.4 μm.
First, two copper electrodes having a rectangular bottom shape with a width of 2 mm * length of 1 mm were pressed against the sample surface at a pressure of 500 g at intervals of 100 cm. Next, the current value when a voltage of 100 V was applied to the two electrodes was measured, and the resistance value was obtained using the Ohm law.
However, the measurement atmosphere was 25 ° C. and 30% RH, and a solid sample was stored at this temperature and humidity for 24 hours before measurement. The value thus obtained was 1/500 to obtain the surface resistivity.
The surface resistivity determined as described above was 7.1Ω / □.

[Example 2]
Instead of “silver nanoparticles (amorphous particles having an average particle size of 15 nm) in acetone solution (solid content 60% by mass) 1225 parts by mass” contained in the coating solution for the photosensitive layer in Example 1, “silver nanoparticles” An electromagnetic wave shielding film was produced in the same manner as in Example 1 except that 1558 parts by mass of an acetone solution (solid content: 54% by mass) of (amorphous particles having an average particle size of 13 nm) was used. It was 9.8 ohms / square when the surface resistivity of the obtained electromagnetic wave shielding film was measured by the method similar to Example 1. FIG.

[Comparative Example 1]
In Example 1, an electromagnetic wave shielding film was produced in the same manner as in Example 1 except that the heat treatment after forming the lattice pattern was not performed. When the surface resistivity of the obtained electromagnetic wave shielding film was measured by the same method as in Example 1, it exceeded the measurement limit (10 ¹⁴ Ω / □) of the measuring apparatus and could not be measured.

Claims (10)

It is produced by forming a geometric pattern containing metal fine particles on a transparent support, and heat-treating the formed geometric pattern so that the surface resistivity of the geometric pattern is 10 ⁶ Ω / □ or less. Electromagnetic shielding film.   2. The electromagnetic wave shielding film according to claim 1, wherein the metal fine particles have an average particle diameter of 5 nm to 500 nm.   The electromagnetic wave shielding film according to claim 1, wherein the transparent support is a polyester support. A geometric pattern forming step for forming a geometric pattern containing metal fine particles on a transparent support, and a heat treatment of the formed geometric pattern results in a surface resistivity of the geometric pattern of 10 ⁶ Ω / □. The manufacturing method of the electromagnetic wave shielding film which has the heat processing process made below.   In the geometric pattern forming step, a photosensitive layer forming step of forming a photosensitive layer containing metal fine particles on a transparent support, an exposure step of exposing the formed photosensitive layer, and an alkali development of the exposed photosensitive layer The method for producing an electromagnetic wave shielding film according to claim 4, further comprising a developing step.   6. The method for producing an electromagnetic wave shielding film according to claim 5, wherein the photosensitive layer further contains a binder and a photopolymerization initiator and / or a photopolymerization initiator system.   The method for producing an electromagnetic wave shielding film according to claim 4, wherein the geometric pattern forming step includes a printing step of printing on a transparent support using an ink containing metal fine particles.   The method for producing an electromagnetic wave shielding film according to claim 7, wherein the ink further contains a binder.   The method for producing an electromagnetic wave shielding film according to any one of claims 4 to 8, wherein an average particle diameter of the metal fine particles is 5 nm to 500 nm.   The said transparent support body is a polyester support body, The manufacturing method of the electromagnetic wave shield film of any one of Claims 4-9 characterized by the above-mentioned.