JP5039315B2 - Electromagnetic wave shielding film and manufacturing method thereof - Google Patents

Description

  The present invention relates to an electromagnetic wave shielding film for shielding electromagnetic waves generated from the front surface of a display device such as a plasma display panel (PDP) and suppressing leakage of the electromagnetic waves to the outside, and a method for manufacturing the same.

  In recent years, the market of various display devices using large and thin display devices such as PDPs (plasma display panels) has been expanding.

  The principle of driving the PDP is that an Xe (xenon) gas sealed in a tube serving as a pixel is excited by being discharged by applying a voltage to an ultraviolet ray in a wide-band wavelength spectrum extending from the ultraviolet to the near infrared region. Excites the phosphor applied in the tube to generate light in the visible region. From the above principle, it is known that the PDP leaks strong electromagnetic waves to the outside during driving.

  Such leakage of electromagnetic waves to the outside is known to cause electromagnetic noise interference (EMI: Electro-Magnetic Interference) such as causing malfunction of electronic equipment in the vicinity of the display device.

  As a method for suppressing leakage of electromagnetic waves from a display device, for example, techniques as disclosed in Patent Documents 1 and 2 below are disclosed.

  Patent Document 1 listed below discloses an electromagnetic wave shielding film formed by bonding a conductive mesh to a transparent resin film surface via an adhesive.

Patent Document 2 below discloses an electromagnetic wave shielding film in which a transparent inorganic conductive layer made of ITO or the like is provided on the surface of a transparent resin film.
Japanese Patent Laid-Open No. 10-335885 JP-A-5-323101

  However, in the conventional electromagnetic wave shielding film as described in the above-mentioned patent document, it is difficult to control the balance between visible light permeability and electromagnetic wave shielding property. That is, in an electromagnetic shielding film formed by bonding a conductive mesh to a transparent resin film, it is necessary to lower the opening ratio of the conductive mesh in order to improve electromagnetic shielding properties, and the opening ratio can be lowered. The visible light transmittance decreases as the time increases. Moreover, in order to improve visible light transmittance, it is necessary to make an aperture ratio high, and an electromagnetic wave shielding property falls, so that an aperture ratio becomes high.

  In addition, in the electromagnetic wave shielding film having a transparent conductive thin film made of ITO or the like on the surface of the transparent resin film, in order to increase the electromagnetic wave shielding property, It is necessary to increase the thickness. And as the thickness increases, the visible light transmittance decreases. On the other hand, in order to improve the visible light transmittance, it is necessary to reduce the thickness, and the electromagnetic wave shielding property is lowered as the thickness is reduced.

  Thus, in the conventional electromagnetic wave shielding film, if the visible light transmittance is increased, the electromagnetic wave shielding property is decreased, and if the electromagnetic wave shielding property is increased, the visible light transmission property is reduced, It was difficult to increase both.

  This invention solves the said conventional subject in an electromagnetic wave shielding film, and provides the electromagnetic wave shielding film which combined visible-light transmittance and high electromagnetic wave shielding property.

  As a result of intensive studies aimed at solving the above problems, the present inventors have focused on the fact that the intensity of the electromagnetic waves radiated from the front surface of the display device differs depending on the frequency. Here, FIG. 11 shows the results of measuring the intensity (dB) of electromagnetic waves in a frequency range of 1 MHz to 1 GHz radiated from a general plasma display separately for horizontal waves and vertical waves. As shown in FIG. 11, the intensity of the electromagnetic wave varies depending on the frequency.

  As a conventionally known electromagnetic wave shielding film, the present inventors attach an electroconductive mesh to the surface of an electromagnetic wave shielding film having a structure in which a transparent conductive thin film made of ITO is formed on the surface of a transparent resin film and the surface of the transparent resin film. The frequency characteristics of the electromagnetic wave shielded by the electromagnetic shielding film having the combined structure were measured.

  Surprisingly, the frequency characteristics of the electromagnetic waves to be shielded were greatly different between the two. Specifically, an electromagnetic wave shielding film having a structure in which a transparent conductive thin film made of ITO is formed has a very low shielding effect in a high frequency region, and an electromagnetic wave shielding film having a structure in which an electrically conductive mesh is bonded is up to about 300 MHz. The shielding effect in the low frequency region was low.

  As shown in FIG. 11, the horizontal wave of the electromagnetic wave shown in FIG. 11A has a peak of about 60 dB near 80 MHz and a peak of about 50 dB near 600 MHz. In the vertical wave shown in FIG. 11B, there is a peak of about 60 dB near 100 MHz. Therefore, in order to shield all the electromagnetic waves different depending on the frequency by using the conventional electromagnetic shielding film, in the case of using the electromagnetic shielding film having the configuration in which the transparent conductive thin film made of ITO is formed, the transparent conductive thin film It is necessary to increase the film thickness, and in the case of using an electromagnetic shielding film having a configuration in which a conductive mesh is bonded, the aperture ratio of the conductive mesh must be lowered. In this case, the visible light transmittance is reduced.

  The present inventors pay attention to the frequency dependence of the shielding characteristics of the electromagnetic wave shielding films having the above-described configurations, and as a result of various studies, the conductive thin film formed so that the conductive mesh and the transparent conductive thin film are in contact with each other. It has been found that the attached conductive mesh can efficiently shield electromagnetic waves having a wide range of frequencies.

  That is, by using a conductive mesh with a conductive thin film formed so that a transparent conductive thin film such as ITO and the conductive mesh are in contact with each other, the aperture ratio of the conductive mesh is reduced or the thickness of the transparent conductive thin film is increased. Thus, it has been found that the electromagnetic wave shielding property can be improved in a wide frequency range while maintaining the visible light transmission property without reducing the visible light transmission property and improving the electromagnetic wave shielding property.

  The conductive mesh with a conductive thin film of the present invention comprises a transparent conductive thin film and a conductive mesh deposited so as to be in contact with the transparent conductive thin film. By disposing a conductive mesh with a conductive thin film having such a configuration on the front surface of the display device, it is possible to realize an electromagnetic wave shield with high electromagnetic wave shielding properties and high visible light transmittance in a wide frequency range.

In the conductive mesh with conductive thin film, the surface resistance of the transparent conductive thin film is preferably 10 ⁵ Ω / sq or less from the viewpoint of excellent shielding performance. In the conductive mesh with a conductive thin film of the present invention, even a transparent conductive thin film having a relatively high surface resistance as described above exhibits sufficient electromagnetic shielding properties by being deposited so as to be in contact with the conductive mesh.

  In addition, the electromagnetic wave shielding film of the present invention includes a transparent support, a conductive mesh attached to the transparent support, and an opening region formed by the conductive mesh on the surface of the transparent support. And a transparent conductive thin film formed in contact with the conductive mesh. By disposing the electromagnetic shielding film having such a configuration on the front surface of the display device, high electromagnetic shielding properties and visible light transmittance in a wide frequency range can be realized.

  The transparent support is preferably a transparent thermoplastic resin film. When a transparent thermoplastic resin film is used, it is easy to arrange it in close contact with the front surface of the display device.

  The method for producing an electromagnetic wave shielding film includes a foil deposition process for depositing a metal foil on a transparent resin film, and etching the metal foil deposited in the foil deposition process with a predetermined shape pattern. A conductive mesh forming step for forming a conductive mesh, and a transparent conductive thin film forming step for forming a transparent conductive thin film on the surface of the transparent resin film on the side on which the conductive mesh is formed so as to contact the conductive mesh. It is characterized by comprising.

  In forming the transparent conductive thin film in the transparent conductive thin film forming step, the transparent conductive thin film having a desired thickness can be easily formed by at least one thin film forming method selected from sputtering, vapor deposition, and coating. It is preferable because of

  Moreover, it is preferable to use the process by crimping | bonding metal foil to transparent thermoplastic resin films, such as an amorphous polyethylene terephthalate type resin, as said foil deposition process. By bonding the metal foil directly to the transparent thermoplastic resin film by pressure bonding, an adhesive layer is not formed on the transparent thermoplastic resin film as in the past. Accordingly, it is possible to suppress a decrease in visible light transmittance due to a difference in refractive index between the adhesive layer and the film. In the present invention, the term “crimping” means that a metal foil is directly pressed and joined to a thermoplastic transparent resin film without heating through an adhesive layer or the like.

  Furthermore, in the manufacturing method of the said electromagnetic wave shielding film, it is preferable to provide the press process for planarizing the surface in which the electroconductive mesh was formed in the said electroconductive mesh formation process. When the surface on which the conductive mesh is formed is flattened by such a pressing step, the conductive mesh is embedded in the transparent thermoplastic resin film, and only the upper surface of the conductive mesh is exposed. In this case, since the conductive layer is formed on the entire surface of the transparent thermoplastic resin film in which the conductive mesh is embedded, the surface having a low surface resistance can be formed.

  In addition, as a method for producing an electromagnetic wave shielding film, a foil deposition process for depositing a metal foil on a transparent resin film, and a metal foil deposited in the foil deposition process are etched to form a predetermined pattern. A manufacturing method comprising a conductive mesh forming step of forming a mesh and a transparent conductive thin film laminating step of laminating the transparent conductive thin film formed on the transparent substrate surface so as to be in contact with the conductive mesh is as follows: The electromagnetic wave shielding film of the invention is preferable because it can be easily obtained.

  In addition, when at least one of the surfaces to be bonded in the bonding step is subjected to plasma treatment or corona discharge treatment, the adhesion strength of the bonded surface is increased, so that it is reliable as an industrial product. High electromagnetic shielding film can be obtained.

  The conductive mesh with conductive thin film and the electromagnetic wave shielding film of the present invention are electromagnetic wave shielding members having high visible light permeability and high electromagnetic wave shielding properties in a wide frequency range.

  Moreover, according to the manufacturing method of the electromagnetic wave shielding film of this invention, the electromagnetic wave shielding film of this invention which show | plays the said outstanding effect can be manufactured easily.

  The contents of the present invention will be specifically described below.

  The conductive mesh with a conductive thin film of the present invention comprises a transparent conductive thin film and a conductive mesh deposited so as to be in contact with the transparent conductive thin film.

  FIG. 1 is a schematic explanatory view of a configuration of a conductive mesh with a conductive thin film of the present invention. An opening 11 is formed in the conductive mesh 1 shown in FIG. On the other hand, 2 in FIG. 1B shows a transparent conductive thin film. The conductive mesh with conductive thin film 3 of the present invention shown in FIG. 1 (c) is configured to be attached so that the conductive mesh 1 and the transparent conductive thin film 2 are in contact with each other.

  Such a conductive mesh with a conductive thin film is used in the form of an electromagnetic wave shielding film, for example.

  The electromagnetic wave shielding film of the present invention includes a transparent support, a conductive mesh adhered to the transparent support, and the conductive mesh in a region of an opening formed by the conductive mesh on the surface of the transparent support. And a transparent conductive thin film formed so as to be in contact with the substrate.

  Examples of the transparent support in the present invention include a transparent resin film and glass.

  As the transparent resin film, a transparent thermoplastic resin film is preferably used, and more preferably, a transparent thermoplastic resin film having a total visible light transmittance of 70% or more made of a resin having a softening temperature of 200 ° C. or lower is used. The softening temperature can be confirmed by measurement of dynamic viscoelasticity. Specifically, it is a temperature at which tan δ shows a peak when a tensile stress is applied to the test piece in a viscoelasticity measuring apparatus and a loss tangent (tan δ) measured by the response is measured.

  Specific examples of the transparent thermoplastic resin film include, for example, polyester resins such as polyethylene terephthalate resin, polyethylene naphthalate resin, and polybutylene terephthalate resin, polyolefin resins such as polyethylene resin and polypropylene resin, and polycarbonate. A film made of a resin such as a (meth) acrylic resin such as a polyresin or polymethylene methacrylate resin and having a total visible light transmittance of 70% or more. In these, the film which consists of resin containing a polyethylene terephthalate-type resin, a polycarbonate-type resin, and a polyethylene terephthalate-type resin and a polycarbonate-type resin from the point of transparency and adhesiveness with metal foil is preferable.

  Among the polyethylene terephthalate resins, the amorphous polyethylene terephthalate resin has a high pressure bonding strength when the conductive mesh is attached to the transparent thermoplastic resin film by thermocompression bonding. Even if it cools, it is especially preferable at the point which can maintain transparency without whitening like a crystalline polyethylene terephthalate-type resin.

  Such an amorphous polyethylene terephthalate resin is an amorphous resin having a molecular structure in which a part of the ethylene glycol unit of polyethylene terephthalate and polyethylene terephthalate is substituted with a cyclohexanedimethanol unit such as 1,4-cyclohexanedimethanol. This is a copolyester.

  Specific examples of the amorphous polyethylene terephthalate include, for example, Oaster (registered trademark) manufactured by Okura Kogyo Co., Ltd., RIVESTAR (registered trademark) manufactured by Riken Technos Co., Ltd., and Peters manufactured by Mitsubishi Plastics Co., Ltd. (Registered trademark), Diafix (registered trademark), Petace (registered trademark) manufactured by Tsutsunaka Plastic Industry Co., Ltd., Hytron PG manufactured by Tamapoli Co., Ltd., PETG film sheet manufactured by Taihei Chemical Products Co., Ltd., etc. It is done.

  On the other hand, the conductive mesh in the present invention is a geometric conductive mesh having a predetermined opening and a line width formed from a conductive material such as a metal foil or conductive fiber.

  For example, a conductive mesh made of a metal foil is formed by chemical etching using a known microlithography technique after the metal foil is thermocompressed or bonded to a transparent support such as a transparent thermoplastic resin film. be able to.

  The metal foil is made of a metal such as copper, aluminum, nickel, iron, gold, silver, stainless steel, tungsten, chromium, titanium, or an alloy containing these, and has a thickness of 0.1 to 40 μm, preferably 5 to 5 μm. An example of the metal foil is 18 μm. Among these, copper foil, aluminum foil, or nickel foil is preferable from the viewpoint of excellent electromagnetic shielding properties, easy etching for forming a conductive mesh, and adhesiveness to a transparent support.

  Examples of the shape of the opening of the formed conductive mesh include triangles such as regular triangles, isosceles triangles and right triangles, squares such as squares, rectangles, rhombuses, parallelograms, trapezoids, (positive) hexagons, (Positive) Octagon, (Positive) dodecagon, (Positive) N-gon (n is a positive integer), circle, ellipse, star, etc. A single repetition of units or a combination of two or more types can be mentioned.

  The wiring width of the conductive mesh is preferably 40 μm or less, and more preferably 25 μm or less. Further, when the wiring width is too thin, the surface resistance is increased and the electromagnetic wave shielding property is lowered, so that the thickness is preferably 1 μm or more.

  The wiring thickness is preferably 40 μm or less. Further, when it is too thin, the surface resistance is increased and the electromagnetic wave shielding property is lowered, so that it is preferably 0.5 μm or more, more preferably 1 μm or more, and particularly preferably 5 μm or more.

  Visible light transmittance is improved as the distance between the wirings is increased. However, when the distance is too large, the electromagnetic shielding property is deteriorated. Therefore, the interval is preferably 100 μm or more and 1000 μm (1 mm) or less.

  In addition, the aperture ratio of the conductive mesh is preferably 50% or more, and more preferably 60% or more from the viewpoint of excellent visible light transmittance. The aperture ratio is the ratio (percentage) of the area obtained by subtracting the area of the conductive mesh portion from the effective area with respect to the effective area of the electromagnetic wave shielding film.

  The transparent conductive thin film in the present invention includes a transparent metal oxide film such as an ITO (indium oxide-tin oxide) thin film, or a thin film made of a transparent conductive resin or the like. Such a thin film should be formed by a method such as sputtering, ion plating, chemical vapor deposition, vacuum vapor deposition, spray pyrolysis, chemical plating, electroplating, coating, or a combination thereof. Can do.

If the film thickness of the transparent conductive thin film is too thin, the surface resistance is increased and the electromagnetic wave shielding property is lowered, and if it is too thick, the visible light transmittance is lowered. In the present invention, the surface resistance of the transparent conductive thin film is preferably 10 ⁵ Ω / sq or less, more preferably 4000 Ω / sq or less. Therefore, it is preferable that the film thickness is formed in a range showing the surface resistance value in the above range.

  The transparent conductive thin film in the present invention is formed so as to come into contact with the conductive mesh in the region of the opening formed by the conductive mesh on the surface of the transparent support. By forming the transparent conductive thin film in this way, the transparent conductive thin film and the conductive mesh are electrically connected, and high electromagnetic shielding properties are exhibited in a wide frequency range. The formation of the transparent conductive thin film is not limited to the region of the opening on the surface of the transparent support, and is electrically connected to the conductive mesh at least in the region of the opening on the surface of the transparent support. What is necessary is just to be formed.

  Below, an example of the manufacturing method of the electromagnetic wave shielding film of this invention is demonstrated in detail.

(Foil deposition process for depositing metal foil on transparent resin film)
As a method of attaching a metal foil to a transparent resin film, there are a method of applying an adhesive to the surface of the transparent resin film and bonding the metal foil, and a method of directly pressing the thermoplastic resin film without using an adhesive. Used.

  As the foil deposition step, in particular, a method of pressure-bonding a thermoplastic resin film without using an adhesive is preferably used. In this case, it is preferable to use a method of using a film made of an amorphous polyethylene terephthalate resin as the thermoplastic resin film, placing a metal foil on the surface, and bonding them by hot pressing. According to this method, the metal foil can be directly bonded to the transparent thermoplastic resin film by thermocompression bonding, and an adhesive layer is formed on the surface of the transparent thermoplastic resin film as in the conventional bonding method using an adhesive or the like. Not. Accordingly, it is possible to suppress a decrease in visible light transmittance due to a difference in refractive index between the adhesive layer and the film.

  The conditions for the hot press are appropriately selected depending on the type of the transparent resin film. As a specific example, for example, when a transparent resin film made of an amorphous polyethylene terephthalate resin having a thickness of about 25 to 250 μm is used as the transparent resin film, the set temperature of the hot press is about 80 to 130 ° C. And the conditions which press about 15 to 90 minutes with the pressure of about 3 MPa of press pressure are mentioned.

  In addition, in the case of the said crimping | compression-bonding, it is preferable from the point which improves the adhesiveness with metal foil that the said to-be-bonded surface is surface-treated by plasma processing or a corona discharge process. Moreover, it is preferable that the surface of the metal foil to be crimped is a roughened surface.

(Conductive mesh formation process)
A conductive mesh having a desired pattern is formed on the metal foil obtained in the above step and applied to the transparent resin film using a mask pattern by, for example, a microlithography method.

  Examples of the microlithography include photolithography, X-ray lithography, electron beam lithography, ion beam lithography, and screen printing. Among these, photolithography is preferable from the viewpoint of processing accuracy, simplicity, and mass productivity, and photolithography using a chemical etching method is particularly preferable.

  The conductive mesh formed by the above method is further pressed by a pressing process for flattening the surface on which the conductive mesh is formed, and the upper exposed surface of the conductive mesh and the surface of the transparent resin film Are preferably formed to have substantially the same height.

  As the method of pressing, the conductive mesh was formed at a temperature at which the formed conductive mesh was not misaligned, specifically, at a temperature equal to or slightly higher than the softening point of the transparent resin film. A method of hot pressing a transparent resin film with a smooth press surface is mentioned. Further, as a pressing method, a pressing method using a roller may be used.

  The pressing process will be described more specifically based on the schematic explanatory view of FIG.

  In Fig.2 (a), 4 is a transparent resin film, 1 shows the electroconductive mesh attached to the transparent resin film.

  In FIG. 2A, the release film is placed so as to cover the entire surface of the transparent resin film 4 on which the conductive mesh 1 is attached. And it heat-presses and presses so that a pressure may be applied equally to the said whole surface through the said release film. As shown in FIG. 2B, the conductive mesh 1 adhered to the transparent resin film 4 by the heating / pressurizing press is applied to the transparent resin film 4 with the upper exposed surface of the conductive mesh 1 and the transparent resin. The surface of the film 4 is embedded so as to have substantially the same height, and the surface is flattened.

(Transparent conductive thin film forming process)
As a method of forming a transparent conductive thin film, various conventional thin film forming methods using a conductive material such as ITO, specifically, for example, sputtering, ion plating, chemical vapor deposition, vacuum, etc. Examples thereof include a vapor deposition method, a spray pyrolysis method, a chemical plating method, an electroplating method, a coating method, or a combination thereof. Among these, the sputtering method, the chemical vapor deposition method, and the vacuum vapor deposition method are preferable because the film thickness can be easily controlled and the film thickness can be made uniform.

  The electromagnetic wave shielding film of the present invention can be produced by the method as described above.

  In the manufacturing method described above, after the conductive mesh is formed on the surface of the transparent resin film in advance, in the transparent conductive thin film forming step, the opening of the conductive mesh deposited on the surface of the transparent resin film is transparent. Although the example which forms a transparent conductive thin film so that it may contact with the said electroconductive mesh on the support body surface was demonstrated, the order of these each process is not specifically limited.

  That is, after forming the transparent conductive thin film on the transparent resin film surface using the thin film forming method in the transparent conductive thin film forming step, a metal foil is deposited on the transparent conductive thin film surface by the same method as the foil depositing step. Furthermore, the conductive mesh may be formed using the same method as in the conductive mesh forming step.

  Further, as another method for obtaining the electromagnetic wave shielding film of the present invention, the following method may be further used.

  That is, a method of bonding a transparent substrate having a transparent conductive thin film formed on the surface thereof so that the transparent conductive thin film formed on the transparent substrate surface is opposed to a conductive mesh previously formed on the surface of the transparent resin film. (Bonding step) may be used.

  As the transparent substrate, a transparent resin substrate or glass substrate having a thickness of about 0.1 to 5 mm is used.

  Examples of the bonding method in the bonding step include bonding using an adhesive and a method of pressure bonding by hot pressing.

  The manufacturing method by the said bonding process is demonstrated concretely using the schematic explanatory drawing of FIG.

  In Fig.3 (a), 4 is a transparent resin film, 1 shows the electroconductive mesh attached to the transparent resin film.

  In FIG. 3B, 51 is a thin film forming transparent substrate in which the transparent conductive thin film 2 is formed on the surface of the transparent substrate 5.

  As shown in FIG. 3B, a thin film-formed transparent substrate 51 is placed on the surface of the transparent resin film 4 on which the conductive mesh 1 is attached. And it heat-presses from the back side of the bonding surface of the said thin film formation transparent substrate 51 so that a pressure may be applied equally to the said bonding surface whole. In addition, you may bond together with an adhesive instead of carrying out hot press and crimping | bonding.

  When the method of hot press is used, as shown in FIG. 3C, the upper exposed surface of the conductive mesh 1 attached to the transparent resin film 4 and the surface of the transparent resin film 4 are substantially the same. It is embedded so that the surface is flattened. And the electroconductive mesh main body 2 and the transparent conductive thin film 2 are formed so that it may contact.

(Configuration example of electromagnetic shielding film)
A configuration example of the electromagnetic wave shielding film of the present invention will be described below.

  FIG. 4 is a schematic view showing an embodiment of the configuration of the electromagnetic wave shielding film. Reference numeral 31 denotes an electromagnetic wave shielding film, 1 denotes a conductive mesh, 2 denotes a transparent conductive thin film, 4 denotes a transparent resin film, and 11 denotes an opening formed by the conductive mesh. The conductive mesh 1 is attached to the surface of the transparent resin film 4, and the transparent conductive thin film 2 is formed on the surface of the transparent resin film 4 and the surface of the conductive mesh 1 in the opening 11. . And the electroconductive mesh 1 and the transparent conductive thin film 2 are formed so that it may contact.

  FIG. 5 is a diagram showing another embodiment of the configuration of the electromagnetic wave shielding film. In FIG. 5, 32 is an electromagnetic wave shielding film, 1 is a conductive mesh, 2 is a transparent conductive thin film, 4 is a transparent resin film, and 11 is an opening of the conductive mesh. The conductive mesh 1 attached to the transparent resin film 4 is embedded in the transparent resin film 4 so that the upper exposed surface of the conductive mesh 1 and the surface of the transparent resin film 4 have substantially the same height. The surface is flattened. The transparent conductive thin film 2 is formed on the surface of the transparent resin film 4 and the surface of the conductive mesh 1 in the opening 11. And the electroconductive mesh 2 and the transparent conductive thin film 2 are formed so that it may contact.

  FIG. 6 is a diagram showing still another embodiment of the configuration of the electromagnetic wave shielding film. In FIG. 6, 33 is an electromagnetic wave shielding film, 1 is a conductive mesh, 2 is a transparent conductive thin film, 4 is a transparent resin film, and 11 is an opening. A transparent conductive thin film 2 is formed on the surface of the transparent resin film 4. And the electroconductive mesh 1 is adhere | attached on the surface. And the electroconductive mesh 1 and the transparent conductive thin film 2 are formed so that it may contact.

(Use of electromagnetic shielding film of the present invention)
The electromagnetic wave shielding film of the present invention is disposed on a display surface on the front surface of a display device such as a PDP (plasma display panel), so that electromagnetic waves radiated from the display surface without reducing the visible light transmittance of the display surface. Can be effectively shielded.

  As a means for disposing on the display surface, the display structure for electromagnetic wave shielding such as an optical filter is formed by combining with a PDP surface directly using an adhesive or an adhesive, or in combination with various optical films. Body may be pasted together.

  Hereinafter, the present invention will be described in more detail with reference to examples. In addition, this invention is not limited at all by this Example.

Example 1
Surface of a transparent resin film with a thickness of 100 μm and a square amorphous polyethylene terephthalate (PET) film (PET) (Okura Kogyo Co., Ltd. “Ooster”, softening temperature 120 ° C., refractive index 1.567) In addition, after placing an electrolytic copper foil (BH-WS, manufactured by Furukawa Electric Co., Ltd.) having a thickness of 12 μm so that the roughened surface (Ra 0.24 μm) faces the film, 130 ° C., 3 MPa, The film was pressure-bonded by hot pressing under the condition of minutes to obtain a transparent resin film with copper foil.

  Next, a glass mask having a pattern formed on the copper foil surface of the transparent resin film with copper foil is disposed, and a conductive mesh having a square lattice pattern with a wiring width of 25 μm and a lattice spacing of 300 μm is formed by a photolithography process. Thus, a transparent resin film having a conductive mesh attached thereto was obtained.

  Next, a release film is disposed on the upper and lower surfaces of the transparent resin film to which the conductive mesh is applied, and is subjected to hot pressing at 130 ° C. and 3 MPa for 10 minutes, whereby the surface on which the conductive mesh is formed Was flattened.

  Next, ITO was sputtered on the surface of the transparent resin film on which the conductive mesh was adhered to form an ITO conductive thin film having a thickness of about 500 mm. The surface resistance value of the formed ITO thin film was formed by forming only an ITO conductive thin film having a thickness of about 500 mm on the transparent resin film, and measuring the surface resistance value according to the four-probe method (Lorestar manufactured by Mitsubishi Chemical Corporation). It was measured by. As a result, the surface resistance value was 300Ω.

  Since the ITO conductive thin film covers the surface almost uniformly, the ITO conductive thin film and the conductive mesh are in contact with each other.

About the obtained electromagnetic wave shielding film, the electromagnetic wave shielding property and visible light transmittance were evaluated by the following methods. The results are shown in Table 1.
<Electromagnetic wave shielding>
According to the KEC (Kansai Electronic Industry Development Center) method, the electromagnetic shielding property in the frequency range of 1 MHz to 1 GHz (1000 MHz) was measured. The results are shown in FIG.
<Visible light transmittance>
Using a haze meter NDH2000 manufactured by Nippon Denshoku Industries Co., Ltd., the transmittance was measured according to “Testing method of total light transmittance of plastic transparent material” of JIS K7361-1 (corresponding to ISO 13468-1). did.

(Example 2)
An electromagnetic wave shielding film was produced and evaluated in the same manner as in Example 1 except that an ITO conductive thin film (surface resistance value 2000 Ω) having a thickness of about 80 mm was formed as the ITO conductive thin film. The results are shown in Table 1 and FIG.

(Example 3)
On the surface of the crystalline PET film having a thickness of 100 μm, an ITO conductive thin film having a thickness of about 1100 mm was formed as an ITO conductive thin film so as to have a surface resistance of 70Ω, thereby obtaining a conductive thin film-forming transparent film. Then, the conductive thin film-forming film and a transparent resin film coated with the same conductive mesh as that formed in Example 1 were bonded together so that the ITO conductive thin film and the conductive mesh were in contact with each other.

  Specifically, the surface on which the ITO conductive thin film is formed and the surface on which the conductive mesh is formed are opposed to the transparent resin film on which the conductive thin film forming film and the conductive mesh are adhered. The bonded surfaces were stacked. And it crimped | bonded by heat-pressing for 10 minutes on conditions of 130 degreeC and 3 MPa. In addition, the said ITO conductive thin film and the conductive mesh contacted by this hot press. The results are shown in Table 1 and FIG.

(Comparative Example 1)
An electromagnetic wave shielding film was produced and evaluated in the same manner as in Example 1 except that the ITO thin film was not formed. The results are shown in Table 1 and FIG.
(Comparative Example 2)
An electromagnetic wave shielding film in the same manner as in Example 1 except that only an ITO conductive thin film (surface resistance value 70Ω) having a thickness of about 1100 mm was formed as an ITO conductive thin film on the transparent resin film without forming a conductive mesh. Were manufactured and evaluated. The results are shown in Table 1 and FIG.

(Comparative Example 3)
An electromagnetic wave shield was formed in the same manner as in Example 1 except that an ITO thin film was not formed and a conductive mesh with a square lattice pattern with a lattice spacing of 600 μm was formed instead of a conductive mesh with a square lattice pattern with a lattice spacing of 300 μm. The film was manufactured and evaluated. The results are shown in Table 1.
(Comparative Example 4)
An electromagnetic wave shield was formed in the same manner as in Example 1 except that an ITO thin film was not formed and a conductive mesh having a square lattice pattern with a lattice spacing of 900 μm was formed instead of a conductive mesh having a square lattice pattern with a lattice spacing of 300 μm. The film was manufactured and evaluated. The results are shown in Table 1.

  The electromagnetic wave shielding films obtained in Examples 1 to 3 have high electromagnetic wave shielding properties and high visible light transmittance in a wide frequency range of 1 MHz to 1000 MHz, as shown in Table 1 and FIGS. 7 to 9. Realized.

  Particularly, in Example 1 including an ITO conductive thin film (thickness of about 500 mm) having a surface resistance of 300Ω and a conductive mesh formed so as to be in contact with the conductive thin film, a high visible light transmittance (75%) is obtained. In addition to the low frequency region up to 230 MHz, high electromagnetic shielding properties are shown in the high frequency region of 230 to 1000 MHz while maintaining (FIG. 7). That is, the shield level shown in FIG. 7 is 55 dB or more in the frequency range of 1-230 MHz, the peak value is 90 dB in 10 MHz, 50 dB or more in the range of 230-600 MHz, and 600 MHz-1000 MHz. Even in the region, it is 41 dB or more.

    On the other hand, according to FIG. 12, which shows noise characteristics radiated from a general plasma display, the shield characteristics required in the 230 to 1000 MHz region is approximately 40 dB or more. Since the minimum value of the characteristic is 41 dB, the required characteristic is sufficiently satisfied.

  Moreover, in the electromagnetic wave shielding film of Example 2 in which an ITO conductive thin film having a surface resistance value of 2000Ω is formed, the shield level is lower than that of Example 1, but it is 40 dB or more in the entire range of 30 MHz to 1000 MHz. Further, the visible light transmittance is 76%, and it can be seen that high electromagnetic shielding properties and visible light transmittance are maintained.

  In addition, it can be seen that the electromagnetic wave shielding film of Example 3 obtained by a production method different from that of Example 1 and Example 2 maintains high electromagnetic wave shielding properties and visible light transmittance.

  On the other hand, from FIG. 10, the electromagnetic wave shielding film of Comparative Example 1 having a configuration in which a conductive mesh is only formed has a low shielding effect up to about 300 MHz. Further, FIG. 10 shows that the electromagnetic wave shielding film of Comparative Example 2 having a configuration in which only an ITO conductive thin film is formed has a very low shielding effect in a high frequency region.

  Further, from Table 1, the electromagnetic wave shielding film of Comparative Example 3 having a wide grid interval of the conductive mesh and a high aperture ratio compared to Comparative Example 1 has a low shielding characteristic, and this tendency has a wider grid interval and an aperture ratio. It was more remarkable in the electromagnetic wave shielding film of Comparative Example 4 having a high value.

It is explanatory drawing of the typical structure of the conductive mesh with a conductive thin film of this invention. It is typical explanatory drawing regarding the manufacturing method of the electromagnetic wave shielding film of this invention. It is typical explanatory drawing regarding another manufacturing method of the electromagnetic wave shielding film of this invention. It is typical sectional drawing which shows one form of the electromagnetic wave shielding film of this invention. It is typical sectional drawing which shows another one form of the electromagnetic wave shielding film of this invention. It is typical sectional drawing which shows another one form of the electromagnetic wave shielding film of this invention. It is a figure which shows the shielding characteristic of the electromagnetic wave shielding film of Example 1. It is a figure which shows the shielding characteristic of the electromagnetic wave shielding film of Example 2. It is a figure which shows the shielding characteristic of the electromagnetic wave shielding film of Example 3. It is a figure which shows the shielding characteristic of the electromagnetic wave shielding film of the comparative example 1 and the comparative example 2. It is a figure which shows the noise characteristic radiated | emitted from a plasma display.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Conductive mesh 2 Transparent conductive thin film 3 Conductive mesh with a transparent conductive thin film 4 Transparent support body (transparent thermoplastic resin film)
DESCRIPTION OF SYMBOLS 5 Transparent substrate 11 Opening part of electroconductive mesh 31, 32, 33 Electromagnetic wave shielding film 51 Thin film formation transparent substrate

Claims (7)

A transparent support;
A conductive mesh pressure-bonded to the transparent support;
A transparent conductive thin film formed in contact with the surface of the opening formed by the conductive mesh on the surface of the transparent support and the surface of the conductive mesh;
The transparent support is a transparent thermoplastic amorphous polyethylene terephthalate resin film;
An electromagnetic wave shielding film, wherein a surface to be bonded of the conductive mesh is roughened. The electromagnetic wave shielding film according to claim 1, wherein the transparent conductive thin film has a surface resistance of 10 ⁵ Ω / sq or less. A foil deposition process for crimping a metal foil to a transparent resin film;
A conductive mesh forming step of forming a conductive mesh by etching the metal foil pressure-bonded in the foil deposition step with a predetermined shape pattern;
A transparent conductive thin film forming step of forming a transparent conductive thin film in contact with the surface of the transparent resin film on the side on which the conductive mesh is formed and the surface of the conductive mesh;
The method for producing an electromagnetic wave shielding film, wherein the transparent resin film is an amorphous polyethylene terephthalate resin.   The production of the electromagnetic shielding film according to claim 3, wherein the formation of the transparent conductive thin film in the transparent conductive thin film forming step is performed by at least one thin film forming method selected from a sputtering method, a vapor deposition method and a coating method. Method.   The manufacturing method of the electromagnetic wave shielding film of Claim 3 or 4 provided with the press process for planarizing the surface in which the electroconductive mesh was formed in the said electroconductive mesh formation process. A foil deposition process for crimping a metal foil to a transparent resin film;
A conductive mesh forming step of forming a conductive mesh by etching the metal foil pressure-bonded in the foil deposition step in a predetermined shape pattern;
A step of laminating a transparent conductive thin film formed on the surface of the transparent substrate in contact with and facing the conductive mesh;
The transparent conductive thin film, the exposed surface of the conductive mesh and the surface of the transparent substrate are embedded at substantially the same height, and a hot pressing step in which the surface is flattened,
The method for producing an electromagnetic wave shielding film, wherein the transparent resin film is an amorphous polyethylene terephthalate resin. The method for producing an electromagnetic wave shielding film according to claim 6, wherein at least one of the surfaces to be bonded in the bonding step is subjected to plasma treatment or corona discharge treatment.

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