JP2010192557A - Electromagnetic wave shielding film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electromagnetic wave shielding film having a conductive mesh pattern with a good electromagnetic wave shielding property. <P>SOLUTION: An electromagnetic wave shielding film has a transparent substrate 2, and a conductive mesh pattern 1 formed on the transparent substrate 2. The mesh pattern 1 is configured by arranging many belt bodies 1a made of a conductive material in a reticular pattern. A mutual distance D of adjacent belt bodies 1a is equal to or more than 1 &mu;m and equal to or less than 25 &mu;m. An aperture ratio of the mesh pattern 1 is set in a range of 50% or more and less than 100%. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to an electromagnetic wave shielding film used for a display device of an electronic device such as a plasma display or a CRT.

  The electromagnetic waves radiated from the information processing apparatus affect other information processing apparatuses, and there is a risk of causing malfunction as well as reducing performance. For this reason, the International Radio Interference Special Committee (CISPR) of the IEC (International Electrotechnical Commission) issued an international standard for information processing equipment in 1985. A Council (VCCI) has been established, and a standard is set that limits electromagnetic waves from information processing devices up to 1 GHz. In the United States, Europe, etc., standards for electromagnetic waves from information processing devices are set in the same way as in Japan, and when selling information processing devices, it is necessary to obtain certification for standards that regulate electromagnetic waves in the countries where they are sold. .

A display that is one of information processing apparatuses includes a display that emits electromagnetic waves strongly from a display element such as a plasma display (hereinafter referred to as a PDP) or a CRT. Therefore, an element that shields electromagnetic waves is required.
As an electromagnetic shielding element on the front surface of the display, an electromagnetic shielding film in which a conductive mesh pattern using a light-shielding conductor is formed on a transparent resin film is generally used.

Since the conductive mesh pattern is light-shielding, there is a disadvantage that the brightness of the display panel is lowered and the visibility is deteriorated, and the ratio of the openings where the conductive mesh pattern is not formed (hereinafter referred to as the aperture ratio). It is required to be raised.
Therefore, the technique of the electromagnetic wave shielding film using a transparent conductive film is disclosed. As a material for the transparent conductive film, indium tin oxide (ITO) is used (for example, see Patent Document 1).

JP-A-5-323101

However, since the ITO transparent conductive film used in Patent Document 1 has almost no shielding characteristics in the high frequency band near 1 GHz, it is necessary to use it together with a conductive mesh such as a conductive mesh pattern. The shield by is dominant, and it can be said that optimization of the conductive mesh shape is necessary.
This invention is made | formed in view of such a point, The objective is to provide the electromagnetic wave shielding film provided with the electroconductive net-like pattern shape with a favorable electromagnetic wave shielding characteristic.

  In order to achieve the above object, an electromagnetic wave shielding film of the present invention comprises a transparent substrate and a conductive mesh pattern formed on the transparent substrate, and the mesh pattern is composed of a number of conductive materials. The strips are arranged in a grid pattern, and the distance D between the adjacent strips is 1 μm or more and 25 μm or less.

According to a second aspect of the present invention, in the electromagnetic wave shielding film according to the first aspect, the conductive mesh pattern includes a plurality of strips made of a conductive material arranged in a grid in the vertical and horizontal directions perpendicular to each other. It is characterized by having a grid pattern.
According to a third aspect of the present invention, in the electromagnetic wave shielding film according to the first or second aspect, the aperture ratio of the mesh pattern is 50% or more and less than 100%.

  According to the present invention, by setting the interval between the conductive mesh patterns to 1 μm or more and 25 μm or less, the effect of improving the electromagnetic wave shielding characteristics is increased, so that the line width of the mesh pattern can be reduced. As a result, an electromagnetic wave shielding film having excellent electromagnetic wave shielding characteristics and a high aperture ratio can be provided at low cost.

It is a cross-sectional schematic diagram which shows the electromagnetic wave shielding film in one embodiment of this invention. It is a schematic diagram of the planar view which shows the electromagnetic wave shielding film in one embodiment of this invention. It is a schematic diagram of the planar view which shows the electromagnetic wave shielding film in other embodiment of this invention. It is a schematic diagram of the planar view which shows the electromagnetic wave shielding film in other embodiment of this invention. It is a figure which shows the measurement result of the shield characteristic of the electromagnetic wave shield film shown in this Embodiment, and the conventional electromagnetic wave shield film. It is a graph which shows the shielding characteristic of the electromagnetic wave shielding film shown in this Embodiment.

Next, an embodiment of the electromagnetic wave shielding film according to the present invention will be described with reference to FIGS.
The electromagnetic wave shielding film shown in the present embodiment includes a transparent substrate 2 and a conductive mesh pattern 1 formed on the transparent substrate 2 as shown in FIGS.
The mesh pattern 1 is configured by arranging a large number of strips 1a made of a conductive material having a certain width and a certain thickness in a lattice shape in the vertical direction and the horizontal direction perpendicular to each other.

In the mesh pattern 1 shown in FIG. 3, a large number of strips having a constant width and a constant thickness are arranged so as to be hexagonal in the opening from which the transparent substrate 2 is exposed. Consists of.
In addition, the mesh pattern 1 shown in FIG. 4 includes a large number of strips having a constant width and a constant thickness made of a conductive material so that the opening from which the transparent substrate 2 is exposed has a triangular shape. It is composed by doing.
When forming the mesh pattern 1, an adhesive layer or the like for bonding the transparent substrate 2 and the mesh pattern 1 may be provided at the interface between the transparent substrate 2 and the mesh pattern 1.

In the electromagnetic wave shielding film shown in the present embodiment, the interval D between the strips 1a adjacent to each other in parallel in the mesh pattern 1 is set in the range of 1 μm to 25 μm.
According to the results of experiments described later by the inventors of the electromagnetic wave shielding film having such a mesh pattern 1, in the shielding characteristics of the electromagnetic wave shielding mesh, the line of the band 1 a constituting the mesh pattern 1 is shown. It has been found that the interval D (mesh interval) between the bands 1a is more dominant than the width. In particular, as is apparent from FIG. 6, by setting the distance D between the belts to 25 μm or less, an electromagnetic wave shielding film having excellent shielding characteristics against low frequency electromagnetic waves can be obtained. When the distance D between the belts exceeds 25 μm, electromagnetic waves having sufficient shielding properties cannot be used as a shield film. On the other hand, it is difficult to form a mesh pattern in which the distance D between the band bodies 1a is less than 1 μm.

  The conductive mesh pattern in the electromagnetic wave shielding film shown in this embodiment is such that the opening from which the transparent substrate is exposed is a triangle such as a regular triangle, an isosceles triangle, a right triangle, a square, a rectangle, a rhombus, and a parallelogram. A square pattern such as a trapezoid, a (positive) hexagon, a (positive) octagon, a (positive) n-gon (e.g., a dodecagon), etc. A single pattern of these units or a mesh pattern combining two or more types may be mentioned.

  Moreover, in the electromagnetic wave shielding film shown in the present embodiment, the conductive mesh pattern is formed in a vertical direction and a horizontal direction in which a large number of strips made of a conductive material as shown in FIG. 2 are orthogonal to each other. A grid pattern arranged in a grid pattern is preferable. By making the mesh pattern into a lattice pattern, it is possible to suppress problems during manufacturing, simplify the design and inspection process, and make the pattern suitable for mass production.

  Moreover, in the electromagnetic wave shielding film shown in this Embodiment, it is preferable that the aperture ratio of the conductive mesh pattern 1 is in the range of 50% or more and less than 100%. By setting the aperture ratio of the conductive mesh pattern 1 to 50% or more, the deterioration of the display quality of the image displayed when the electromagnetic wave shielding film shown in the present embodiment is provided in a display device such as a plasma display is suppressed. Can do.

  Moreover, as the transparent substrate 2 shown in the present embodiment, films or sheets made of various organic polymers having transparency can be used. For example, a base material usually used for an optical member such as a display can be cited, considering optical properties such as transparency and refractive index of light, and further various physical properties such as impact resistance, heat resistance and durability, Polyolefins such as polyethylene and polypropylene, polyesters such as polyethylene terephthalate and polyethylene naphthalate, celluloses such as triacetyl cellulose, diacetyl cellulose and cellophane, polyamides such as 6-nylon and 6,6-nylon, polymethyl methacrylate, etc. Those made of organic polymers such as acrylic, polystyrene, polyvinyl chloride, polyimide, polyvinyl alcohol, polycarbonate, ethylene vinyl alcohol are used.

  The thickness of the transparent substrate 2 is preferably about 5 μm to 500 μm. When the thickness is less than 5 μm, the handleability is deteriorated, and when it exceeds 500 μm, the flexibility is lost and the handleability is deteriorated.

  As a conductive material for forming the mesh pattern 1 shown in the present embodiment, a metal material such as copper (Cu), aluminum, nickel, iron, gold, silver, stainless steel, tungsten, chromium, titanium, or the like The alloy material which combined 2 or more types of these can be used. Copper, aluminum, and nickel thin films can be preferably used from the viewpoint of conductivity (electromagnetic wave shielding), mesh pattern formation, and cost. In addition, metal materials such as nickel, iron, stainless steel, and titanium are preferably used because they are excellent in magnetic shielding properties.

  In the electromagnetic wave shielding film shown in the present embodiment, as a method of forming the mesh pattern 1 made of a conductive material on the transparent substrate 2, it can be formed by, for example, an etching method. However, it is not limited to this in the manufacturing method of the electromagnetic wave shielding film of this invention.

Next, the electromagnetic wave shielding mesh in the embodiment of the present invention will be further described.
The conductive mesh (lattice pattern) 1 in which the conductive mesh pattern shown in FIGS. 1 and 2 is arranged in a grid is formed by attaching a Cu foil to the transparent substrate 2 and etching the Cu foil. .
At this time, a negative dry film resist AQ-1558 (trade name: manufactured by Asahi Kasei Electronics Co., Ltd.) was formed on the copper foil by thermal lamination, and ultraviolet exposure was performed through a glass plate on which an electromagnetic wave shielding mesh pattern was drawn.
Subsequently, a resist pattern was formed on the copper foil by performing spray development with a 1% sodium carbonate solution at 30 ° C.
Further, a shield mesh pattern was formed by etching the substrate.
Etching was performed using a ferric chloride solution of 50 ° C. and 36 ° Be, and a spray etching apparatus with a spray pressure of 0.2 MPa.
Subsequently, an unnecessary resist layer was removed using 3% sodium hydroxide at 50 ° C. to prepare a conductive shield film in which a conductive network pattern was formed.

  Here, a 100 μm thick polyester (PET) film is used for the transparent substrate 2, a 1 μm thick Cu foil is used for the conductive mesh (lattice pattern) 1, and the wiring width (width of the band 1 a) is obtained by etching. A conductive shield film having a grid pattern of 10 μm, a lattice interval (interval between strips 1a) D of 25 μm, and a line thickness (thickness of strip 1a) of 1 μm was formed.

  Then, four conventional electromagnetic wave shielding films 1 (wiring width 10 μm, lattice spacing 50 μm, wire thickness 1 μm) and electromagnetic wave shielding film 2 (wiring width 10 μm, which were prepared for comparison in the same materials and steps as in the above embodiment. Lattice spacing 100 μm, wire thickness 1 μm), electromagnetic shielding film 3 (wiring width 10 μm, lattice spacing 200 μm, wire thickness 1 μm), electromagnetic shielding film 4 (wiring width 20 μm, lattice spacing 200 μm, wire thickness 1 μm) (hereinafter, Comparative Example 1) FIG. 5 summarizes the results of measuring the electromagnetic wave shielding characteristics of Comparative Example 2, Comparative Example 3, and Comparative Example 4). According to the KEC (Kansai Electronics Industry Promotion Center) method, the electromagnetic wave shielding characteristics are evaluated by measuring how many dB of shielding effect can be obtained at a low frequency of 10 MHz and a high frequency of 500 MHz.

  As is clear from FIG. 4, the improvement of the shield characteristics due to the fact that the grating interval (interval between the band bodies 1a) D is halved is 9.7 dB (1 MHz), 9.8 dB (500 MHz) from 200 μm to 100 μm. 100 μm to 50 μm, 12.6 dB (1 MHz), 12.5 dB (500 MHz), 50 μm to 25 μm, 18.6 dB (10 MHz), 18.7 dB (500 MHz), and the lattice spacing is halved from 50 μm to 25 μm. The effect is greater than others. Therefore, it is possible to provide an electromagnetic wave shielding film having better shielding characteristics than the prior art by creating a conductive mesh shield film having a mesh (lattice) interval of 25 μm or less.

  Further, from the shield characteristic results of Comparative Example 2 and Comparative Example 4 shown in FIG. 5, it can be seen that the lattice spacing is more dominant in the shield characteristics than the line width. FIG. 6 shows a graph of shield characteristics at a frequency of 10 MHz and a high frequency of 500 MH when the line width is 10 μm (Comparative Example 1, Comparative Examples 1 to 3). This time, the line width was 10 μm, but it is easily estimated that the same result is obtained even when the line width is different.

The electromagnetic wave shielding film obtained in the embodiment of the present invention can be used as a front surface of a display device or a window film. In particular, it can be suitably used as a front plate of a plasma display. When used as a front plate of a plasma display, it can be installed by attaching an electromagnetic shielding film directly to the front surface of the main body of the plasma display. At this time, the mesh pattern can be embedded in an adhesive or an adhesive, and can be bonded to another member by the adhesive or the adhesive.
In addition, when the obtained electromagnetic wave shielding film is provided with an adhesive or a pressure-sensitive adhesive and directly attached to the plasma display, an additive may be added to the adhesive or the pressure-sensitive adhesive. Examples of the additive include materials having functions such as a near infrared absorption function, a color correction function, and an ultraviolet absorption function.

  The mesh pattern is preferably grounded through the conductive portion. Specifically, an electromagnetic wave shielding mesh corresponding to the size of the display is created, and its end is made into a frame shape in order to give physical strength to the electromagnetic wave shielding layer. And it is preferable to make conduction | electrical_connection from a part of the edge part, and to ensure an electromagnetic wave shielding characteristic.

  DESCRIPTION OF SYMBOLS 1 ... Mesh-like pattern (conductive mesh), 1a ... Band, 2 ... Transparent substrate.

Claims (3)

A transparent substrate and a conductive mesh pattern formed on the transparent substrate;
The mesh pattern is composed of a large number of strips made of a conductive material arranged in a lattice pattern,
An interval D between adjacent bands is 1 μm or more and 25 μm or less.
An electromagnetic wave shielding film characterized by that.   2. The electromagnetic wave according to claim 1, wherein the conductive mesh pattern is a grid pattern in which a large number of strips made of a conductive material are arranged in a grid pattern in a vertical direction and a horizontal direction orthogonal to each other. Shield film.   2. The electromagnetic wave shielding film according to claim 1, wherein the opening ratio of the mesh pattern is in the range of 50% or more and less than 100%.

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