JPH10335883A - Transparent material for electromagnetic shield - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a display image easy to see and improve electromagnetic shield by successively laminating a gray conductive metal film and Cu film into a mesh form on a transparent board, so as to provide specified total light transmittance. SOLUTION: On an inorganic transparent plate 1 such as glass plate a Ni, Cr or Ni-Cr alloy gray conductive metal film 2 of 0.005-1 μm is laminated into a mesh or lattice form, a Cu film 3 of 0.2-20 μm is laminatingly formed on the film 2, and a Ni-Cr alloy or similar gray conductive metal film 4 of 0.3-10 μm is formed on the Cu film 3, to thereby provide a high-transparency and high-electromagnetic shield member for which display images are seen easily.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transparent member for shielding electromagnetic waves, and the sheet-like member is effective for shielding electromagnetic waves from a screen such as a plasma display.

[0002]

2. Description of the Related Art In recent years, a large number of electronic information devices have been developed and are effectively used for their respective purposes, but on the other hand, various problems have also occurred. One of them is a malfunction due to an electromagnetic wave generated from the device or an electromagnetic wave received from another device, which has been internationally taken up as an electromagnetic environment problem. This is considered to be one international standard that will be followed by one restriction standard.

[0003] Means for removing electromagnetic interference can be broadly classified into a method in which an electromagnetic wave is reflected at the surface and the like, so that the electromagnetic wave is not transmitted, and a method in which electromagnetic wave energy is absorbed and neither reflected nor transmitted. The present invention relates to the latter method of absorbing electromagnetic waves, and it is an object of the present invention to provide a material for the method. The required function of the material also differs depending on the place of use in an electronic information device. For example, when the device is a CRT or a plasma display monitor, since the electromagnetic waves are radiated through the screen itself, the shielding material should not be opaque at first and should be transparent (there is no inconvenience for viewing the screen). Transparency) that effectively shields electromagnetic waves.

As for a transparent electromagnetic wave shielding material, for example, one side of a transparent plastic sheet is plated with nickel or copper using a mesh-like fiber woven fabric, and further, carbon black is coated on the plating layer. (Mixed with resin) is known (hereinafter referred to as M
Call the law. ). As an alternative, one side of a transparent plastic sheet is first coated with a transparent anchor layer for subsequent electroless plating, and then electroless plating of copper is performed thereon. There has been proposed a translucent electromagnetic wave shielding material having a mesh lattice pattern. When viewed from the non-processed surface (opposite side), the copper lattice pattern portion looks black (introduced in Japanese Patent Application Laid-Open No. 5-283889) (hereinafter referred to as the C method).

[0005]

However, each of the above methods has the following problems and is not sufficiently satisfied. First, in the M method, a conductive mesh pattern in which fibers are used as a core material is used. The pattern is abnormally thick and thick. In other words, transparency and electromagnetic wave shielding properties are not compatible with each other, and in particular, transparency is extremely unsatisfactory, and it is impossible to apply this to a screen such as a plasma display where transparency is also an important factor. That the pattern is clearly visible as if the pattern were more exposed, making it difficult to see the image, when viewing the screen from an oblique direction, the transparency is lower than when viewed from the front, and this shield The process of obtaining the material is complicated and the productivity is increased.

The method C has the following disadvantages. First, it is entirely dark, resulting in a decrease in transparency. The cause is considered to be coloring due to the remaining palladium catalyst dispersed on the transparent anchor layer used in the electroless plating of copper. Further, the provision of the transparent anchor layer induces a further decrease in the transparency. This is because the surface of the transparent anchor layer has fine irregularities in order to increase the adhesion of the copper electroless plating layer,
It is considered that diffuse reflection due to this was promoted. Also, the copper pattern is black (probably due to the remaining palladium catalyst), but depending on the content of the pattern, the black may be difficult to see through the screen,
In addition, it can be mentioned that the use of only the copper mesh pattern naturally has a limit in expressing a larger electromagnetic wave shielding effect.

The present invention has been made in view of the problems of the transparent electromagnetic wave shielding material according to the M method, the C method, and the like, and has a higher transparency, an easier to see display image, and an excellent electromagnetic wave shielding property. This is a result of intensive studies to find a shielding member. It is achieved by the following means.

[0008]

That is, the transparent member for shielding electromagnetic waves according to the present invention has a mesh-like gray color on a transparent substrate (1) so that the total light transmittance is 50% or more. It is characterized in that a conductive metal thin film (2) and a copper thin film (3) are sequentially laminated.

Further, on the mesh-like copper thin film (3),
Further, it is characterized by having a three-layer structure in which a gray conductive metal thin film (4) is laminated. Further, the transparent substrate (1) is a thermoplastic resin substrate having a total light transmittance of 50% or more, and the gray conductive metal thin film (2) or (4) is made of nickel, chromium, or an alloy thereof. The gray conductive metal thin film (2) has a thickness of 0.005 to 1 μm, and the copper thin film (3) has a thickness of 0.2 to 20 μm. And that the gray conductive metal thin film (4) has a thickness of 0.3 to 10 μm. Furthermore, on a sheet-like thermoplastic resin having a total light transmittance of 60% or more,
A thin film made of nickel, chromium, or an alloy thereof and having a thickness of 0.005 to 1 μm;
A copper thin film having a thickness of 0.3 μm and a thin film having a thickness of 0.3 to 10 μm made of any one of nickel, chromium and their alloys are sequentially laminated, and the mesh is formed so that the total light transmittance is 50% or more. It is characterized by forming a shape,
The electromagnetic wave shielding transparent member is characterized in that it is an electromagnetic wave shielding transparent member for a screen of a plasma display. Hereinafter, the present invention will be described in more detail.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, in the present invention, the transparent substrate (1) shown in FIG. 1 can basically recognize at least the display screen or the inside of the device through the transparent member for electromagnetic wave shielding of the present invention. It is intended for those having transparency of about 50% or more, heat resistance, non-shrinkage, mechanical strength, chemical resistance and the like. The shape is generally a sheet (about 0.05 to 2 mm in thickness), but it may be a bent shape or the like depending on the place of use. Specifically, a transparent substrate made of an inorganic substance such as a glass plate, polymethyl methacrylate, a copolymer of polystyrene or styrene with acrylonitrile or methyl methacrylate, poly (4-methylpentene-
1), a cyclic olefin polymer such as polypropylene or cyclopentene, norbornene, tetracyclododecane or the like alone or copolymerized with ethylene or the like, polyethylene terephthalate, polyethylene naphthalate, polyacrylate, polyether sulfone, polycarbonate, diethylene glycol bisallyl Examples thereof include transparent thermoplastic resin bases such as carbonates and liquid crystal polymers, and transparent synthetic resin bases made of acrylic, urethane, and epoxy thermosetting transparent resins.

The choice of the transparent substrate is determined in consideration of various conditions. At least the transparency (total light transmittance) is about 50% or more, and the substrate made of a thermoplastic resin is used. It is desirable to select from the following.

Next, the gray conductive metal thin film (2) in FIG. 1 will be described. Since the color of the thin film is grayish, the red color of the copper thin film changes to gray (dark gray) having a slight black color. Discoloration to this color also has the effect of increasing contrast (for example, for red) and suppressing surface reflection. In the case of light gray, gray is mixed with white, and the degree of surface reflection also varies depending on the mixing ratio of white.

[0013] In the gray system, since it is a conductive metal thin film, it has a higher electromagnetic wave shielding effect and an effect of preventing corrosion of the copper thin film, and further, the thin film itself is transparent because it is smooth. It exerts an effect of preventing a decrease in sex and the like. Therefore, the type is not particularly limited as long as it effectively exhibits such an effect, but, for example, a thin film made of nickel, chromium, a nickel-chromium alloy, aluminum, iron, stainless steel, platinum, or the like is used. No. Above all, nickel, chromium, or nickel-chromium is preferable because it is advantageous for simultaneously forming a network pattern of a copper thin film.

It is not desirable that the film thickness of the thin film (2) is too small or too large. If this is too thin, the red color due to the copper thin film will remain, and the contrast will not be improved. In addition, there is a case where the adhesion with the copper thin film to be laminated may not be sufficiently obtained,
There is substantially no additional effect on the electromagnetic wave shielding property. On the other hand, if the thickness is too thick, the difference in heat shrinkage from the transparent substrate becomes more remarkable, which may cause inconvenience such as cracking or peeling, or the copper thin film (3) described later is etched in a mesh shape. In this case, there is a problem that a stable pattern cannot be obtained due to a difference in etching rate. In this sense, generally 0.0%
It is good to set it between about 0.05 and 1 μm, preferably between 0.01 and 0.5 μm.

The thin film (2) is in a state where it is patterned in a mesh pattern. Here, the mesh pattern referred to in the present invention is a grid pattern with the same width and width or different width. Of course, the opening portion is rectangular, and of course, crosses obliquely at a certain angle, that is, the opening portion is a rhombus, or a polygonal shape of about 5-10 octagons, that is, the opening portion is a pentadecagonal. The case is also included. If the degree of opening of the mesh is large, the total light transmittance increases, but the electromagnetic wave shielding property tends to decrease.

The method for forming the thin film (2) is not particularly limited, but the following method is preferably used. First, the surface of the transparent substrate (1) is physically degreased or cleaned by corona discharge, glow discharge, flame (flame), oxidizing agent, etc.
Pretreat chemically. Since what kind of pretreatment is performed depends on the type of the transparent substrate (1), each effective method may be confirmed experimentally in advance and determined.

Next, a gray conductive metal thin film (2) is provided on the surface of the transparent substrate (1) by a thin film forming means so as to form a mesh or a uniform surface. Here, the thin film forming means is based on a vacuum deposition method, an ion plating method or a physical method which is generally used in sputtering. Among them, a low temperature, a high speed, and an adhesive property with the transparent substrate (1) can be obtained. A sputtering method is preferable for obtaining a stable state. The condition of the sputtering method is generally such that a sputtering voltage is applied to an ingot of the conductive metal in an atmosphere of an inert gas such as argon in an ultra-vacuum state. The metal ions sputtered from the ingot surface are fixed as a thin film on the transparent substrate surface.

Here, means for patterning the thin film (2) into a mesh pattern include:
Immediate meshing is also possible. For example, the transparent substrate (1) is printed by a printing method (such as screen printing or offset printing) using silicone oil, mineral oil, vegetable oil, or the like. At this time, the printing pattern is such that the oil is printed on a non-pattern portion (non-image portion). Then, the sputtering or the like is performed on the printed transparent substrate. A gray conductive metal thin film is formed only on the mesh portions. On the other hand, an etching method can be used. In this case, first, the thin film is uniformly formed on the entire surface of the transparent substrate, and the mesh pattern portion is masked by photolithography using a photoresist, and the other non-pattern portions are removed by etching with an inorganic acid. I do. This etching method can be used under the same condition as one of the means for forming a mesh of a copper thin film (3) described later and a gray-based conductive metal thin film (4). It is possible to provide a uniform thin film (2) over the entire lower surface of the next copper thin film (3) without patterning it into a mesh pattern, and this is also preferable.

Next, the mesh-like copper thin film (3) in FIG. 1 will be described. First, since the thin film is made of copper, it has an extremely excellent electromagnetic wave shielding effect and also has an effect of further promoting the speed of heat dissipation to the outside with respect to the heating of the shield member by transmitting and receiving electromagnetic waves. Has various effects, such as being easier to produce an eye-shaped pattern. This is a feature not available with the use of other metals.

The copper thin film (3) is also laminated in a mesh pattern like the thin film (2), but at this time, transparency is maintained so that the total light transmittance does not become less than 50%. It is necessary to determine what specifications of the mesh are to be used. Transparency is largely determined by the aperture ratio of the mesh, but if the aperture ratio is set too high to achieve transparency, the important electromagnetic wave shielding property as well as the transparency deteriorates. The relationship between the transparency and the electromagnetic wave shielding properties was thoroughly studied on what kind of equipment, what kind of effect the transparent member of the present invention has, what kind of position is used, etc. It is good to decide on the net. For example, when used on the entire surface of a plasma display screen, the total light transmittance is 5%.
If it is set to about 5 to 70% and the mesh is provided in a grid shape (mesh shape), the electromagnetic wave shielding effect becomes 50 to 60 dB.
(DB) and a high effect can be obtained. The mesh density of the mesh at this time is about 100 to 200 lines / inch.

The thickness of the copper thin film (3) is preferably thick in order to further enhance the electromagnetic wave shielding effect, but the difference in heat shrinkage with the transparent substrate (1) is further promoted. It is easy to cause the phenomenon of saying. In particular, when the substrate is made of a thermoplastic resin, the influence is large, and delamination may even occur. Therefore, the film thickness balanced in these respects is 0.2 to 20 μm, preferably 1 to 15 μm.
m.

The method of forming the mesh-like copper thin film (3) on the thin film (2) is not particularly limited. For example, as in the case of the thin film (2), sputtering or the like or electrolytic plating may be used. Here, the electromagnetic wave shielding effect is a copper thin film (3)
Although the above-mentioned film thickness is preferably exemplified because it depends on the film thickness of the film, it takes a long time to form the film if the film thickness is to be achieved only by the thin film forming method. In order to shorten this time, it is preferable to use both the thin film forming method and the electrolytic plating method. In this case, it is preferable to perform, for example, sputtering and then electrolytic plating thereon.

The method of forming the mesh pattern of the copper thin film (3) may be, for example, the method of printing oil, sputtering the non-patterned portion, and immediately laminating the pattern as exemplified in the thin film (2). However, since the copper thin film (3) is required to be thicker than other thin films, it takes a long time to form the thin film using only a thin film forming means such as sputtering. In the case of this combined use, first, an underlayer is formed on the entire surface of the thin film (2) by sputtering, copper electrolytic plating is performed on the entire surface, and the desired pattern described above is photographed. It is preferable to form a mesh pattern by a plate making method and etching. Of course, it may be laminated by electrolytic plating of copper

The thus obtained transparent member for electromagnetic wave shielding may be used as it is for electromagnetic wave shielding of various displays and the like, but such a mesh-like copper thin film (3) is in direct contact with air. If you use
It is susceptible to oxidation and corrosion by oxygen and moisture. Therefore, in order to prevent this, for example, the entire surface of the copper thin film (3) is coated with a transparent resin, the same or different transparent substrate is used as the transparent substrate, or the substrate is polymerized by electroless plating. It is also possible to form a protective film. Further, a thin film (4) which is the same as the gray conductive metal thin film (2) of the first layer can be laminated.
Among these, the latter method of laminating the thin film (4) is preferable, and it is more preferable that a thin film made of nickel, chromium, or an alloy thereof is particularly stacked as the conductive metal thin film. This means that the influence of the copper thin film (3) on air is smaller, the electromagnetic wave shielding effect is larger, and the obtained transparent member can be viewed from any side (for example, from the front or the back). Because the red color of copper looks gray, it is convenient to use.

The thickness of the thin film (4) is preferably larger than the thickness of the thin film (2) in the first layer, specifically, about 0.3 to 10 μm, preferably about 1 to 5 μm.
This aims to substantially eliminate the influence of the copper thin film (3) on air and the like and to obtain a greater shielding effect of electromagnetic waves.

The thin film (4) may be formed on the entire surface of the copper thin film (3). However, if the required total light transmittance is less than 50%, the thin film (4) may be formed in a mesh shape. It is good to form. The method of forming the mesh shape is preferably the method described in the above-mentioned thin film (2) or thin film (3).

[0027]

Next, the present invention will be described in more detail with reference to Examples together with Comparative Examples. In the text, the total light transmittance (hereinafter abbreviated as Tt) referred to in each of Examples and Comparative Examples is JIS K7105 (19).
The transmittance (%) at a wavelength of 380 to 720 nm measured with a "U-3410" type spectrophotometer manufactured by Hitachi, Ltd. based on 81). Also, electromagnetic wave shielding (effect)
Is based on the Kansai Electronics Industry Promotion Center Act (generally KEC
Call it the law. ) Was evaluated by measuring the proximity electrolytic shielding effect using the above method, and this is shown as an attenuation rate (decibel).

Example 1 Biaxially stretched thickness 125 μm
Polyethylene terephthalate film (Tt = 88)
%, Referred to as PET film) as a transparent substrate, pre-treated by glow discharge, and then sputtered using nickel as a target under the following conditions to deposit a nickel thin film to a total thickness of 0.01 μm. . That is, the inside of the sputtering apparatus was first evacuated to 0.5 mTorr, argon was introduced into the apparatus as an inert gas, the vacuum was set to 8 mTorr, and 0.5 Kw of electric power was applied to perform sputtering. A nickel thin film having a uniform and sufficient adhesion was formed on the entire surface of the film. It had a gray color.

Next, by changing the nickel target to a copper target, copper was sputtered over the entire surface of the nickel thin film layer under the following conditions, and was deposited and laminated to a thickness of 0.3 μm. That is, the inside of the sputtering apparatus is first set to 0.
Vacuum to 5 mTorr, introduce argon gas, 8 mTorr
, And a voltage of 5 Kw of direct current (DC) was applied to perform sputtering.

Then, in order to further increase the thickness of the copper thin film layer of 0.3 μm, copper plating was performed on the layer to make the total thickness 5 μm. Hereinafter, this is referred to as a copper laminated film.

Next, an acrylic photosensitive resin is coated on the copper layer surface of the copper laminated film, and a grid-like negative film made of 100 mesh and 200 mesh is used. And exposed to ultraviolet light, and finally developed with an aqueous alkali solution to dissolve and remove the resin in the unexposed portion (non-reticulated pattern portion). Hereinafter, this is called a photoengraved film.

Then, on the photo-engraved film,
A ferric chloride aqueous solution is spray-sprayed to dissolve and remove the copper layer corresponding to the unexposed portion and the underlying nickel layer, and then immersed in an alkaline aqueous solution to form a mask-shaped mesh pattern portion. The cured acrylic resin film was peeled off, washed sufficiently with water and dried. Hereinafter, these are referred to as a 100 mesh film and a 200 mesh film.

The obtained 100 mesh film and 2
First, the reproducibility of the negative film was checked for the 00 mesh film.
A grid-like mesh was reproduced with a pattern size of.
Tt and electromagnetic wave 100 for each mesh film
The attenuation rate at 500 MHz (megahertz) was measured and summarized in Table 1.

[0034]

[Table 1]

(Example 2) Using the copper laminated film obtained in Example 1 above, sputtering was further performed on the entire surface under the following conditions using chromium as a target to form a thin film having a thickness of 1 µm. . That is, the inside of the sputtering apparatus is first evacuated to 0.5 mTorr, argon is introduced into the apparatus as an inert gas, and the sputtering apparatus is evacuated to 8 mTorr.
DC power of 5 Kw was applied to perform sputtering. Hereinafter, it is called a three-layer film.

Next, using the above three-layer film,
Under the same conditions as described above, after photolithography using a negative film of 100 mesh and 200 mesh, the non-pattern portion was removed by etching with an aqueous solution of ferric chloride and the like, followed by washing and drying. Each mesh was reproduced almost one-to-one with respect to the negative film, and did not peel off between the layers even when bent. Further, when viewed from either side of the two sides, there was no copper red color, and the color was slightly darker than that of Example 1.

Next, Tt and electromagnetic wave attenuation were measured for each of the obtained mesh films in the same manner as in Example 1, and the results are shown in Table 1. The transparent film for electromagnetic wave shielding obtained in this example was a PET film having a thickness of 125 μm for the transparent substrate (1) and a nickel-based conductive metal thin film (2) having a thickness of 0.01 μm shown in FIG. The thin film and the copper thin film (3) are a copper thin film having a thickness of 5 μm, and the gray conductive metal thin film (4) is a chromium thin film having a thickness of 1 μm.

(Comparative Example 1) In Example 1, no nickel thin film layer was provided, and only a 5 μm thin film of copper was used.
A mesh and a 200-mesh grid-like transparent PET film were produced in the same manner. The Tt and the electromagnetic wave attenuation rate of this product were measured and summarized in Table 1. From Table 1, there is no significant difference in transparency, but a difference in the electromagnetic wave attenuation rate, as compared with Example 1 and Example 2, which is the difference between the gray conductive metal thin film and the copper thin film in the present invention. This can be said to be the effect of the combination.

Further, each of the Examples and Comparative Examples obtained by
Each of the 0 meshes was superposed on a 0.5 mm acrylic plate, suspended over the entire screen of the plasma display with a gap of 3 mm, and the image was observed. As a result, with respect to those obtained in Examples 1 and 2, the existence of the lattice pattern was hardly noticed, and observation was possible with high contrast. It was visually noticed that it was difficult to observe.

[0040]

The present invention has the following effects by being configured as described above. First, transparency and electromagnetic wave shielding performance are at a high level that balances both, making it extremely effective for use as a member for electromagnetic wave shielding such as plasma displays that also require excellent transparency. Since the mesh pattern of the mesh formed on the base is colored in a dark gray system, compared with the red pattern,
When an image or the inside of a device is viewed, the presence of the pattern is not so noticeable, and it is possible to see through with a good contrast. The transparent member of the present invention is particularly effective for use on the front side of the screen of a plasma display. However, the present invention is not limited to this application, and it is not limited to this. It is a member that can be effectively used for devices and the like that suffer from obstacles.

[Brief description of the drawings]

FIG. 1 is a perspective sectional view showing a structure of a transparent member according to the present invention.

[Explanation of symbols]

 1. 1. transparent substrate 2. Gray conductive metal thin film Copper thin film 4. Gray conductive metal thin film

Claims (9)

[Claims] 1. A transparent substrate (1) having a total light transmittance of 5
A transparent member for electromagnetic wave shielding, wherein a gray-based conductive metal thin film (2) and a copper thin film (3) are sequentially laminated in a mesh shape so as to be 0% or more. 2. The transparent material for electromagnetic wave shielding according to claim 1, wherein a gray conductive metal thin film (4) is further laminated on the mesh-like copper thin film (3). Element. 3. The transparent substrate (1) has a total light transmittance of 5
The transparent member for an electromagnetic wave shield according to claim 1, wherein the transparent member is a thermoplastic resin substrate of 0% or more. 4. The gray conductive metal thin film (2) or (4) is made of any one of nickel, chromium, and alloys thereof. Transparent member for electromagnetic wave shielding. 5. The gray-based conductive metal thin film (2),
5. The transparent member for electromagnetic wave shielding according to claim 1, wherein the thickness is 0.005 to 1 [mu] m. 6. The thin copper film (3) has a thickness of 0.2 to 20.
The transparent member for electromagnetic wave shielding according to claim 1, wherein the transparent member has a thickness of μm. 7. The gray-based conductive metal thin film (4),
3. A film having a thickness of 0.3 to 10 .mu.m.
Or the transparent member for electromagnetic wave shielding according to 4. 8. A thin film having a thickness of 0.005 to 1 μm made of nickel, chromium, or an alloy thereof on a sheet-like thermoplastic resin having a total light transmittance of 60% or more,
A copper thin film having a thickness of 0.2 to 20 μm and a film thickness of 0.3 to 10 made of one of nickel, chromium and their alloys;
μm thin films are sequentially laminated and the total light transmittance is 50
%. A transparent member for electromagnetic wave shielding, characterized in that the mesh is formed so as to have a percentage of not less than%. 9. The transparent member for shielding electromagnetic waves according to claim 8, wherein the transparent member for shielding electromagnetic waves is a transparent member for shielding electromagnetic waves of a screen of a plasma display.