JPH11330772A - High-electromagnetic shielding transparent sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high-electromagnetic shielding transparent sheet which is more enhanced in electromagnetic shielding properties solving troubles such as poor visibility and Moire fringes without degrading in transparency. SOLUTION: A reticulate copper pattern (for example, a square lattice pattern) P whose main component is copper and a solid transparent conductive thin film layer (for instance, ITO(Indium-Tin Oxide)) are formed on a transparent sheet 1 of PET(polyethylene Terephthalate) so as to be totally 50% or above in light transmittance. It does not matter whether the thin film layer is formed either on or under the reticulate copper pattern P. A dark brown layer 3 of copper oxide or copper sulfide is provided to the surface of the copper pattern P so as to improve it in visibility, and when the copper pattern P is set at 1 to 25 μm in line width, Moire fringes disappear or are reduced. The transparent sheet is used to be suspended at the front of the scope of PDP or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high electromagnetic wave shielding transparent sheet having improved electromagnetic wave shielding as well as transparency.

[0002]

2. Description of the Related Art Electromagnetic waves emitted from various types of electronic information devices, and conversely, electromagnetic waves received from other worlds, have caused problems as malfunctions between devices and adverse effects on the human body. Currently, the electromagnetic wave shielding method generally studied is based on the following two methods.

[0003] One of the methods is to form a conductive fiber having a surface plated with nickel or copper into a mesh shape, and form the mesh into a mesh.
This is a method in which a metal circuit such as copper is provided in a mesh shape by sandwiching between substrates or an adhesive on the substrate, that is, a mesh method.

Another method is a thin film method in which ITO (indium tin oxide), silver, or the like is used and the entire surface of the substrate is coated in a thin film.

[0005]

However, there is the following difference in effect between the mesh method and the thin film method.

That is, the mesh method is generally excellent in electromagnetic wave shielding properties. However, in the case of an electromagnetic wave shielding material which also requires transparency, the electromagnetic wave shielding property and the transparency are in a trade-off relationship, and the transparency is not good. Further, moiré interference fringes are easily generated.

On the other hand, the thin film method is satisfactory in terms of transparency and moiré interference fringes, but is inferior in electromagnetic wave shielding properties, which also has wavelength dependence, and especially in high frequency bands. In addition, when the display back surface of a plasma display (PDP) or the like is viewed through an electromagnetic wave shielding member, visibility is required in addition to transparency, that is, it is easy to view even if viewed for a long time, and the eyes do not have much fatigue. However, this is not satisfied with both methods.

The present inventors have solved the above various problems.
Developed a shielding material with higher transparency and higher electromagnetic wave shielding properties without lowering transparency, and in addition to these characteristics, visibility and non-Moire interference fringe properties to prevent or reduce the occurrence of moiré interference fringes We studied diligently to develop a shield material to be applied. As a result, the following solution has been found and the invention has been made.

[0009]

That is, a transparent sheet having excellent transparency and higher electromagnetic wave shielding properties, which is a main object of the present invention, is solved by providing claim 1. That is, on the transparent sheet (1), a mesh-like copper pattern (P) containing copper as a main component and a transparent conductive thin film layer (2) such that the total light transmittance (hereinafter abbreviated as Tt) becomes 50% or more. ) Is a high electromagnetic wave shielding transparent sheet provided with at least two layers.

A second aspect of the present invention provides a solution to the problem of visibility which makes the main problem more visible. That is, this is because a brown to black colored layer (3) is further added to the surface of the mesh copper pattern (P).

With respect to the moire interference fringe which is a further problem, this phenomenon is that a square or rectangular lattice pattern in a mesh copper pattern (P) is more likely to occur than other shapes. According to claim 5, in particular, the line width of the pattern is 1 to 25 μm and the aperture ratio is 5
The solution is achieved by setting the content to 6 to 96%.

It is to be noted that claims 3 and 4 and claim 6 are provided as preferred embodiments as dependent inventions to the above claims 1 and 2. Hereinafter, the present invention will be described in more detail.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, a transparent sheet (1) serving as a base of the transparent sheet having high electromagnetic wave shielding properties according to claims 1 to 6.
Has a total light transmittance Tt of about 60% or more, preferably 65% or more.
% Of a transparent inorganic glass or a synthetic resin, or a film or plate having a thickness of about 0.05 to 5 mm. In particular, in the case of a synthetic resin sheet, it is preferable that the sheet has excellent heat resistance, weather resistance, non-shrinkage, chemical resistance, and other mechanical strengths. The synthetic resin sheet may be a thermosetting resin sheet of acrylic, silicone, urethane or the like, but is preferably a thermoplastic resin sheet because it is difficult to easily obtain a sheet having a desired thickness.

Specifically, a reinforced or non-reinforced inorganic glass plate having a thickness of 1 to 3 mm, or a polymetal acrylate, polystyrene, a copolymer of styrene with acrylonitrile or methyl methacrylate, poly (4-methylpentene-1) , Polypropylene, cyclopentene, norbonene, tetracyclododecane, etc. alone or copolymerized with ethylene, cyclic olefin polymer (amorphous), polyethylene terephthalate, polyether sulfone, polycarbonate, various liquid crystal polymers, etc. 0.0
A thermoplastic resin sheet of 5 to 5 mm, preferably 0.1 to 3 mm can be used.

The transparent sheet (1) is generally a single sheet, but may be a composite transparent sheet obtained by appropriately combining two or more kinds. Then, the sheet itself may be provided with, for example, near-infrared shielding properties and anti-reflection properties.

Then, on the transparent sheet, a mesh-like copper pattern (P) containing copper as a main component and a transparent conductive thin film layer (2)
Will be provided. First, in this formation,
Tt of the final transparent sheet is 50
% Or more, preferably 60% or more. By adopting at least these two components, the electromagnetic wave shielding property and Tt are synergistically improved as compared with the case of each of them alone. It is considered that this synergistic effect is not merely due to the existence of the transparent conductive thin film layer in the opening of the copper pattern, but to the fact that the shape of the copper pattern itself is entangled and acts.

Here, the mesh copper pattern (P) of the mesh will be described. Here, the reason why the material of the pattern is mainly made of copper is that it is more comprehensive (performance, quality, manufacturability, etc.) in terms of imparting an electromagnetic wave shielding property than other metals.
This is because it is the most effective material. Here, the term "mainly composed of copper" means that only copper or an alloy of copper and another metal, for example, Cu / Zn (brass), Cu / Sn (bronze), Cu /
It is meant to include a copper-based binary alloy such as Al, Cu / Ni, Cu / Pb, and Cu / Be, and a copper-based triple alloy such as Cu / Sn / P (phosphor bronze). However, any inconvenience must be avoided for the copper pattern manufacturing means (chemical etching, sputtering, etc.) described later, including these alloys.

Further, the pattern needs to have a mesh shape. This means that a continuous copper continuous line mainly composed of copper is regularly meshed with an opening having a certain shape. This means that the patterns are arranged. Specifically, a lattice copper pattern in which the opening has a square or rectangular shape, a rhombus, a circular shape, or even a copper pattern in a polygonal shape by any of 3 or 5 to 10 can be exemplified. When the rectangular lattice copper pattern is formed into a mesh shape, the above effect is more effectively exhibited, which is preferable.

The reason why the square or rectangular lattice copper pattern is more effective than the mesh copper pattern of other meshes is to obtain higher transparency and to control higher electromagnetic wave shielding properties in a well-balanced manner. Because it is easier.

However, in the lattice copper pattern, for example, P
Moire interference fringes are more liable to occur and stronger fringes than the other mesh patterns when facing the DP screen. This is especially true when the line width of the pattern is 1
The solution is specified as ５６25 μm, and 56-96% of the aperture so that transparency is maintained.
Of course, in the copper mesh pattern of other nets, the line width is not specified, and may be determined appropriately in relation to the effect.
Although moire interference fringes are generally eliminated or reduced by changing the facing angle with a screen such as a PDP, the present invention can eliminate or reduce them regardless of the facing angle.

The line width is 1 to 25 μm, preferably 3 to 2 μm.
0 μm, more preferably 5 to 15 μm, is necessary at least for solving the occurrence of moire interference fringes. Here, as the line width becomes smaller, the effect increases and the aperture ratio also increases, so that the transparency also improves. However, when the line width is less than 1 μm, there is no synergistic effect with the lattice copper pattern in the electromagnetic wave shielding effect, which is not practical. It is not preferable because it becomes the level. On the other hand, when it is larger than 25 μm, moire interference fringes tend to occur, and the aperture ratio becomes smaller, so that T
This is not preferable from the point of t.

Therefore, the line width also affects the transparency, so that the transparency within the line width, that is, Tt corresponds to 56 to 96% in terms of aperture ratio. become. The aperture ratio can be obtained from Equations (1) and (2), but will be described in detail below.

First, the aperture ratio in the case of a square lattice pattern will be described with reference to FIG. In the figure, a portion B indicated by a dotted line and a solid line intersecting each other is a square opening, and this opening B is formed by A having one of the copper patterns as a constituent unit. Therefore, aperture ratio (%)
(56-96%) and the line width have the relationship of Equation 1. Where a
Is 1 to 25 μm, b is the length of one side of the structural unit A (μm)
It is. Note that (ba) in Equation 1 is also called an opening.

[0024]

(Equation 1)

Next, regarding the rectangular lattice copper pattern,
This will be described with reference to FIG. In the figure, the portion indicated by the intersection of the dotted line and the solid line is the opening G, which is formed by H having one of the copper patterns as a constituent unit. Therefore, the aperture ratio (%) (56 to 96%) and the line width have the relationship of Equation 2. However, c and d are 1 to 25 μm and generally c = d, but there are cases where c ≠ d. e and f constitute one unit H with a long side and a short (μm) length, respectively. These two sides may be e> f or e <f. Also, e> d and f> c. In addition, (e−
d) and (fc) are also called opening.

[0026]

(Equation 2)

The thickness of the mesh-like copper pattern must be larger than the thickness of the transparent conductive thin film layer (2) so that the electromagnetic wave shielding effect is maximized. Although it is thick, the effect does not increase even if it is too thick. From such a meaning, it is good to set to about 0.5 to 10 μm, preferably 1 to 7 μm.

Next, the transparent conductive film layer (2) will be described. First, the thin film layer is provided on the entire surface as a lower layer or an upper layer of the mesh-like copper pattern (P). This layer is made of a transparent and conductive material, that is, a conductive material having a lower resistance, but this transparency is such that at least the total Tt is not less than 50% and the Tt is as high as possible. Is preferred. It is also desired that the thin film layer is easily formed and has a sufficient adhesive strength to the transparent sheet (1) and the mesh-like copper pattern (P). Regarding the film thickness, it is not preferable that it is at least conductive, that is, it is not preferable that it is too thin so that the electromagnetic wave shielding effect is not effectively performed. Conversely, if it is too thick, cracks are likely to occur due to impact or bending, so balance these. It is necessary to think and decide, 10
0 to 1500 °, preferably 150 to 1200 °.

Examples of the conductive material which is transparent, has conductivity and is easy to form a thin film layer include simple metals such as silver, platinum, aluminum and chromium, indium oxide, tin dioxide, zinc oxide and cadmium oxide. Metal oxide, indium tin oxide (ITO) in which indium oxide is doped with tin, antimony tin oxide (ATO) in which tin dioxide is doped with antimony, fluorine tin oxide (FTO) in which tin dioxide is doped with fluorine, oxidation Examples include aluminum zinc oxide (AZO) in which zinc is doped with aluminum, and a composite oxide of indium oxide and zinc oxide. Among these, the metal alone has higher conductivity than others, but is inferior in transparency, so that it is necessary to reduce the film thickness in order to increase the transparency. However, when the film thickness is reduced, the conductivity deteriorates. Therefore, the synergistic effect with the mesh copper pattern is also reduced.

Therefore, among the conductive materials exemplified above, those which exhibit conductivity, that is, the transparency and the electromagnetic wave shielding effect in a well-balanced and synergistic manner, are more preferably made of metal oxide or doped metal oxide than metal alone. It is preferable to use ITO as a typical example.

Next, the method for producing the transparent sheet with high electromagnetic wave shielding properties according to claim 1 will be described. However, the production method is not limited, and the following four examples can be given.

In the method of Example 1, an anchor layer (hydrophilic resin) (for example, polyhydroxyethyl acrylate) for forming a plating nucleus for electroless plating is provided on one surface of the transparent sheet (1). The anchor layer is provided with an electroless plating layer for chemical plating using palladium as a catalyst, and the plating layer is treated with an electroless plating solution of copper, and in some cases, is further subjected to copper plating by electrolysis to obtain a 1 to 10 μm
Is provided on the entire surface. Next, using a masking film having a desired mesh pattern, a mesh copper pattern is formed by a general photo-etching method.

Next, a transparent conductive thin film layer (2) is laminated on the entire surface including the mesh-like copper pattern. The method for laminating the thin film layers is not particularly limited, but it is preferable to laminate the layers using a conductive material exemplified above by a physical thin film forming means such as a vacuum deposition method, a sputtering method, or an ion plating method. Among them, the sputtering method is preferable because a high-quality transparent conductive thin film can be formed quickly.

The method of Example 2 is a method using a copper-clad sheet obtained by bonding and laminating a copper foil to the transparent sheet (1).
That is, the copper-clad surface is formed into a desired net-like copper pattern by photoetching in the same manner as in Example 1, and a transparent conductive thin film is provided on the entire surface from above the pattern by physical thin film forming means. .

In the method of Example 3, first, a mesh-like copper pattern (P) provided on the transparent sheet (1) is formed by plating a copper thin film mainly composed of copper as an underlayer,
For example, it is made by plating copper into a thick film by electrolytic plating. Then, a transparent conductive thin film layer (2) is laminated on the entire surface of the formed copper pattern (P) in the same manner as described above. Incidentally, there are the following two methods for forming the copper pattern itself.

One of them is that the transparent sheet (1) has a thickness of 50 to 1 μm, preferably 1 to 50 μm by the physical thin film forming means using the copper material containing copper as a main component.
A thin film layer having a thickness of 00 to 0.7 μm is provided. Next, copper plating is performed on the entire surface of the thin film layer by electrolytic plating, and a thick film layer having a thickness of 1 to 10 μm is laminated. Finally, photo-etching is performed via a photolithography method using a masking film having a desired mesh pattern image. As a result, a mesh-like copper pattern consisting of two layers in which a copper thin film layer is stacked on a copper thin film layer as an underlayer is formed.

The other is a method of forming a physical thin film on the surface of the transparent sheet (1) in the same manner as described above to form a layer mainly composed of copper with a thickness of 50 to 1 μm, preferably 100 to 0.7 μm.
m is provided. Next, the thin film layer is developed by a photolithography method using a masking film having a desired mesh pattern image to expose the pattern portion. That is, here, the non-pattern portion is kept masked by the photosensitive resist. Next, copper is electroplated on the exposed thin film layer of the pattern portion by a plating means to laminate the pattern layer having a thickness of 1 to 10 μm. Next, the resist film remaining on the non-pattern portion is peeled and removed with a solvent.

Finally, the entire surface is chemically etched, and as soon as the thin film layer in the non-pattern portion is dissolved and removed, the etching is stopped immediately. Since the entire surface is chemically etched, the copper by plating which has already formed the pattern is also etched at the same time. However, the thinning of the non-patterned portions is etched much faster, so that the plating reduces the copper in the thick film to a very small extent and remains substantially at the original thickness.

The method of Example 4 is a method in which a transparent conductive thin film layer (2) is provided below and a mesh-like copper pattern (P) is provided thereon. Specifically, first, a transparent conductive thin film (2) is provided on the entire surface of one side of the transparent sheet (1) by using the above-mentioned conductive material by a physical thin film forming means. Next, using a masking film having a desired mesh-like pattern image, development is performed by photolithography to expose a portion corresponding to the pattern. That is, here, the non-pattern portion is in a state of being masked by the photosensitive resist.

Then, copper having a thickness of 1 to 10 μm is electrolytically plated on an exposed portion (transparent conductive thin film portion) for forming the pattern portion. Finally, the remaining resist in the non-pattern portion is removed (or dissolved) and removed. That is, in this method, the transparent conductive thin film layer (2) is provided on the entire surface as a lower layer, and a desired mesh-like copper pattern (P) is provided on the upper layer. In addition, the conductive thin film layer (2)
When electrolytic plating copper on, depending on the material of the thin film layer,
Electroplating environment (electricity, resistance to electrolytic plating solution, etc.), adhesion to copper to be plated, and the like may become a problem. In such a case, it is necessary to carry out various tests in advance to know the pretreatment conditions for adhesion. For example, when the thin film layer is made of ITO, the adhesion to the copper plating layer is weak. Therefore, a method is used in which electroless plating of palladium and nickel is performed on the ITO layer in advance, and copper is electrolytically plated thereon.

However, of the above four examples, either Example 3 or Example 4 is preferable. The reason is as follows. That is, as in Examples 1 and 2, a conductive material is used to provide an adhesive function without providing an adhesive layer, so there is no decrease in transparency due to the adhesive, and the adhesive force is higher and more stable than with the adhesive. Long life. Further, the shielding effect itself is added to the electromagnetic wave shielding effect itself of the thick copper pattern, and a separate process for providing an adhesive layer is not required.

Next, a method for providing the colored layer (3) according to claim 2 will be described. In this method, the surface of the mesh-like copper pattern (P) of the mesh is colored. First, the color of the coloring is particularly selected from brown to black. The mesh-like copper pattern of the mesh colored with this color gives the gentleness to the eyes when viewing a screen of a PDP or the like through this, because it is easier to see than other colors and the eyestrain is small even if the user stares for a long time. This provides visibility in a different sense from moiré interference fringes. Here, the meaning of brown to black may be a single color of brown or black, or may be a mixture of both colors as appropriate, and preferably a mixture of strong black and black brown.

Specific examples of the coloring method include the following Examples 5 to 7, but are not limited thereto. First, as Example 5, a method of thinly coating the surface of a mesh-like copper pattern (P) with a coating resin solution prepared by mixing a brown to black pigment with a coating resin. In Example 6, a photosensitive resist used for forming a mesh-like copper pattern (P) by using a photo-etching method is colored in advance, and the resist remaining on the copper pattern is not peeled off as it is. How to leave.

Example 7 is a chemical method in which the mesh-like copper pattern (P) is oxidized or sulfurized to change the surface to copper oxide or copper sulfide. However, of these three examples, the method of Example 7 is preferred. It is the other two
Since the coloring layer is formed integrally with the copper pattern on the surface as compared with the method, there is no fear of peeling off at the interface. This is because the thickness of the copper oxide layer or the copper sulfide layer can freely change the color tone by simply changing the oxidation or sulfidation treatment conditions.

The oxidation treatment can be easily carried out simply by immersing the obtained mesh-like copper pattern (P) in an aqueous solution obtained by making sodium chlorite alkaline with sodium hydroxide, that is, an alkaline strong oxidizing agent aqueous solution. Can be changed to copper. The conditions (temperature, immersion time, alkali concentration, chlorite concentration, etc.) at this time are preferably tested in advance to determine the optimum conditions. In the sulfurizing treatment, for example, an aqueous solution containing sulfur or an inorganic compound thereof (eg, potassium sulfide) as a main component is brought into contact with the copper pattern surface. Here, in the case of using sulfur, since it is not efficient by itself, quick lime, casein and, if necessary, potassium sulfide are further added as an auxiliary agent to form an aqueous solution. On the other hand, in the case of potassium sulfide, an aqueous solution is formed using ammonium chloride or the like in combination to promote the reaction. In each case, the contact time and temperature are appropriately determined by experiments. The thickness of the surface layer made of copper oxide or copper sulfide can be freely changed depending on the oxidation or sulfidation conditions.
If the thickness is too large, the electrical resistance value of the copper pattern increases, and as a result, it tends to lower the electromagnetic wave shielding effect. Its electric resistance value is about 200 mΩ / dish,
The copper oxide or copper sulfide layer should be as thin as possible so as not to exceed this.

The transparent conductive thin film layer (2) provided on the entire surface
May be provided as a lower layer or an upper layer of the mesh-like copper pattern (P) of the mesh as described above, but may be provided in both upper and lower layers with the pattern interposed therebetween. In the case of both layers, further improvement in electromagnetic wave shielding properties and protection of the pattern are expected.

[0047]

The present invention will be described in more detail with reference to the following examples together with comparative examples. In the text, the electromagnetic wave shielding property referred to in the example,
The total light transmittance Tt (%) and the moire interference fringes were obtained by the following measuring methods.

The electromagnetic wave shielding property can be measured at a frequency of 100 to 1000 MHz by a measuring device according to the Kansai Electronics Industry Promotion Center method (generally called the KEC method).
(DB) of electromagnetic wave measured in the range (megahertz)
-DB).

The total light transmittance Tt is determined according to JIS K7105.
It is a transmittance (%) measured by a turbidimeter type NDH-20D manufactured by Nippon Denshoku Industries Co., Ltd. based on (1981).

The moire interference fringes were obtained by applying the obtained high electromagnetic wave shielding transparent sheet to the entire surface of the screen of a commercially available PDP with a gap 10.
It was visually determined whether or not moiré interference fringes appeared when the lens was suspended and set in mm. The degree of occurrence was evaluated on a three-point scale. 場合 indicates that no occurrence occurred, 若干 indicates that slight occurrence occurred, but 場合 indicates that the amount was slight and did not cause a practical problem, and x indicated that the occurrence was obvious and caused a practical problem. did. Note that the aperture ratio was determined by Equation 1 or Equation 2 described in the text.

Example 1 First, a transparent sheet having a thickness of 125 μm, a size of 400 × 1000 mm, and a Tt of 90%
Of the above-mentioned biaxially stretched polyethylene terephthalate film (hereinafter referred to as PET film), and one surface thereof was pretreated by glow discharge. Then, the pre-treated PET film was placed in a vacuum chamber of a magnetron type sputtering apparatus by an IT
It is placed facing O (target), and under the following conditions, ITO
And an ITO thin film was sputter-deposited on the entire surface. -Sputtering operation pressure: Degree of vacuum obtained by replacing the inside of the vacuum chamber with argon gas containing 4.5% oxygen 2
× 10 ^-3 Torr ・ Sputtering temperature ・ ・ ・ ・ 90 ℃ ・ Sputtering time ・ ・ ・ ・ 4 seconds The thickness of the ITO thin film layer formed by this sputter deposition is 200 ° and the surface resistance value is 400Ω / evil. ,
Tt was 88.9%.

Next, a positive photoresist was coated on the surface of the ITO thin film by a roll coater to a thickness of 2 μm. Then, a line width of 15 μm and a pitch of 150 μm
Using a negative film for a mask having a square grid pattern image made with m, the film was irradiated with ultraviolet rays at an intensity of 130 mJ / cm ² while being vacuum-contacted with the coating surface. Then, a pattern portion corresponding to the pattern image irradiated with ultraviolet light was developed and peeled off.
Therefore, the resist in a portion corresponding to the non-pattern image remains and is masked. Hereinafter, this is called an ITO pattern PET film.

Next, the ITO pattern PET film was first manufactured by palladium electroless bath bath ore metal plating Co., Ltd., product number CG-535A, pH = 3-3.
5) at room temperature for 1 minute, and after sufficient washing, this time immersion in a nickel electroless bath stamping metal plating Co., Ltd., product number Nikom N, pH = 4.5-5) at 70 ° C. for 5 minutes Thus, a nickel layer was provided. The palladium electroless and the nickel electroless are, as described above, a base layer for a subsequent copper electrolytic plating (in this case, a layer thickness of 0.2 μm).
m), with the intervention of ITO
The pattern layer and the thick film layer formed by copper plating adhere to each other to form a stronger copper pattern. Therefore, this underlayer is made of a transparent conductive thin film layer (2) provided on the entire surface.
O is an example of pre-processing performed when it is provided as a lower layer. If the thin film layer is of a type other than ITO, the contents of the pre-processing (the pre-processing may not be performed, or other methods may be used) Is different.

Next, the ITO pattern layer having the underlayer is used as a cathode and immersed in a plating bath using a mixed aqueous solution of copper sulfate and sulfuric acid as a cathode.
/ Dm ² , plating rate 0.28 μm / min).
The thickness of the copper laminated by this plating is 1.1 μm
Met. Hereinafter, this is referred to as a copper plating pattern PET film.

Next, the resist film remaining on the non-patterned portion of the copper-plated PET film was dissolved and removed with acetone. As a result, the entire surface of the ITO transparent conductive thin film layer as the lower layer and the square lattice copper pattern as the upper layer are formed on the PET film. The line width of the obtained pattern was 14 μm, and other electromagnetic wave shielding properties, Tt, and Moire interference fringes are summarized in Table 1. Note that the aperture ratio is obtained by Equation 1.

[0056]

[Table 1]

Example 2 The PET film having the square lattice copper pattern obtained in Example 1 was oxidized under the following conditions to color the copper surface of the pattern. Then, a black-brown colored layer 3 was formed.
That is, the whole PET film was immersed in a bath of a mixed aqueous solution obtained by dissolving sodium hydroxide and sodium chlorite heated to 70 ° C. in water for 5 minutes, taken out, washed and dried. The surface of the copper pattern was oxidized and turned into a black-brown copper oxide layer. The thickness of the copper oxide colored layer is 0.8
μm. This and Example 1 were suspended from the PDP, and the displayed images were viewed. As a result, in this example, the first time, the first time, the user felt feeling calm and looked at the subject for a long time, but did not feel tired. The other electromagnetic wave shielding properties, Tt, and moire interference fringes were not different from those in Example 1.

FIG. 1 shows the structure of the first embodiment and the second embodiment together. That is, 1
Is a PET film, and 2 is an I film provided on the entire surface as a lower layer.
TO transparent thin film layer, P is copper pattern layer by electrolytic plating,
3 is a black-brown colored layer made of copper oxide.

Example 3 Four PET films were prepared as in Example 1 and pretreated by glow discharge. Then, each of the pretreated PET films was placed in a vacuum chamber of a magnetron sputtering apparatus so as to face a copper target, and the air in the chamber was completely replaced with argon gas to obtain a degree of vacuum of 2 × 10 2. ^At an operating pressure of ^-3 torr, sputtering is performed while running at a speed of 1 m / min with an input power of 9 kW (DC), and this is repeated three times to obtain a film having a film thickness of 0.12 μm (± 0.01). A thin layer of copper was deposited. In addition, cut out a part of each,
A bending test at 180 ° C. was performed, but none of the thin films was peeled off from the PET film surface.

Next, the copper thin film surfaces of the four PET films obtained above were processed by photolithography to change them into square lattice patterns having different aperture ratios. That is, first, a positive resist (photo-decomposable type) was coated on the thin film surface at 2 μm, and the coated surface was fixed at a line width of 15 μm and the pitch was changed to 100 μm, 150 μm, 200 μm and 250 μm, respectively. Used, vacuum adhered to each, 110mJ / cm
Irradiation with UV light source No. ² was performed. Then, the exposed portion of the resist in the pattern portion was developed and dissolved and removed (the resist in the non-pattern portion remained tightly adhered).

Next, copper is electrolytically plated on the obtained copper thin film layer having a square lattice pattern formed on each of the four PET films under the following conditions, and a thick copper film is laminated.
A copper pattern was formed, and finally, the remaining resist film in the non-pattern portion was dissolved and removed. That is, using the pattern as a cathode,
Using a mixed aqueous solution of copper sulfate and sulfuric acid as a plating bath, and using this as an anode, electrolytic plating was performed at a bath temperature of 23 ° C., a current density of 1.7 A / dm ² , and a plating speed of 0.3 μm / min. The thickness of the copper pattern formed by this electrolytic plating is uniformly 2.
It was 5 μm.

Next, the four PET films having the copper pattern formed on the copper thin film were chemically etched under the following conditions to dissolve and remove the copper thin film layer in the non-pattern portion. That is, each of the four PET films was entirely set in an etching apparatus, and contacted with a hydrogen peroxide / sulfuric acid-based etching solution at 20 ° C. for 30 seconds. Since the copper thin film in the non-pattern portion was dissolved and removed, the etching was immediately stopped, washed with water and dried. The thickness of the copper pattern thus obtained was uniformly 2.41 (± 0.01) μm. This thickness is equal to the thickness before etching (2.5 μm).
It can be seen that there is no substantial difference from m). This means that the copper pattern portion is also etched at the same time as the non-pattern portion of the copper thin film, but there is a large difference in the film thickness of both, and there is a difference in the quality of both copper films. Is considered to have been etched. The reduction in line width was smaller than that of the copper pattern according to the method of Example 1, and was reproduced one-to-one. Next, quicklime, casein and potassium sulfide were added to sulfur as a main component and dissolved in distilled water. This was used as a sulfurizing bath at 40 ° C., indirectly in contact with the copper pattern surface for about 60 seconds, and then washed with water and dried. The surface was colored and blacker and sharper than the color of the copper oxide layer of Example 2.

Next, ITO was sputtered on each of the PET films having the obtained colored copper patterns so as to cover the copper patterns and cover the entire surface. The sputtering conditions here were the same as in Example 1, except that the sputtering time was 8 seconds. The film thickness of the sputter-deposited ITO was 410 °, and the surface resistance value was 300 Ω / cm.

With respect to the obtained four sheets, the electromagnetic wave shielding property with respect to the line width / pitch of the formed copper pattern, T
The t and moiré interference fringes were measured and are summarized in Table 1.

(Comparative Example 1) (In Case of Only Copper Pattern) In Example 3, copper patterns were formed on a PET film under exactly the same conditions except that no ITO thin film layer was provided, and four types of square copper patterns were formed. Were produced. Example 3 for each PET film
The results were measured in the same manner as in Example 1 and the results are summarized in Table 1.

(Comparative Example 2) (In the case of using only the ITO thin film layer) The same PET film as used in Example 1 was used, pretreatment was similarly performed by glow discharge, and the treated surface was used in Example 3 Under the same conditions as above, ITO was sputtered over the entire surface to provide an ITO thin film layer having the same film thickness. The obtained PET film having only the ITO transparent thin film layer was measured in the same manner as in Example 3, and the results are summarized in Table 1.

(Comparative Example 3) (When the line width of the square lattice copper pattern is wider than 25 μm) Except that a negative film for a mask having a square lattice pattern image produced with a line width of 30 μm and a pitch of 180 μm is used. The procedure was performed under the same conditions as in Example 1, and an ITO thin film layer was entirely laminated on a PET film, and a copper lattice pattern was sequentially laminated thereon. The obtained product was measured in the same manner as in Example 1 and summarized in Table 1. Moire interference fringes are observed.

As is evident from Table 1, first, it is understood that the shielding effect of the electromagnetic wave is much higher when the copper pattern is used alone and when the ITO thin film is used alone than when both are used. Furthermore, especially at electromagnetic wavelengths higher than 100 MHz, a synergistic effect appears, which is a surprising result. Further, in the balance between the transparency and the electromagnetic wave shielding property, even if the transparency is increased, the decrease in the electromagnetic wave shielding property is small with respect to the increased transparency. This does not reduce the electromagnetic shielding properties,
It is highly evaluated as being able to increase transparency.

[0069]

The present invention is configured as described above, and has the following effects.

First, the effect of shielding the electromagnetic wave is greatly improved as compared with the case of each alone (only the copper pattern and only the transparent conductive thin film layer), and is synergistically improved particularly in a high electromagnetic wavelength region.

The transparency can be increased without lowering the electromagnetic wave shielding effect. This overturns the fact that the two are generally in conflict.

Visibility is imparted by further providing a brown to black colored layer on the surface of the mesh-like copper pattern. Further, occurrence of moiré interference fringes particularly in the case of a square or rectangular lattice copper pattern can be eliminated or reduced by specifying the line width of the pattern.

By having the above-described effects, the use thereof is further expanded to use as an electromagnetic wave shielding member of electronic equipment, such as PDPs and CRTs which generate electromagnetic waves.

[Brief description of the drawings]

FIG. 1 is a perspective sectional view showing a transparent sheet having high electromagnetic wave shielding properties obtained in Examples 1 and 2.

FIG. 2 is a plan view showing a case where the mesh copper pattern of the mesh is a square lattice pattern.

FIG. 3 is a plan view showing a case where the mesh copper pattern of the mesh is a rectangular lattice pattern.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 PET film 2 ITO transparent thin film layer P Copper pattern layer 3 Copper oxide coloring layer A Square copper pattern constituent unit B Square opening H Rectangular copper pattern constituent unit G Rectangular opening

Claims (6)

[Claims] 1. A transparent sheet (1) having a total light transmittance of 5
A high electromagnetic wave shielding transparent sheet comprising a mesh-like copper pattern (P) containing copper as a main component and a transparent conductive thin film layer (2) so as to be 0% or more. 2. The high electromagnetic wave shielding transparent sheet according to claim 1, wherein a brown to black colored layer (3) is further provided on the mesh-like copper pattern (P). 3. The high electromagnetic wave shielding transparent sheet according to claim 2, wherein the brown to black colored layer (3) is made of copper oxide or copper sulfide. 4. The transparent sheet (1) has a total light transmittance of 60.
% Of the thermoplastic resin sheet.
The transparent sheet with high electromagnetic wave shielding properties according to any one of the above. 5. The mesh-like copper pattern (P) of the mesh has a line width of 1 to 5.
The high electromagnetic wave shielding transparent sheet according to any one of claims 1 to 4, wherein the transparent sheet has a square or rectangular lattice pattern having an opening ratio of 25 µm and an aperture ratio of 56 to 96%. 6. The transparent conductive thin film layer (2) has a thickness of 10
The high electromagnetic wave shielding transparent sheet according to any one of claims 1 to 5, wherein the angle is 0 to 1500 °.