JP2004095829A - Electromagnetic wave shield transparent sheet and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electromagnetic wave shield transparent sheet having excellent transparency as well as shielding characteristics and excellent in thread workability. <P>SOLUTION: The electromagnetic wave shield transparent sheet is provided on a transparent substrate with a conductive pattern having a metal layer. In this case, the thickness of the metal layer is 0.01-1μm, the linear width of the conductive pattern is 1-10μm, the pitch width of the same is 5-200μm and a ratio of the pitch width to the linear width is 5-40. <P>COPYRIGHT: (C)2004,JPO

Description

【００７７】
図４、図５及び表１に示される結果から明らかなように、本発明のシートはシート抵抗値が高いにも関わらず、良好なシールド特性を有していることが明らかとなった。特に、ＰＤＰの放射ノイズで問題視されている周波数帯（３０〜３００ＭＨｚ）の電磁波が、顕著にシールドされることが明らかとなった。
【００７８】
実施例２
ＰＤＰの前面に、前記実施例１で作成した電磁波シールド透明シートを設置したところ、モアレが発生しなかった。更に、ＰＤＰとの対面角度を４５度ずらして設置しても、モアレが発生しなかった。このことから、本願発明によって、モアレ現象が軽減又は消失されることが明らかとなった
【００７９】
【発明の効果】
本願発明は、上述のような構成を有することによって、細線加工が可能となり、しかも、良好な透明性及びシールド特性を有するという優れた効果を奏する。特に、本願発明においては、低周波領域の電磁波が格段にシールド（遮蔽）されるという、従来技術からは予測できない有利な効果を奏する。
【００８０】
また、本願発明は、微細な細線加工が可能となったことで、モアレ現象が軽減又は消失するという効果も奏する。これによって、従来のような、モアレを解消するための角度の調整が必要なくなり、ＰＤＰ等の機種毎にバイアス角度の調整も不要となる。
【００８１】
更に、本発明のシートの製造に際しては、メッキ等の複雑な工程を必要せず、容易に、しかも、安易に電磁波シールド透明シートが得られるという利点も有する。また、厚さが薄くなったことにより、粘着フィルムとの貼り合わせの際の気泡かみ込みの問題が軽減されるという利点も有する。
【００８２】
本願発明の透明シートは、このような優れた物性を有していることから、ＰＤＰ等の電磁波発生機器からの電磁波シールド用として有用である。
【図面の簡単な説明】
【図１】図１は、パターンが正方形格子パターンである場合の構成を平面図で示した図面である。
【図２】図２は、シート抵抗値を算出するためのモデル回路を示した図面である。
【図３】図３は、（イ）〜（ニ）の各工程で処理されて得られる本発明のシートの構造を断面図で示した図面である。
【図４】図４は、本発明の実施例の電磁波シールド特性を示す図面である。
【図５】図５は、比較例の電磁波シールド特性を示す図面である。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an improved electromagnetic wave shielding transparent sheet and a method for manufacturing the same. In particular, the present invention relates to an electromagnetic wave shielding transparent sheet for electronic information equipment such as a plasma display (PDP).
[0002]
[Prior art]
Electromagnetic waves emitted from various electronic information devices, and conversely, electromagnetic waves received from other worlds, have become a problem as factors that cause malfunctions of the devices.
[0003]
Various measures have already been proposed and implemented for measures to prevent equipment failure due to electromagnetic waves. For example, in an electronic information device such as a plasma display, since an electromagnetic wave emitted from the inside through a screen becomes an obstacle, a method of loading an electromagnetic wave shielding material on the screen is generally adopted. In such a case, the shielding material must not be opaque, but must be transparent and effectively shield electromagnetic waves.
[0004]
Conventionally, as an electromagnetic wave shielding member having transparency, a copper foil having a thickness of 10 to 40 μm was pasted on a transparent substrate, and then patterned by a photolithography method, and then removed by etching to form a pattern on the sheet. Shield members and the like have been proposed.
[0005]
However, although the copper foil having the above-mentioned thickness has good shielding properties, there is a limit to thinning of the pattern, and there are also problems such as a decrease in overall transparency and visibility.
[0006]
[Problems to be solved by the invention]
The main object of the present invention is to provide an electromagnetic wave shielding transparent sheet having good transparency and shielding properties and excellent in fine wire workability.
[0007]
[Means for Solving the Problems]
The inventor of the present invention has made intensive studies with the main object of solving the above problems. As a result, by setting the thickness of the metal layer, the line width, the pitch width, and the ratio of the line width to the pitch width in a specific range, the electromagnetic wave having excellent transparency and shielding properties, and excellent fine wire processability. The inventors have found that a shield transparent sheet can be obtained, and have further studied, and completed the present invention.
[0008]
That is, the present invention relates to the following matters.
1. An electromagnetic wave shielding transparent sheet having a conductive pattern formed of a metal layer on a transparent substrate, wherein the thickness of the metal layer is 0.01 to 1 μm.
2. 2. The electromagnetic wave shielding transparent sheet according to 1, wherein the conductive pattern has a line width (a) of 1 to 10 μm.
3. 3. The electromagnetic wave shielding transparent sheet according to any one of 1 and 2, wherein the pitch width (b) of the conductive pattern is 5 to 200 μm.
4. 4. The electromagnetic wave shielding transparent sheet according to any one of 1 to 3, wherein a ratio (b / a) of a pitch width to a line width of the conductive pattern is 5 to 40.
5. 5. The electromagnetic wave shielding transparent sheet according to any one of 1 to 4, wherein the aperture ratio of the conductive pattern is 64 to 95%.
6. 6. The electromagnetic wave shielding transparent sheet according to any one of 1 to 5, which has a sheet resistance of 0.08 to 50 Ω / □.
7. The electromagnetic wave shielding transparent sheet according to any one of 1 to 6, which is obtained by sequentially performing the following steps (a) to (d).
(A) forming a metal layer on one surface of a transparent substrate by a thin film forming means;
(B) developing the metal layer by photolithography to expose a non-conductive pattern portion;
(C) a step of chemically etching the non-conductive pattern portion to dissolve and remove the metal layer;
(D) removing and removing the remaining resist of the conductive pattern;
8. (4) A method for producing an electromagnetic wave shielding transparent sheet, comprising sequentially performing the following steps (a) to (d).
(A) forming a metal layer having a thickness of 0.01 to 1 μm on one surface of the transparent substrate by a thin film forming means;
(B) developing the metal layer by photolithography to expose a non-conductive pattern portion;
(C) a step of chemically etching the non-conductive pattern portion to dissolve and remove the metal layer;
(D) removing and removing the remaining resist of the conductive pattern;
9. (I) A composite sheet having a shield layer comprising the electromagnetic wave shielding transparent sheet according to any one of (1) to (7), (ii) an antireflection layer, and (iii) a near-infrared cut layer.
[0009]
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Hereinafter, the present invention will be described specifically.
[0010]
Conductive pattern
The conductive pattern has a geometric shape in which openings having a certain shape are repeated vertically and horizontally continuously, and has a metal layer made of a conductive metal.
[0011]
The shape of the opening is not particularly limited, and examples thereof include a square, a rectangle, 3 or 5 to 10 regular polygons, a circle, and a rhombus. Among them, those having a square shape are preferable because they can easily achieve both transmittance and shielding performance.
[0012]
Here, the line width, the pitch width, the ratio of the pitch width to the line width, and the aperture ratio in the present invention will be described with reference to FIG. 1 by taking a square lattice pattern as an example.
[0013]
In FIG. 1, the opening B is formed by A having one of the copper patterns as a constituent unit. a is the line width, which indicates the width of the line forming one side of the structural unit A. b is a pitch width, which indicates the length of one side of the structural unit A. The ratio of the pitch width to the line width is represented by b / a.
[0014]
The aperture ratio (%) and the line width and the pitch width have the following relationship (1).
[0015]
Formula 1: Opening ratio (%) = 100 × (ba)²/ B²
In the present invention, the line width (a) of the conductive pattern is 1 to 10 μm, preferably 1 to 7 μm, and more preferably 2 to 5 μm. If the line width is too large, it is not preferable in terms of Moire interference and light transmittance, and if it is too small, it is not preferable in terms of shielding characteristics.
[0016]
The pitch width (b) of the conductive pattern is 5 to 200 μm, preferably 5 to 150 μm, and more preferably 10 to 100 μm. If the pitch width is too large, it is not preferable in terms of shielding characteristics, and if it is too small, it is not preferable in terms of light transmittance.
[0017]
The ratio (b / a) of the pitch width to the line width of the conductive pattern is 5 to 40, preferably 10 to 30, and more preferably 15 to 25. If the ratio of the pitch width to the line width is too large, it is not preferable in terms of the shield characteristics, and if it is too small, it is not preferable in terms of Moire interference and light transmittance.
[0018]
Further, the opening ratio of the conductive pattern is 64 to 95%, preferably 75 to 95%, and more preferably 85 to 95%. If the aperture ratio is too large, it is not preferable in terms of shielding performance, and if it is too small, it is not preferable in terms of light transmittance.
[0019]
Metal layer
In the present invention, the thickness of the metal layer is 0.01 to 1 μm, preferably 0.05 to 0.5 μm, and more preferably 0.05 to 0.1 μm. If it is too thick, it is not preferable in performing patterning for thinning. On the other hand, if it is too thin, it is not preferable in terms of shielding performance.
[0020]
In the present invention, since the thickness of the metal layer is thinner than the conventional one, it is possible to make the pattern thinner, and there is an advantage that moire interference is reduced and eliminated.
[0021]
The material of the metal layer is not particularly limited as long as it can be used as a conductive metal, and examples thereof include copper, gold, silver, aluminum, nickel, tin, chromium, and alloys thereof. . Among them, copper, gold, silver, aluminum, nickel or an alloy thereof is preferable, and particularly copper or an alloy thereof is preferable.
[0022]
The copper is preferably pure copper as much as possible. The alloy is an alloy mainly composed of copper, for example, Cu / Zn (brass), Cu / Sn (bronze), Cu / Al, Cu / Ni, Cu / Pd, phosphor bronze, Cu / Be, etc. Can be suitably used.
[0023]
Further, the metal layer is not limited to a single metal layer, but may be a stacked layer. For example, a two-layer, three-layer, or multi-layered layer having a structure of chromium + copper or chromium + copper + chromium can be exemplified. At this time, in the metal layer disposed as the outermost layer, a metal having a function of correcting the color from white to a black system color or a function of protecting the intermediate layer against the environment is selected in order to maintain good visibility. Is preferred.
[0024]
Transparent substrate
The shape of the transparent substrate can be set as appropriate according to the intended use. Usually, it is used as a flat sheet, but depending on the application, it may be bent, or may be used as a film or plate. The thickness of the transparent substrate is usually about 0.05 to 5 mm, preferably about 0.1 to 0.3 mm.
[0025]
Examples of the material of the transparent substrate include inorganic substances such as glass, polymethyl methacrylate, polystyrene or a copolymer of styrene and acrylonitrile or methyl methacrylate, poly (4-methylpentene-1), polypropylene or cyclopentene, norbornene, or tetracyclo. Thermoplastic resins such as amorphous cyclic olefin polymer, polyethylene terephthalate, polyethylene naphthalate, polyarylate, polyether sulfone, polycarbonate, various liquid crystal polymers, etc., by homopolymerization with cycloolefin monomer such as dodecane or copolymerization of ethylene etc., acrylic And urethane-based, epoxy-based and silicone-based thermosetting transparent resins. These may be used in combination of two or more.
[0026]
What is selected for the transparent substrate can be appropriately set according to various uses, but it is preferable that the total light transmittance is 50% or more, preferably 70% or more, and more preferably 90% or more. . The larger this value is, the more transparent and excellent the visibility is. Further, those having excellent heat resistance, weather resistance, non-shrinkage, mechanical strength, chemical resistance and the like are preferable.
[0027]
Electromagnetic wave shielding transparent sheet
The sheet resistance of the electromagnetic wave shielding transparent sheet of the present invention is from 0.08 to 50 Ω / □, preferably from 0.4 to 10 Ω / □, more preferably from 0.6 to 6 Ω / □.
[0028]
If the sheet resistance value is too large, it is not preferable in terms of shielding characteristics.
[0029]
Here, the sheet resistance value will be described with reference to FIG. The sheet resistance value (Rs) of the entire metal layer is obtained by the following equation. ρv is the volume resistivity, and t is the thickness of the metal layer.
[0030]
Equation 2: Rs = ρv / t
Next, in obtaining the sheet resistance value after pattern formation, a configuration unit having a resistance value r (Ω) as shown in FIG. 2 will be considered. For example, a sheet resistance value R (Ω / □) having a pattern in which this constituent unit is composed of 2 × 2 is considered that the resistance in the vertical direction is equipotential (for example, no current flows between AB and BC). Therefore, it can be ignored and can be obtained from the combined resistance of the 2 × 2 equivalent circuit. That is, the relational expression of R (Ω / □) = r (Ω) holds. This relational expression holds even if the constituent units are expanded to n × n. This r (Ω) is obtained from the relationship expressed by Equation 3 from the pattern pitch width b, the line width a, and the sheet resistance value Rs of the entire metal layer.
[0031]
Equation 3: r = Rs × (b / a)
Finally, the sheet resistance value R after pattern formation is obtained from R (Ω / □) = Rs × (b / a). For reference, even when the pattern is inclined by 45 °, the relational expression of R = r can be obtained from the constituent units shown in the figure by an equivalent circuit. When a sheet resistance value is required as the characteristic value, the sheet resistance after pattern formation can be arbitrarily designed based on the sheet resistance value of the base material before pattern formation and the designed line width and pitch width.
[0032]
The specific volume resistivity (ρv) of the metal is, specifically, chromium 12.9 × 10^-6Ωcm, nickel 6.84 × 10^-6Ωcm, tin 11.0 × 10^-6Ωcm, aluminum 2.65 × 10^-6Ωcm, gold 2.35 × 10^-6Ωcm, silver 1.59 × 10^-6Ωcm, copper 1.67 × 10^-6Ωcm.
[0033]
Although the electromagnetic wave shielding transparent sheet of the present invention may be used alone, it may also be used as a composite sheet in which (i) a shield layer made of the sheet, (ii) an antireflection layer and (iii) a near infrared cut layer are laminated. Good.
[0034]
The composite sheet can be used as a filter for an image display device such as a PDP.
[0035]
The anti-reflection layer is a layer intended to suppress the reflection on the surface and improve the transmittance of the filter, and includes a metal oxide, a fluoride, a silicide, a boride, a carbide, a nitride, and a sulfide. A method of laminating an inorganic substance in a single layer or a multilayer by a vacuum deposition method, a sputtering method, an ion plating method, an ion beam assist method, etc., and laminating a resin having a different refractive index such as an acrylic resin or a fluororesin in a single layer or a multilayer. It can be formed by a method or the like. Further, an anti-glare layer (non-glare layer) may be laminated. The non-glare layer is a layer intended to increase the viewing angle of the filter, and is formed by, for example, a method of forming a powder such as silica, melamine, or acrylic into an ink and coating the surface to scatter transmitted light. be able to. The ink can be cured by heat or light.
[0036]
The near-infrared cut layer is provided on the front of the display for the purpose of preventing malfunctions in remote control and transmission optical communication due to near-infrared rays emitted from the plasma display. The cut region of the near-infrared light has a wavelength of 800 to 1000 nm for a remote controller or a transmission optical communication as a wavelength that is particularly problematic, and a near-infrared absorbing material having absorption in that region is used. Examples of the near-infrared absorbing material include nitroso compounds and metal complex salts thereof, cyanine compounds, dithiol nickel complex salt compounds, aminothiol nickel complex salt compounds, phthalocyanine compounds, triallylmethane compounds, immonium compounds, diimmonium compounds. , Naphthoquinone-based compounds, anthraquinone-based compounds, amino compounds, near-infrared-absorbing dyes such as aminium salt-based compounds, or carbon black, or near-infrared-absorbing compounds such as indium tin oxide and antimony tin oxide can be used alone or in combination. it can.
[0037]
The near-infrared cut layer can be formed by adding a near-infrared absorbing substance to the pressure-sensitive adhesive layer. Examples of the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer include rubbers such as styrene-butadiene rubber, polyisobutylene, natural rubber, neoprene, and butyl rubber, and alkyl polyacrylates such as polymethyl acrylate, polyethyl acrylate, and polybutyl acrylate. And the like, or a polymer obtained by adding piccolite, polypropylene, rosin ester or the like as a tackifier thereto.
[0038]
When attaching the filter to the plasma display, if bubbles enter between the surface of the plasma display and the filter, the image will be distorted and it will be difficult to see it. There is a need to. Further, since the surface of the plasma display itself becomes high in temperature, an adhesive which generates gas by heating should be avoided.
[0039]
Specifically, a polymer-based pressure-sensitive adhesive such as a polyacrylate alkyl ester-based or a rubber-based pressure-sensitive adhesive such as styrene-butadiene rubber or natural rubber is used for halogen-based, alcohol-based, ketone-based, ester-based, ether-based, or aliphatic Hydrocarbons, aromatic hydrocarbons and other organic solvents are dispersed or dissolved in a single or mixed solvent system to adjust the viscosity, and the viscosity is adjusted by dipping, flow coating, spraying, bar coating, gravure coating, etc. Then, coating is performed by a coating method such as a roll coating method, a blade coating method, and an air knife coating method, and then the solvent is dried to form an adhesive layer.
[0040]
At this time, the thickness of the pressure-sensitive adhesive layer is usually 5 to 100 μm, preferably 10 to 50 μm. A release film may be provided on the surface of the pressure-sensitive adhesive layer, and the pressure-sensitive adhesive layer may be protected until the pressure-sensitive adhesive layer is attached to the surface of the plasma display so that dust and the like do not adhere to the pressure-sensitive adhesive layer.
[0041]
The composite sheet of the present invention can further be provided with a hard coat layer, a contamination prevention layer, and the like, if necessary.
[0042]
Further, the composite sheet of the present invention may be bonded to a support such as tempered glass and used in the form of a laminated sheet.
[0043]
Method for manufacturing electromagnetic wave shielding transparent sheet
The electromagnetic wave shield of the present invention is formed by sequentially performing the following steps (a) to (d).
(A) forming a metal layer having a thickness of 0.01 to 1 μm on one surface of the transparent substrate by a thin film forming means;
(B) developing the metal layer by photolithography to expose a non-conductive pattern portion;
(C) a step of chemically etching the non-conductive pattern portion to dissolve and remove the metal layer;
(D) removing and removing the remaining resist of the conductive pattern;
[0044]
First, the step (a) will be described.
[0045]
In the step (a), a metal layer having a thickness of 0.01 to 1 μm is formed on one surface of the transparent substrate by physical means.
[0046]
Here, the thin film forming means is a generally used thin film forming technique, such as a chemical thin film forming means or a physical thin film forming means. Specific examples of the chemical thin film forming means include a plating method and a CVD method. Examples of the physical thin film forming means include a sputtering method, a vacuum deposition method, and an ion plating method.
[0047]
These are commonly used to convert the metal or nonmetal into a gas or ion state by some method, receive it on the surface of a transparent substrate, and deposit it into a thin film. Use copper or its alloy.
[0048]
Among the thin film forming means, a sputtering method or an ion plating method is preferable from the viewpoint of adhesion to a substrate.
[0049]
More specifically, a thin film having a thickness of 0.01 to 1 μm is sputter-deposited on one surface of a sheet-shaped transparent substrate by a sputtering method using copper or an alloy thereof as a target.
[0050]
At the time of this sputtering, it is not necessary to perform any pretreatment on the sheet, and it can be performed immediately. Good. The sputtering may be performed under general conditions, but low-gas-pressure sputtering performed under a low gas pressure (the gas is an inert gas such as argon) is preferable. This low gas pressure sputtering corresponds to tripolar glow discharge, bipolar glow RF discharge, magnetron, sputtering by ion beam. Is more preferable because the temperature generated in the vacuum chamber is low.
[0051]
Next, the step (b) will be described.
[0052]
The metal layer obtained in the step (a) is developed using a photolithography method to expose a desired pattern. Here, the photolithography method generally means application of a photosensitive resist → vacuum adhesion of a masking film → exposure → development for dissolving and removing an exposed portion or a non-exposed portion → exposure of a desired pattern. The photosensitive resist is classified into a negative type and a positive type. In the case of the negative type, when exposed to ultraviolet light, only that portion is photo-cured. The positive type has the opposite light characteristics to the negative type, and the portion that has received ultraviolet light is photolyzed. If both development processes are performed, the unexposed portion is dissolved and removed in the negative type, and the exposed portion is dissolved and removed in the positive type. Therefore, the masking film uses a positive mask (pattern is black) for the positive type and a negative mask (pattern is transparent) for the negative type.
[0053]
The type of the photosensitive resist is not particularly limited, but an acrylic type is generally used for a negative type, and a diazo type is used for a body type. Since the resist is generally in a liquid state, the resist is applied. However, the resist may be in the form of a film in advance, such as a dry film.
[0054]
Next, the step (c) will be described. The chemical etching in (c) is an operation of chemically dissolving and removing the metal constituting the metal layer with an etchant. Therefore, the etchant is not limited as long as the metal can be dissolved. Generally, it is an aqueous solution of ferric chloride or cupric chloride which is usually used. However, it is preferable to use a sulfuric acid / hydrogen peroxide based aqueous solution which can be etched milder than these.
[0055]
In the present invention, since the thickness of the metal layer is small, the chemical etching time can be as short as about 30 to 60 seconds.
[0056]
Finally, the step (d) will be described. The photosensitive resist layer in the remaining conductive pattern portion is peeled off. The peeling removal is generally performed by spraying or rocking immersion using a stripping chemical solution of various organic solvents or alkaline aqueous solutions.
[0057]
Immediately after finishing, wash and dry to complete the whole process.
[0058]
FIG. 3 shows the structure of the product obtained by the treatment in each of the above steps according to (a) to (2). In FIG. 3, a part of the structure is shown in a sectional view. In FIG. 3, 1 indicates a transparent substrate, 2 indicates a metal layer, and 3 indicates a photosensitive photoresist.
[0059]
【Example】
Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples.
[0060]
Example 1
A biaxially stretched polyethylene terephthalate film (hereinafter referred to as a PET film) having a thickness of 125 μm, a size of 400 × 1000 mm, and Tt = 90% is placed in a vacuum chamber of a magnetron type sputtering apparatus so as to face a copper target, and air is blown. Vacuum degree 2 × 10 obtained by completely replacing with argon^-3In a toll environment, sputter deposition was repeated three times at an applied voltage of 9 kW and at 1 m / min.
[0061]
The thickness of the copper thin film obtained above was uniform at about 0.1 μm. A part was cut off and a tape peeling test was performed, but there was no appearance that the copper thin film was peeled off.
[0062]
Next, a positive resist was coated on the sputtered surface of the obtained copper sputtered PET film by a roll coater to provide the resist layer having a thickness of 5 μm. Then, a positive mask depicting a pattern having a line width of 5 μm, a pitch width of 100 μm, a pitch width to the line width of 20, and an aperture ratio of 90% was vacuum-sucked onto the resist layer surface, and then exposed.
[0063]
As the positive mask, a masking film in which the pattern portions were black, the non-pattern portions were transparent, and the openings were drawn in a square shape was used. Exposure was performed using an ultra-high pressure mercury lamp as a light source at 130 mJ / cm.²Irradiation was performed. As a result of this exposure, the resist in the non-pattern portion was decomposed, and this portion was dissolved and removed with a developing solution, and finally, washed and dried. The resist in the pattern portion remained in close contact with the copper sputtering surface. Therefore, the pattern portion is masked, and the non-pattern portion has the copper sputter layer exposed.
[0064]
This was entirely etched under the following conditions. An aqueous solution containing sulfuric acid and hydrogen peroxide was used as a chemical etching solution, and the solution was put into a bath and etched while stirring. The etching time was 30 seconds, and immediately after 30 seconds, the substrate was washed with water and dried.
[0065]
Next, the entire surface was sprayed with acetone and brushed with a light touch to dissolve and remove the remaining resist in the pattern portion, washed with water and dried to obtain a transparent sheet having a conductive pattern formed on a PET film.
[0066]
Comparative Example 1
A biaxially stretched polyethylene terephthalate film (hereinafter referred to as a PET film) having a thickness of 125 μm, a size of 400 × 1000 mm, and Tt = 90% is placed in a vacuum chamber of a magnetron type sputtering apparatus so as to face a copper target, and air is blown. Vacuum degree 2 × 10 obtained by completely replacing with argon^-3In a toll environment, sputtering was repeated three times at an applied voltage of 9 kW at 1 m / min.
[0067]
The thickness of the copper thin film obtained above was uniform at about 0.1 μm. A part was cut off and a tape peeling test was performed, but there was no appearance that the copper thin film was peeled off.
[0068]
Next, a positive resist was coated on the sputtered surface of the obtained copper sputtered PET film by a roll coater to provide the resist layer having a thickness of 5 μm. Then, a negative mask depicting a pattern having a line width of 15 μm, a pitch width of 322 μm, a pitch width relative to the line width of 21.5 and an aperture ratio of 90% was vacuum-sucked on the resist layer surface, and then exposed.
[0069]
As the negative mask, a masking film in which the pattern portions were transparent, the non-pattern portions were black, and the openings were drawn in a square shape was used. Exposure was performed using an ultra-high pressure mercury lamp as a light source at 130 mJ / cm.²Irradiation was performed. As a result of this exposure, the resist in the pattern portion was decomposed, and this portion was dissolved and removed with a developing solution. Finally, the resist was washed with water and dried. The resist in the non-pattern portion remained in close contact with the copper sputtering surface. Therefore, the non-patterned portion is masked, and the patterned portion has the copper sputtered layer exposed.
[0070]
Next, copper was electrolytically plated on the exposed pattern under the following conditions. That is, a phosphorous-containing copper as an anode, the pattern as a cathode, a mixed solution of copper sulfate, sulfuric acid and water as a plating solution, a bath temperature of 23 ° C., and a cathode current density of 1.7 A / dm.²Electroplating was performed at a plating speed of 0.3 μm / min. Then, it was thoroughly washed with water and dried.
[0071]
Next, the surface of the electroplated product was brushed with a light touch while spraying acetone over the entire surface to dissolve and remove the remaining resist in the non-pattern portion, washed with water, and dried. The obtained part was cut out, and the cross section was enlarged and observed with a microscope. As a result, the laminated copper plating layer had a very sharp prismatic shape.
[0072]
Next, this was entirely etched under the following conditions.
[0073]
An aqueous solution containing sulfuric acid and hydrogen peroxide was used as a chemical etching solution, and the solution was put into a bath and etched while stirring. The etching time was 30 seconds. After 30 seconds, the film was immediately washed with water and dried to obtain a transparent sheet having a conductive pattern formed on a PET film. The final thickness of the metal (copper) layer was 2.7 μm.
[0074]
Test example 1
With respect to the sheet obtained in Example 1 and the sheet obtained in Comparative Example 1, electromagnetic wave shielding characteristics, sheet resistance, and total light transmittance were examined. The electromagnetic wave shielding characteristic is expressed by an attenuation rate (dB-dB) of an electromagnetic wave measured in a frequency range of 0 to 1000 MHz (megahertz) by a measuring device in the Kansai Electronics Industry Promotion Center method (generally called the KEC method). did. The sheet resistance value was measured with a sheet resistance measuring device (Loresta-EP (MCP-T360) manufactured by Mitsubishi Chemical Corporation, probe used: ESP). The total light transmittance was measured by a turbidimeter type NDH-20D manufactured by Nippon Denshoku Industries Co., Ltd., which was manufactured based on JIS K7105 (1981).
[0075]
Regarding the test results of the electromagnetic wave shielding characteristics, FIG. 4 shows the result of Example 1 and FIG. 5 shows the result of Comparative Example 1. Table 1 shows the results of examining the characteristics of each sheet including the sheet resistance value and the total light transmittance.
[0076]
[Table 1]

[0077]
As is clear from the results shown in FIGS. 4 and 5 and Table 1, it was found that the sheet of the present invention had good shielding characteristics despite having a high sheet resistance value. In particular, it has been clarified that electromagnetic waves in a frequency band (30 to 300 MHz), which is regarded as a problem due to PDP radiation noise, are significantly shielded.
[0078]
Example 2
When the electromagnetic wave shielding transparent sheet prepared in Example 1 was placed on the front surface of the PDP, no moiré occurred. Further, moiré did not occur even if the face-to-face angle with the PDP was shifted by 45 degrees. From this, it became clear that the moiré phenomenon was reduced or eliminated by the present invention.
[0079]
【The invention's effect】
The present invention has an excellent effect of enabling fine wire processing and having good transparency and shielding characteristics by having the above-described configuration. In particular, the present invention has an advantageous effect that electromagnetic waves in a low frequency region are remarkably shielded (shielded), which is unpredictable from the prior art.
[0080]
In addition, the present invention also has an effect that the moire phenomenon is reduced or eliminated by enabling fine fine wire processing. This eliminates the need for the conventional angle adjustment for eliminating moiré, and also eliminates the need for the bias angle adjustment for each type of PDP or the like.
[0081]
Further, there is an advantage that the electromagnetic wave shielding transparent sheet can be easily and easily obtained without requiring complicated steps such as plating when producing the sheet of the present invention. In addition, since the thickness is reduced, there is also an advantage that the problem of air bubble entrapment at the time of bonding with the adhesive film is reduced.
[0082]
Since the transparent sheet of the present invention has such excellent physical properties, it is useful for shielding electromagnetic waves from electromagnetic wave generating devices such as PDPs.
[Brief description of the drawings]
FIG. 1 is a plan view showing a configuration when a pattern is a square lattice pattern.
FIG. 2 is a diagram illustrating a model circuit for calculating a sheet resistance value.
FIG. 3 is a cross-sectional view showing the structure of the sheet of the present invention obtained by processing in each of the steps (a) to (d).
FIG. 4 is a drawing showing electromagnetic wave shielding characteristics of an example of the present invention.
FIG. 5 is a drawing showing electromagnetic wave shielding characteristics of a comparative example.

Claims (9)

An electromagnetic wave shielding transparent sheet having a conductive pattern formed of a metal layer on a transparent substrate, wherein the thickness of the metal layer is 0.01 to 1 μm. 2. The electromagnetic wave shielding transparent sheet according to claim 1, wherein the line width (a) of the conductive pattern is 1 to 10 [mu] m. The electromagnetic wave shielding transparent sheet according to claim 1, wherein a pitch width (b) of the conductive pattern is 5 to 200 μm. The electromagnetic wave shielding transparent sheet according to any one of claims 1 to 3, wherein a ratio (b / a) of a pitch width to a line width of the conductive pattern is 5 to 40. The electromagnetic wave shielding transparent sheet according to any one of claims 1 to 4, wherein the conductive pattern has an aperture ratio of 64 to 95%. The electromagnetic wave shielding transparent sheet according to any one of claims 1 to 5, wherein the sheet resistance value is 0.08 to 50Ω / □. The electromagnetic wave shielding transparent sheet according to any one of claims 1 to 6, which is obtained by sequentially performing the following steps (a) to (d).
(A) forming a metal layer on one surface of a transparent substrate by a thin film forming means;
(B) developing the metal layer by photolithography to expose a non-conductive pattern portion;
(C) a step of chemically etching the non-conductive pattern portion to dissolve and remove the metal layer;
(D) removing and removing the resist remaining on the conductive pattern; A method for producing an electromagnetic wave shielding transparent sheet, wherein the following steps (a) to (d) are sequentially performed.
(A) forming a metal layer having a thickness of 0.01 to 1 μm on one surface of the transparent substrate by a thin film forming means;
(B) developing the metal layer by photolithography to expose a non-conductive pattern portion;
(C) a step of chemically etching the non-conductive pattern portion to dissolve and remove the metal layer;
(D) removing and removing the resist remaining on the conductive pattern; A composite sheet comprising (i) a shield layer comprising the electromagnetic wave shielding transparent sheet according to claim 1, (ii) an antireflection layer, and (iii) a near-infrared cut layer.

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