JP2000114770A - Electromagnetic wave shielding transparent body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electromagnetic wave shielding transparent film appropriate for a window of a display body at low cost, by generating a pattern form where curves according to sinusoidal function or tangential function are arrayed vertically and horizontally for raised electromagnetic wave shielding effect. SOLUTION: At formation of a conductive layer at least on one surface of a transparent polymer film, a pattern form where the curves according to the sinusoidal function or tangential function represented by equation (y=A.Sin(αx+ϕ) y=B.Tan(βx+ψ), where A, B, α, β, ϕ, ψ are arbitrary constants) are arrayed vertically and horizontally is generated to provide an electromagnetic wave shielding body. The electromagnetic shielding body is excellent in transparency.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a window on which a display surface of a display device, in particular, a plasma display (hereinafter abbreviated as PDP) which requires prevention of electromagnetic wave leakage and a medical device which needs to see through the inside are installed. And other surface cover materials.

[0002]

2. Description of the Related Art In recent years, with the rapid development of electronics, electromagnetic interference that causes malfunctions of electronic devices has become a serious problem with the development of computers and the like. As means for preventing the electromagnetic wave interference beforehand, there is an active shield that seals unnecessary radio waves at the source by making the housing of the electronic device conductive. As specific materials for preventing electromagnetic wave leakage, metal foils, punched metal foils, metal meshes, metal fibers, and organic / inorganic fiber plated materials are used. However, transparent materials are used for display bodies and windows represented by PDPs. Properties are absolutely necessary conditions, and none of them were suitable for use from the viewpoint of light transmission.

Further, since the metal surface is oxidized with the passage of time, high-frequency contact is easily cut off at lattice points even in a metal mesh which can be expected to have a certain degree of transparency, and the electromagnetic shielding effect is stable for a long time. There was a disadvantage that it was difficult to show. On the other hand, it has been considered that a composite oxide of indium oxide and tin oxide (hereinafter abbreviated as ITO), which is widely used as an electrode for liquid crystal and has no oxidative deterioration, is considered to be used, but it is pointed out that there is little electromagnetic wave leakage prevention function. In fact, it has been limited to antistatic function applications. Attempts have been made to increase the conductivity to the same level as that of metal, for example, 1 Ω / □ or less, but at present, even if the film is formed while heating on a glass substrate, the level is 4 Ω / □, and the film is formed on a plastic film. That was technically impossible.

Further, there is a problem of weight. In particular, if a large-sized and heavy glass substrate having a diagonal of 40 to 50 inches or more is used, which is attracting attention in the future, there is a problem from the viewpoint of mountability when mounting the PDP.
On the other hand, if a plastic substrate is used as a substrate for weight reduction, the most important means of heating the substrate to increase transparency and conductivity cannot be used from the viewpoint of heat resistance, and it is impossible to obtain a low resistance. Was. If the resistance is lowered by further increasing the film thickness, the film may be peeled off from internal stress after film formation due to the difference in the coefficient of linear expansion between the ITO film and the plastic substrate, or cracks may be formed to form ITO having a resistance as low as metal. Is 20-40Ω
However, it was the limit, and it was impossible to achieve the purpose.

[0005]

SUMMARY OF THE INVENTION The present invention provides an inexpensive transparent electromagnetic wave shielding film having transparency and a high electromagnetic wave shielding effect, which is most suitable for a display, particularly for a plasma display or a window of a medical equipment room. To provide

[0006]

The present invention provides a method for forming a conductive layer on at least one surface of a transparent polymer film.
It is a transparent electromagnetic wave shielding body in which a pattern according to a Sin function (1) or a Tan function (2) shown in the following equation is arranged vertically and horizontally. y = A · Sin (αx + φ) (1) y = B · Tan (βx + ψ) (2) A, B, α, β, φ, ψ: Arbitrary constants In the present invention, at least one surface of the transparent polymer film is conductive. In forming a layer, the electromagnetic wave shielding transparent body has a pattern shape in which curves according to an exponential function (3) and a logarithmic function (4) shown in the following equation are arranged vertically and horizontally. y = C · exp (γx + ρ) (3) y = D · ln (δx + ξ) (4) C, D, γ, δ, ρ, ξ: Arbitrary constants In the present invention, at least one surface of the transparent polymer film is conductive. In forming a layer, the electromagnetic wave shielding transparent body has a pattern shape in which curves according to an inverse proportional function (5) shown in the following equation are arranged vertically and horizontally. y = E / x (5) E: Arbitrary constant The present invention is a transparent electromagnetic wave shielding body in which a pattern shape is created by combining and arranging the curves of the above equations (1) to (5). In a preferred embodiment, the transparent polymer reinforcement having a light transmittance at a wavelength of 550 nm of 50% or more and a thickness of 1 mm or more is laminated via an adhesive layer, and at least one of a laminated film and a transparent polymer reinforcement is used. And an anti-reflection layer and / or a hard coat layer and / or a near infrared cut layer.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION A polymer film serving as a base material for forming a conductive layer most important to the present invention is made of polyester such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate, polyimide, polycarbonate, polyacrylonitrile, and the like. Thermoplastic resin represented by polyethersulfone, polysulfone, polyetherimide, polyarylate, norbornene,
It is made of a UV-curable resin, a thermosetting resin represented by an epoxy resin or the like, and has a light transmittance at 550 nm of 80%.
(Hereinafter, values at 550 nm are all shown.) A film having higher transparency or a copolymer of these polymers can be used and is appropriately selected.

Although it is desirable that the total light transmittance is as high as possible, the final product needs to be 50% or more. Therefore, even if at least two sheets are laminated, if the substrate has 80%, it is suitable for the purpose. Yes, since the higher the transmittance, the more layers can be laminated, the thickness is preferably 85% or more, most preferably 90% or more. Therefore, reducing the thickness is also an effective means. The thickness of the polymer film is not particularly limited as long as transparency is satisfied, but is preferably 25 to 300 μm from the viewpoint of processability. If the thickness is less than 25 μm, the film is too flexible, and it is not suitable because the film tends to be stretched or wrinkled due to the tension during the lamination process of the conductive layer. Also, 30
If it exceeds 0 μm, the flexibility of the film decreases, and continuous winding in each step is difficult and not suitable. In particular, when a plurality of sheets are laminated, the workability is significantly inferior, and the workability and the overall thickness are particularly preferably 25 to 100 μm in consideration of the overall thickness.

When laminating the conductive layers, a known adhesive layer is provided for the purpose of improving the adhesion. This problem is particularly important when the conductive layer is patterned into fine wires. For example, when patterning is performed on an etching line, the adhesion between the base material and the conductive layer should be at least 0.3 k in order to withstand shower water pressure.
g / cm is required, and an adhesion force of 1.0 kg / cm or more is required as a level having no practical problem. If these adhesions are not obtained, the conductive layer may be peeled off after patterning, or may be disconnected during etching. Since a higher light transmittance is desired, the thickness of the adhesive layer, the refractive index of a substance used for the adhesive layer, and the like are also important characteristics. The type of adhesive can be selected as appropriate according to the base material used, but as a resin used for the adhesive layer, a synthetic resin-based resin, urea resin-based, melamine resin-based, phenolic resin-based, epoxy resin-based, There are vinyl acetate resin type, cyanoacrylate type, polyurethane type, α-olefin-maleic anhydride resin type, aqueous polymer-isocyanate type, acrylic resin type, UV curable resin type,
Other examples include an emulsion adhesive, a hot melt adhesive, a synthetic rubber adhesive, a silicone adhesive, and an inorganic adhesive.

The conductive layer formed on the above-mentioned film may be A
Metals such as u, Ag, Al, Pt, and Cu, or alloys, oxides, nitrides, ITO, and conductive polymers containing these as main components can be used, and if these can be patterned, There is no particular limitation. If necessary, these may be laminated. Here, in the case of metal, the film thickness is preferably 50 ° to 50 μm. 50Å
If it is less than 50 μm, the shielding effect is remarkably poor, and if it exceeds 50 μm, the pattern workability is reduced and the transmittance is reduced. Further, as an effect of laminating the conductive layers, for example, when the upper and lower portions of the metal layer are protected by ITO or the like, there is an advantage that oxidation deterioration can be largely improved. As a film forming method, for metals and the like, a vapor deposition method, an electroplating method, a method of laminating by laminating a metal foil, and a method of using these in combination are possible. Selected. In addition, as a method of forming an oxide or nitride containing ITO, a vapor deposition method and a sputtering method are generally used, but a sol-gel method is also possible. As a method for forming the patterning, a photolithography method, a printing method, or the like can be applied.

In forming a pattern on a conductive layer, its shape is very important. For example, when a lattice-shaped pixel is formed on a target on which a transparent electromagnetic wave shielding body is installed, such as a PDP screen, when both the pixel of the PDP and the lattice-shaped pattern of the transparent electromagnetic wave shielding body are overlapped, moire occurs. The visibility of the screen is significantly reduced. Therefore, in the present invention, as a method for solving this moiré phenomenon, in forming a conductive layer on at least one surface of a transparent polymer film, a pattern shape in which curves according to Sin, Tan, exponent, logarithm, and inverse proportional function are arranged vertically and horizontally is used. They found that it was good to create them. The moiré phenomenon is caused by combining a periodic intensity distribution of light intensity generated by a partition wall forming a PDP pixel and a similar intensity distribution generated by a conductive layer pattern. Therefore, if the pattern of the pixel constituting the PDP is similar to that of the pattern, moiré fringes are likely to occur. When Sin, Tan, exponent, logarithm and inverse proportional function according to the present invention are applied to pattern design, PD
Although the light intensity distribution is generated due to the superposition of the partition walls and the pattern of P, the light intensity distribution can be made minute and uniform so that it cannot be visually recognized, so that the aperture ratio having sufficient transparency and the electromagnetic wave shielding characteristics are maintained. While doing
It is possible to suppress the occurrence of the moire phenomenon. Here, the moire fringes are generated depending on the shape of the PDP pixel and the electromagnetic wave shield pattern when they are superimposed.
Determined in consideration of the pitch and line width of the P pixels. Also,
The pitch and line width for arranging these functions are arbitrarily determined within a range in which the required electromagnetic wave shielding characteristics and aperture ratio are compatible.

The frequency of the electromagnetic wave to be regulated is 10K
Since the range of Hz to 1000 MHz is generally used, the conductivity of the conductive layer requires a specific resistance of 10 ³ Ω · cm or less. Generally, the electromagnetic wave shielding effect is expressed by the following equation. S (dB) = 10log (1 / ρf) + 1.7t√f / ρ S (dB): Electromagnetic wave shielding effect ρ (Ω · cm): Volume resistivity of conductive film f (MHz): Electromagnetic wave frequency Naturally, shielding effect In order to increase S, it is necessary to reduce the specific resistance ρ as much as possible. The lower the specific resistance ρ, the more effectively electromagnetic waves having a wider range of frequencies can be effectively shielded. In order to obtain a desired shielding effect, it is possible to appropriately design the pattern shape, the material of the conductive layer, and the film thickness of the conductive layer.

By forming the electromagnetic wave cut filter in this way, the shielding effect represented by the following equation can be greatly improved. S (dB) = 20 X log10 (E0 / E1) E0 is an incident electromagnetic wave E1 is a transmitted electromagnetic wave The allowable return loss, which is a conventional radio wave absorber, is a power absorption rate of 9
One guideline is 20 dB or more corresponding to 9% or more, but the present invention has enabled 30 to 50 dB.

The transparent polymer reinforcing plate is used to withstand an external pressure, and a hard coat is indispensable to prevent damage due to scratches and the like, and to prevent a decrease in transparency. The hard coat layer is made of a UV curable resin such as epoxy acrylate or urethane acrylate, or a thermosetting resin such as an epoxy resin, or an inorganic material, specifically, a transparent oxide such as silicon oxide, alumina, titanium oxide, or zirconium oxide. preferable. Further, the original reinforcing plate needs to have a strength of 1 mm or more due to the use of a polymer in order to reduce the weight. The strength increases as the thickness increases, but it is disadvantageous in terms of weight and transparency. If the strength can withstand artificial external pressure and finger pressure, the object can be achieved with 1 mm or more, and practically 5 mm
Up to.

Further, it is desirable that the transparent polymer reinforcing plate has an antireflection function. This is installed in order to prevent diffuse reflection from the PDP on the display unit and increase contrast. Of course, the hard coat layer may have an anti-reflection function, and may be separately laminated.

[0016]

EXAMPLES Example 1 A urethane-based adhesive layer 1 was applied to a 75 μm-thick polyethylene terephthalate film (hereinafter abbreviated as PET), and then a copper foil (12 μm thick) was laminated to form a PET film with a copper foil. I got This conductive layer was patterned by a photolithography method to form a pattern in which curves represented by the Sin function and the Tan function shown in FIG. 1 were arranged vertically and horizontally. At this time, the line width was 10 μm, and the space width was 160 μm. The light transmittance at 550 nm after pattern processing is 74%, and the light transmittance in the near infrared region is <10% (900 to 1200).
nm), and the electric field shielding characteristics were as good as 50 dB or more (Advantest method) in the range of 200 to 1000 MHz. Subsequently, a hard coat having a pencil hardness of 3H or more having an anti-reflection function is applied to one surface of a 2 mm thick polycarbonate substrate, and aliphatic polyester urethane (A manufactured by Toyo Morton Co., Ltd.)
DN-401) The patterned base material was laminated on the back surface of the hard coat layer with the adhesive layer 2. At the outer edge, each transparent conductive film and the flat cable were bonded with silver paste (CRM-1085 manufactured by Sumitomo Bakelite) and electrically grounded. PDP with excellent pencil hardness of 3H and excellent in abrasion resistance, excellent not only in shielding property but also in durability, no moiré fringe when superimposed on PDP screen, excellent in visibility
An electromagnetic wave shielding transparent plate for use was obtained.

<< Embodiments 2 to 4 >> The patterns in Embodiment 1 are shown in FIG. 2 by the Sin function (Embodiment 2), the exponential function and the logarithmic function shown in FIG. 3 (Embodiment 3), and FIG. When an electromagnetic wave shielding transparent plate was formed in the same manner as in Example 1 by using the curve described by the inverse proportional function (Example 4), moire fringes did not occur when superimposed on the PDP screen. there were.

<< Comparative Example 1 >> In Example 1, Sin, T
When a pattern was formed by a straight line instead of using the curve described by the an function, moiré fringes occurred when the pattern was superimposed on a PDP screen, and it could not be put to practical use.

[0019]

According to the present invention, it is possible to provide a transparent electromagnetic wave shielding plate having excellent transparency.

[Brief description of the drawings]

FIG. 1 is an example of a pattern drawing according to a first embodiment.

FIG. 2 is an example of a pattern drawing according to a second embodiment.

FIG. 3 is an example of a pattern drawing according to a third embodiment.

FIG. 4 is an example of a pattern drawing according to a fourth embodiment.

Claims (9)

[Claims] In forming a conductive layer on at least one surface of a transparent polymer film, a pattern is formed by vertically and horizontally arranging a curve according to a Sin function (1) or a Tan function (2) shown in the following equation. An electromagnetic wave shielding transparent body characterized by the following. y = A · Sin (αx + φ) (1) y = B · Tan (βx + ψ) (2) A, B, α, β, φ, ψ: arbitrary constant 2. In forming a conductive layer on at least one surface of a transparent polymer film, a pattern is formed by arranging a curve according to an exponential function (3) and a logarithmic function (4) shown below and vertically and horizontally. An electromagnetic wave shielding transparent body characterized by the following. y = C · exp (γx + ρ) (3) y = D · ln (δx + ξ) (4) C, D, γ, δ, ρ, ξ: arbitrary constant 3. A method for forming a conductive layer on at least one surface of a transparent polymer film, comprising forming a pattern shape in which curves according to an inverse proportional function (5) shown in the following formula are arranged vertically and horizontally. Transparent body. y = E / x (5) E: arbitrary constant 4. A transparent electromagnetic wave shielding body, wherein a pattern is formed by combining and arranging the curves according to claim 1. 5. The light transmittance at a wavelength of 550 nm is 50%.
The transparent electromagnetic wave shielding body according to claim 1, which is the above. 6. An electromagnetic wave shielding transparent body comprising the transparent electromagnetic wave shielding body according to claim 1 laminated on a transparent polymer reinforcement having a thickness of 1 mm or more via an adhesive layer. 7. The electromagnetic wave shielding transparent body according to claim 6, wherein an antireflection layer is provided on at least one of the laminated film and the transparent polymer reinforcing body. 8. The electromagnetic wave shielding transparent body according to claim 6, wherein a hard coat layer is provided on at least one of the laminated film and the transparent polymer reinforcing body. 9. The electromagnetic wave shielding transparent body according to claim 6, wherein a near-infrared cut layer is provided on at least one of the laminated film and the transparent polymer reinforcement.