JP2000059075A - Electromagnetic wave shielding transparent substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain transparency and increase in electromagnetic wave shielding effect by depositing an adhesive layer, a transparent conductive film and a metal thin-film layer in this order, as necessary on at least one face of a transparent high molecular film and then removing only the metal thin film layer by selective etching to form a filter pattern. SOLUTION: A high molecular film in a transparent high molecular film as a base is made of thermoplastic resin, ultraviolet curing resin, thermosetting resin or the like. And, it has a transparency of 80% (50% as a final product) or higher than light transmissivity at 550 nm wavelength. When fabricating a substrate by depositing copper as a metal layer on a transparent high molecular film, a transparent metal oxide is formed as an adhesive layer to obtain both transparency and adhesion. In patterning copper, if it is a transparent conducive film of a high crystallinity, only a copper layer is selectively etched using a selective etchant such as a secondary iron nitrate. Thereby, superior durability as well as high shielding property can be obtained.

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 waves which cause malfunctions of electronic devices with the development of computers and the like have become a serious problem. 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. Are all necessary conditions, and all of them are unsuitable 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 a film is formed on a glass substrate while heating, the level is 4 Ω / □, which is technically impossible. There was.

[0004] In addition, there is the 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 ~
It was 40Ω, and it was impossible to achieve the purpose.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has a high transparency and a high electromagnetic wave shielding effect. It is used for a display, particularly for a plasma display or a window of a medical equipment room. It is to provide an optimal electromagnetic wave shielding transparent film at a low cost.

[0006]

According to the present invention, an adhesive layer, a transparent conductive film, and a metal thin film layer are sequentially laminated on at least one side of a transparent polymer film, if necessary, and only the metal thin film layer is selectively formed. It is an electromagnetic wave shielding transparent body formed by etching to form a filter pattern. A preferred embodiment is a transparent electromagnetic shielding material in which the metal thin film layer is made of copper and the light transmittance at a wavelength of 550 nm is 50% or more. In a more preferred embodiment, a transparent polymer reinforcement having a thickness of 1 mm or more is laminated via an adhesive layer, and at least one of the laminated film and the transparent polymer reinforcement is provided with an antireflection layer and / or a hard coat layer. Is an electromagnetic wave shielding transparent body.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The polymer film in the transparent conductive film which is the most important substrate in the present invention includes polyester such as polyethylene terephthalate, polybutylene terephthalate and polyethylene naphthalate, polyimide, polycarbonate, polyacrylonitrile, and the like. It is made of a thermoplastic resin represented by polyethersulfone, polysulfone, polyetherimide, polyarylate, norbornene, a thermosetting resin represented by an ultraviolet curable resin, an epoxy resin or the like, and has a light transmittance at 550 nm of 80. % (Hereinafter, all values at 550 nm) 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. When the thickness is less than 25 μm, the film is too flexible, and the tension or the like at the time of film formation or processing of the oxide which is the transparent conductive layer is apt to be stretched or wrinkled, so that the transparent conductive layer is easily cracked or peeled off, which is not suitable. . On the other hand, if it exceeds 300 μm, the flexibility of the film decreases, and continuous winding in each step is difficult and not suitable. Especially when laminating a plurality of sheets, workability is greatly inferior,
In addition, in consideration of the entire thickness, 25 to 100 μm is particularly preferable.

When a substrate is prepared by laminating copper as a metal layer on a transparent polymer film, there is a problem that sufficient adhesion cannot be obtained. This is considered to be because the physical constants such as the coefficient of linear expansion and the elastic modulus between the base material, the adhesive layer and the copper layer are largely different. Another major factor is that it is difficult to design an adhesive that achieves both transparency and adhesion. This problem is particularly remarkable when copper is laminated by a method such as vapor deposition or sputtering, and it is difficult to obtain sufficient adhesion. If the adhesion between the copper and the base material is not sufficient, it is difficult to increase the productivity, and there is a problem that the cost of the product is increased. Then, in order to solve the above-mentioned problem, it has been found that by providing a transparent metal oxide as an adhesive layer, it is possible to obtain a highly reliable electromagnetic wave shielding transparent body having both transparency and 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.

Here, as an example of the transparent metal oxide film, I
conductive complex oxides such as n ₂ O ₃ , In ₂ O ₃ and SnO ₂ (ITO), In ₂ O ₃ and ZnO, In ₂ O ₃ and Ga ₂ O ₃ ;
Examples include SiOx, TiOx, and composite oxides thereof. As a method of forming a transparent oxide film, sputtering, evaporation,
There are a vacuum deposition method such as ion plating, a coating method using a sol-gel method, and the like, which may be selected in consideration of the type, thickness, and productivity of the film to be formed. In the vacuum deposition method, it is possible to form a conductive film having a low resistance value, so that an improvement in the shielding effect can be expected. In the case of using the coating method, an anchor effect of the copper layer due to fine irregularities on the surface layer can be expected. Therefore, it is advantageous for improving the adhesion. Before forming the transparent metal oxide film, it is also possible to perform a pretreatment such as an undercoat treatment, a primer treatment, and a corona treatment, which are usually used for obtaining adhesion to the substrate.

Subsequently, a copper layer is formed on the transparent metal oxide film. When a copper layer is laminated on the transparent metal oxide film, migration occurs between the copper layer and the transparent oxide film layer. This creates an intermediate layer of cuprous oxide between the two layers,
Since this intermediate layer has a gradient structure in which the composition of both components changes little by little in the thickness direction, the adhesiveness is improved more than when only an intermediate layer of cuprous oxide is provided. In addition, the oxidation proceeds from cuprous oxide to copper oxide, and as the thickness of the copper oxide layer increases, the adhesion decreases. The thickness is most suitable for maximizing the adhesion. In addition to the improved adhesion, other important properties can be improved at the same time. (1) For example, the surface of copper is usually coated with N for the purpose of preventing oxidation.
Although i-plating treatment and rust-prevention coating treatment are applied, the provision of a transparent oxide film layer with high gas barrier property prevents gas such as water vapor and oxygen from entering the substrate from entering, and the temporal adhesion due to oxidation Deterioration can be prevented. This is especially important for long term reliability. (2) In the case where a conductor is applied as the transparent metal oxide, conductivity is imparted also to the mesh openings formed of copper by lamination, so that an effect of improving the electromagnetic wave shielding effect is also imparted. If the electromagnetic wave shielding layer formed of mesh and the ITO film are designed so that the frequency dependence of the shielding characteristics is different, the frequency of the electromagnetic waves that can be shielded can be widened, so the characteristics as an electromagnetic wave shielding body are greatly improved. It is possible to do. (3) The ITO film has a property of blocking light rays in the near-infrared region, and has an effect of imparting a near-infrared cut function to the electromagnetic wave shielding transparent body. (4) An antireflection function can be provided by the difference in the refractive index between the ITO film and the coating layer to be laminated.

Here, the thickness of the copper layer is preferably 50 ° to 50 μm. If it is less than 50 °, the shielding effect is remarkably poor, and
If it exceeds m, the pattern workability will decrease and the transmittance will decrease. The method of forming the copper layer here is as follows.
In addition to the sputtering method and the vapor deposition method, electroplating is also possible, and is selected from the viewpoints of economy, pattern workability, shielding characteristics, and the like. For the purpose of preventing oxidation deterioration on the copper surface,
A plating treatment with gold, nickel, or the like, or a rust-preventive coating treatment may be performed as necessary.

In the patterning of copper, it is necessary to selectively etch only the copper layer. This is important for satisfying the adhesion of the copper layer, the optical characteristics and the shielding characteristics of the transparent electromagnetic wave shield. The pattern processing conditions can be set according to the type of the transparent metal oxide film. For example, S
In the case of iOx, TiOx, or a composite oxide thereof, cupric chloride or ferric chloride, which is usually used as an etching solution for copper, may be used. By using a selective etching solution such as ferric nitrate, it is possible to selectively etch only the copper layer.

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 thickness of the conductive layer.

By forming the electromagnetic wave cut filter in this manner, 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 external pressure. However, a hard coat is indispensable because it is damaged by scratches and the like, and furthermore, reduces transparency. The hard coat layer is preferably made of an inorganic material, specifically a transparent oxide such as silicon oxide, alumina, titanium oxide or zirconium oxide, in addition to a resin such as epoxy acrylate or urethane acrylate. 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 the weight,
Since it is disadvantageous from the viewpoint of transparency, if the strength is sufficient to withstand artificial external pressure and acupressure, the object can be achieved with 1 mm or more and practically up to 5 mm.

The PDP emits light using xenon gas discharge. The near-infrared ray generated at this time leaks to the outside and leads to malfunction of widely used sensors, so that the near-infrared ray cut function is indispensable for the front shield plate of the PDP. In order to provide a near-infrared cut function, a method of providing a near-infrared cut function to the transparent polymer reinforcement and a method of newly providing a coating layer are used. Examples of the near-infrared absorbing agent include anthraquinone-based, aminium-based, polymethine-based, diimonium-based, and cyanine-based dyes, metal complexes such as palladium, nickel, platinum, molybdenum, and tungsten, and organic salts.

Furthermore, it is desirable that the surface opposite to the hard coat layer 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, there is no limitation on the formation surface as long as the function can be imparted to the hard coat layer.

[0019]

EXAMPLES Example 1 An epoxy acrylate prepolymer (VR-6, manufactured by Showa Polymer Co., Ltd.) having a molecular weight of 1540 and a melting point of 70 ° C. was used as an undercoat on a 75 μm-thick polyethylene terephthalate film (hereinafter abbreviated as PET).
0) 100 parts by weight, 400 parts by weight of butyl acetate, 100 parts by weight of cellosolve acetate, and 2 parts by weight of benzoin ethyl ether were used to coat to a thickness of 1 μm. Further, indium oxide was formed by a sputtering method so as to form a crystalline film having a transmittance of 80% and a sheet resistance of 150Ω. A copper thin film was formed to a thickness of 2000 ° by sputtering and then electroplated to obtain a copper thickness of 4 μm and a surface resistance of 4 × 10 ⁻³ Ω /.
The PET film with copper foil of □ was obtained. This conductive layer is patterned by a photolithography method using ferric nitrate as an etchant to obtain a line width of 10 μm and a space width of 160 μm.
A μm mesh filter pattern was obtained. When the copper foil surfaces of the obtained films were bonded to each other with a thermosetting epoxy-based adhesive and subjected to a 90-degree peel test, 1 kg / cm
The above adhesion was obtained. When an acceleration test was performed under high temperature and high humidity of 80 ° C. and 90% RH, the adhesion after 1000 hours was 900 g / cm, which was a level that was substantially no problem. The light transmittance at 550 nm after pattern processing is 74.
%, The light transmittance in the near infrared region is <10% (900 to
1200 nm), electric field shielding property is 200 to 1000
It was as good as 50 dB or more (Advantest method) in the range of MHz. On one side of a 2 mm thick polycarbonate substrate, a hard coat having a pencil hardness of 3H or more having an anti-reflection function added with a near-infrared cut material is applied, and a hard coat layer is formed with an aliphatic polyester urethane (AD-N401 manufactured by Toyo Morton) adhesive. A patterned substrate was laminated on the back surface. At the outer edge, each transparent conductive film and the flat cable were coated with silver paste (CRM-108 manufactured by Sumitomo Bakelite).
5) Adhesion and electrical grounding. The pencil hardness was 3H, which was excellent in abrasion properties. As a transparent plate for electromagnetic wave shielding for PDP, characteristics excellent not only in shielding properties but also in durability were obtained.

Example 2 A transparent electromagnetic wave shielding body was produced in the same manner as in Example 1 except that the transparent metal oxide film was SiOx. An adhesion test was performed in the same manner as in Example 1.
An adhesion of at least g / cm was obtained.

Comparative Example 1 In Example 1, copper was laminated without providing a transparent metal oxide film layer. When an adhesion test was performed in the same manner as in Example 1, the adhesion was 200 g / cm or less, and some lines were missing in the subsequent patterning step, resulting in a very poor yield.

[0022]

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 a diagram illustrating a layer configuration according to a first embodiment.

FIG. 2 is a layer configuration diagram of Comparative Example 1.

Claims (6)

[Claims] 1. The method according to claim 1, wherein at least one side of the transparent polymer film has
A transparent electromagnetic wave shielding body characterized in that a filter pattern is formed by sequentially laminating an adhesive layer, a transparent conductive film, and a metal thin film layer as necessary, and then selectively removing only the metal thin film layer by etching. 2. The electromagnetic wave shielding transparent body according to claim 1, wherein the metal thin film layer is made of copper. 3. The light transmittance at a wavelength of 550 nm is 50%.
The electromagnetic wave shielding transparent body according to claim 1 or 2, which is as described above. 4. An electromagnetic wave shielding transparent body comprising the electromagnetic wave shielding transparent body according to claim 1 laminated on a transparent polymer reinforcement having a thickness of 1 mm or more via an adhesive layer. 5. The electromagnetic wave shielding transparent body according to claim 4, wherein an antireflection layer is provided on at least one of the laminated film and the transparent polymer reinforcing body. 6. The electromagnetic wave shielding transparent body according to claim 4, wherein a hard coat layer is provided on at least one of the laminated film and the transparent polymer reinforcing body.