JPH01158799A - Manufacture of transparent electromagnetic wave shielding sheet - Google Patents

Abstract

PURPOSE:To realize a transparent electromagnetic wave shielding sheet which has a high strength and maintains a high reliability for a long term and in which a transparent plastic sheet is simply buried (sticking) without a possibility of peeling-off by employing a meshed conductive woven cloth as a shielding layer. CONSTITUTION:A woven cloth woven so as to form meshes is prepared. The woven cloth is impregnated with conductive coating of adhesive resin and conductive metal powder dispersed in the adhesive resin and dried to make a conductive woven cloth. Then the meshed conductive woven cloth is laminated with transparent plastic. The method of lamination is such that a transparent plastic film is extruded on the meshed conductive woven cloth and coated on the cloth or by thermocompression bonding. Otherwise, the transparent plastic film may be applied to the cloth by dry lamination. With this constitution, a shielding sheet in which the meshed conductive woven cloth and the transparent plastic are unified can be obtained. As the conducting part is made of the meshed cloth, the sheet is flexible and, as the cloth is impregnated with the conductive coating, the conductive coating film is not peeled off.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention is transparent and highly flexible, and can be attached to window glass in shield rooms, used as a shield curtain, or directly wrapped around objects to be shielded. The present invention relates to a method for manufacturing a shield sheet that can be used as a sheet or a bag.

(Prior Art) With the rapid development of electronic devices in recent years, electromagnetic interference has become a problem, and various electromagnetic shielding sheets have been developed as a preventive measure. However, a typical manufacturing method for a sheet that exhibits an electromagnetic wave shielding effect while maintaining transparency is a metal sheet with mesh-like holes made by etching, punching, etc. on a highly transparent plastic sheet. A manufacturing method in which a conductive metal is vapor-deposited in a mesh shape on a transparent plastic, a method in which a mesh pattern is printed on a transparent plastic, a method in which fine metal wires are woven into a mesh shape and then bonded to a transparent plastic, etc. It has been known.

(Problems to be Solved by the Invention) In the conventional technique described above, the method of laminating a metal sheet with mesh-like holes to a transparent plastic sheet requires time and effort to manufacture the metal foil, and is not flexible. The vapor deposition method of conductive metal has disadvantages such as poor processability, heavy weight, and high cost.The vapor deposition method of conductive metal has a thinner vapor deposition film on the product sheet, so the physical surface strength is weak and it is difficult to attract attention. It is easily peeled off by scratching or pressure, has poor flexibility, cracks occur when bent, and conductive paths are cut. Moreover, it has problems in that it has a poor yield and is expensive to manufacture.

Also, when printing conductive paint on transparent plastic, you need to be careful of fire when using a solvent, and in addition, when printing a mesh pattern on a large sheet, it is difficult to get the desired coating amount. There is a problem in that it is difficult to apply it uniformly over the entire surface.

Furthermore, the method of weaving thin metal wires into a mesh shape requires a complicated weaving process, resulting in high costs, and is also difficult to bond with a transparent plastic sheet.

(Means for Solving the Problems) The present invention aims to solve the problems of the above-mentioned conventional techniques and provide a shield sheet that is relatively simple and has good quality performance.The outline thereof is as follows. That's right.

A woven cloth woven into a mesh shape is prepared, and a conductive paint made by dispersing conductive metal powder in an adhesive resin is impregnated and applied, and then dried to create a conductive woven cloth. The present invention relates to a method of manufacturing a transparent electromagnetic shielding sheet by laminating transparent plastic onto a mesh-like conductive woven fabric. In this case, as a laminating means, extrusion coating or thermocompression bonding of a transparent plastic film on the mesh-like conductive woven fabric, or a means of laminating a transparent plastic film by dry lamination is applicable to the present invention. The aim is to obtain a transparent electromagnetic shielding sheet in which a mesh-like conductive woven fabric and transparent plastic are integrated.

(Function) According to the present invention, the conductive part is made of a mesh-like woven fabric, so it is flexible, and the woven fabric is coated and impregnated with a conductive paint. This differs from vapor deposition or printing methods, in which the film easily peels off.

By attaching or covering an object with the sheet obtained according to the present invention, it is possible to exhibit an electromagnetic shielding effect and a protective effect.

The fiber material of the woven fabric used in the present invention is not particularly limited (natural fibers such as hemp and cotton, nylon, polypropylene,
Plastic fibers such as polyester and acrylic fibers and carbon fibers are used, and woven fabrics in which voids are formed between the fibers, such as tulle, curtain fabric, and screen door netting, are preferred. In particular, those using plastic fibers are more preferable because they cause less fuzz.

In addition, the metal particles constituting the conductive paint impregnated with this are approximately 0.1 to 10/im, and the metal types include gold, silver, copper, nickel, zinc, ferrite, and stainless steel. Other metals or alloys,
These can be used alone or in combination of two or more.

In addition, by mixing carbon blank and graphite in this conductive metal, the strong stimulation caused by reflected light to the viewer when using only the metal can be alleviated by blackening, and the result is less irritating. Can be used as a shield.

Furthermore, various binders such as rubber and plastic are used as binders, such as polyester, acrylic, urethane, phenol, etc.
Examples include rubber-based, silicone-based, and epoxy-based binders, and curing type binders such as thermosetting or self-crosslinking are also applicable to the present invention.

However, this binder is selected depending on the mesh-like woven fabric base material to be used, and has high reliability that can withstand long-term use with little change over time in terms of adhesion, heat resistance, weather resistance, heat and humidity resistance, etc.
It is necessary to select an adhesive with good processability; for example, for fibers such as nylon, polyethylene, and polyester, highly reliable self-crosslinking polyester-based commercially available adhesives can be obtained.

In addition, the electrical resistance of conductive paints varies depending on the particle size and amount of the metal used, but there is a significant correlation between the electrical resistance of conductive paints and the electromagnetic shielding properties. The lower the value, the better the electromagnetic shielding properties.

Therefore, it is desirable that the electrical resistance of the paint composition used be as low as possible, with a volume resistivity of 5X10-'Ω・cm.
Hereinafter, the sheet resistance needs to be 9×10-'Ω/mouth or less.

As a means of filling the voids (spaces) of the conductive fabric with transparent plastic and supporting the same fabric, for example, a transparent plastic film made of polyolefin film such as polyethylene or polypropylene is layered on the conductive fabric. It can be produced by passing it through a hot roll and bonding it by pressure or by hot pressing, or by extruding a transparent resin such as polyolefin onto a conductive fabric using an extrusion lamination method.

Furthermore, when a transparent plastic film is used to embed a space in a mesh-like conductive woven fabric, the actual image of an object on the opposite side may not be visually discernible simply by embedding the film. In other words, even if the so-called light transmittance is sufficient, transparency (see-through) cannot be obtained.The cause of this is that the temperature of the plastic is low when embedding the conductive fabric, the nip pressure is low, or the nip roll This occurs because light scattering occurs because the plastic film has a rough surface, and either the front or back surfaces of the plastic film are not smooth. In order to prevent this, it is necessary to make both the front and back surfaces of the film sufficiently smooth.

Next, since the transparent plastic attached to this conductive woven fabric supports the conductive mesh woven fabric, in addition to transparency, it has a melting point that is equal to or lower than the melting point of the mesh woven fabric. Preferred examples include, but are not limited to, polyethylene, polypropylene, nylon, and modified products thereof. However, if the above-mentioned modified substances are not selected and used in a manner that is compatible with the resin of the conductive coating composition, there is a risk of poor adhesion and other deterioration of quality performance due to changes over time.

Since either a thermosetting resin or a self-crosslinking resin is used as the resin base of the conductive coating composition used in the present invention, drying after impregnating and coating the mensch-like woven fabric is carried out in a suspended state. It is necessary to perform a curing process. Conditions vary depending on the type of resin used, but - For boat fishing, the drying temperature is 70°C to 150°C for several minutes, and the curing is at 20°C to 85°C for 0.5 to 200 hours. It is carried out in the process of In order to satisfy both effective electromagnetic shielding properties and transparency, it is important to use a conductive paint with as low electrical resistance as possible, but shielding properties can also be affected by the pattern of the mesh fabric and the amount of coating applied. and transparency are greatly affected.

Furthermore, it is recognized that the shielding effect is directional (in the near field) when using only parallel line patterns.
A sufficient electromagnetic shielding effect cannot be obtained unless the conductive portion is in a mesh shape as in the present invention. In addition, this mesh pattern can basically be of various shapes such as a grid (square), a triangle, a polygon, a circle, an oval, etc., but it is of course possible to adopt a mesh pattern that is fashionable. It is.

Furthermore, depending on the fiber diameter of the mesh pattern, the size of the void area, the size of the transparent area, and the amount of conductive paint applied,
Electromagnetic shielding properties and transparency are different, but if you make the mesh finer, thicken the fiber diameter, use multiple fibers, or increase the amount of conductive paint applied to improve electromagnetic shielding, transparency can be achieved. On the other hand, if the mesh is made larger, the fiber diameter is made smaller, and the amount of conductive paint impregnated is reduced in order to improve transparency, the electromagnetic shielding property will be reduced.

The electromagnetic shielding sheet obtained according to the present invention has a structure as shown in FIG. 1, and is composed of a mesh-like conductive woven fabric 1 and a transparent plastic sheet 2. For example, as shown in Fig. 2, an adhesive layer 3 is provided on the surface in contact with the conductive fabric, a releasable plastic layer 4 is provided on this, and the adhesive is used as needed to attach the window glass. You can also obtain something that can be attached to, etc.

The cross-sectional structure of the conductive fibers constituting the conductive woven fabric 2 used here is as shown in FIG. However, it is not limited to this figure.

Further, if the plan view of each side of the product obtained by the present invention is shown in FIG. 4, a highly fashionable product can be manufactured.

Although not shown, the sheet of the present invention can be folded into a U-shape and the edges heat-sealed to make a bag.
It is also possible to heat seal the opening of the bag or attach a zipper to the bag so that it can be opened and closed.

Further, it is also possible to create a sheet having an ultraviolet absorbing effect by selecting a transparent UV absorber as a constituent material of the present invention and incorporating it into, for example, a transparent plastic or an adhesive layer.

(Example) Example 1 The following materials were prepared.

(1) Conductive paint A binder made of polyester resin is coated with PCA (
(2) Mesh-like woven nylon tulle (3) Electrically conductive Paint impregnation coating conditions Coating amount: 18.5 g/pot Drying and curing: 120°C, 10 min (4) Transparent plastic resin and film formation Extrusion conditions Modified polyethylene resin (Dow Chemical Co., Ltd. ethylene acrylic acid copolymer) (Product name Primacol 3330) Extrusion temperature 250°C 1 Thickness 300 pm (5) Adhesive Acrylic resin (Soken Chemical Co., Ltd. Product name Thermoisocyanate curing agent (Soken Chemical Co., Ltd. product name D-9090% solution) 0.06 weight Diluted with solvent toluene ≧ parts by weight (6) Release film polyethylene terephthalate film with a thickness of 38 μm coated with a silicone release paint on one side and baked (Souken Kakosha) (7) Glass plate microslide Glass thickness 1 mm x width 52 mm x length 76 mm Next, the above conductive coating composition was diluted with a solvent and adjusted to a solid content concentration (viscosity) that was easy to impregnate and coat, and then applied to a mesh-like woven fabric. A conductive woven fabric was prepared by coating and impregnating the solid content at 18.5 g/g, drying and curing at 120°C for 10 minutes at the same time.Then, using a T-die hot melt extrusion laminator, 250 g of Primacol resin was applied. A transparent electromagnetic shielding sheet was prepared by laminating the sheet onto the conductive fabric described above while extruding it to a thickness of 300 μm at °C and embedding it in the voids of the fabric.

On the other hand, 2.6 g/solid acrylic adhesive was applied to mold release polyethylene terephthalate coated with silicone mold release agent.
n (After coating and drying, the conductive fabric of the sheet was bonded so as to be in contact with the exposed surface.Next, in order to put the transparent electromagnetic shielding sheet according to the present invention into practical use, this releasability was determined. Film (polyethylene terephthalate)
While peeling off and removing the sample, a sample was prepared by pasting it on a 1 mm thick experimental microslide glass plate.

Next, store this sample at 21℃ 65%RH 140'C90
It was left for 1000 hours under the following conditions: %RH 180°C, 90%RH 185°C dry. In addition, the sample was measured using a fade meter for 384 hours (equivalent to 2 years of sunlight).
Irradiated with ultraviolet light. Transparency, electromagnetic wave shielding properties, and hue for each sample under each of the above-mentioned storage or irradiation conditions,
Changes over time in bubbles, peeling, appearance, etc. were investigated. As a result, the amount of 500
As for shielding characteristics at MHz, stable electromagnetic shielding characteristics were obtained as shown in FIG.

In addition, no changes over time were observed in other properties.
It was confirmed that the transparent electromagnetic shielding sheet according to the present invention has good reliability.

(Effects of the Invention) According to the present invention, since a mesh-like conductive woven fabric is used as a shielding layer, it is possible to obtain an electromagnetic wave shielding property with high strength and high reliability over a long period of time. Also, embedding (bonding) of transparent plastic sheet
This can be carried out extremely easily and without fear of peeling, and a shielding material that maintains transparency and electromagnetic shielding properties over a long period of time can be provided at low cost.

[Brief explanation of the drawing]

FIGS. 1 and 2 are cross-sectional views of examples of transparent electromagnetic shielding sheets obtained using the present invention, and FIG. 3 is the above-mentioned FIG.
Fig. 2 is a cross-sectional view of the conductive fiber, Fig. 4 is a plan view of an example of a transparent electromagnetic shielding sheet obtained by the present invention, and Fig. 5 is a change over time in the electromagnetic shielding effect of the sheet obtained by the present invention. This is a graph showing. 1: Conductive woven fabric, 2: Transparent plastic sheet, 3:
Adhesive layer, 4: Release plastic layer, 10: Fiber (filament), 11: Coating and impregnating layer of conductive paint Agent: Patent attorney Mori Takeuchi Seisho (self-proposal) February 3, 1988 Kunio Ogawa, Commissioner of the Japan Patent Office1, Indication of the case: Patent Application No. 31674.7 of 19882, Title of the invention: Method for manufacturing transparent electromagnetic shielding sheet 3, Person making the amendment Relationship with the case Patent applicant address 5-15 Kyobashi-chome, Chuo-ku, Tokyo Name
Tomoe Paper Mill Co., Ltd. Representative Takao Inoue 4, Agent 101 Address 2-15-13-66 Uchikanda, Chiyoda-ku, Tokyo
Number of inventions increased by amendment 07, "Detailed description of the invention" column of the specification subject to amendment and Figure 5 of the drawings (
1) On page 8, line 16 of the specification, the word ``kurusu'' is amended to ``kurusu''. (2) Page 10, line 17 of the specification: ``Correct the word ``2'' in ``1'' to ``1''. (3) r2.6 g/mJ on line 14 @ line 9 of the specification
(4) In Figure 5 of the drawings, the phrase 1 (electromagnetic waves) is revised to read ``(electromagnetic waves)'' as shown in the attached sheet. I”d

Claims (1)

[Claims] A conductive paint made by dispersing conductive metal powder in an adhesive resin is impregnated and coated on a mesh-like woven fabric, dried to create a conductive woven fabric, and then the mesh-like conductive A method for manufacturing a transparent electromagnetic shielding sheet, characterized in that a sheet in which the conductive woven fabric and transparent plastic are integrated is formed by laminating transparent plastic on a conductive woven fabric.