JPH0260496B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an electromagnetic wave shielding material that has excellent transparency and little optical distortion, and a method for manufacturing the same, and more specifically relates to deformations such as warping and bending during molding. The present invention relates to an electromagnetic wave shielding material that has no internal strain and internal stress, and has excellent clarity in transparent images, and a method for manufacturing the same.

Prior Art and Technical Problems of the Invention In recent years, with the advanced development of office automation equipment and other electronic devices, electromagnetic wave shielding effects have been developed to prevent noise in electronic devices and prevent direct effects of electromagnetic waves on the human body. , transparent electromagnetic wave shielding plates are in demand as CRT filters for office automation equipment and viewing windows for shielded rooms for electronic equipment.

Conventionally, such transparent electromagnetic wave shielding plates include: porous metal plates such as punched metal; articles made of transparent materials coated with conductive metal oxides or metals by vacuum deposition; conductive synthetic fiber networks themselves; stainless steel. wire mesh; etc., but due to corrosion etc.
The shielding effect tends to deteriorate over time, and it is difficult to obtain a sufficient shielding effect.Although it is relatively easy to obtain, it is not strong enough, and it is difficult to clean the screen from tearing, corrosion, and attached dirt. Both have drawbacks such as difficulty in obtaining small filament diameters.

Outline and Object of the Invention The present invention provides a method for embedding metal-plated synthetic fiber gauze among various porous conductive members in a radically polymerizable acrylic resin syrup and polymerizing the syrup. It has been found that it is possible to obtain an electromagnetic wave shielding material that is free from deformation such as warping or bending, suppresses the generation of internal strain and internal stress, and can form clear perspective images without distortion.

That is, an object of the present invention is to provide an electromagnetic wave shielding material that eliminates the above-mentioned drawbacks of conventional electromagnetic wave shielding materials.

Another object of the present invention is to provide a transparent electromagnetic wave shielding material that has excellent transparency and electromagnetic wave shielding properties, eliminates deformation and internal distortion during molding, and does not cause distortion of transparent images. It is in.

Still another object of the present invention is to provide a see-through electromagnetic wave shielding material that eliminates the aforementioned deformation and internal distortion that tend to occur when acrylic resin syrup is used as a laminating resin for porous conductive members, and a method for producing the same. It is on offer.

Structure of the Invention According to the present invention, there is provided a see-through electromagnetic wave shielding material characterized in that at least one sheet of metal-plated synthetic fiber gauze is embedded in an acrylic resin molded body.

According to the present invention, a radically polymerizable acrylic syrup is injected into a mold in which a metal-plated synthetic fiber gauze is spread and fixed in the inner space, and the acrylic resin and the gauze are integrated by polymerizing the syrup. A method for producing a see-through electromagnetic shielding material is provided, which comprises obtaining a molded body.

Preferred Embodiment of the Invention In FIG. 1 showing the cross-sectional structure of the electromagnetic wave shielding material of the present invention, the shielding material 1 is integrally molded with acrylic resin 2, and there is a metal between one surface 3 and the other surface 4. Metsuki synthetic fiber gauze 5 is buried,
The two resins partitioned by this metal-plated synthetic fiber gauze are connected through the openings in the gauze 5 and are completely integrated. That is, the acrylic resin 2 and the metal-plated synthetic fiber 5 are completely adhered and integrated,
There are no or almost no voids in the resin matrix or the interface between the resin and the metal plating layer.

When forming a laminate structure between a conductive porous member and an acrylic resin, the conductive porous member is sandwiched between two pre-formed acrylic resin plates and bonded using hot press, ultrasonic welding, or adhesive. It is conceivable to integrate both resin plates by means of a chemical agent, but in this case, fine voids inevitably remain between the conductive member and the resin, making complete integration difficult. Peeling may occur at the interface between the two, or image distortion may occur at the interface.

According to the present invention, all of the above-mentioned drawbacks are solved by using radically polymerizable acrylic syrup, embedding metal-plated synthetic fibers therein, and polymerizing and integrating them.

That is, as shown in FIG. 2, the electromagnetic wave shielding material 1 of the present invention has a spacer or gasket 8 in the center of sheet-like molds 6 and 7 made of, for example, reinforced glass, which can follow the shrinkage during polymerization and curing. , 8 to fix the metal-plated synthetic fiber gauze 5 in a liquid-tight manner, and inject a composition containing an acrylic monomer, an acrylic resin prepolymer, and a radical polymerization initiator into this space 9. Obtained by polymerization under heating.

The radical polymerizable acrylic resin syrup is a syrupy liquid composition containing an acrylic resin prepolymer and an acrylic monomer. A preferred acrylic resin syrup is based on methyl methacrylate.

This methacrylic resin syrup is obtained by adding a small amount of a radical polymerization initiator to a monomer mainly composed of methyl methacrylate, heating the mixture in a prepolymerization tank, and partially polymerizing the mixture. The degree of partial polymerization is suitably within a range such that the polymerization rate is 10 to 30%. For the purpose of syrup moldability and resin modification, styrene monomers such as styrene and vinyltoluene, and other acrylic monomers such as ethyl acrylate and butyl methacrylate are used before or after partial polymerization. can be mixed. These modifying monomers are preferably used in an amount of 10 to 30% by weight per syrup.

The raw material resin syrup has a rating of 500% in terms of mixability with the components described later, castability, and post-polymerization curing properties.
Preferably, the viscosity is between 2000 centipoise (CPS) and 2000 centipoise (CPS). This syrup is mixed with a radical initiator and used for molding.

As radical initiators, organic peroxides such as benzoyl peroxide and lauryl peroxide, and azo compounds such as azobisisobutyronitrile are used.
Generally used in amounts of 0.05 to 2% by weight, especially 0.2 to 2% by weight, based on the resin syrup.

The casting composition of the present invention may contain known auxiliary agents or compounding agents, such as coloring agents, viscosity modifiers, antioxidants, mold release agents, etc., to the extent that their essence is not impaired. It can be formulated in a prescription.

In the present invention, a metal-plated synthetic fiber gauze is used in combination with a superfilled resin. The metal-plated synthetic fiber gauze is obtained by weaving or knitting monofilament or multifilament yarn or spun yarn of polyester, nylon, vinylon, acrylic, etc. into a coarse weave, and adding copper, nickel, cobalt, etc. A plating layer of metal such as chromium, silver, or aluminum is used. The plating layer can be formed by electroless plating (chemical plating),
This can be done by vacuum deposition or a combination of these and electroplating. The plating layer may be formed to such an extent that these surfaces become sufficiently conductive but do not cause clogging. The plating layer may be a single metal layer or may be composed of a plurality of metal layers, for example, a combination of an electroless plating layer and an electrolytic plating layer is used. The metal-plated synthetic fiber gauze used in the present invention has a mesh size of 80 to 250,
In particular, it is desirable to have a mesh of about 100 to 200 meshes from the viewpoint of electromagnetic wave shielding properties and light transmittance, and the aperture ratio is generally 10 to 90%, especially 30%.
It is desirable that the ratio be within the range of 800% to 800%.

According to the present invention, by using metal-plated synthetic fiber gauze as the conductive net, extremely large advantages can be achieved in relation to molding shrinkage of the resin and the like. In other words, the molding shrinkage rate of methacrylic resin is on the order of about 20%, but when using metal nets, punched metal, etc., resin shrinkage is less likely to occur in areas with conductive nets, and resin shrinks in other areas. As a result of this contraction, internal strain or internal stress occurs. For example, in a portion where the conductive network is deviated from the center of the resin molded body, deformation such as warping or bending easily occurs. Furthermore, during use or when exposed to heat, cracks are likely to occur and transparency may be impaired. On the other hand, according to the present invention, even when producing a relatively large-sized molded object, the synthetic fibers that form the base of the conductive network have flexibility and deformability, so that they can withstand shrinkage during resin curing. It has good followability and effectively prevents deformations such as warping and bending during molding, the generation of internal stress and strain, and the occurrence of cracks accompanying these.

Moreover, with synthetic fibers, monofilaments with small diameters can be easily obtained, and the strands of the conductive network themselves can be made extremely fine.
When used in OA equipment, CRT filters, etc., it is transparent and does not cause any discomfort (obstruction). Further, this metal-plated synthetic fiber gauze itself has good workability such as cuttability, and the molded article in which it is embedded also has good workability. Furthermore, this material also has the advantage of good followability during bending.

In the electromagnetic shielding material of the present invention, since the metal-plated synthetic fiber gauze has good shrinkage followability, the position where it is buried is not particularly limited; for example, it may be located in the center of the molded body, or it may be placed in any It may be provided offset to the surface side. Furthermore, two or more sheets of metal-plated synthetic fiber gauze can be provided if desired. The metal plating layer may be colored if desired. Furthermore, in order to improve the adhesion with the resin,
The surface of the metal-plated synthetic fiber gauze may be previously treated with a coupling agent such as triethoxyaminopropisilane. Further, it may be dyed black for the purpose of removing metallic color.

Polymerization can be carried out by any method known per se, for example, a one-stage polymerization method or a two-stage polymerization method. For example, in the latter two-stage polymerization method, a method may be employed in which the first stage is a polymerization at a relatively low temperature, and the second stage is a combination of polymerization at a higher temperature.

Furthermore, heat treatment can be performed at a temperature higher than the glass transition temperature (Tg) of the resin for the purpose of removing internal strain caused by polymerization shrinkage.

The electromagnetic wave shielding material according to the present invention not only has excellent electromagnetic wave shielding function and can be seen through, but also because the manufacturing method is the cell cast method, it is completely integrated with the conductive net, and can be bonded by welding or adhesive. There is no risk of peeling, fine voids, image distortion, etc. Also, since it is made of resin, functions other than electromagnetic wave shielding, such as ultraviolet ray protection, can be easily obtained.

In addition, by forming a plate with conductive fiber gauze embedded in acrylic resin with excellent properties,
An electromagnetic wave shielding material is provided that solves the above-mentioned problems such as corrosion and tearing of the mesh, is easy to clean, is uniform as a whole, and does not feel strange when used as a CRT filter for office automation equipment.

Example 0.1% by weight of benzoyl peroxide was added to methyl methacrylate and heated to 80°C in a prepolymerization vessel to produce an acrylic resin syrup (viscosity 1000 cps) with a polymerization rate of about 25%. A casting composition was prepared by blending 0.5% by weight of benzoyl peroxide with this resin syrup. This composition,
It was molded into an electromagnetic shielding plate using the mold shown in FIG. An electromagnetic wave shielding net made of 200 mesh polyester fiber monofilament gauze coated with steel in a non-clogging state is placed under uniform tension. Next, a gasket was placed on each peripheral edge of two 400 m/m square glass plates, and the electromagnetic shielding net was sandwiched between the two glass plates, which were then clipped to form a gap of 3 m/m.

The removed casting composition was injected through an injection port provided at the top of the gasket, and polymerized and cured at 80°C for 3 hours.

The obtained electromagnetic wave shielding plate had no deformation such as warping or bending, had excellent transparency, and was completely unobtrusive when used as a filter.

Effects of the Invention According to the present invention, a metal-plated synthetic fiber gauze is used as a conductive net for an acrylic resin molded body, and by embedding this in the resin, deformation such as warping and bending, and internal distortion during molding can be prevented. An electromagnetic wave shielding material is provided that effectively prevents the generation of internal stress, has excellent transparency, has no image distortion, and has excellent various properties.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a transparent electromagnetic wave shielding material according to the present invention, and FIG. 2 is an explanatory diagram for explaining the production of the electromagnetic wave shielding material of the present invention. 1 is electromagnetic wave shielding material, 2 is acrylic resin, 3, 4
5 is the surface, 5 is the metal-plated synthetic fiber gauze, 6 and 7 are the molds, and 8 is the gasket.

Claims (1)

[Scope of Claims] 1. A transparent electromagnetic wave shielding material, characterized in that at least one sheet of metal-plated synthetic fiber gauze is embedded in an acrylic resin molded body. 2. The shielding material according to claim 1, wherein the metal-plated synthetic fiber gauze has a mesh of 80 to 250 meshes. 3. A radically polymerizable acrylic syrup is injected into a mold in which a metal-plated synthetic fiber gauze is spread and fixed in the inner space, and the syrup is polymerized to obtain a molded product in which the acrylic resin and the gauze are integrated. A manufacturing method for transparent electromagnetic shielding material consisting of: