JPH0482003B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a shielding plate that has excellent transparency, has the property of blocking radiation and electromagnetic waves, and is useful as a filter for cathode ray tubes, etc. ,
More specifically, the present invention relates to a radiation and electromagnetic wave shielding plate which is a molded product having excellent optical transparency and mechanical strength, as well as moisture resistance, heat resistance, and scratch resistance.

(Prior Art) In recent years, radioactive materials have been used in various fields such as medicine, energy, schools, and research institutes. This radiation is not only harmful to the human body, but also has an adverse effect on surrounding equipment and materials. Against this background, it is necessary to shield radiation when using radioactive materials.

In addition, trace amounts of X-rays are emitted from cathode ray tubes (CRTs) used in office automation such as various computers and word processors.
It is known that electromagnetic waves are emitted, and various filters are being developed to block them and protect the human body.

For example, a method of polymerizing organic acid lead such as lead methacrylate together with a vinyl monomer (Japanese Patent Application Laid-Open No. 53-9996
No.) A method has been proposed in which a specific polyfunctional monomer is used as a part of the vinyl monomer (Japanese Patent Application Laid-Open No. 1797-1987).

(Problems to be Solved by the Invention) However, these known plastic materials use vinyl monomers, specifically methyl methacrylate (MMA), styrene (ST), hydroxyalkyl methacrylate, etc. as base monomers. (a) High polymerization shrinkage rate. (For example, about 20% in MMA,
(About 17% in ST) (a) When using hydroxyalkyl methacrylate, it has a hydrophilic group, so it has a high affinity for water and has poor moisture resistance. Furthermore, during molding, there is a problem of poor mold releasability due to high adhesion to glass plates and stainless steel plates that are generally used as molds.

(c) Since the boiling point of the monomer is low, there is a risk of foaming in the case of thick-walled products unless sufficient temperature control is carried out.

These problems remain, and as a result, molding is extremely difficult.

Furthermore, the mechanical strength of the molded product itself is still not sufficient, and the scratch resistance of the surface is also poor.

Therefore, the present invention solves the above-mentioned drawbacks without impairing the transparency, radiation shielding ability, and electromagnetic wave shielding ability of the material, and provides a shielding plate with excellent mechanical strength, moisture resistance, heat resistance, and scratch resistance. The purpose is to

(Means for Solving the Problems) According to the present invention, in order to provide a radiation and electromagnetic wave shielding plate having the above characteristics, (A) at least one polyol selected from the group consisting of polyol polyacrylate and polyol polymethacrylate; 15 to 60% by weight of a functional monomer, (B) 25 to 50% by weight of at least one lead-containing monomer selected from the group consisting of lead acrylate and lead methacrylate, and (C) lead organic acid.
A reticular electromagnetic shielding material is embedded in the polymerized cured product of the composition comprising 15 to 35% by weight.

This shielding material plate is produced by injecting the above radically polymerizable compositions (A) to (C) into a mold in which a net-like electromagnetic wave shielding material is fixed in the inner space, and polymerizing and curing the composition.

(Function) The shielding plate of the present invention (hereinafter sometimes referred to as shielding material) contains a radiation blocking substance in the form of a lead salt or a radiation blocking substance generally in the form of a porous body such as a net. An important feature is that the material is incorporated into a polymeric crosslink, in which a reticular radiation blocking material is embedded.

That is, the above component (B) used in the present invention binds the lead component to the polymer chain in the form of ions, and the above component (C)
By dissolving the lead component in the form of a salt in the polymer, the polymer molded product is given a radiation shielding effect while maintaining excellent transparency. The functional monomer (A) is characterized in that it can introduce a crosslinked structure while preserving these characteristics of the components (B) and (C).

In the transparent shielding material of the present invention, the electromagnetic wave shielding material is contained in the crosslinked polymer in an embedded state so that the transparency of the molded product is not substantially impaired, thereby imparting electromagnetic wave shielding properties. However, according to the present invention, by embedding a net-like electromagnetic wave shielding material in the polymerized cured product made of the compositions (A), (B), and (C), electromagnetic wave shielding can be achieved in a normal polymer molded product. It provides better electromagnetic wave shielding performance than structures with buried materials. The reason for this has not yet been elucidated, but the lead component present in the polymerized hardened material present in the mesh opening of the electromagnetic wave shielding material may be due to its own properties or due to its ionic conductivity. This is thought to be because it exhibits the property of blocking electromagnetic waves.

Moreover, according to the present invention, the matrix in the molded product is made into a polymer crosslinked product, which improves the mechanical strength of the material itself compared to molded products obtained from ordinary polymers made of single monomers or polymer blends. This can contribute to improving heat resistance.

Moreover, since the constituent component forming the basic skeleton of the crosslinked polymer of the present invention is the polyfunctional monomer (A), various excellent advantages can be achieved. In other words, the polyfunctional monomer (A) itself has a polymerization shrinkage rate as low as that of MMA.
Since it is much lower than ST, highly accurate casting molding is possible, and optical distortion due to residual stress and distortion after polymerization and curing can be prevented. Furthermore, since this polyfunctional monomer (A) has a very high boiling point, it can solve the problem of foaming and improve transparency.

(Operations and Effects of the Invention) According to the present invention, transparency, radiation shielding properties, and A transparent molded body with excellent electromagnetic wave shielding properties and improved heat resistance and mechanical strength can be obtained, and this product can be used as an inexpensive CRT filter, experimental equipment or industrial equipment that generates radiation and/or ultraviolet rays. It is useful for applications such as viewing windows or transparent shielding materials.

(Description of preferred embodiments of the invention) (A) Polyfunctional monomer In the present invention, at least one selected from the group consisting of polyol polyacrylate and polyol polymethacrylate is used as the polyfunctional monomer.

A typical example of this is the following general formula: In the formula, R ₁ is a hydrogen atom or a methyl group, and X represents an alkylene group, a hydroxy-substituted alkylene group, an alkyleneoxyalkylene group, or a poly(alkyleneoxy)alkylene group. .

Specific examples of such polyfunctional monomers (A) include, but are not limited to, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1 ,6
- hexanediol di(meth)acrylate,
1,3-butylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, tetramethylolmethane tri(meth)acrylate
Examples include acrylate. In this specific example, polyethylene glycol di(meth)
When selecting acrylate and polypropylene glycol di(meth)acrylate, the group X in the above formula is a poly(ethyleneoxy)ethylene group and a poly(propyleneoxy)propylene group, respectively, and the oxygen atom bonded to the terminal alkylene. to form an alkyleneoxy repeating unit, i.e. (-O-CH ₂ -CH ₂ )- _o or It is preferable to select one in which n is 4 to 23.
By making such a selection, it becomes possible to obtain a molded product with excellent transparency and mechanical strength from the resulting crosslinked polymer.

Among the polyfunctional monomers (A) mentioned above, it is particularly effective to select polyethylene glycol di(meth)acrylate and neopentyl glycol dimethacrylate having 9 to 23 repeating ethyleneoxy units. The reason for this is that the above-mentioned two polyfunctional monomers (A) have particularly excellent physical properties in terms of boiling point, curability, compatibility, and polymerization shrinkage rate, and are extremely easy to mold. This is because the molded product also has particularly excellent transparency, mechanical strength, moisture resistance, and scratch resistance.

(B) Lead-containing monomer The lead-containing monomer used in the present invention is at least one monomer selected from the group consisting of lead acrylate and lead methacrylate.

These lead-containing monomers themselves are conventionally known as materials that have transparent radiation-shielding ability when polymerized at temperatures above their melting points. However, the polymers obtained in this way are generally brittle and cannot withstand practical use in molding, processing, or use, and even when copolymerized with other monomers such as MMA, it is difficult to obtain strength that can be used in practical use. This monomer had the problem that when the copolymerization ratio was adjusted, the resulting polymer lost its transparency.

In the present invention, by using a lead-containing monomer having such properties in combination with other specific components as an element of a crosslinked polymer, radiation shielding ability is ensured without impairing the transparency of the polymer. I was able to do that.

In the present invention, at least one monomer selected from the group consisting of lead acrylate and lead methacrylate described above can be used, but lead methacrylate is preferably used from the viewpoint of transparency and mechanical strength.

(C) Organic acid lead In the present invention, organic acid lead is used in combination with the lead-containing monomer (B) as the lead-containing component.

A typical example of this organic acid lead is the following general formula (R COO) _a Pb where a is an integer equal to the valence of lead, and R is a saturated or unsaturated hydrocarbon residue having 5 to 20 carbon atoms. It is a lead salt of a monobasic organic fatty acid represented by
If the number of carbon atoms is 4 or less or 21 or more, the resulting crosslinked polymer will be unsatisfactory in terms of transparency and mechanical strength.

Specific examples of the organic lead acid include lead hexanoate, lead octylate, lead octylbenzoate, lead stearate, lead palmitate, lead palmitolate, lead linoleate, lead naphthenate, and the like.

Polymerizable Curable Composition Further, during polymerization, it is desirable to use the composition in the following proportions in view of the total balance of various physical properties such as radiation shielding ability, strength, and transparency as a radiation shielding material. That is, based on the three components (A), (B) and (C), the polyfunctional monomer (A) is 15 to 60% by weight, preferably 20 to 45% by weight, and the lead-containing monomer (B) is 25 to 50% by weight. % by weight, preferably 30 to 50% by weight, organic acid lead (C) 15
It is desirable to mix them in an amount of 35% to 35% by weight, preferably 25% to 35% by weight.

A catalytic amount of a radical initiator is added to this composition. As a radical initiator, t-butyl hydroperoxide, cumene hydroperoxide, di-
t-Butyl peroxide, peroxybenzoic acid-
Peroxides such as t-butyl, lauroyl peroxide, diisopropyl peroxydicarbonate, and methylene ethyl ketone peroxide, and azo compounds such as azobisisobutyronitrile and azobismethylisovaleronitrile are used. These radical initiators are preferably present in an amount of 0.1 to 5% by weight, especially 1 to 4% by weight, based on monomer.
These radical initiators can also be used in combination with accelerators such as various amines and metal soaps.

This polymerizable composition may optionally contain an ultraviolet absorber and the like.

As the ultraviolet blocking substance, any ultraviolet absorber can be used, but since the polymerized and cured molded product of the above components absorbs or reflects ultraviolet rays with a wavelength of 270 nm (nanometers) or less, it is preferable to use ultraviolet rays with a wavelength of 270 nm (nanometers) or less. It is preferable to use a substance having the ability to absorb ultraviolet rays having a wavelength in the range of 270 to 400 nm, particularly a benzophenone-based or benzotriazole-based ultraviolet absorbing substance.

Suitable examples of benzophenone-based and benzotriazole-based ultraviolet absorbing substances include, but are not limited to, the following.

2,2'-dihydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, 2,2',4,4'-tetrahydroxybenzophenone, 2(2 '-Hydroxy-5'-methylphenyl)benzotriazole, 2(2'-hydroxy-3'-tertbutyl-5'-methylphenyl)-5-chlorobenzotriazole, 2(2'-hydroxy-4'-octoxyphenyl) enil)
Benzotriazole, 2(2'-hydroxy-3',5'-di-tert-butyl)benzotriazole.

Electromagnetic Wave Shielding Material A conductive net is used as the electromagnetic wave shielding material. In this case, the opening degree of the conductive mesh is preferably in the range of generally 80 to 250 meshes, particularly 80 to 200 meshes, expressed in Tyler standard meshes. That is, if the mesh number is smaller than the above range, the electromagnetic wave shielding effect will be inferior to that within the above range, while if it is larger than the above range, the transparency will be impaired. Become.

As the conductive mesh, a wire mesh, especially a wire mesh having a copper plating layer, is used, and most preferably, a metal plating synthetic fiber gauze is used. 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 is formed by electroless plating (chemical plating), 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 preferably has an aperture ratio of generally 10 to 90%, particularly 30 to 80%, from the viewpoint of electromagnetic wave shielding properties and light transmittance.

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. That is, when using a metal net, punched metal, etc., the resin is less likely to shrink in the portion where the conductive net is provided, and the resin shrinks in other portions, resulting in internal strain or internal stress. for example,
For this reason, deformations such as warpage and bending easily occur in portions where the conductive network is deviated from the center of the resin molded body. 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 easy deformability, so that they are resistant to shrinkage during resin curing. The followability is good, and deformations such as warping and bending during molding, the generation of internal stress and internal strain, and the generation of cracks accompanying this can be effectively prevented.

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 (obtrusiveness). 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 resin 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.

Molding Method and Molded Body In FIG. 1 showing the cross-sectional structure of an example of the shielding material of the present invention, the shielding plate 1 is integrally molded with the resin 2 described above, and is formed between one surface 3 and the other surface 4. is embedded with metal-plated synthetic fiber gauze 5,
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 cured resin 2 and the metal-plated synthetic fiber gauze 5 are completely adhered and integrated, and there are no or almost no voids in the resin matrix or the interface between the resin and the metal-plated layer.

When forming a laminate structure between a conductive porous member and a resin, the conductive porous member is sandwiched between two pre-formed resin plates, and methods such as hot pressing, ultrasonic welding, and adhesive bonding are used. It is conceivable to integrate the two resin plates in this case, but in this case, fine voids inevitably remain between the conductive member and the resin, making complete integration difficult, and the interface between the two remains. Peeling may occur at the interface, or image distortion may occur at the interface.

According to the present invention, all of the above-mentioned drawbacks are solved by using the above-mentioned resin composition, embedding metal-plated synthetic fibers therein, and polymerizing and integrating the resin composition.

That is, the shielding material 1 of the present invention, as shown in FIG. Fixation and sealing are provided by flexible spacer parts 8, 8 which can follow contraction. The molding composition is injected into the space 9 between the glass plates 6 and 7, and polymerized and cured under the following temperature conditions to produce a shielding material.

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, a method may be employed that consists of a combination of polymerization at a relatively low temperature in the first stage and polymerization at a higher temperature in the second stage.

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.

(Example) Next, examples of the present invention will be shown.

Example 1 Polyethylene glycol dimethacrylate (n
=14) 20% by weight neopentyl glycol dimethacrylate (n
=14) 15% by weight Lead methacrylate 35% by weight Lead octylate 30% by weight 2(2'-Hydroxy-5'-methylphenyl)benzotriazole 0.1% by weight A mixture of the above proportions was heated and stirred at 70°C for 10 minutes to form a uniform mixture. After forming a solution, it was once cooled to 40°C, and 0.1% by weight of t-butyl perbenzoate was added to form a casting composition.

This composition was molded into a radiation and electromagnetic wave shielding plate using a mold shown in FIG. An electromagnetic wave shielding net made of 200 mesh polyester fiber monofilament gauze coated with copper 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 above composition was poured into this mold, heated at 80℃ for 3 hours,
Polymerization was carried out at 120°C for 2 hours. The resulting molded plate is made of lead.
It contained 30wt% and had not only radiation shielding ability, electromagnetic wave shielding ability, and ultraviolet shielding ability, but also excellent transparency, scratch resistance, mechanical strength, and moisture resistance.

Example 2 Polyethylene glycol dimethacrylate (n
=23) 20% by weight 1,3 butylene glycol dimethacrylate
15% by weight of lead methacrylate, 35% by weight of lead octylate, and 30% by weight of lead octylate were polymerized and cured in the same manner as in Example 1. The moldability was as good as in Example 1, and the physical properties of the obtained molded plate were also sufficient as in Example 1.

Comparative Example 1 MMA 35% by weight Lead methacrylate 35% by weight Lead octylate 30% by weight 2(2'-Hydroxy-5'-methylphenyl)benzotriazole 0.1% by weight Polymerization and curing were carried out in the same manner as in Example 1. The obtained molded plate had excellent transparency, but was inferior in scratch resistance and mechanical strength.

Comparative example 2 MMA 20% by weight ST 10% by weight 2-hydroxyethyl methacrylate 5% by weight Lead methacrylate 35% by weight Lead octylate 30% by weight 2(2'-Hydroxy-5'-methylphenyl)benzotriazole 0.1% by weight Implemented When polymerized and cured in the same manner as in Example 1,
It adhered tightly to the tempered glass plate and could not be released from the mold.

[Brief explanation of drawings]

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

Claims (1)

[Claims] 1 (A) At least one polyfunctional monomer selected from the group consisting of polyol polyacrylate and polyol polymethacrylate 15 to 60
(B) at least one lead-containing monomer selected from the group consisting of lead acrylate and lead methacrylate;
25 to 50% by weight, and (C) 15 to 35% by weight of organic acid lead, and a reticulated electromagnetic wave shielding material is embedded in the polymerized crosslinked product of the composition in such a way that the transparency of the molded product is not substantially impaired. A transparent radiation and electromagnetic wave shielding plate comprising: 2. The shielding plate according to claim 1, wherein the net-like electromagnetic wave shielding material is a metal-coated synthetic fiber gauze. 3 In a mold having a net-like electromagnetic wave shielding material fixed in the inner space, (A) 15 to 60% by weight of at least one polyfunctional monomer selected from the group consisting of polyol polyacrylate and polyol polymethacrylate, (B) acrylic acid. At least one lead-containing monomer selected from the group consisting of lead and lead methacrylate
and (C) 15 to 35% by weight of organic acid lead, and the composition is polymerized and cured in the mold. A method for manufacturing an electromagnetic shielding plate.