JPH09107194A - Manufacture of high electromagnetic wave shielding composite sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent breaking and powdering without damaging the conductivity by laminating and joining one sheetlike base substance or more containing fiber cloth on to at least one surface of a conductive fiber-resin integrated layer, and exfoliating a heat resistant exfoliation sheet from the conductive fiber-resin integrated layer before and after joining. SOLUTION: Conductive short fiber is spreayed on a resin solution applied layer made by applying a resin solution composed mainly of thermoplastic polymer material on the exfoliating surface of a heat-resisting exfoliation sheet. This resin solution applied layer is solidified and a resin matrix layer is formed, and the conductive short fiber deposited layer and the resin matrix layer supporting it are pressure-processed. By doing this way, the conductive short fiber deposited layer is buried at least in the surface layer part of the resin matrix layer and a conductive fiber-resin integrated layer 2 is formed. At least one sheetlike base substance 1 containing fiber cloth is laminated and joined on to at least one surface of this conductive fiber-resin integrated layer 2.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a composite sheet having excellent electromagnetic wave shielding properties and high flex resistance. More specifically, the method of the present invention exhibits excellent durability even when used in applications which are repeatedly subjected to a bending action such as fluttering by wind, etc., has excellent electromagnetic wave shielding properties, and is highly bendable, and has high bending resistance. The present invention relates to a method for efficiently producing a functional composite sheet.

[0002]

2. Description of the Related Art Conventionally known conductive sheet materials include metallic fillers such as metal powder and metal flakes, non-metallic inorganic fillers such as carbon black and graphite in a matrix made of a polymer material. There is a sheet-shaped one in which powder, flakes, or metallized glass fibers, for example, glass fibers metallized by a chemical vapor deposition method, an electroplating method, an electroless plating method or the like are dispersed and contained. In general, the conductive sheet or film, since the matrix made of the polymer material is easy to stretch, as a whole,
When it is repeatedly stretched or momentarily loaded, it tends to stretch easily. In this way, when the conductive sheet or film is stretched or deformed, a change occurs in the distribution of the conductive filler dispersed therein,
As a result, the resistance value and the electromagnetic wave shielding property are changed, and the performance thereof is deteriorated, which may eventually lead to loss of practicality.

In order to solve the above drawbacks, for example, the present inventor has attempted to form or adhere a conductive sheet or film on one side or both sides of a base fabric made of a fiber material. . Such a conductive composite sheet substantially eliminates the above-mentioned drawbacks of a conventional conductive sheet or film, and has been practically useful. However, for applications requiring extremely high electromagnetic wave shielding properties, the conductive sheet or film must have a very high concentration of conductive material, and have a shape with high conductive efficiency, such as a conductive fiber having a relatively long length. It is necessary to use in the shape of. In this way, the coating liquid containing a large amount of conductive material with a long length becomes lumpy,
The spreadability of the coating becomes extremely low, making it impractical, and when the amount of solvent is increased to improve the coating property, the conductive material precipitates or localizes in the coating solution,
In addition, when the coating liquid layer is dried and solidified, there are disadvantages such as the formation of a large number of pores, which is not practical. Generally, when the conductive fiber-containing layer is formed by the conventional method, it is extremely difficult to increase the volume content ratio of the conductive fiber in the layer to more than 7.5%. In addition, when the volume content of the conductive fibers is low, it is necessary to form a conductive fiber-containing layer having a considerably large thickness in order to obtain a desired electromagnetic wave shielding property. For example, in order to obtain a shielding property of 40 dB, the thickness of the conductive fiber-containing layer having a conductive fiber volume content of 10% or more is 0.1 mm or more, but the volume content is 7% or more. 0.5% or 5%, the conductive fiber containing layer is 0.50 mm or more, or 1.0
Since the thickness of mm or more is required, the required amount of the conductive short fibers is significantly increased. Furthermore, when the conductive material is mixed with the polymer material and the mixture is applied to a mixer, a kneader, or a calender, the conductive material, particularly the fibers, is cut and pulverized by the shearing force, and the conductive material is mixed. In the case of a plating material, there arises a problem that the plating is peeled off and the conductivity is lowered.

[0004]

The method of the present invention eliminates the above-mentioned drawbacks of conventional electromagnetic wave shielding composite sheets, and a desired amount of conductive fiber material is placed in a resin matrix at a desired site without breaking it. An object of the present invention is to provide a method capable of being integrated, having excellent electromagnetic wave shielding properties, and efficiently manufacturing a high electromagnetic wave shielding composite sheet having excellent bending resistance.

[0005]

The method (1) for producing a composite sheet with high electromagnetic wave shielding property according to the method of the present invention comprises a polymer material having thermoplasticity as a main component on the release surface of a heat resistant release sheet. To form a resin liquid coating layer, sprinkle and deposit conductive short fibers on the resin liquid coating layer, and solidify the resin liquid coating layer to form a resin matrix layer. The short fiber spattering deposit layer and the resin matrix layer carrying it are subjected to a pressure treatment, whereby the conductive short fiber spattering deposit layer is embedded in at least the surface layer portion of the resin matrix layer to conduct the electric conduction. Forming a conductive fiber-resin integrated layer, and laminating and bonding a sheet-like substrate containing at least one fiber cloth on at least one surface of the conductive fiber-resin integrated layer, before the laminating and binding operation. , Or after, before Heat-resistant release sheet the conductive fibers - peeled from the resin integral layer, it is characterized in. Another method (2) for manufacturing a high electromagnetic wave shielding composite sheet according to the method of the present invention is to apply a resin liquid containing a thermoplastic polymer material as a main component on the release surface of a heat resistant release sheet. A resin liquid coating layer is formed, conductive short fibers are sprinkled and deposited on the resin liquid coating layer, and a sheet-like substrate containing at least one fiber cloth is laminated on the conductive short fiber sprinkling deposited layer. , Before or after the laminating operation,
The resin liquid coating layer is solidified to form a resin matrix layer, and the laminated body is subjected to a pressure treatment, thereby burying the conductive short fiber spattering deposition layer in at least the surface layer portion of the resin matrix layer. While forming a conductive fiber-resin integrated layer by binding the sheet-shaped substrate and the conductive fiber-resin integrated layer, before the pressure treatment,
Alternatively, the heat-resistant release sheet is released from the resin matrix layer later. The fiber cloth-containing sheet-like substrate used in each of the above methods (1) and (2) is at least one of the fiber cloths.
The surface may be covered with a substrate coating layer containing a thermoplastic polymer material as a main component. The method (1) and (2) for producing a high electromagnetic wave shielding composite sheet according to the method of the present invention provides a surface containing a flexible polymer material as a main component on the conductive fiber-resin integrated layer. The method may further include the step of forming a protective layer.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The sheet-like substrate used in the method of the present invention comprises at least one fiber cloth and may be composed of only the fiber cloth, or At least one surface of this fiber cloth may have a substrate coating layer containing a polymer material having thermoplasticity as a main component, or a flexible resin between two or more fiber cloths. An intermediate layer containing a material as a main component may be arranged.

The fibers constituting the fiber cloth include natural fibers such as cotton and hemp, inorganic fibers such as glass fibers, carbon fibers and metal fibers, regenerated fibers such as viscose rayon and cupra. Semi-synthetic fibers such as cellulose and triacetate fibers, and synthetic fibers such as nylon 6, nylon 66, polyester (polyethylene terephthalate), aromatic polyamides, aromatic polyesters, acrylic polymers, polyvinyl chloride, vinylon, and It can be selected from polyolefin fibers and the like, and particularly high strength fibers (15 to 50 g / d) and / or high heat resistant fibers can also be used. Preferred fibers for the method of the present invention include polyester fibers, polyamide fibers, water-insolubilized polyvinyl alcohol fibers, aromatic polyamide fibers, and aromatic polyester fibers. The fibers in the fiber cloth may be any shape such as a short fiber spun yarn, a long fiber thread, a split yarn, a tape yarn, and the fiber cloth may be a woven fabric, a knitted fabric, a non-woven fabric, a paper-like product, and Any of these two or more composite sheets may be used.
Generally, the fibers used in the method of the present invention are preferably polyester fibers, and the fibers are preferably in the form of long fibers (filaments). The fiber fabric used in the method of the present invention is useful for suppressing the elongation of the obtained composite sheet and maintaining its mechanical strength at a high level. Examples of useful woven fabrics include twill weaves, plain weaves, leno weaves, warp weaves, special knitted fabrics, and other fabrics having a structure. There is no particular limitation on the weight, thickness, etc. of the fiber cloth, but in general, those having a weight of 300 to 1000 g / m ² and / or a thickness of 0.05 to 1.0 mm are preferable. In the composite sheet obtained by the method of the present invention, the sheet-shaped substrate containing the fiber cloth suppresses expansion and deformation of the conductive coating layer to stabilize the electromagnetic wave shielding property of the composite sheet, and durability against fluttering and repeated bending. Of the conductive fiber can be improved.
It is also effective to maintain the dimensional stability of the obtained composite sheet when the resin integrated layer is formed.

In the method of the present invention, the thermoplastic polymer material used for forming the resin matrix layer has flexibility, and at least one kind of flexible natural and synthetic rubber and synthetic resin is used. It consists of Examples of the flexible synthetic resin include polyethylene, polypropylene, polyvinyl chloride, polystyrene, polyvinyl acetate, polybutene, polyacrylic acid ester, polyvinyl butyral, polyvinylidene chloride, polyacrylonitrile, ABS resin, acrylonitrile-styrene resin, ester-acetic acid. Vinyl resin, ionomer resin, fluorinated polyethylene, acetal resin, chlorinated polyether resin,
Polypropylene oxide, polyester, polyamide,
Examples of the thermoplastic resin include polyimide, polycarbonate, polyphenylene oxide, and polysulfone. Further, as synthetic rubber, diene rubber such as styrene-butadiene copolymer, olefin rubber such as butyl rubber, fluorine-containing rubber such as fluorinated acrylate rubber,
Rubbers such as ether / thioether rubber, urethane rubber, silicone rubber, and chlorosulfonated polyethylene can be used.

In the method of the present invention, the resin matrix layer is formed by applying a resin liquid containing the above-mentioned polymer material as a main component on the release surface of the heat-resistant release sheet and solidifying (gelling,
Or dried).

In the method of the present invention, a resin solution containing a polymer material having thermoplasticity as a main component is applied on the release surface of the heat resistant release sheet to form a resin application layer, and the resin application layer is formed on the resin solution application layer. Sprinkle conductive short fibers on. The spread conductive short fibers adhere to the resin liquid coating layer and are deposited thereon to form a conductive short fiber spread deposition layer.

Next, in the method (1) of the present invention, the resin liquid coating layer is solidified to form a resin matrix layer,
The conductive short fiber sprinkling deposited layer and the resin matrix layer carrying it are subjected to a pressure treatment, whereby the conductive short fiber sprinkling deposited layer is embedded in at least the surface layer portion of the resin matrix layer. Thus, a conductive fiber-resin integrated layer is formed, and a sheet-shaped substrate containing at least one fiber cloth is laminated and bound on at least one surface of the conductive fiber-resin integrated layer. In addition, in the method (2) of the present invention, a sheet-like substrate containing at least one fiber cloth is laminated on the conductive short fiber sprinkling deposited layer, and the resin liquid is added before or after the laminating operation. The coating layer is solidified to form a resin matrix layer, and the laminated body is subjected to a pressure treatment, whereby the conductive short fiber spattering deposition layer is embedded in at least the surface layer portion of the resin matrix layer, and the conductivity is improved. A fiber-resin integrated layer is formed and the sheet-shaped substrate and the conductive fiber-resin integrated layer are bound together.

Next, in each of the methods (1) and (2) of the present invention, the heat-resistant release sheet is peeled from the resin matrix layer before or after the pressure treatment, whereby a high electromagnetic wave shield is obtained. A composite sheet is obtained.

In the method of the present invention, a spatter-deposited layered body of a predetermined amount of conductive short fibers is embedded in at least one surface-side surface layer portion of the resin matrix layer formed on the release surface of the heat-resistant release sheet, whereby , A conductive fiber-resin integrated layer is formed. In the formation of such an electroconductive fiber-resin integrated layer, the electroconductive short fibers are distributed at a high density by forming a spatter-deposited layered body only on the surface layer portion of at least one surface of the resin matrix layer, and the remaining portion of the resin matrix layer remains. The conductive short fibers may not be substantially distributed in the portion, or the conductive short fibers may be distributed at a high density over substantially the entire volume of the resin matrix layer. Good.

The conductive short fibers used in the method of the present invention are:
Conductive metal fiber (for example, copper fiber, aluminum fiber,
Brass fiber, aluminum alloy fiber, stainless steel fiber, etc.), carbon fiber, graphite fiber, conductive composite fiber and the like. The conductive composite fiber is a core body made of organic or inorganic fibers, preferably organic short fibers, and a coating layer formed on the surface of the core body and made of a conductive material, particularly a conductive metal. It is composed. Such conductive conjugate fibers, since the organic fibers constituting the core have good flexibility and mechanical strength, do not break and powder even if repeatedly subjected to bending during use, Further, the conductive coating layer is less likely to peel or crack, and therefore has excellent durability.

The organic short fibers used as the core of the conductive composite fiber are known natural organic fibers, organic regenerated fibers,
It can be selected from organic semi-synthetic fiber and organic synthetic fiber, and one kind or a mixture of two or more kinds thereof can be used. As such organic natural fibers, for example, cotton, hemp, silk, wool, etc. can be used, as organic regenerated fibers viscose rayon, cupra, etc., and as semi-synthetic fibers cellulose di- and triacetate fibers, etc. Can be used. Further, as the organic synthetic fibers, polyamide fibers such as nylon 6 and nylon 66, polyester fibers such as polyethylene terephthalate fibers, polyvinyl alcohol fibers such as vinylon, polyvinyl chloride fibers, polyvinylidene chloride fibers, Organic fibers such as polyacrylic fibers, polyolefin fibers, fluorocarbon fibers and polyurethane fibers can be used. Suitable for the method of the present invention include polyester fibers, polyamide fibers, and water-insoluble polyvinyl alcohol fibers. The thickness of the organic short fibers is not particularly limited, but generally 0.1 to 1
It is preferably in the range of 0 denier.

On the surface of the organic short fiber core as described above,
A conductive metal coating layer is formed. There is no particular limitation on the method of forming the conductive metal coating layer, and any one of a metal deposition method, an electroplating method, and an electroless plating method may be used. However, compatibility with short fibers, ease of process,
It is preferable to use the electroless plating method in consideration of processing conditions, costs, required equipment, and the like. The electroless plating process is
It can be carried out as follows. The organic short fibers are subjected to the required pre-plating treatment, for example, degreasing cleaning with an alkaline cleaning solution and cleaning with an acid cleaning solution containing hydrochloric acid, sulfuric acid, or phosphoric acid, and then a sensitization treatment with a stannous chloride aqueous solution. , And a catalytic treatment with an aqueous palladium chloride solution. At this time, depending on the type of the organic short fiber, for example, in the case of polyamide fiber, wool, or silk, after the above-described catalyzing treatment, a reducing agent treatment is performed, or a catalyst using a palladium chloride treatment solution containing a silane coupling agent. May be applied. The pretreated organic short fibers are subjected to an electroless plating treatment. The metal coating formed on the surface of the organic short fiber core is generally made of copper, nickel, or a nickel alloy, but in addition,
Cobalt, silver, gold, etc. may be used, and two or more layers of different metals may be laminated.

Next, an example of the step of forming the nickel coating layer will be described. 100 g of organic short fibers having a predetermined length are treated in a 5% by weight caustic soda aqueous solution at a predetermined temperature, for example 50 ° C., for a predetermined time, for example 10 minutes, while gently stirring. After the treatment, the short fibers are separated from the treatment liquid by filtration, washed with water, and treated, for example, in a 1% by weight hydrochloric acid aqueous solution at a predetermined temperature (for example, room temperature) with stirring for a predetermined time (for example, 2 minutes). A solution of stannous chloride in hydrochloric acid is added so as to have a predetermined concentration, for example, 1 ml / l, and treated for a predetermined time (for example, 2 minutes). The treated organic short fibers are filtered out of the treatment liquid, washed with water, and then to a predetermined concentration, for example 1 g.
The mixture is sensitized at a predetermined temperature (for example, normal temperature) for a predetermined time (for example, 5 minutes) in a 1 / l hydrochloric acid aqueous solution with good stirring, and then filtered.

10 ml of a palladium chloride / hydrochloric acid solution having a predetermined concentration, for example, 0.1 g / l, was added to the filtered organic short fibers.
While stirring with an aqueous solution containing 990 ml of 10 ml / l hydrochloric acid, an activation (catalyzing) treatment is performed at a predetermined temperature (for example, room temperature) for a predetermined time (for example, 5 minutes). The treated organic short fibers are separated by filtration, and an electroless nickel plating solution having a predetermined composition (for example, the following composition) is used: Nickel sulfate 25 g / l Sodium hypophosphite 25 g / l Sodium citrate 30 g / l Sodium acetate 15 g / L pH (adjusted with acid or alkali) 4.5 to 5.5 with stirring at a predetermined temperature (generally 80 to 9)
5 ° C). Then, a conductive short fiber having a conductive nickel coating layer is obtained. The conductive short fibers thus obtained are covered with a conductive metal coating not only at the periphery but also at both end cross-sections, and exhibit good conductivity when dispersed in a matrix.

Table 1 shows an example of the performance of the conductive short fibers having the metal coating layer.

[Table 1]

[Note] Metallization rate: Electroless plated short fibers were put into an aqueous solution of sulfuric acid, and the amount of nickel dissolved therein was measured by IC.
Quantitative analysis by P and defined as the value obtained by the following formula. Metallization rate (%) = [measured value of the amount of eluted nickel (mg)] /
[Weight of collected sample (mg)] × 100 Calculation of density = The density of the metallized short fibers was calculated by the following formula.

(Equation 1) In the formula, A = density of coated metal (g / cm ³ ), B = density of fiber (g / cm ³ ).

The thickness and length of the conductive short fibers used in the method of the present invention are not particularly limited, but in general, the thickness is preferably 1.0 to 50 μm, and the length thereof is It is preferably 0.5 to 5 mm, 0.8 to 3 mm
Is more preferable. The aspect ratio is preferably 10 to 5,000, and 15 to 30.
More preferably, it is 00. If the length of the conductive short fibers is less than 0.5 mm, the same behavior as powder is exhibited, and the efficiency of expressing conductivity decreases, and if the length is longer than 5 mm, it is difficult to uniformly spread and deposit. become.

In the method of the present invention, the amount of the electrically conductive short fibers to be incorporated with the resin matrix layer can be arbitrarily set according to the purpose of the sheet material, and the obtained electrically conductive fiber-resin integrated layer. It is preferable to determine the resistance value of 10 ⁻² Ωcm or less. Generally, in the method of the present invention, the resin matrix layer has a thickness of 0.01 to 0.5.
Preferably, the conductive short fibers to be incorporated into the resin matrix layer have a spread amount (total volume) of 10 to 250 cm ³ / m ² . The total volume content of the conductive short fibers in the conductive short fiber-containing portion of the conductive fiber-resin integrated layer is 10 to 50% by volume with respect to the volume of the portion of the conductive fiber-resin integrated layer. Is preferable, and it is more preferable that it is 15 to 25% by volume. If this volume content is less than 10%, the resulting composite sheet may have insufficient electromagnetic wave shielding properties, and if it exceeds 50%, the resistance of the conductive fiber-resin integrated layer may be reduced. There are disadvantages that the abrasion property is poor and the peel strength to the sheet-shaped substrate and / or the surface protective layer is insufficient.

In the method of the present invention, if necessary, a known conductive material such as a metal fiber, a metal-coated glass fiber, a metal flake, a metal powder, a carbon fiber may be added to the conductive short fiber.
Carbon black, antimony chloride powder, copper iodide powder and the like, and matrix modifying materials such as colorants, plasticizers, stabilizers and fillers may be contained in the resin matrix layer in appropriate amounts.

The method of the present invention may further include a step of forming a surface protective layer containing a polymer material having good flexibility as a main component on the conductive fiber-resin integrated layer. The surface protective layer can prevent the conductive short fibers from being exposed on the surface, suppress a decrease in the conductive effect, and protect the composite sheet surface from mechanical and chemical damage.
Further, a desired color, pattern, uneven pattern, stain resistance, waterproofness, oil resistance, weather resistance, transparency or opacity can be imparted to the surface protective layer. The polymer used for the surface protective layer is not particularly limited, but generally polyvinyl chloride (PVC), polyurethane, polyester, fluorine-containing polymer, silicone polymer, acrylic polymer, ethylene-
It can be selected from thermoplastic resins such as vinyl acetate copolymers, chlorosulfonated polyethylene, and rubbery polymers such as synthetic and natural rubber. The thickness and weight of the surface protective layer are not particularly limited, but are generally 0.05 to 0.5 mm and 50, respectively.
It is preferably about 500 g / m ² .

FIG. 1 shows a sectional explanatory view of one embodiment of the composite sheet obtained by the method of the present invention. In FIG. 1, a conductive fiber-resin integrated layer 2 is formed on a sheet-like substrate 1, and in the surface layer portion 2a of this integrated layer 2, conductive short fibers form a spatter-deposited layered body. Highly distributed in the resin matrix layer, and the other portion 2b
Conductive short fibers are not substantially buried and distributed. The surface layer portion 2a in which the conductive short fibers are distributed at a high density has good conductivity, and therefore the composite sheet as a whole exhibits excellent electromagnetic wave shielding properties. The conductive fiber-resin integrated layer 2 may be substantially composed of only the portions 2a in which the conductive short fibers are densely distributed.
The conductive fiber-resin integrated layer 2 may be bonded so that the conductive fiber high density portion 2a is directly bonded to the sheet-shaped substrate 1. Further, the surface protective layer 3 may be bound on the conductive fiber-resin integrated layer 2.

In FIG. 2, the conductive fiber-resin integrated layer 2 is composed of a resin matrix layer and conductive short fibers distributed at a high density over the entire volume thereof,
A surface protective layer may be bound on the conductive fiber-resin integrated layer. The surface protective layer is preferably formed on at least one outermost surface of the composite sheet, as shown in FIGS. 1 and 2.

In the method (1) of the present invention, a resin liquid containing a thermoplastic polymer material for a resin matrix layer is applied on the release surface of a heat resistant release sheet, and conductive short fibers are sprinkled on the resin liquid application layer. The resin liquid coating layer is deposited and the conductive short fibers are sprinkled and deposited and then solidified to form a resin matrix layer, which is subjected to a pressure treatment to form a conductive fiber-resin integrated layer. Next, a sheet-shaped substrate is laminated on at least one surface of the conductive fiber-resin integrated layer, and these are bound by any means. The release sheet is released from the conductive fiber-resin integrated layer of the laminate before or after the above-mentioned lamination and binding operation.

Further, in the method (2) of the present invention, a sheet-like substrate is laminated on the conductive short fiber spattering deposition layer formed on the resin liquid coating layer, and the resin liquid coating is applied before or after this laminating operation. The layers are solidified to form a resin matrix layer, and the laminate is subjected to pressure treatment. By doing so, the conductive fiber-resin integrated layer is formed and the sheet-shaped substrate is bound at the same time. The heat-resistant release sheet can be peeled off before or after the pressure treatment.

The heat-resistant release sheet (film) used in the method of the present invention is conventionally used, for example, a release agent (for example, a silicone-containing low molecular weight compound or polymer, a fluorine-containing low molecular weight compound or polymer). , Or paraffin) coated plastic film (for example, polyester film), paper, cloth, or the like, or a plastic film having relatively low adhesion to the matrix resin.

In the method of the present invention, a resin matrix layer is formed on the release surface of the heat resistant release sheet. This resin matrix layer is obtained by applying a resin liquid on the release surface,
It is formed by solidifying this. Conductive short fibers are sprinkled on the resin liquid coating layer for forming a resin matrix layer, and this is adhered and deposited. In the method (1) of the present invention, the resin liquid coating layer formed as described above and carrying the conductive short fiber spattering deposition layer is solidified to form a resin matrix layer. A pressure treatment is applied to the matrix layer and the conductive short fiber sprinkling deposited layer on the matrix layer, and the conductive short fiber layer is press-fitted and buried in at least the surface layer portion of the resin matrix layer to integrate the two and A fiber-resin integrated layer is formed. In this case, it is preferable to perform the pressure treatment under a temperature condition in which the resin matrix layer exhibits thermoplasticity.

In the method (2) of the present invention, a sheet-like substrate containing at least one fiber cloth is laminated on the conductive short fiber spreading layer formed as described above, and thus, The formed laminate is subjected to the same pressure treatment as described above, thereby forming a conductive short fiber spattering deposited layer,
By embedding it in at least the surface layer portion of the resin matrix layer, a conductive fiber-resin integrated layer is formed and at the same time a sheet-like substrate having a fiber cloth is bound.

The thickness of the conductive fiber-resin integrated layer is
It is preferably 0.01 to 0.5 mm, and 0.1 to 0.5 mm.
More preferably, it is 0.2 mm. This conductive fiber
In the resin-integrated layer, the conductive short fibers form a spatter-deposited layered body and are distributed at the highest density in at least the surface layer portion in the resin matrix layer. In other words, the conductive short fibers are unevenly distributed at a high density at least in the surface layer portion of the resin matrix layer, and can exhibit high conductivity. Alternatively, when the resin matrix layer is thin, the buried conductive short fibers are distributed over the entire volume of the resin matrix layer while forming a scattered layered body.

In the method of the present invention, there is no particular limitation on the method for sprinkling and depositing the conductive short fibers, and for example, the gravity dropping method, the air blowing method, the placing method, the magnetic attraction method, etc. can be used. When the amount of the conductive short fibers deposited and deposited is excessive, a part of the conductive short fibers may be removed and collected before the pressure treatment. In the method of the present invention, when a pressure treatment is applied to the resin matrix layer carrying the conductive short fiber layer,
The electrically conductive short fibers are press-fitted, embedded or adhered into at least the surface layer portion of the resin matrix layer exhibiting plasticity. This pressing operation hardly breaks the conductive short fiber or peels off the plating on the surface, and combines with the resin matrix layer while maintaining its length and conductivity. It is. Further, the pressurizing operation may be performed at any temperature, for example, room temperature, but it is generally preferable to perform it under a temperature condition in which the resin matrix layer exhibits thermoplasticity.

In the method of the present invention, the heat-resistant release sheet is released from the resin matrix layer before or after the conductive fiber-resin integrated pressure treatment. This release sheet is peeled off, and on the exposed resin matrix layer surface, if necessary,
A surface protective layer containing a plastic polymer as a main component is formed.

The surface protective layer may be a flexible resin film or sheet adhered to the surface of the resin matrix layer, or a flexible resin liquid may be applied on the surface of the resin matrix layer. May be solidified.

In the methods (1) and (2) of the present invention,
A thermoplastic resin is used as a matrix, and in order to form a conductive layer in which conductive short fibers are sprinkled and deposited, a resin coating layer is formed on the release surface of the heat resistant release sheet, and a conductive layer is formed on top of it. Forming a sprinkling deposited layer of conductive short fibers, solidifying the resin coating liquid layer to form a resin matrix layer, and then forming a laminated body containing the sprinkling deposited layered body of conductive short fibers and a resin matrix layer. It is characterized in that the conductive short fiber spattered deposited layered body is pressed and embedded in the resin matrix layer of that shape under pressure to integrate them. By doing so, as compared with the conventional method, that is, the method of mixing and stirring the conductive short fibers in the matrix resin solution, and the method of kneading the matrix resin and the conductive short fibers with a calender, etc. It is characterized in that the fibers can be used uniformly and with a high content, without impairing the conductivity, and while keeping the fiber length at a desired length.
That is, breakage of the conductive fiber and peeling of the metal coating layer do not occur. Also, since the conductive fiber-resin integrated layer can be easily formed as a relatively thin layer at a desired portion of the high electromagnetic wave shielding composite sheet material as one or more arbitrary layers, it is very diverse. A product with a simple structure can be obtained. Further, by providing an arbitrary colored layer on the outermost surface of the composite sheet, a composite sheet having various appearances can be obtained.

In the conventional method, in order to keep the fiber length relatively long and to contain a large amount of conductive short fibers, a method of sandwiching or adhering conductive fiber-containing paper formed by, for example, a papermaking method is also available. However, in this case, it is necessary to mix the conductive short fibers with other fibers or pulp longer than the fiber length, and also to mix the binder. Mixing these other fibers or binders creates the disadvantage of reducing the conductivity of the conductive layer.
In the method of the present invention, it is not necessary to use another material which impairs the physical properties which are originally required, especially the conductivity. Also,
In the conventional papermaking method, in order to increase the paper strength for maintaining the process, by mixing the other materials as described above, the physical properties of the obtained conductive layer and other properties of this conductive layer and other There is a problem that the peel strength between the layers is significantly reduced. These problems occur not only in the papermaking method but also when, for example, a preformed nonwoven fabric is used. However, such a problem does not occur in the method of the present invention.

[0038]

The method of the present invention will be further described with reference to the following examples.

[0039]Example 1 (A)Preparation of sheet substrate Polyethylene terephthalate multifilament yarn
The following organizations consisting of:And has 180 g / m^TwoPlain woven fabric having a weight of
Was prepared and washed and dried by a conventional method. Next,
The following composition on the back of the fabric of P. V. C. 100 parts by weight D.I. O. P. 67 〃 Stabilizer 3 〃 Pigment 8 〃 Trichloroethylene 5 〃 Resin solution (having a viscosity of 10 poise at 25 ° C
Applied), heat dried at 100 ° C. for 3 minutes, and
Gel at 80 ℃ for 3 minutes, dry weight 70g / m ^TwoBehind
A face coating layer was formed. The weight of the obtained sheet substrate is 2
50g / m^TwoMet.

(B) Preparation of Conductive Short Fibers 100 g of polyethylene terephthalate short fibers having a length of 0.8 mm, a diameter of 15 μm and an aspect ratio of 53 were mixed with 5 g / l of γ-aminopropyltriethoxy. Treated with silane and dried, then 0.1 g /
It was put into an aqueous solution containing 10 ml of a palladium chloride / hydrochloric acid solution (1) and 10 ml / l of hydrochloric acid (990 ml) and, while being well stirred and dispersed, it was subjected to a catalytic treatment for 30 minutes at room temperature. It was then filtered off and dried in a drier at 110 ° C. The catalyzed polyester staple fibers, nickel plating bath having the following composition: Ingredients Amount (g / l) was added to nickel sulfate 25 sodium hypophosphite 30 30 in succinate 16 pH 4.5 to 5.0 malic acid Then, nickel plating treatment was performed at a liquid temperature of 60 to 95 ° C. The metallization rate of the obtained conductive polyester short fibers was 36%.

(C) Production of composite sheet (i) Resin liquid for resin coating layer The following composition: P. V. C. 100 parts by weight D.I. O. P. A resin liquid was prepared by adding trichlorethylene to a mixture containing 67 3 of stabilizer 3 3 and adjusting its viscosity to 30 poise at 25 ° C. (Ii) Composite sheet A heat-resistant polyester film having a thickness of 25 μm (trademark: Lumira-S-10, (Toray)) was uniformly coated with the above resin solution so that the dry weight was 60 g / m ^2. Apply the above conductive short fibers (fiber length 0.8 mm) on this,
An amount of 35 g / m ^2, that is, 13.9 cm ³ / m ² was sprinkled and deposited to form a conductive short fiber sprinkling deposited layer, which was subjected to infrared heating to dry and solidify the resin liquid layer. Next, using a direct pressure press, while heating the laminate to 175 ° C.,
This was subjected to a pressure treatment of 5 kg / cm ² for 2 minutes, and the above-mentioned sheet-like substrate was laminated thereon, and while being further heated to 175 ° C., a pressure treatment of 20 kg / cm ² was applied to this for 1 minute. ,
The heat resistant polyester film was peeled off from the obtained laminated product to obtain a composite sheet. The resulting composite sheet had a total weight of 345 g / m ² and a thickness of 0.35 mm, and had a smooth surface. The thickness of the conductive fiber-resin integrated layer of the obtained composite sheet was 0.08 mm,
The conductive short fiber content is 21.88% by volume, and the volume resistance value of the conductive fiber-resin integrated layer is 1.1 × 10 ⁻³ Ω-cm.
And had good performance. The volume resistance value was measured by the SRIS 2301 (1963), 3.1 term voltage-current method. Generally, the volume resistance value of the electromagnetic wave shielding sheet is preferably 10 ⁻² Ω · cm or less, and more preferably 10 ⁻³ Ω · cm or less.

Also, the sheet having the conductive fiber-resin integrated layer was peeled from the heat-resistant polyester film to form an independent sheet, which was laminated and adhered to the above-mentioned base cloth. .

Example 2 The same operation as in Example 1 was performed. However, after depositing the conductive short fiber cloth, the fiber cloth of Example 1 was laminated thereon, and infrared heating was applied thereto to dry and solidify the resin liquid, which was heated to 175 ° C. using a direct pressure type press machine. While 5kg / cm ²
Was applied for 2 minutes, and then a pressure treatment of 20 kg / cm ² was applied for 1 minute to embed and integrate the conductive short fibers in the resin layer. Next, the heat resistant substrate film was peeled off to obtain a composite sheet. The properties of the obtained composite sheet were almost the same as in Example 1 and were good.

[0044]

According to the method of the present invention, a relatively large amount of electrically conductive short fibers having a relatively long fiber length can be obtained without damaging the electrical conductivity thereof or breaking or pulverizing.
It is possible to form a conductive fiber-resin integrated layer by being united in a resin matrix layer, and thus it is possible to efficiently produce a useful composite sheet having a desired high electromagnetic wave shielding property. . In addition, by providing a surface protective layer, the conductive fiber-resin integrated layer is protected to prevent mechanical damage and falling off of the conductive short fiber, and to significantly improve the weather resistance, and to obtain a desired color, A high-electromagnetic-wave-shielding composite sheet having a beautiful appearance having a pattern, an uneven pattern, and the like was obtained, and the production of the composite sheet became possible. The composite sheet obtained by the method of the present invention contains a conductive short fiber-containing layer (conductive fiber-resin integrated layer) distributed at a relatively high density, and can exhibit extremely excellent electromagnetic wave shielding properties.

[Brief description of the drawings]

FIG. 1 is a cross-sectional explanatory view of one embodiment of a high electromagnetic wave shielding composite sheet obtained by the method of the present invention.

FIG. 2 is a cross-sectional explanatory view of another embodiment of the high electromagnetic wave shielding composite sheet obtained by the method of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Sheet-shaped substrate 2 ... Conductive fiber-resin integrated layer 2a ... Surface layer part in which conductive short fibers are distributed at high density 2b ... Part in which conductive short fibers are not substantially distributed 3 ... Surface protection layer

Claims (12)

[Claims] 1. A resin liquid coating layer is formed by coating a resin liquid containing a thermoplastic polymer material as a main component on a release surface of a heat resistant release sheet, and a conductive film is formed on the resin liquid coating layer. Of the conductive short fibers is sprinkled and deposited, and the resin liquid coating layer is solidified to form a resin matrix layer, and the conductive short fiber sprinkling deposited layer and the resin matrix layer supporting the conductive short fiber are subjected to a pressure treatment. , Thereby forming the conductive fiber-resin integrated layer by burying the conductive short fiber-spreading deposited layer in at least the surface layer portion of the resin matrix layer, and forming at least one surface of the conductive fiber-resin integrated layer. above,
Laminating and binding sheet-like substrates containing at least one fiber cloth, and peeling the heat-resistant release sheet from the conductive fiber-resin integrated layer before or after the laminating and binding operation. And a method for producing a high electromagnetic wave shielding composite sheet. 2. A resin liquid coating layer is formed by coating a resin liquid containing a thermoplastic polymer material as a main component on a release surface of a heat resistant release sheet, and a conductive layer is formed on the resin liquid coating layer. Short fibers are sprinkled and deposited, and a sheet-shaped substrate containing at least one fiber cloth is laminated on the conductive short fiber sprinkling deposited layer, and the resin liquid coating layer is formed before or after the laminating operation. A resin matrix layer is formed by solidification, and the laminate is subjected to a pressure treatment, thereby burying the conductive short fiber spattering deposition layer in at least the surface layer portion of the resin matrix layer to form a conductive fiber-resin. Forming an integrated layer, binding the sheet-shaped substrate and the conductive fiber-resin integrated layer, before or after the pressure treatment, the heat-resistant release sheet, from the resin matrix layer To peel off A method for producing a composite sheet with high electromagnetic wave shielding properties, comprising: 3. The sheet-like substrate containing the fiber cloth, wherein at least one surface of the fiber cloth is covered with a substrate coating layer containing a thermoplastic polymer material as a main component. Manufacturing method. 4. The total volume content of the conductive short fibers in the conductive fiber-resin integrated layer is 10 to 250 cm ³ / m ^2.
The manufacturing method according to any one of claims 1 and 2. 5. The manufacturing method according to claim 1, wherein the conductive fiber-resin integrated layer has a thickness of 0.01 to 0.5 mm. 6. The total volume content of the electroconductive short fibers in the electroconductive short fiber-containing portion in the electroconductive fiber-resin integrated layer is 10 to the volume of the electroconductive short fiber-containing portion. The manufacturing method according to claim 1 or 2, wherein the volume is 50% by volume. 7. The conductive short fibers are 1.0 to 50 μm.
1 or 2 having a thickness of 0.5 to 5 mm.
The production method described in 1. 8. The conductive short fibers are conductive metal fibers,
The manufacturing method according to claim 1 or 2, which is selected from carbon fibers, graphite fibers, and conductive composite fibers. 9. In the conductive fiber-resin integrated layer, the conductive short fibers are distributed at a high density only in the surface layer portion on one surface side of the resin matrix layer, and in the remaining portion of the resin matrix layer. The manufacturing method according to claim 1 or 2, wherein the conductive short fibers are not substantially distributed. 10. The conductive fiber-resin integrated layer, wherein the conductive short fibers are distributed at a high density over substantially the entire volume of the resin matrix layer.
Or the production method according to 2. 11. The manufacturing method according to claim 1, further comprising forming a surface protective layer containing a flexible polymer material as a main component on the conductive fiber-resin integrated layer. . 12. The manufacturing method according to claim 11, wherein the surface protective layer is formed on at least one outermost surface of the composite sheet.