CN112703281B - Non-woven fabrics for electromagnetic wave shielding materials and electromagnetic wave shielding materials - Google Patents

Abstract

The subject of this invention is providing the nonwoven fabric base material for electromagnetic wave shielding materials, and an electromagnetic wave shielding material which can express the excellent electromagnetic wave shielding property. A non-woven fabric for an electromagnetic wave shielding material comprising stretched polyester staple fibers and fibers having two or more different fiber diameters selected from stretched polyester staple fibers having a fiber diameter of 3 μm or more and less than 12 μm A wet-laid nonwoven fabric of unstretched polyester staple fibers with a diameter of 3 μm or more and 5 μm or less. A non-woven fabric for electromagnetic wave shielding materials, comprising stretched polyester staple fibers with a fiber diameter of less than 3 μm and unstretched polyester staple fibers with a fiber diameter of 3 μm or more and 5 μm or less, and having a weight per unit area of 7 g/ Wet-laid non-woven fabrics below m ² and with a density of 0.5-0.8 g/cm ³ . A non-woven fabric for an electromagnetic wave shielding material comprising stretched polyester staple fibers and unstretched polyester staple fibers having a melting point of not less than 220° C. and not more than 250° C., the nonwoven fabric having a peel strength (longitudinal direction) of More than 2.0N/m.

Description

Non-woven fabrics for electromagnetic wave shielding materials and electromagnetic wave shielding materials

technical field

The present invention relates to a nonwoven fabric for an electromagnetic wave shielding material and an electromagnetic wave shielding material which are excellent in conveyability of a mesh cloth and can express excellent electromagnetic wave shielding properties.

Background technique

Electronic devices generate electromagnetic waves. In addition, an electromagnetic wave shielding material is used in order not to leak electromagnetic waves to the outside of the electronic equipment, and to prevent electronic equipment from malfunctioning due to electromagnetic waves. Examples of the electromagnetic wave shielding material include metal plates, metal-containing paints, metal meshes, and foamed metals. Moreover, the electromagnetic wave shielding material which metal-plated the nonwoven fabric which consists of short polyester fibers is disclosed (for example, refer patent document 1 and 2).

Patent Document 1 discloses an electromagnetic wave shielding material in which a continuous metallic conductive layer is attached to the entire periphery and intersection of fibers of a woven, knitted or non-woven fabric of non-conductive fibers by a wet plating method. week. It is described that polyester fibers and polypropylene fibers are preferable as chemical fibers because they are excellent in the tensile strength and elongation properties of the substrate itself, and can prevent deterioration of properties in the plating pretreatment process.

Patent Document 2 discloses an electromagnetic wave shielding material. It is an electromagnetic wave shielding material obtained by applying a metal coating to a wet-laid nonwoven fabric. within the range of 10 to 30 μm.

With recent miniaturization, higher frequency, and higher performance of electronic equipment, thinner electromagnetic wave shielding materials with higher electromagnetic wave shielding properties are required. Specifically, an electromagnetic wave shielding material having a thickness of 15 μm or less and exhibiting excellent electromagnetic wave shielding properties in a wide frequency range of 100 MHz to 10 GHz is required.

Like Patent Documents 1 and 2, when metal coating treatment such as metal plating is applied to the nonwoven fabric, the roll to roll (Roll to Roll) with good productivity is processed, but there is generation of nonwoven fabric during transportation. Problems of wrinkling and poor transportability.

In addition, in the embodiment of Patent Document 2, an electromagnetic wave shielding material is disclosed, which includes stretched polyester fibers with a single fiber fineness of 0.1 dtex and unstretched binder fibers with a single fiber fineness of 0.2 dtex. The weight per unit area of the base paper of the woven fabric was 8 g/m ² , the weight per unit area of the electromagnetic wave shielding material was 19 g/m ² , and the thickness was 12 μm. However, there is a problem that the electromagnetic wave shielding material of Patent Document 2 cannot sufficiently ensure electromagnetic wave shielding properties as a thin electromagnetic wave shielding material is required. In addition, there may be a problem that the metal coating peels off.

In addition, in the electromagnetic wave shielding material obtained by metal-plating the non-woven fabric, polyester-based short fibers are required to be in close contact with the metal film formed by the metal-plating process. Alkali treatment is performed on polyester staple fibers.

Patent Document 1 describes that polyester fibers can prevent deterioration of properties in a pre-plating treatment step. Usually, however, the alkali treatment of nonwoven fabrics is a wet treatment, and fibers may fall off in a water tank, resulting in a significant decrease in workability. In addition, there may be a problem that a defect occurs in the metal plating process due to reattachment of the detached fibers to the nonwoven fabric.

prior art literature

patent documents

Patent Document 1: Japanese Publication No. 48-40800

Patent Document 2: Japanese Unexamined Patent Publication No. 2014-75485

Contents of the invention

The problem to be solved by the invention

A first object of the present invention is to provide a nonwoven fabric for an electromagnetic wave shielding material that is excellent in transportability and capable of expressing excellent electromagnetic wave shielding properties, and an electromagnetic wave shielding material using the nonwoven fabric for an electromagnetic wave shielding material.

A second object of the present invention is to provide a nonwoven fabric for an electromagnetic shielding material that is thin and exhibits excellent electromagnetic shielding properties, and whose metal coating does not easily peel off, and an electromagnetic shielding material using the nonwoven fabric for an electromagnetic shielding material.

The third object of the present invention is to provide a non-woven fabric for electromagnetic wave shielding materials with less fiber shedding and high strength in alkali treatment in the pre-plating treatment process for electromagnetic wave shielding materials and a nonwoven fabric for electromagnetic wave shielding materials using the same. Fabric electromagnetic wave shielding material.

means to solve the problem

The inventors of the present invention conducted intensive studies to solve the above-mentioned problems, and as a result, found the following invention.

<1> A non-woven fabric for electromagnetic wave shielding materials, which is a wet-laid non-woven fabric, characterized in that the wet-laid non-woven fabric contains fibers selected from stretched polyester staple fibers with a fiber diameter of 3 μm or more and less than 12 μm Two or more kinds of drawn polyester staple fibers having different diameters and undrawn polyester staple fibers having a fiber diameter of 3 μm or more and 5 μm or less are essential components.

<2> A non-woven fabric for electromagnetic wave shielding materials, which is a wet-laid non-woven fabric, characterized in that it contains stretched polyester short fibers with a fiber diameter of less than 3 μm and unstretched polyester staple fibers with a fiber diameter of 3 μm or more and 5 μm or less. The polyester staple fiber is an essential component, the weight per unit area is 7 g/m ² or less, and the density is 0.5-0.8 g/cm ³ .

<3> A non-woven fabric for electromagnetic wave shielding materials, which is a wet-laid non-woven fabric, characterized in that it contains stretched polyester staple fibers and unstretched polyester staple fibers with a melting point of 220°C to 250°C. Fiber, the peel strength (longitudinal direction) of this nonwoven fabric is 2.0 N/m or more.

<4> An electromagnetic wave shielding material characterized in that the nonwoven fabric for an electromagnetic wave shielding material according to any one of <1> to <3> above is subjected to a metal coating treatment.

<5> The electromagnetic wave shielding material according to the above <4>, wherein the metal coating treatment is one or more treatments selected from electroless metal plating treatment, electroplating treatment, metal vapor deposition treatment, and sputtering treatment .

<6> The electromagnetic wave shielding material according to <4> above, wherein the metal coating treatment includes sputtering nickel coating, copper coating plating and nickel coating coating in this order.

<7> The electromagnetic wave shielding material according to any one of <4> to <6>, wherein the thickness of the electromagnetic wave shielding material is 15 μm or less, and the surface resistance of the electromagnetic wave shielding material is 0.03 Ω/□ or less.

The effect of the invention

The first effect of the present invention is that it is possible to provide a nonwoven fabric for an electromagnetic wave shielding material that is excellent in transportability and can express excellent electromagnetic wave shielding properties, and an electromagnetic wave shielding material using the nonwoven fabric for an electromagnetic wave shielding material.

The second effect of the present invention is that it is possible to provide a nonwoven fabric for an electromagnetic shielding material that is thin, exhibits excellent electromagnetic wave shielding properties, and has a metal coating that does not easily peel off, and an electromagnetic shielding material using the nonwoven fabric for an electromagnetic shielding material.

The third effect of the present invention is that it is possible to provide a non-woven fabric for electromagnetic wave shielding material with less fiber shedding and high strength in alkali treatment in the pre-plating treatment process as electromagnetic wave shielding material, and a nonwoven fabric for electromagnetic wave shielding material using the same. electromagnetic wave shielding material.

Description of drawings

Fig. 1 is a schematic view showing the state of the nonwoven fabric for electromagnetic wave shielding materials when the peel strength is measured.

detailed description

Hereinafter, the nonwoven fabric for electromagnetic wave shielding materials of this invention, and an electromagnetic wave shielding material are demonstrated in detail.

-Nonwoven fabric for electromagnetic wave shielding material <1>-

The nonwoven fabric <1> for an electromagnetic wave shielding material of the present invention is characterized in that it contains two or more kinds of stretched fibers with different fiber diameters selected from stretched polyester staple fibers with a fiber diameter of 3 μm or more and less than 12 μm. A wet-laid nonwoven fabric in which polyester staple fibers and unstretched polyester staple fibers having a fiber diameter of 3 μm or more and 5 μm or less are essential components.

Usually, when the nonwoven fabric is transported in roll-to-roll processing, since the tension is applied in the MD (Machine Direction: Machine Direction), the nonwoven fabric is stretched, thereby causing wrinkles. Since the nonwoven fabric <1> for an electromagnetic wave shielding material of the present invention contains two or more kinds of stretched polyester staple fibers with different fiber diameters selected from stretched polyester staple fibers having a fiber diameter of 3 μm or more and less than 12 μm and undrawn polyester staple fibers with a fiber diameter of 3 μm or more and 5 μm or less are essential components, so the same 1 Such stretched polyester staple fibers are less likely to elongate than non-woven fabrics in which unstretched polyester staple fibers having a fiber diameter of 3 μm to 5 μm as an essential component are less prone to wrinkling during transportation. In addition, in the case of using a nonwoven fabric in which drawn polyester staple fibers have a fiber diameter as large as 12 μm or more, it is difficult to obtain a thin electromagnetic wave shielding material. The nonwoven fabric <1> for an electromagnetic wave shielding material of the present invention can achieve a thin and non-woven fabric by comprising stretched polyester staple fibers with a fiber diameter of less than 12 μm and undrawn polyester staple fibers with a fiber diameter of 3 μm or more and 5 μm or less. The effect of excellent transportability.

In general, electromagnetic wave shielding properties are realized by absorption reflection loss, reflection loss, and multiple reflection loss of electromagnetic waves. In the nonwoven fabric <1> for an electromagnetic wave shielding material of the present invention, by using two or more kinds of stretched polyester fibers having different fiber diameters selected from stretched polyester short fibers having a fiber diameter of 3 μm or more and less than 12 μm Since the fibers are short, electromagnetic waves penetrating into the electromagnetic wave shielding material are easily reflected repeatedly in the electromagnetic wave shielding material, and excellent electromagnetic wave shielding properties due to the improvement of multiple reflection loss can be obtained.

In the nonwoven fabric <1> for an electromagnetic wave shielding material of the present invention, the mass content ratio of stretched polyester staple fibers to unstretched polyester staple fibers is preferably 10:90 to 90:10, more preferably 20 :80 to 80:20, more preferably 30:70 to 70:30. If the content of the unstretched polyester short fibers is less than 10% by mass of the entire fibers constituting the wet-laid nonwoven fabric, the strength required as a nonwoven fabric for electromagnetic wave shielding materials may not be exhibited. On the other hand, when the content of the unstretched polyester staple fiber exceeds 90% by mass, uniformity may be impaired.

In the nonwoven fabric <1> for an electromagnetic shielding material of the present invention, stretched polyester staple fibers other than stretched polyester staple fibers having a fiber diameter of 3 μm or more and less than 12 μm may be used. In addition, unstretched polyester staple fibers other than unstretched polyester staple fibers having a fiber diameter of 3 μm or more and 5 μm or less may also be used. That is, drawn polyester staple fibers with a fiber diameter of less than 3 μm, drawn polyester staple fibers with a fiber diameter of 12 μm or more, undrawn polyester staple fibers with a fiber diameter of less than 3 μm, and polyester staple fibers with a fiber diameter of more than 5 μm can be used. Unstretched polyester staple fiber. These may be used alone, or two or more types of fibers having a fiber diameter may be used in combination.

In the nonwoven fabric <1> for an electromagnetic shielding material of the present invention, the stretched polyester staple fibers having a fiber diameter of 3 μm or more and less than 12 μm have a mass content equal to that of all the stretched polyester staple fibers contained. Among them, 1-100 mass % is preferable, and 3-100 mass % is more preferable. When the content of drawn polyester staple fibers with a fiber diameter of 3 μm or more and less than 12 μm is less than 1% by mass in all drawn polyester staple fibers, a thin electromagnetic shielding material with excellent conveyability may not be obtained .

In addition, in the nonwoven fabric <1> for an electromagnetic wave shielding material of the present invention, the unstretched polyester-based short fibers having a fiber diameter of 3 μm or more and 5 μm or less have a mass content ratio equal to that of the total unstretched polyester contained. Preferably it is 1-100 mass % in a short fiber, More preferably, it is 2-100 mass %. When the content of undrawn polyester staple fibers with a fiber diameter of 3 μm or more and 5 μm or less is less than 1% by mass, depending on the fiber diameter used in combination, the specific surface area may become small, making it difficult to exhibit excellent electromagnetic wave shielding properties. In addition, it is sometimes difficult to express the strength of a wet-laid nonwoven fabric.

The thickness of the nonwoven fabric <1> for an electromagnetic shielding material of the present invention is preferably 7 to 30 μm, more preferably 15 μm or less, for the purpose of use in electronic devices. The weight per unit area (weight per unit area) is preferably 5 to 30 g/m ² , more preferably 15 g/m ² or less. If the weight per unit area is less than 5 g/m ² , it will be difficult to obtain uniformity, and the effect of electromagnetic wave shielding property will easily vary.

-Non-woven fabrics for electromagnetic wave shielding materials<2>-

The nonwoven fabric <2> for an electromagnetic wave shielding material of the present invention is characterized in that it contains, as Essential ingredients, wet-laid non-woven fabrics with a weight per unit area of 7 g/m ² or less and a density of 0.5 to 0.8 g/cm ³ .

In general, in the metal coating treatment of wet-laid nonwoven fabrics, if the specific surface area (surface area per unit volume) of the fibers forming the wet-laid nonwoven fabric is small, the amount of metal attached per unit volume is small, and excellent performance may not be achieved. electromagnetic wave shielding. Since the nonwoven fabric <2> for an electromagnetic wave shielding material of the present invention contains, as essential components, drawn polyester staple fibers with a fiber diameter of less than 3 μm and undrawn polyester staple fibers with a fiber diameter of 3 μm or more and 5 μm or less It is a wet-laid non-woven fabric, so it can increase the specific surface area and exhibit excellent electromagnetic wave shielding properties. When the wet-laid nonwoven fabric contains only drawn polyester staple fibers with a fiber diameter of 3 μm or more and undrawn polyester staple fibers with a fiber diameter of more than 5 μm, excellent electromagnetic shielding properties cannot be exhibited. It should be noted that it is difficult to obtain undrawn polyester staple fibers with a fiber diameter of less than 3 μm. In addition, the fiber diameter of the drawn polyester staple fiber having a fiber diameter of less than 3 μm is preferably 0.1 μm or more. When the fiber diameter is less than 0.1 μm, strength may not be expressed.

In the nonwoven fabric <2> for an electromagnetic shielding material of the present invention, the mass content ratio of stretched polyester staple fibers to unstretched polyester staple fibers is preferably 20:80 to 80:20, more preferably 30 :70 to 70:30, more preferably 40:60 to 60:40. If the content of the unstretched polyester short fibers is less than 20% by mass of the entire fibers constituting the wet-laid nonwoven fabric, the strength required as a nonwoven fabric for electromagnetic wave shielding materials may not be exhibited. On the other hand, if the content of the unstretched polyester staple fiber exceeds 80% by mass, uniformity may be impaired.

In the nonwoven fabric <2> for an electromagnetic shielding material of the present invention, stretched polyester staple fibers with a fiber diameter of less than 3 μm and undrawn polyester staple fibers with a fiber diameter of 3 μm or more and 5 μm or less can also be used. other fibers. That is, drawn polyester staple fibers with a fiber diameter of 3 μm or more, undrawn polyester staple fibers with a fiber diameter of less than 3 μm, and undrawn polyester staple fibers with a fiber diameter of more than 5 μm can be used. These may be used alone, or two or more types of fibers having a fiber diameter may be used in combination.

In the nonwoven fabric <2> for an electromagnetic shielding material of the present invention, the content of drawn polyester staple fibers having a fiber diameter of less than 3 μm is preferably 1 to 100% by mass in all drawn polyester staple fibers , and more preferably 3 to 100% by mass. When the content of drawn polyester staple fibers with a fiber diameter of less than 3 μm is less than 1% by mass, depending on the fiber diameter used together, the specific surface area may become small, making it difficult to express excellent electromagnetic wave shielding properties.

In addition, in the nonwoven fabric <2> for an electromagnetic shielding material of the present invention, the content of unstretched polyester staple fibers having a fiber diameter of 3 μm or more and 5 μm or less is equal to or greater than that of all unstretched polyester staple fibers. 1 to 100% by mass is preferable, and 2 to 100% by mass is more preferable. When the content of undrawn polyester staple fibers with a fiber diameter of 3 μm or more and 5 μm or less is less than 1% by mass, depending on the fiber diameter used in combination, the specific surface area may become small and it may be difficult to exhibit excellent electromagnetic wave shielding properties, Or it may be difficult to express the strength of the excellent wet-laid nonwoven fabric.

In the nonwoven fabric <2> for an electromagnetic shielding material of the present invention, the basis weight of the wet-laid nonwoven fabric is 7 g/m ² or less, more preferably 5 g/m ² or less, further preferably 4 g/m ² or less. If the weight per unit area exceeds 7 g/m ² , it may become thicker after the metal coating treatment, resulting in a thickness of the electromagnetic wave shielding material exceeding 15 μm, which may not be used for electronic equipment, communication equipment, electric appliances, etc. In addition, the basis weight of the wet-laid nonwoven fabric is preferably 3 g/m ² or more. In addition, the weight per unit area was measured by the method described in JISP8124:2011.

In the nonwoven fabric <2> for electromagnetic shielding materials of the present invention, the density of the wet-laid nonwoven fabric is 0.5 to 0.8 g/cm ³ , more preferably 0.55 to 0.65 g/cm ³ . Since the specific surface area increases when the density is 0.8 g/cm ³ or less, the number of metal coatings formed by the metal coating treatment increases, and the electromagnetic wave shielding property improves. In addition, the metal coating is difficult to peel off. In addition, if the density is 0.5 g/cm ³ or more, the strength of the wet-laid nonwoven fabric becomes high, and troubles are less likely to occur during metal coating treatment, and the metal coating is less likely to peel off. In addition, density was measured by the method described in JISP8118:2014.

-Non-woven fabrics for electromagnetic wave shielding materials<3>-

The nonwoven fabric <3> for an electromagnetic shielding material of the present invention is a wet-laid nonwoven fabric containing stretched polyester staple fibers and unstretched polyester staple fibers having a melting point of 220°C to 250°C. And the peeling strength (longitudinal direction) of the nonwoven fabric <3> for electromagnetic wave shielding materials of this invention is 2.0 N/m or more.

In the nonwoven fabric for electromagnetic wave shielding material <3> of the present invention, the peel strength (longitudinal direction) of the nonwoven fabric for electromagnetic wave shielding material is 2.0 N/m or more, more preferably 2.5 N/m or more, still more preferably 3.0 N /m above. When the peeling strength (longitudinal direction) is less than 2.0 N/m, the bonding between the fibers is too weak, so that during the alkali treatment, the fibers will fall off from the nonwoven fabric for electromagnetic wave shielding material more, and the accumulation of fibers on the conveying roller will occur. etc. Therefore, there arises a problem that periodic cleaning is required to cause a decrease in operability, and a problem that a defect occurs in the metal plating process due to reattachment of the shed fibers to the nonwoven fabric for electromagnetic wave shielding material. In the nonwoven fabric for electromagnetic wave shielding material <3> of the present invention, the peel strength (machine direction) of the nonwoven fabric for electromagnetic wave shielding material is preferably 10.0 N/m or less. If it exceeds 10.0 N/m, fusion of the nonwoven fabric for electromagnetic wave shielding materials may proceed excessively, and the surface of the nonwoven fabric for electromagnetic wave shielding materials may be formed into a film, and the form may not be maintained.

In the nonwoven fabric <3> for an electromagnetic shielding material of the present invention, the fiber diameter of the stretched polyester staple fibers is preferably 1 to 10 μm, more preferably 2 to 8 μm. As the drawn polyester staple fiber, two or more kinds of drawn polyester staple fibers having different fiber diameters may be included. When the fiber diameter of the drawn polyester staple fiber is 10 μm or less, it is easy to provide a thin electromagnetic wave shielding material. In addition, it is preferable that the stretched polyester staple fibers preferably contain polyester staple fibers having a fiber diameter of 3 μm or less as an essential component. By including short polyester fibers with a fiber diameter of 3 μm or less, electromagnetic wave shielding properties are further improved.

In the nonwoven fabric <3> for an electromagnetic shielding material of the present invention, the fiber diameter of the unstretched polyester staple fibers is preferably 1 to 8 μm, more preferably 3 to 5 μm. When the fiber diameter is within this range, it is easy to provide a thin electromagnetic wave shielding material while improving the strength of the wet-laid nonwoven fabric. As the unstretched polyester staple fiber, two or more kinds of unstretched polyester staple fibers having different fiber diameters may be included.

In the nonwoven fabric <3> for an electromagnetic shielding material of the present invention, the mass content ratio of the stretched polyester staple fibers to the unstretched polyester staple fibers is preferably 20:80 to 80:20. If the content of the unstretched polyester short fibers is less than 20% by mass of the entire fibers constituting the wet-laid nonwoven fabric, the strength required as a nonwoven fabric for electromagnetic wave shielding materials may not be exhibited. On the other hand, if the content of the unstretched polyester staple fiber exceeds 80% by mass, uniformity may be impaired. In addition, in order to improve electromagnetic shielding properties, the content of drawn polyester staple fibers having a fiber diameter of 3 μm or less is more preferably 5 to 80% by mass of the entire fibers constituting the wet-laid nonwoven fabric. In the nonwoven fabric <3> for an electromagnetic wave shielding material of the present invention, the most preferable fiber composition is stretched polyester with 20 to 80% by mass of unstretched polyester short fibers and a fiber diameter of more than 3 μm and 10 μm or less. 0 to 75% by mass of staple fibers, and 5 to 80% by mass of drawn polyester staple fibers having a fiber diameter of 3 μm or less.

The thickness of the nonwoven fabric <3> for an electromagnetic shielding material of the present invention is preferably 5 to 30 μm, more preferably 20 μm or less, for the purpose of use in electronic devices. The weight per unit area (weight per unit area) is preferably 3 to 30 g/m ² , more preferably 15 g/m ² or less. If the weight per unit area is less than 3 g/m ² , it will be difficult to obtain uniformity, the effect of electromagnetic wave shielding property will easily vary, and it will be difficult to maintain the strength of the nonwoven fabric for electromagnetic wave shielding material itself, resulting in difficulty in workability.

-Polyester staple fiber-

In the present invention, the stretched polyester staple fibers are not easily melted or softened even by heat calendering, and are the main fibers forming the skeleton of the wet-laid nonwoven fabric.

In the present invention, the unstretched polyester staple fibers are melted or softened by heat calendering, and function as binder fibers that increase the strength of the wet-laid nonwoven fabric. The melting point of the unstretched polyester staple fiber is preferably 220°C to 250°C. In the nonwoven fabric <3> for an electromagnetic shielding material of the present invention, the melting point of the unstretched short polyester fibers is 220° C. or higher and 250° C. or lower. When the melting point of the unstretched polyester staple fiber is lower than 220° C., the wet-laid nonwoven fabric may stick to the hot roll during the heat calendering process, and it may not be possible to form a sheet. When the temperature exceeds 250° C., the fibers may not be bonded and the strength of the wet-laid nonwoven fabric may not be exhibited. The melting point of the unstretched polyester staple fiber is more preferably 225°C or higher and 250°C or lower.

The melting point of the undrawn polyester staple fiber is the peak temperature when the temperature is raised from 25° C. to 300° C. at a heating rate of 10° C./min in a nitrogen atmosphere using a differential scanning calorimeter.

In addition, in the Example of this invention, the fiber diameter of a polyester staple fiber describes the fiber diameter before manufacture of a nonwoven fabric. The fiber diameter of the polyester staple fiber can be measured in the form of the following diameter, that is, by taking a 3000-fold enlarged photo of the cross-section of the wet non-woven fabric or electromagnetic wave shielding material with a microscope, the cross-sectional area of the polyester staple fiber is measured, and the fiber In this case, it is preferable to obtain the arithmetic mean value of 10 or more fibers having substantially the same cross-sectional area.

The fiber length of the polyester staple fiber is preferably 1 to 20 mm, more preferably 1 to 10 mm, and still more preferably 2 to 8 mm. When the fiber length of polyester staple fiber is less than 1 mm, it may be difficult to express the intensity|strength required as a wet-laid nonwoven fabric. When the fiber length of polyester staple fiber exceeds 20 mm, uniformity may be impaired.

In the present invention, examples of polyester include polyethylene terephthalate, polyethylene isophthalate, polypropylene terephthalate, polyethylene naphthalate, polyethylene Butylene terephthalate, polybutylene naphthalate, etc. Polyester-based short fibers are preferable in view of the ability to reduce the fiber diameter for reducing the thickness of the electromagnetic wave shield, ease of papermaking, and dimensional stability during wet alkali treatment in the plating process. The polyester-based staple fibers may be used alone or in combination of two or more.

-Wet-laid non-woven fabric-

As a method of forming fibers into a sheet, various production methods such as spunbond method, melt blown method, electrospinning method, and wet method can be mentioned. The nonwoven fabric for electromagnetic wave shielding material of the present invention is produced by the wet method (sheet paper method) formed into a sheet-like wet-laid non-woven fabric, which is a non-woven fabric with excellent strength and high uniformity. Moreover, various methods, such as a chemical bonding method and a thermal welding method, are mentioned as a method of joining between fibers. Among them, the thermal fusion method is preferable from the viewpoint of excellent durability and strength, and a smooth surface of the nonwoven fabric.

As the thermal welding method in the wet method, heat drying can be performed when the sheet obtained by the papermaking method is heat-dried with a dryer used after papermaking, such as a multi-cylinder dryer, a Yankee dryer, or a hot air dryer. The method of welding. In addition, a method of performing thermal fusion by thermal calendering treatment by a thermal calendering device having roll combinations such as metal heated roll/metal heated roll, metal heated roll/elastic roll, and metal heated roll/cotton roll can also be used. . By thermal drying or thermal calendering, the binder component is thermally melted to generate thermal fusion.

In addition, the conditions of hot rolling are exemplified below, but are not limited thereto. The temperature of the hot roll in the hot calendering treatment is preferably 200°C or higher and 215°C or lower. When the temperature of the heat roll is lower than 200° C., there may be a problem that the fibers do not adhere to each other and the strength cannot be expressed. In addition, conversely, when the temperature of the heat roll exceeds 215° C., the wet-laid nonwoven fabric may stick to the heat roll and fail to form a sheet. The temperature of the heat roller is more preferably 203°C or higher and 210°C or lower, still more preferably 205°C or higher. It should be noted that in the nonwoven fabric for electromagnetic wave shielding material <3> of the present invention, in order to increase the peel strength of the nonwoven fabric for electromagnetic wave shielding material, it is preferable to use a pair of heating rollers with a temperature of 200° C. or higher and 215° C. or lower. A wet-laid nonwoven fabric of stretched polyester staple fibers and unstretched polyester staple fibers having a melting point of 220° C. to 250° C. is subjected to heat calendering. A more preferable temperature of the heat roller is 203°C or higher and 210°C or lower.

In order to express strength, the pressure (linear pressure) in the heat rolling treatment is preferably 50 to 250 kN/m, more preferably 80 to 150 kN/m. In the case of a pressure of less than 50kN/m, the smoothness of the surface may be impaired, and the thickness may not be thinned unless the speed is reduced. In the case where the pressure exceeds 250 kN/m, there is a possibility that the sheet cannot withstand the pressure and breaks. The processing speed of hot rolling is preferably 1 to 300 m/min. Work efficiency becomes favorable by making a processing speed 1 m/min or more. By setting the processing speed at 300 m/min or less, the heat is conducted to the wet-laid nonwoven fabric, and the practical effect of thermal welding is easily obtained. There is no particular limitation on the number of nip times for hot calendering as long as heat can be transferred to the wet-laid nonwoven fabric. In the combination of metal heating rollers/elastic rollers, more than two times can be used to conduct heat from the front and back of the wet-laid nonwoven fabric. .

-Electromagnetic wave shielding material-

The electromagnetic wave shielding material of the present invention is characterized in that the nonwoven fabric for electromagnetic wave shielding material of the present invention is subjected to a metal coating treatment. That is, the electromagnetic wave shielding material of this invention is characterized by including the nonwoven fabric for electromagnetic wave shielding materials of this invention, and a metal film.

In the present invention, examples of metal coating treatment include electroless metal plating treatment, electroplating treatment, metal vapor deposition treatment, sputtering treatment and the like. One or more treatments selected from these treatments may be performed. Among them, it is preferable to perform plating treatment after sputtering treatment from the viewpoints that thinning is possible, the surface resistance value tends to be lowered, and the metal film is less likely to peel off. The above-mentioned metal film may be one layer, or may be a multilayer of two or more layers.

Gold, silver, copper, zinc, aluminum, nickel, tin, or their alloys etc. are mentioned as a kind of metal used for a metal coating process. Among them, one or more metals selected from gold, silver, copper, aluminum, nickel, and tin are preferable, and copper and nickel are more preferable in consideration of electrical conductivity and manufacturing cost.

In the present invention, the metal coating treatment more preferably includes, in this order, a treatment for forming a nickel coating by sputtering, a treatment for forming a copper coating by electroplating, and a treatment for forming a nickel coating by electroplating. First, a metal coating is formed on a wet-laid nonwoven fabric by sputtering. The metal in the sputtering treatment is preferably nickel. After sputtering, metal coatings are laminated by electroplating. The metal to be plated is preferably copper. In addition, in order to prevent rust, a metal having good rust resistance such as nickel may be laminated on the outer layer. This lamination method is preferably a method utilizing electroplating.

The thickness of the electromagnetic wave shielding material of the present invention is preferably 15 μm or less, more preferably 13 μm or less, and still more preferably 12 μm or less. If the thickness of the electromagnetic wave shielding material exceeds 15 μm, it may not be used in electronic equipment, communication equipment, electric appliances, and the like. In addition, the thickness of the electromagnetic wave shielding material is preferably 7 μm or more. In addition, thickness was measured by the method described in JISP8118:2014.

In addition, the surface resistance value of the electromagnetic wave shielding material of the present invention is preferably 0.03Ω/□ or less, more preferably 0.01Ω/□ or less. Moreover, it is preferable that the electromagnetic wave shielding property in 40 MHz - 18 GHz is 50 dB or more. Moreover, it is preferable that the electromagnetic wave shielding property in 40 MHz - 10 GHz is 60 dB or more. Moreover, it is preferable that the electromagnetic wave shielding property in 40 MHz - 1 GHz is 70 dB or more.

Example

Hereinafter, although an Example is given and this invention is demonstrated, this invention is not limited to these Examples at all. In addition, in an Example, unless otherwise specified, % and a part are all based on mass.

"Examples of the nonwoven fabric <1> for electromagnetic wave shielding material of the present invention"

[Example 1]

Using a pulper, 30 parts by mass of stretched polyethylene terephthalate (PET) short fibers with a fineness of 0.3 dtex (fiber diameter of 5.3 μm) and a fiber length of 3 mm and a fineness of 0.6 dtex (fiber diameter of 7.4 μm), 30 parts by mass of stretched PET staple fibers with a fiber length of 5 mm and 40 parts by mass of unstretched PET staple fibers with a fineness of 0.2 dtex (fiber diameter 4.3 μm) and a fiber length of 3 mm were dispersed in water to prepare a uniform concentration of 1 mass %. paste for papermaking. The papermaking slurry was prepared by a wet method using an inclined paper machine equipped with a papermaking net with an air permeability of 275 cm ³ /cm ² /sec and a texture [on the net: plain weave, on the bottom net: heavy flat weave]. The drum dryer at 135°C thermally welds the unstretched PET-based short fibers to develop strength, and produces a wet-laid non-woven fabric with a weight per unit area of 10 g/m ² . In addition, using a 1-clamp hot calendering device including a dielectric heating jacket roll (metal heating roll) and an elastic roll, under the conditions of a hot roll temperature of 200°C, a linear pressure of 100kN/m, and a processing speed of 30m/min. This wet-laid nonwoven fabric was subjected to heat calendering treatment to produce a nonwoven fabric for electromagnetic wave shielding materials with a thickness of 15 μm.

[Example 2]

In addition to 10 parts by mass of drawn PET-based staple fiber with a fineness of 0.3 dtex (fiber diameter 5.3 μm) and a fiber length of 3 mm, and 50 parts by mass of drawn PET-based staple fiber with a fineness of 0.6 dtex (fiber diameter of 7.4 μm) and a fiber length of 5 mm , and fineness 0.2dtex (fiber diameter 4.3 μm), except 40 parts by mass of unstretched PET-based staple fibers with a fiber length of 3 mm, the same operation as in Example 1 was performed to produce a nonwoven fabric for electromagnetic wave shielding materials with a thickness of 17 μm.

[Example 3]

In addition to 50 parts by mass of drawn PET staple fiber with a fineness of 0.3 dtex (fiber diameter 5.3 μm) and a fiber length of 3 mm, and 10 parts by mass of drawn PET staple fiber with a fineness of 0.6 dtex (fiber diameter of 7.4 μm) and a fiber length of 5 mm , and fineness 0.2dtex (fiber diameter 4.3 μm), except 40 parts by mass of unstretched PET-based staple fibers with a fiber length of 3 mm, the same operation as in Example 1 was performed to produce a nonwoven fabric for electromagnetic wave shielding materials with a thickness of 16 μm.

[Example 4]

In addition to 45 parts by mass of stretched PET-based staple fibers with a fineness of 0.3 dtex (fiber diameter 5.3 μm) and a fiber length of 3 mm, and 45 parts by mass of drawn PET-based staple fibers with a fineness of 0.6 dtex (fiber diameter 7.4 μm) and a fiber length of 5 mm , and fineness 0.2dtex (fiber diameter 4.3 μm), fiber length 3mm except 10 parts by mass of unstretched PET-based short fibers, the same operation as in Example 1, to produce a thickness of 16 μm electromagnetic wave shielding nonwoven fabric.

[Example 5]

In addition to 30 parts by mass of stretched PET-based staple fibers with a fineness of 0.1 dtex (fiber diameter: 3.0 μm) and a fiber length of 3 mm, and 30 parts by mass of drawn PET-based staple fibers with a fineness of 0.6 dtex (fiber diameter: 7.4 μm) and a fiber length of 5 mm , and fineness 0.2dtex (fiber diameter 4.3 μm), except 40 parts by mass of unstretched PET-based staple fibers with a fiber length of 3 mm, the same operation as in Example 1 was performed to produce a nonwoven fabric for electromagnetic wave shielding materials with a thickness of 14 μm.

[Example 6]

In addition to 10 parts by mass of stretched PET-based staple fibers with a fineness of 0.1 dtex (fiber diameter: 3.0 μm) and a fiber length of 3 mm, and 30 parts by mass of drawn PET-based staple fibers with a fineness of 0.3 dtex (fiber diameter: 5.3 μm) and a fiber length of 3 mm , 30 parts by mass of stretched PET staple fibers with a fineness of 0.6 dtex (fiber diameter 7.4 μm) and a fiber length of 5 mm, and 30 parts by mass of undrawn PET staple fibers of a fineness of 0.2 dtex (fiber diameter 4.3 μm) and a fiber length of 3 mm Other than that, it carried out similarly to Example 1, and produced the nonwoven fabric for electromagnetic wave shielding materials of thickness 14 micrometers.

[Example 7]

In addition to 30 parts by mass of stretched PET-based staple fibers with a fineness of 0.3 dtex (fiber diameter 5.3 μm) and a fiber length of 3 mm, and 30 parts by mass of drawn PET-based staple fibers with a fineness of 0.6 dtex (fiber diameter 7.4 μm) and a fiber length of 5 mm , 10 parts by mass of stretched PET-based staple fibers with a fineness of 1.7 dtex (fiber diameter of 12.0 μm) and a fiber length of 5 mm, and 30 parts by mass of undrawn PET-based staple fibers of a fineness of 0.2 dtex (fiber diameter of 4.3 μm) and a fiber length of 3 mm Other than that, it carried out similarly to Example 1, and produced the nonwoven fabric for electromagnetic wave shielding materials of thickness 16 micrometers.

[Example 8]

In addition to 10 parts by mass of stretched PET-based staple fibers with a fineness of 0.06 dtex (fiber diameter: 2.4 μm) and a fiber length of 3 mm, and 30 parts by mass of drawn PET-based staple fibers with a fineness of 0.3 dtex (fiber diameter: 5.3 μm) and a fiber length of 3 mm , 30 parts by mass of stretched PET staple fibers with a fineness of 0.6 dtex (fiber diameter 7.4 μm) and a fiber length of 5 mm, and 30 parts by mass of undrawn PET staple fibers of a fineness of 0.2 dtex (fiber diameter 4.3 μm) and a fiber length of 3 mm Other than that, it carried out similarly to Example 1, and produced the nonwoven fabric for electromagnetic wave shielding materials of thickness 14 micrometers.

[Example 9]

In addition to 30 parts by mass of stretched PET-based staple fibers with a fineness of 0.3 dtex (fiber diameter 5.3 μm) and a fiber length of 3 mm, and 30 parts by mass of drawn PET-based staple fibers with a fineness of 0.6 dtex (fiber diameter 7.4 μm) and a fiber length of 5 mm , 30 parts by mass of undrawn PET-based staple fibers with a fineness of 0.2 dtex (fiber diameter: 4.3 μm) and a fiber length of 3 mm, and 10 parts by mass of undrawn PET-based staple fibers with a fineness of 1.2 dtex (fiber diameter: 10.5 μm) and a fiber length of 5 mm Except the parts, it carried out similarly to Example 1, and produced the nonwoven fabric for electromagnetic wave shielding materials of thickness 16 micrometers.

[Example 10]

In addition to 15 parts by mass of stretched PET-based staple fibers with a fineness of 0.3 dtex (fiber diameter 5.3 μm) and a fiber length of 3 mm, and 15 parts by mass of drawn PET-based staple fibers with a fineness of 0.6 dtex (fiber diameter 7.4 μm) and a fiber length of 5 mm , and fineness 0.2dtex (fiber diameter 4.3 μm), fiber length 3mm except 70 parts by mass of unstretched PET-based short fibers, the same operation as in Example 1, to produce a thickness of 14 μm electromagnetic wave shielding nonwoven fabric.

[Comparative example 1]

In addition to 30 parts by mass of stretched PET-based staple fibers with a fineness of 0.3 dtex (fiber diameter 5.3 μm) and a fiber length of 3 mm, and 30 parts by mass of drawn PET-based staple fibers with a fineness of 0.6 dtex (fiber diameter 7.4 μm) and a fiber length of 5 mm , and fineness 1.2dtex (fiber diameter 10.5 μm), except 40 parts by mass of unstretched PET-based staple fibers with a fiber length of 5 mm, the same operation as in Example 1 was performed to produce a nonwoven fabric for electromagnetic wave shielding materials with a thickness of 17 μm.

[Comparative example 2]

In addition to 60 parts by mass of stretched PET-based staple fibers with a fineness of 0.3 dtex (fiber diameter 5.3 μm) and a fiber length of 3 mm, and 40 parts by mass of undrawn PET-based staple fibers with a fineness of 0.2 dtex (fiber diameter 4.3 μm) and a fiber length of 3 mm Except for parts by mass, it carried out similarly to Example 1, and produced the nonwoven fabric for electromagnetic wave shielding materials of thickness 15 micrometers.

[Comparative example 3]

In addition to 30 parts by mass of stretched PET-based staple fibers with a fineness of 1.7 dtex (fiber diameter of 12.0 μm) and a fiber length of 5 mm, and 30 parts by mass of drawn PET-based staple fibers of a fineness of 3.3 dtex (fiber diameter of 17.5 μm) and a fiber length of 5 mm , and fineness 0.2dtex (fiber diameter 4.3 μm), except 40 parts by mass of unstretched PET-based staple fibers with a fiber length of 3 mm, the same operation as in Example 1 was performed to produce a nonwoven fabric for electromagnetic wave shielding materials with a thickness of 21 μm.

[Comparative example 4]

In addition to 60 parts by mass of stretched PET-based staple fibers with a fineness of 1.7 dtex (fiber diameter of 12.0 μm) and a fiber length of 5 mm, and 40 parts by mass of undrawn PET-based staple fibers of a fineness of 0.2 dtex (fiber diameter of 4.3 μm) and a fiber length of 3 mm Except for parts by mass, it carried out similarly to Example 1, and produced the nonwoven fabric for electromagnetic wave shielding materials of thickness 18 micrometers.

[Comparative Example 5]

In addition to 60 parts by mass of stretched PET-based staple fibers with a fineness of 0.1 dtex (fiber diameter: 3.0 μm) and a fiber length of 3 mm, and 40 parts by mass of undrawn PET-based staple fibers with a fineness of 0.2 dtex (fiber diameter: 4.3 μm) and a fiber length of 3 mm Except for parts by mass, it carried out similarly to Example 1, and produced the nonwoven fabric for electromagnetic wave shielding materials of thickness 15 micrometers.

The nonwoven fabrics for electromagnetic wave shielding materials produced in Examples and Comparative Examples were covered with a nickel film by electroless plating, and then a copper film and a nickel film were sequentially laminated by electroplating to produce an electromagnetic wave shielding material.

<Evaluation>

[shipping characteristics]

The nonwoven fabric for electromagnetic wave shielding materials was conveyed at a constant tension, and the occurrence of wrinkles at that time was evaluated according to the following criteria.

"○" does not cause wrinkles and is very good in transportability.

"△" part of the nonwoven fabric for the electromagnetic wave shielding material is wrinkled, but there is no problem with the transportability.

"x" was wrinkled to such an extent that the whole nonwoven fabric for electromagnetic shielding materials could not be processed, and the transportability was poor.

[Electromagnetic wave shielding property (electric field)]

It measured based on the electromagnetic wave shielding property (electric field) by the coaxial tube method. It measures by the coaxial tube method 39D in the frequency range of 40 MHz-3 GHz, and measures by the coaxial tube method GPC7 in the frequency range of 500 MHz-18 GHz. The frequency of 500 MHz to 3 GHz is measured by both the coaxial tube method 39D and the coaxial tube method GPC7, and a lower numerical value is adopted.

The higher the numerical value described in the electromagnetic wave shielding property, the more excellent the electromagnetic wave shielding property is.

[Table 1]

Since the nonwoven fabrics for electromagnetic wave shielding materials of Examples 1 to 10 contain two or more kinds of stretched polyester staple fibers with different fiber diameters selected from stretched polyester staple fibers with a fiber diameter of 3 μm or more and less than 12 μm, The fiber and undrawn polyester staple fiber with a fiber diameter of 3 μm or more and 5 μm or less are wet-laid nonwoven fabrics as an essential component, so it has excellent conveyability and excellent electromagnetic wave shielding properties. Although the strength of the nonwoven fabric for electromagnetic wave shielding material of Example 4 was slightly lowered, there was no problem with transportability, and the electromagnetic wave shielding property was also excellent.

On the other hand, it does not contain two or more kinds of drawn polyester staple fibers with different fiber diameters selected from drawn polyester staple fibers with a fiber diameter of 3 μm or more and less than 12 μm and a fiber diameter of 3 μm or more and 5 μm or less. The nonwoven fabrics for electromagnetic wave shielding materials of Comparative Examples 1, 2, 3, and 4, in which the unstretched polyester staple fiber is an essential component, were poor in electromagnetic wave shielding properties. That is, it is considered that the nonwoven fabric for electromagnetic wave shielding material of Comparative Example 1 in which the fiber diameter of the unstretched polyester staple fiber exceeds 5 μm, and the fiber diameter of the stretched polyester staple fiber selected from the fiber diameter of 12 μm or more are different. The nonwoven fabric for electromagnetic wave shielding material of Comparative Example 3 of the two kinds of stretched polyester staple fibers, the nonwoven fabric for electromagnetic wave shielding material of Comparative Example 4 of comparative example 4 in which the fiber diameter of stretched polyester staple fibers is 12 μm, and The electromagnetic wave shielding material of Comparative Example 2 containing only one kind of drawn polyester staple fiber with the same fiber diameter (fiber diameter 5.3 μm) although it contains drawn polyester staple fibers with a fiber diameter of 3 μm or more and less than 12 μm The multiple reflection loss of the woven cloth is reduced.

In addition, the electromagnetic wave shielding material of Comparative Example 5 containing only one type of drawn polyester staple fiber (fiber diameter 3.0 μm) with the same fiber diameter although it contains drawn polyester staple fibers with a fiber diameter of 3 μm or more and less than 12 μm Wrinkles are generated when the mesh cloth is transported by the non-woven fabric, and the transport property is poor. It is considered that by including only stretched polyester staple fibers with a small fiber diameter, the mesh fabric becomes soft, stretches easily, and creases easily occur.

"Example of the nonwoven fabric <2> for electromagnetic wave shielding material of the present invention"

<Evaluation>

(1) Surface resistance value

Measurements were performed based on MIL DTL 83528C.

(2) Electromagnetic wave shielding (electric field)

It measured based on the electromagnetic wave shielding property (electric field) by the coaxial tube method. It measures by the coaxial tube method 39D in the frequency range of 40 MHz-3 GHz, and measures by the coaxial tube method GPC7 in the frequency range of 500 MHz-18 GHz. The frequency of 500 MHz to 3 GHz is measured by both the coaxial tube method 39D and the coaxial tube method GPC7, but a low numerical value is adopted.

(3) Peeling evaluation

Adhesive tape (Nitto (registered trademark) 31B tape, manufactured by Nitto Denko Co., Ltd.) was attached to an electromagnetic wave shielding material sample of width 25 mm×length 150 mm, and rolled 10 times with a 2 kg roller at a speed of 300 mm/min. Then, the tape and the sample were formed at an angle of 180 degrees, and peeled off at a speed of 1000 mm/min. Evaluation was performed based on the following criteria.

<benchmark>

◯: Measurement was performed three times, and there was no breakage of the sample or adhesion of metal powder to the tape.

Δ: The measurement was performed three times, and the breakage of the sample and the adhesion of the metal powder to the adhesive tape occurred 1 to 2 times.

×: The measurement was performed three times, and the breakage of the sample and the adhesion of the metal powder to the adhesive tape occurred three times.

[Example 11]

Using a pulper, 20 parts by mass of stretched polyethylene terephthalate (PET) short fibers with a fineness of 0.06 dtex (fiber diameter of 2.4 μm) and a fiber length of 3 mm and a fineness of 0.3 dtex (fiber diameter of 5.3 μm), 40 parts by mass of stretched PET staple fibers with a fiber length of 3 mm and 40 parts by mass of unstretched PET staple fibers for a one-component binder with a fiber length of 3 mm and a fineness of 0.2 dtex (fiber diameter 4.3 μm) are dispersed in water , Prepare a uniform papermaking slurry with a concentration of 1% by mass. The papermaking slurry was prepared by a wet method using an inclined paper machine equipped with a papermaking net with an air permeability of 275 cm ³ /cm ² /sec and a texture [on the net: plain weave, on the bottom net: heavy flat weave]. The drum dryer at 135°C heat-seals the binder with unstretched PET-based short fibers to develop strength and make wet-laid non-woven fabrics. In addition, using a 1-clamp hot calendering device including a dielectric heating jacket roll (metal heating roll) and an elastic roll, under the conditions of a hot roll temperature of 200°C, a linear pressure of 100kN/m, and a processing speed of 100m/min The wet-laid nonwoven fabric was heat-calendered to produce a nonwoven fabric for an electromagnetic wave shielding material having a basis weight of 6.5 g/m ² and a density of 0.50 g/cm ³ .

Next, the above-mentioned nonwoven fabric for electromagnetic wave shielding material was covered with a nickel coating by electroless plating, and then a copper coating and a nickel coating were sequentially laminated by electroplating, and a metal coating was performed to obtain an electromagnetic shielding material with a thickness of 17.5 μm. Material.

[Example 12]

40 parts by mass of stretched PET-based staple fibers with a fineness of 0.06dtex (fiber diameter: 2.4μm) and a fiber length of 3mm, stretched PET-based staple fibers with a fineness of 0.3dtex (fiber diameter: 3.0μm) and a fiber length of 3mm 20 parts by mass, and fineness 0.2dtex (fiber diameter 4.3 μm), fiber length 3mm except 40 parts by mass of unstretched PET-based short fibers for single-component binders. spinning. Except for the condition that the processing speed was set at 50 m/min, the wet-laid nonwoven fabric was subjected to thermal calendering in the same manner as in Example 11 to produce an electromagnetic wave shielding material with a basis weight of 6.5 g/m ² and a density of 0.63 g/cm ³ non-woven fabric. Next, a metal coating treatment was performed in the same manner as in Example 11 to obtain an electromagnetic wave shielding material with a thickness of 16.0 μm.

[Example 13]

In addition to 60 parts by mass of stretched PET-based staple fibers with a fiber blend of 0.06 dtex (fiber diameter 2.4 μm) and a fiber length of 3 mm, and one-component type viscose with a fineness of 0.2 dtex (fiber diameter 4.3 μm) and a fiber length of 3 mm, A wet-laid nonwoven fabric was obtained in the same manner as in Example 11, except for 40 parts by mass of the unstretched PET-based staple fiber for the binder. Except for the conditions that the linear pressure was 125kN/m and the processing speed was 40m/min, the wet-laid nonwoven fabric was subjected to heat calendering in the same manner as in Example 11 to produce a fabric with a basis weight of 6.5g/m ² and a density of 0.80g/cm ^3. Non-woven fabrics are used as electromagnetic wave shielding materials. Next, a metal coating treatment was performed in the same manner as in Example 11 to obtain an electromagnetic wave shielding material with a thickness of 15.5 μm.

[Example 14]

A wet-laid nonwoven fabric was obtained in the same manner as in Example 11 except that the basis weight was 5.0 g/m ² . This wet-laid nonwoven fabric was heat-calendered in the same manner as in Example 13 to produce a nonwoven fabric for electromagnetic wave shielding materials with a density of 0.80 g/cm ³ . Next, the above-mentioned nonwoven fabric for electromagnetic wave shielding material was covered with a nickel film by sputtering, a copper film and a nickel film were sequentially laminated by electroplating, and metal film treatment was performed to obtain an electromagnetic wave shielding material with a thickness of 8.5 μm.

[Example 15]

A wet-laid nonwoven fabric was obtained in the same manner as in Example 12 except that the basis weight was 5.0 g/m ² . This wet-laid nonwoven fabric was heat-calendered in the same manner as in Example 11 to produce a nonwoven fabric for electromagnetic wave shielding materials with a density of 0.50 g/cm ³ . Next, the above-mentioned nonwoven fabric for electromagnetic wave shielding material was metal-coated similarly to Example 14, and the electromagnetic wave shielding material of thickness 12.0 micrometers was obtained.

[Example 16]

A wet-laid nonwoven fabric was obtained in the same manner as in Example 13 except that the basis weight was 5.0 g/m ² . This wet-laid nonwoven fabric was heat-calendered in the same manner as in Example 12 to produce a nonwoven fabric for electromagnetic wave shielding materials with a density of 0.63 g/cm ³ . Next, a metal coating treatment was performed in the same manner as in Example 14 to obtain an electromagnetic wave shielding material with a thickness of 10.0 μm.

[Comparative Example 11]

In addition to 60 parts by mass of stretched PET-based staple fibers with a fineness of 0.3 dtex (fiber diameter 5.3 μm) and a fiber length of 5 mm, and one-component type viscose with a fineness of 1.2 dtex (fiber diameter 10.7 μm) and a fiber length of 5 mm Except for 40 parts by mass of unstretched PET-based short fibers for the binder, the same procedure as in Example 11 was carried out to obtain a wet-laid nonwoven fabric with a basis weight of 10.0 g/m ² . Except being set as the conditions of linear pressure 135kN/m, processing speed 40m/min, this wet-laid nonwoven fabric is subjected to thermal calendering process in the same manner as in Example 11, and a density ^of 0.85g/cm is produced. Nonwoven fabric for electromagnetic wave shielding material . Next, a metal coating treatment was performed in the same manner as in Example 14 to obtain an electromagnetic wave shielding material with a thickness of 16.0 μm.

[Comparative Example 12]

A nonwoven fabric for electromagnetic wave shielding materials with a basis weight of 10.0 g/m ² and a density of 0.63 g/cm ³ was produced in the same manner as in Comparative Example 11 except that the linear pressure was 100 kN/m and the processing speed was 50 m/min. . Next, metal coating treatment was performed in the same manner as in Comparative Example 11 to obtain an electromagnetic wave shielding material with a thickness of 20.0 μm.

[Comparative Example 13]

A nonwoven fabric for electromagnetic shielding materials with a basis weight of 10.0 g/m ² and a density of 0.45 g/cm ³ was produced in the same manner as in Comparative Example 11 except that the linear pressure was 90 kN/m and the processing speed was 100 m/min. . Next, metal coating treatment was performed in the same manner as in Comparative Example 11 to obtain an electromagnetic wave shielding material with a thickness of 26.0 μm.

[Comparative Example 14]

In the same manner as in Comparative Example 11, a nonwoven fabric for an electromagnetic shielding material having a basis weight of 10.0 g/m ² and a density of 0.85 g/cm ³ was produced. Next, a metal coating treatment was performed in the same manner as in Example 11 to obtain an electromagnetic wave shielding material with a thickness of 16.0 μm.

[Comparative Example 15]

In the same manner as in Comparative Example 12, a nonwoven fabric for an electromagnetic shielding material having a basis weight of 10.0 g/m ² and a density of 0.63 g/cm ³ was produced. Next, metal coating treatment was performed in the same manner as in Comparative Example 14 to obtain an electromagnetic wave shielding material with a thickness of 20.0 μm.

[Comparative Example 16]

In the same manner as in Comparative Example 13, a nonwoven fabric for an electromagnetic shielding material having a basis weight of 10.0 g/m ² and a density of 0.45 g/cm ³ was produced. Next, a metal coating treatment was performed in the same manner as in Comparative Example 14 to obtain an electromagnetic wave shielding material with a thickness of 26.0 μm.

[Table 2]

As a non-woven fabric for electromagnetic wave shielding materials that contains stretched polyester staple fibers with a fiber diameter of less than 3 μm and unstretched polyester staple fibers with a fiber diameter of 3 μm or more and 5 μm or less as essential components, weight per unit area Examples 11 to 16 of the electromagnetic wave shielding materials in which the wet-laid nonwoven fabric with a density of 7 g/m ² or less and a density of 0.5 to 0.8 g/cm ³ is treated with a metal coating have excellent electromagnetic wave shielding properties, and the metal coating can be easily peeled off. Effect. In addition, it can be seen that the metal coating treatment sequentially includes sputtering to form a nickel coating, electroplating to form a copper coating, and electroplating to form a nickel coating. Examples in which the thickness is 15 μm or less and the surface resistance value is 0.03 Ω/□ or less Compared with the electromagnetic wave shielding materials of Examples 11 to 13, the electromagnetic wave shielding materials of 14 to 16 were more excellent in electromagnetic wave shielding properties, and the metal film was less likely to be peeled off.

Comparative Examples 11 to 16 are nonwoven fabrics for electromagnetic wave shielding materials that contain stretched PET staple fibers with a fiber diameter of 3 μm or more and undrawn PET staple fibers with a fiber diameter of more than 5 μm, and have a weight per unit area of more than 7 g. It is an electromagnetic wave shielding material made of a wet-laid non-woven fabric with a thickness of 1/m ² and treated with a metal coating. In Comparative Examples 11 and 13, in which the metal coating treatment sequentially included nickel coating by sputtering, copper coating by electroplating, and nickel coating by electroplating, the results of electromagnetic shielding and peeling evaluation were poor. The electromagnetic wave shielding material of Comparative Example 12 was good in evaluation of electromagnetic wave shielding property and peeling, but the thickness of the electromagnetic wave shielding material was 20.0 μm, and it could not be reduced in thickness. In Comparative Examples 14 to 16, the electroless plating process was used to cover the nickel film, and then the copper film and the nickel film were sequentially laminated by the electroplating process to implement the metal film treatment. Although the results of the peeling evaluation were good, the electromagnetic wave Poor shielding.

"Examples of the nonwoven fabric <3> for electromagnetic wave shielding material of the present invention"

[Example 21]

Using a pulper, 30 parts by mass of stretched polyethylene terephthalate (PET) short fibers with a fineness of 0.6 dtex (fiber diameter of 7.4 μm) and a fiber length of 5 mm and a fineness of 0.3 dtex (fiber diameter of 5.3 μm), 30 parts by mass of stretched PET-based short fibers with a fiber length of 3 mm, and 40 parts by mass of undrawn PET-based short fibers for one-component binders with a fineness of 0.2 dtex (fiber diameter of 4.3 μm), a fiber length of 3 mm, and a melting point of 246° C. 1 part was dispersed in water to prepare a uniform slurry for papermaking with a concentration of 1% by mass. The papermaking slurry was prepared by a wet method using an inclined paper machine equipped with a papermaking net with an air permeability of 275 cm ³ /cm ² /sec and a texture [on the net: plain weave, on the bottom net: heavy flat weave]. The drum dryer at 135°C heat-seals the binder with unstretched PET-based short fibers to develop strength, and makes a wet-laid non-woven fabric with a unit area weight of 10 g/m ² . In addition, using a 1-clamp hot calendering device including a dielectric heating jacket roll (metal heating roll) and an elastic roll, under the conditions of a hot roll temperature of 202°C, a linear pressure of 100kN/m, and a processing speed of 40m/min This wet-laid nonwoven fabric was heat-calendered to produce a nonwoven fabric for electromagnetic shielding materials having a thickness of 15 μm and a peel strength of 2.1 N/m.

[Example 22]

Except having made the heat roll temperature into 208 degreeC, it carried out similarly to Example 21, and produced the nonwoven fabric for electromagnetic wave shielding materials with thickness 15 micrometers and peeling strength 3.1 N/m.

[Example 23]

Except having set the heat roll temperature to 205 degreeC, it carried out similarly to Example 21, and produced the nonwoven fabric for electromagnetic wave shielding materials with thickness 15 micrometers and peeling strength 4.2 N/m.

[Example 24]

Except that the compounding of drawn polyester staple fiber is 30 parts by mass of drawn PET staple fiber with a fineness of 0.6 dtex (fiber diameter 7.4 μm) and a fiber length of 3 mm, and a fineness of 0.1 dtex (fiber diameter 3.0 μm), a fiber length of Except for 30 parts by mass of stretched PET-based short fibers of 3 mm, the same procedure as in Example 23 was carried out to produce a nonwoven fabric for electromagnetic wave shielding materials with a thickness of 15 μm and a peel strength of 3.5 N/m.

[Example 25]

Except that the compounding of the stretched polyester staple fiber is 30 parts by mass of stretched PET staple fiber with a fineness of 0.6dtex (fiber diameter: 7.4μm) and a fiber length of 3mm, and a fineness of 0.06dtex (fiber diameter: 2.4μm), and a fiber length of Except for 30 parts by mass of stretched PET-based short fibers of 3 mm, a nonwoven fabric for electromagnetic shielding materials having a thickness of 15 μm and a peel strength of 3.7 N/m was produced in the same manner as in Example 23.

[Example 26]

In addition to setting the blending of drawn polyester staple fibers to 30 parts by mass of drawn PET staple fibers with a fineness of 0.3 dtex (fiber diameter 5.3 μm) and a fiber length of 3 mm, and a fineness of 0.1 dtex (fiber diameter 3.0 μm), the fiber length Except for 30 parts by mass of stretched PET-based short fibers of 3 mm, a nonwoven fabric for electromagnetic shielding materials having a thickness of 15 μm and a peel strength of 3.4 N/m was produced in the same manner as in Example 23.

[Example 27]

Except that the compounding of the stretched polyester staple fiber is 30 parts by mass of stretched PET staple fiber with a fineness of 0.3 dtex (fiber diameter 5.3 μm) and a fiber length of 3 mm, and a fineness of 0.06 dtex (fiber diameter 2.4 μm), a fiber length Except for 30 parts by mass of stretched PET-based staple fibers of 3 mm, the same procedure as in Example 23 was carried out to produce a nonwoven fabric for electromagnetic wave shielding materials with a thickness of 15 μm and a peel strength of 3.3 N/m.

[Example 28]

Except that the compounding of drawn polyester staple fiber is 30 parts by mass of drawn PET staple fiber with fineness 0.1dtex (fiber diameter 3.0μm), fiber length 3mm, fineness 0.06dtex (fiber diameter 2.4μm), fiber length Except for 30 parts by mass of stretched PET-based short fibers of 3 mm, the same procedure as in Example 23 was carried out to produce a nonwoven fabric for electromagnetic wave shielding materials with a thickness of 15 μm and a peel strength of 3.5 N/m.

[Comparative Example 21]

Except having set the heat roll temperature to 198 degreeC, it carried out similarly to Example 21, and produced the nonwoven fabric for electromagnetic wave shielding materials with thickness 15 micrometers and peeling strength 1.8 N/m.

[Comparative Example 22]

Except having set the heat roll temperature to 195 degreeC, it carried out similarly to Example 21, and produced the nonwoven fabric for electromagnetic wave shielding materials with thickness 15 micrometers and peeling strength 1.0 N/m.

[Comparative Example 23]

Except having made the heat roll temperature into 198 degreeC, it carried out similarly to Example 24, and produced the nonwoven fabric for electromagnetic wave shielding materials with thickness 15 micrometers and peeling strength 1.5 N/m.

[Comparative Example 24]

Except having set the heat roll temperature to 198 degreeC, it carried out similarly to Example 25, and produced the nonwoven fabric for electromagnetic wave shielding materials with thickness 15 micrometers and peeling strength 1.0 N/m.

[Comparative Example 25]

In addition to setting the blend of fibers to 30 parts by mass of stretched PET-based staple fibers with a fineness of 0.6dtex (fiber diameter of 7.4μm) and a fiber length of 3mm, stretched PET-based staple fibers of a fineness of 0.3dtex (fiber diameter of 5.3μm) and a fiber length of 3mm 30 parts by mass of fibers, 0.1 dtex (fiber diameter: 3.0 μm), 30 parts by mass of stretched PET-based staple fibers with a fiber length of 3 mm, and a single set of 0.2 dtex (fiber diameter: 4.3 μm), a fiber length of 3 mm, and a melting point of 246°C Except for 10 parts by mass of the unstretched PET-based short fibers for the parting adhesive, the same procedure as in Example 23 was carried out to produce a nonwoven fabric for electromagnetic wave shielding materials with a thickness of 15 μm and a peel strength of 0.2 N/m.

[Comparative Example 26]

In addition to setting the blending of fibers at a fineness of 0.6dtex (fiber diameter 7.4μm), 10 parts by mass of drawn PET-based staple fibers with a fiber length of 3mm, and a fiber length of 3mm with a fiber length of 3mm and a melting point of 246°C Except for 90 parts by mass of unstretched PET-based short fibers for one-component binders, a nonwoven fabric for electromagnetic wave shielding materials with a thickness of 15 μm and a peel strength of 1.8 N/m was produced in the same manner as in Example 23.

The nonwoven fabrics for electromagnetic wave shielding materials produced in Examples and Comparative Examples were subjected to alkali treatment as a pre-plating treatment, and metal plating treatment of copper and nickel was performed by electroless plating to produce electromagnetic wave shielding materials.

<Evaluation>

[Peel strength]

The electromagnetic wave shielding material was cut into 25 mm × 200 mm with a non-woven fabric, and a double-sided tape (manufactured by NICHIBAN, trade name: NW-R25, NICETACK (registered trademark) low-adhesion type) was attached to a backing paper (manufactured by Mitsubishi Paper Co., Ltd. , product name: N peal card (registered trademark) FSC certification - MX (450.0g/m ² )) on the non-glossy side, from which the non-woven fabric for electromagnetic wave shielding material is laminated, and the packaging tape ( KAMOI KAKOSHI Co., Ltd. product, trade name: No. 220W), the peeling test was implemented in the form shown in FIG. 1, and the peeling strength was measured. In the peeling test, the device name: Digital Force Gauge FGC-2B manufactured by SHIMPO (NIDEC-SHIMPO) was used, the distance between jigs was set to 1.8 cm, and the nonwoven fabric for electromagnetic wave shielding material was positioned at the center of the distance. The measurement was performed under the condition of a speed of 100 mm/min.

[Fiber shedding resistance]

Take a non-woven fabric for electromagnetic wave shielding materials, cut it into 25 mm × 200 mm, and use a Gakushin type friction fastness tester to use a Billikenmos (Japanese original: ビリケンモス) (registered trademark) cloth with a weight of 500 gf. The electromagnetic wave shielding material was reciprocated and rubbed five times with a nonwoven fabric, and evaluated according to the following criteria.

"◎" Fibers are not attached to Billikenmos cloth.

"O" fibers hardly adhere to the Billikenmos cloth.

The "△" fibers were slightly attached to the Billikenmos cloth, but there was no practical problem.

"X" fibers adhere to the Billikenmos cloth, and the base material may be broken in some cases.

[Defect frequency]

The frequency of defects per 1000 m when the metal plating treatment was performed on the nonwoven fabric for electromagnetic wave shielding materials subjected to the alkali treatment as the plating pretreatment was confirmed.

"◎" 0 pieces/1000m.

"○"1 piece/1000m.

"△" 2 pieces/1000m.

More than 3 "×"/1000m.

[Electromagnetic wave shielding properties (electric field)]

It measured based on the electromagnetic wave shielding property (electric field) by the coaxial tube method. It measures by the coaxial tube method 39D in the frequency range of 40 MHz-3 GHz, and measures by the coaxial tube method GPC7 in the frequency range of 500 MHz-18 GHz. The frequency of 500 MHz to 3 GHz is measured by both the coaxial tube method 39D and the coaxial tube method GPC7, and a lower numerical value is adopted.

The higher the numerical value described in the electromagnetic wave shielding property, the more excellent the electromagnetic wave shielding property is.

[table 3]

The nonwoven fabrics for electromagnetic wave shielding materials of Examples 21 to 28 have higher peel strength than the nonwoven fabrics for electromagnetic wave shielding materials of Comparative Examples 21 to 26, so they have excellent fiber shedding resistance and have less defect frequency, so the finished products The efficiency is also good, showing excellent electromagnetic wave shielding properties.

When comparing Examples 21 to 23, in Example 23 in which the heat roll temperature was 205° C., the peel strength was the highest, and the fiber dropout resistance was improved. On the other hand, in Comparative Examples 21 to 24, since the heat roll temperature was lower than 200° C., the nonwoven fabric for electromagnetic wave shielding materials had low peel strength, poor fiber shedding resistance, and very high defect frequency.

In Comparative Examples 25 and 26, the content of unstretched polyester staple fibers was less than 20% by mass or exceeded 80% by mass relative to the entire fibers constituting the nonwoven fabric for electromagnetic wave shielding materials, which deviated from the ideal range. The roll temperature was 205° C., which was an ideal range, but it was a nonwoven fabric for electromagnetic wave shielding materials with low peel strength and poor fiber shedding resistance.

Industrial availability

The nonwoven fabric for electromagnetic wave shielding material and the electromagnetic wave shielding material of the present invention are suitable for use in electronic equipment, communication equipment, electric appliances, and the like. These devices and products include devices such as mobile phones, smartphones, mobile phones, personal computers, and mobile phones, boxes for storing them, and electrical appliances such as televisions and washing machines. In particular, the electromagnetic wave shielding material of the present invention is suitably used for fixing to plastic cases, flexible printed boards, electric wires and cables, connector cables, etc. by bonding, crimping, welding, winding, and the like.

Claims (5)

1. A nonwoven fabric for an electromagnetic wave shielding material, which is a wet nonwoven fabric, characterized in that the wet nonwoven fabric contains, as essential components, 2 or more types of drawn polyester staple fibers having different fiber diameters from among drawn polyester staple fibers having a fiber diameter of 3 [ mu ] m or more and less than 12 [ mu ] m, and undrawn polyester staple fibers having a fiber diameter of 3 [ mu ] m or more and 5 [ mu ] m or less.

2. An electromagnetic wave shielding material, characterized in that the nonwoven fabric for electromagnetic wave shielding material according to claim 1 is subjected to a metal coating treatment.

3. The electromagnetic wave shielding material according to claim 2, wherein the metal coating treatment is 1 or more selected from the group consisting of an electroless metal plating treatment, an electroplating treatment, a metal evaporation treatment, and a sputtering treatment.

4. The electromagnetic wave shielding material according to claim 2, wherein the metal coating treatment includes a treatment of forming a nickel coating by sputtering, a treatment of forming a copper coating by electroplating, and a treatment of forming a nickel coating by electroplating in this order.

5. The electromagnetic wave shielding material according to any one of claims 2 to 4, wherein the thickness of the electromagnetic wave shielding material is 15 μm or less, and the surface resistance value of the electromagnetic wave shielding material is

The following.

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