TW202030392A - Non-woven fabric for electromagnetic wave shielding materials and electromagnetic wave shielding material - Google Patents

Abstract

The problem of the present invention is to provide: a non-woven fabric base material for electromagnetic wave shielding materials, which can exhibit excellent electromagnetic wave shielding properties; and an electromagnetic wave shielding material. A non-woven fabric for electromagnetic wave shielding materials, which is a wet-type non-woven fabric comprising at least two types of stretched polyester-based short fibers and a non-stretched polyester-based short fiber, wherein the stretched polyester-based short fibers are independently selected from stretched polyester-based short fibers each having a fiber diameter of 3 [mu]m or more and less than 12 [mu]m and have different fiber diameters from each other and the non-stretched polyester-based short fiber has a fiber diameter of 3 to 5 [mu]m inclusive; a non-woven fabric for electromagnetic wave shielding materials, which is a wet-type non-woven fabric comprising a stretched polyester-based short fiber having a fiber diameter of less than 3 [mu]m and a non-stretched polyester-based short fiber having a fiber diameter of 3 to 5 [mu]m inclusive, wherein the non-woven fabric has an areal fiber weight of 7 g/m2 or less and a density of 0.5 to 0.8 g/cm3; and a non-woven fabric for electromagnetic wave shielding materials, which comprises a stretched polyester-based short fiber and a non-stretched polyester-based short fiber having a melting point of 220 to 250 DEG C inclusive, wherein the peel strength (in the vertical direction) of the non-woven fabric is 2.0 N/m or more.

Description

Non-woven fabric for electromagnetic wave shielding material and electromagnetic wave shielding material

The present invention relates to a non-woven fabric for an electromagnetic wave shielding material and an electromagnetic wave shielding material that has excellent transportability of the screen and can exhibit excellent electromagnetic wave shielding properties.

Electronic equipment generates electromagnetic waves. In addition, in order to prevent electromagnetic waves from leaking to the outside of the electronic device, and to prevent electromagnetic waves from causing abnormalities in the electronic device, electromagnetic wave shielding materials are used. Examples of electromagnetic wave shielding materials include sheet metal, metal-containing paint, metal mesh, and foamed metal. In addition, some people disclose electromagnetic wave shielding materials obtained by applying metal plating to a non-woven fabric made of polyester short fibers (for example, refer to Patent Documents 1 and 2).

Patent Document 1 discloses an electromagnetic wave shielding material in which a continuous metal conductive layer is adhered to the entire periphery of a non-conductive fiber fabric, braid, or non-woven fabric by a wet plating method. As far as chemical fibers are concerned, polyester fibers and polypropylene fibers have excellent tensile strength and elongation properties of the base material, and can prevent the deterioration of properties in the pre-plating treatment step, and are described as being more desirable.

Patent Document 2 discloses an electromagnetic wave shielding material, which is an electromagnetic wave shielding material obtained by applying a metal coating to a wet nonwoven fabric, and is characterized in that it contains polyester fibers with a single fiber fineness of 1.1 dtex or less and has a thickness of 10 to 30 μm. In the range.

With the recent miniaturization, higher frequency, and higher performance of electronic devices, thinner electromagnetic wave shielding materials with high electromagnetic wave shielding properties are required. Specifically, it requires an electromagnetic wave shielding material that has a thickness of 15 μm or less and exhibits excellent electromagnetic wave shielding properties in a wide frequency range of 100 MHz to 10 GHz.

For example, in Patent Documents 1 and 2, when metal coating treatment such as metal plating treatment is applied to the non-woven fabric, although it is processed by a roll-to-roll method with good productivity, the non-woven fabric will be wrinkled during transportation, and there may be transportation. The problem of poor sex.

In addition, in the example of Patent Document 2, it discloses an electromagnetic wave shielding material, which comprises a polyester stretched fiber with a single fiber fineness of 0.1 dtex and an unstretched adhesive fiber with a single fiber fineness of 0.2 dtex, and a base paper base of a wet non-woven fabric The weight is 8 g/m ² , the basis weight of the electromagnetic wave shielding material is 19 g/m ² , and the thickness is 12 μm. However, as a thinner electromagnetic wave shielding material is required, the electromagnetic wave shielding material of Patent Document 2 has a problem that it cannot sufficiently ensure electromagnetic wave shielding properties. Moreover, the problem of peeling of the metal film sometimes occurs.

In addition, the electromagnetic wave shielding material obtained by applying metal plating to the non-woven fabric requires that the polyester staple fiber and the metal film formed by the metal plating be in close contact with each other. Therefore, it is known as a pre-plating process It is alkali treatment of polyester staple fiber.

Patent Document 1 describes that polyester fibers can prevent the deterioration of characteristics in the pretreatment step of plating. However, the alkali treatment of non-woven fabrics is usually a wet treatment, and the fibers will fall off into the water tank, which significantly deteriorates the workability. In addition, since the fallen fibers will re-attach to the non-woven fabric, the problem of defects in the metal plating process may sometimes occur. [Prior Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Unexamined Publication No. 48-40800 [Patent Document 2] JP 2014-75485 A

[The problem to be solved by the invention]

The first subject of the present invention is to provide a non-woven fabric for electromagnetic wave shielding material that has excellent transportability and can exhibit excellent electromagnetic wave shielding properties, and an electromagnetic wave shielding material using the non-woven fabric for electromagnetic wave shielding material.

The second subject of the present invention is to provide a non-woven fabric for electromagnetic wave shielding material that is thin, can exhibit excellent electromagnetic wave shielding properties, and the metal film is not easily peeled off, and an electromagnetic wave shielding material using the non-woven fabric for electromagnetic wave shielding material.

The third subject of the present invention is to provide a non-woven fabric for electromagnetic wave shielding material with high strength during the alkali treatment of the plating pre-treatment step for electromagnetic wave shielding material, and the electromagnetic wave shielding material using the non-woven fabric for electromagnetic wave shielding material. material. [Means to solve the problem]

The inventors of the present application have worked hard to solve the above-mentioned problems and found the following invention as a result.

<1> A non-woven fabric for electromagnetic wave shielding material, which is a wet-type non-woven fabric, characterized in that: the wet-type non-woven fabric contains two different fiber diameters selected from stretched polyester staple fibers with a fiber diameter of 3 μm or more and less than 12 μm The above-mentioned stretched polyester staple fibers and unstretched polyester staple fibers with 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 material, which is a wet non-woven fabric characterized in that it 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 to 5 μm As an essential component, the basis weight is 7 g/m ² or less and the density is 0.5 to 0.8 g/cm ³ .

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

<4> An electromagnetic wave shielding material characterized in that the electromagnetic wave shielding material of any one of the above <1> to <3> is formed by applying a metal coating to the non-woven fabric.

<5> The electromagnetic wave shielding material according to the above <4>, wherein the metal film treatment is one or more treatments selected from the group consisting of electroless metal plating treatment, electroplating treatment, metal evaporation treatment, and sputtering treatment.

<6> The electromagnetic wave shielding material as in the above <4>, in which the metal film treatment includes, in order, the treatment of forming nickel coating by sputtering, the treatment of forming copper coating by electroplating, and the treatment of nickel coating by electroplating Treatment of coating formation.

<7> The electromagnetic wave shielding material according to any one of the above <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 0.03Ω/□ or less. [Effects of Invention]

The first effect of the present invention is to provide a non-woven fabric for electromagnetic wave shielding material that is excellent in transportability and exhibits excellent electromagnetic wave shielding properties, and an electromagnetic wave shielding material using the non-woven fabric for electromagnetic wave shielding material.

The second effect of the present invention is to provide a non-woven fabric for electromagnetic wave shielding material that is thin, can exhibit excellent electromagnetic wave shielding properties, and the metal film is not easily peeled off, and an electromagnetic wave shielding material using the non-woven fabric for electromagnetic wave shielding material.

The third effect of the present invention is to provide a non-woven fabric for electromagnetic wave shielding material with high strength during the alkali treatment in the pre-treatment step of plating for electromagnetic wave shielding material, and electromagnetic wave using the non-woven fabric for electromagnetic wave shielding material. Shading material.

[The form of implementing the invention]

The non-woven fabric for electromagnetic wave shielding material and the electromagnetic wave shielding material of the present invention will be described in detail below.

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

Generally speaking, when the non-woven fabric is transported in roll-to-roll processing, tension is applied to the non-woven fabric in the MD (Machine Direction) direction, which causes the non-woven fabric to stretch, which causes wrinkles. The non-woven fabric <1> for electromagnetic wave shielding materials of the present invention contains two or more types 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, and An undrawn polyester staple fiber with a fiber diameter of 3 μm or more and 5 μm or less is an essential component, and one type of stretched polyester staple fiber that contains the same fiber diameter selected from a fiber diameter of 3 μm or more and less than 12 μm. Short fibers are less likely to stretch than non-woven fabrics with non-stretched polyester staple fibers having a fiber diameter of 3 μm or more and 5 μm or less as an essential component, so that wrinkles are less likely to occur during transportation. In addition, when a non-woven fabric having a fiber diameter of 12 μm or more of stretched polyester short fibers is used, it is difficult to obtain a thin electromagnetic wave shielding material. The non-woven fabric for electromagnetic wave shielding material of the present invention <1> can be thin and excellent in transportability by including stretched polyester staple fibers with a fiber diameter of less than 12μm and unstretched polyester staple fibers with a fiber diameter of 3μm to 5μm. The effect.

Generally speaking, electromagnetic shielding is achieved by electromagnetic wave absorption reflection loss, reflection loss, and multiple reflection loss. In the non-woven fabric <1> for electromagnetic wave shielding materials of the present invention, by using two or more types of stretched polyester staple fibers selected from stretched polyester staple fibers with a fiber diameter of 3 μm or more and less than 12 μm, which have different fiber diameters, The electromagnetic wave that enters the electromagnetic wave shielding material is more likely to be repeatedly reflected in the electromagnetic wave shielding material, and excellent electromagnetic wave shielding performance due to multiple reflection losses can be obtained.

In the non-woven fabric for electromagnetic wave shielding material <1> of the present invention, the mass content ratio of stretched polyester staple fiber to unstretched polyester staple fiber is preferably 10:90~90:10, more preferably 20:80~80 : 20, even better 30:70~70:30. If the content of the undrawn polyester staple fiber is less than 10% by mass of the total fiber constituting the wet-type nonwoven fabric, the strength required as a nonwoven fabric for electromagnetic wave shielding material cannot be exhibited. On the other hand, if the content of the undrawn polyester staple fiber exceeds 90% by mass, uniformity is impaired.

In the nonwoven fabric <1> for electromagnetic wave shielding materials 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, undrawn polyester staple fibers other than undrawn polyester staple fibers having a fiber diameter of 3 μm or more and 5 μm or less may also be used. In other words, stretched polyester staple fibers with a fiber diameter of less than 3μm, stretched polyester staple fibers with a fiber diameter of 12μm or more, unstretched polyester staple fibers with a fiber diameter of less than 3μm, and fiber diameters of more than 5μm can also be used. The unstretched polyester staple fiber. These can be used alone, or two or more fiber diameters can be used in combination.

In the non-woven fabric for electromagnetic wave shielding material <1> of the present invention, for stretched polyester staple fibers having a fiber diameter of 3 μm or more and less than 12 μm, the mass content of the stretched polyester staple fibers is preferably 1 to 100% by mass, more preferably 3 to 100% by mass. When the content of stretched polyester staple fibers having a fiber diameter of 3 μm or more and less than 12 μm is less than 1% by mass in all stretched polyester staple fibers, a thin electromagnetic shielding material with excellent transportability cannot be obtained.

Furthermore, in the non-woven fabric for electromagnetic wave shielding material <1> of the present invention, the undrawn polyester staple fiber with a fiber diameter of 3 μm or more and 5 μm or less has a mass content rate among all the undrawn polyester staple fibers contained It is preferably 1 to 100% by mass, and more preferably 2 to 100% by mass. When the content of undrawn polyester staple fibers with a fiber diameter of 3μm or more and 5μm or less is less than 1% by mass, depending on the fiber diameter used in combination, the specific surface area may be small and it is difficult to exhibit excellent electromagnetic wave shielding properties. Moreover, sometimes it is not easy to exhibit the strength of the wet non-woven fabric.

The thickness of the non-woven fabric <1> for electromagnetic wave shielding material of the present invention is intended to be used in electronic equipment, preferably 7-30 μm, more preferably 15 μm or less. The basis weight (weight per unit area) is preferably 5 to 30 g/m ² , and more preferably 15 g/m ² or less. If the basis weight is less than 5g/m ² , it is difficult to obtain uniformity, and the electromagnetic shielding effect is likely to be uneven.

-Non-woven fabric for electromagnetic wave shielding material <2>- The non-woven fabric for electromagnetic wave shielding material of the present invention <2> is characterized in that it is a wet non-woven fabric and contains stretched polyester staple fibers with a fiber diameter of less than 3 μm and the fiber diameter is As an essential component, non-stretched polyester staple fibers of 3 μm or more and 5 μm or less have a basis weight of 7 g/m ² or less and a density of 0.5 to 0.8 g/cm ³ .

Generally speaking, for the metal film treatment of the wet nonwoven fabric, the smaller the specific surface area (surface area per unit volume) of the fibers forming the wet nonwoven fabric, the smaller the amount of metal adhesion per unit volume, and it is difficult to exhibit excellent electromagnetic waves. Concealment. The non-woven fabric for electromagnetic wave shielding materials of the present invention <2> is a wet non-woven fabric containing 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 to 5 μm as essential components. Can increase the specific surface area, and can show excellent electromagnetic wave shielding. When the wet non-woven fabric is composed of only stretched polyester short fibers with a fiber diameter of 3 μm or more and undrawn polyester short fibers with a fiber diameter of more than 5 μm, it cannot exhibit excellent electromagnetic wave shielding properties. In addition, undrawn polyester staple fibers with fiber diameters of less than 3 μm are not easy to obtain. In addition, the fiber diameter of the stretched 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, the strength cannot be exhibited.

In the non-woven fabric for electromagnetic wave shielding material of the present invention <2>, the mass content ratio of stretched polyester staple fiber to unstretched polyester staple fiber is preferably 20:80~80:20, more preferably 30:70~70 : 30, better still 40:60~60:40. If the content of the undrawn polyester staple fiber is less than 20% by mass of the total fiber constituting the wet-type nonwoven fabric, the strength required as a nonwoven fabric for electromagnetic wave shielding material cannot be exhibited. On the other hand, if the content of the undrawn polyester staple fiber exceeds 80% by mass, uniformity is impaired.

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

In the non-woven fabric for electromagnetic wave shielding material of the present invention <2>, the content of stretched polyester staple fibers with a fiber diameter of less than 3μm is preferably 1-100% by mass in all stretched polyester staple fibers, and more Preferably, it is 3-100% by mass. When the content of stretched polyester staple fibers with a fiber diameter of less than 3μm is less than 1% by mass, the diameter of the combined fiber varies, and the specific surface area may be small and it is not easy to exhibit excellent electromagnetic wave shielding properties.

In addition, in the non-woven fabric for electromagnetic wave shielding material of the present invention <2>, the content of undrawn polyester staple fibers having a fiber diameter of 3 μm or more and 5 μm or less is preferably 1 among all undrawn polyester staple fibers. ~100% by mass, more preferably 2~100% by mass. When the content of undrawn polyester staple fibers with a fiber diameter of 3μm to 5μm is less than 1% by mass, the fiber diameter varies depending on the fiber diameter used together, and sometimes the specific surface area is small and it is difficult to exhibit excellent electromagnetic wave shielding properties, or it is difficult Demonstrates the strength of an excellent wet non-woven fabric.

In the non-woven fabric <2> for electromagnetic wave shielding materials of the present invention, the basis weight of the wet non-woven fabric is 7 g/m ² or less, more preferably 5 g/m ² or less, and still more preferably 4 g/m ² or less. If the basis weight exceeds 7g/m ² , it will become thicker after the metal film is processed, so that the thickness of the electromagnetic wave shielding material may exceed 15 μm, and it cannot be used in electronic equipment, communication equipment, electrical appliances, etc. In addition, the basis weight of the wet non-woven fabric is preferably 3 g/m ² or more. In addition, the basis weight is measured by the method described in JIS P8124:2011.

In the non-woven fabric for electromagnetic wave shielding material of the present invention <2>, the density of the wet non-woven fabric is 0.5 to 0.8 g/cm ³ , more preferably 0.55 to 0.65 g/cm ³ . With a transmission density of 0.8 g/cm ³ or less, the specific surface area can be increased, so that the metal film produced by the metal film treatment increases, and the electromagnetic wave shielding property is improved. In addition, the metal film is not easy to peel off. In addition, if the density is 0.5 g/cm ³ or more, the strength of the wet non-woven fabric will increase, problems will not easily occur in the treatment of the metal film, and the metal film will not easily peel off. In addition, the density is measured by the method described in JIS P8118:2014.

-Non-woven fabric for electromagnetic wave shielding material <3>- The non-woven fabric <3> for electromagnetic wave shielding materials of the present invention is a wet non-woven fabric containing stretched polyester short fibers and unstretched polyester short fibers with a melting point of 220°C or more and 250°C or less. Furthermore, the non-woven fabric <3> of the electromagnetic wave shielding material of the present invention has a peel strength (longitudinal direction) of 2.0 N/m or more.

In the non-woven fabric for electromagnetic wave shielding material <3> of the present invention, the peel strength (longitudinal direction) of the non-woven fabric for electromagnetic wave shielding material is 2.0 N/m or more, more preferably 2.5 N/m or more, and still more preferably 3.0 N/m or more. When the peel strength (longitudinal) is less than 2.0N/m, the adhesion between the fibers is too weak, causing a large amount of fibers to fall off from the non-woven fabric for electromagnetic wave shielding material during the alkali treatment, and the fibers accumulate on the conveying roller. Regular cleaning is required. This leads to the problem of poor workability, or the problem of defects in the metal plating process due to the detached fibers re-adhering to the non-woven fabric for electromagnetic wave shielding materials. In the nonwoven fabric for electromagnetic wave shielding material of the present invention <3>, the peel strength (longitudinal 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, the non-woven fabric for electromagnetic wave shielding material will be welded excessively, and the surface of the non-woven fabric for electromagnetic wave shielding material will become thinner and the shape cannot be maintained.

In the non-woven fabric <3> for electromagnetic wave shielding materials of the present invention, the fiber diameter of the stretched polyester staple fiber is preferably 1 to 10 μm, more preferably 2 to 8 μm. As the stretched polyester staple fiber, two or more stretched polyester staple fibers having different fiber diameters may be included. When the fiber diameter of the stretched 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 short fibers contain polyester short fibers having a fiber diameter of 3 μm or less as an essential component. By including short polyester fibers with a fiber diameter of 3μm or less, electromagnetic wave shielding properties can be further improved.

In the non-woven fabric <3> for electromagnetic wave shielding material of the present invention, the fiber diameter of the undrawn polyester staple fiber 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 with improved strength of the wet nonwoven fabric. As the undrawn polyester staple fiber, two or more types of undrawn polyester staple fibers having different fiber diameters may be included.

In the non-woven fabric <3> for electromagnetic wave shielding materials of the present invention, the mass content ratio of the stretched polyester short fibers to the undrawn polyester short fibers is preferably 20:80 to 80:20. If the content of the undrawn polyester staple fiber is less than 20% by mass of the total fiber constituting the wet-type nonwoven fabric, the strength required as a nonwoven fabric for electromagnetic wave shielding material cannot be exhibited. On the other hand, if the content of the undrawn polyester staple fiber exceeds 80% by mass, uniformity is impaired. Furthermore, in order to improve electromagnetic wave shielding properties, the content of stretched polyester staple fibers with a fiber diameter of 3 μm or less is more preferably 5 to 80% by mass of the total fiber constituting the wet nonwoven fabric. In the non-woven fabric for electromagnetic wave shielding material of the present invention <3>, the best fiber formulation is that the undrawn polyester staple fiber is 20 to 80% by mass, and the stretched polyester staple fiber with a fiber diameter exceeding 3 μm and less than 10 μm is 0 ~75% by mass and 5 to 80% by mass of stretched polyester staple fibers with a fiber diameter of 3μm or less.

The thickness of the non-woven fabric <3> for the electromagnetic wave shielding material of the present invention is intended to be used in electronic devices, preferably 5-30 μm, more preferably 20 μm or less. The basis weight (weight per unit area) is preferably 3 to 30 g/m ² , more preferably 15 g/m ² or less. If the basis weight is less than 3g/m ² , it is difficult to obtain uniformity, so that the electromagnetic wave shielding effect is likely to be uneven, and it is difficult to maintain the strength of the non-woven fabric for electromagnetic wave shielding material itself, resulting in difficulty in operation.

-Polyester staple fiber- In the present invention, the stretched polyester staple fiber is the main fiber that is not easy to melt or soften after hot calendering treatment, and forms the skeleton of the wet non-woven fabric.

In the present invention, the non-stretched polyester staple fiber is melted or softened by a hot calendering process, and functions as a binder fiber that improves the strength of the wet nonwoven fabric. The melting point of the undrawn polyester staple fiber is preferably 220°C to 250°C. In the non-woven fabric <3> for electromagnetic wave shielding materials of the present invention, the melting point of the undrawn polyester staple fiber is 220°C or more and 250°C or less. When the melting point of the undrawn polyester staple fiber is less than 220°C, the wet non-woven fabric will stick to the hot roller during the hot calendering process and cannot form a sheet. When it exceeds 250°C, the fibers are not adhered and the strength of the wet nonwoven fabric cannot be exhibited. The melting point of the undrawn polyester staple fiber is more preferably 225°C or more and 250°C or less.

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 using a differential scanning calorimeter in a nitrogen environment.

In addition, in the examples of the present invention, the fiber diameter of the polyester staple fiber refers to the fiber diameter before the nonwoven fabric is manufactured. The fiber diameter of the polyester staple fiber can be taken with a microscope to take a 3000x magnified photograph of the cross section of the wet nonwoven fabric or electromagnetic wave shielding material, and the cross-sectional area of the polyester staple fiber can be measured, and the cross-sectional shape of the fiber can be calculated as a circle. Measurement; At this time, it is better to find the arithmetic average of more than 10 fibers with approximately the same cross-sectional area.

The fiber length of the polyester staple fiber is preferably 1-20 mm, more preferably 1-10 mm, and still more preferably 2-8 mm. When the fiber length of polyester staple fiber is less than 1mm, it is difficult to exhibit the strength required as a wet non-woven fabric. When the fiber length of polyester staple fiber exceeds 20 mm, uniformity is impaired.

In the present invention, the polyester may include polyethylene terephthalate, polyethylene isophthalate, polyethylene terephthalate, polyethylene naphthalate, and polybutylene terephthalate. Diester, polybutylene naphthalate, etc. The polyester staple fiber is preferable in terms of the reduction in the fiber diameter in order to reduce the thickness of electromagnetic wave shielding, the ease of papermaking, and the dimensional stability when the plating treatment is performed in a wet alkaline treatment. The polyester staple fiber may be used alone or in combination of two or more kinds.

-Wet non-woven fabric- Various manufacturing methods such as spunbonding, meltblown, electrospinning, and wet methods can be used to form fibers into thin sheets. The non-woven fabric for electromagnetic wave shielding material of the present invention is made by wet method (papermaking method). ) The wet non-woven fabric formed into a sheet shape is a non-woven fabric with excellent strength and high uniformity. In addition, various methods such as a chemical bonding method and a thermal welding method can be exemplified as a method of joining fibers. Among these, the thermal welding method is preferred in terms of excellent durability or strength and a smooth surface of the non-woven fabric.

As the thermal welding method in the wet method, the sheet obtained by the papermaking method can be used when the multi-cylinder dryer, Yankee dryer, and through-air dryer are equivalent to the dryer used after papermaking. The method of thermal welding. In addition, it is also possible to use hot calendering treatment by using a hot calendering device with a combination of metal hot rollers/metal hot rollers, metal hot rollers/flexible rollers, metal hot rollers/cotton rollers, etc. Methods. Through thermal drying or hot calendering, the adhesive components will be thermally melted to produce thermal welding.

In addition, the conditions of hot calendering can be exemplified as follows, but are not limited to these. The temperature of the hot roll in the hot calendering treatment is preferably 200°C or more and 215°C or less. When the temperature of the hot roll is less than 200°C, the fibers are not adhered to each other and cannot exhibit strength. On the other hand, when the temperature of the heat roller exceeds 215°C, the wet nonwoven fabric sticks to the heat roller and cannot form a sheet. The temperature of the heat roller is more preferably 203°C or higher and 210°C or lower, and still more preferably 205°C or higher. In addition, in the non-woven fabric for electromagnetic wave shielding material of the present invention <3>, in order to increase the peel strength of the non-woven fabric for electromagnetic wave shielding material, it is preferable to include stretched polyester staple fibers and unstretched polyester with a melting point of 220°C or higher and 250°C or lower The short fiber wet non-woven fabric is hot-calendered using a hot roll with a temperature of 200°C or more and 215°C or less. More preferably, the temperature of the hot roll is 203°C or more and 210°C or less.

In order to exhibit strength, the pressure (line pressure) in the hot calendering treatment is preferably 50 to 250 kN/m, more preferably 80 to 150 kN/m. If the pressure is less than 50kN/m, the smoothness of the surface may be impaired. Also, if the speed is reduced, the thickness may not be reduced. When the pressure exceeds 250kN/m, the sheet may not be able to withstand the pressure and may break. The processing speed of hot calendering is preferably 1 to 300 m/min. The penetration processing speed is 1m/min or more, and the work efficiency is good. By setting the processing speed below 300m/min, heat can be transferred to the wet non-woven fabric, and the actual effect of thermal welding can be easily obtained. The number of clamping times of hot calendering is not particularly limited as long as it can conduct heat to the wet non-woven fabric. The combination of a metal heat roller/flexible roller can also clamp the heat from both sides of the wet non-woven fabric. Hold more than 2 times.

-Electromagnetic wave shielding material- The electromagnetic wave shielding material of the present invention is characterized in that the non-woven fabric of the electromagnetic wave shielding material of the present invention is processed by metal coating. That is, the electromagnetic wave shielding material of the present invention is characterized by including the non-woven fabric and metal film for the electromagnetic wave shielding material of the present invention.

In the present invention, the metal film treatment includes electroless metal plating treatment, electroplating treatment, metal vapor deposition treatment, sputtering treatment, and the like. It is possible to perform processing of 1 or more selected among these processings. Among them, since it can be thinned, the surface resistance value is easily lowered, and the metal film is not easily peeled off, it is preferable to perform the electroplating treatment after the sputtering treatment. The aforementioned metal film may be one layer or multiple layers of two or more layers.

The type of metal used in the metal film treatment includes gold, silver, copper, zinc, aluminum, nickel, tin, and alloys thereof. Among them, one or more metals selected from the group consisting of gold, silver, copper, aluminum, nickel and tin are preferred, and copper and nickel are more preferred in consideration of conductivity and manufacturing cost.

In the present invention, the metal film treatment preferably includes, in order, 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. First, a metal film is formed on the wet non-woven fabric by sputtering. The metal in the sputtering treatment is preferably nickel. After the sputtering treatment, the metal film is laminated by electroplating. The metal to be plated is preferably copper. Furthermore, in order to prevent rust, a metal with good rust resistance such as nickel may be laminated on the outer layer. The laminating method is preferably a method by 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 is greater than 15μm, it cannot be used in electronic equipment, communication equipment, electrical appliances, etc. In addition, the thickness of the electromagnetic wave shielding material is preferably 7 μm or more. In addition, the thickness is measured by the method described in JIS P8118:2014.

In addition, the surface resistance value of the electromagnetic wave shielding material of the present invention is preferably 0.03 Ω/□ or less, more preferably 0.01 Ω/□ or less. In addition, the electromagnetic shielding properties at 40 MHz to 18 GHz are preferably 50 dB or more. Furthermore, it is preferable that the electromagnetic wave shielding property at 40 MHz to 10 GHz is 60 dB or more. Furthermore, the electromagnetic shielding properties at 40 MHz to 1 GHz are preferably 70 dB or more. [Example]

The following examples are given to illustrate the present invention, but the present invention is not limited in any way by these examples. In addition, in the examples,% and parts are quality standards unless they are stated first.

≪Non-woven fabric for electromagnetic wave shielding material of the present invention <1> Related Examples≫

[Example 1] 30 parts by mass of stretched polyethylene terephthalate (PET) staple fiber with a fineness of 0.3 dtex (fiber diameter of 5.3 μm) and a fiber length of 3 mm, a fineness of 0.6 dtex (fiber diameter of 7.4 μm), and a fiber 30 parts by mass of stretched PET short fibers with a length of 5 mm and 40 parts by mass of undrawn PET short fibers with a fineness of 0.2 dtex (fiber diameter: 4.3 μm) and a fiber length of 3 mm are dispersed in water by a pulper to prepare a concentration of 1% by mass The uniform slurry for papermaking. The slurry for papermaking is lifted up by the wet method with an inclined paper machine equipped with a papermaking net with air permeability of 275cm ³ /cm ² /sec and weave [online: plain weave, lower net: striped weave]. Using a drum dryer at 135°C, the unstretched PET short fibers were thermally welded to exhibit strength, and a wet non-woven fabric with a basis weight of 10 g/m ² was made. Furthermore, this wet-type non-woven fabric was treated with a single-roll type hot calendering device composed of a dielectric heating jacket roll (metal heat roll) and an elastic roll. The heat roll temperature was 200°C, the linear pressure was 100kN/m, and the The hot-calendering process was performed at a speed of 30 m/min, and a non-woven fabric for electromagnetic wave shielding material with a thickness of 15 μm was produced.

[Example 2] Except for 10 parts by mass of stretched PET short fibers with a fineness of 0.3 dtex (fiber diameter of 5.3 μm) and a fiber length of 3 mm, 50 parts by mass of stretched 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 0.2 A non-woven fabric for electromagnetic wave shielding material having a thickness of 17 μm was prepared in the same manner as in Example 1 except for 40 parts by mass of undrawn PET short fibers having a dtex (fiber diameter of 4.3 μm) and a fiber length of 3 mm.

[Example 3] Except for 50 parts by mass of stretched PET short fibers with a fineness of 0.3 dtex (fiber diameter of 5.3 μm) and a fiber length of 3 mm, 10 parts by mass of stretched 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 0.2 A non-woven fabric for electromagnetic wave shielding material having a thickness of 16 μm was prepared in the same manner as in Example 1 except for 40 parts by mass of undrawn PET short fibers having a dtex (fiber diameter of 4.3 μm) and a fiber length of 3 mm.

[Example 4] Except for 45 parts by mass of stretched PET short fibers with a fineness of 0.3 dtex (fiber diameter of 5.3 μm) and a fiber length of 3 mm, 45 parts by mass of stretched 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 0.2 In the same manner as in Example 1, except for 10 parts by mass of undrawn PET short fibers having a dtex (fiber diameter of 4.3 μm) and a fiber length of 3 mm, a non-woven fabric for electromagnetic wave shielding material having a thickness of 16 μm was produced.

[Example 5] Except for 30 parts by mass of stretched PET short fibers with a fineness of 0.1 dtex (fiber diameter of 3.0 μm) and a fiber length of 3 mm, 30 parts by mass of stretched 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 0.2 A non-woven fabric for electromagnetic wave shielding material having a thickness of 14 μm was prepared in the same manner as in Example 1 except for 40 parts by mass of undrawn PET short fibers having a dtex (fiber diameter of 4.3 μm) and a fiber length of 3 mm.

[Example 6] Except for 10 parts by mass of stretched PET short fibers with a fineness of 0.1 dtex (fiber diameter of 3.0 μm) and a fiber length of 3 mm, 30 parts by mass of stretched 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 30 parts by mass of stretched PET short fibers with a dtex (fiber diameter of 7.4 μm) and a fiber length of 5 mm, and 30 parts by mass of non-stretched PET staple fibers with a fineness of 0.2 dtex (fiber diameter of 4.3 μm) and a fiber length of 3 mm. 1 In the same manner, a non-woven fabric for electromagnetic wave shielding material with a thickness of 14 μm was produced.

[Example 7] Except 30 parts by mass of stretched PET short fibers with a fineness of 0.3 dtex (fiber diameter of 5.3 μm) and a fiber length of 3 mm, 30 parts by mass of stretched 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 1.7 10 parts by mass of stretched PET short fibers with dtex (fiber diameter 12.0μm) and 5mm fiber length, and 30 parts by mass of unstretched PET short fibers with a fineness of 0.2dtex (fiber diameter 4.3μm) and 3mm fiber length. 1 In the same manner, a non-woven fabric for electromagnetic wave shielding material with a thickness of 16 μm was prepared.

[Example 8] Except for 10 parts by mass of stretched PET short fibers with a fineness of 0.06 dtex (fiber diameter of 2.4 μm) and a fiber length of 3 mm, 30 parts by mass of stretched 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 30 parts by mass of stretched PET short fibers with a dtex (fiber diameter of 7.4 μm) and a fiber length of 5 mm, and 30 parts by mass of non-stretched PET staple fibers with a fineness of 0.2 dtex (fiber diameter of 4.3 μm) and a fiber length of 3 mm. 1 In the same manner, a non-woven fabric for electromagnetic wave shielding material with a thickness of 14 μm was produced.

[Example 9] Except for 30 parts by mass of stretched PET short fibers with a fineness of 0.3 dtex (fiber diameter of 5.3 μm) and a fiber length of 3 mm, 30 parts by mass of stretched 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 0.2 dtex (fiber diameter 4.3μm), fiber length 3mm unstretched PET short fiber 30 mass parts, fineness 1.2dtex (fiber diameter 10.5μm), fiber length 5mm unstretched PET short fiber 10 mass parts other than the system and implementation In the same manner as in Example 1, a non-woven fabric for electromagnetic wave shielding material having a thickness of 16 μm was produced.

[Example 10] Except 15 parts by mass of stretched PET short fibers with a fineness of 0.3 dtex (fiber diameter of 5.3 μm) and a fiber length of 3 mm, 15 parts by mass of stretched 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 0.2 In the same manner as in Example 1, except for 70 parts by mass of undrawn PET short fibers having a dtex (fiber diameter of 4.3 μm) and a fiber length of 3 mm, a nonwoven fabric for electromagnetic wave shielding material having a thickness of 14 μm was produced.

[Comparative Example 1] Except for 30 parts by mass of stretched PET short fibers with a fineness of 0.3 dtex (fiber diameter of 5.3 μm) and a fiber length of 3 mm, 30 parts by mass of stretched 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 1.2 A non-woven fabric for electromagnetic wave shielding material having a thickness of 17 μm was prepared in the same manner as in Example 1 except for 40 parts by mass of undrawn PET short fibers having a dtex (fiber diameter of 10.5 μm) and a fiber length of 5 mm.

[Comparative Example 2] Except for the use of 60 parts by mass of stretched PET short fibers with a fineness of 0.3 dtex (fiber diameter of 5.3 μm) and a fiber length of 3 mm, and 40 parts by mass of undrawn PET staple fibers with a fineness of 0.2 dtex (fiber diameter of 4.3 μm) and a fiber length of 3 mm. In the same manner as in Example 1, a non-woven fabric for electromagnetic wave shielding material having a thickness of 15 μm was produced.

[Comparative Example 3] Except 30 parts by mass of stretched PET short fibers with a fineness of 1.7 dtex (fiber diameter 12.0 μm) and a fiber length of 5 mm, 30 parts by mass of stretched PET short fibers with a fineness of 3.3 dtex (fiber diameter 17.5 μm) and a fiber length of 5 mm and a fineness of 0.2 A non-woven fabric for electromagnetic wave shielding material having a thickness of 21 μm was produced in the same manner as in Example 1 except that 40 parts by mass of undrawn PET short fibers having a dtex (fiber diameter of 4.3 μm) and a fiber length of 3 mm were produced.

[Comparative Example 4] Except that 60 parts by mass of stretched PET short fibers with a fineness of 1.7 dtex (fiber diameter 12.0 μm) and a fiber length of 5 mm and 40 parts by mass of undrawn PET short fibers with a fineness of 0.2 dtex (fiber diameter of 4.3 μm) and a fiber length of 3 mm are used In the same manner as in Example 1, a non-woven fabric for electromagnetic wave shielding material having a thickness of 18 μm was produced.

[Comparative Example 5] Except for 60 parts by mass of stretched PET short fibers with a fineness of 0.1 dtex (fiber diameter of 3.0 μm) and a fiber length of 3 mm, and 40 parts by mass of undrawn PET short fibers with a fineness of 0.2 dtex (fiber diameter of 4.3 μm) and a fiber length of 3 mm are used. In the same manner as in Example 1, a non-woven fabric for electromagnetic wave shielding material having a thickness of 15 μm was produced.

The non-woven fabric for electromagnetic wave shielding materials produced in the examples and comparative examples was coated with a nickel film by an electroless plating method, and then a copper film and a nickel film were sequentially laminated by an electroplating method to prepare an electromagnetic wave shielding material.

＜Assessment＞ [Transportability] The non-woven fabric for electromagnetic wave shielding material is transported under a certain tension, and the wrinkle occurrence at this time is evaluated according to the following criteria.

"○" No wrinkles are generated, and the transportability is excellent. "△" The non-woven fabric for electromagnetic wave shielding material has wrinkles, but there is no problem with the transportability. "×" The whole nonwoven fabric for electromagnetic wave shielding material has so many wrinkles that it cannot be processed, and the transportability is poor.

[Electromagnetic shielding (electric field)] The measurement is based on electromagnetic shielding properties (electric field) based on the coaxial tube method. The frequency range of 40MHz~3GHz is measured by the coaxial tube method 39D, and the frequency range of 500MHz~18GHz is measured by the coaxial tube method GPC7. The frequency of 500MHz~3GHz is measured by the coaxial tube method 39D and the coaxial tube method 7, but the lower value is used.

The higher the numerical value described in the electromagnetic shielding property, the better the electromagnetic shielding property.

Since the non-woven fabrics for electromagnetic wave shielding materials of Examples 1 to 10 contain two or more types 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, and A wet non-woven fabric with non-stretched polyester staple fibers having a fiber diameter of 3 μm to 5 μm as an essential component has excellent transportability and excellent electromagnetic wave shielding properties. The strength of the nonwoven fabric for electromagnetic wave shielding material of Example 4 is slightly lowered, but there is no problem in transportability, and electromagnetic wave shielding properties are also excellent.

On the other hand, it does not contain two or more kinds of stretched polyester staple fibers selected from stretched polyester staple fibers with a fiber diameter of 3 μm or more and less than 12 μm that differ in fiber diameter, and those with a fiber diameter of 3 μm or more and 5 μm or less. The non-woven fabrics for electromagnetic wave shielding materials of Comparative Examples 1, 2, 3, and 4 in which undrawn polyester staple fibers are an essential component have poor electromagnetic wave shielding properties. That is, the non-woven fabric for electromagnetic wave shielding material of Comparative Example 1 in which the fiber diameter of the undrawn polyester staple fiber exceeds 5 μm contains one of two different fiber diameters selected from the stretched polyester staple fiber with a fiber diameter of 12 μm or more. The nonwoven fabric for electromagnetic wave shielding material of Comparative Example 3 of stretched polyester staple fiber, the nonwoven fabric for electromagnetic wave shielding material of Comparative Example 4 where the fiber diameter of stretched polyester staple fiber is 12 μm, and the non-woven fabric for electromagnetic wave shielding material containing fiber diameter of 3 μm or more and less than 12 μm The non-woven fabric for electromagnetic wave shielding material of Comparative Example 2 containing only one type of stretched polyester staple fiber with the same fiber diameter (fiber diameter: 5.3 μm) has been studied to reduce the multiple reflection loss.

In addition, it contains stretched polyester staple fibers with a fiber diameter of 3 μm or more and less than 12 μm, but only contains one type of stretched polyester staple fiber (fiber diameter 3.0 μm) with the same fiber diameter for the electromagnetic wave shielding material of Comparative Example 5 The non-woven fabric has wrinkles when the screen is transported, and the transportability is poor. Since it only contains stretched polyester staple fibers with a small fiber diameter, the screen will become softer and easier to stretch and wrinkles are likely to occur.

≪Non-woven fabric for electromagnetic wave shielding material of the present invention <2> Related Examples≫

＜Assessment＞ (1) Surface resistance value Measured based on MIL DTL 83528C.

(2) Electromagnetic wave shielding (electric field) The measurement is based on electromagnetic shielding properties (electric field) based on the coaxial tube method. The frequency range of 40MHz~3GHz is measured by the coaxial tube method 39D, and the frequency range of 500MHz~18GHz is measured by the coaxial tube method GPC7. The frequency of 500MHz~3GHz is measured by the coaxial tube method 39D and the coaxial tube method GPC7, but the lower value is used.

(3) Peel evaluation A tape (Nitto (registered trademark) 31B Tape, manufactured by Nitto Denko Co., Ltd.) was applied to an electromagnetic wave shielding material sample of 25 mm in width × 150 mm in length, and rolled 10 times with a 2 kg roller at a speed of 300 mm/min. After that, the tape and the sample were at an angle of 180 degrees and peeled at a speed of 1000 mm/min. The evaluation is based on the following criteria.

<Benchmark> ○: The measurement was performed 3 times, and there was no sample fracture or metal powder adhered to the tape. △: The measurement was performed 3 times, and the sample was broken and metal powder adhered to the tape 1 to 2 times. ×: The measurement was performed 3 times, and the sample fracture and metal powder adhered to the tape occurred 3 times.

[Example 11] 20 parts by mass of stretched polyethylene terephthalate (PET) staple fiber with a fineness of 0.06 dtex (fiber diameter of 2.4 μm) and a fiber length of 3 mm, a fineness of 0.3 dtex (fiber diameter of 5.3 μm), and a fiber 40 parts by mass of stretched PET staple fiber with a length of 3mm, a single-component type bonding non-stretched PET staple fiber with a fineness of 0.2dtex (fiber diameter of 4.3μm) and a fiber length of 3mm are prepared by dispersing in water by a pulper. A uniform papermaking slurry with a concentration of 1% by mass. The slurry for papermaking is lifted up by the wet method with an inclined paper machine equipped with an air permeability of 275cm ³ /cm ² /sec and a tissue [Internet: plain weave, lower mesh: striped weave]. By using a drum dryer at 135°C, non-stretched PET short fibers for thermal fusion bonding are used to develop strength to produce a wet non-woven fabric. Furthermore, this wet-type non-woven fabric was treated with a single-roll type hot calendering device composed of a dielectric heating jacket roll (metal heat roll) and an elastic roll. The heat roll temperature was 200°C, the linear pressure was 100kN/m, and the The hot calendering process was performed at a speed of 100 m/min, and a non-woven fabric for electromagnetic wave shielding material having a basis weight of 6.5 g/m ² and a density of 0.50 g/cm ³ was produced.

Next, the non-woven fabric for the electromagnetic wave shielding material was coated with a nickel film by electroless plating. Next, a copper film and a nickel film were sequentially laminated by electroplating, and the metal film was processed to obtain a thickness of 17.5 μm. Electromagnetic wave shielding material.

[Example 12] Except that the fiber formulation was set to 40 parts by mass of stretched PET short fibers with a fineness of 0.06 dtex (fiber diameter of 2.4 μm) and a fiber length of 3 mm, a fineness of 0.3 dtex (fiber diameter of 3.0 μm), and a stretched PET of 3 mm in length. A wet nonwoven fabric was obtained in the same manner as in Example 11 except that 20 parts by mass of short fibers and 40 parts by mass of unstretched PET short fibers for single-component bonding with a fineness of 0.2 dtex (fiber diameter: 4.3 μm) and a fiber length of 3 mm were obtained. . This wet-type nonwoven fabric was subjected to hot calendering treatment in the same manner as in Example 11 except that the processing speed was set to 50 m/min, to obtain a basis weight of 6.5 g/m ² and a density of 0.63 g/cm ³ Non-woven fabric for electromagnetic wave shielding material. Next, the metal film treatment was performed in the same manner as in Example 11 to obtain an electromagnetic wave shielding material having a thickness of 16.0 μm.

[Example 13] The fiber formulation was set to a single component of 60 parts by mass of stretched 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 0.2 dtex (fiber diameter of 4.3 μm) and a fiber length of 3 mm. The wet type nonwoven fabric was obtained in the same manner as in Example 11 except that 40 parts by mass of the non-stretched PET short fibers for type bonding were obtained. This wet-type nonwoven fabric was subjected to hot calendering treatment in the same manner as in Example 11, except that the linear pressure was 125 kN/m and the processing speed was 40 m/min. The basis weight was 6.5 g/m ² and the density 0.80g/cm ³ non-woven fabric for electromagnetic wave shielding material. Next, the metal film treatment was performed in the same manner as in Example 11 to obtain an electromagnetic wave shielding material having a thickness of 15.5 μm.

[Example 14] A wet type 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-type nonwoven fabric was subjected to a hot calendering treatment in the same manner as in Example 13 to prepare a nonwoven fabric for electromagnetic wave shielding material with a density of 0.80 g/cm ³ . Next, the aforementioned non-woven fabric for electromagnetic wave shielding material was coated with a nickel film by sputtering treatment, copper film and nickel film were sequentially laminated by electroplating treatment, and metal film treatment was performed to obtain an electromagnetic wave shielding material with a thickness of 8.5 μm.

[Example 15] A wet type 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-type nonwoven fabric was subjected to a hot calendering treatment in the same manner as in Example 11 to prepare a nonwoven fabric for electromagnetic wave shielding material with a density of 0.50 g/cm ³ . Next, the aforementioned non-woven fabric for electromagnetic wave shielding material was subjected to a metal coating treatment in the same manner as in Example 14 to obtain an electromagnetic wave shielding material having a thickness of 12.0 μm.

[Example 16] A wet type 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-type nonwoven fabric was subjected to a hot calendering treatment in the same manner as in Example 12 to prepare a nonwoven fabric for electromagnetic wave shielding material with a density of 0.63 g/cm ³ . Next, the metal film treatment was performed in the same manner as in Example 14 to obtain an electromagnetic wave shielding material having a thickness of 10.0 μm.

[Comparative Example 11] Except that the fiber formulation was set to a single component of 60 parts by mass of stretched PET short fibers with a fineness of 0.3 dtex (fiber diameter of 5.3 μm) and a fiber length of 5 mm and a fineness of 1.2 dtex (fiber diameter of 10.7 μm) and a fiber length of 5 mm In the same manner as in Example 11, except for 40 parts by mass of undrawn PET short fibers for type bonding, a wet nonwoven fabric with a basis weight of 10.0 g/m ² was obtained. This wet-type nonwoven fabric was subjected to hot calendering treatment in the same manner as in Example 11, except that the line pressure was 135kN/m and the processing speed was 40m/min. The electromagnetic wave shielding density was 0.85g/cm ³ . The material is made of non-woven fabric. Next, the metal film treatment was performed in the same manner as in Example 14 to obtain an electromagnetic wave shielding material having a thickness of 16.0 μm.

[Comparative Example 12] Except that the linear pressure was 100 kN/m and the processing speed was 50 m/min, an electromagnetic wave 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. Non-woven fabric is used for the shielding material. Next, a metal film treatment was performed in the same manner as in Comparative Example 11 to obtain an electromagnetic wave shielding material having a thickness of 20.0 μm.

[Comparative Example 13] Except for setting the linear pressure of 90 kN/m and the processing speed of 100 m/min, an electromagnetic wave 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. Non-woven fabric is used for the shielding material. Next, a metal film treatment was performed in the same manner as in Comparative Example 11 to obtain an electromagnetic wave shielding material having a thickness of 26.0 μm.

[Comparative Example 14] In the same manner as in Comparative Example 11, a non-woven fabric for electromagnetic wave shielding material having a basis weight of 10.0 g/m ² and a density of 0.85 g/cm ³ was produced. Next, the metal film treatment was performed in the same manner as in Example 11 to obtain an electromagnetic wave shielding material having a thickness of 16.0 μm.

[Comparative Example 15] In the same manner as in Comparative Example 12, a non-woven fabric for electromagnetic wave shielding material having a basis weight of 10.0 g/m ² and a density of 0.63 g/cm ³ was produced. Next, the metal film treatment was performed in the same manner as in Comparative Example 14 to obtain an electromagnetic wave shielding material having a thickness of 20.0 μm.

[Comparative Example 16] In the same manner as in Comparative Example 13, a non-woven fabric for electromagnetic wave shielding material having a basis weight of 10.0 g/m ² and a density of 0.45 g/cm ³ was produced. Next, the metal film treatment was performed in the same manner as in Comparative Example 14 to obtain an electromagnetic wave shielding material having a thickness of 26.0 μm.

Containing stretched polyester staple fibers with a fiber diameter of less than 3μm and unstretched polyester staple fibers with a fiber diameter of 3μm to 5μm as essential components, with a basis weight of 7g/m ² or less and a density of 0.5~0.8g/ cm ³ is the electromagnetic wave shielding material of wet non-woven fabric. Examples 11 to 16 of the electromagnetic wave shielding material made of non-woven fabric treated with metal film have excellent electromagnetic wave shielding properties and can achieve the effect of preventing the metal film from peeling off. In addition, the metal film treatment sequentially includes the treatment of forming a nickel coating by sputtering, the treatment of forming a copper coating by electroplating, and the treatment of forming a nickel coating by electroplating. The thickness is 15μm or less and the surface resistance value is Compared with the electromagnetic wave shielding materials of Examples 11-13, the electromagnetic wave shielding materials of Examples 14 to 16 having a value of 0.03Ω/□ or less have superior electromagnetic wave shielding properties, and it can be seen that the metal film is less likely to peel off.

Comparative Examples 11 to 16 are non-woven fabrics for electromagnetic wave shielding materials containing stretched PET short fibers with a fiber diameter of 3 μm or more and undrawn PET short fibers with a fiber diameter of more than 5 μm, and a basis weight of more than 7 g/m ² which is a wet non-woven fabric Electromagnetic wave shielding material made of metal coating. Regarding the metal coating treatments in this order, including the treatment of forming a nickel coating by sputtering, the treatment of forming a copper coating by electroplating, and the treatment of forming a nickel coating by electroplating, Comparative Examples 11 and 13, the electromagnetic wave shielding The results of the evaluation of properties and peeling were poor. Although the electromagnetic wave shielding material of Comparative Example 12 had good electromagnetic wave shielding properties and peeling evaluation, the thickness of the electromagnetic wave shielding material was 20.0 μm, and it was not possible to reduce the thickness. For Comparative Examples 14 to 16, the nickel film was coated by electroless plating, and the copper film and the nickel film were sequentially laminated by electroplating, and the metal film was processed. The peeling evaluation results were good, but electromagnetic waves Poor shading.

≪Non-woven fabric for electromagnetic wave shielding material of the present invention <3> Related Examples≫

[Example 21] 30 parts by mass of stretched polyethylene terephthalate (PET) staple fiber with a fineness of 0.6 dtex (fiber diameter 7.4 μm) and a fiber length of 5 mm, a fineness of 0.3 dtex (fiber diameter 5.3 μm), and a fiber 30 parts by mass of stretched PET short fibers with a length of 3 mm and a fineness of 0.2 dtex (fiber diameter: 4.3 μm), a fiber length of 3 mm, and 40 parts by mass of unstretched PET staple fibers for single-component bonding with a melting point of 246°C are dispersed by a pulper In water, prepare a uniform papermaking slurry with a concentration of 1% by mass. The slurry for papermaking is lifted up by the wet method with an inclined paper machine equipped with a papermaking net with air permeability of 275cm ³ /cm ² /sec and weave [online: plain weave, lower net: striped weave]. By using a drum dryer at 135°C, unstretched PET short fibers for thermal fusion bonding were used to develop strength to produce a wet non-woven fabric with a basis weight of 10 g/m ² . Furthermore, this wet-type non-woven fabric was treated with a single-roll type hot calendering device composed of a dielectric heating jacket roll (metal heat roll) and an elastic roll. The hot roll temperature was 202°C, the linear pressure was 100kN/m, and the The hot calendering process was performed at a speed of 40 m/min, and a non-woven fabric for electromagnetic wave shielding material having a thickness of 15 μm and a peel strength of 2.1 N/m was produced.

[Example 22] A non-woven fabric for electromagnetic wave shielding material having a thickness of 15 μm and a peel strength of 3.1 N/m was produced in the same manner as in Example 21 except that the temperature of the heat roller was 208°C.

[Example 23] A nonwoven fabric for electromagnetic wave shielding material having a thickness of 15 μm and a peel strength of 4.2 N/m was produced in the same manner as in Example 21 except that the temperature of the heat roller was 205°C.

[Example 24] Except that the formulation of the stretched polyester staple fiber is set to a fineness of 0.6 dtex (fiber diameter 7.4 μm), 30 parts by mass of stretched PET staple fiber with a fiber length of 3 mm, and a stretch of 0.1 dtex (fiber diameter of 3.0 μm) and a fiber length of 3 mm. A non-woven fabric for electromagnetic wave shielding material having a thickness of 15 μm and a peel strength of 3.5 N/m was produced in the same manner as in Example 23 except for 30 parts by mass of PET short fibers.

[Example 25] Except that the formulation of the stretched polyester staple fiber is set to be 0.6 dtex (fiber diameter 7.4 μm), 30 parts by mass of stretched PET staple fiber with a fiber length of 3 mm, and a stretch of 0.06 dtex (fiber diameter of 2.4 μm) and a fiber length of 3 mm. A non-woven fabric for electromagnetic wave shielding material having a thickness of 15 μm and a peel strength of 3.7 N/m was prepared in the same manner as in Example 23 except for 30 parts by mass of PET short fibers.

[Example 26] Except that the formulation of the stretched polyester staple fiber is set to 0.3 dtex (fiber diameter 5.3 μm), 30 parts by mass of stretched PET staple fiber with a fiber length of 3 mm, and a stretch of 0.1 dtex (fiber diameter of 3.0 μm) and a fiber length of 3 mm. A non-woven fabric for electromagnetic wave shielding material 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 except for 30 parts by mass of PET-based short fibers.

[Example 27] Except that the formulation of the stretched polyester staple fiber is set to 0.3 dtex (fiber diameter 5.3 μm), 30 parts by mass of stretched PET staple fiber with a fiber length of 3 mm, and a stretch of 0.06 dtex (fiber diameter of 2.4 μm) and a fiber length of 3 mm. A non-woven fabric for electromagnetic wave shielding material having a thickness of 15 μm and a peel strength of 3.3 N/m was prepared in the same manner as in Example 23 except for 30 parts by mass of PET short fibers.

[Example 28] Except that the formulation of the stretched polyester staple fiber is set to a fineness of 0.1 dtex (fiber diameter 3.0 μm), 30 parts by mass of stretched PET staple fiber with a fiber length of 3 mm, and a stretch of 0.06 dtex (fiber diameter of 2.4 μm) and a fiber length of 3 mm. A non-woven fabric for electromagnetic wave shielding material having a thickness of 15 μm and a peel strength of 3.5 N/m was produced in the same manner as in Example 23 except for 30 parts by mass of PET short fibers.

[Comparative Example 21] A non-woven fabric for electromagnetic wave shielding material having a thickness of 15 μm and a peel strength of 1.8 N/m was produced in the same manner as in Example 21 except that the heat roller temperature was 198°C.

[Comparative Example 22] A non-woven fabric for electromagnetic wave shielding material having a thickness of 15 μm and a peel strength of 1.0 N/m was produced in the same manner as in Example 21 except that the temperature of the heat roller was 195°C.

[Comparative Example 23] A non-woven fabric for electromagnetic wave shielding material having a thickness of 15 μm and a peel strength of 1.5 N/m was produced in the same manner as in Example 24 except that the heat roller temperature was 198°C.

[Comparative Example 24] A non-woven fabric for electromagnetic wave shielding material having a thickness of 15 μm and a peel strength of 1.0 N/m was produced in the same manner as in Example 25 except that the heat roller temperature was set to 198°C.

[Comparative Example 25] Except that the fiber formulation is set to 30 parts by mass of stretched PET short fibers with a fineness of 0.6 dtex (fiber diameter 7.4 μm) and a fiber length of 3 mm, a fineness of 0.3 dtex (fiber diameter 5.3 μm), and 30 parts by weight of stretched PET short fibers with a fiber length of 3 mm. 30 parts by mass, fineness 0.1dtex (fiber diameter 3.0μm), 30 mass parts of stretched PET short fiber with fiber length 3mm, and single-component bonding material with fineness 0.2dtex (fiber diameter 4.3μm), fiber length 3mm, and melting point of 246°C Except for 10 parts by mass of the stretched PET short fibers, a non-woven fabric for electromagnetic wave shielding material having a thickness of 15 μm and a peel strength of 0.2 N/m was produced in the same manner as in Example 23.

[Comparative Example 26] Except that the fiber formulation is set to a single component with a fineness of 0.6 dtex (fiber diameter: 7.4μm), 10 parts by mass of stretched PET short fibers with a fiber length of 3mm, and a single component with a fineness of 0.2dtex (fiber diameter of 4.3μm), fiber length of 3mm, and melting point of 246°C A non-woven fabric for electromagnetic wave shielding material having a thickness of 15 μm and a peel strength of 1.8 N/m was prepared in the same manner as in Example 23 except for 90 parts by mass of the undrawn PET short fibers for type bonding.

The non-woven fabrics for electromagnetic wave shielding materials produced in the examples and comparative examples were subjected to alkali treatment before plating, and copper and nickel metal plating treatments were performed by electroless plating to prepare electromagnetic wave shielding materials.

<Assessment> [Peel strength] Cut the electromagnetic wave shielding material into 25mm×200mm non-woven fabric, and stick the double-sided tape (manufactured by NICHIBAN, trade name: NW-R25, Nicetack (registered trademark) low adhesion type) on the backing paper (Mitsubishi) Made of paper, trade name: N Pearl Card (registered trademark) FSC certified-MX (450.0g/m ² )) non-glossy surface, superimposed on the non-woven fabric for electromagnetic wave shielding material, and pasted packaging tape (KAMOI Industrial system, trade name: No. 220W), and perform a peel test as shown in Figure 1 to measure the peel strength. The peeling test is made by SHIMPO (NIDEC-SHIMPO). The name of the device: Digital Tensile Gauge FGC-2B. Set the distance between the clamps to 1.8cm, and place the non-woven fabric for electromagnetic wave shielding material at the center of the distance at a speed of 100mm/min. Perform the measurement.

[Fiber shedding resistance] Adopt the non-woven fabric for electromagnetic wave shielding material, cut into 25mm×200mm, use the Academic Promotion Association type friction fastness tester, use the Billiken Mos (registered trademark) cloth with a load of 500gf to rub the electromagnetic wave shielding material with non-woven fabric back and forth 5 times, according to The following criteria are used for evaluation.

"◎" There is no fiber attached to the Billiken Mos cloth. "○" There is almost no fiber attached to the Billiken Mos cloth. "△" Although there are some fibers attached to the Billiken Mos cloth, there is no problem in practical use. "×" Billiken Mos cloth adheres to fibers, and the substrate breaks in some cases.

[Defect Frequency] Check the frequency of defects per 1000 m when metal plating is performed on the non-woven fabric for electromagnetic wave shielding material that has been subjected to the alkali treatment before plating.

"◎" 0 pcs/1000m. "○" 1 piece/1000m. "△" 2 pcs/1000m. "×" 3 or more/1000m.

[Electromagnetic shielding (electric field)] The measurement is based on electromagnetic shielding properties (electric field) based on the coaxial tube method. The frequency range of 40MHz~3GHz is measured by the coaxial tube method 39D, and the frequency range of 500MHz~18GHz is measured by the coaxial tube method GPC7. The frequency of 500MHz~3GHz is measured by the coaxial tube method 39D and the coaxial tube method 7, but the lower value is used.

The higher the numerical value described in the electromagnetic shielding property, the better the electromagnetic shielding property.

Compared with the non-woven fabrics for electromagnetic wave shielding materials of Examples 21 to 28, the non-woven fabrics for electromagnetic wave shielding materials of Comparative Examples 21 to 26 have higher peel strength, excellent fiber shedding resistance, and less defect frequency, and the yield rate is also high. Good and exhibit excellent electromagnetic wave shielding properties.

Comparing Examples 21 to 23, Example 23 with a heat roll temperature of 205°C has the highest peel strength and improved fiber shedding resistance. On the other hand, in Comparative Examples 21 to 24, since the heat roller temperature is lower than 200°C, the nonwoven fabric for electromagnetic wave shielding material has low peel strength, poor fiber shedding resistance, and extremely high frequency of defects.

As for Comparative Examples 25 and 26, the content of undrawn polyester staple fibers did not reach 20% by mass or more than 80% by mass of the total fiber constituting the nonwoven fabric for electromagnetic wave shielding material, which deviated from the preferred range, even though the heat roller temperature was 205 °C is a preferable range, but it is still a non-woven fabric for electromagnetic wave shielding material with low peel strength and poor fiber shedding resistance. [Industrial availability]

The non-woven 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, electrical appliances, and the like. Such equipment or products include equipment such as mobile phones, smart phones, cell phones, personal computers, mobile devices, or housings for storing such equipment, televisions or washing machines and other electrical appliances. In particular, the electromagnetic wave shielding material of the present invention can be suitably used by being fixed to a plastic shell, a flexible printed circuit board, a cable, a connector cable, etc. by bonding, crimping, welding, winding, etc.

Fig. 1 is a schematic view showing the state of the non-woven fabric for electromagnetic wave shielding material when the peel strength is measured.

Claims (7)

A non-woven fabric for electromagnetic wave shielding material, which is a wet-type non-woven fabric, characterized in that: the wet-type non-woven fabric contains two or more types of stretches selected from stretched polyester staple fibers with a fiber diameter of 3 μm or more and less than 12 μm with different fiber diameters Polyester staple fibers and undrawn polyester staple fibers with a fiber diameter of 3 μm or more and 5 μm or less are essential components. A non-woven fabric for electromagnetic wave shielding material, which is a wet non-woven fabric, characterized in that it 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 to 5 μm as essential components , The basis weight is 7g/m ² or less and the density is 0.5~0.8g/cm ³ . A non-woven fabric for electromagnetic wave shielding material, which is a wet non-woven fabric, characterized in that it contains stretched polyester staple fibers and unstretched polyester staple fibers with a melting point of 220°C or more and 250°C or less, and the peel strength of the non-woven fabric ( Longitudinal) is 2.0 N/m or more. An electromagnetic wave shielding material, characterized in that the electromagnetic wave shielding material according to any one of Claims 1 to 3 is processed with a metal film with a non-woven fabric. Such as the electromagnetic wave shielding material of claim 4, wherein the metal film treatment is one or more treatments selected from the group consisting of electroless metal plating treatment, electroplating treatment, metal evaporation treatment and sputtering treatment. The electromagnetic wave shielding material of claim 4, wherein the metal film treatment includes, in order, 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 . Such as the electromagnetic wave shielding material of any one of claims 4 to 6, wherein the thickness of the electromagnetic wave shielding material is 15μm or less, and the surface resistance of the electromagnetic wave shielding material is 0.03Ω/□ or less.

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