JP2020167375A - Non-woven fabric for electromagnetic wave shielding material and electromagnetic wave shielding material - Google Patents

Abstract

To provide a non-woven fabric base material for an electromagnetic wave shielding material and an electromagnetic wave shielding material, capable of exhibiting excellent electromagnetic wave shielding properties.SOLUTION: A nonwoven fabric for electromagnetic wave shielding material is a wet nonwoven 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 or more and 5 μm or less, with a mesh density of 7 g/m2 or less and a density of 0.5 to 0.8 g/cm3. The nonwoven fabric for electromagnetic wave shielding material also contains stretched polyester short fibers and unstretched polyester short fibers having a melting point of 220°C or more and 250°C or less and has a peel strength (longitudinal) of 2.0 N/m or more.SELECTED DRAWING: Figure 1

Description

The present invention relates to a non-woven fabric for an electromagnetic wave shielding material and an electromagnetic wave shielding material capable of exhibiting excellent electromagnetic wave shielding properties while having excellent web transportability.

Electronic devices generate electromagnetic waves. Then, an electromagnetic wave shielding material is used in order to prevent the electromagnetic wave from leaking to the outside of the electronic device and to prevent the electronic device from malfunctioning due to the electromagnetic wave. Examples of the electromagnetic wave shielding material include sheet metal, paint containing metal, metal mesh, foamed metal and the like. Further, an electromagnetic wave shielding material obtained by subjecting a non-woven fabric made of polyester-based short fibers to a metal plating treatment is disclosed (see, for example, Patent Documents 1 and 2).

Patent Document 1 discloses an electromagnetic wave shielding material in which a continuous metal conductive layer is attached to the outer periphery of a non-woven fabric, knitted fabric, or non-woven fabric fiber and the entire circumference of a crossed portion by a wet plating method. It is described that polyester fibers and polypropylene fibers are preferable as chemical fibers because they have excellent tensile strength and elongation characteristics of the base material itself and can prevent deterioration of the characteristics in the plating pretreatment step.

Patent Document 2 describes an electromagnetic wave shielding material obtained by subjecting a wet non-woven fabric to a metal film treatment, containing polyester fibers having a single fiber fineness of 1.1 dtex or less, and having a thickness in the range of 10 to 30 μm. An electromagnetic wave shielding material characterized by the above is disclosed.

With the recent miniaturization, high frequency, and high performance of electronic devices, there is a demand for thinner and higher electromagnetic wave shielding materials. Specifically, there is a demand for 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.

When a metal film treatment such as metal plating is applied to a non-woven fabric as in Patent Documents 1 and 2, the non-woven fabric is processed by roll-to-roll with good productivity, but wrinkles occur in the non-woven fabric during transportation. There was a problem that the transportability was not excellent.

Further, in the example of Patent Document 2, a polyester drawn fiber having a single fiber fineness of 0.1 dtex and an undrawn binder fiber having a single fiber fineness of 0.2 dtex are included, and the base paper texture of the wet non-woven fabric is 8 g / m ² . , An electromagnetic wave shielding material having a grain size of 19 g / m ² and a thickness of 12 μm is disclosed. However, as a thin electromagnetic wave shielding material is required, there is a problem that the electromagnetic wave shielding material of Patent Document 2 cannot sufficiently secure the electromagnetic wave shielding property. In addition, there may be a problem that the metal film is peeled off.

Further, in the electromagnetic wave shielding material in which the non-woven fabric is metal-plated, it is required that the polyester-based short fibers and the metal film formed by the metal plating are in close contact with each other. Therefore, as a pre-plating step, polyester is required. It is known that short fibers are subjected to alkali treatment.

Patent Document 1 describes that polyester fibers can prevent deterioration of characteristics in the plating pretreatment step. However, the alkaline treatment of the non-woven fabric is usually a wet treatment, and the fibers may fall off in the water tank, which may significantly reduce the operability. In addition, the fallen fibers may reattach to the non-woven fabric, causing a problem that defects occur in the metal plating process.

Jitsukaisho 48-40800 Japanese Unexamined Patent Publication No. 2014-75485

A first object of the present invention is to provide a non-woven fabric for an electromagnetic wave shielding material which is excellent in transportability and can exhibit excellent electromagnetic wave shielding property, and an electromagnetic wave shielding material using the non-woven fabric for the electromagnetic wave shielding material.

A second object of the present invention is to provide a non-woven fabric for an electromagnetic wave shielding material which is thin and can exhibit excellent electromagnetic wave shielding properties and whose metal film is hard to peel off, and an electromagnetic wave shielding material using the non-woven fabric for the electromagnetic wave shielding material. is there.

A third object of the present invention is an electromagnetic wave shielding material non-woven fabric having less fiber loss and high strength in the alkali treatment, which is a plating pretreatment step for the electromagnetic wave shielding material, and an electromagnetic wave shielding using the electromagnetic wave shielding material non-woven fabric. It is to provide materials.

As a result of diligent research to solve the above problems, the present inventors have found the following inventions.

<1> In the non-woven fabric for electromagnetic wave shielding material which is a wet non-woven fabric, the wet non-woven fabric is selected from stretched polyester short fibers having a fiber diameter of 3 μm or more and less than 12 μm, and two or more kinds of stretched polyester short fibers having different fiber diameters. A non-woven fabric for an electromagnetic wave shielding material, which contains unstretched polyester-based short fibers having a fiber diameter of 3 μm or more and 5 μm or less as an essential component.

<2> A non-woven fabric for electromagnetic wave shielding material, which is a wet non-woven fabric, contains drawn polyester short fibers having a fiber diameter of less than 3 μm and unstretched polyester short fibers having a fiber diameter of 3 μm or more and 5 μm or less as essential components, and has a texture of 7 g / A non-woven fabric for an electromagnetic wave shielding material, which is m ² or less and has a density of 0.5 to 0.8 g / cm ³ .

<3> The non-woven fabric for electromagnetic wave shielding material, which is a wet non-woven fabric, contains stretched polyester-based short fibers and unstretched polyester-based short fibers having a melting point of 220 ° C. or higher and 250 ° C. or lower, and the peeling strength (longitudinal direction) of the non-woven fabric is 2. A non-woven fabric for electromagnetic wave shielding material, which is characterized by having a concentration of 0.0 N / m or more.

<4> The electromagnetic wave shielding material according to any one of <1> to <3> above, wherein the non-woven fabric for the electromagnetic wave shielding material is treated with a metal film.

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

<6> The above-mentioned <4>, wherein the metal film 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. Electroplating shield material.

<7> The electromagnetic wave shielding material according to any one of <4> to <6> above, 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 0.03Ω / □ or less.

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

The second effect of the present invention is to provide a non-woven fabric for an electromagnetic wave shielding material which is thin and can exhibit excellent electromagnetic wave shielding properties and whose metal film is hard to peel off, and an electromagnetic wave shielding material using the non-woven fabric for the electromagnetic wave shielding material. ..

The third effect of the present invention is that in the alkali treatment, which is a plating pretreatment step for the electromagnetic wave shielding material, the non-woven fabric for the electromagnetic wave shielding material having less fiber loss and high strength, and the electromagnetic wave shielding using the non-woven fabric for the electromagnetic wave shielding material. It is possible to provide materials.

The schematic diagram which showed the state of the non-woven fabric for an electromagnetic wave shielding material at the time of measuring the peel strength.

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

-Non-woven fabric for electromagnetic wave shielding material <1>-
The non-woven fabric <1> for electromagnetic shielding material of the present invention is selected from drawn polyester short fibers having a fiber diameter of 3 μm or more and less than 12 μm, and two or more kinds of drawn polyester short fibers having different fiber diameters and a fiber diameter of 3 μm or more. It is a wet non-woven fabric containing unstretched polyester-based short fibers of 5 μm or less as an essential component.

In general, the non-woven fabric during transport in roll-to-roll processing is tensioned in the MD (Machine Direction) direction, so that the non-woven fabric is stretched, which causes wrinkles. The non-woven fabric for electromagnetic wave shielding material <1> of the present invention comprises two or more kinds of stretched polyester short 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, and a fiber diameter of 3 μm. Since it contains unstretched polyester-based short fibers of 5 μm or less as an essential component, it is selected from drawn polyester-based short fibers having a fiber diameter of 3 μm or more and less than 12 μm with one type of drawn polyester-based short fibers having the same fiber diameter. Compared with a non-woven fabric containing unstretched polyester-based short fibers having a fiber diameter of 3 μm or more and 5 μm or less as an essential component, it is less likely to stretch and therefore less likely to wrinkle during transportation. Further, when a non-woven fabric having a large fiber diameter of 12 μm or more of the drawn polyester-based short fibers is used, it is difficult to obtain a thin electromagnetic wave shielding material. The non-woven fabric for electromagnetic wave shielding material <1> of the present invention is thin and has a transportability by containing drawn polyester short fibers having a fiber diameter of less than 12 μm and undrawn polyester short fibers having a fiber diameter of 3 μm or more and 5 μm or less. The effect of being excellent can be achieved.

Generally, electromagnetic wave shielding property is achieved by absorption / reflection loss, reflection loss, and multiple reflection loss of electromagnetic waves. In the non-woven fabric for electromagnetic wave shielding material <1> of the present invention, electromagnetic waves are obtained by using two or more kinds of stretched polyester short 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. The electromagnetic waves that have entered the shield material are easily reflected repeatedly in the electromagnetic wave shield material, and excellent electromagnetic wave shielding properties can be obtained by improving the multiple reflection loss.

In the non-woven fabric for electromagnetic wave shielding material <1> of the present invention, the mass content ratio of the stretched polyester-based short fibers and the unstretched polyester-based short fibers is preferably 10:90 to 90:10, preferably 20:80 to 80: 10. It is more preferably 20 and even more preferably 30:70 to 70:30. If the content of the unstretched polyester-based short fibers is less than 10% by mass of the total fibers constituting the wet non-woven fabric, the strength required for the non-woven fabric for the electromagnetic wave shielding material may not be exhibited. On the other hand, if the content of the unstretched polyester-based short fibers exceeds 90% by mass, the uniformity may be impaired.

In the non-woven fabric <1> for electromagnetic wave shielding material of the present invention, stretched polyester-based short fibers other than stretched polyester-based short fibers having a fiber diameter of 3 μm or more and less than 12 μm may be used. Further, unstretched polyester-based short fibers other than unstretched polyester-based short fibers having a fiber diameter of 3 μm or more and 5 μm or less may be used. That is, drawn polyester-based short fibers having a fiber diameter of less than 3 μm, drawn polyester-based short fibers having a fiber diameter of 12 μm or more, unstretched polyester-based short fibers having a fiber diameter of less than 3 μm, and undrawn polyester-based short fibers having a fiber diameter of more than 5 μm. Fiber may be used. These may be used alone or in combination with fibers having two or more kinds of fiber diameters.

In the non-woven fabric for electromagnetic wave shielding material <1> of the present invention, the mass content of the drawn polyester-based short fibers having a fiber diameter of 3 μm or more and less than 12 μm is 1 to 100% by mass in the total stretched polyester-based short fibers contained. It is preferably 3 to 100% by mass, and more preferably 3 to 100% by mass. When the content of the drawn polyester short fibers having a fiber diameter of 3 μm or more and less than 12 μm is less than 1% by mass in the fully drawn polyester short fibers, a thin electromagnetic wave shielding material having excellent transportability may not be obtained. ..

Further, in the non-woven fabric <1> for electromagnetic wave shielding material of the present invention, the mass content of unstretched polyester-based short fibers having a fiber diameter of 3 μm or more and 5 μm or less is 1 among all unstretched polyester-based short fibers contained. ~ 100% by mass is preferable, and 2 to 100% by mass is more preferable. When the content of undrawn polyester short fibers having a fiber diameter of 3 μm or more and 5 μm or less is less than 1% by mass, the specific surface area may become small depending on the fiber diameter used in combination, and it may be difficult to exhibit excellent electromagnetic wave shielding properties. is there. In addition, it may be difficult to develop the strength of the wet non-woven fabric.

The thickness of the non-woven fabric <1> for an electromagnetic wave shielding material of the present invention is preferably 7 to 30 μm, more preferably 15 μm or less, for the purpose of being used in an electronic device. Basis weight (basis weight) is preferably from 5 to 30 g / ^{m 2,} and more preferably 15 g / ^{m 2} or less. If the basis weight is less than 5 g / m ² , it becomes difficult to obtain uniformity, and the effect of the electromagnetic wave shielding property tends to vary.

-Non-woven fabric for electromagnetic wave shielding material <2>-
The non-woven fabric <2> for electromagnetic shielding material of the present invention contains drawn polyester short fibers having a fiber diameter of less than 3 μm and unstretched polyester short fibers having a fiber diameter of 3 μm or more and 5 μm or less as essential components, and has a texture of 7 g / m. It is a wet non-woven fabric having a density of ² or less and a density of 0.5 to 0.8 g / cm ³ .

Generally, in the treatment of a metal film on a wet non-woven fabric, if the specific surface area (surface area per unit volume) of the fibers forming the wet non-woven fabric is small, the amount of metal adhered per unit volume is small, and excellent electromagnetic shielding properties are obtained. It may not be expressed. The non-woven fabric for electromagnetic wave shielding material <2> of the present invention is a wet non-woven fabric containing stretched polyester short fibers having a fiber diameter of less than 3 μm and unstretched polyester short fibers having a fiber diameter of 3 μm or more and 5 μm or less as essential components. Therefore, the specific surface area can be increased, and excellent electromagnetic shielding properties can be exhibited. When the wet non-woven fabric is composed of only drawn polyester-based short fibers having a fiber diameter of 3 μm or more and unstretched polyester-based short fibers having a fiber diameter of more than 5 μm, excellent electromagnetic wave shielding properties cannot be exhibited. It is difficult to obtain undrawn polyester short fibers having a fiber diameter of less than 3 μm. Further, the fiber diameter of the drawn polyester-based short fiber having a fiber diameter of less than 3 μm is preferably 0.1 μm or more. If the fiber diameter is less than 0.1 μm, the strength may not be exhibited.

In the non-woven fabric for electromagnetic wave shielding material <2> of the present invention, the mass content ratio of the stretched polyester-based short fibers and the unstretched polyester-based short fibers is preferably 20:80 to 80:20, preferably 30:70 to 70:20. It is more preferably 30 and even more preferably 40:60 to 60:40. If the content of the unstretched polyester-based short fibers is less than 20% by mass of the total fibers constituting the wet non-woven fabric, the strength required for the non-woven fabric for the electromagnetic wave shielding material may not be exhibited. On the other hand, if the content of the unstretched polyester-based short fibers exceeds 80% by mass, the uniformity may be impaired.

In the non-woven fabric for electromagnetic wave shielding material <2> of the present invention, fibers other than drawn polyester short fibers having a fiber diameter of less than 3 μm and undrawn polyester short fibers having a fiber diameter of 3 μm or more and 5 μm or less may be used. That is, drawn polyester-based short fibers having a fiber diameter of 3 μm or more, undrawn polyester-based short fibers having a fiber diameter of less than 3 μm, and undrawn polyester-based short fibers having a fiber diameter of more than 5 μm may be used. These may be used alone or in combination with fibers having two or more kinds of fiber diameters.

In the non-woven fabric for electromagnetic wave shielding material <2> of the present invention, the content of the drawn polyester-based short fibers having a fiber diameter of less than 3 μm is preferably 1 to 100% by mass in the total drawn polyester-based short fibers. More preferably, it is 3 to 100% by mass. When the content of the drawn polyester-based short fibers having a fiber diameter of less than 3 μm is less than 1% by mass, the specific surface area becomes small depending on the fiber diameter used in combination, and it may be difficult to exhibit excellent electromagnetic wave shielding properties.

Further, in the non-woven fabric <2> for electromagnetic wave shielding material of the present invention, the content of unstretched polyester-based short fibers having a fiber diameter of 3 μm or more and 5 μm or less is 1 to 100 mass among all unstretched polyester-based short fibers. % Is preferable, and 2 to 100% by mass is more preferable. When the content of undrawn polyester short fibers having a fiber diameter of 3 μm or more and 5 μm or less is less than 1% by mass, the specific surface area becomes small depending on the fiber diameter used in combination, and it becomes difficult to develop excellent electromagnetic wave shielding properties, or , It may be difficult to develop the strength of an excellent wet non-woven fabric.

In the non-woven fabric for electromagnetic wave shielding material <2> 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 further preferably 4 g / m ² or less. .. If the basis weight exceeds 7 g / m ² , the thickness of the electromagnetic wave shielding material may exceed 15 μm after the metal film treatment, and the electromagnetic wave shielding material may not be used for electronic devices, communication devices, electric appliances, and the like. The basis weight of the wet non-woven fabric is preferably 3 g / m ² or more. The basis weight was measured by the method described in JIS P8124: 2011.

In the non-woven fabric for electromagnetic wave shielding material <2> of the present invention, the density of the wet non-woven fabric is 0.5 to 0.8 g / cm ³ , more preferably 0.5 to 0.65 g / cm ³ . When the density is 0.8 g / cm ³ or less, the specific surface area is increased, so that the metal film by the metal film treatment is increased and the electromagnetic wave shielding property is improved. In addition, the metal film is less likely to come off. Further, when the density is 0.5 g / cm ³ or more, the strength of the wet non-woven fabric becomes high, defects are less likely to occur in the metal film treatment, and the metal film is less likely to be peeled off. The density was measured by the method described in JIS P8118: 2014.

-Non-woven fabric for electromagnetic wave shielding material <3>-
The non-woven fabric for electromagnetic wave shielding material <3> of the present invention is a wet non-woven fabric containing stretched polyester-based short fibers and unstretched polyester-based short fibers having a melting point of 220 ° C. or higher and 250 ° C. or lower. The peel strength (longitudinal direction) of the electromagnetic wave shielding material non-woven fabric <3> of the present invention is 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, still more preferably. It is 3.0 N / m or more. When the peeling strength (longitudinal direction) is less than 2.0 N / m, the adhesion between the fibers is too weak, so that the fibers are often dropped from the non-woven fabric for the electromagnetic wave shielding material during the alkali treatment, and the fibers are attached to the transport roll. Accumulation occurs, which causes problems such as the need for regular cleaning, which reduces operability, and the reattachment of fallen fibers to the non-woven fabric for electromagnetic wave shielding materials, which causes defects in the metal plating process. .. 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 preferably 10.0 N / m or less. If it exceeds 10.0 N / m, the non-woven fabric for the electromagnetic wave shielding material may be fused too much, and the surface of the non-woven fabric for the electromagnetic wave shielding material may become a film and the shape may not be maintained.

In the non-woven fabric for electromagnetic wave shielding material <3> of the present invention, the fiber diameter of the drawn polyester-based short fibers is preferably 1 to 10 μm, more preferably 2 to 8 μm. As the drawn polyester-based short fibers, two or more kinds of drawn polyester-based short fibers having different fiber diameters may be included. When the fiber diameter of the stretched polyester-based short fiber is 10 μm or less, it becomes easy to provide a thin electromagnetic wave shielding material. Further, it is preferable that the drawn polyester-based short fibers include polyester-based short fibers having a fiber diameter of 3 μm or less as an essential component. By including polyester-based short fibers having a fiber diameter of 3 μm or less, the electromagnetic wave shielding property is further improved.

In the non-woven fabric for electromagnetic wave shielding material <3> of the present invention, the fiber diameter of the unstretched polyester-based short fibers is preferably 1 to 8 μm, and more preferably 3 to 5 μm. When the fiber diameter is in this range, it becomes easy to provide a thin electromagnetic wave shielding material while increasing the strength of the wet non-woven fabric. As the undrawn polyester-based short fibers, two or more types of undrawn polyester-based short fibers having different fiber diameters can be included.

In the non-woven fabric for electromagnetic wave shielding material <3> of the present invention, the mass content ratio of the stretched polyester-based short fibers and the unstretched polyester-based short fibers is preferably 20:80 to 80:20. If the content of the unstretched polyester-based short fibers is less than 20% by mass of the total fibers constituting the wet non-woven fabric, the strength required for the non-woven fabric for the electromagnetic wave shielding material may not be exhibited. On the other hand, if the content of the unstretched polyester-based short fibers exceeds 80% by mass, the uniformity may be impaired. Further, in order to improve the electromagnetic wave shielding property, it is more preferable that the content of the drawn polyester-based short fibers having a fiber diameter of 3 μm or less is 5 to 80% by mass of the total fibers constituting the wet non-woven fabric. In the non-woven fabric <3> for electromagnetic shielding material of the present invention, the most preferable fiber composition is 20 to 80% by mass of unstretched polyester-based short fibers and 0 to 0 to 10 μm or less of stretched polyester-based short fibers having a fiber diameter of more than 3 μm and 10 μm or less. 75% by mass and 5 to 80% by mass of drawn polyester-based short fibers having a fiber diameter of 3 μm or less.

The thickness of the non-woven fabric <3> for an electromagnetic wave shielding material of the present invention is preferably 5 to 30 μm, more preferably 20 μm or less, for the purpose of using it in an electronic device. Basis weight (basis weight) is preferably 3 to 30 g / ^{m 2,} and more preferably 15 g / ^{m 2} or less. If the basis weight is less than 3 g / m ² , it becomes difficult to obtain uniformity, the effect of the electromagnetic wave shielding property tends to vary, and it becomes difficult to maintain the strength of the non-woven fabric itself for the electromagnetic wave shielding material, resulting in workability. There is a difficulty.

-Polyester-based short fibers-
In the present invention, the drawn polyester-based short fibers are the main fibers that are difficult to melt or soften even by the thermal calendar treatment and form the skeleton of the wet non-woven fabric.

In the present invention, the unstretched polyester-based short fibers function as binder fibers that are melted or softened by thermal calendar treatment to increase the strength of the wet non-woven fabric. The melting point of the unstretched polyester-based short fibers is preferably 220 ° C. to 250 ° C. In the non-woven fabric for electromagnetic wave shielding material <3> of the present invention, the melting point of the unstretched polyester-based short fibers is 220 ° C. or higher and 250 ° C. or lower. If the melting point of the unstretched polyester-based short fibers is less than 220 ° C., the wet non-woven fabric may stick to the thermal roll during the thermal calendar treatment, and the sheet may not be formed. If the temperature exceeds 250 ° C., the fibers may not adhere and the strength of the wet non-woven fabric may not be exhibited. The melting point of the unstretched polyester-based short fibers is more preferably 225 ° C. or higher and 250 ° C. or lower.

The melting point of the unstretched polyester-based short 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 by a differential scanning calorimetry device.

In the examples of the present invention, the fiber diameter of the polyester-based short fiber is the fiber diameter before the production of the non-woven fabric. The fiber diameter of the polyester-based short fiber is determined by taking a magnified photograph of the cross section of the wet non-woven fabric or electromagnetic wave shielding material 3000 times with a microscope, measuring the cross-sectional area of the polyester-based short fiber, and calculating the cross-sectional shape of the fiber as a perfect circle. It can be measured, and in that case, it is preferable to obtain the arithmetic average value of 10 or more fibers having substantially the same cross-sectional area.

The fiber length of the polyester-based short fibers is preferably 1 to 20 mm, more preferably 1 to 10 mm, and even more preferably 2 to 8 mm. When the fiber length of the polyester-based short fiber is less than 1 mm, it may be difficult to develop the strength required for the wet non-woven fabric. If the fiber length of the polyester-based short fibers exceeds 20 mm, the uniformity may be impaired.

In the present invention, examples of the polyester include polyethylene terephthalate, polyethylene isophthalate, polytrimethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, and polybutylene naphthalate. Polyester-based short fibers are preferable because the fiber diameter can be reduced in order to reduce the thickness of the electromagnetic wave shield, the ease of papermaking, and the dimensional stability during wet alkali treatment in the plating treatment. The polyester-based short fibers may be used alone or in combination of two or more.

-Wet non-woven fabric-
Examples of the method for forming the fibers into a sheet include various manufacturing methods such as a spunbond method, a melt blow method, an electrostatic spinning method, and a wet method. The non-woven fabric for an electromagnetic wave shielding material of the present invention is a wet method (papermaking method). It is a wet non-woven fabric formed in the form of a sheet, and is a non-woven fabric having excellent strength and high uniformity. Further, as a method for joining the fibers, various methods such as a chemical bond method and a heat fusion method can be mentioned. Among these, the heat fusion method is preferable because it has excellent durability and strength and the surface of the non-woven fabric is smooth.

As a heat fusion method in the wet method, a method of heat-sealing a sheet obtained by a paper making method when heat-drying with a dryer used after paper making such as a multi-cylinder dryer, a yankee dryer, or an air through dryer. Can be used. It is also possible to use a method of heat fusion by thermal calendar processing with a thermal calendar device having a roll combination such as a metal thermal roll / metal thermal roll, a metal thermal roll / elastic roll, and a metal thermal roll / cotton roll. it can. The binder component is thermally melted by heat drying or heat calendar treatment, and heat fusion occurs.

The conditions of the thermal calendar can be exemplified below, but are not limited thereto. The temperature of the heat roll in the heat calendar treatment is preferably 200 ° C. or higher and 215 ° C. or lower. If the temperature of the heat roll is less than 200 ° C., there may be a problem that the fibers do not adhere to each other and the strength is not developed. On the contrary, when the temperature of the heat roll is higher than 215 ° C., the wet non-woven fabric may stick to the heat roll, which may cause a problem that the sheet cannot be formed. The temperature of the heat roll is more preferably 203 ° C. or higher and 210 ° C. or lower, and even more preferably 205 ° C. or higher. In the non-woven fabric for electromagnetic wave shielding material <3> of the present invention, in order to increase the peeling strength of the non-woven fabric for electromagnetic wave shielding material, stretched polyester-based short fibers and unstretched polyester-based short fibers having a melting point of 220 ° C. or higher and 250 ° C. or lower are used. It is preferable that the wet non-woven fabric containing the above-mentioned material is subjected to thermal calendar treatment using a thermal roll having a temperature of 200 ° C. or higher and 215 ° C. or lower. A more preferable temperature of the heat roll is 203 ° C. or higher and 210 ° C. or lower.

In order to develop the strength, the pressure (linear pressure) in the thermal calendar treatment is preferably 50 to 250 kN / m, more preferably 80 to 150 kN / m. If the pressure is less than 50 kN / m, the smoothness of the surface may be impaired, and the thickness may not be reduced unless the speed is reduced. If the pressure is more than 250 kN / m, the sheet may not withstand the pressure and break. The processing speed of the thermal calendar is preferably 1 to 300 m / min. When the processing speed is 1 m / min or more, the work efficiency is improved. By setting the treatment speed to 300 m / min or less, heat is conducted to the wet non-woven fabric, and it becomes easy to obtain the effect of heat fusion. The number of nip times of the thermal calendar is not particularly limited as long as heat can be conducted to the wet non-woven fabric, but in the combination of the metal thermal roll / elastic roll, the nip is performed twice or more in order to conduct heat from the front and back of the wet non-woven fabric. You may.

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

In the present invention, examples of the metal film treatment include electroless metal plating treatment, electroplating treatment, metal vapor deposition treatment, and sputtering treatment. One or more processes selected from these processes can be performed. Above all, since it can be made thin, the surface resistance value tends to be low, and the metal film is difficult to peel off, it is preferable to perform the electroplating treatment after the sputtering treatment. The metal film may have one layer or two or more layers.

Examples of the type of metal used for the metal film treatment include 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 preferable, and copper and nickel are more preferable in consideration of conductivity and manufacturing cost.

In the present invention, it is more preferable that the metal film 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. First, a metal film is formed on the wet non-woven fabric by sputtering treatment. Nickel is preferable as the metal in the sputtering treatment. After the sputtering process, the metal film is laminated by electroplating. Copper is preferable as the metal for electroplating. Further, for rust prevention, a metal having good rust prevention such as nickel may be laminated on the outer layer thereof. 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 even more preferably 12 μm or less. If the thickness of the electromagnetic wave shielding material is larger than 15 μm, it may not be usable in electronic devices, communication devices, electric appliances, and the like. Further, the thickness of the electromagnetic wave shielding material is preferably 7 μm or more. The thickness was measured by the method described in JIS P8118: 2014.

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

The present invention will be described below with reference to examples, but the present invention is not limited to these examples. In addition, Examples 1 to 10 are reference examples, and in Examples,% and part are all based on mass unless otherwise specified.

<< Example of Nonwoven Fabric <1> for Electromagnetic Wave Shielding Material of the Present Invention >>

[Example 1]
30 parts by mass of stretched polyethylene terephthalate (PET) short fiber with a fineness of 0.3 dtex (fiber diameter 5.3 μm) and a fiber length of 3 mm, and a stretched PET short fiber with a fineness of 0.6 dtex (fiber diameter 7.4 μm) and a fiber length of 5 mm. 30 parts by mass of fibers and 40 parts by mass of unstretched PET-based short fibers having a fineness of 0.2 dtex (fiber diameter of 4.3 μm) and a fiber length of 3 mm are dispersed in water by a pulper, and a uniform papermaking slurry having a concentration of 1% by mass is dispersed. Was prepared. This slurry for making is made by a wet method with a slanted paper machine equipped with a paper making wire having an air permeability of 275 cm ³ / cm ² / sec and a structure [upper net: plain weave, lower net: ridge weave], and is made at 135 ° C. The unstretched PET-based short fibers were heat-sealed to develop strength with the cylinder dryer of No. 1 and obtained as a wet non-woven fabric having a grain size of 10 g / m ² . Further, this wet non-woven fabric is subjected to a thermal roll temperature of 200 ° C., a linear pressure of 100 kN / m, and a processing speed of 30 m / min by using a one-nip thermal calendar device composed of a dielectric heating jacket roll (metal thermal roll) and an elastic roll. A non-woven fabric for an electromagnetic wave shielding material having a thickness of 15 μm was prepared by performing a thermal calendar treatment under the above conditions.

[Example 2]
10 parts by mass of drawn PET short fibers 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 short fibers with a fineness of 0.6 dtex (fiber diameter 7.4 μm) and a fiber length of 5 mm. A non-woven fabric for an electromagnetic wave shielding material having a thickness of 17 μm was prepared in the same manner as in Example 1 except that the fineness was 0.2 dtex (fiber diameter 4.3 μm) and the fiber length was 3 mm and 40 parts by mass of unstretched PET-based short fibers. Made.

[Example 3]
50 parts by mass of drawn PET short fibers 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 short fibers with a fineness of 0.6 dtex (fiber diameter 7.4 μm) and a fiber length of 5 mm. A non-woven fabric for an electromagnetic wave shielding material having a thickness of 16 μm was prepared in the same manner as in Example 1 except that the fineness was 0.2 dtex (fiber diameter 4.3 μm) and the fiber length was 3 mm and 40 parts by mass of unstretched PET-based short fibers. Made.

[Example 4]
45 parts by mass of drawn PET short 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 short fibers with a fineness of 0.6 dtex (fiber diameter 7.4 μm) and a fiber length of 5 mm. A non-woven fabric for an electromagnetic wave shielding material having a thickness of 16 μm was prepared in the same manner as in Example 1 except that the fineness was 0.2 dtex (fiber diameter 4.3 μm) and the fiber length was 3 mm and 10 parts by mass of unstretched PET-based short fibers. Made.

[Example 5]
30 parts by mass of drawn PET short 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 short fibers with a fineness of 0.6 dtex (fiber diameter 7.4 μm) and a fiber length of 5 mm. A non-woven fabric for an electromagnetic wave shielding material having a thickness of 14 μm was prepared in the same manner as in Example 1 except that the fineness was 0.2 dtex (fiber diameter 4.3 μm) and the fiber length was 3 mm and 40 parts by mass of unstretched PET-based short fibers. Made.

[Example 6]
10 parts by mass of stretched PET short 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 short 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 short fibers with a fineness of 0.6 dtex (fiber diameter 7.4 μm) and a fiber length of 5 mm, and undrawn PET short fibers with a fineness of 0.2 dtex (fiber diameter 4.3 μm) and a fiber length of 3 mm. A non-woven fiber for electromagnetic wave shielding material having a thickness of 14 μm was produced in the same manner as in Example 1 except that the weight was 30 parts by mass.

[Example 7]
30 parts by mass of drawn PET short 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 short fibers with a fineness of 0.6 dtex (fiber diameter 7.4 μm) and a fiber length of 5 mm. And 10 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 unstretched PET short fibers with a fineness of 0.2 dtex (fiber diameter 4.3 μm) and a fiber length of 3 mm. A non-woven fiber for electromagnetic wave shielding material having a thickness of 16 μm was produced in the same manner as in Example 1 except that the weight was 30 parts by mass.

[Example 8]
10 parts by mass of drawn PET short 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 short 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 short fibers with a fineness of 0.6 dtex (fiber diameter 7.4 μm) and a fiber length of 5 mm, and undrawn PET short fibers with a fineness of 0.2 dtex (fiber diameter 4.3 μm) and a fiber length of 3 mm. A non-woven fiber for electromagnetic wave shielding material having a thickness of 14 μm was produced in the same manner as in Example 1 except that the weight was 30 parts by mass.

[Example 9]
30 parts by mass of drawn PET short 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 short 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 unstretched PET short fibers with a fineness of 0.2 dtex (fiber diameter 4.3 μm) and a fiber length of 3 mm, and unstretched PET short fibers with a fineness of 1.2 dtex (fiber diameter 10.5 μm) and a fiber length of 5 mm. A non-woven fabric for an electromagnetic wave shielding material having a thickness of 16 μm was produced in the same manner as in Example 1 except that the fibers were 10 parts by mass.

[Example 10]
15 parts by mass of stretched PET short 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 short fibers with a fineness of 0.6 dtex (fiber diameter 7.4 μm) and a fiber length of 5 mm. A non-woven fabric for an electromagnetic wave shielding material having a thickness of 14 μm was prepared in the same manner as in Example 1 except that the unstretched PET-based short fiber having a fineness of 0.2 dtex (fiber diameter of 4.3 μm) and a fiber length of 3 mm was 70 parts by mass. Made.

[Comparative Example 1]
30 parts by mass of drawn PET short 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 short fibers with a fineness of 0.6 dtex (fiber diameter 7.4 μm) and a fiber length of 5 mm. A non-woven fabric for an electromagnetic wave shielding material having a thickness of 17 μm was prepared in the same manner as in Example 1 except that the fibers had a fineness of 1.2 dtex (fiber diameter of 10.5 μm) and a fiber length of 5 mm and 40 parts by mass of unstretched PET-based short fibers. Made.

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

[Comparative Example 3]
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 and 30 parts by mass of drawn PET short fibers with a fineness of 3.3 dtex (fiber diameter 17.5 μm) and a fiber length of 5 mm. A non-woven fabric for an electromagnetic wave shielding material having a thickness of 21 μm was prepared in the same manner as in Example 1 except that the fineness was 0.2 dtex (fiber diameter 4.3 μm) and the fiber length was 3 mm and 40 parts by mass of unstretched PET-based short fibers. Made.

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

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

The non-woven fabric for electromagnetic wave shielding material produced in Examples and Comparative Examples was covered with a nickel film by an electroless plating method, and then a copper film and a nickel film were laminated in order by an electroplating method to prepare an electromagnetic wave shielding material. ..

<Evaluation>
[Transportability]
The non-woven fabric for the electromagnetic wave shielding material was conveyed with a constant tension, and the wrinkle generation state at that time was evaluated according to the following criteria.

"○" No wrinkles and very good transportability.
"△" There are wrinkles in a part of the non-woven fabric for electromagnetic wave shielding material, but there is no problem in transportability.
Wrinkles are formed on the entire non-woven fabric for electromagnetic wave shielding material to the extent that "x" processing cannot be performed, and the transportability is inferior.

[Electromagnetic wave shielding property (electric field)]
The measurement was performed based on the electromagnetic wave shielding property (electric field) by the coaxial tube method. The frequency range of 40 MHz to 3 GHz was measured by the coaxial tube method 39D, and the frequency range of 500 MHz to 18 GHz was measured by the coaxial tube method GPC7. The frequencies of 500 MHz to 3 GHz are measured by both the coaxial tube method 39D and the coaxial tube method 7, but low values are adopted.

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

The non-woven fabric for electromagnetic wave shielding material of Examples 1 to 10 is selected from drawn polyester short fibers having a fiber diameter of 3 μm or more and less than 12 μm, and two or more kinds of drawn polyester short fibers having different fiber diameters and a fiber diameter of 3 μm. Since it is a wet non-woven fabric containing unstretched polyester-based short fibers of 5 μm or less as an essential component, it has excellent transportability and excellent electromagnetic wave shielding properties. The non-woven fabric for the electromagnetic wave shielding material of Example 4 had a slightly reduced strength, but there was no problem in transportability, and the electromagnetic wave shielding property was also excellent.

On the other hand, two or more kinds of drawn polyester short fibers having different fiber diameters selected from drawn polyester short fibers having a fiber diameter of 3 μm or more and less than 12 μm, and unwoven polyester short fibers having 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 which did not contain fibers as essential components were inferior in electromagnetic wave shielding properties. That is, two types of drawn fibers having different fiber diameters are selected from the non-woven fabric for electromagnetic wave shielding material of Comparative Example 1 in which the fiber diameter of the unstretched polyester short fibers exceeds 5 μm and the drawn polyester short fibers having a fiber diameter of 12 μm or more. The non-woven fabric for electromagnetic wave shielding material of Comparative Example 3 containing polyester-based short fibers, the non-woven fabric for electromagnetic wave shielding material of Comparative Example 4 in which the fiber diameter of the stretched polyester-based short fibers is 12 μm, and the 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-based short fibers having the same fiber diameter (fiber diameter of 5.3 μm), although it contains the stretched polyester-based short fibers of It is considered that the reflection loss has decreased.

Further, Comparative Example 5 in which the drawn polyester short fibers having a fiber diameter of 3 μm or more and less than 12 μm are contained, but only one type of drawn polyester short fibers having the same fiber diameter (fiber diameter 3.0 μm) is contained. The non-woven fabric for electromagnetic wave shielding material is inferior in transportability due to wrinkles when the web is transported. It is considered that the web became supple, easily stretched, and wrinkled easily by containing only the drawn polyester-based short fibers having a small fiber diameter.

<< Examples of Nonwoven Fabric <2> for Electromagnetic Wave Shielding Material of the Present Invention >>

<Evaluation>
(1) The surface resistance value was measured based on MIL DTL 83528C.

(2) Electromagnetic wave shielding property (electric field)
The measurement was performed based on the electromagnetic wave shielding property (electric field) by the coaxial tube method. The frequency range of 40 MHz to 3 GHz was measured by the coaxial tube method 39D, and the frequency range of 500 MHz to 18 GHz was measured by the coaxial tube method GPC7. The frequencies of 500 MHz to 3 GHz are measured by both the coaxial tube method 39D and the coaxial tube method GPC7, but low values are adopted.

(3) Peel evaluation Adhesive tape (Nitto (registered trademark) 31B tape, manufactured by Nitto Denko KK) is attached to an electromagnetic wave shielding material sample with a width of 25 mm and a length of 150 mm, and a roll of 2 kg is used for 10 at a speed of 300 mm / min. Rolling times. Then, the tape and the sample are angled at 180 degrees and peeled off at a speed of 1000 mm / min. It was evaluated according to the following criteria.

<Criteria>
◯: The measurement was performed 3 times, and there was no breakage of the sample and no adhesion of metal powder to the tape.
Δ: The measurement was performed 3 times, and the sample was broken and the metal powder adhered to the tape once or twice.
X: The measurement was performed 3 times, and the sample was broken and the metal powder adhered to the tape 3 times.

[Example 11]
20 parts by mass of stretched polyethylene terephthalate (PET) short fiber with a fineness of 0.06 dtex (fiber diameter 2.4 μm) and a fiber length of 3 mm, and a stretched PET short fiber with a fineness of 0.3 dtex (fiber diameter 5.3 μm) and a fiber length of 3 mm. 40 parts by mass of fibers and 40 parts by mass of unstretched PET-based short fibers for single component type binders having a fineness of 0.2 dtex (fiber diameter of 4.3 μm) and a fiber length of 3 mm were dispersed in water by a pulper to a concentration of 1% by mass. A uniform papermaking slurry was prepared. This slurry for making is made by a wet method with a slanted paper machine equipped with a paper making wire having an air permeability of 275 cm ³ / cm ² / sec and a structure [upper net: plain weave, lower net: ridge weave], and is made at 135 ° C. The unstretched PET-based short fibers for the binder were heat-sealed to develop strength by using the cylinder dryer of the above, and a wet non-woven fabric was obtained. Further, this wet non-woven fabric is subjected to a thermal roll temperature of 200 ° C., a linear pressure of 100 kN / m, and a processing speed of 100 m / min by using a 1-nip thermal calendar device composed of a dielectric heating jacket roll (metal thermal roll) and an elastic roll. A non-woven fabric for an electromagnetic wave shielding material having a grain size of 6.5 g / m ² and a density of 0.50 g / cm ³ was prepared by performing a thermal calendar treatment under the conditions of.

Next, the non-woven fabric for the electromagnetic wave shielding material was covered with a nickel film by electroless plating, and then a copper film and a nickel film were laminated in this order by electroplating, and a metal film treatment was performed to obtain a thickness of 17.5 μm. Obtained the electromagnetic wave shielding material of.

[Example 12]
The fiber composition is as follows: 40 parts by mass of stretched PET short fibers having a fineness of 0.06 dtex (fiber diameter 2.4 μm) and a fiber length of 3 mm, and drawn PET short fibers having a fineness of 0.3 dtex (fiber diameter 3.0 μm) and a fiber length of 3 mm. The same as in Example 11 except that 20 parts by mass of the fiber and 40 parts by mass of the unstretched PET-based short fiber for a single component type binder having a fineness of 0.2 dtex (fiber diameter of 4.3 μm) and a fiber length of 3 mm were used. , Wet non-woven fabric was obtained. This wet non-woven fabric was subjected to thermal calendar treatment in the same manner as in Example 11 except that the treatment speed was 50 m / min, and the non-woven fabric for electromagnetic wave shielding material having a basis weight of 6.5 g / m ² and a density of 0.63 g / cm ^3. Was produced. Next, a 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 composition is a single component type with a fineness of 0.06 dtex (fiber diameter of 2.4 μm), a fiber length of 3 mm and 60 parts by mass of drawn PET-based short fibers, and a fineness of 0.2 dtex (fiber diameter of 4.3 μm) and a fiber length of 3 mm. A wet nonwoven fabric was obtained in the same manner as in Example 11 except that 40 parts by mass of unstretched PET-based short fibers for binders were used. The wet non-woven fabric was subjected to thermal calendar treatment in the same manner as in Example 11 except that the linear pressure was 125 kN / m and the treatment speed was 40 m / min, and the basis weight was 6.5 g / m ² and the density was 0.80 g / cm ^3. A non-woven fabric for electromagnetic wave shielding material was produced. Next, a 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 non-woven fabric was obtained in the same manner as in Example 11 except that the basis weight was 5.0 g / m ² . This wet non-woven fabric was subjected to a thermal calendar treatment in the same manner as in Example 13 to prepare a non-woven fabric for an electromagnetic wave shielding material having a density of 0.80 g / cm ³ . Next, the non-woven fabric for the electromagnetic wave shielding material is covered with a nickel film by sputtering treatment, and a copper film and a nickel film are laminated in this order by electroplating treatment, and a metal film treatment is performed to obtain an electromagnetic wave shielding material having a thickness of 8.5 μm. It was.

[Example 15]
A wet non-woven fabric was obtained in the same manner as in Example 12 except that the basis weight was 5.0 g / m ² . This wet non-woven fabric was subjected to a thermal calendar treatment in the same manner as in Example 11 to prepare a non-woven fabric for an electromagnetic wave shielding material having a density of 0.50 g / cm ³ . Next, the non-woven fabric for the electromagnetic wave shielding material was subjected to a metal film 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 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 non-woven fabric was subjected to a thermal calendar treatment in the same manner as in Example 12 to prepare a non-woven fabric for an electromagnetic wave shielding material having a density of 0.63 g / cm ³ . Next, a 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]
The fiber composition is a single component type having a fineness of 0.3 dtex (fiber diameter of 5.3 μm) and a fiber length of 5 mm and 60 parts by mass of drawn PET-based short fibers and a fineness of 1.2 dtex (fiber diameter of 10.7 μm) and a fiber length of 5 mm. A wet non-woven fabric having a grain size of 10.0 g / m ² was obtained in the same manner as in Example 11 except that 40 parts by mass of unstretched PET-based short fibers for binders were used. This wet non-woven fabric was subjected to thermal calendar treatment in the same manner as in Example 11 except that the conditions were a linear pressure of 135 kN / m and a treatment speed of 40 m / min to prepare a non-woven fabric for an electromagnetic wave shielding material having a density of 0.85 g / cm ^3. did. Next, a 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]
A non-woven fabric for an 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 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. did. 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]
A non-woven fabric for an 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 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. did. 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 an 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, a 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 an 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, a 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 an 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, a 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.

It contains drawn polyester-based short fibers with a fiber diameter of less than 3 μm and undrawn polyester-based short fibers with a fiber diameter of 3 μm or more and 5 μm or less as essential components, has a texture of 7 g / m ² or less, and has a density of 0.5 to 0. Examples 11 to 16 which are electromagnetic shielding materials obtained by applying a metal film treatment to a non-woven fabric for an electromagnetic wave shielding material which is a wet non-woven fabric of 8 g / cm ³ have an excellent electromagnetic shielding property and an effect that the metal film is hard to peel off. I was able to achieve it. Further, the metal film 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, and the thickness is 15 μm or less and the surface resistance. The electromagnetic shielding materials of Examples 14 to 16 having a value of 0.03Ω / □ or less are superior in electromagnetic shielding properties to the electromagnetic shielding materials of Examples 11 to 13, and the metal film may be more difficult to peel off. I understand.

Comparative Examples 11 to 16 are electromagnetic waves which are wet non-woven fabrics containing drawn PET short fibers having a fiber diameter of 3 μm or more and unstretched PET short fibers having a fiber diameter of more than 5 μm and having a grain size of more than 7 g / m ^2. An electromagnetic wave shielding material obtained by applying a metal film treatment to a non-woven fabric for a shielding material. In Comparative Examples 11 and 13, the metal film 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. The result of the peel evaluation was bad. The electromagnetic wave shielding material of Comparative Example 12 had good electromagnetic wave shielding properties and peel evaluation, but the thickness of the electromagnetic wave shielding material was 20.0 μm and could not be reduced. In Comparative Examples 14 to 16, the copper film and the nickel film were laminated in this order by electroless plating, and then the copper film and nickel film were laminated in order and treated with a metal film. The peel evaluation result was good. However, the electromagnetic wave shielding property was poor.

<< Examples of Nonwoven Fabric <3> for Electromagnetic Wave Shielding Material of the Present Invention >>

[Example 21]
30 parts by mass of stretched polyethylene terephthalate (PET) short fiber with a fineness of 0.6 dtex (fiber diameter 7.4 μm) and a fiber length of 5 mm, and a stretched PET short fiber with a fineness of 0.3 dtex (fiber diameter 5.3 μm) and a fiber length of 3 mm. 30 parts by mass of the fiber and 40 parts by mass of the unstretched PET-based short fiber for a single component type binder having 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. were dispersed in water by a pulper. A uniform papermaking slurry having a concentration of 1% by mass was prepared. This slurry for making is made by a wet method with a slanted paper machine equipped with a paper making wire having an air permeability of 275 cm ³ / cm ² / sec and a structure [upper net: plain weave, lower net: ridge weave], and is made at 135 ° C. The unstretched PET-based short fibers for the binder were heat-sealed to develop strength by using the cylinder dryer of No. 1 (Cylinder Dryer) to obtain a wet non-woven fabric having a grain size of 10 g / m ² . Further, this wet non-woven fabric is subjected to a thermal roll temperature of 202 ° C., a linear pressure of 100 kN / m, and a processing speed of 40 m / min by using a 1-nip thermal calendar device composed of a dielectric heating jacket roll (metal thermal roll) and an elastic roll. A non-woven fabric for an electromagnetic wave shielding material having a thickness of 15 μm and a peel strength of 2.1 N / m was prepared by performing a thermal calendar treatment under the above conditions.

[Example 22]
A non-woven fabric for an 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 thermal roll temperature was set to 208 ° C.

[Example 23]
A non-woven fabric for an 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 thermal roll temperature was set to 205 ° C.

[Example 24]
The blend of stretched polyester-based short fibers includes 30 parts by mass of drawn PET-based short fibers having a fineness of 0.6 dtex (fiber diameter of 7.4 μm) and a fiber length of 3 mm, and a fineness of 0.1 dtex (fiber diameter of 3.0 μm) and a fiber length of 3 mm. A non-woven fabric for an electromagnetic wave shielding material having a thickness of 15 μm and a peeling strength of 3.5 N / m was produced in the same manner as in Example 23 except that the stretched PET-based short fibers were 30 parts by mass.

[Example 25]
The blend of stretched polyester-based short fibers includes 30 parts by mass of drawn PET-based short fibers having a fineness of 0.6 dtex (fiber diameter of 7.4 μm) and a fiber length of 3 mm, and a fineness of 0.06 dtex (fiber diameter of 2.4 μm) and a fiber length of 3 mm. A non-woven fabric for an electromagnetic wave shielding material having a thickness of 15 μm and a peeling strength of 3.7 N / m was produced in the same manner as in Example 23 except that the stretched PET-based short fibers were 30 parts by mass.

[Example 26]
The blend of stretched polyester-based short fibers includes 30 parts by mass of stretched PET-based short fibers having a fineness of 0.3 dtex (fiber diameter of 5.3 μm) and a fiber length of 3 mm, and a fineness of 0.1 dtex (fiber diameter of 3.0 μm) and a fiber length of 3 mm. A non-woven fabric for an electromagnetic wave shielding material having a thickness of 15 μm and a peeling strength of 3.4 N / m was produced in the same manner as in Example 23 except that the stretched PET-based short fibers were 30 parts by mass.

[Example 27]
The blend of stretched polyester-based short fibers includes 30 parts by mass of stretched PET-based short fibers having a fineness of 0.3 dtex (fiber diameter of 5.3 μm) and a fiber length of 3 mm, and a fineness of 0.06 dtex (fiber diameter of 2.4 μm) and a fiber length of 3 mm. A non-woven fabric for an electromagnetic wave shielding material having a thickness of 15 μm and a peeling strength of 3.3 N / m was produced in the same manner as in Example 23 except that the stretched PET-based short fibers were 30 parts by mass.

[Example 28]
The blend of stretched polyester-based short fibers includes 30 parts by mass of stretched PET-based short fibers having a fineness of 0.1 dtex (fiber diameter 3.0 μm) and a fiber length of 3 mm, and a fineness of 0.06 dtex (fiber diameter 2.4 μm) and a fiber length of 3 mm. A non-woven fabric for an electromagnetic wave shielding material having a thickness of 15 μm and a peeling strength of 3.5 N / m was produced in the same manner as in Example 23 except that the stretched PET-based short fibers were 30 parts by mass.

[Comparative Example 21]
A non-woven fabric for an 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 thermal roll temperature was 198 ° C.

[Comparative Example 22]
A non-woven fabric for an 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 thermal roll temperature was set to 195 ° C.

[Comparative Example 23]
A non-woven fabric for an 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 thermal roll temperature was 198 ° C.

[Comparative Example 24]
A non-woven fabric for an 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 thermal roll temperature was 198 ° C.

[Comparative Example 25]
The composition of the fibers is as follows: 30 parts by mass of stretched PET short fibers having a fineness of 0.6 dtex (fiber diameter 7.4 μm) and a fiber length of 3 mm, and drawn PET type having a fineness of 0.3 dtex (fiber diameter 5.3 μm) and a fiber length of 3 mm. 30 parts by mass of short fibers, 0.1 dtex (fiber diameter 3.0 μm), 30 parts by mass of drawn PET-based short fibers having a fiber length of 3 mm, fineness 0.2 dtex (fiber diameter 4.3 μm), fiber length 3 mm, melting point A non-woven fabric for an electromagnetic wave shielding material having a thickness of 15 μm and a peeling strength of 0.2 N / m was produced in the same manner as in Example 23 except that 10 parts by mass of unstretched PET-based short fibers for a single component type binder at 246 ° C. were used. did.

[Comparative Example 26]
The fibers are blended with 10 parts by mass of drawn PET short fibers having a fineness of 0.6 dtex (fiber diameter of 7.4 μm) and a fiber length of 3 mm, and 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. A non-woven fabric for an electromagnetic wave shielding material having a thickness of 15 μm and a peeling strength of 1.8 N / m was produced in the same manner as in Example 23 except that 90 parts by mass of unstretched PET-based short fibers for a single component type binder was prepared.

The non-woven fabric for electromagnetic wave shielding material produced in Examples and Comparative Examples was subjected to an alkali treatment, which is a pre-plating treatment, and a metal plating treatment of copper and nickel was performed by an electroless plating method to prepare an electromagnetic wave shielding material.

<Evaluation>
[Peeling strength]
Cut the non-woven fabric for electromagnetic wave shielding material into 25 mm x 200 mm, and attach double-sided tape (Nichiban, product name: NW-R25, Nystack (registered trademark) low adhesive type) to the mount (Mitsubishi Paper, product name: N Pearl Card). FSC certification-MX (450.0g / m ² )) is attached to the non-glossy surface, a non-woven fabric for electromagnetic wave shielding material is layered on it, and a wrapping tape (manufactured by Kamoi Kogyo, product name: No. .220W) was pasted, and a peeling test was carried out in the form as shown in FIG. 1 to measure the peeling strength. For the peeling test, use SHIMPO (Nippon Densan Symposium), device name: Digital Force Gauge FGC-2B, set the distance between jigs to 1.8 cm, and make sure that there is a non-woven fabric for electromagnetic wave shielding material in the center of the distance. , Measured under the condition of a speed of 100 mm / min.

[Fiber drop resistance]
Collect the non-woven fabric for electromagnetic wave shielding material, cut it into 25 mm x 200 mm, use a Gakushin type friction fastness tester, and use a Billikenmos (registered trademark) cloth with a weight of 500 gf to cut the non-woven fabric for electromagnetic wave shield material 5 It was rubbed back and forth and evaluated according to the following criteria.

"◎" Fibers do not adhere to the Billikenmos cloth.
"○" Fibers hardly adhere to the Billikenmos cloth.
"△" Some fibers adhere to the Billikenmos cloth, but there is no problem in practical use.
"X" Fibers adhere to the Billikenmos cloth, and in some cases, the base material breaks.

[Defect frequency]
We confirmed the frequency of defects per 1000 m when the non-woven fabric for electromagnetic wave shielding material, which had been subjected to alkali treatment, which is a pre-plating treatment, was subjected to metal plating treatment.

"◎" 0 pieces / 1000m.
"○" 1 piece / 1000m.
"△" 2 pieces / 1000m.
"X" 3 or more / 1000m.

[Electromagnetic wave shielding property (electric field)]
The measurement was performed based on the electromagnetic wave shielding property (electric field) by the coaxial tube method. The frequency range of 40 MHz to 3 GHz was measured by the coaxial tube method 39D, and the frequency range of 500 MHz to 18 GHz was measured by the coaxial tube method GPC7. The frequencies of 500 MHz to 3 GHz are measured by both the coaxial tube method 39D and the coaxial tube method 7, but low values are adopted.

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

The non-woven fabrics for electromagnetic wave shielding materials of Examples 21 to 28 have higher peel strength than the non-woven fabrics for electromagnetic wave shielding materials of Comparative Examples 21 to 26, and therefore have excellent fiber drop resistance and less frequent defects. The yield was also good, and excellent electromagnetic wave shielding properties were exhibited.

Comparing Examples 21 to 23, in Example 23 in which the thermal 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 thermal roll temperature was lower than 200 ° C., the peel strength of the non-woven fabric for the electromagnetic wave shielding material was low, the fiber drop resistance was poor, and the frequency of defects was very high.

In Comparative Examples 25 and 26, the content of the unstretched polyester-based short fibers was less than 20% by mass or more than 80% by mass of the total fibers constituting the non-woven fabric for the electromagnetic wave shielding material, which was out of the preferable range, and thus the thermal roll temperature. The temperature was 205 ° C., which was a preferable range, but the peeling strength was low, and the non-woven fabric for electromagnetic wave shielding material having poor fiber dropout resistance was obtained.

The non-woven fabric for electromagnetic wave shielding material and the electromagnetic wave shielding material of the present invention are suitably used for electronic devices, communication devices, electric appliances and the like. These devices and products include devices such as mobile phones, smartphones, mobile phones, personal computers and mobiles, cases for storing them, and electrical appliances such as televisions and washing machines. In particular, the electromagnetic wave shielding material of the present invention is preferably used by fixing it to a plastic housing, a flexible printed substrate, an electric wire cable, a connector cable, or the like by adhesion, crimping, fusion, winding, or the like.

Claims (6)

A non-woven fabric for electromagnetic wave shielding material, which is a wet non-woven fabric, contains drawn polyester-based short fibers having a fiber diameter of less than 3 μm and unstretched polyester-based short fibers having a fiber diameter of 3 μm or more and 5 μm or less as essential components, and has a texture of 7 g / m ² or less. A non-woven fabric for an electromagnetic wave shielding material, which has a density of 0.5 to 0.8 g / cm ³ . The non-woven fabric for electromagnetic wave shielding material, which is a wet non-woven fabric, contains stretched polyester-based short fibers and unstretched polyester-based short fibers having a melting point of 220 ° C. or higher and 250 ° C. or lower, and the peel strength (longitudinal direction) of the non-woven fabric is 2.0 N / Non-woven fabric for electromagnetic wave shielding material characterized by being m or more. The electromagnetic wave shielding material according to any one of claims 1 to 2, wherein the non-woven fabric for the electromagnetic wave shielding material is treated with a metal film. The electromagnetic wave shielding material according to claim 3, wherein the metal film treatment is one or more treatments selected from the group consisting of electroless metal plating treatment, electroplating treatment, metal vapor deposition treatment, and sputtering treatment. The electromagnetic wave shielding material according to claim 3, wherein the metal film 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. .. The electromagnetic wave shielding material according to any one of claims 3 to 5, 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 0.03Ω / □ or less.