KR20210057047A - Non-woven fabric for electromagnetic shielding material and electromagnetic shielding material - Google Patents

Abstract

An object of the present invention is to provide a nonwoven fabric base material for electromagnetic wave shielding materials and an electromagnetic wave shielding material capable of expressing excellent electromagnetic wave shielding properties.
Two or more oriented polyester-based short fibers having different fiber diameters selected from oriented polyester-based short fibers having a fiber diameter of 3 µm or more and less than 12 µm, and undrawn polyester-based short fibers having a fiber diameter of 3 µm or more and 5 µm or less A nonwoven fabric for electromagnetic wave shielding material, which is a wet nonwoven fabric containing, contains a stretched polyester short fiber having a fiber diameter of less than 3 µm and an unstretched polyester short fiber having a fiber diameter of 3 µm or more and 5 µm or less, and has an apparent weight of 7 g/ ㎡ or less, and a non-woven fabric for electromagnetic wave shielding material, which is a wet non-woven fabric having a density of 0.5 to 0.8 g/cm 3, contains short stretched polyester fibers and short unstretched polyester fibers having a melting point of 220° C. or more and 250° C. or less. A nonwoven fabric for electromagnetic wave shielding materials having a peel strength (vertical direction) of 2.0 N/m or more.

Description

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

The present invention relates to a nonwoven fabric for electromagnetic wave shielding materials and an electromagnetic wave shielding material that is excellent in transportability of a web and can exhibit excellent electromagnetic wave shielding properties.

Electronic devices are generating electromagnetic waves. Further, in order to prevent electromagnetic waves from leaking to the outside of the electronic device, and to prevent the electronic device from malfunctioning due to electromagnetic waves, an electromagnetic wave shielding material is used. Examples of the electromagnetic shielding material include sheet metal, a coating material containing a metal, a metal mesh, and a foamed metal. Further, an electromagnetic shielding material obtained by subjecting a nonwoven fabric formed of a polyester-based short fiber to a metal plating treatment is disclosed (see, for example, Patent Documents 1 and 2).

Patent Literature 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 woven, knitted or non-woven fiber by a wet plating method around the outer circumference and the entire circumference of the cross section. As the chemical fibers, polyester fibers and polypropylene fibers are preferable because they are excellent in tensile strength and elongation properties of the substrate itself, and furthermore, deterioration in properties in the pretreatment step for plating can be prevented.

In Patent Document 2, an electromagnetic shielding material obtained by subjecting a wet nonwoven fabric to a metal coating treatment, which contains polyester fibers having a single fiber fineness of 1.1 dtex or less, and has a thickness in the range of 10 to 30 µm. Ash has been disclosed.

[0003] With the recent miniaturization, high frequency and high performance of electronic devices, a thinner, high magnetic wave shielding electromagnetic wave shielding material has been demanded. Specifically, there is a demand for an electromagnetic shielding material having a thickness of 15 µm or less and exhibiting excellent electromagnetic shielding properties over a wide frequency range of 100 MHz to 10 GHz.

As in Patent Documents 1 and 2, when metal coating treatment such as metal plating treatment is performed on the nonwoven fabric, processing is performed with a roll to roll with good productivity, but wrinkles occur in the nonwoven fabric at the time of conveyance, and conveyance. There was a problem that the castle was not excellent.

In addition, in the example of Patent Document 2, a polyester oriented fiber having a single fiber fineness of 0.1 dtex and an unstretched binder fiber having a single fiber fineness of 0.2 dtex are contained, and the basis weight of the wet nonwoven fabric is 8 g/m 2, The electromagnetic shielding material has an apparent weight of 19 g/m 2 and a thickness of 12 µm. However, as a thin electromagnetic wave shielding material is required, the electromagnetic wave shielding material of Patent Document 2 has a problem in that the electromagnetic wave shielding property cannot be sufficiently secured. In addition, there was a case where a problem of peeling of the metal film occurred.

In addition, in the electromagnetic shielding material subjected to metal plating treatment on the nonwoven fabric, it is required that the polyester short fibers and the metal film formed by the metal plating treatment be in close contact. Therefore, as a plating pretreatment step, the polyester short fibers are required to be in close contact with each other. It is known to perform an alkali treatment.

In Patent Document 1, it is described that the polyester fiber can prevent deterioration in properties in the plating pretreatment step. However, in general, the alkali treatment of the nonwoven fabric is a wet treatment, and fibers may fall off in the water tank, which significantly lowers the operability. In addition, there was a case where a problem of occurrence of defects in metal plating treatment occurred due to the detached fibers being reattached to the nonwoven fabric.

Japanese Open Utility Model Publication No. 48-40800 Japanese Laid-Open Patent Publication No. 2014-75485

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

A second object of the present invention is to provide a nonwoven fabric for an electromagnetic wave shielding material that is thin and capable of exhibiting excellent electromagnetic shielding properties, and a metal film is difficult to peel off, and an electromagnetic wave shielding material using the nonwoven fabric for electromagnetic wave shielding materials.

A third object of the present invention is to provide a nonwoven fabric for electromagnetic wave shielding material with little fiber dropout and high strength in alkali treatment, which is a pretreatment step for plating for electromagnetic wave shielding material, and an electromagnetic wave shielding material using the nonwoven fabric for electromagnetic wave shielding material.

The present inventors discovered the following invention as a result of earnestly researching in order to solve the said subject.

<1> In the nonwoven fabric for electromagnetic wave shielding material, which is a wet nonwoven fabric, the wet nonwoven 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 oriented polyester short fibers having different fiber diameters. And an unstretched polyester-based short fiber having a fiber diameter of 3 µm or more and 5 µm or less as an essential component.

<2> In the nonwoven fabric for electromagnetic wave shielding material, which is a wet nonwoven fabric, it contains as an essential component a stretched polyester short fiber having a fiber diameter of less than 3 µm and an unstretched polyester short fiber having a fiber diameter of 3 µm or more and 5 µm or less. A nonwoven fabric for an electromagnetic shielding material, characterized in that it has a weight of 7 g/m 2 or less and a density of 0.5 to 0.8 g/cm 3.

<3> In the nonwoven fabric for electromagnetic wave shielding material, which is a wet nonwoven fabric, it contains a stretched polyester short fiber and an unstretched polyester short fiber having a melting point of 220°C or more and 250°C or less, and the peel strength (vertical direction) of the nonwoven fabric is 2.0 Non-woven fabric for electromagnetic wave shielding material, characterized in that N/m or more.

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

<5> The electromagnetic shielding material according to <4>, wherein the metal coating treatment is at least one treatment selected from the group consisting of an electroless metal plating treatment, an electroplating treatment, a metal vapor deposition treatment, and a sputtering treatment.

<6> The above characterized in that the metal coating treatment includes, in this 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. The electromagnetic wave shielding material described in <4>.

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

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

The second effect of the present invention is that it is possible to provide a nonwoven fabric for an electromagnetic shielding material that is thin and capable of exhibiting excellent electromagnetic shielding properties, and the metal film is difficult to peel off, and an electromagnetic shielding material using the nonwoven fabric for electromagnetic shielding materials.

A third effect of the present invention is to provide an electromagnetic wave shielding material using a nonwoven fabric for electromagnetic wave shielding material with little fiber dropout and high strength, and a nonwoven fabric for electromagnetic wave shielding material in the alkali treatment, which is a pretreatment step for plating for electromagnetic wave shielding material. .

1 is a schematic diagram showing a state of a nonwoven fabric for electromagnetic wave shielding materials when peeling strength is measured.

Hereinafter, the nonwoven fabric for electromagnetic shielding material and the electromagnetic shielding material of the present invention will be described in detail.

－Non-woven fabric for electromagnetic shielding material <1>-

The nonwoven fabric <1> for an electromagnetic wave shielding material of the present invention 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 oriented polyester short fibers having different fiber diameters, and a fiber diameter of 3 It is characterized in that it is a wet-type nonwoven fabric containing as an essential component unstretched polyester-based staple fibers of µm or more and 5 µm or less.

In general, since tension is applied to the nonwoven fabric at the time of conveyance in the roll-to-roll processing in the MD (Machine Direction) direction, the nonwoven fabric is stretched, which causes wrinkles. The nonwoven fabric <1> for an electromagnetic wave shielding material of the present invention 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 oriented polyester short fibers having different fiber diameters, and a fiber diameter of 3 One type of oriented polyester-based short selected from stretched polyester-based short fibers having a fiber diameter of 3 µm or more and less than 12 µm and having the same fiber diameter as it contains as an essential component unstretched polyester short fibers of µm or more and 5 µm or less. Compared with a nonwoven fabric containing fibers and unstretched polyester-based short fibers having a fiber diameter of 3 µm or more and 5 µm or less as essential components, it is difficult to stretch, and therefore, it is difficult to wrinkle at the time of conveyance. Further, when a nonwoven fabric having a fiber diameter of 12 µm or more and a large fiber diameter of the stretched polyester-based short fibers is used, it is difficult to obtain a thin electromagnetic shielding material. The nonwoven fabric <1> for an electromagnetic wave shielding material of the present invention contains a stretched polyester short fiber having a fiber diameter of less than 12 µm and an unstretched polyester short fiber having a fiber diameter of 3 µm or more and 5 µm or less, so that it is thin and has transportability. This excellent effect can be achieved.

In general, the electromagnetic shielding property is achieved by absorption return loss, return loss, and multiple return loss of electromagnetic waves. In the nonwoven fabric <1> for an electromagnetic wave shielding material of the present invention, by using two or more kinds of stretched polyester 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, electromagnetic waves Electromagnetic waves that have penetrated into the shielding material are easily reflected in the electromagnetic wave shielding material, and excellent electromagnetic wave shielding properties can be obtained by improving multiple reflection losses.

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

In the nonwoven fabric <1> for an electromagnetic wave shielding material of the present invention, a stretched polyester short fiber other than a stretched polyester short fiber having a fiber diameter of 3 µm or more and less than 12 µm may be used. Further, unstretched polyester short fibers other than unstretched polyester short fibers having a fiber diameter of 3 µm or more and 5 µm or less may be used. In other words, short stretched polyester fibers with a fiber diameter of less than 3 µm, short oriented polyester fibers with a fiber diameter of 12 µm or more, undrawn polyester short fibers with a fiber diameter of less than 3 µm, and unrolled fibers with a fiber diameter of more than 5 µm. New polyester-based short fibers may be used. These may be used alone, or two or more types of fibers having a fiber diameter may be used in combination.

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

In addition, in the nonwoven fabric <1> for electromagnetic wave shielding material of the present invention, for the unstretched polyester short fibers having a fiber diameter of 3 μm or more and 5 μm or less, the mass content rate is among all the unstretched polyester short fibers contained. , 1-100 mass% is preferable, and 2-100 mass% is more preferable. When the content of the unstretched polyester-based 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 to be used in some cases, making it difficult to exhibit excellent electromagnetic shielding properties. . Moreover, it may become difficult to express the strength of the wet nonwoven fabric.

The thickness of the nonwoven fabric <1> for electromagnetic shielding materials of the present invention is preferably 7 to 30 µm, and more preferably 15 µm or less, for use in electronic devices. It is preferable that it is 5-30 g/m<2>, and, as for the apparent weight (base weight), it is more preferable that it is 15 g/m<2> or less. If the apparent weight is less than 5 g/m 2, it becomes difficult to obtain uniformity, and unevenness is liable to occur in the effect of electromagnetic shielding properties.

－Non-woven fabric for electromagnetic shielding material <2>-

The nonwoven fabric <2> for an electromagnetic wave shielding material of the present invention contains as an essential component a stretched polyester short fiber having a fiber diameter of less than 3 µm and an unstretched polyester short fiber having a fiber diameter of 3 µm or more and 5 µm or less. It is characterized by being a wet nonwoven fabric having a density of not more than 7 g/m 2 and a density of 0.5 to 0.8 g/cm 3.

In general, in the metal coating treatment on a wet nonwoven fabric, if the specific surface area (surface area per unit volume) of the fibers forming the wet nonwoven fabric is small, the amount of metal adhesion per unit volume decreases, and excellent electromagnetic shielding properties cannot be expressed. There are cases. The nonwoven fabric <2> for electromagnetic wave shielding material of the present invention is a wet nonwoven fabric containing as essential components a stretched polyester short fiber having a fiber diameter of less than 3 µm and an unstretched polyester short fiber having a fiber diameter of 3 µm or more and 5 µm or less. Therefore, the specific surface area can be increased, and excellent electromagnetic shielding properties can be expressed. When the wet-type nonwoven fabric is composed of only short stretched polyester fibers having a fiber diameter of 3 µm or more and short unstretched polyester fibers having a fiber diameter exceeding 5 µm, excellent electromagnetic wave shielding properties cannot be exhibited. Further, it is difficult to obtain unstretched polyester-based short fibers having a fiber diameter of less than 3 µm. Further, it is preferable that the fiber diameter of the stretched polyester-based short fibers having a fiber diameter of less than 3 µm is 0.1 µm or more. When the fiber diameter is less than 0.1 µm, strength may not be expressed.

In the nonwoven fabric <2> for electromagnetic wave shielding materials of the present invention, the mass content ratio of the stretched polyester short fibers and the unstretched polyester short fibers is preferably 20:80 to 80:20, and 30:70 to 70 : It is more preferable that it is 30, and it is still more preferable that it is 40:60-60:40. When the content rate of the unstretched polyester-based short fibers is less than 20% by mass of the total fiber constituting the wet nonwoven fabric, the strength required as the nonwoven fabric for electromagnetic wave shielding materials may not be expressed. On the other hand, when the content rate of the unstretched polyester-based short fibers exceeds 80% by mass, uniformity may be impaired.

In the nonwoven fabric <2> for electromagnetic wave shielding materials of the present invention, fibers other than 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 may be used. That is, a stretched polyester short fiber having a fiber diameter of 3 µm or more, an unstretched polyester short fiber having a fiber diameter of less than 3 µm, and an unstretched polyester short fiber having a fiber diameter exceeding 5 µm may be used. These may be used alone, or two or more types of fibers having a fiber diameter may be used in combination.

In the nonwoven fabric <2> for an electromagnetic shielding material of the present invention, for a stretched polyester short fiber having a fiber diameter of less than 3 μm, the content is preferably 1 to 100% by mass among all stretched polyester short fibers. It is more preferable that it is 3-100 mass %. When the content ratio of the stretched 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 excellent electromagnetic shielding properties may be difficult to express.

In addition, in the nonwoven fabric <2> for an electromagnetic wave shielding material of the present invention, for unstretched polyester short fibers having a fiber diameter of 3 μm or more and 5 μm or less, the content rate is 1 to 100 mass% is preferable, and 2-100 mass% is more preferable. When the content of the unstretched polyester-based 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, making it difficult to express excellent electromagnetic shielding properties, or, There are cases where it becomes difficult to express the strength of the excellent wet nonwoven fabric.

In the nonwoven fabric <2> for electromagnetic wave shielding materials of the present invention, the apparent weight of the wet nonwoven 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 apparent weight exceeds 7 g/m 2, it becomes thicker after the metal coating treatment, and there is a possibility that the thickness of the electromagnetic wave shielding material exceeds 15 µm, and thus it may not be used in electronic devices, communication devices, telephone products, and the like. Moreover, it is preferable that the bulk weight of a wet-type nonwoven fabric is 3 g/m 2 or more. In addition, the apparent weight was measured by the method described in JIS P 8124:2011.

In the nonwoven fabric <2> for an electromagnetic wave shielding material of the present invention, the density of the wet nonwoven fabric is 0.5 to 0.8 g/cm 3, more preferably 0.55 to 0.65 g/cm 3. When the density is 0.8 g/cm 3 or less, since the specific surface area is increased, the metal film by the metal film treatment increases, and the electromagnetic wave shielding property is improved. Moreover, it becomes difficult to peel a metal film. In addition, when the density is 0.5 g/cm 3 or more, the strength of the wet nonwoven fabric is increased, the problem is less likely to occur in the metal film treatment, and the metal film is less likely to be peeled off. In addition, the density was measured by the method described in JIS P 8118:2014.

―Non-woven fabric for electromagnetic shielding material <3>―

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

In the nonwoven fabric for electromagnetic wave shielding material <3> of the present invention, the peel strength (vertical direction) of the nonwoven fabric for electromagnetic wave shielding material is 2.0 N/m or more, more preferably 2.5 N/m or more, and even more preferably 3.0 N/m. m or more. In the case where the peel strength (vertical direction) is less than 2.0 N/m, the adhesion between the fibers is too weak, resulting in increased fiber loss from the nonwoven fabric for electromagnetic shielding material during alkali treatment, and the accumulation of fibers on the conveying roll, etc. Therefore, there arises a problem that periodic cleaning is required and operability is deteriorated, and a problem occurs in that a defect in the metal plating treatment occurs due to the detached fiber being reattached to the nonwoven fabric for electromagnetic wave shielding material. In the nonwoven fabric for electromagnetic wave shielding materials <3> of the present invention, the peel strength (vertical direction) of the nonwoven fabric for electromagnetic wave shielding materials is preferably 10.0 N/m or less. When it exceeds 10.0 N/m, the fusion bonding of the nonwoven fabric for electromagnetic wave shielding material proceeds excessively, and the surface of the nonwoven fabric for electromagnetic wave shielding material is formed into a film, and the shape may not be maintained.

In the nonwoven fabric <3> for electromagnetic wave shielding materials of the present invention, the fiber diameter of the stretched polyester short fibers is preferably 1 to 10 µm, more preferably 2 to 8 µm. As the stretched polyester short fibers, two or more types of stretched polyester short fibers having different fiber diameters may be contained. When the fiber diameter of the stretched polyester-based short fibers is 10 µm or less, it becomes easy to provide a thin electromagnetic wave shielding material. Further, preferably, it is preferable to contain as an essential component a polyester-based short fiber having a fiber diameter of 3 µm or less as a stretched polyester-based short fiber. By containing the polyester-based short fibers having a fiber diameter of 3 µm or less, electromagnetic wave shielding properties are further improved.

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

In the nonwoven fabric <3> for electromagnetic wave shielding materials of the present invention, the mass content ratio of the stretched polyester short fibers and the unstretched polyester short fibers is preferably from 20:80 to 80:20. When the content rate of the unstretched polyester-based short fibers is less than 20% by mass of the total fiber constituting the wet nonwoven fabric, the strength required as the nonwoven fabric for electromagnetic wave shielding materials may not be expressed. On the other hand, when the content rate of the unstretched polyester-based short fibers exceeds 80% by mass, uniformity may be impaired. Further, in order to improve the electromagnetic wave shielding property, it is more preferable that the content of the stretched polyester-based short fibers having a fiber diameter of 3 µm or less is 5 to 80 mass% of the entire fiber constituting the wet nonwoven fabric. In the nonwoven fabric <3> for an electromagnetic wave shielding material of the present invention, the most preferable fiber blending is a stretched polyester short fiber having 20 to 80 mass% of unstretched polyester short fiber and a fiber diameter exceeding 3 µm and not more than 10 µm. Is 0 to 75% by mass, and 5 to 80% by mass of oriented polyester short fibers having a fiber diameter of 3 μm or less.

The thickness of the nonwoven fabric <3> for electromagnetic shielding materials of the present invention is preferably 5 to 30 µm, and more preferably 20 µm or less, for use in electronic devices. It is preferable that it is 3-30 g/m<2>, and, as for the apparent weight (base weight), it is more preferable that it is 15 g/m<2> or less. If the apparent weight is less than 3 g/m 2, it becomes difficult to obtain uniformity, and unevenness is liable to occur in the effect of electromagnetic shielding properties, and it becomes difficult to maintain the strength of the nonwoven fabric for electromagnetic shielding material itself, resulting in difficulty in workability.

―Polyester-based short fibers―

In the present invention, the stretched polyester-based short fibers are hardly melted or softened even by thermal calendering, and are main fibers that form the skeleton of a wet nonwoven fabric.

In the present invention, the unstretched polyester-based short fibers are melted or softened by thermal calendering to function as a binder fiber that increases the strength of the wet nonwoven fabric. The melting point of the unstretched polyester short fiber is preferably 220°C to 250°C. In the nonwoven fabric <3> for electromagnetic wave shielding materials of the present invention, the melting point of the unstretched polyester short fibers is 220°C or more and 250°C or less. When the melting point of the unstretched polyester-based short fibers is less than 220°C, a wet nonwoven fabric is affixed to the heat roll during the heat calendering treatment, and thus the sheet may not be formed. When it exceeds 250 degreeC, the fiber may not adhere and the strength of a wet nonwoven fabric may not be expressed. The melting point of the unstretched polyester short fibers is more preferably 225°C or more and 250°C or less.

The melting point of the unstretched polyester short fiber is a 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 with a differential scanning calorimetry device.

In addition, in the examples of the present invention, the fiber diameter of the polyester-based short fibers describes the fiber diameter before manufacturing the nonwoven fabric. The fiber diameter of a polyester-based short fiber is a diameter calculated by taking an enlarged photograph of a cross section of a wet nonwoven fabric or electromagnetic wave shielding material 3000 times larger under a microscope, measuring the cross-sectional area of the polyester-based short fiber, and taking the cross-sectional shape of the fiber as a true circle. It can be measured as, and in that case, it is preferable to obtain the arithmetic average value of 10 or more fibers having approximately 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 still more preferably 2 to 8 mm. When the fiber length of the polyester-based short fibers is less than 1 mm, the strength required as a wet nonwoven fabric may be difficult to express. When the fiber length of the polyester-based short fibers exceeds 20 mm, 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. The polyester-based short fibers are preferable from the fact that the fiber diameter can be made small in order to make the thickness of the electromagnetic shield thin, the ease of papermaking, and the dimensional stability during the wet alkali treatment in the plating treatment. The polyester-based short fibers may be used alone or in combination of two or more.

―Wet-type non-woven fabric―

As a method of forming a fiber into a sheet, various manufacturing methods such as a spun bond method, a melt blow method, an electrostatic spinning method, and a wet method may be mentioned, but the nonwoven fabric for electromagnetic wave shielding material of the present invention is formed into a sheet by a wet method (papermaking method). It is a formed wet nonwoven fabric, which has excellent strength and high uniformity. Moreover, various methods, such as a chemical bonding method and a thermal fusion method, are mentioned as a method of bonding between fibers. Among these, since it is excellent in durability and strength, and the surface of the nonwoven fabric is smooth, a thermal fusion method is preferable.

As the thermal fusion method in the wet method, a method of thermally fusion bonding the sheet obtained by the papermaking method when thermally drying with a dryer used after papermaking, such as a multi-cylinder dryer, a Yankee dryer, or an air-through dryer, can be used. In addition, a method of thermally fusion bonding by thermal calendering using a thermal calendering device having a roll combination such as a metal heat roll/metal heat roll, a metal heat roll/elastic roll, and a metal heat roll/cotton roll can also be used. By thermal drying or thermal calendering, the binder component is thermally melted and thermal fusion occurs.

In addition, although the conditions of a thermal calender can be illustrated below, it is not limited to these. The temperature of the heat roll in the thermal calendering treatment is preferably 200°C or more and 215°C or less. When 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 thus the strength is not exhibited. On the contrary, when the temperature of the heat roll is more than 215°C, a problem that a wet nonwoven fabric is affixed to the heat roll may arise, and a sheet may not be formed. The temperature of the heat roll is more preferably 203°C or more and 210°C or less, and still more preferably 205°C or more. In addition, in the nonwoven fabric for electromagnetic wave shielding material <3> of the present invention, in order to increase the peel strength of the nonwoven fabric for electromagnetic wave shielding material, short stretched polyester fibers and short unstretched polyester fibers having a melting point of 220°C to 250°C are contained. It is preferable that the wet nonwoven fabric is subjected to thermal calendering using a heat roll having a temperature of 200°C or more and 215°C or less. The temperature of a more preferable heat roll is 203 degreeC or more and 210 degreeC or less.

In order to express the strength, the pressure (line pressure) in the thermal calendering treatment is preferably 50 to 250 kN/m, more preferably 80 to 150 kN/m. When the pressure is less than 50 kN/m, there is a possibility that the smoothness of the surface is impaired, and if the speed is not lowered, there is a possibility that the thickness does not become thin. If the pressure exceeds 250 kN/m, there is a possibility that the sheet cannot withstand the pressure and break. The processing speed of the thermal calender is preferably 1 to 300 m/min. When the processing speed is 1 m/min or more, the work efficiency becomes good. By setting the treatment speed to 300 m/min or less, heat is conducted to the wet nonwoven fabric, and the effect of thermal fusion becomes easy to be obtained. The number of nips of the thermal calender is not particularly limited as long as it can conduct heat to the wet nonwoven fabric, but in the combination of a metal heat roll/elastic roll, in order to conduct heat from the front and back of the wet nonwoven fabric, it may be nip twice or more.

―Electromagnetic shielding material―

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

In the present invention, examples of the metal coating treatment include electroless metal plating treatment, electroplating treatment, metal vapor deposition treatment, sputtering treatment, and the like. One or more treatments selected from these treatments can be performed. Among them, it is preferable to perform electroplating treatment after sputtering treatment, since it can be made thin, the surface resistance value tends to be low, and the metal film becomes difficult to peel off. One layer may be sufficient as the said metal film, and multiple layers may be sufficient as two or more layers.

Examples of metals used in the metal coating treatment include gold, silver, copper, zinc, aluminum, nickel, tin, or alloys thereof. Among them, at least one metal selected from the group consisting of gold, silver, copper, aluminum, nickel and tin is 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 coating treatment includes, in this 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 a wet nonwoven fabric by sputtering. Nickel is preferable as the metal in the sputtering treatment. After the sputtering treatment, a metal film is deposited by electroplating. The metal for electroplating is preferably copper. Further, for rust prevention, a metal having good rust prevention properties, such as nickel, may be laminated on the outer layer. The lamination method is preferably an electroplating method.

The thickness of the electromagnetic 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 shielding material is larger than 15 µm, it may not be used in electronic devices, communication devices, telephone products, and the like. Moreover, it is preferable that the thickness of an electromagnetic wave shielding material is 7 micrometers or more. In addition, the thickness was measured by the method described in JIS P 8118:2014.

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

Example

Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited at all by these examples. In addition, in Examples,% and parts are all based on mass unless otherwise noted.

≪Example concerning the nonwoven fabric <1> for electromagnetic wave shielding material of the present invention≫

[Example 1]

Stretched PET-based short fiber with a fineness of 0.3 dtex (fiber diameter 5.3 µm) and a fiber length of 3 ㎜ stretched polyethylene terephthalate (PET)-based short fiber, and a oriented PET-based short fiber with a fineness of 0.6 dtex (fiber diameter of 7.4 µm) and a fiber length of 5 mm 30 parts by mass, fineness 0.2 dtex (fiber diameter: 4.3 µm), and 40 parts by mass of unstretched PET-based short fibers having a fiber length of 3 mm are dispersed in water with a pulper for uniform papermaking having a concentration of 1% by mass. A slurry was prepared. This papermaking slurry was lifted up by a wet method with an inclined paper machine equipped with a papermaking wire having an air permeability of 275 cm3/cm2/sec and a structure [upper net: plain weave, bottom net: nonwoven], and then floated in a cylinder dryer at 135°C. Thus, the unstretched PET-based short fibers were thermally fused to express strength, thereby obtaining a wet nonwoven fabric having an apparent weight of 10 g/m 2. In addition, this wet-type nonwoven fabric was subjected to a heat 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 calender device consisting of a dielectric heating jacket roll (metal heat roll) and an elastic roll. Thermal calendering was performed to prepare a nonwoven fabric for electromagnetic wave shielding materials having a thickness of 15 µm.

[Example 2]

A fineness of 0.3 dtex (fiber diameter 5.3 µm), a fiber length of 3 mm, 10 parts by mass of a stretched PET short fiber, a fineness of 0.6 dtex (fiber diameter of 7.4 µm), a fiber length of 5 mm, a stretched PET-based short fiber 50 parts by mass, A nonwoven fabric for an electromagnetic wave shielding material having a thickness of 17 µm was produced in the same manner as in Example 1, except that the fineness was 0.2 dtex (fiber diameter: 4.3 µm) and 40 parts by mass of the unstretched PET-based short fiber having a fiber length of 3 mm.

[Example 3]

A fineness of 0.3 dtex (fiber diameter 5.3 µm), a fiber length of 3 mm, 50 parts by mass of a stretched PET short fiber, a fineness of 0.6 dtex (fiber diameter of 7.4 µm), a fiber length of 5 mm, a stretched PET-based short fiber 10 parts by mass, A nonwoven 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 fineness was 0.2 dtex (fiber diameter: 4.3 µm) and 40 parts by mass of the unstretched PET-based short fiber having a fiber length of 3 mm.

[Example 4]

A fineness of 0.3 dtex (fiber diameter 5.3 µm), a fiber length of 3 mm oriented PET-based short fibers 45 mass parts, a fineness of 0.6 dtex (fiber diameter of 7.4 µm), a fiber length of 5 mm oriented PET-based short fibers 45 parts by mass, A nonwoven 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 10 parts by mass of unstretched PET-based short fibers having a fiber length of 3 mm.

[Example 5]

A fineness of 0.1 dtex (fiber diameter 3.0 µm), a fiber length of 3 mm, 30 parts by mass of a stretched PET short fiber, a fineness of 0.6 dtex (fiber diameter of 7.4 µm), a fiber length of 5 mm, a stretched PET-based short fiber 30 parts by mass, A nonwoven 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 40 parts by mass of the unstretched PET-based short fiber having a fiber length of 3 mm.

[Example 6]

A fineness of 0.1 dtex (fiber diameter 3.0 µm), a fiber length of 3 mm oriented PET-based short fibers 10 mass parts, a fineness of 0.3 dtex (fiber diameter 5.3 µm), a fiber length of 3 mm oriented PET-based short fibers 30 parts by mass, A fineness of 0.6 dtex (fiber diameter 7.4 µm) and a fiber length of 5 mm in 30 parts by mass of stretched PET short fibers, a fineness of 0.2 dtex (fiber diameter of 4.3 µm) and a fiber length of 3 mm in 30 parts by mass of unstretched PET short fibers. Except for that, in the same manner as in Example 1, a nonwoven fabric for electromagnetic wave shielding materials having a thickness of 14 µm was produced.

[Example 7]

A fineness of 0.3 dtex (fiber diameter 5.3 µm), a fiber length of 3 mm, 30 parts by mass of a stretched PET short fiber, a fineness of 0.6 dtex (fiber diameter of 7.4 µm), a fiber length of 5 mm, a stretched PET-based short fiber 30 parts by mass, A fineness of 1.7 dtex (fiber diameter 12.0 µm) and a fiber length of 5 mm in 10 parts by mass of stretched PET short fibers, fineness of 0.2 dtex (fiber diameter of 4.3 µm) and a fiber length of 3 mm in unstretched PET-based short fibers 30 parts by mass. Except for that, in the same manner as in Example 1, a nonwoven fabric for electromagnetic wave shielding materials having a thickness of 16 µm was produced.

[Example 8]

A fineness of 0.06 dtex (fiber diameter 2.4 µm), a fiber length of 3 mm oriented PET-based short fibers 10 mass parts, a fineness of 0.3 dtex (fiber diameter 5.3 µm), a fiber length of 3 mm oriented PET-based short fibers 30 parts by mass, A fineness of 0.6 dtex (fiber diameter 7.4 µm) and a fiber length of 5 mm in 30 parts by mass of stretched PET short fibers, a fineness of 0.2 dtex (fiber diameter of 4.3 µm) and a fiber length of 3 mm in 30 parts by mass of unstretched PET short fibers. Except for that, in the same manner as in Example 1, a nonwoven fabric for electromagnetic wave shielding materials having a thickness of 14 µm was produced.

[Example 9]

A fineness of 0.3 dtex (fiber diameter 5.3 µm), a fiber length of 3 mm, 30 parts by mass of a stretched PET short fiber, a fineness of 0.6 dtex (fiber diameter of 7.4 µm), a fiber length of 5 mm, a stretched PET-based short fiber 30 parts by mass, With a fineness of 0.2 dtex (fiber diameter of 4.3 µm) and a fiber length of 3 mm, 30 parts by mass of undrawn PET-based short fibers, a fineness of 1.2 dtex (fiber diameter of 10.5 µm), and a fiber length of 5 mm in 10 parts by mass of undrawn PET-based short fibers. A nonwoven fabric for electromagnetic wave shielding materials having a thickness of 16 µm was produced in the same manner as in Example 1 except for the one.

[Example 10]

15 parts by mass of stretched PET-based short fibers having a fineness of 0.3 dtex (fiber diameter 5.3 µm) and a fiber length of 3 mm, and 15 parts by mass of oriented PET-based short fibers having a fineness of 0.6 dtex (fiber diameter of 7.4 µm) and a fiber length of 5 mm, A nonwoven 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 70 parts by mass of the unstretched PET-based short fiber having a fiber length of 3 mm.

[Comparative Example 1]

A fineness of 0.3 dtex (fiber diameter 5.3 µm), a fiber length of 3 mm, 30 parts by mass of a stretched PET short fiber, a fineness of 0.6 dtex (fiber diameter of 7.4 µm), a fiber length of 5 mm, a stretched PET-based short fiber 30 parts by mass, A nonwoven 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 1.2 dtex (fiber diameter 10.5 µm) and 40 parts by mass of unstretched PET-based short fibers having a fiber length of 5 mm.

[Comparative Example 2]

The fineness of 0.3 dtex (fiber diameter 5.3 µm), fiber length 3 ㎜ stretched PET-based short fiber 60 parts, fineness 0.2 dtex (fiber diameter 4.3 µm), fiber length 3 ㎜ unstretched PET-based short fiber 40 parts by mass Except for that, in the same manner as in Example 1, a nonwoven fabric for electromagnetic wave shielding materials having a thickness of 15 µm was produced.

[Comparative Example 3]

A fineness of 1.7 dtex (fiber diameter 12.0 µm), a fiber length of 5 mm in 30 parts by mass of a stretched PET short fiber, a fineness of 3.3 dtex (fiber diameter of 17.5 µm), a fiber length of 5 mm in a stretched PET-based short fiber 30 parts by mass, A nonwoven 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 40 parts by mass of the unstretched PET-based short fiber having a fiber length of 3 mm.

[Comparative Example 4]

A fineness of 1.7 dtex (fiber diameter 12.0 µm), a fiber length of 5 mm in 60 parts by mass of a stretched PET short fiber, a fineness of 0.2 dtex (fiber diameter of 4.3 µm), a fiber length of 3 mm in an unstretched PET-based short fiber 40 parts by mass. Except for that, in the same manner as in Example 1, a nonwoven fabric for an electromagnetic wave shielding material having a thickness of 18 µm was produced.

[Comparative Example 5]

A fineness of 0.1 dtex (fiber diameter 3.0 µm) and a fiber length of 3 ㎜ stretched PET-based short fiber 60 parts, fineness 0.2 dtex (fiber diameter of 4.3 µm) and a fiber length of 3 ㎜ unstretched PET-based short fiber 40 parts by mass. Except for that, in the same manner as in Example 1, a nonwoven fabric for electromagnetic wave shielding materials having a thickness of 15 µm was produced.

The nonwoven 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 sequentially laminated by an electroplating method to prepare an electromagnetic wave shielding material.

<Evaluation>

[Transportability]

The nonwoven fabric for electromagnetic shielding material was conveyed with a constant tension, and the occurrence of wrinkles at that time was evaluated based on the following criteria.

"○" wrinkles do not occur, and transportability is very good.

"Δ" Wrinkles are formed in a part of the nonwoven fabric for electromagnetic wave shielding material, but there is no problem in transportability.

To the extent that "x" processing is impossible, wrinkles are formed in the entire nonwoven fabric for electromagnetic wave shielding materials, and conveyance properties are inferior.

[Electromagnetic shielding (electric field)]

It measured based on electromagnetic wave shielding property (electric field) by the coaxial tube method. In the range of the frequency of 40 MHz to 3 GHz, the measurement was performed by the coaxial tube method 39D, and in the range of the frequency of 500 MHz to 18 GHz, the measurement was performed by the coaxial tube method GPC7. The frequencies of 500 MHz to 3 GHz were measured by both the coaxial tube method 39D and the coaxial tube method GPC7, but a lower value was employed.

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

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

In contrast, two or more oriented polyester-based short fibers having different fiber diameters selected from oriented polyester-based short fibers having a fiber diameter of 3 µm or more and less than 12 µm, and undrawn polyester having a fiber diameter of 3 µm or more and 5 µm or less The nonwoven fabrics for electromagnetic wave shielding materials of Comparative Examples 1, 2, 3 and 4 that did not contain the stepped fiber as an essential component were inferior to the electromagnetic wave shielding property. That is, two kinds of drawing with different fiber diameters selected from the nonwoven fabric for electromagnetic wave shielding material of Comparative Example 1 in which the fiber diameter of the unstretched polyester short fiber is more than 5 µm, and the stretched polyester short fiber having a fiber diameter of 12 µm or more. The nonwoven fabric for electromagnetic wave shielding material of Comparative Example 3 containing the short polyester fiber, the nonwoven fabric for electromagnetic wave shielding material of Comparative Example 4 in which the fiber diameter of the stretched polyester short fiber is 12 µm, and the fiber diameter of 3 µm or more and 12 µm The non-woven fabric for electromagnetic wave shielding material of Comparative Example 2 containing only one type of stretched polyester short fiber having the same fiber diameter (fiber diameter 5.3 µm), which contains less than the stretched polyester short fiber, has reduced multiple reflection losses. I think it was done.

In addition, the electromagnetic wave of Comparative Example 5 containing only one type of stretched polyester short fiber having the same fiber diameter (fiber diameter 3.0 μm), although it contains stretched polyester short fibers having a fiber diameter of 3 µm or more and less than 12 µm. In the nonwoven fabric for shielding materials, wrinkles occur during transport of the web, and the transportability is inferior. It is considered that by containing only the stretched polyester-based short fibers having a small fiber diameter, the web becomes flexible, is easily stretched, and wrinkles are more likely to occur.

≪Example concerning the nonwoven fabric <2> for electromagnetic wave shielding material of the present invention≫

<Evaluation>

(1) Surface resistance value

Measured based on MIL DTL 83528C.

(2) Electromagnetic shielding (electric field)

It measured based on electromagnetic wave shielding property (electric field) by the coaxial tube method. In the range of the frequency of 40 MHz to 3 GHz, the measurement was performed by the coaxial tube method 39D, and in the range of the frequency of 500 MHz to 18 GHz, the measurement was performed by the coaxial tube method GPC7. The frequencies of 500 MHz to 3 GHz were measured by both the coaxial tube method 39D and the coaxial tube method GPC7, but a lower value was employed.

(3) Peel evaluation

An adhesive tape (Nitto (registered trademark) 31B tape, manufactured by Nitto Electric Co., Ltd.) was affixed to a sample of an electromagnetic wave shielding material having a width of 25 mm and a length of 150 mm, and rolled 10 times at a speed of 300 mm/min with a 2 kg roll. After that, the tape and the sample are separated at an angle of 180 degrees and peeled at a speed of 1000 mm/min. It evaluated according to the following criteria.

<Standard>

○: Measured three times, and there was no fracture of the sample and no adhesion of metal powder to the tape.

?: Measurement was performed 3 times, and fracture of the sample and adhesion of the metal powder to the tape occurred 1 to 2 times.

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

[Example 11]

Stretched PET-based short fibers with a fineness of 0.06 dtex (fiber diameter of 2.4 µm) and a fiber length of 3 mm, 20 parts by mass of stretched polyethylene terephthalate (PET)-based short fibers and a fineness of 0.3 dtex (fiber diameter of 5.3 µm) and a fiber length of 3 mm 40 parts by mass, fineness 0.2 dtex (fiber diameter 4.3 µm), fiber length 3 mm for single-component binder 40 parts by mass of undrawn PET-based short fibers are dispersed in water with a pulper for uniform papermaking with a concentration of 1% by mass A slurry was prepared. This papermaking slurry was lifted up by a wet method with an inclined paper machine equipped with a papermaking wire having an air permeability of 275 cm3/cm2/sec and a structure [upper mesh: plain weave, bottom mesh: nonwoven], and used for binders by a 135°C cylinder dryer. The unstretched PET-based short fibers were thermally fused to express strength to obtain a wet nonwoven fabric. In addition, this wet-type nonwoven fabric was heated under conditions of a heat roll temperature of 200°C and a linear pressure of 100 kN/m and a processing speed of 100 m/min by using a one-nip thermal calender device consisting of a dielectric heating jacket roll (metal heat roll) and an elastic roll By calendering, a nonwoven fabric for an electromagnetic wave shielding material having an apparent weight of 6.5 g/m 2 and a density of 0.50 g/cm 3 was produced.

Next, the electromagnetic shielding nonwoven fabric was covered with a nickel film by electroless plating treatment, and then a copper film and a nickel film were sequentially laminated by electroplating treatment, followed by a metal film treatment, and a thickness of 17.5 μm. To obtain an electromagnetic shielding material.

[Example 12]

The fiber blends were drawn PET-based short fibers having a fineness of 0.06 dtex (fiber diameter 2.4 µm) and a fiber length of 3 mm, and a stretched PET-based short fibers having a fineness of 0.3 dtex (fiber diameter of 3.0 µm) and a fiber length of 3 mm. A wet nonwoven fabric was obtained in the same manner as in Example 11, except that parts by mass, fineness of 0.2 dtex (fiber diameter: 4.3 µm) and fiber length of 3 mm were used as 40 parts by mass of unstretched PET-based short fibers for a single component type binder. Except having made this wet-type nonwoven fabric under conditions of a treatment speed of 50 m/min, heat calendering treatment was performed in the same manner as in Example 11 to produce a nonwoven fabric for electromagnetic wave shielding materials having an apparent weight of 6.5 g/m 2 and a density of 0.63 g/cm 3. Next, metal coating 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 blend was used for a single-component binder with a fineness of 0.06 dtex (fiber diameter 2.4 µm) and a stretched PET-based short fiber having a fiber length of 3 mm, and a fineness of 0.2 dtex (fiber diameter: 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 new PET-based short fibers were used. Heat calendering was performed in the same manner as in Example 11, except that this wet nonwoven fabric was subjected to a line pressure of 125 kN/m and a treatment speed of 40 m/min, and an electromagnetic wave shield having an apparent weight of 6.5 g/m 2 and a density of 0.80 g/cm 3 A re-use nonwoven fabric was produced. Next, metal coating 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]

Except having set it as an apparent weight of 5.0 g/m 2, it carried out similarly to Example 11, and obtained the wet-type nonwoven fabric. This wet nonwoven fabric was subjected to thermal calendering treatment in the same manner as in Example 13 to produce a nonwoven fabric for electromagnetic wave shielding materials having a density of 0.80 g/cm 3. Subsequently, the nonwoven fabric for electromagnetic wave shielding material was covered with a nickel film by sputtering treatment, a copper film and a nickel film were sequentially laminated by electroplating treatment, and a metal film treatment was performed to obtain an electromagnetic wave shielding material having a thickness of 8.5 μm. .

[Example 15]

A wet nonwoven fabric was obtained in the same manner as in Example 12 except that the apparent weight was 5.0 g/m 2. This wet nonwoven fabric was subjected to thermal calendering treatment in the same manner as in Example 11 to produce a nonwoven fabric for electromagnetic wave shielding materials having a density of 0.50 g/cm 3. Next, the metal coating treatment was performed on the nonwoven fabric for electromagnetic wave shielding material 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 apparent weight was 5.0 g/m 2. This wet nonwoven fabric was subjected to thermal calendering treatment in the same manner as in Example 12 to prepare a nonwoven fabric for electromagnetic wave shielding materials having a density of 0.63 g/cm 3. Next, metal coating 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 blend was used for a single component binder with a fineness of 0.3 dtex (fiber diameter 5.3 µm) and a stretched PET-based short fiber having 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. A wet nonwoven fabric having an apparent weight of 10.0 g/m 2 was obtained in the same manner as in Example 11 except that 40 parts by mass of the new PET-based short fibers were used. Except having made this wet-type nonwoven fabric under conditions of a line pressure of 135 kN/m and a treatment speed of 40 m/min, heat calendering was performed in the same manner as in Example 11 to produce a nonwoven fabric for electromagnetic wave shielding materials having a density of 0.85 g/cm 3. Next, metal coating 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 nonwoven fabric for electromagnetic wave shielding materials having an apparent 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 conditions of the line pressure of 100 kN/m and the treatment speed of 50 m/min were set. Next, metal coating 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 nonwoven fabric for an electromagnetic wave shielding material having an apparent weight of 10.0 g/m2 and a density of 0.45 g/cm3 was produced in the same manner as in Comparative Example 11, except that the conditions were 90 kN/m and a treatment speed of 100 m/min. Next, metal coating treatment was performed in the same manner as in Comparative Example 11 to obtain an electromagnetic wave shielding material having a thickness of 26.0 µm.

[Comparative Example 14]

In the same manner as in Comparative Example 11, a nonwoven fabric for electromagnetic wave shielding materials having an apparent weight of 10.0 g/m 2 and a density of 0.85 g/cm 3 was produced. Next, metal coating 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 nonwoven fabric for electromagnetic wave shielding materials having an apparent weight of 10.0 g/m 2 and a density of 0.63 g/cm 3 was produced. Next, metal coating treatment was performed in the same manner as in Comparative Example 14 to obtain an electromagnetic wave shielding material having a thickness of 20.0 µm.

[Comparative Example 16]

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

It contains as essential components a stretched polyester short fiber with a fiber diameter of less than 3 µm and an unstretched polyester short fiber having a fiber diameter of 3 µm or more and 5 µm or less, and has an apparent weight of 7 g/m 2 or less, and a density of 0.5 to Examples 11 to 16, which are electromagnetic wave shielding materials obtained by subjecting a nonwoven fabric for an electromagnetic wave shielding material, which is a 0.8 g/cm 3 wet nonwoven fabric, to a metal film treatment, are excellent in electromagnetic wave shielding properties, and the effect that the metal film is difficult to peel was achieved. In addition, the metal coating treatment includes, in this 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 in this order, and the thickness is 15 μm or less. And, compared with the electromagnetic wave shielding material of Examples 11 to 13, the electromagnetic wave shielding material of Examples 14 to 16 having a surface resistance value of 0.03 Ω/□ or less is superior to the electromagnetic wave shielding material of Examples 11 to 13, and the metal film is more difficult to peel off. I can see that.

Comparative Examples 11 to 16 contain a stretched PET-based short fiber having a fiber diameter of 3 µm or more and an unstretched PET-based short fiber having a fiber diameter of more than 5 µm, and a wet nonwoven fabric having an apparent weight of more than 7 g/m 2. It is an electromagnetic wave shielding material obtained by subjecting a reusable nonwoven fabric to a metal coating treatment. In Comparative Examples 11 and 13, in which the metal coating treatment includes a treatment of forming a nickel coating by sputtering, a treatment of forming a copper coating by electroplating, and a treatment of forming a nickel coating by electroplating in this order, The results of electromagnetic shielding and peel evaluation were bad. The electromagnetic shielding material of Comparative Example 12 had good electromagnetic shielding properties and peel evaluation, but the thickness of the electromagnetic shielding material was 20.0 µm, and it could not be made thin. In Comparative Examples 14 to 16, a nickel film was covered by electroless plating treatment, and then a copper film and a nickel film were sequentially laminated by electroplating treatment, and a metal film treatment was performed, and the result of peel evaluation. Was good, but the electromagnetic shielding property was poor.

≪Example concerning the nonwoven fabric <3> for electromagnetic wave shielding material of the present invention≫

[Example 21]

Stretched PET-based short fiber with a fineness of 0.6 dtex (fiber diameter 7.4 µm) and a fiber length of 5 ㎜ stretched polyethylene terephthalate (PET)-based short fiber, and a oriented PET-based short fiber with a fineness of 0.3 dtex (fiber diameter 5.3 µm) and a fiber length of 3 ㎜ 30 parts by mass, fineness 0.2 dtex (fiber diameter 4.3 µm), fiber length 3 mm, and 40 parts by mass of undrawn PET-based short fibers for a single component type binder having a melting point of 246°C are dispersed in water with a pulper, and the concentration is 1% by mass. A uniform slurry for papermaking was prepared. This papermaking slurry was lifted up by a wet method with an inclined paper machine equipped with a papermaking wire having an air permeability of 275 cm3/cm2/sec and a structure [upper mesh: plain weave, bottom mesh: nonwoven], and used for binders by a 135°C cylinder dryer. The unstretched PET-based short fibers were thermally fused to develop strength to obtain a wet nonwoven fabric having an apparent weight of 10 g/m 2. In addition, this wet-type nonwoven fabric was subjected to a heat roll temperature of 202°C, a linear pressure of 100 kN/m, and a processing speed of 40 m/min using a one-nip thermal calender device consisting of a dielectric heating jacket roll (metal heat roll) and an elastic roll. Thermal calendering was performed to prepare a nonwoven fabric for electromagnetic wave shielding materials having a thickness of 15 µm and a peel strength of 2.1 N/m.

[Example 22]

A nonwoven fabric for electromagnetic wave shielding materials 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 heat roll temperature was set to 208°C.

[Example 23]

A nonwoven fabric for electromagnetic wave shielding materials 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 heat roll temperature was set to 205°C.

[Example 24]

The blending of the stretched polyester short fibers, having a fineness of 0.6 dtex (fiber diameter 7.4 µm) and a fiber length of 3 mm oriented PET-based short fibers 30 parts by mass, a fineness of 0.1 dtex (fiber diameter 3.0 µm), and a fiber length of 3 mm. A nonwoven fabric for electromagnetic shielding materials 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 that 30 parts by mass of stretched PET-based short fibers were used.

[Example 25]

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

[Example 26]

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

[Example 27]

The blending of the stretched polyester short fibers was prepared with a fineness of 0.3 dtex (fiber diameter 5.3 μm), a fiber length of 3 mm, 30 parts by mass of stretched PET short fibers, a fineness of 0.06 dtex (fiber diameter: 2.4 μm), and a fiber length of 3 mm. A nonwoven fabric for electromagnetic shielding materials having a thickness of 15 µm and a peel strength of 3.3 N/m was produced in the same manner as in Example 23 except that 30 parts by mass of stretched PET-based short fibers were used.

[Example 28]

The blending of the stretched polyester short fibers was prepared with a fineness of 0.1 dtex (fiber diameter 3.0 µm), a fiber length of 3 mm, 30 parts by mass of oriented PET short fibers, a fineness of 0.06 dtex (fiber diameter of 2.4 µm), and a fiber length of 3 mm. A nonwoven fabric for electromagnetic shielding materials 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 that 30 parts by mass of stretched PET-based short fibers were used.

[Comparative Example 21]

A nonwoven fabric for electromagnetic wave shielding materials 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 roll temperature was set at 198°C.

[Comparative Example 22]

A nonwoven fabric for electromagnetic wave shielding materials 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 heat roll temperature was set to 195°C.

[Comparative Example 23]

A nonwoven fabric for electromagnetic wave shielding materials 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 roll temperature was set at 198°C.

[Comparative Example 24]

A nonwoven fabric for electromagnetic wave shielding materials 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 roll temperature was set at 198°C.

[Comparative Example 25]

The blending of the fibers was a fineness of 0.6 dtex (fiber diameter 7.4 µm), a stretched PET-based short fiber with a fiber length of 3 mm, 30 parts by mass, a fineness of 0.3 dtex (fiber diameter 5.3 µm), and a stretched PET-based short fiber having a fiber length of 3 mm. 30 parts by mass, fineness 0.1 dtex (fiber diameter 3.0 µm), fiber length 3 mm stretched PET-based short fiber 30 parts by mass, fineness 0.2 dtex (fiber diameter 4.3 µm), fiber length 3 mm, a single 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 0.2 N/m was prepared in the same manner as in Example 23, except that 10 parts by mass of unstretched PET-based short fibers for component binders were used.

[Comparative Example 26]

The blending of the fibers was a single fiber having a fineness of 0.6 dtex (fiber diameter 7.4 μm) and a stretched PET-based short fiber having a fiber length of 3 mm, and a fineness of 0.2 dtex (fiber diameter: 4.3 μm), a fiber length of 3 mm, and a 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 that 90 parts by mass of the unstretched PET-based short fiber for a component binder was used.

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

<Evaluation>

[Peel strength]

A non-woven fabric for electromagnetic wave shielding material is cut into 25 mm × 200 mm, and double-sided tape (manufactured by Nichiban, brand name: NW-R25, Nice Stack (registered trademark) low-adhesion type) is placed on a paper (manufactured by Mitsubishi Paper, brand name: N Pearl Card (registered trademark) FSC Certification-MX (450.0 g/m²)) is affixed to the non-glossy surface, from above, a nonwoven fabric for electromagnetic shielding material is superimposed, and a packaging tape (manufactured by Kamoi Industries, brand name: No. 220W) was affixed, and the peeling test was performed in the form as shown in FIG. 1, and the peeling strength was measured. In the peeling test, SHIMPO (Nippon Computerized Shimpo) manufactured, equipment name: digital force gauge FGC-2B was used, the jig distance was 1.8 cm, and there was a nonwoven fabric for electromagnetic wave shielding material at the center of the distance, and the speed was 100 mm/ It was measured under the conditions of min.

[Fiber drop-off resistance]

A nonwoven fabric for electromagnetic wave shielding material was collected, cut into 25 mm × 200 mm, and cut into 25 mm × 200 mm, using a Hakjin-type friction fastness tester, and a 500 gf of Billiken Moss (registered trademark) fabric on which a weight of 500 gf was applied, and the non-woven fabric for electromagnetic wave shielding material was 5 It was rubbed back and forth, and evaluated according to the following criteria.

“◎” Fibers do not adhere to the bilikene moss cloth

"○" Fibers hardly adhere to the bilikene moss cloth.

"Δ" The fibers are slightly attached to the biliken moss cloth, but there is no problem in practical use.

The fibers adhere to the "x" bilikene moss cloth, and in some cases, the substrate is broken.

[Defect frequency]

The frequency of defects per 1000 m when metal plating treatment was applied to the nonwoven fabric for electromagnetic wave shielding material subjected to alkali treatment as a pre-plating treatment was confirmed.

「◎」0 pieces/1000 m.

``○'' 1 piece/1000 m.

``△'' 2 pieces/1000 m.

``×'' 3 or more / 1000 m.

[Electromagnetic shielding (electric field)]

It measured based on electromagnetic wave shielding property (electric field) by the coaxial tube method. In the range of the frequency of 40 MHz to 3 GHz, the measurement was performed by the coaxial tube method 39D, and in the range of the frequency of 500 MHz to 18 GHz, the measurement was performed by the coaxial tube method GPC7. The frequencies of 500 MHz to 3 GHz were measured by both the coaxial tube method 39D and the coaxial tube method GPC7, but a lower value was employed.

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

Since the nonwoven fabric for electromagnetic wave shielding material of Examples 21 to 28 has high peel strength compared to the nonwoven fabric for electromagnetic wave shielding material of Comparative Examples 21 to 26, it has excellent fiber-resistance and less defect frequency, so the yield is good and excellent. Electromagnetic shielding properties were exhibited.

Comparing Examples 21 to 23, in Example 23 in which the hot roll temperature was 205°C, the peel strength was the highest and the fiber resistance to fall off was improved. On the other hand, in Comparative Examples 21 to 24, since the heat roll temperature was lower than 200°C, the peeling strength of the nonwoven fabric for electromagnetic wave shielding material was low, the fiber resistance was poor, and the defect frequency was very high.

In Comparative Examples 25 and 26, since the content of the unstretched polyester-based short fibers was less than 20% by mass or more than 80% by mass of the entire fiber constituting the nonwoven fabric for electromagnetic wave shielding material, and was out of the preferred range, the heat roll temperature was 205 Although it was a preferable range in degreeC, the peeling strength was low, and it became a nonwoven fabric for electromagnetic wave shielding materials with poor fiber-removal resistance.

Industrial applicability

The nonwoven fabric for electromagnetic wave shielding material and the electromagnetic wave shielding material of the present invention are preferably used for electronic devices, communication devices, telephone products, and the like. These devices and products include devices such as mobile phones, smart phones, mobile phones, personal computers, and mobile devices, cases for storing them, and telephone products such as televisions and washing machines. In particular, the electromagnetic shielding material of the present invention is preferably used by fixing a plastic housing, a flexible printed circuit board, an electric wire cable, a connector cable, or the like by bonding, pressing, fusion bonding, winding, or the like.

Claims (7)

In the nonwoven fabric for electromagnetic wave shielding material which is a wet nonwoven fabric, the wet nonwoven fabric is selected from stretched polyester short fibers having a fiber diameter of 3 µm or more and less than 12 µm, two or more oriented polyester short fibers having different fiber diameters, and a fiber diameter A nonwoven fabric for an electromagnetic wave shielding material, comprising as an essential component the unstretched polyester-based short fibers of 3 µm or more and 5 µm or less. In the nonwoven fabric for electromagnetic wave shielding material, which is a wet nonwoven fabric, it contains as an essential component a stretched polyester short fiber having a fiber diameter of less than 3 µm and an unstretched polyester short fiber having a fiber diameter of 3 µm or more and 5 µm or less, and has an apparent weight of 7 A nonwoven fabric for an electromagnetic wave shielding material, characterized in that it is g/m 2 or less and has a density of 0.5 to 0.8 g/cm 3. In the nonwoven fabric for electromagnetic wave shielding material which is a wet nonwoven fabric, it contains a stretched polyester short fiber and an unstretched polyester short fiber having a melting point of 220°C or more and 250°C or less, and the peel strength (vertical direction) of the nonwoven fabric is 2.0 N/m Nonwoven fabric for electromagnetic wave shielding material, characterized in that the above. An electromagnetic shielding material, characterized in that the nonwoven fabric for electromagnetic shielding materials according to any one of claims 1 to 3 is subjected to a metal coating treatment. The method of claim 4,
An electromagnetic shielding material, characterized in that the metal coating treatment is at least one treatment selected from the group consisting of an electroless metal plating treatment, an electroplating treatment, a metal vapor deposition treatment, and a sputtering treatment. The method of claim 4,
An electromagnetic shielding material, characterized in that the metal coating treatment includes, in this 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. The method according to any one of claims 4 to 6,
An electromagnetic shielding material having a thickness of the electromagnetic shielding material of 15 µm or less and a surface resistance of the electromagnetic shielding material of 0.03 Ω/□ or less.

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