Electromagnetic wave shielding molding film

Abstract

The object of the present invention is to provide a molded film for electromagnetic shielding that is excellent in electromagnetic shielding properties, moldability, and electromagnetic shielding properties after molding. The molded film for electromagnetic shielding has a conductive layer on at least one side of a base film, the conductive layer contains conductive particles A and a thermoplastic resin, the porosity of the conductive layer at a cut surface is 5% or more and 30% or less, and the aspect ratio of the conductive particles A is 5.0 or more and 20.0 or less.

Description

[Technical field]

[0001] The present invention relates to a molded film for electromagnetic wave shielding. [Background technology]

[0002] In recent years, with the expansion of the IoT society, there is an increasing demand for electromagnetic wave shielding performance in fields such as mobile phones, electrical appliances, and automobile parts. When using resin for the housing, a method of treating the molded product with plating, conductive paint, etc. is known. However, these conventional methods require environmental measures such as wastewater treatment and post-treatment of solvents, and various attempts have been made to improve this point.

[0003] For example, Patent Document 1 discloses a technique for an in-mold transfer molding film having a conductive layer made of metal or conductive polymer resin, and Patent Document 2 discloses a technique for in-mold transfer molding a molding film having a conductive layer containing resin and conductive fine particles. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2006-297642 A [Patent Document 2] Patent Publication No. 2021-192960 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the technology described in Patent Document 1 has limitations in terms of the shape of the object to be molded, since cracks or tears may occur in the conductive layer and the base film when the shape of the molded object is complex. On the other hand, the technology described in Patent Document 2 has a problem that, although the conductive layer can conform to the shape of a molded object with a complex shape, the electromagnetic wave shielding performance is inferior.

[0006] An object of the present invention is to overcome the problems of the conventional techniques and to provide a molded film for electromagnetic shielding which is excellent in electromagnetic shielding properties, moldability and electromagnetic shielding properties after molding. [Means for solving the problem]

[0007] As a result of intensive research aimed at solving the above problems, the inventors have found that the problems can be solved as follows, and have arrived at the present invention. That is, a preferred embodiment of the electromagnetic wave shielding molded film of the present invention has the following configuration. (1) A molded film for electromagnetic shielding, comprising a conductive layer on at least one side of a base film, the conductive layer containing conductive particles A and a thermoplastic resin, the conductive layer having a void ratio of 5% or more and 30% or less at a cut surface, and the conductive particles A having an aspect ratio of 5.0 or more and 20.0 or less. (2) The molded film for electromagnetic shielding according to (1), wherein the aspect ratio of the cross-sectional shape of the voids observed on a cut surface of the conductive layer is 1.0 or more and 20.0 or less. (3) The molded film for electromagnetic shielding according to (2), wherein the orientation angle of the voids is 0° or more and 45° or less. (4) The molded film for electromagnetic shielding according to any one of (1) to (3), wherein the conductive layer contains conductive particles B having an aspect ratio of 1.0 or more and 2.0 or less. (5) A molded film for electromagnetic shielding according to any one of (1) to (4), in which the area of ​​conductive particles in a cut surface of the conductive layer is 50% or more and 90% or less, and the area of ​​thermoplastic resin in a cut surface of the conductive layer is 5% or more and 45% or less. (6) The molded film for electromagnetic shielding according to any one of (1) to (5), wherein the orientation angle of the conductive particles A in the cut surface of the conductive layer is 3° or more and 45° or less. (7) The molded film for electromagnetic shielding according to any one of (1) to (6), wherein the conductive layer has a thickness of 5 μm or more and 15 μm or less. (8) The molded film for electromagnetic shielding according to any one of (1) to (7), wherein a release layer is located between the base film and the conductive layer. Effect of the Invention

[0008] According to the present invention, it is possible to provide an electromagnetic wave shielding molded film which is excellent in electromagnetic wave shielding properties, moldability, and electromagnetic wave shielding properties after molding. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 shows a schematic cross-sectional view of one embodiment of the electromagnetic wave shielding molded film of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The electromagnetic shielding molded film of the present invention has a conductive layer on at least one surface of a base film, the conductive layer containing conductive particles A and a thermoplastic resin, the porosity of the cut surface of the conductive layer being 5% or more and 30% or less, and the aspect ratio of the conductive particles A being 5 or more and 20 or less. By adopting such an embodiment, the electromagnetic shielding molded film of the present invention is excellent in electromagnetic shielding property, moldability, and electromagnetic shielding property after molding.

[0011] The electromagnetic wave shielding molded film of the present invention will be specifically described below. Here, Fig. 1 is as described above, and the electromagnetic wave shielding molded film 4 has a conductive layer 1, a release layer 2, and a base film 3 in this order.

[0012] (Conductive layer) The conductive layer in the present invention contains conductive particles A and a thermoplastic resin, and the void ratio in the cut surface of the conductive layer is 5% or more and 30% or less, and the aspect ratio of the conductive particles A is 5 or more and 20 or less. By adopting such a form, the electromagnetic wave shielding molding film has excellent electromagnetic wave shielding properties, moldability, and electromagnetic wave shielding properties after molding.

[0013] A preferred example of the conductive particle A in the present invention is a particle containing one or more selected from the group consisting of zero-valent carbon, silver, gold, copper, nickel, chromium, palladium, indium, aluminum, zinc, and platinum. By adopting such a form, the resistivity of the conductive layer is reduced, and the molded film for electromagnetic shielding has excellent electromagnetic shielding properties. From the same viewpoint as above, it is more preferable that the conductive particle A contains one or more selected from the group consisting of gold, silver, silver-plated copper powder, and an alloy of silver and copper. Note that "zero-valent" refers not only to the carbon at the beginning but also to all metal elements. Whether or not the conductive particle A contains a zero-valent metal element can be determined by whether or not a zero-valent metal element is detected in the particle portion by performing energy dispersive X-ray spectroscopy mapping analysis (hereinafter, EDX mapping analysis) on a cross section obtained by cutting the molded film for electromagnetic shielding. The EDX mapping analysis can be performed, for example, using a scanning electron microscope (FEI, XL30 SFEG) equipped with an energy dispersive X-ray spectrometer (EDAX, NEW XL30 132-2.5) under conditions of an acceleration voltage of 20 kV and a magnification of 20,000 times. In addition, the cutting means for the electromagnetic wave shielding molded film can be a "Cross Section Polisher" (registered trademark) SM-09010 (JEOL), etc., and when using this device, a sample is obtained by treating with argon gas at an acceleration voltage of 4 kV and a current value of 70 μA for 10 hours. In addition, the carbon particles refer to particles that have been qualitatively analyzed by performing a microscopic Raman mapping analysis on a cross section obtained by the same method as above. The microscopic Raman mapping analysis can be measured, for example, using a microscopic laser Raman spectrometer (HORIBA, LTD., "LabRAM" (registered trademark) HR Evolution).

[0014] The aspect ratio of the conductive particle A in the present invention is 5.0 or more and 20.0 or less. By making the aspect ratio of the conductive particle A 5.0 or more, the overlap between particles in the conductive layer after molding can be maintained, so that the electromagnetic wave shielding property after molding is excellent. From the same viewpoint as above, it is preferable to make it 7.0 or more. In addition, by making the aspect ratio of the conductive particle A 20.0 or less, the dispersibility of the particles in the conductive layer can be improved, so that the moldability as a molded film for electromagnetic wave shielding and the electromagnetic wave shielding property after molding are excellent. From the same viewpoint, it is preferable to make it 15.0 or less. The aspect ratio of the conductive particle A can be calculated by the average major axis / average minor axis of the conductive particle A. As a method for calculating the average major axis / average minor axis of the conductive particles A, for example, a scanning electron microscope (XL30 SFEG, manufactured by FEI) is used to observe the cross section of the conductive layer obtained by cutting the electromagnetic wave shielding molded film under conditions of an acceleration voltage of 20 kV and a magnification of 100,000 times, 50 particles are extracted from the obtained image, each is approximated to an ellipse, and the aspect ratio is calculated by taking the average value of the maximum length as the average major axis and the average value of the minimum length as the average minor axis. As a cutting means for the electromagnetic wave shielding molded film, for example, a manual rotary microtome ("HistoCore BIOCUT" (registered trademark) R, manufactured by Leica Microsystems Co., Ltd.) can be used to obtain a sample.

[0015] The orientation angle of the conductive particles A in the present invention is preferably 3° or more and 45° or less. By setting the orientation angle to 45° or less, the number of contacts between the conductive particles A in the conductive layer increases, and the resistance value of the conductive layer decreases, resulting in an excellent electromagnetic wave shielding property as a molded film for electromagnetic wave shielding. From the same viewpoint as above, the orientation angle is more preferably 33° or less. In addition, by setting the orientation angle to 3° or more, the contacts between the conductive particles A can be maintained when the conductive particles A enter the voids during molding in which the conductive layer is stretched, resulting in an excellent electromagnetic wave shielding property after molding as a molded film for electromagnetic wave shielding. From the same viewpoint as above, the orientation angle is more preferably 5° or more. The orientation angle of the conductive particles A can be reduced by increasing the area and aspect ratio of the conductive particles A in the conductive layer. On the other hand, the orientation angle of the conductive particles A can be reduced by increasing the porosity in the conductive layer. The orientation angle of the conductive particles A in the present invention refers to the average angle of the length direction of the conductive layer with respect to the length direction of the conductive particles A on the cut surface of the conductive layer. An orientation angle of 0° is parallel to the length direction of the conductive layer, and an orientation angle of 90° is perpendicular to the length direction of the conductive layer.

[0016] The thermoplastic resin in the present invention is preferably a polyester resin, a polyurethane resin, a (meth)acrylic resin, a polyolefin resin, an ethylene-vinyl acetate copolymer resin, a polyamide resin, a chloroprene resin, an aramid resin, an acrylic urethane copolymer resin, or a polyester urethane copolymer resin, used alone or in combination. By adopting such a form, the dispersibility of the conductive particles A and the conductive particles B described later in the conductive layer, and the moldability and flexibility of the entire conductive layer can be improved, and the molded film for electromagnetic wave shielding has excellent electromagnetic wave shielding properties, moldability, and electromagnetic wave shielding properties after molding. From the same viewpoint as above, it is more preferable to use a polyester resin, a polyurethane resin, or a polyester urethane copolymer resin.

[0017] The qualitative and quantitative analysis method of the thermoplastic resin in the present invention may, for example, be a method in which only the conductive layer is scraped off from a molded film for electromagnetic shielding, the obtained sample of the conductive layer is freeze-dried, and the recovered dried material is subjected to qualitative and quantitative analysis using gas chromatography mass spectrometry (P&T-GC / MS) equipped with a purge and trap sampler (thermal desorption device).

[0018] The porosity of the cut surface of the conductive layer in the present invention is 5% or more and 30% or less. By making the porosity 5% or more, gaps into which the conductive particles can enter can be secured during molding in which the conductive layer is stretched, and the occurrence of cracks in the conductive layer can be suppressed, so that the molded film for electromagnetic shielding has excellent moldability and electromagnetic shielding properties after molding. From the same viewpoint as above, it is preferable that the porosity is 7% or more. Furthermore, by making the porosity 30% or less, the overlap of the conductive particles before molding can be guaranteed, so that the molded film for electromagnetic shielding has excellent electromagnetic shielding properties. From the same viewpoint as above, it is preferable that the porosity is 15% or less.

[0019] In the present invention, the porosity can be set to 5% or more and 30% or less, for example, by mixing a dilution organic solvent having a relative evaporation rate 5 times faster than that of the mixing organic solvent used in the conductive layer coating composition when laminating the conductive layer on the substrate film. By using this method, when the conductive layer coating composition is applied to the substrate film and then heat treated, voids can be formed in the conductive layer due to the difference in the relative evaporation rates of the mixing organic solvent and the dilution organic solvent. The relative evaporation rate based on n-butyl acetate can be determined by the evaporation rate measured in accordance with ASTM D3539-87 (2004). Specifically, it is a value defined as the relative value of the evaporation rate based on the time required for n-butyl acetate to evaporate 90% by mass under dry air.

[0020] As the above-mentioned organic solvent for mixing, for example, ethylene glycol monoethyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, butyl carbitol, hexyl carbitol, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, ethylene glycol mono-n-propyl ether, diacetone alcohol, tetrahydrofurfuryl alcohol, propylene glycol monomethyl ether acetate is preferably used alone or in combination. By using such an organic solvent, the solubility with the thermoplastic resin and the processability when mixing the conductive resin and the thermoplastic resin are excellent. Furthermore, since the relative evaporation rate is slow, voids can be formed when the conductive layer coating material composition is subjected to a heat treatment.

[0021] In addition, as the dilution organic solvent, for example, ethyl methyl ketone, methyl isobutyl ketone, butyl acetate, ethyl acetate, methanol, isopropanol, cyclohexanone, toluene, are preferably used alone or in combination.By using such a solvent, the viscosity of the conductive layer coating composition can be reduced, and the conductive layer coating composition has excellent coating properties when applied to a substrate film.Furthermore, the relative evaporation rate is faster, so that the productivity of the molding film for electromagnetic wave shielding is excellent.

[0022] The aspect ratio of the cross-sectional shape of the void observed on the cut surface of the conductive layer in the present invention is preferably 1.0 or more and 20.0 or less. By making the aspect ratio of the cross-sectional shape of the void 1.0 or more, the gap into which the conductive particles enter during molding in which the conductive layer is stretched can be secured, and the occurrence of cracks in the conductive layer can be suppressed, so that the molded film for electromagnetic shielding has excellent moldability and electromagnetic shielding properties after molding. From the same viewpoint as above, it is more preferable that the aspect ratio of the cross-sectional shape of the void is 3.0 or more. In addition, by making the aspect ratio of the cross-sectional shape of the void 20.0 or less, the overlap of the conductive particles before molding can be guaranteed, so that the molded film for electromagnetic shielding has excellent electromagnetic shielding properties. From the same viewpoint as above, it is more preferable that the aspect ratio of the cross-sectional shape of the void is 15.0 or less. The aspect ratio of the cross-sectional shape of the void can be improved by increasing the area of ​​the conductive particles in the conductive layer and the aspect ratio of the conductive particles. On the other hand, by increasing the porosity in the conductive layer, the aspect ratio of the cross-sectional shape of the voids can be reduced. The aspect ratio of the cross-sectional shape of the voids in the present invention can be calculated by the average major axis / average minor axis of the voids. The average major axis / average minor axis of the voids can be calculated in the same manner as in the conductive particle A.

[0023] The orientation angle of the voids in the present invention is preferably 0° or more and 45° or less. By setting the orientation angle of the voids to 45° or less, the number of contacts between the conductive particles A in the conductive layer increases, and the resistance value of the conductive layer decreases, resulting in an excellent electromagnetic shielding property as a molded film for electromagnetic shielding. From the same viewpoint as above, it is more preferable to set the orientation angle of the voids to 33° or less. In addition, by setting the orientation angle of the voids to 0° or more, the contacts between the conductive particles A can be maintained when the conductive particles A enter the voids during molding in which the conductive layer is stretched, so that the molded film for electromagnetic shielding has excellent electromagnetic shielding property after molding. From the same viewpoint as above, it is more preferable to set the orientation angle of the voids to 5° or more. The orientation angle of the voids can be reduced by increasing the area and aspect ratio of the conductive particles in the conductive layer. On the other hand, the orientation angle of the voids can be reduced by improving the porosity in the conductive layer. The orientation angle of the voids in the present invention refers to the average angle of the length direction of the conductive layer with respect to the length direction of the voids in the cut surface of the conductive layer. When the orientation angle of the voids is 0°, they are parallel to the length direction of the conductive layer, and when the orientation angle of the voids is 90°, they are perpendicular to the length direction of the conductive layer.

[0024] A method for measuring the porosity of the conductive layer can be, for example, to cut the electromagnetic shielding molded film perpendicular to the thickness using a manual rotary microtome (Leica Microsystems, HistoCore BIOCUT (registered trademark) R) to obtain a cross-section of the electromagnetic shielding molded film, and then to observe the cross-section of the conductive layer using a scanning electron microscope (FEI, XL30 SFEG) at an acceleration voltage of 20 kV and an observation magnification of 1,000 times.The area of ​​the void parts is calculated by subtracting the non-perforated parts from the cross-sectional photograph, and the porosity can be calculated as the area ratio of the void parts to the total area.

[0025] The conductive layer in the present invention preferably contains conductive particles B having an aspect ratio of 1.0 or more and 2.0 or less. By containing conductive particles B having an aspect ratio of 1.0 or more and 2.0 or less in addition to conductive particles A in the conductive layer, the conductive particles in the conductive layer are closely packed, and when the conductive particles enter the voids during molding in which the conductive layer is stretched, the contact points between the conductive particles A and B can be maintained, so that the overlap between the particles in the conductive layer before and after molding can be maintained, and the electromagnetic shielding property and the electromagnetic shielding property after molding as a molded film for electromagnetic shielding are further improved. The aspect ratio of the conductive particles B in the present invention can be calculated in the same manner as that of the conductive particles A. The conductive particles B in the present invention are preferably exemplified by particles containing one or more selected from the group consisting of zero-valent carbon, silver, gold, copper, nickel, chromium, palladium, indium, aluminum, zinc, and platinum. By adopting such a form, the resistivity of the conductive layer is lowered, and therefore the molded film for electromagnetic shielding has excellent electromagnetic shielding property. From the same viewpoint as above, it is more preferable that the conductive particles B contain at least one type selected from the group consisting of gold, silver, silver-plated copper powder, and an alloy of silver and copper.

[0026] The area of ​​the conductive particles in the cut surface of the conductive layer in the present invention is preferably 50% or more and 90% or less, and the area of ​​the thermoplastic resin in the cut surface of the conductive layer is preferably 5% or more and 45% or less. The conductive particles referred to here refer to the conductive particles A in the present invention and the conductive particles B in the present invention. By making the area of ​​the conductive particles 50% or more, the component ratio of the conductive particles in the conductive layer can be increased, so that the molded film for electromagnetic shielding has excellent electromagnetic shielding properties and excellent electromagnetic shielding properties after molding. From the same viewpoint, it is more preferable to make it 75% or more. Furthermore, by making the area of ​​the conductive particles 90% or less, the component ratio of the resin in the conductive layer can be increased, so that the molded film for electromagnetic shielding has excellent moldability. From the same viewpoint, it is more preferable to make it 85% or less. From the same viewpoint as above, by making the area of ​​the thermoplastic resin 45% or less, the component ratio of the conductive particles to the total components constituting the conductive layer can be increased, so that the molded film for electromagnetic shielding has excellent electromagnetic shielding properties and excellent electromagnetic shielding properties after molding. From the same viewpoint as above, it is more preferable to make it 25% or less. In addition, by making the area of ​​the thermoplastic resin 5% or more, the dispersibility of the conductive particles in the conductive layer and the moldability and flexibility of the entire conductive layer can be improved, resulting in a molded film with excellent moldability for electromagnetic wave shielding. From the same viewpoint as above, it is more preferable to make it 7% or more. Here, the area of ​​the conductive particles on the cut surface of the conductive layer means the ratio of the total area of ​​the conductive particles reflected in the observation image to the total area of ​​the observation image of the cut surface of the conductive layer. In addition, the area of ​​the thermoplastic resin on the cut surface of the conductive layer means the ratio of the total area of ​​the thermoplastic resin part reflected in the observation image to the total area of ​​the observation image of the cut surface of the conductive layer.

[0027] The thickness of the conductive layer in the present invention is preferably 5 μm or more and 15 μm or less. By having a thickness of the conductive layer of 15 μm or less, the conductive layer is stably heated in the molding process, and the in-plane variation of the conductive layer can be reduced, so that the molded film for electromagnetic shielding has excellent electromagnetic shielding properties after molding. From the same viewpoint, it is more preferable that the thickness of the conductive layer is 12 μm or less. In addition, by having a thickness of the conductive layer of 5 μm or more, the content of particles in the conductive layer increases and the resistivity of the conductive layer decreases, so that the conductivity and electromagnetic shielding properties can be fully exhibited, and the molded film for electromagnetic shielding has excellent electromagnetic shielding properties and electromagnetic shielding properties after molding. From the same viewpoint, it is more preferable that the thickness of the conductive layer is 7 μm or more.

[0028] As a method for qualitatively and quantitatively analyzing thermoplastic resins, for example, the conductive layer alone can be scraped off from an electromagnetic wave shielding molded film, the obtained sample of the conductive layer is freeze-dried, and the recovered dried material can be qualitatively and quantitatively analyzed using gas chromatography mass spectrometry (P&T-GC / MS) equipped with a purge and trap sampler (thermal desorption device).

[0029] (Base film) The substrate film in the present invention is preferably composed of at least one selected from the group consisting of polyester resins (e.g., polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, etc.), polymethyl methacrylate resins, acrylic resins, polycarbonate resins, polyethylene resins, polypropylene resins, polystyrene resins, fluororesins, triacetyl cellulose resins, polyvinyl alcohol resins, polyvinyl chloride resins, polyvinylidene chloride resins, ethylene-vinyl acetate copolymer resins, polyvinyl butyral resins, metal ion cross-linked ethylene-methacrylic acid copolymer resins, polyurethane resins, and cyclic olefin resins, from the viewpoints of good dimensional stability and durability, improved productivity, and excellent processability in lamination and molding of the release layer and conductive layer. From the same viewpoints as above, polyester resins are preferably used, and polybutylene terephthalate is particularly preferably used.

[0030] (Release layer) The electromagnetic wave shielding molded film of the present invention is preferably used in an embodiment that includes a step of placing the film in a mold, such as in-mold molding, and then injecting a resin and / or a resin precursor. Therefore, it is preferable that a release layer is located between the base film and the conductive layer in the present invention.

[0031] The release layer in the present invention is not particularly limited as long as it does not impair the effects of the present invention, and preferred examples include alkyd resins, polyolefin resins, long-chain alkyl group-containing resins, fluorine resins, silicone resins, organic and silicone mixed or copolymer resins, etc. Among these, silicone resins are preferred from the viewpoint of easily adjusting the release properties.

[0032] The method for laminating the release layer onto the base film is not particularly limited as long as it does not impair the effects of the present invention. However, it is preferable to form the release layer by coating using a dip coating method, roller coating method, wire bar coating method, gravure coating method or die coating method (U.S. Pat. No. 2,681,294 specification), etc., and from the viewpoint of processability, the gravure coating method or die coating method is more preferable. EXAMPLES

[0033] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0034] The measurement and evaluation methods used in the present examples are as follows.

[0035] (1) Thickness of the conductive layer The thickness (μm) of the conductive layer was obtained by cutting the electromagnetic shielding molded film in a direction perpendicular to the thickness using a manual rotary microtome (Leica Microsystems, "HistoCore BIOCUT" (registered trademark) R) to obtain a cross section of the electromagnetic shielding molded film. Next, the cross section of the conductive layer of the cross section of the electromagnetic shielding molded film was observed using a scanning electron microscope (FEI, XL30 SFEG) at an accelerating voltage of 20 kV and an observation magnification of 100,000 times, and the thickness (μm) of the conductive layer was obtained by calculating the average value of the values ​​obtained by measuring any five points on the cross section photograph.

[0036] (2) Aspect ratio of the cross-sectional shape of conductive particle A, conductive particle B, and void In the method (1), 50 conductive particles and voids were extracted from the obtained scanning electron microscope image, and each was approximated to an ellipse, and the aspect ratios of the cross-sectional shapes of conductive particle A, conductive particle B, and voids were calculated by taking the average value of the maximum length as the average major axis and the average value of the minimum length as the average minor axis. Next, a histogram was created in increments of 0.1 using the obtained aspect ratios for conductive particle A and conductive particle B, and the peak value was calculated as the aspect ratio of conductive particle A. When there were two peaks, the peak with the smaller value was taken as the aspect ratio of conductive particle B, and the peak with the larger value was taken as the aspect ratio of conductive particle A.

[0037] (3) Orientation angle of conductive particles A and voids In the method (1), 20 conductive particles A and 20 voids were extracted from the obtained scanning electron microscope image, and the orientation angle of each of them in the length direction of the conductive layer relative to the length direction of the conductive particles A and the voids was calculated. Next, a histogram was created in 1° increments using the obtained orientation angles, and the peak values ​​were calculated as the orientation angles of the conductive particles A and the voids.

[0038] (4) Porosity and area of ​​conductive particles A, conductive particles B, and thermoplastic resin In the method (1), the image was cut out from the obtained scanning electron microscope image so that the conductive particles A, the conductive particles B, and the thermoplastic resin remained, and the image was analyzed using "HALCON" (registered trademark) Ver. 10.0 manufactured by MVTec Corporation to calculate the void area, and the ratio of the total area of ​​the void area to the area of ​​the entire image was calculated as the porosity. The areas of the conductive particles A, the conductive particles B, and the thermoplastic resin were also calculated in the same manner as the porosity.

[0039] (5) Electromagnetic wave shielding effect of molded films for electromagnetic wave shielding The molded film for electromagnetic shielding was cut into a size of 120 mm x 120 mm, and measurements were performed using the KEC method (electric field), and the electromagnetic shielding effect (dB) at a frequency of 300 MHz was calculated using a spectrum analyzer. The results obtained show that the higher the electromagnetic shielding effect of the molded film for electromagnetic shielding, the better the electromagnetic shielding properties.

[0040] (6) Electromagnetic wave shielding effect of a molded film for electromagnetic wave shielding when stretched 1.6 times vertically and 1.6 times horizontally The molded film for electromagnetic shielding was cut to 120mm x 120mm, and the molded film for electromagnetic shielding was subjected to simultaneous biaxial stretching processing at 1.6 times length x 1.6 times width using a Bruckner KARO5.0 lab stretcher to obtain a sample, which was then measured using the KEC method (electric field) and the electromagnetic shielding effect (dB) at a frequency of 1GHz was measured using a spectrum analyzer, and the obtained result was taken as the electromagnetic shielding effect at a frequency of 1GHz. The higher the electromagnetic shielding effect, the better the electromagnetic shielding properties.

[0041] (7) Formability of Electromagnetic Wave Shielding Film In the method of (6), the sample was subjected to simultaneous biaxial stretching at a magnification of 1.6 times vertically and 1.6 times horizontally, and the sample after the simultaneous biaxial stretching was visually observed and evaluated according to the following criteria. A: The conductive layer is uniformly stretched over the base film, showing good results. B: The conductive layer is stretched relative to the base film, but cracks are observed in some parts of the conductive layer. No problems in practical use. C: Cracks are observed throughout the conductive layer. Not suitable for practical use.

[0042] The materials used are as follows:

[0043] (conductive particles a) Silver particles (Fukuda Metal Foil & Powder Co., Ltd., AgC-2011, average particle size 2.6 μm, flake shape).

[0044] (Conductive particles b) Silver particles (Fukuda Metal Foil & Powder Co., Ltd., AgC-B, average particle size 4.0 μm, flake shape).

[0045] (conductive particles c) Silver particles (Fukuda Metal Foil & Powder Co., Ltd., AgG-204B, average particle size 7.2 μm, flake shape).

[0046] (conductive particles d) Silver particles (DOWA Electronics Co., Ltd., AG-2-1C, average particle size 0.8 μm, spherical).

[0047] (conductive particles e) Silver particles (Fukuda Metal Foil and Powder Co., Ltd., AgC-222, average particle size 5.0 μm, kidney-shaped).

[0048] (conductive particles f) Silver particles (Fukuda Metal Foil & Powder Co., Ltd., Ag-XF, average particle size 5.0 μm, flake shape).

[0049] (conductive particles g) Silver particles (Fukuda Metal Foil and Powder Co., Ltd., AgC-251, average particle size 3.0 μm, kidney-shaped).

[0050] (conductive particles h) Silver particles (Fukuda Metal Foil & Powder Co., Ltd., AgC-156, average particle size 1.5 μm, spherical).

[0051] (thermoplastic resin) Urethane modified polyester resin (manufactured by Toyobo Co., Ltd., "Vylon" (registered trademark) UR-4800, glass transition temperature 106°C, weight average molecular weight 25,000).

[0052] (Organic solvent a) Diethylene glycol monoethyl ether acetate (relative evaporation rate 0.2).

[0053] (Organic solvent b) Ethyl methyl ketone (relative evaporation rate 3.7).

[0054] [Example 1] <Production of molding film for electromagnetic wave shielding> The conductive layer coating composition for obtaining a conductive layer had the composition shown in Table 1, and was dispersed or dissolved in diethylene glycol monoethyl ether acetate as an organic solvent for mixing, and then kneaded using a three-roll mill. Next, ethyl methyl ketone was mixed and dispersed as an organic solvent for dilution using a Homodisper (manufactured by Primix Corporation), thereby obtaining a conductive layer coating composition with a solid content of 30.0 mass %.

[0055] A 50 μm thick polybutylene terephthalate film (ESRM manufactured by Okura Industrial Co., Ltd.) was used as the substrate film, and an alkyd modified silicone resin (X-62-900B manufactured by Shin-Etsu Chemical Co., Ltd.) was dissolved in methyl ethyl ketone and mixed and dispersed using a Homo Disper (manufactured by Primix Corporation) to form a coating composition, which was then applied by gravure coating. After drying at 120°C, a release layer laminated substrate film having a release layer with a thickness of 0.05 μm was obtained.

[0056] The conductive layer coating composition was applied to the release layer-laminated substrate film by gravure coating, dried at 120°C, and cured to laminate a conductive layer having a thickness of 10 μm, thereby obtaining a molded film for electromagnetic wave shielding, which was then wound into a roll.

[0057] [Examples 2 to 10, Comparative Examples 1 to 4] An electromagnetic wave shielding molded film was produced in the same manner as in Example 1, except that the conductive particles, the organic solvent for mixing, and the organic solvent for dilution were as shown in Tables 1 to 3.

[0058] The electromagnetic wave shielding molded films of Examples 1 to 10 all had excellent electromagnetic wave shielding properties, moldability, and electromagnetic wave shielding properties after molding as electromagnetic wave shielding films.

[0059] On the other hand, the electromagnetic shielding molded films of Comparative Examples 1 and 4 were inferior in moldability and in electromagnetic shielding properties after molding to the electromagnetic shielding molded films of the Examples.

[0060] Furthermore, the electromagnetic shielding molded film of Comparative Example 2 was inferior to the electromagnetic shielding molded films of Examples in terms of electromagnetic shielding properties and electromagnetic shielding properties after molding.

[0061] Furthermore, the electromagnetic wave shielding molded film of Comparative Example 3 was inferior in electromagnetic wave shielding properties after molding to the electromagnetic wave shielding molded films of the Examples.

[0062] [Table 1]

[0063] [Table 2]

[0064] [Table 3] [Explanation of symbols]

[0065] 1: Conductive layer 2; Release layer 3: Base film 4: Molded film for electromagnetic wave shielding

Claims

1. A conductive layer is provided on at least one surface of the base film, The conductive layer contains conductive particles A and a thermoplastic resin, The porosity of the cut surface of the conductive layer is 5% or more and 30% or less, the aspect ratio of the cross-sectional shape of the void observed on a cut surface of the conductive layer is 1.0 or more and 20.0 or less; The aspect ratio of the conductive particles A is 5.0 or more and 20.0 or less. Molded film for electromagnetic wave shielding.

2. 2. The electromagnetic wave shielding molded film according to claim 1, wherein the orientation angle of the voids is from 0° to 45°.

3. 2. The electromagnetic wave shielding molded film according to claim 1, wherein the conductive layer contains conductive particles B having an aspect ratio of 1.0 or more and 2.0 or less.

4. 2. The molded film for electromagnetic shielding according to claim 1, wherein an area of ​​conductive particles in a cut surface of the conductive layer is 50% or more and 90% or less, and an area of ​​thermoplastic resin in a cut surface of the conductive layer is 5% or more and 45% or less.

5. 2. The electromagnetic wave shielding molded film according to claim 1, wherein the conductive particles A have an orientation angle of 3° or more and 45° or less in a cut surface of the conductive layer.

6. 2. The electromagnetic wave shielding molded film according to claim 1, wherein the conductive layer has a thickness of 5 μm or more and 15 μm or less.

7. The electromagnetic wave shielding molded film according to claim 1 , wherein a release layer is located between the base film and the conductive layer.

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