Conductive film manufacturing method and conductive film

Abstract

To provide a method for manufacturing a conductive film and the like capable of suppressing an increase in electric resistance of the conductive film.SOLUTION: A method for manufacturing a conductive film comprises steps of: extruding a conductive composition in which a metal filler is blended in a thermoplastic resin, from a die; and cooling the conductive composition by a cast roll. In the conductive composition, a linear pressure applied from an opposite side of the cast roll toward a cast roll side is 10 N / mm or less.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for producing a conductive film, and a conductive film. [Background technology]

[0002] JP 2014-91248 A (Patent Document 1) discloses a method for producing a conductive film. In this method, a conductive composition extruded from a T-die is sandwiched between a cooling roll and a rubber roll. The conductive composition is sent backward by the cooling roll and the rubber roll to produce a conductive film (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2014-91248 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the above Patent Document 1, the present inventor(s) discovered that when the pressure applied by the rubber roll to the cooling roll is large, the electrical resistance value of the conductive film increases.

[0005] The present invention has been made to solve such problems, and its object is to provide a method for producing a conductive film that can suppress an increase in the electrical resistance value of the conductive film. [Means for solving the problem]

[0006] A method for producing a conductive film according to an aspect of the present invention includes the steps of extruding a conductive composition, which is a thermoplastic resin blended with a metal filler, from a die and cooling the conductive composition with a casting roll. A linear pressure applied to the conductive composition from the opposite side of the casting roll toward the casting roll is 10 N / mm or less.

[0007] In this method for producing a conductive film, the linear pressure applied to the conductive composition cooled by the cast roll is 10 N / mm or less. Therefore, according to this method for producing a conductive film, the linear pressure applied to the conductive composition is low, and the metal filler present near the surface of the conductive composition is unlikely to penetrate deep into the conductive composition, so that an increase in the electrical resistance value of the conductive film can be suppressed.

[0008] In the above-mentioned method for producing a conductive film, in the step of cooling the conductive composition by the casting roll, the conductive composition may be sandwiched between the casting roll and a touch roll, and the touch roll may apply pressure to the casting roll.

[0009] In the method for producing a conductive film, a linear pressure applied to the conductive composition from the opposite side to the casting roll toward the casting roll may be 4 N / mm or less.

[0010] A conductive film according to another aspect of the present invention includes a thermoplastic resin and a metal filler, and in an analysis using a scanning electron microscope / energy dispersive X-ray spectroscopy (SEM-EDX), the ratio of the content of the metal filler detected when the tilt angle of an observation sample stage on which a test piece of the conductive film is placed is 0° to the content of the metal filler detected when the tilt angle is 40° is 0.7 or more.

[0011] In the analysis using SEM-EDX, when the tilt angle of the observation sample stage is 0°, the detection range is up to a relatively deep position of the test piece. On the other hand, when the tilt angle of the observation sample stage is 40°, the detection range is up to a relatively shallow position of the test piece. Therefore, the larger the ratio of the content of the metal filler detected when the tilt angle is 40° to the content of the metal filler detected when the tilt angle is 0°, the larger the amount of metal filler located near the surface of the test piece. In this conductive film, the ratio of the content of the metal filler detected when the tilt angle of the observation sample stage is 40° to the content of the metal filler detected when the tilt angle of the observation sample stage is 0° is 0.7 or more. Therefore, according to this conductive film, since the amount of metal filler located near the surface is relatively large, a relatively low electrical resistance value can be realized. Effect of the Invention

[0012] According to the present invention, it is possible to provide a method for producing a conductive film that can suppress an increase in the electrical resistance value of the conductive film. [Brief description of the drawings]

[0013] [Figure 1] FIG. 2 is a diagram illustrating a manufacturing apparatus for a conductive film. [Diagram 2] FIG. 1 is a diagram showing a schematic diagram of SEM-EDX when the tilt angle of the observation sample stage is 0°. [Diagram 3] FIG. 1 is a diagram showing a schematic diagram of SEM-EDX when the tilt angle of the observation sample stage is 40°. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the drawings, the same or corresponding parts are designated by the same reference characters and their description will not be repeated.

[0015] [1. Manufacturing equipment configuration] 1 is a schematic diagram of a manufacturing apparatus 10 for a conductive film C2 according to the present embodiment. As shown in FIG. 1, the manufacturing apparatus 10 includes a T-die 100, a casting roll 200, a touch roll 300, a control device 350, and a take-up roll 390.

[0016] The T-die 100 is configured to melt and extrude the conductive composition C1. The conductive composition C1 contains a thermoplastic resin material and a metal filler. In the manufacturing apparatus 10, a conductive film C2 is manufactured based on the conductive composition C1. The conductive film C2 is used, for example, as a charging film or a discharging film for a copier or a printer, or as various functional films for other electric and electronic devices and parts. The conductive film C2 may or may not be subjected to surface treatment such as corona, plasma, coating, or sputtering. Any material may be used as the thermoplastic resin material as long as it is a resin material having thermoplasticity.

[0017] As the thermoplastic resin material, for example, polyolefin resins (homopolymers and copolymers) such as polypropylene (PP) or polyethylene (PE) may be used. In addition, as the thermoplastic resin, for example, fluorine-based copolymers such as tetrafluoroethylene-perfluoroalkylvinylether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), ethylene-tetrafluoroethylene copolymer (ETFE), or tetrafluoroethylene-hexafluoropropylene-perfluoroalkylvinylether copolymer (EPE), polyester-based copolymers such as polyether ester, or polyamide-based copolymers such as polyether amide or polyether ester amide may be used. In addition, as the thermoplastic resin material, for example, polymer alloys or polymer blends of the above may be used.

[0018] Examples of the metal filler include platinum, gold, silver, copper, nickel, titanium, and mixtures thereof. That is, the metal filler contained in the conductive composition C1 includes at least one metal selected from the group including platinum, gold, silver, copper, nickel, and titanium. Among these, nickel particles are more preferable as the metal filler.

[0019] The casting roll 200 is configured to cool the conductive composition C1 extruded by the T die 100 and send it downstream. The touch roll 300 is configured to press the conductive composition C1 extruded by the T die 100 toward the casting roll 200 and send it downstream. That is, the conductive composition C1 is sandwiched between the casting roll 200 and the touch roll 300. The winding roll 390 is configured to wind up the conductive film C2 produced by being cooled by the casting roll 200.

[0020] The control device 350 includes a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), etc., and is configured to control each component of the manufacturing apparatus 10 in response to information processing. The control device 350 controls, for example, the pressure applied by the touch roll 300 to the cast roll 200. The touch roll 300 is connected, for example, to an air cylinder (not shown). The control device 350 controls the pressure applied by the touch roll 300 to the cast roll 200 by controlling the pressure of this air cylinder.

[0021] In the manufacturing apparatus 10, the conductive composition C1 is pressed against the cast roll 200 by the touch roll 300 to increase the flatness of the conductive film C2. As a method for pressing the conductive composition C1 against the cast roll 200, for example, an air knife or electrostatic pinning method can be considered. However, since the conductive composition C1 contains a large amount of metal filler, the melt viscosity is likely to be high and it is difficult to be charged. Therefore, the conductive composition C1 cannot be sufficiently pressed against the cast roll 200 by the air knife or electrostatic pinning. Therefore, in the manufacturing apparatus 10, the conductive composition C1 is pressed against the cast roll 200 by the touch roll 300.

[0022] The present inventor(s) discovered that, in such a manufacturing apparatus 10, the electrical resistance value of the manufactured conductive film C2 increases as the pressure applied by the touch roll 300 toward the casting roll 200 increases. This is thought to be because, as the pressure applied by the touch roll 300 toward the casting roll 200 increases, the amount of metal filler located near the surface of the conductive film C2 decreases and the amount of metal filler located deep inside the conductive film C2 increases.

[0023] Therefore, in the manufacturing apparatus 10, the linear pressure applied by the touch roll 300 to the casting roll 200 side is 10 N / mm or less. Preferably, the linear pressure applied by the touch roll 300 to the casting roll 200 side is 4 N / mm or less.

[0024] Therefore, according to the manufacturing apparatus 10, the line pressure applied to the conductive composition C1 is low, and the metal filler present near the surface of the conductive composition C1 is less likely to penetrate into the deep parts of the conductive composition C1, thereby suppressing an increase in the electrical resistance value of the conductive film C2.

[0025] [2. Distribution of metal filler in the thickness direction of conductive film] As described above, in the conductive film C2 manufactured by the manufacturing apparatus 10, a sufficient amount of metal filler is located near the surface of the conductive film C2. In the conductive film C2, the degree to which the metal filler is located on the surface is indicated by an index calculated using SEM-EDX (Scanning Electron Microscope / Energy Dispersive X-ray Spectroscopy). The index will be described below.

[0026] FIG. 2 is a diagram schematically showing the SEM-EDX 20 when the tilt angle of the observation specimen stage 400 is 0°. FIG. 3 is a diagram schematically showing the SEM-EDX 20 when the tilt angle of the observation specimen stage 400 is 40°.

[0027] Referring to FIGS. 2 and 3, a test piece of the conductive film C2 is placed on the observation specimen stage 400. The test piece on the observation specimen stage 400 is irradiated with an electron beam, and the detector 500 detects the characteristic X-rays emitted from the test piece. Based on the detection result of the detector 500, the content rate of the metal filler in the test piece is calculated.

[0028] The electron beam irradiated on the test piece penetrates, for example, to a depth of X1 μm from the surface of the test piece. When the tilt angle of the observation specimen stage 400 is 0°, the detector 500 detects the characteristic X-rays emitted from the range from the surface of the test piece to a depth of X1 μm in the vertical direction. On the other hand, when the tilt angle of the observation specimen stage 400 is 40°, since the electron beam enters the test piece from an oblique direction, even if the penetration amount of the electron beam is the same, the penetration amount in the vertical direction from the surface of the test piece becomes shorter. For example, when the tilt angle of the observation specimen stage 400 is 40°, the detector 500 detects the characteristic X-rays emitted from the range from the surface of the test piece to a depth of X2 μm (<X1 μm) in the vertical direction.

[0029] In this way, when the tilt angle of the observation specimen stage 400 is 0°, metal filler present at a deeper position in the test piece is detected than when the tilt angle of the observation specimen stage 400 is 40°. Therefore, when metal filler is present in a large amount at a deep position in the test piece, the content of metal filler is higher when the tilt angle of the observation specimen stage 400 is 0° compared to when the tilt angle of the observation specimen stage 400 is 40°.

[0030] For example, the higher the ratio (B1 / A1) of the metal filler content (B1%) detected when the observation specimen stage 400 is tilted at an angle of 40° to the metal filler content (A1%) detected when the observation specimen stage 400 is tilted at an angle of 0°, the more metal filler is present in the conductive film C2 near the surface of the conductive film C2. One reason for this tendency is that when the observation specimen stage 400 is tilted at an angle of 0°, parts that cannot be detected due to the unevenness of the test piece surface (for example, the side of the undulations) become detectable.

[0031] In the conductive film C2 manufactured by the manufacturing apparatus 10, this ratio (B1 / A1) is 0.7 or more. Therefore, according to the conductive film C2, the amount of metal filler located near the surface is relatively large, and therefore a relatively low electrical resistance value can be achieved.

[0032] [3. Features] As described above, in the manufacturing method of the conductive film C2 according to the present embodiment, the linear pressure applied to the conductive composition C1 cooled by the casting roll 200 is 10 N / mm or less. Therefore, according to this manufacturing method, the linear pressure applied to the conductive composition C1 is low, and the metal filler present near the surface of the conductive composition C1 is unlikely to penetrate deep into the conductive composition C1, so that an increase in the electrical resistance value of the conductive film C2 can be suppressed.

[0033] In the conductive film C2 according to the present embodiment, in an analysis using SEM-EDX, the ratio (B1 / A1) of the metal filler content (B1%) detected when the tilt angle of the observation specimen stage 400 is 40° to the metal filler content (A1%) detected when the tilt angle of the observation specimen stage 400 is 0° is 0.7 or more. Therefore, according to the conductive film C2, the amount of metal filler located near the surface is relatively large, and therefore a relatively low electrical resistance value can be achieved.

[0034] [4. Modifications] Although the embodiment has been described above, the present invention is not limited to the above embodiment, and various modifications are possible without departing from the spirit of the present invention.

[0035] In the above embodiment, the conductive composition C1 is urged toward the casting roll 200 by the touch roll 300. However, the conductive composition C1 does not necessarily have to be urged toward the casting roll 200 by the touch roll 300. For example, the conductive composition C1 does not have to be urged toward the casting roll 200 at all. It is sufficient that the linear pressure applied to the conductive composition C1 from the opposite side of the casting roll 200 toward the casting roll 200 side is 10 N / mm or less.

[0036] 5. Working Examples <5-1. Examples and Comparative Examples> The conductive films of Examples 1 to 3 and the comparative example were produced by using a production apparatus 10 shown in Fig. 1. The conductive films of Examples 1 to 3 and the comparative example will be described below.

[0037] The conductive composition used in the production of the conductive film of Example 1 contained 30 wt% polypropylene (PP) and 70 wt% nickel (Ni). The linear pressure of the touch roll against the cast roll during the production of the conductive film of Example 1 was 2.7 N / mm. The thickness of the conductive film of Example 1 was 50 μm. The drawing speed of the winding roll during the production of the conductive film of Example 1 was 2.5 m / min.

[0038] The conductive composition used in the production of the conductive film of Example 2 contained 30 wt% polypropylene (PP) and 70 wt% nickel (Ni). The linear pressure of the touch roll against the cast roll during the production of the conductive film of Example 2 was 0.0 N / mm. That is, the touch roll was not pressed against the cast roll during the production of the conductive film of Example 2. The thickness of the conductive film of Example 2 was 120 μm. The reeling speed of the winding roll during the production of the conductive film of Example 2 was 5.8 m / min.

[0039] The conductive composition used in the production of the conductive film of Example 3 contained 30 wt% polypropylene (PP) and 70 wt% nickel (Ni). The linear pressure of the touch roll against the cast roll during the production of the conductive film of Example 3 was 3.4 N / mm. The thickness of the conductive film of Example 3 was 85 μm. The drawing speed of the winding roll during the production of the conductive film of Example 3 was 1.9 m / min.

[0040] The conductive composition used in the production of the comparative conductive film contained 30 wt% polypropylene (PP) and 70 wt% nickel (Ni). The linear pressure of the touch roll against the cast roll during the production of the comparative conductive film was 130.1 N / mm. The thickness of the comparative conductive film was 100 μm. The drawing speed of the winding roll during the production of the comparative conductive film was 5.8 m / min.

[0041] Examples 1 to 3 and the comparative example are summarized in Table 1 below.

[0042] [Table 1] <5-2. Various measurement methods> (5-2-1. How to measure volume resistance) The volume resistance of each of the conductive films of Examples 1-3 and Comparative Example was measured. Specifically, the volume resistance of each conductive film was measured by the following method. A test piece of the conductive film cut into a 30 mm square was sandwiched between electrodes with a diameter of 20 mm, a voltage was applied in the thickness direction of the test piece, and the resistance value of each conductive film was measured using a resistance meter RM3544-01 manufactured by HIOKI EE. The resistance value (Ω) measured by the resistance meter was multiplied by the contact area (3.14 cm2) between the test piece and the electrodes. 2 ) is the volume resistivity (Ω cm 2 ) was decided.

[0043] (5-2-2. How to measure volume resistance when stacked) For each of the conductive films of Examples 1-3 and Comparative Examples, the volume resistance was measured with the surfaces that would come into contact with the touch roll during molding overlapped together. Specifically, the volume resistance of each conductive film was measured by the following method. Two 30 mm square test pieces were cut out, the surfaces that would come into contact with the touch roll during molding overlapped together, and sandwiched between electrodes with a diameter of 20 mm. A voltage was applied in the thickness direction of the test pieces, and the resistance value of each conductive film was measured using a resistance meter RM3544-01 manufactured by Hioki E.E.C. The resistance value (Ω) measured with the resistance meter was multiplied by the contact area between the test piece and the electrode (3.14 cm2). 2 ) is the volume resistivity (Ω cm 2 ) was decided.

[0044] (5-2-3.Measuring method for surface resistance) The surface resistance of each conductive film of Examples 1-3 and Comparative Example was measured. Specifically, the surface resistance of each conductive film was measured by the following method. A test piece was cut into a 30 mm square, and the surface resistance was measured using a simple low resistance meter Loresta AX MCP-T370 manufactured by Nitto Seiko Analytech Co., Ltd. The PSP probe MCP-TP06P RMH112 was used as the probe. The value obtained by multiplying the resistance value (Ω) measured by the low resistance meter by a correction coefficient (4.532) was taken as the surface resistance (Ω / □).

[0045] (5-2-4. Measurement method using SEM-EDX) The conductive films of Examples 1 to 3 and Comparative Example were measured using SEM-EDX. Specifically, the measurements were performed using SEM-EDX in the following manner.

[0046] The surface that touched the touch roll during molding was used as the measurement surface, and the test piece was set on the observation sample stage of an SEM (Hitachi High-Tech S-4800 Type II) and observed at an accelerating voltage of 15 kV and a magnification of 1000 times. The observed image was obtained, and elemental quantitative analysis was performed using an EDX (Horiba EMAX ENERGY EX-250) attached to the SEM device. The metal filler content in all detected elements was calculated as a volume ratio. The measurement was performed under two conditions: when the observation sample stage was tilted at an angle of 0° and when it was tilted at an angle of 40°. A tilt angle of 0° refers to a state in which the electron beam is irradiated perpendicularly to the test piece, and a tilt of 40° refers to a state in which the observation sample stage is tilted 40° toward the detector from that angle.

[0047] <5-3.Various measurement results> The results of the various measurements are summarized in Table 2 below.

[0048] [Table 2] As shown in Table 2, in each of Examples 1 to 3, various electrical resistance values ​​were lower than those in the comparative example. Also, in each of Examples 1 to 3, in the analysis using SEM-EDX, the ratio of the content of nickel (Ni) detected when the inclination angle of the observation sample stage on which the conductive film test piece was placed was 0° to the content of nickel (Ni) detected when the inclination angle of the observation sample stage was 40° to the content of nickel (Ni) detected when the inclination angle of the observation sample stage was 0° was 0.7 or more. [Explanation of symbols]

[0049] 10 manufacturing equipment, 20 SEM-EDX, 100 T die, 200 casting roll, 300 touch roll, 350 control device, 390 winding roll, 400 observation sample stage, 500 detector, C1 conductive composition, C2 conductive film.

Claims

1. A method for producing a conductive film, comprising the steps of: A step of extruding a conductive composition having a metal filler mixed in a thermoplastic resin through a die; and cooling the conductive composition by a casting roll; The conductive composition includes 30 wt % polypropylene as the thermoplastic resin and 70 wt % nickel as the metal filler, the linear pressure applied to the conductive composition from the opposite side of the casting roll toward the casting roll is 4 N / mm or less.

2. In the step of cooling the conductive composition by the casting roll, the conductive composition is sandwiched between the casting roll and a touch roll, The method for producing a conductive film according to claim 1 , wherein the touch roll applies pressure to the casting roll.

3. A conductive film comprising: As a thermoplastic resin, 30 wt% polypropylene, As a metal filler, 70 wt % nickel is included, A conductive film, in which, in an analysis using SEM-EDX (Scanning Electron Microscope / Energy Dispersive X-ray Spectroscopy), the ratio of the nickel content detected when the inclination angle of an observation sample stage on which a test piece of the conductive film is placed is 0° to the nickel content detected when the inclination angle of the observation sample stage is 40° is 0.7 or more.

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