JP2012204292A - Conductive film and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thin conductive film with high conductivity, even when the thin film is formed of a crystalline resin.SOLUTION: In a conductive film including a crystalline resin and a carbon-based conductive filler, a ratio (weight ratio) of the crystalline resin to the carbon-based conductive filler is adjusted to the former/the latter=90/10-55/45. The film has a thickness of 5-120 μm, and a volume specific resistivity of 0.1-1500 Ω cm. The conductive film has an absolute value of a weight change rate of 10 wt% or less after it is immersed in tetrahydrofuran at 25°C for 24 hours. A conductive carbon black may be used as the carbon-based conductive filler. A polypropylene-based resin and/or a polyamide-based resin may be used as the crystalline resin.

Description

  The present invention relates to a conductive film used for electronic components, semiconductor elements, and the like, and a method for manufacturing the same.

  In various fields where conductivity is required, such as electronic parts and semiconductor elements, a conductive film formed of a resin is used because of excellent moldability and flexibility. In particular, with the recent miniaturization and thinning of electronic components, a thin film is also required for the conductive film used. For example, lithium ion secondary batteries are also mounted on EVs (electric vehicles) and HEVs (hybrid electric vehicles). In particular, in a bipolar battery in which a positive electrode and a negative electrode are stacked via a current collector, a large number of conductive films are stacked as a current collector in a limited space inside the vehicle, so that the thin and light weight is highly conductive. There is a demand for a film having properties.

  As a method for producing a thin-walled conductive film, the resin component is dissolved in a good solvent, then a conductive filler is added, and cast on a substrate to process it into a film, heat in which the conductive filler is dispersed There is known a thermoforming method in which a plastic resin is formed into a film by melt extrusion or rolling.

  As a conductive film obtained by the casting method, WO98 / 40435 (Patent Document 1) contains a thermoplastic elastomer and 5 to 100 parts by weight with respect to 100 parts by weight of the thermoplastic elastomer, and A conductive elastomer film having a volume resistance value of 0.1 to 5 Ω · cm in a direction perpendicular to the film surface is disclosed.

  Japanese Patent Application Laid-Open No. 2011-6534 (Patent Document 2) describes a heavy resin containing 80 to 55% by mass of a cyclic olefin resin and 20 to 45% by mass of a hydrogenated aromatic vinyl-conjugated diene block copolymer. A conductive polymer film containing 100 parts by mass of a coalescing component and 25 to 60 parts by mass of a conductive filler is disclosed.

  However, since the casting method needs to be dissolved in a solvent, a polymer having high solvent resistance, such as a crystalline resin, cannot be formed into a film. In particular, a current collector of a lithium ion battery uses an electrolytic solution containing an organic solvent, and therefore requires high solvent resistance. Furthermore, the casting method has a complicated process of gradually evaporating the solvent while maintaining pinholes generation prevention and coating uniformity, and it is necessary to peel the thin conductive film from the substrate without damaging it. In addition to low properties and convenience, a solvent remains in the obtained conductive thin film.

  On the other hand, as a thermoforming method, Japanese Patent Application Laid-Open No. 2002-75052 (Patent Document 3) includes a low melting point metal having a melting point of 300 ° C. or less and a metal powder, using a thermoplastic resin or a thermoplastic elastomer as a substrate, and A conductive sheet obtained by extruding a conductive resin composition having a melt tension of 0.3 to 15 g at the time of melting is disclosed. In the examples of this document, a thermoplastic elastomer composed of an acid-modified polyolefin is used as the thermoplastic resin or thermoplastic elastomer.

JP 2010-150435 A (Patent Document 4) includes 1 to 99 parts by mass of a polyolefin-based resin, 99 to 1 part by mass of a hydrogenated thermoplastic elastomer, and 1 to 100 parts by mass of a conductive filler. A conductive sheet obtained by extruding a conductive composition having a resistance value of 10 ³ Ω · cm or less is disclosed. In the examples of this document, 60 to 20 parts by mass of a hydrogenated styrene-butadiene block copolymer is blended with 40 to 80 parts by mass of a polypropylene resin.

  Generally, when a thin film is produced by extrusion molding of a resin composition containing a conductive filler, increasing the proportion of the conductive filler in the resin composition is necessary when processing the resin composition into a film. The melt tension is insufficient. That is, the resin (polymer) has a high melt viscosity due to the entanglement between the molecules even at the time of melting, and at the same time has a melt tension. Therefore, when the resin is heated and processed into a film by extrusion, the molten resin that has exited the extrusion mold due to this melt tension suppresses breakage and fluctuations in film thickness even when subjected to tension due to film take-up. It's easy. On the other hand, unlike the resin, the conductive filler has no entanglement between molecules and does not generate melt tension. Therefore, if the proportion of the conductive filler in the resin composition is increased, the film is broken when the film is taken out by extrusion molding. And thickness variation is likely to occur. Therefore, as in Patent Documents 3 and 4, it is necessary to blend an elastic body such as an amorphous thermoplastic elastomer. However, when an amorphous thermoplastic elastomer or a rubber component is blended, the solvent resistance and gas barrier properties of the resin composition are lowered. In particular, the current collector of a lithium ion battery requires extremely high solvent resistance due to the characteristics of the electrolytic solution, but is difficult to use in such applications.

  Moreover, in patent document 3, since a metal material is used as an electroconductive filler, when the specific gravity of a filler is large and the ratio of an electroconductive filler is made high, lightness will fall.

Japanese Patent Laid-Open No. 2010-170833 (Patent Document 5) has a structure including one or more layers having a resin and a conductive material, and a crystalline resin having a melting point of 120 ° C. or more is used as the resin. A current collector for a bipolar secondary battery to be used is disclosed. This document describes that the volume resistivity in the thickness direction (film thickness direction) of the current collector is 10 ² Ω or less, preferably 10 ² to 10 ⁻⁵ Ω. Furthermore, in the examples, pellets were prepared by adding 10% by weight ketjen black to a crystalline resin such as polypropylene, and then the pellets were kneaded and rolled with a rolling mill to produce a current collecting sheet having a thickness of 50 μm. is doing. The electrical resistance in the thickness direction of the obtained current collector sheet is 10 to 100Ω (2000 to 20000Ω · cm in terms of volume resistivity per 1 cm thickness), and has good chemical resistance, oxygen barrier property, and heat press resistance. It is described that it is useful as a current collector for a secondary battery such as a lithium ion battery.

  However, even with such a current collector, since the thin film is produced by the kneading and rolling process, the content of the conductive filler is limited to a small amount, and the conductive filler in the resin composition The conductivity is low because the network structure (secondary structure by the aggregate) cannot be formed.

WO98 / 40435 gazette (Claims) JP 2011-6534 A (Claims) JP-A-2002-75052 (Claims, Examples) JP 2010-150435 A (claims, paragraphs [0018] [0019], examples) JP 2010-170833 A (claims, paragraph [0088], examples)

  Accordingly, an object of the present invention is to provide a conductive film that is formed of a crystalline resin and has high conductivity even when it is thin, and a method for manufacturing the same.

  Another object of the present invention is to provide a conductive film that is thin and highly conductive without substantially containing an elastomer or a rubber component, and a method for producing the same.

  Still another object of the present invention is to provide a conductive film having high solvent resistance and high gas barrier property and a method for producing the same.

  Another object of the present invention is to provide a conductive film excellent in light weight despite its high conductivity, and a method for producing the same.

  As a result of intensive studies to achieve the above-mentioned problems, the present inventors have molded a composition containing a crystalline resin and a carbon-based conductive filler by a specific method that combines extrusion molding and stretching or rolling treatment. Thus, the inventors have found that a novel conductive film having high conductivity can be obtained even if it is formed of a crystalline resin and is thin, and the present invention has been completed.

  That is, the conductive film of the present invention is a conductive film containing a crystalline resin and a carbon-based conductive filler, and satisfies the following characteristics (1) to (4).

(1) The ratio (weight ratio) between the crystalline resin and the carbon-based conductive filler is the former / the latter = 90/10 to 55/45 (2) The film thickness is 5 to 120 μm (3) Volume The specific resistivity is 0.1 to 1500 Ω · cm. (4) The absolute value of the weight change rate after being immersed in tetrahydrofuran at 25 ° C. for 24 hours is 10% by weight or less.

  The carbon-based conductive filler may be conductive carbon black. The crystalline resin may be a polypropylene resin and / or a polyamide resin. The polypropylene resin has a specific gravity of 0.95 or less and may contain 90 mol% or more of propylene units. The polyamide resin may be an aliphatic polyamide resin having a specific gravity of 1.05 or less. In the conductive film of the present invention, the crystalline resin may be a polypropylene resin, and the specific gravity of the film may be about 0.95 to 1.20. The conductive film of the present invention may have a volume resistance of about 0.001 to 5Ω. The conductive film of the present invention may have a thickness variation ratio (maximum thickness / minimum thickness) of 1.5 or less. The conductive film of the present invention may not substantially contain an elastomer.

  In the present invention, when a crystalline resin and a carbon-based conductive filler are extruded to form a sheet having a thickness of 120 to 500 μm, and the melting point of the crystalline resin is mp, (mp-40) The manufacturing method of the said electroconductive film including the extending | stretching or rolling process of extending | stretching or rolling the obtained sheet | seat at the temperature of (degreeC)-(mp-5) degreeC is also included. In the stretching or rolling step, the thickness after treatment may be stretched or rolled to about 1/2 to 1/5 times the thickness before treatment.

  In addition, in this invention, even if the film containing crystalline resin and a carbon-type conductive filler is thin, the mechanism in which high electroconductivity expresses can be estimated as follows.

  First, in the conventional method by extrusion molding, high electrical conductivity can be imparted to a crystalline resin by blending a large amount of conductive filler with a thick sheet. The mechanism by which the conductivity is developed by the conventional method is that the crystalline resin in the molten state and the conductive filler have a specific gravity difference. However, since the conductive filler is usually fine particles, the entire composition melted without settling. To be distributed. However, since the carbon-based conductive filler originally has the property of easily aggregating even if it is a fine particle, it is easy to form a branch-and-leaf structure in which fine particles called aggregates or structures are aggregated. Further, it is presumed that the higher order structure in which the aggregates are in contact with each other is formed as a matrix in the resin, and the conductivity by the conductive filler is exhibited even after being processed as a sheet.

  When a thick sheet is formed by melt extrusion, it is usually solidified after extrusion to widen the slit width or slow down the sheet winding speed in the slit portion where solidification starts from the molten state. However, since the shearing force applied to the sheet hardly acts, it can be presumed that the aggregate and higher-order structure are hardly broken, and a sheet having high conductivity is formed even if it is thick.

  In addition, as the amount of the conductive filler contained in the resin composition increases, the formation of aggregates and the formation of higher-order structures between the aggregates are further promoted. Therefore, the shear force generated during extrusion molding to reduce the thickness However, even if the aggregate or network structure in the hard crystalline resin is partially destroyed, as a result, the conductivity of the resin composition is increased. However, when the amount of conductive filler increases, the melt tension decreases and sheet processing becomes difficult.In addition, when the slit width is narrowed or the sheet winding speed is increased to reduce the sheet thickness, It can be presumed that the resulting shear force is somewhat increased, the aggregates and network structure present in the hard crystalline resin are largely destroyed, and the conductivity of the resulting sheet is reduced.

  Therefore, as described above, in the conventional method, in a thin film of about 110 μm or less, a highly conductive film containing a conductive filler is extruded without adding a soft component such as elastomer or rubber to a hard crystalline resin. It was difficult to manufacture with.

  Therefore, the present inventor has attempted to reduce the thickness of the thick conductive sheet obtained by extrusion molding by stretching or rolling. As a result, when the thick conductive sheet was thinned by stretching or rolling, the conductivity tended to be lower than that of the conductive sheet before thinning. The reason can be presumed that the conductivity is lowered by the destruction of the aggregate and the higher order structure formed of the thick conductive sheet by the stretching or rolling process. In contrast, the present inventor has succeeded in producing a thin film having high conductivity by stretching or rolling by controlling the heating temperature, but this mechanism is controlled by controlling the heating temperature. As a result of controlling the fluidity of the resin when the conductive sheet is stretched and deformed, the aggregate and higher-order structure are substantially maintained without being destroyed, and a thick film before stretching or rolling treatment and It can be presumed that the same high conductivity could be developed in the thin film.

  In the present invention, the conductivity of a thin film formed of a crystalline resin can be improved, probably because a large amount of carbon-based conductive filler is present in an aggregated state in a thin film. In addition, a thin film having high conductivity can be produced without substantially containing an elastomer or a rubber component, and this film has excellent solvent resistance and gas barrier properties. In addition, since the conductive filler is carbon-based, it has excellent lightness despite having high conductivity. In particular, a polypropylene resin or a polyamide resin having a small specific gravity as a resin is excellent in lightness, and particularly when a polypropylene resin is used, the effect of reducing the weight is remarkable. Furthermore, in applications that require low moisture permeability or water absorption, polypropylene resins are more preferably used.

1 is a transmission electron microscope (TEM) photograph of a cross section of a conductive sheet after extrusion molding obtained in Example 1. FIG. FIG. 2 is a transmission electron microscope (TEM) photograph of the cross section of the conductive film after rolling obtained in Example 1.

[Conductive film]
The conductive film of the present invention contains a crystalline resin and a carbon-based conductive filler.

(Crystalline resin)
Examples of the crystalline resin include olefin resins (polyethylene resins such as high density polyethylene, polypropylene resins, etc.), styrene resins (syndiotactic polystyrene, etc.), polyacetal resins (polyoxymethylene, etc.), and polyester resins. Resins (polyalkylene arylates such as polyethylene terephthalate, polybutylene terephthalate and polyethylene naphthalate, liquid crystal polyesters, etc.), polyamide resins (aliphatic polyamides, etc.), polyphenylene sulfide resins, polyether ether ketone, fluororesins (polytetrafluoroethylene) Etc.). These crystalline resins can be used alone or in combination of two or more.

  Of these crystalline resins, polypropylene resins, polyamide resins, polyphenylene sulfide resins, polyether ether ketones, and the like are preferable because they are excellent in heat resistance and mechanical properties, and are excellent in chemical resistance and moldability. From the viewpoint, a polypropylene resin and a polyamide resin are particularly preferable.

(1) Polypropylene resin The polypropylene resin may be a propylene homopolymer (propylene homopolymer) or a propylene copolymer (propylene copolymer). Copolymers include propylene and α-olefins [e.g., ethylene, 1-butene, 2-butene, 1-pentene, 1-hexene, 3-methylpentene, 4-methylpentene, 4-methyl-1-butene, 1 Α-C _2-16 olefins other than propylene such as hexene, 1-octene, 1-nonene, 1-decene, 1-undecene and 1-dodecene (particularly α-C _2-6 olefins such as ethylene and butene), etc. ], For example, propylene-ethylene random copolymer, propylene-butene random copolymer, propylene-ethylene-butene random terpolymer, and the like. In the present invention, from the viewpoints of solvent resistance and heat resistance, it does not substantially contain a copolymerizable unit having a polar group such as maleic acid or (meth) acrylic acid and / or an aromatic vinyl unit such as styrene. Is preferred. Examples of the form of the copolymer include block copolymerization, random copolymerization, and graft copolymerization.

  In the copolymer, the ratio (molar ratio) of propylene and α-olefin (particularly ethylene) is propylene / α-olefin = 90/10 to 100/0, preferably 95/5 to 100/0, more preferably. It is about 99/1 to 100/0. When the proportion of α-olefin is too small, crystallinity is lowered, and solvent resistance and heat resistance are lowered. In the present invention, a homopolymer is preferred.

  The polypropylene resin may be an atactic polymer, but from the viewpoint of improving crystallinity, a structure having stereoregularity such as isotactic and syndiotactic is preferable, and an isotactic polymer is particularly preferable.

  Further, the polypropylene resin may be a polymer using a Ziegler catalyst, but a metallocene resin using a metallocene catalyst from the viewpoint of obtaining a polymer having a low molecular weight tack component and a narrow molecular weight distribution. It is preferable to contain at least (particularly a metallocene copolymer).

  The specific gravity of the polypropylene resin is 1.00 or less (particularly 0.95 or less), for example, 0.80 to 0.95, preferably 0.85 to 0.95, and more preferably 0.87 to 0.93. (Especially about 0.89 to 0.91).

  The melting point of the polypropylene resin (melting peak temperature in the differential scanning calorimeter DSC) can be selected from a range of about 100 to 170 ° C., for example, but is 110 to 170 ° C., preferably 120 to 120 ° C. from the viewpoint of heat resistance. It is about 168 ° C., more preferably about 130 to 166 ° C. (especially 160 to 166 ° C.). In the present specification, the melting point of the polypropylene resin is measured in the form of pellets prepared by melt mixing with the conductive filler.

(2) Polyamide resin Examples of polyamide resins include polyamides obtained by polycondensation of diamine and dicarboxylic acid, polyamides obtained by polycondensation of aminocarboxylic acid, and polyamides obtained by ring-opening polymerization of lactam. And polyamides obtained by polymerizing these monomers in combination.

  Examples of the diamine include trimethylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, 2,2,4-trimethylhexamethylenediamine, 2,4,4-trimethylhexamethylenediamine, octamethylenediamine, and nonamethylene. Aliphatic diamines such as diamines; and alicyclic diamines such as bis (4-aminocyclohexyl) methane and bis (4-amino-3-methylcyclohexyl) methane. In addition, aromatic diamines such as phenylenediamine and metaxylylenediamine may be used in combination. These diamines can be used alone or in combination of two or more.

Examples of the dicarboxylic acid include C _4-20 aliphatic dicarboxylic acids such as glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, and octadecanedioic acid; dimerized fatty acid (dimer acid); cyclohexane Examples include alicyclic dicarboxylic acids such as -1,4-dicarboxylic acid and cyclohexane-1,3-dicarboxylic acid; aromatic dicarboxylic acids such as phthalic acid, phthalic anhydride, isophthalic acid, terephthalic acid, and naphthalenecarboxylic acid. . These dicarboxylic acids can be used alone or in combination of two or more.

Examples of aminocarboxylic acids include C _4-20 aminocarboxylic acids such as aminoheptanoic acid, aminononanoic acid, and aminoundecanoic acid. Aminocarboxylic acids can be used alone or in combination of two or more. These aminocarboxylic acids can be used alone or in combination of two or more.

Examples of the lactam include C _4-20 lactams such as butyrolactam, bivalolactam, caprolactam, capryllactam, enantolactam, undecanolactam, and dodecalactam. These lactams can be used alone or in combination of two or more.

  Polyamide resins include aliphatic polyamides such as polyamide 46, polyamide 6, polyamide 66, polyamide 610, polyamide 612, polyamide 11 and polyamide 12, aromatic dicarboxylic acids (for example, terephthalic acid and / or isophthalic acid) and aliphatic. Obtained from polyamides obtained from diamines (eg hexamethylenediamine, nonamethylenediamine, etc.), aromatic and aliphatic dicarboxylic acids (eg terephthalic acid and adipic acid) and aliphatic diamines (eg hexamethylenediamine) Examples thereof include polyamide. These polyamide-based resins are not limited to homopolyamide but may be copolyamide. These polyamide resins can be used alone or in combination of two or more.

Of these polyamide-based resins, aliphatic polyamides such as polyamide 46, polyamide 6, polyamide 66, polyamide 610, polyamide 612, polyamide 11, and polyamide 12 are preferable because of high crystallinity and excellent heat resistance. These aliphatic polyamides can be selected depending on the use, and when improving crystallinity such as uses where heat resistance and gas barrier properties are important, aliphatic polyamides having a C _2-12 alkylene chain (particularly polyamide 46). And aliphatic polyamides having a C _3-8 alkylene chain such as polyamide 66). In applications where moldability and solvent resistance are important, aliphatic polyamides having C _8-16 alkylene chains (particularly aliphatic polyamides having C _10-14 alkylene chains such as polyamide 11 and polyamide 12) are preferred.

  The specific gravity of the polyamide-based resin is 1.05 or less, for example, about 0.80 to 1.04, more preferably about 0.90 to 1.02.

  The melting point of the polyamide-based resin (melting peak temperature in the differential scanning calorimeter DSC) can be selected from a range of about 100 to 250 ° C., for example, but is 140 to 220 ° C., preferably 150 to 150 ° C. from the viewpoint of heat resistance. It is 200 degreeC, More preferably, it is about 160-190 degreeC (especially 170-180 degreeC) grade. In the present specification, the melting point of the polyamide-based resin is measured in the state of pellets prepared by melt mixing with the conductive filler.

  Of these crystalline resins, polypropylene resins are particularly preferred because they are excellent in chemical resistance, gas barrier properties, toughness, and economy in addition to the above-mentioned properties.

(Carbon conductive filler)
Examples of the carbon conductive filler include artificial graphite, expanded graphite, natural graphite, coke, carbon nanotube, conductive carbon black, and carbon fiber. In the present invention, since a carbon-based conductive filler is used as the conductive filler, it is superior in lightness compared to a metal filler, and even if a large amount of filler is blended with the crystalline resin, the lightness is not greatly impaired. These conductive fillers can be used alone or in combination of two or more.

  Although it is difficult to determine the true specific gravity of carbon-based conductive fillers, especially nano-level particulate fillers, the specific gravity of carbon-based conductive fillers is 2.5 or less, for example, 0.30 to 2.5, preferably Is about 0.45 to 2.0, more preferably about 1.0 to 2.0 (especially 1.4 to 1.9).

  Examples of the shape of these carbon-based conductive fillers include particulate (powder), plate (or scale), fibrous, and indefinite shape. Of these shapes, particle shapes such as a substantially spherical shape and a polygonal shape are widely used.

  In the present invention, among these carbon-based conductive fillers, conductive carbon black is preferable from the viewpoint of conductivity and lightness.

  Examples of the conductive carbon black include furnace black, channel black, gas black, acetylene black, arc black, and ketjen black. These conductive carbon blacks can be selected depending on the application.For example, acetylene black with low oil content may be used to improve flame retardancy, and hollow shell structure ketjen black is used to improve lightness. May be.

  Of these conductive carbon blacks, furnace black, ketjen black, acetylene black and the like are preferable from the viewpoint of conductivity. Further, a conductive composite carbon black obtained by combining these conductive carbon blacks may be used.

  Commercially available products of conductive carbon black include ketjen black (“EC600JD” and “EC300J” manufactured by Ketjen Black International Co., Ltd.), ketjen black (“MBP1853” manufactured by Ketjen Black International Co., Ltd.), Acetylene black (“Denka Black HS-100” manufactured by Denki Kagaku Kogyo Co., Ltd.), Furnace Carbon Black (“Toka Black # 5500”, “Toka Black # 4300” manufactured by Tokai Carbon Co., Ltd.) and “Made by Mitsubishi Chemical Corporation” # 3030B "," # 3400B ") and the like, and conductive carbon black having different characteristics such as particle diameter and cohesiveness.

  The average primary particle diameter (calculated average particle diameter obtained by observation with a transmission electron microscope) of the carbon-based conductive filler (for example, conductive carbon black) can be appropriately selected from a range of about 10 μm or less, but is dispersed in a thin film. From the point which makes it, 1 micrometer or less is preferable, and also from the point etc. which can suppress the smoothness of a film, a pinhole, and a tear, For example, 1-1000 nm, Preferably it is 5-100 nm, More preferably, it is 10-60 nm (especially 10-50 nm). Degree.

  In the conductive film of the present invention, the carbon-based conductive filler (for example, conductive carbon black) has such a primary particle size, but the primary particles in the film are aggregates (aggregates). Furthermore, it can be estimated that it has formed. It can be presumed that this aggregate structure is maintained even in a thin film, forms a network structure with many contact points between particles, and improves the conductivity of the film.

Carbon-based conductive fillers (eg, conductive carbon black) DBP (dibutyl phthalate) oil absorption amount of (A method of JIS K6221), depending on the application, 10~1000cm ³ / 100g (e.g., 30~500cm ³ / 100g The nitrogen adsorption BET specific surface area is 20 m ² / g or more, preferably 25 m ² / g or more (for example, 25 to 2000 m ² / g), more preferably 30 m ² / g or more (for example, 30 ˜1500 m ² / g).

  The ratio (weight ratio) between the crystalline resin and the carbon-based conductive filler is the former / the latter = 90/10 to 55/45, preferably 85/15 to 55/45, more preferably 85/15 to 60. / 40 (especially 80/20 to 60/40). When the content of the conductive filler is too small, the volume specific resistance value of the thin-walled conductive film becomes high. Conversely, when the content is too large, the sheet moldability and the sheet physical properties tend to decrease.

  Note that special fillers (such as ketjen black) that have internal voids or cavities such as hollow structures and tube structures have a small apparent density and therefore have a large volume and an aggregate structure with respect to the weight added to the resin composition. On the other hand, the influence of the filler on the kneading and melt extrusion characteristics becomes larger. Therefore, although the true specific gravity of the composition is low and a film having high electrical conductivity can be obtained even with a small addition amount, the upper limit of the addition weight is higher than other carbon-based fillers with a large apparent density because of the workability of the composition. Tend to be low. In addition, a structure having voids or cavities tends to be destroyed by mechanical shearing force such as kneading, extrusion molding, stretching, rolling, etc., compared to fillers substantially free of internal voids, such as acetylene black. is there. Therefore, when using the filler which has a space | gap or a cavity inside, it is necessary to pay attention to the conditions in each step.

  The ratio between the crystalline resin and the carbon-based conductive filler may be adjusted according to the specific gravity of the carbon-based conductive filler, and although it is difficult to obtain the true specific gravity of nano-level granular carbon black, for example, the specific gravity is In the case of 2.0 to 1.7 (especially 1.9 to 1.8) filler (for example, acetylene black), crystalline resin / carbon-based conductive filler = 80/20 to 55/45, preferably 75 / It may be about 25 to 55/45, more preferably about 70/30 to 60/40. In the case of a filler (for example, ketjen black) having a true specific gravity of 0.3 to 1.6 (particularly 0.4 to 1.5), crystalline resin / carbon-based conductive filler = 90/10 to 70 / It may be 30, preferably 90/10 to 80/20, more preferably about 90/10 to 85/15.

  Furthermore, the carbon-based conductive filler is based on each of the above characteristics, and within a processable range from kneading of the composition to obtaining a conductive film, alone or in combination of two or more kinds in the composition. By selecting a ratio, various physical properties resulting from the composition, such as volume-specific low efficiency and specific gravity, may be imparted to the desired conductive film.

(Other additives)
The conductive film of the present invention further contains conventional additives such as other polymers (amorphous resins, amorphous elastomers, crystalline elastomers, rubbers, etc.), plasticizers, other conductive fillers, conductive properties. Polymer, stabilizer (heat stabilizer, ultraviolet absorber, light stabilizer, antioxidant, etc.), dispersant, antistatic agent, colorant, lubricant, crystal nucleating agent, flame retardant, flame retardant aid, filling Agents, impact resistance improvers, reinforcing agents, foaming agents, antibacterial agents and the like. These additives can be used alone or in combination of two or more. The ratio of these additives is, for example, 10 parts by weight or less, preferably 0.01 to 5 parts by weight, more preferably 0.05 to 100 parts by weight with respect to the total of 100 parts by weight of the crystalline resin and the carbon-based conductive filler. About 3 parts by weight (particularly 0.1 to 2 parts by weight).

  The conductive film of the present invention may contain a soft component such as an elastomer or rubber as long as it is in the above proportion, but substantially contains a soft component such as an elastomer or rubber (especially an elastomer such as an amorphous elastomer). It does not have to be contained. In the present invention, a thin and highly conductive film can be prepared without containing a soft component, although it is substantially formed of a crystalline resin as a resin component.

(Characteristics of conductive film)
The conductive film of the present invention is a thin film having a thickness of 120 μm or less. Specifically, the thickness of the conductive film can be selected from the range of about 5 to 120 μm (for example, 5 to 110 μm), preferably about 10 to 100 μm, more preferably about 15 to 80 μm (particularly 20 to 60 μm), and usually It is about 25-50 micrometers (for example, 30-45 micrometers).

  The conductive film of the present invention has high thickness uniformity, and the thickness variation ratio (maximum thickness / minimum thickness) is, for example, 1.5 or less (for example, 1 to 1.5), preferably 1.01 to 1. .4, more preferably about 1.03 to 1.3 (particularly 1.05 to 1.25), for example, about 1.1 to 1.2. Since the conductive film of the present invention has a uniform thickness, for example, even when a plurality of films are laminated, a large gap is not generated, and the adhesiveness is high, and the conductivity uniformity and stability are also high. The thickness variation ratio can be measured by the method described in Examples described later.

  The conductive film of the present invention is characterized by having high conductivity while being thin. The volume resistivity of the conductive film of the present invention is 0.1 to 1500 Ω · cm, preferably 1 to 1000 Ω · cm, more preferably 2 to 500 Ω · cm (particularly 3 to 100 Ω · cm), For example, it may be about 1 to 50 Ω · cm (particularly 2 to 10 Ω · cm). The volume resistance value of the conductive film of the present invention is, for example, about 0.001 to 5Ω, preferably about 0.01 to 3Ω, and more preferably about 0.1 to 1Ω.

  The conductive film of the present invention is excellent in solvent resistance, and the absolute value of the weight change after immersion in tetrahydrofuran at 25 ° C. for 24 hours is 10% by weight or less, for example, 0.05 to 8% by weight. %, Preferably 0.5 to 5.0% by weight, more preferably about 0.5 to 4.0% by weight. In applications where high solvent resistance is required, for example, 0.5 to 3. It may be about 0% by weight, preferably 0.5 to 2.0% by weight, more preferably about 0.5 to 1.5% by weight (particularly 0.5 to 1.0% by weight).

  The specific gravity of the conductive film of the present invention is, for example, 0.75 to 1.20, preferably 0.80 to 1.18, more preferably 0.85 to 1.15 (particularly 0.90 to 1.15). Degree. When the crystalline resin is a polypropylene resin, the specific gravity of the film is, for example, 0.95 to 1.2, preferably 0.96 to 1.18, more preferably 0.97 to 1.15 (particularly 1. It may be about 0 to 1.1).

[Method for producing conductive film]
The method for producing a conductive film of the present invention includes an extrusion molding process in which a crystalline resin and a carbon-based conductive filler are extruded to form a sheet having a thickness of 120 to 500 μm, and the melting point of the crystalline resin is mp. A stretching or rolling step is performed in which the obtained sheet is stretched or rolled at a temperature of (mp-40) ° C. to (mp-5) ° C. while being heated.

  In the present invention, the crystalline resin and the carbon-based conductive filler subjected to the extrusion molding process may be prepared into pellets by melt kneading in advance. As a method of melt kneading, a conventional method, for example, a method using a mixer such as a pressure kneader kneader, a Banbury mixer, a mixing roll, or the like can be used. Furthermore, you may pelletize using a feeder luder etc. after melt-kneading. In this invention, workability | operativity, such as adjustment between each process of sheet | seat processing, can be improved by pelletizing. In addition, as a method of melt kneading, each component may be dry-mixed with a Henschel mixer or a ribbon mixer, and melt kneading and pelletization may be simultaneously performed using a single screw or twin screw extruder.

(Extrusion process)
In the extrusion process, the obtained pellets or dry mixture is produced into a sheet using an extruder (for example, a single-screw or twin-screw extruder) or a calendar molding machine, and the pellets are usually placed in the extruder. The mixture is melt-kneaded and extruded from the slit of the die (die) at the tip of the extruder. The die (die) may be a ring die used for inflation molding, but usually a T die such as a multi-manifold die or a flat die can be used. Further, the extruded sheet is cooled by a cooling roll and can be wound on a sheet winder.

  The conditions for extrusion molding can be selected according to the type of the extruder and the crystalline resin, and the molding temperature is about 100 to 280 ° C, preferably about 150 to 260 ° C, and more preferably about 180 to 250 ° C. The cooling temperature by a cooling roll is 80-200 degreeC, for example, Preferably it is 100-180 degreeC, More preferably, it is about 120-160 degreeC. Further, the gap (clearance or gap) of the extrusion slit is 0.5 to 2.0 mm, preferably 0.6 to 1.5 mm, and more preferably 0.7 to 1.0 mm. The take-up speed (winding speed) is, for example, 0.1 to 70 m / min, preferably 0.5 to 40 m / min, more preferably 1.5 to 30 m / min (particularly about 2 to 10 m / min). .

  In the present invention, the characteristics of the apparatus are adjusted so that each resin composition has a thickness of 120 to 500 μm, preferably 130 to 400 μm, and more preferably 130 to 300 μm (particularly 130 to 250 μm). It is adjusted at the combined winding speed.

  In the present invention, the sheet is once adjusted to such a thickness by extrusion, but in this state, the conductive filler is appropriately aggregated (aggregated) in the sheet to form a network structure. Or high conductivity. The obtained sheet has a volume resistivity of 1000 Ω · cm or less, preferably 0.1 to 500 Ω · cm, more preferably 0.2 to 200 Ω · cm (particularly 0.3 to 100 Ω · cm). .

(Stretching or rolling process)
In the stretching or rolling process, the roll sheet obtained in the extrusion process is unwound and stretched or rolled. The stretching or rolling process is performed with the sheet heated, but in the method of the present invention, the conductive filler network structure formed in the extrusion process is not broken in the stretching or rolling process. The heating temperature in the treatment is controlled. The heating temperature in the stretching or rolling treatment is a temperature range of (mp-40) ° C. to (mp-5) ° C., preferably (mp−35) ° C. to (mp, where mp is the melting point of the crystalline resin. −5) ° C., more preferably (mp-30) ° C. to (mp-10) ° C. [particularly, (mp-30) ° C. to (mp-15) ° C.]. If the heating temperature is too high, the conductivity decreases because the molecular chain of the molten polymer enters the network structure of the conductive filler. In addition, the polymer is softened or melted, and tends to be in close contact with the rotating roll or difficult to tear and wind. On the other hand, if the heating temperature is too low, a high shearing force is applied to the resin composition and the network structure is destroyed. Moreover, since the fluidity | liquidity of a polymer is low, a sheet | seat is not fully thinned but it becomes easy to tear. On the other hand, in the method of the present invention, the heating temperature in stretching or rolling is controlled to an appropriate range. For example, the network structure is reduced in the thickness direction so that the pantograph is folded. Alternatively, high conductivity can be maintained even after the rolling process.

  In the stretching or rolling process, the thickness of the thin film after treatment may be adjusted to about 1 / 1.2 to 1/10 times that of the sheet before treatment, for example, 1 / 1.5-1 to 1. / 8 times, preferably 1/2 to 1/5 times, more preferably about 1 / 2.5 to 1 / 4.5 times.

  In the stretching step, the stretching treatment may be uniaxial stretching or biaxial stretching. The biaxial stretching may be simultaneous biaxial stretching or sequential biaxial stretching. The draw ratio may be adjusted so that the thickness of the thin film falls within the above range, and can be selected from a range of about 1.1 to 10 times, preferably 1.5 to 5 times, more preferably 2 to 5 times. It is about twice.

  In the rolling step, the load of the rolling treatment can be selected from about 100 kN or less, for example, 0.1 to 100 kN, preferably 0.5 to 50 kN, more preferably 1 to 30 kN (particularly 2 to 10 kN). If the rolling pressure increases, the shearing force applied to the thick sheet increases, or the volume-specific low efficiency of the thin film tends to increase. Therefore, the load applied to the sheet from the heating roll is preferably small.

  In the rolling process, a drawing process may be applied in the longitudinal direction of the sheet by increasing the winding speed of the winder from the supply speed of the original sheet. The ratio of the winding speed to the supply speed (winding speed / supply speed) is, for example, about 1 to 10 times, preferably 1.5 to 8 times, more preferably 2 to 5 times (particularly 3 to 4.5 times). is there. This ratio can be selected from this range in accordance with the processing temperature and the applied load, and the thickness of the film may be adjusted by adjusting these conditions. In the rolling process, the relationship between the load load and the speed ratio is preferably such that the load ratio is reduced and the speed ratio is increased from the viewpoint that the film thickness can be made uniform and the conductivity can be improved. Furthermore, from the point of making the film thickness uniform and improving the conductivity, a stretching process without applying a load may be used. In particular, a conductive filler having a cavity structure such as ketjen black can maintain high conductivity even after stretching or rolling because the destruction of the cavity structure can be suppressed.

  Further, in the stretching or rolling step, a lubricant or a release agent may be applied to the sheet surface in order to improve workability, or a plurality of rolls may be combined.

  The obtained thin conductive film may be annealed by a conventional method in order to release the residual distortion of the thinned film. The annealing temperature is, for example, (mp-60) ° C to (mp-5) ° C, preferably (mp-55) ° C to (mp-10), where mp is the melting point of the crystalline resin. More preferably, it is (mp-50) ° C to (mp-20) ° C.

  Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples. The compounding components used in the examples and comparative examples, and the evaluation of the conductive film properties obtained in the examples and comparative examples were measured by the following methods.

[specific gravity]
Based on JIS K7112, specific gravity was calculated | required from the sample density measured using the electronic hydrometer ("Electronic Densometer SD-200L" by Alpha Mirage Co., Ltd.). In addition, in a bulky sample or the like, when a sample shape appropriate for measurement could not be obtained, the sample was cut out after being previously formed by hot pressing.

[Melt flow rate (MFR) and melt tension]
MFR (g / 10 minutes) of a resin composition (for example, pellets) prepared by melt kneading is based on JIS K7210, using a capillary rheometer (“Capillograph 1D” manufactured by Toyo Seiki Seisakusho) The measurement was performed under the conditions of 230 ° C. and 21.2 N load. Moreover, the melt tension of 200 degreeC and 240 degreeC of the said composition was also measured using the same apparatus. The melt tension was measured under the measurement conditions of extrusion speed: 0.05 m / min, pulling speed: 3 m / min, capillary diameter: 2 mmφ, land length: 20 mm.

[Melting point / Glass transition temperature]
The melting point (mp) and glass transition temperature (Tm) of a resin composition (for example, pellets) prepared by melt kneading were measured. The measurement was performed by a normal thermal analysis method using a differential scanning calorimeter (DSC) (trade name “Q2000” manufactured by TA Instruments Inc.).

[Thickness and uniformity of sheet or film]
Using a micrometer ("Digimatic Micrometer MDC25MJ" manufactured by Mitutoyo Co., Ltd.), the film was measured at 10 points or more at 25 mm intervals in the film width direction (TD), and the film flow direction (MD) The measurement was performed at 10 points or more at intervals of 25 mm, and the arithmetic average value was obtained from the measured values of 20 points or more in total. Similarly, the uniformity (or stability) of the thickness is 1 m in the flow direction (MD) at the center of the film, and the thickness is measured at intervals of 50 mm. The average value of 5 points was calculated as thickness variation ratio = (maximum average value / minimum average value). The smaller the ratio, the more stable the film thickness.

[Conductivity (volume resistivity)]
In accordance with JIS K7194, the surface resistivity was measured using a surface resistance meter (manufactured by Mitsubishi Chemical Corporation, “Loresta Loresta-GP”) to determine the volume resistivity.

[Solvent resistance]
The film was cut into 100 mm × 100 mm, and the initial weight: A (mg) was measured. Next, the film was completely immersed in tetrahydrofuran (THF) at 25 ° C. and allowed to stand for 24 hours, and then the surface of the taken out film was wiped off, and the weight: B (mg) was measured again. The weight change rate was calculated based on the following formula, and then evaluated according to the following criteria.

Weight change rate (%) = [(BA) / A] × 100 (%)
◎: Less than ± 1% ○: ± 1% or more and less than ± 5% Δ: ± 5% or more and less than ± 10% ×: ± 10% or more.

[MIT test]
In accordance with a folding test method using an MIT testing machine defined in JIS P8115, a strip with a width of 15 mm was usually sampled for a long time in the film flow direction (MD), which is the direction in which breakage tends to occur, and used for the MIT test. The test results were evaluated according to the following criteria.

A: The number of times until breakage is 1000 times or more. ○: The number of times until breakage is 100 times or more and less than 1000 times. Δ: The number of times until breakage is less than 100 times.

[Transmission electron microscope (TEM) observation]
Using a transmission electron microscope (“JEM-1200EX” manufactured by JEOL Ltd.), the acceleration voltage was 80 kV. The sample for TEM observation uses an ultramicrotome (LEICA ULTRCUT UCT, LEICA EM FCT, manufactured by Leica Co., Ltd.) and a diamond knife (Cryo dry, manufactured by DiATOME) to produce an ultrathin section having a thickness of 100 nm on a copper mesh. Observed.

[Ingredients]
Homopolypropylene (PP-1): “E-100GPL” manufactured by Prime Polymer Co., Ltd., MFR: 0.9, specific gravity 0.900 (converted from density)
General-purpose polypropylene (PP-2): “Novatec (registered trademark) EA9” manufactured by Nippon Polypro Co., Ltd., MFR: 0.5, specific gravity 0.90 to 0.91 (converted from density)
Homopolypropylene (PP-3): Prime polymer "F744NP", MFR: 7.0, specific gravity 0.900 (converted from density)
Random polypropylene (PP-4): “B221WA” manufactured by Prime Polymer Co., Ltd., MFR: 0.5, specific gravity 0.910 (converted from density)
Polyamide 12 (PA12): “L1901” manufactured by Daicel Evonik Co., Ltd., specific gravity 1.01.

Polyolefin elastomer (PPE-1): “DYNARON (registered trademark) 1320P” manufactured by JSR Corporation, hydrogenated styrene / phthaldiene rubber, styrene content 10%, MFR: 3.5, specific gravity 0.89
Polyolefin elastomer (PPE-2): “Dynalon (registered trademark) 4600P” manufactured by JSR Corporation, styrene-ethylene-butylene-ethylene block copolymer, styrene content 10%, MFR: 5.6, specific gravity 0.91
Polyolefin elastomer (PPE-3): “Dynalon (registered trademark) 6200P” manufactured by JSR Corporation, ethylene-ethylene-butylene-ethylene block copolymer, styrene content 0%, MFR: 2.5, specific gravity 0.88.

Acetylene black (CB-1): “Denka Black HS-100” manufactured by Denki Kagaku Kogyo Co., Ltd., average primary particle size 48 nm, BET specific surface area 39 m ² / g, specific gravity 1.9
Furnace black (CB-2): Tokai Carbon Co., Ltd., "Tokablack ♯5500", average primary particle size 25 nm, BET specific surface area of 225 m ² / g, DBP oil absorption 155cm ^3/100 g, specific gravity 1.8
Ketchen black (CB-3): Ketjen Black International Co., Ltd. "EC600JD", BET specific surface area of 1270m ² / g, DBP oil absorption of 495cm ³ / 100g
Ketjen black has a special structure, and it can be estimated that its average primary particle size is at least a true average particle size of 50 nm or more and at most 100 nm. Furthermore, since the specific gravity of each filler is a value after hot pressing, it can be estimated that the specific gravity is slightly estimated. In particular, ketjen black is at least 0.36 or more, at most 1. It can be estimated that the specific gravity is 5 or less.

Example 1
45 parts by weight of homopolypropylene (PP-1) and 25 parts by weight of homopolypropylene (PP-3) as resin components, 40 parts by weight of carbon black (CB-1) as a conductive filler were blended in a pressure kneader kneader, It melt-mixed, and also was made into the pellet with the feeder ruder. When the characteristics of the pellet were measured, the specific gravity was 1.07, the melting point (mp) was 166 ° C., and the glass transition temperature (Tm) was −22 ° C.

  The MFR was 0.31 g / 10 min, and the melt tension was 200 ° C .: 41 mN and 240 ° C .: 28 mN.

  The obtained pellets were supplied to a T-die extrusion molding machine, extruded into a sheet shape from an extrusion slit gap of 0.8 mm to an extrusion temperature of 230 ° C., wound at a winding speed of 2.7 m / min, and had a thickness of 131 μm. A conductive sheet was obtained. The volume resistivity of this sheet was 35 Ω · cm. A TEM photograph of the sheet cross section is shown in FIG. As is apparent from FIG. 1, the sheet has an aggregate structure formed by agglomerating carbon black (black particles) present in the resin composition.

  Next, while rewinding the roll sheet, between two heating rolls having a surface temperature of 140 ° C. (thermal stretching temperature difference = composition melting point−heating roll surface temperature = −26 ° C.) at a roll load of 5 kN, While being contact-heated from both sides of the sheet, the sheet was passed at a feeding speed of 1 m / min and a winding speed of 2.8 m / min to perform a heat stretching process. The obtained conductive film is a conductive film having a thickness of 44 μm and a specific volume resistivity of 53 Ω · cm. From the results of the thickness fluctuation ratio, MIT test, and solvent resistance test, the film is smooth and has almost no thickness fluctuation. It was confirmed that the thin conductive film had excellent mechanical properties and excellent solvent resistance. A TEM photograph of the cross section of the conductive film is shown in FIG. As is apparent from FIG. 2, the aggregate structure before stretching is retained without being broken even after heat stretching.

Example 2
70 parts by weight of random polypropylene (PP-4) as a resin component and 30 parts by weight of furnace carbon black (CB-2) as a conductive filler are mixed in a pressure kneader kneader, melt-mixed, and further pelleted by a feeder ruder. It was. When the characteristics of the pellet were measured, the specific gravity was 1.07, the melting point (mp) was 139 ° C., and the glass transition temperature (Tm) was −21 ° C. The melt flow rate (MFR) was 0.01 g / 10 min, and the melt tension was 200 ° C .: 74 mN, 240 ° C .: 60 mN. The melt flow rate (MFR) when the measurement temperature was changed from 230 ° C. to 260 ° C. was 0.08 g / 10 min.

  The obtained pellets were supplied to a T-die extrusion molding machine, extruded into a sheet shape under the same conditions as in Example 1, and wound up with a winder at a winding speed of 1.6 m / min to obtain a conductive sheet having a thickness of 230 μm. Obtained. The volume resistivity of this sheet was 12.0 Ω · cm.

  Then, while rewinding the roll sheet, the film was heat-stretched under the same conditions as in Example 1 except that only the heat-stretching temperature difference was changed from −26 ° C. to −9 ° C. to obtain a conductive film.

Example 3
68 parts by weight of homopolypropylene (PP-1) as a resin component and 32 parts by weight of carbon black (CB-1) as a conductive filler are blended in a pressure kneader kneader, melt mixed, and further pelletized with a feeder ruder. did. When the characteristics of the pellet were measured, the specific gravity was 1.08, the melting point (mp) was 166 ° C., and the glass transition temperature (Tm) was −22 ° C.

  The obtained pellets were supplied to a T-die extrusion molding machine, extruded into a sheet shape under the same conditions as in Example 1, and wound up at a winding speed of 2.5 m / min to obtain a conductive sheet having a thickness of 140 μm. The volume resistivity of this sheet was 8.0 Ω · cm.

  Then, while rewinding the roll sheet, the film was subjected to heat stretching under the same conditions as in Example 1 except that only the heat stretching temperature difference was changed from −26 ° C. to −25 ° C. to obtain a conductive film.

Examples 4-10
The type and composition ratio of the resin component and the conductive filler are replaced with the types and composition ratios shown in Table 1, and the sheet processing by melt mixing and extrusion is adjusted so that the sheet is stably obtained. Otherwise, the same procedure as in Example 1 was performed to obtain a conductive sheet. Furthermore, the conductive film was obtained by appropriately adjusting the film processing conditions (thermal stretching temperature difference, heating roll load, winding speed) in the step of thermally stretching the conductive sheet.

Example 11
88 parts by weight of polyamide 12 as a resin component and 20 parts by weight of carbon black (CB-1) as a conductive filler were mixed in a pressure kneader kneader, melt-mixed, and further pelletized with a feeder ruder. When the characteristics of the pellet were measured, the specific gravity was 1.17, the melting point (mp) was 178 ° C., and the glass transition temperature (Tm) was 50 ° C.

  The obtained pellets were supplied to a T-die extrusion molding machine and extruded into a sheet shape from an extrusion slit gap of 0.8 mm to an extrusion temperature of 220 ° C., wound at a winding speed of 2.5 m / min, and had a thickness of 131 μm. A conductive sheet was obtained. The volume resistivity of this sheet was 35 Ω · cm.

  Next, the sheet in the same manner as in Example 1 except that the surface temperature of the heating roll was changed to 150 ° C. (thermal stretching temperature difference = composition melting point−heating roll surface temperature = −28 ° C.) while rewinding the roll sheet. While being heated from both sides, a heat-stretching treatment was performed to obtain a conductive film.

Example 12
The composition ratio was changed to the composition ratio shown in Table 1, and extrusion molding was performed in the same manner as in Example 11 except that the film was wound at a winding speed of 1.6 m / min. Thus, a conductive sheet having a thickness of 205 μm was obtained. Next, while rewinding the roll-shaped sheet, the surface temperature of the heating roll is 163 ° C. (thermal stretching temperature difference = composition melting point−heating roll surface temperature = −15 ° C.), feeding speed is 1 m / min, winding speed is 2.3 m. A conductive film was obtained in the same manner as in Example 11 except for replacing with / min.

Example 13
45 parts by weight of homopolypropylene (PP-1) and 25 parts by weight of homopolypropylene (PP-3) as resin components, 40 parts by weight of carbon black (CB-1) as a conductive filler were blended in a pressure kneader kneader, It melt-mixed, and also was made into the pellet with the feeder ruder. When the characteristics of the pellet were measured, the specific gravity was 1.07, the melting point (mp) was 166 ° C., and the glass transition temperature (Tm) was −22 ° C.

  The obtained pellets were supplied to a T-die extrusion molding machine, extruded into a sheet shape from an extrusion slit gap of 0.8 mm to an extrusion temperature of 230 ° C., wound at a winding speed of 2.7 m / min, and a thickness of 130 μm. A conductive sheet was obtained. The volume resistivity of this sheet was 30 Ω · cm.

  Next, a heat-stretching treatment was performed in the same manner as in Example 1 except that the roll load was changed to 30 kN while the roll-shaped sheet was rewound to obtain a conductive film.

  The results of the conductive films obtained in Examples 1 to 13 are shown in Table 1.

  As is clear from the results in Table 1, the conductive films of the examples are excellent in various characteristics.

Comparative Example 1
50 parts by weight of homopolypropylene (PP-1) as a resin component and 50 parts by weight of carbon black (CB-1) as a conductive filler are mixed in a pressure kneader kneader, melt mixed, and further pelletized with a feeder ruder. did. The pellets were supplied to a T-die extrusion molding machine, and extrusion molding was attempted at an extrusion temperature of 230 ° C. However, the sheet was broken and extrusion molding was impossible.

Comparative Example 2
70 parts by weight of homopolypropylene (PP-1) as a resin component and 30 parts by weight of carbon black (CB-1) as a conductive filler are mixed in a pressure kneader kneader, melt-mixed, and further pelletized by a feeder ruder. did.

  The obtained pellets were supplied to a T-die extrusion molding machine, extruded into a sheet shape from an extrusion slit gap of 0.8 mm to an extrusion temperature of 230 ° C., wound at a winding speed of 2.5 m / min, and had a thickness of 140 μm. A conductive sheet was obtained. The volume resistivity of this sheet was 8.0 Ω · cm.

  Next, while rewinding the roll sheet, the surface temperature of the heating roll is 163 ° C. (thermal stretching temperature difference = composition melting point−heating roll surface temperature = −3 ° C.) and the roll load is 5 kN. However, the heat stretching process was performed at a feeding speed of 1.0 m / min and a winding speed of 3.0 m / min, but the sheet stuck to the roll and the stretching process was difficult.

Comparative Examples 3 and 4
Instead of the types and composition ratios of the resin component and conductive filler shown in Table 2, the sheet processing by melt mixing and extrusion is performed in the same manner as in Example 1, and the film processing conditions by hot stretching are shown in Table 2. The conductive film was obtained by adjusting to the conditions shown in FIG.

Comparative Example 5
Mixing 55 parts by weight of homopolypropylene (PP-1) and 25 parts by weight of olefin elastomer (PPE-1) as resin components and 30 parts by weight of ketjen black (CB-3) as conductive fillers in a pressure kneader kneader. The mixture was melted and mixed, and further pelletized with a feeder ruder.

  The obtained pellets were supplied to a T-die extrusion molding machine, extruded into a sheet shape from an extrusion slit gap of 0.8 mm to an extrusion temperature of 230 ° C., wound up at a winding speed of 4.5 m / min, and had a thickness of 80 μm. A conductive sheet was obtained. This sheet was subjected to various tests without being subjected to stretching treatment.

Comparative Examples 6-7
A conductive film was obtained in the same manner as in Comparative Example 5 except that the types and composition ratios of the resin component and conductive filler were changed to the types and composition ratios shown in Table 2.

Comparative Example 8
Instead of the types and composition ratios of the resin component and conductive filler shown in Table 2, the sheet processing by melt mixing and extrusion is performed in the same manner as in Example 1, and the film processing conditions by hot stretching are shown in Table 2. The conductive film was obtained by adjusting to the conditions shown in FIG.

  The results of the conductive films obtained in Comparative Examples 1 to 8 are shown in Table 2.

  As is clear from the results in Table 2, the conductive film of the comparative example is difficult to manufacture or does not satisfy various characteristics.

Example 14
The conductive films obtained in Examples 1 to 7 were annealed at 130 ° C. for 3 minutes and then allowed to stand at 140 ° C. for 3 minutes, but the conductive film dimensions, thickness, thickness variation rate, and volume-specific low efficiency There was no change in the physical property values such as, and the distortion caused by the thinning treatment was alleviated.

Example 15
The conductive film obtained in Example 1 was annealed at 115 ° C. for 1 hour and then allowed to stand at 140 ° C. for 3 minutes. In the conductive film flow direction (MD) and width direction (TD), respectively. The shrinkage of 12% and the elongation of 3% were observed, and the strain generated by the thinning treatment tended to be not yet relaxed.

  The thin conductive film of the present invention is used in various fields where conductivity and solvent resistance are required, and is used in contact with a solvent, for example, a semiconductor wafer storage container, a gasoline tank, an electronic / electrical device, and a semiconductor manufacturing It can be used as a material for flooring and wall materials in factories and various battery members. Moreover, it is useful for energy device uses, such as an electrode material, from the outstanding electroconductivity. Among these, it is particularly useful as a current collector for a secondary battery such as a lithium ion battery because it is thin and requires high conductivity.

Claims (11)

A conductive film comprising a crystalline resin and a carbon-based conductive filler, wherein the conductive film satisfies the following characteristics (1) to (4).
(1) The ratio (weight ratio) between the crystalline resin and the carbon-based conductive filler is the former / the latter = 90/10 to 55/45 (2) The film thickness is 5 to 120 μm (3) Volume The specific resistivity is 0.1 to 1500 Ω · cm. (4) The absolute value of the weight change rate after being immersed in tetrahydrofuran at 25 ° C. for 24 hours is 10% by weight or less.   The conductive film according to claim 1, wherein the carbon-based conductive filler is conductive carbon black.   The conductive film according to claim 1 or 2, wherein the crystalline resin is a polypropylene resin and / or a polyamide resin.   The conductive film according to claim 3, wherein the polypropylene-based resin has a specific gravity of 0.95 or less and contains 90 mol% or more of propylene units.   The conductive film according to claim 3, wherein the polyamide resin is an aliphatic polyamide resin having a specific gravity of 1.05 or less.   The conductive film according to claim 1, wherein the crystalline resin is a polypropylene resin, and the specific gravity of the film is 0.95 to 1.20.   The conductive film according to claim 1, which has a volume resistance value of 0.001 to 5Ω.   The conductive film according to claim 1, wherein a thickness variation ratio (maximum thickness / minimum thickness) is 1.5 or less.   The conductive film according to any one of claims 1 to 8, which contains substantially no elastomer.   Extrusion molding of a crystalline resin and a carbon-based conductive filler to form a sheet having a thickness of 120 to 500 μm, and when the melting point of the crystalline resin is mp, (mp-40) ° C. to (mp− 5) The manufacturing method of the electroconductive film of Claim 1 including the extending | stretching or rolling process of extending | stretching or rolling, heating the obtained sheet | seat at the temperature of degreeC.   The manufacturing method according to claim 10, wherein in the stretching or rolling step, the thickness after treatment is stretched or rolled to 1/2 to 1/5 times the thickness before treatment.