JP2012140002A - Porous film and power accumulating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a porous film which prevents inorganic particles in a porous layer from dropping, has high air permeability, and exhibits superior battery characteristics when used as a separator.SOLUTION: At least one surface of the porous resin film has a porous layer containing inorganic particles When the width of the porous layer containing inorganic particles is W1 and the width of the porous resin film is W2, W1<W2 is satisfied. The porous film has a part not having the porous layer containing inorganic particles which is located at one side or both sides in its width direction and has air permeability in the part that has the porous layer containing inorganic particles.

Description

  The present invention relates to a porous film. More specifically, the present invention relates to a porous film that can be suitably used for a separator used in a non-aqueous solvent battery or a capacitor. Particularly, when the inorganic film contained in the porous film is less dropped, the air permeability is high, and used as a separator. The present invention relates to a porous film exhibiting excellent battery characteristics.

  A non-aqueous solvent battery such as a lithium battery or a lithium ion battery has a problem that the electrolytic solution used is an organic solvent and is inferior in safety against heat generation of the battery as compared with an aqueous solvent of an aqueous battery. Therefore, conventionally, in order to improve the safety of non-aqueous solvent batteries, particularly lithium ion batteries having a large energy density, a separator using a microporous porous film of an olefin-based material mainly composed of polyethylene has been used. Polyethylene is mainly used because polyethylene can be used in an organic solvent, and when the battery abnormally generates heat due to a short circuit, etc., the polyethylene melts at an appropriate temperature (around 130 ° C) and the porous structure is blocked. This is because safety can be ensured by doing (shutdown).

  However, in recent years, large batteries such as hybrid vehicle (HEV) batteries and tool batteries have been increased in output and rapidly rise to temperatures higher than 130 ° C. The function of shutting down is not always required, and heat resistance is required. Further, in order to increase the output of the battery and to use it for a lithium ion capacitor, it is necessary to reduce the resistance of the separator alone, so that a high porosity and high air permeability of the separator are required. Further, it is important for HEV batteries to be able to guarantee a long life of 10 years and more stringent safety. Moreover, in a battery having high energy and high power, such as a battery for HEV, the amount of heat generated at the time of thermal runaway is large, and if the temperature continues to rise even when the shutdown temperature is exceeded, the film breaks due to the thermal contraction of the separator. There is a problem that both poles are short-circuited and cause further heat generation.

  Furthermore, in providing separators for various battery applications, there are examples in which high functionality is achieved by providing various porous layers on the porous resin film. For example, by providing a porous layer containing inorganic particles or a porous layer made of organic particles having a high softening point, high heat resistance is imparted, and a porous layer made of organic particles having a melting point of 100 to 140 ° C. is given. Thus, shutdown property can be imparted.

  A separator using polyethylene has a problem in that it is inferior in heat resistance such as heat generation due to a short circuit between the electrodes due to a tendency to shrink at a temperature of 120 ° C. or less for a battery high temperature test. Therefore, a separator using a polypropylene porous film having higher heat resistance than polyethylene has been proposed (for example, Patent Document 1). However, there may be a problem that it does not have a shutdown property in a temperature range of 130 to 140 ° C. and that the porous film opens at a high temperature of 200 ° C. or higher.

  Moreover, the proposal which uses the polypropylene nonwoven fabric excellent in heat resistance and suitable for high output uses like a large sized battery for a separator is also made (for example, patent document 2). However, in this case, since the base material is a non-woven fabric made of fibers, it has a large average pore diameter of about several μm, so that a fine short circuit is likely to occur, and a long life like a battery for HEVs. And it was not enough for even more stringent safety. Furthermore, as long as the nonwoven fabric is used, the film thickness becomes large and the volume increase is inevitable, and there is also a problem that goes against the trend of the era of battery miniaturization and weight reduction.

  In addition, a composite porous membrane filled with resin particle aggregates from the surface to the inside of a porous substrate has been proposed (for example, Patent Document 3). However, in this case, fine particles may be aggregated, and due to the aggregation of the fine particles, defects may occur or the particles may fall off. Not enough for longevity and even more stringent safety.

  In addition, proposals have been made to apply an organic particle or inorganic particle-containing layer having a high softening point to the surface of a porous substrate (for example, Patent Document 4). In addition, a proposal has been made to apply a polyimide, aramid and polyamideimide layer in which inorganic particles are dispersed on the surface of a polyethylene porous film (for example, Patent Document 5). In addition, a proposal has been made to apply an aramid layer on the surface of a polyethylene porous film, and further apply polypropylene and polyethylene particles (for example, Patent Document 6). In these cases, since the particle-containing layer is slit at the time of slitting, the particles may drop off, and the particles may drop off at the time of battery assembly, which may affect the battery characteristics.

  Moreover, the proposal which apply | coats an inorganic particle layer partially on the surface of a porous base material is made | formed (for example, patent document 7). In this case, there is a place where the inorganic particle layer does not exist on the surface in contact with the electrode, the heat resistance is only partially exhibited, and the safety is not sufficient.

Japanese Patent Laid-Open No. 01-103634 JP-A-60-52 JP 2006-286111 A JP 2007-273443 A JP 2006-164873 A JP 2002-151044 A JP 2006-12788 A

  An object of the present invention is to solve the above-described problems. That is, an object of the present invention is to provide a porous film in which the inorganic particles in the porous layer are less dropped, the gas permeability is high, the processability is excellent, and the battery characteristics are excellent when used as a separator.

  The present invention for achieving the above object has a porous layer containing inorganic particles on at least one surface of a porous resin film, the width of the porous layer containing inorganic particles is Wh, and the width of the porous resin film is When the thickness is W2, Wh <W2 is satisfied, a portion substantially not having a porous layer containing inorganic particles is present in one or both of the width direction, and a portion having a porous layer containing inorganic particles is air permeable. It is a porous film provided with.

  The porous film of the present invention can be provided as a porous film that is excellent in heat resistance and processability, has high air permeability, and exhibits excellent battery characteristics when used as a separator.

It is a schematic sectional drawing of the porous film which concerns on one embodiment of this invention. It is the schematic of the porous film roll which concerns on one embodiment of this invention.

  The porous resin film used in the present invention is a film having a large number of fine through holes that penetrate both surfaces of the film and have air permeability. The same applies to the porous film. The resin constituting the porous resin film may be any of polyolefin resin, polycarbonate, polyamide, polyimide, polyamideimide, aromatic polyamide, fluorine resin, etc., but heat resistance, moldability, production cost reduction, chemical resistance From the viewpoints of properties, oxidation resistance and reduction resistance, polyolefin resins are desirable.

  Examples of the monomer component constituting the polyolefin resin include ethylene, propylene, 1-butene, 1-pentene, 3-methylpentene-1, 3-methyl-1-butene, 1-hexene and 4-methyl. -1-pentene, 5-ethyl-1-hexene, 1-heptene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-heptadecene, 1-octadecene, 1-eicosene, vinyl And cyclohexene, styrene, allylbenzene, cyclopentene, norbornene, 5-methyl-2-norbornene, and the like. These homopolymers and at least two kinds of copolymers selected from the above monomer components, Examples include, but are not limited to, blends of copolymers and copolymers. In addition to the above monomer components, for example, vinyl alcohol, maleic anhydride or the like may be copolymerized or graft polymerized, but is not limited thereto. As the lithium ion battery separator, polyethylene using ethylene as a monomer component and / or polypropylene using propylene as a monomer component is preferable, and propylene is preferably used from the viewpoint of heat resistance, air permeability, porosity, and the like. Polypropylene used as a monomer component is preferred.

  As a method for forming the through hole in the porous resin film, either a wet method or a dry method may be used. Specifically, the wet method is a method using a polyolefin resin as a matrix resin, adding an extract to be extracted after forming into a sheet, mixing, and extracting only the additive using a good solvent of the extract, This is a method for generating voids in a matrix resin, and various proposals have been made. On the other hand, as a dry method, for example, by adopting low-temperature extrusion and a high draft ratio at the time of melt extrusion, the lamella structure in the film before stretching formed into a sheet is controlled, and this is uniaxially stretched so that at the lamella interface A method (so-called lamellar stretching method) in which cleavage is generated to form voids has been proposed. Further, as a dry method, a large amount of incompatible resin is added as inorganic particles or polypropylene, which is a matrix resin, and a sheet is formed and stretched to cause cleavage at the interface between the particles and the polypropylene resin. A method of forming has also been proposed. Furthermore, there is a so-called β crystal method in which voids are formed in the film by utilizing the crystal density difference and crystal transition between α type crystal (α crystal) and β type crystal (β crystal), which are polymorphs of polypropylene. Many proposals have been made for the so-called method.

  The porous film of the present invention is provided with a porous layer containing inorganic particles on at least one surface of the above-described porous resin film. By containing inorganic particles in the porous layer, heat resistance of 200 ° C. or higher can be imparted to the porous film. The types of inorganic particles include, for example, oxide ceramics such as alumina, silica, titania, zirconia, magnesia, ceria, yttria, zinc oxide and iron oxide, and nitride ceramics such as silicon nitride, titanium nitride and boron nitride, and silicon. Carbide, calcium carbonate, aluminum sulfate, potassium titanate, talc, kaolin clay, kaolinite, halloysite, pyrophyllite, montmorillonite, sericite, mica, amicite, bentonite, asbestos, zeolite, calcium silicate, magnesium silicate, Examples include ceramics such as diatomaceous earth and silica sand, ceramics such as glass beads and glass fibers, etc. From the viewpoint of electrochemical stability, it is preferable to use oxide-based ceramics, which are used alone. Good It may be mixed and used more.

  Furthermore, from the viewpoint of stability in the lithium ion battery, inorganic particles having a water content of 1% by mass or less are preferable. More preferably, the water content is preferably 0.5% by mass or less. In the present invention, the inorganic particles having a water content of 1% by mass or less are preferably inorganic particles having a dense structure having no pores inside. For example, alumina, silica produced by dry method, oxide ceramics such as zirconia produced by dry method, nitride ceramics such as silicon nitride, titanium nitride, boron nitride, silicon carbide, calcium carbonate, aluminum sulfate silica Examples include ceramics such as sand, ceramics such as glass fiber, etc. From the viewpoint of electrochemical stability, it is preferable to use alumina, silica produced by a dry method, zirconia produced by a dry method, May be used alone, or a plurality may be used in combination. Alumina, silica produced by a dry method, and zirconia produced by a dry method may be subjected to a silane coupling treatment.

  The average particle diameter of the inorganic particles is preferably 0.1 to 5 μm. If the average particle size is less than 0.1 μm, pores existing in the porous resin film may be clogged, resulting in poor air permeability. On the other hand, when the thickness exceeds 5 μm, coarse protrusions are formed, the surface property is deteriorated, and the assembling property of the battery such as winding deviation may be deteriorated. More preferably, it is 0.1-3 micrometers from a viewpoint of the assembly property of a battery. If the average particle diameter of the inorganic particles is a spherical particle, the average particle diameter is the average particle diameter. In the case of particles other than the spherical particles such as flat particles, the average of the short-side diameter and the long-side diameter is defined as the average particle diameter.

  When the porous layer is formed by coating, the content of the inorganic particles is preferably 10 to 40% by mass in the raw material coating. When the content is less than 10% by mass, heat resistance may not be imparted to the entire porous film. When the content is more than 40% by mass, the inorganic particles become excessive, and the inorganic particles fall off. Agglomeration may occur, a slight short-circuit is likely to occur, and it may not be sufficient for a long life as in a HEV battery and more severe safety. Moreover, it is preferable that content of the inorganic particle in a porous layer is 30-80 mass%. When the content is less than 30% by mass, heat resistance may not be imparted to the entire porous film. When the content is more than 80% by mass, the inorganic particles become excessive, and the inorganic particles fall off. Agglomeration may occur, a slight short-circuit is likely to occur, and it may not be sufficient for a long life as in a HEV battery and more severe safety.

  In the present invention, it is also preferable to add an adhesive to the porous layer containing inorganic particles in order to improve the adhesion between the porous resin film and the porous layer. For example, various epoxy resins, epoxy group-containing (meth) acrylates such as glycidyl (meth) acrylate, epoxy group-containing organosilicon compounds such as Y-glycidoxypropylmethyldiethoxysilane, polyvinylidene chloride, polyvinylidene fluoride, styrene Butadiene rubber, cellulose and / or cellulose salt, acrylic resin, polyvinyl butyral, polyethylene, polyvinyl alcohol, polytetrafluoroethylene, polyvinyl pyrrolidone, polyimide, polyamide, polysulfide, polyvinyl methyl ether, polyethylene oxide, polypropylene oxide, melamine resin, polyvinyl Examples thereof include resins such as pyridine and higher alcohols and salts thereof.

  Since the porous film of the present invention is suitably used for a separator of an electricity storage device, the air permeability resistance is in the range of 50 to 600 seconds / 100 ml from the viewpoint of reducing the internal resistance of the battery and further improving the output density. preferable. If the air permeation resistance is less than 50 seconds / 100 ml, the porosity may increase or the pore diameter may become too large, and the strength may not be sufficiently maintained. In addition, when used as a separator, the battery life may be shortened. On the other hand, if it exceeds 600 seconds / 100 ml, the characteristics when used as a separator will be insufficient. More preferably, it is 50-400 seconds / 100ml, More preferably, it is 50-300 seconds / 100ml from a viewpoint of a separator characteristic.

  Here, the air permeation resistance is an index of the air permeability of the sheet and is shown in JIS P 8117 (1998). The air resistance of the sheet can be controlled not only by controlling the air resistance of the porous resin film but also by changing the composition of the inorganic particles and the adhesive in the porous layer. When the mixing ratio of the inorganic particles and the adhesive is increased, the air permeability resistance is decreased when the mixing ratio of the inorganic particles is increased, and when the mixing ratio of the adhesive is increased, the air resistance is increased.

  The porous film of the present invention has a relationship in which the width length Wh of the porous layer containing inorganic particles and the width length W2 of the porous resin film serving as a substrate are Wh <W2, and the porous layer containing inorganic particles It is important that a substantially non-existing portion exists in one or both of the width directions. The portion having substantially no porous layer containing inorganic particles refers to a portion that is 1/3 or less of the average thickness of the porous layer containing inorganic particles, and preferably there is no porous layer containing inorganic particles. Say part. When a porous layer containing inorganic particles is arranged on the entire surface of the porous resin film, when used as a battery separator, the particles fall off from the cross section of the porous layer due to expansion and contraction of the electrode during charge and discharge, and long-term stability is improved. In the case of a cylindrical battery or prismatic battery, the winding body may be used when welding the current collecting tab to the winding body composed of the positive electrode, the negative electrode, and the separator, or when welding the outer can to the current collector. The separator in the width direction of the separator may be crushed, and particles may fall off from the crushed portion, thereby reducing long-term reliability. In the case of a laminated or single-layer laminated battery, when performing a three-way seal or a seal after pouring, the margin in the width direction of the separator in the laminate composed of the positive electrode, the negative electrode, and the separator is crushed, and the crushed portion In some cases, the particles fall off and the long-term reliability decreases, or the inorganic particles fall off during slitting of the separator, or the life of the slit blades decreases. From the viewpoint of battery processability and battery characteristics, 1 mm <(W2-Wh) <10 mm is preferable.

  The porous film of the present invention has a width of a portion not having one porous layer when a portion not having a porous layer containing inorganic particles applied to at least one surface of the porous resin film is present in both width directions. The length Δ1 and the other width length Δ2 are preferably | Δ1−Δ2 | <0.5 mm, 0.5 mm ≦ Δ1 ≦ 5 mm, and 0.5 mm ≦ Δ2 ≦ 5 mm. When | Δ1-Δ2 | is 0.5 mm or more, a portion that does not have any one porous layer enters the electrode facing surface, and may not exhibit sufficient heat resistance. From the viewpoint of battery processability and battery characteristics, | Δ1−Δ2 | <0.1 mm is preferable, and Δ1 = Δ2 is more preferable. In addition, when both Δ1 and Δ2 are less than 0.5 mm, the particles fall off during the slit processing, and the passability of the slit process decreases, or the particles fall off from the slit cross section of the porous layer after the slit. However, when used as a battery separator, the electrode edge may hit the end of the porous layer and the particles may fall off, which may reduce long-term stability. On the other hand, when both Δ1 and Δ2 exceed 5 mm, when the battery is designed so that the porous layer functions over the entire surface of the active material layer when used as a battery separator, the margin between the electrode and the separator increases and the battery capacity decreases. There is a case. From the viewpoint of battery workability and battery characteristics, 1 mm ≦ Δ1 ≦ 5 mm and 1 mm ≦ Δ2 ≦ 5 mm are preferable, and 1 mm ≦ Δ1 ≦ 4 mm and 1 mm ≦ Δ2 ≦ 4 mm are particularly preferable. From the viewpoint of heat resistance, 2 mm ≦ Δ1 ≦ 4 mm and 2 mm ≦ Δ2 ≦ 4 mm are more preferable.

  The porous film of the present invention has a longitudinal direction of a porous layer containing inorganic particles when a portion not having a porous layer containing inorganic particles coated on at least one side of the porous resin film is present in one or both of the width directions. It is preferable that the cross-sectional shape of the edge portion has a curve, a corner, or a chamfered shape. This shape is exemplified by the shape indicated by reference numeral 10 in FIG. When the edge in the longitudinal direction has a corner or is a straight line, when producing a wound body with an electrode or a laminate with an electrode, specifically, a porous film passes through a film path, or with an electrode. When winding or laminating, the corners and sharp edges of the longitudinal edge of the porous layer are rubbed with the film pass rolls and electrodes, so that inorganic particles fall off and the battery assembly process passability decreases. In some cases, the dropped inorganic particles enter the battery and the long-term reliability is lowered. When the entire surface is coated and slits are made to have a predetermined width, by inserting a slit blade on the coating surface, a corner is formed at the edge portion in the longitudinal direction or a straight line is formed. Therefore, in order to make the cross-section of the edge part in the longitudinal direction into the above-mentioned preferable shape, by intermittently applying a porous layer containing inorganic particles in the width direction of the porous resin film, Thus, the coating material flows naturally to the uncoated part, and the above-mentioned preferable shape can be obtained. Moreover, in the case of intermittent coating, since a slit blade is not put on the coating surface, it is possible to maintain the preferable shape even after slitting.

  Also, a porous layer containing inorganic particles is present on both sides of the porous resin film, the width of the porous layer containing inorganic particles on the positive electrode side of the porous film is W3, and the porous layer containing inorganic particles on the negative electrode side When the width is W1, the width of the positive active material layer is W (positive electrode), and the width of the negative active material layer is W (negative electrode), 0 ≦ W1−W3 ≦ 20 mm. In addition, it is also preferable to make an electricity storage device using the above porous film as an electricity storage device separator so that W3 ≧ W (positive electrode) and W1 ≧ W (negative electrode). In the case of W3 <W (positive electrode), the whole positive electrode active material layer may not have sufficient heat resistance. In the case of W1 <W (negative electrode), the entire negative electrode active material layer may not have sufficient heat resistance. When W1-W3 <0 mm, the negative electrode width length is often larger than the positive electrode width length in a general battery design, and the entire negative electrode active material layer may not have sufficient heat resistance. When W1-W3> 20 mm, the entire positive electrode active material layer may not have sufficient heat resistance. From the viewpoint of battery characteristics and heat resistance, 0 ≦ W1−W3 ≦ 10 mm is preferable. Note that Δ1 and Δ2 when a porous layer containing inorganic particles is present on both sides of the porous resin film are Δ1 and Δ2 of the porous layer facing the active material layer of the negative electrode.

  Here, an example of the porous film and the electricity storage device separator of the present invention described above is shown as follows.

  FIG. 1 is a schematic cross-sectional view of an electricity storage device separator in which a positive electrode and a negative electrode are provided on a porous film according to an embodiment of the present invention. The porous resin film 1 is provided with a porous layer 2 on one surface and a porous layer 3 on the other surface to constitute a porous film 4. Further, a negative electrode 5 made of a negative electrode active material layer is provided on the surface of the porous layer 2, and a positive electrode 6 made of a positive electrode active material layer is provided on the surface of the porous layer 3, thereby constituting an electricity storage device separator 7 as a whole. ing. In FIG. 1, the width length W2 of the porous resin film 1 and the width length W1 of one porous layer 2 have a relationship of W1 <W2. The relationship between W2 and the width length W3 of the other porous layer 3 is also the same. The relationship between the width length W (negative electrode) and W1 of the negative electrode and the relationship between the width length W (positive electrode) and W3 of the positive electrode are W3> W (positive electrode) and W1> W (negative electrode) in FIG. It has become. Of course, these relationships may be W3 ≧ W (positive electrode) and W1 ≧ W (negative electrode) as described above.

  In order to obtain the above-described porous film of the present invention, a porous layer containing inorganic particles is intermittently arranged in the width direction of the porous resin film (each of the porous layers is continuously provided in the longitudinal direction). It is preferable to first produce a film and then slit the film in the longitudinal direction at the portion where the porous layer is not disposed.

  If slitting is performed in a state where a porous layer containing inorganic particles is disposed on the entire surface of the porous resin film, the particles may fall off during slitting, and the processability of the slit process may deteriorate, or after slitting In some cases, the particles fall off from the cross section of the porous layer, thereby deteriorating the processability of the battery assembly process. If a porous layer containing inorganic particles is disposed intermittently in the width direction of the porous resin film, the particles can be prevented from falling off by slitting at a portion where the porous layer is not disposed.

  This will be specifically described with reference to the drawings.

  FIG. 2 is a schematic view of the porous film roll 8 showing a state in which porous layers containing inorganic particles are intermittently disposed on both surfaces of the porous resin film 1. However, the porous layer is shown only on one side. In FIG. 2, the porous film roll has a porous layer intermittently provided on both sides of the rolled porous resin film, and a portion where the porous layer is not provided (unlaminated portion 9) exists between the porous layers. In addition, a porous film as shown in FIG. 1 can be obtained by slitting each unlaminated portion.

  The width of the non-laminated portion of the porous film roll described above is preferably 0.2 to 10 mm. When the non-laminated portion is less than 0.2 mm, it is difficult to slit only the non-laminated portion at the time of slitting, and the porous layer portion is slit and the particles fall off, thereby allowing the slit process to pass. May deteriorate, and the function of the porous layer may not be exhibited over the entire surface of the electrode active material. On the other hand, when the width of the non-laminated portion is wider than 10 mm, the non-laminated portion enters the electrode facing surface, and it may not be possible to provide sufficient heat resistance. The width of the non-laminated portion is preferably 5 to 10 mm from the viewpoint of process passability.

  In order to produce the porous film roll as described above, it is most convenient to intermittently apply in the width direction when applying the coating liquid constituting the porous layer on the porous resin film. Intermittent coating in the width direction can be achieved by, for example, intermittent coating in the width direction using a die coater with the discharge port portion corresponding to the unstacked portion masked with tape or the like. is there.

The porous resin film of the above, when the thickness of the case plus the load of 0.06 kg / cm ² and D1, and the thickness when a load is applied in 6 kg / cm ² and D2, 75% ≦ D2 / D1 Is preferably satisfied. When D2 / D1 <75%, the holes present in the porous resin film may be crushed in the slitting process, or the holes present in the porous resin film may be crushed when wound as a roll. From the viewpoint of slit processability and battery characteristics, 75% ≦ D2 / D1 ≦ 90% is more preferable. When D2 / D1> 90%, it may be difficult to follow the expansion and contraction of the positive and negative electrodes accompanying the charge / discharge reaction, and the battery characteristics may be deteriorated.

  The heat resistance of the porous film is preferably such that the film shape is maintained under the conditions of a heating temperature of 200 ° C., a heating time of 10 seconds, and a load of 0.1 MPa, and the width dimension change is 20% or less. When the shape of the film is not maintained under the main heating conditions, or when the width dimension change is larger than 20%, the battery may be short-circuited when abnormal heat is generated. From the viewpoint of preventing a short circuit during abnormal heat generation, it is more preferably less than 12%. Further, in order to maintain the shape of the film under the present heating conditions and to change the width dimension to 20% or less, it has the shape of the porous film of the present application in which a porous layer is provided on the porous resin film, and Δ1 and Δ2 are the above-described values. The conditions are preferable.

  As a method for providing the porous layer by coating, any method generally used may be used. For example, a suspension prepared by dispersing an oxirane ring-containing compound in ion-exchanged water or the like is used as a reverse coating method, a bar coating method, or the like. What is necessary is just to apply | coat on a porous resin film with coating methods, such as a coating method, a gravure coating method, a rod coating method, a die coating method, and a spray coating method, and to make a coating layer (porous layer). Further, when preparing the suspension, a dispersant or the like may be appropriately added in order to prevent uneven distribution of particles in the coating layer. In particular, the die coating method is preferable from the viewpoint that the intermittent coating can be easily performed.

  As drying conditions after coating, the drying temperature is preferably 80 to 120 ° C. and the drying time is preferably 1 to 10 minutes. Moreover, when apply | coating intermittently and making it dry, it is preferable to arrange | position the hose which circulated cooling water on the upper and lower sides of a non-laminated part, and to dry an application part, cooling a non-laminated part. When the non-laminated portion is dried without cooling (especially when heated and dried), shrinkage of the non-laminated portion and a decrease in air permeability may occur due to differences in drying behavior. When the drying temperature is less than 80 ° C., the reaction of the binder becomes insufficient, the adhesiveness is insufficient, and the porous layer becomes undried, and the porous layer may contain a large amount of moisture. When the temperature is higher than 120 ° C., the porous resin film may shrink and the air permeability of the porous film may deteriorate. When the drying time is less than 1 minute, the reaction of the binder becomes insufficient, the adhesiveness becomes insufficient, the porous layer becomes undried, and a large amount of moisture may be contained in the porous layer. When the length is longer than 5 minutes, the porous resin film may shrink and the air permeability of the porous film may deteriorate. More preferably, from the viewpoint of binder reaction and air permeability of the porous film, the drying temperature is preferably 90 to 110 ° C., and the drying time is preferably 2 to 5 minutes.

  Below, an example of the manufacturing method of the porous resin film and porous film of this invention is demonstrated concretely. In addition, the manufacturing method of the film of this invention is not limited to this.

  First, as the polypropylene resin constituting the porous resin film, 95 to 100 parts by mass of a commercially available homopolypropylene resin having an MFR of 5 to 20 g / 10 minutes, and 1 part by mass of a high melt tension polypropylene resin having the same MFR of 2 to 5 g / 10 minutes. , N′-dicyclohexyl-2,6-naphthalenedicarboxamide 0.05 to 0.3 parts by mass are mixed, and a raw material mixed in advance at a predetermined ratio using a twin screw extruder is prepared.

  Next, this mixed raw material is supplied to a single screw extruder, and melt extrusion is performed at 200 to 230 ° C. And after removing a foreign material, a modified polymer, etc. with the filter installed in the middle of the polymer pipe | tube, it discharges on a cast drum from T-die, and a lamination | stacking unstretched sheet is obtained. At this time, the surface temperature of the cast drum is preferably 105 to 130 ° C. from the viewpoint of controlling the β-crystal forming ability of the cast film to be high. At this time, in particular, since the forming of the end portion of the sheet affects the subsequent stretchability, it is preferable that the end portion is sprayed with spot air to be in close contact with the drum. Further, air may be blown over the entire surface using an air knife as necessary based on the state of close contact of the entire sheet on the drum.

  Next, the obtained unstretched sheet is biaxially oriented to form pores in the film. As a biaxial orientation method, the film is stretched in the longitudinal direction of the film and then stretched in the width direction, or the sequential biaxial stretching method in which the film is stretched in the width direction and then stretched in the longitudinal direction. The simultaneous biaxial stretching method can be used, but it is preferable to adopt the sequential biaxial stretching method in that it is easy to obtain a highly air-permeable film, and in particular, it is possible to stretch in the width direction after stretching in the longitudinal direction. preferable.

  As specific stretching conditions, first, the temperature is controlled so that the unstretched sheet is stretched in the longitudinal direction. As a temperature control method, a method using a temperature-controlled rotating roll, a method using a hot air oven, or the like can be adopted. The stretching temperature in the longitudinal direction is preferably 90 to 130 ° C, more preferably 100 to 125 ° C. As a draw ratio, it is 3-6 times, More preferably, it is 3-5 times.

  After stretching in the longitudinal direction, the film end is held by a stenter-type stretching machine and introduced. And preferably, it heats to 130-160 degreeC, and performs 6-12 times in the width direction, More preferably, it extends 6-10 times. The transverse stretching speed at this time is preferably 100 to 5,000% / min, more preferably 1,000 to 4,000% / min. Subsequently, heat setting is performed in the stenter as it is, and the temperature is preferably from the transverse stretching temperature to 160 ° C. Further, the heat setting may be performed while relaxing in the longitudinal direction and / or the width direction of the film, and in particular, the relaxation rate in the width direction is preferably 5 to 20% from the viewpoint of thermal dimensional stability.

  The porous resin film produced by the above production method is subjected to corona treatment as needed, more preferably corona treatment in a carbon dioxide atmosphere, and 15 parts by mass of silica particles produced by a dry method as inorganic particles, and containing an oxirane ring A suspension obtained by mixing 2.0 parts by mass of a compound, 1.0 part by mass of cellulose and / or cellulose salt, and 82 parts by mass of ion-exchanged water, and stirring the suspension for 4 hours has a wet thickness of 3 by a die coating method. The film is intermittently applied on the film so that the non-laminated portion is 5 mm, and dried at 100 ° C. for 2 minutes to form a porous layer having a dry thickness of 1 to 4 μm.

  In addition, when performing a corona treatment in the above-mentioned carbon dioxide atmosphere, the corona treatment is performed on the porous resin film produced by the above method in a mixed gas atmosphere of carbon dioxide 40-60 parts by mass and nitrogen gas 40-60 parts by mass. To introduce a carboxyl group.

  Although an example of a manufacturing method was described as mentioned above, of course, this invention is not limited to these.

  Since the porous film of the present invention can hold an organic solvent, it can be used as a separator for an electricity storage device that uses an organic solvent as an electrolytic solution. Moreover, since the porous film of this invention has high air permeability, resistance as a separator becomes low and can be preferably used for a lithium ion battery and a lithium ion capacitor among the said electrical storage devices.

  Examples of the electricity storage device using the porous film of the present invention include a non-aqueous electrolyte secondary battery using an organic solvent and an electric double layer capacitor. In particular, a lithium ion battery is suitable from the balance of battery capacity and output density. Since it can be used repeatedly by charging and discharging, it can be used for power supplies of IT equipment, daily life equipment, hybrid cars, electric cars and the like. In particular, a lithium ion battery is suitable for the above applications because of the balance between battery capacity and output density. Since the electricity storage device using the porous film of the present invention has a high porosity and high air permeability, it can be suitably used for a power source such as a hybrid vehicle and an electric vehicle.

  Hereinafter, the present invention will be described in detail by way of examples. The characteristics were measured and evaluated by the following methods.

(1) Process passability of slit process Using a slitter “MODEL433B” manufactured by Gordo Kiko Co., Ltd., a porous film was slit with a width of 60 mm and a length of 100 m for each of the examples and comparative examples. The conveying speed was 25 m / min, the unwinding tension was 18 N / 110 mm, the winding tension was 20 N, and the slit blade was a circular shear blade with a blade tip thickness of 0.5 mm for intermittent coating. The center part of the width direction of the non-laminated part of the porous layer was slit. In addition, the porous layer part was slit about the porous film which has not occurred intermittent coating.

  The particles dropped out and the particles adhered to the shear blade and pass roll were evaluated as NG.

○: No NG in 100 m from the beginning of winding Δ: NG generated from 50 m to less than 100 m from the beginning of winding ×: NG generated in less than 50 m from the beginning of winding (2) Air resistance (Gurley air permeability)
Based on B method of JIS P 8117 (1998), measurement was performed at 23 ° C. and 65% RH (unit: second / 100 ml). The same measurement was performed five times at different locations on the porous layer portion of the porous film of each Example / Comparative Example, and the average value of the obtained Gurley air permeability was taken as the Gurley air permeability of the sample. At this time, those having an average value of Gurley air permeability exceeding 7,200 seconds / 100 ml were regarded as substantially having no air permeability, and were set to infinity (∞) seconds / 100 ml.

(3) Thickness D1 (μm) is a value measured by attaching a 10 mmφ flat standard gauge head to a dial gauge (Mitoyo Seisakusho No. 2109-10) and applying a load to 0.06 kg / cm ^2. A value measured by attaching a 1 mmφ flat standard measuring probe and applying a load so as to be 6 kg / cm ² was defined as D2 (μm).

  The thickness was measured 30 seconds after applying the load. In this measurement, the measurement position was changed, 10 points were measured, and the average value was used.

(4) Heat resistance test A sample film was cut into a rectangle with a width direction of 60 mm and a longitudinal direction of 30 mm, and using a heat seal tester manufactured by Tester Sangyo Co., Ltd., a heating temperature of 200 ° C., a heating time of 10 seconds, and a load of 0.1 MPa. The area of 60 mm in the width direction and 10 mm in the longitudinal direction was heated.

  The film which performed the said process was evaluated on the following references | standards.

  ○: The shape of the film is maintained. No hole formation by visual inspection. The width change is less than 12%.

  Δ: The shape of the film is maintained. Although no hole is formed visually, the width dimension change is 12 to 20%.

  X: The flatness of the film is poor and there is a hole formed by melting in the uncoated part, or the width dimension change exceeds 20%.

(5) Battery assembly property Using a positive electrode with a lithium cobalt oxide (LiCoO ₂ ) thickness of 40 μm manufactured by Hosen Co., Ltd., sampled into a rectangle of longitudinal direction: 300 mm × width direction 52 mm. ) Using a graphite negative electrode having a thickness of 50 μm, sampled into a rectangle of 300 mm × width direction: 55 mm in the longitudinal direction, and then the porous film of each of the examples and comparative examples: 310 mm × width direction: Sampled into a 60 mm rectangle. In addition, about the porous film coated intermittently, the center part of the non-laminated part was cut.

  Using a manual winding machine UP3015 manufactured by Ube Industries Co., Ltd., the positive electrode and the negative electrode are overlapped at the center in the width direction of the porous film through the porous film, and the height is 60 mm. A cylindrical electrode body was obtained. The tension was controlled using a cylindrical type, a spring having a spring pressure of 100 g / cm, and manually wound so that the speed was 1 m / min.

The cylindrical electrode body was pushed from both sides in the height direction with a load of 50 g / cm ² , and the dropout of the particles and the state of the porous layer were decomposed and evaluated.

  Evaluation was made according to the following criteria.

○: No dropout of particles and crack of porous layer Δ: No dropout of particles, but crack of porous layer ×: Dropping of particles and crack of porous layer

(6) Cross-sectional observation of edge portion in longitudinal direction The porous film of each Example / Comparative Example is microtomed to form a cross section, and the longitudinal edge portion of the porous layer in the cross section is scanned by JEOL Ltd. Using a scanning electron microscope (SEM) JSM-6700F, the magnification was observed 500 times, a cross-sectional photograph was taken, and the state was confirmed.

  The shape of the edge portion was evaluated according to the following criteria.

○: The cross section of the edge portion in the longitudinal direction is a curved line, rounded, or chamfered. ×: The cross section of the edge portion in the longitudinal direction is straight or has a corner.

  The state of the inorganic particles in the edge portion was evaluated according to the following criteria.

○: There is no evidence that particles have fallen off.

    Hereinafter, the present invention will be described more specifically based on examples. Of course, the present invention is not limited to these.

Example 1
First, the following composition was compounded with a twin-screw extruder to prepare a resin A chip.

<Polypropylene resin A>
99,75 parts by mass of homopolypropylene FLX80E4 (hereinafter referred to as PP-1) manufactured by Sumitomo Chemical Co., Ltd., N, N′-dicyclohexyl-2,6-naphthalenedicarboxamide, which is a β crystal nucleating agent (Shin Nippon Rika) Co., Ltd., Nu-100, hereinafter simply referred to as a β crystal nucleating agent) is added to 0.25 parts by mass, and antioxidants such as IRGANOX 1010 and IRGAFOS 168 manufactured by Ciba Specialty Chemicals are 0.15,. The compound was compounded with a twin screw extruder at 1 part by mass (hereinafter simply referred to as an acid inhibitor and used at a mass ratio of 3: 2 unless otherwise specified).

  Chips made of polypropylene resin A are supplied to a single screw extruder, melt extruded at 225 ° C, removed foreign matter with a 25μm cut sintered filter, and then discharged onto a cast drum whose surface temperature is controlled at 120 ° C with a T-die. Then, the film was cast so as to be indirectly on the drum for 15 seconds, and was blown into close contact with air using an air knife from the non-drum surface side of the film to form an unstretched sheet.

  The obtained unstretched sheet was preheated through a roll group maintained at 118 ° C., passed between rolls maintained at 118 ° C. and provided with a peripheral speed difference, stretched 5 times in the longitudinal direction at 118 ° C., and 1 at 118 ° C. Hold for 2 seconds and cool to 80 ° C. After cooling, it was introduced into a tenter while holding both ends with clips, preheated at 150 ° C., and stretched 6 times in the transverse direction at 155 ° C. Next, while giving 10% relaxation in the transverse direction in the tenter, heat-fixed at 160 ° C., slowly cooled at 100 ° C., cooled to room temperature, slit the edge, wound up, and had a thickness of 21 μm. A porous resin film was obtained.

  Next, 25 parts by mass of “FB-3SDC” manufactured by Denki Kagaku Kogyo Co., Ltd., which are silica particles produced by a dry method as inorganic particles, and Denacol “EX-861” 2 manufactured by Nagase Chemical Industries, Ltd. A suspension prepared by mixing 0.0 part by mass, 1.0 part by mass of “CMC Daicel 2240” manufactured by Daicel Chemical Industries, Ltd., which is cellulose and / or cellulose salt, and 72 parts by mass of ion-exchanged water was prepared. . The above suspension was stirred for 4 hours. Next, the suspension after stirring is applied onto the porous resin film under a condition of a conveyance speed of 2.5 m / min with a die coater so as to have a wet thickness of 15 μm. 3 mm intermittently so as to be 5 mm, and by placing a hose in which a coolant is circulated under the non-laminated part, the temperature rise of the non-laminated part is suppressed, and only the coated part is 100 ° C. And dried for 1 minute to obtain a porous film roll having a total thickness of 25 μm. The center part of the non-laminated part of the obtained porous film roll was slit, and the porous film was obtained. The discharge port part of the used die coater is [edge masking part | 55 mm coating part | 5 mm masking part | 55 mm coating part | 5 mm masking part | 55 mm coating part | edge masking part] The coated part was masked with tape so that the coated part was 3 places in the width direction and the width of the non-laminated part was 5 mm. The end masking portions at both ends were masked to the end so that at least 5 mm of unlaminated portions could be secured. Using the obtained film, a cylindrical assembly was produced according to the method described in (5) Battery assemblability.

  The process passability of the slit process of the obtained film, Gurley air permeability, battery assembly property, and heat resistance were measured. The results are shown in Table 1.

  The obtained film had the same process passability, air permeability, and excellent battery assemblability as the base film, and had heat resistance.

(Example 2)
First, the following composition was compounded with a twin-screw extruder to prepare a resin B chip.

<Polypropylene resin B>
99 parts by mass of homopolypropylene FLX80E4 (hereinafter referred to as PP-1) manufactured by Sumitomo Chemical Co., Ltd. and 1 mass of Engage 8411 (melt index: 18 g / 10 min) manufactured by Dow Chemical which is an ethylene-octene-1 copolymer N, N′-dicyclohexyl-2,6-naphthalenedicarboxyamide (manufactured by Shin Nippon Rika Co., Ltd., Nu-100, hereinafter simply referred to as β crystal nucleating agent) is 0.25 parts. 0.15 and 0.1 parts by mass of IRGANOX 1010 and IRGAFOS 168 manufactured by Ciba Specialty Chemicals, which are antioxidants, respectively (hereinafter referred to simply as “antioxidants”, unless otherwise specified, 3: 2 mass) Compounded with a twin screw extruder.

  Chips made of polypropylene resin B are supplied to a single screw extruder, melt extruded at 220 ° C, removed foreign matter with a 25μm cut sintered filter, and then discharged onto a cast drum whose surface temperature is controlled at 120 ° C with a T-die. Example 1 except that the film was cast so as to be indirectly on the drum for 15 seconds, and was blown into close contact with air by using an air knife from the non-drum surface side of the film to form an unstretched sheet. The same operation was performed. Using the obtained film, a cylindrical assembly was produced according to the method described in (5) Battery assemblability.

  The process passability of the slit process of the obtained film, Gurley air permeability, battery assembly property, and heat resistance were measured. The results are shown in Table 1.

  The obtained film had the same process passability, air permeability, and excellent battery assemblability as the base film, and had heat resistance.

(Example 3)
The discharge port part of the die coater is [edge masking part | 58 mm coating part | 2 mm masking part | 58 mm coating part | 2 mm masking part | 58 mm coating part | edge masking part] Use a die coater that is masked with tape so that the width of the non-laminated part is 2 mm in the width direction (the end masking part at both ends is masked to the end so that at least 2 mm of non-laminated part can be secured). The operation was the same as in Example 1 except that the wet thickness was 15 μm, and the coated portion was 58 mm and the non-laminated portion was 2 mm. Using the obtained film, a cylindrical assembly was produced according to the method described in (5) Battery assemblability.

  The process passability of the slit process of the obtained film, Gurley air permeability, battery assembly property, and heat resistance were measured. The results are shown in Table 1.

  The obtained film had the same process passability, air permeability, and excellent battery assemblability as the base film, and had heat resistance.

Example 4
The discharge port part of the die coater is [edge masking part | 50 mm coating part | 10 mm masking part | 50 mm coating part | 10 mm masking part | 50 mm coating part | edge masking part] Use a die coater masked with tape so that the width of the non-laminated part is 10 mm in the width direction (the end masking part at both ends is masked to the end so that at least 10 mm of non-laminated part can be secured) The operation was the same as in Example 1 except that the wet thickness was 15 μm, and the coated portion was 50 mm and the non-laminated portion was 10 mm. Using the obtained film, a cylindrical assembly was produced according to the method described in (5) Battery assemblability.

  The process passability of the slit process of the obtained film, Gurley air permeability, battery assembly property, and heat resistance were measured. The results are shown in Table 1.

  The obtained film had the same process passability, air permeability, and excellent battery assemblability as the base film, and had heat resistance.

(Example 5)
On the condition of the conveyance speed of 2.5 m / min, the suspension after stirring was applied to the upper surface of the porous resin film so as to have a wet thickness of 15 μm by the same die coater used in Example 1. After three places are applied intermittently so that the coated part is 55 mm and the non-laminated part is 5 mm, the wet part is similarly applied to the lower surface so that the wet thickness is 15 μm, and the coated part is 55 mm and the non-laminated part is 5 mm. The same operation as in Example 1 was carried out except that the coating was intermittently applied at three locations and the whole surface was dried at 100 ° C. for 1 minute. Using the obtained film, a cylindrical assembly was produced according to the method described in (5) Battery assemblability.

  The process passability of the slit process of the obtained film, Gurley air permeability, battery assembly property, and heat resistance were measured. The results are shown in Table 1.

  The obtained film had the same process passability, air permeability, and excellent battery assemblability as the base film, and had heat resistance.

(Example 6)
Under the condition of a conveyance speed of 2.5 m / min, the suspension after stirring was applied to the upper surface of the porous resin film so as to have a wet thickness of 15 μm by the same die coater used in Example 3. After applying three places intermittently so that the coated part is 58 mm and the non-laminated part is 2 mm, similarly, it is applied to the lower surface so that the wet thickness is 15 μm, and the coated part is 58 mm and the non-laminated part is 2 mm. The same operation as in Example 1 was carried out except that the coating was intermittently applied at three locations and the whole surface was dried at 100 ° C. for 1 minute. Using the obtained film, a cylindrical assembly was produced according to the method described in (5) Battery assemblability.

  The process passability of the slit process of the obtained film, Gurley air permeability, battery assembly property, and heat resistance were measured. The results are shown in Table 1.

  The obtained film had the same process passability, air permeability, and excellent battery assemblability as the base film, and had heat resistance.

(Example 7)
Under the condition of a conveyance speed of 2.5 m / min, the suspension after stirring was applied to the upper surface of the porous resin film with a die coater similar to that used in Example 4 so that the wet thickness was 15 μm. After applying three places intermittently so that the coated part is 50 mm and the non-laminated part is 10 mm, the coated part is similarly applied to the lower surface so that the wet thickness is 15 μm, and the coated part is 50 mm and the non-laminated part is 10 mm. The same operation as in Example 1 was carried out except that the coating was intermittently applied at three locations and the whole surface was dried at 100 ° C. for 1 minute. Using the obtained film, a cylindrical assembly was produced according to the method described in (5) Battery assemblability.

  The process passability of the slit process of the obtained film, Gurley air permeability, battery assembly property, and heat resistance were measured. The results are shown in Table 1.

  The obtained film had the same process passability, air permeability, and excellent battery assemblability as the base film, and had heat resistance.

(Example 8)
On the condition of the conveyance speed of 2.5 m / min, the suspension after stirring was applied to the upper surface of the porous resin film so as to have a wet thickness of 15 μm by the same die coater used in Example 1. After applying three places intermittently so that the coating part 55 mm and the non-laminated part become 5 mm, it was applied to the lower surface with a die coater similar to that used in Example 3 to a wet thickness of 15 μm, The same operation as in Example 1 was performed, except that three portions were applied intermittently so that the coated portion was 58 mm and the non-laminated portion was 2 mm, and the whole surface was dried at 100 ° C. for 1 minute. Using the obtained film, a cylindrical assembly was produced according to the method described in (5) Battery assemblability.

  The process passability of the slit process of the obtained film, Gurley air permeability, battery assembly property, and heat resistance were measured. The results are shown in Table 1.

  The obtained film had the same process passability, air permeability, and excellent battery assemblability as the base film, and had heat resistance.

Example 9
On the condition of the conveyance speed of 2.5 m / min, the suspension after stirring was applied to the upper surface of the porous resin film so as to have a wet thickness of 15 μm by the same die coater used in Example 1. After applying three places intermittently so that the coated part is 55 mm and the non-laminated part is 5 mm, it is applied to the lower surface by a die coater similar to that used in Example 4 so that the wet thickness is 15 μm. The same operation as in Example 1 was performed, except that the coating part was intermittently applied at three places so that the coated part was 50 mm and the non-laminated part was 10 mm, and the whole surface was dried at 100 ° C. for 1 minute. Using the obtained film, a cylindrical assembly was produced according to the method described in (5) Battery assemblability.

  The process passability of the slit process of the obtained film, Gurley air permeability, battery assembly property, and heat resistance were measured. The results are shown in Table 1.

  The obtained film had the same process passability, air permeability, and excellent battery assemblability as the base film, and had heat resistance.

(Example 10)
Film formation was performed according to the following method described in Example 4 of Japanese Patent No. 4280371. An ethylene-octene copolymer produced with a metallocene catalyst having a weight average molecular weight of 2 million ultra high molecular weight polyethylene (UHMWPE) 30 mass%, a weight average molecular weight of 350,000 high density polyethylene (HDPE) 40 mass%, and a melting point of 108 ° C. (AffinityPOP FM1570, octene content 7.5 mol%) A polyolefin composition in which 0.375 parts by mass of an antioxidant is added to 100 parts by mass of a composition consisting of 10% by mass and 20% by mass of polypropylene having a weight average molecular weight of 530,000. Melting point 165 ° C.). 30 parts by mass of this polyolefin composition was put into a twin screw extruder (58 mmφ, L / D = 42, strong kneading type). Moreover, 70 mass parts of liquid paraffin was supplied from the side feeder of this twin-screw extruder, and it melt-kneaded at 200 rpm, and prepared the polyolefin solution in an extruder. Subsequently, a gel-like sheet was formed while being extruded at 190 ° C. from a T die installed at the tip of the extruder and being taken up by a cooling roll. Subsequently, this gel-like sheet was simultaneously biaxially stretched at 116 ° C. 5 × 5 times to obtain a stretched film. The obtained stretched membrane was washed with methylene chloride to extract and remove the remaining liquid paraffin, and then the same operation as in Example 1 was performed except that a porous resin film was obtained by drying and heat setting at 120 ° C. . Using the obtained film, a cylindrical assembly was produced according to the method described in (5) Battery assemblability.

  The process passability of the slit process of the obtained film, Gurley air permeability, battery assembly property, and heat resistance were measured. The results are shown in Table 1.

  The obtained film had the same process passability, air permeability, and excellent battery assemblability as the base film, and had heat resistance.

(Example 11)
On the condition of the conveyance speed of 2.5 m / min, the suspension after stirring was applied to the upper surface of the porous resin film so as to have a wet thickness of 15 μm by the same die coater used in Example 1. After applying three places intermittently so that the coated part is 55 mm and the non-laminated part is 5 mm, it is applied to the lower surface by a die coater similar to that used in Example 4 so that the wet thickness is 15 μm. The same operation as in Example 1 was carried out except that three places were applied intermittently so that the coated part was 52 mm and the non-laminated part was 8 mm, and the whole surface was dried at 100 ° C. for 1 minute. Using the obtained film, a cylindrical assembly was produced according to the method described in (5) Battery assemblability.

  The process passability of the slit process of the obtained film, Gurley air permeability, battery assembly property, and heat resistance were measured. The results are shown in Table 1.

  The obtained film had the same process passability, air permeability, and excellent battery assemblability as the base film, and had heat resistance.

(Comparative Example 1)
The same operation as in Example 1 was performed except that the suspension was not applied. Using the obtained film, a cylindrical assembly was produced according to the method described in (5) Battery assemblability.

  The process passability of the slit process of the obtained film, Gurley air permeability, battery assembly property, and heat resistance were measured. The results are shown in Table 1.

  The obtained film had the same process passability, air permeability, and excellent battery assemblability equivalent to the base film, but formation of pores by melting was seen in the obtained film, and the shrinkage rate In addition, the heat resistance was insufficient.

(Comparative Example 2)
The same operation as in Example 1 was performed except that the suspension was applied to the entire surface of the porous resin film. Using the obtained film, a cylindrical assembly was produced according to the method described in (5) Battery assemblability.

  The process passability of the slit process of the obtained film, Gurley air permeability, battery assembly property, and heat resistance were measured. The results are shown in Table 1.

  The obtained film had excellent air permeability and heat resistance, but the process passability and battery assembly were insufficient.

(Comparative Example 3)
The same operation as in Example 1 was performed except that the coating part was 45 mm and the non-laminated part was 15 mm. Using the obtained film, a cylindrical assembly was produced according to the method described in (5) Battery assemblability.

  The process passability of the slit process of the obtained film, Gurley air permeability, battery assembly property, and heat resistance were measured. The results are shown in Table 1.

  Although the obtained film had the same process passability, excellent air permeability and battery assemblability as the base film, the shrinkage was large and the heat resistance was insufficient.

(Comparative Example 4)
As an oxirane ring-containing compound, 2.0 parts by mass of Denasel “EX-861” manufactured by Nagase Kasei Kogyo Co., Ltd. and 1.0 part by mass of “CMC Daicel 2240” manufactured by Daicel Chemical Industries, Ltd., which is cellulose and / or cellulose salt And 97 parts by mass of ion-exchanged water, and the same operation as in Example 1 was performed except that the suspension was changed to a mixed suspension. Using the obtained film, a cylindrical assembly was produced according to the method described in (5) Battery assemblability.

  The process passability of the slit process of the obtained film, Gurley air permeability, battery assembly property, and heat resistance were measured. The results are shown in Table 1.

  In this case, although it had the battery assembly property excellent in process permeability and air permeability equivalent to the base film, the heat resistance was insufficient.

  The porous film of the present invention can be provided as a porous film that does not drop off inorganic particles in the porous layer, has high air permeability, and exhibits excellent battery characteristics when used as a separator.

DESCRIPTION OF SYMBOLS 1 Porous resin film 2 Porous layer 3 Porous layer 4 Porous film 5 Negative electrode 6 Positive electrode 7 Electrical storage device separator 8 Porous film roll 9 Unlaminated part 10 Edge part of the longitudinal direction of porous layer

Claims (8)

When a porous layer containing inorganic particles is provided on at least one surface of the porous resin film, the width of the porous layer containing inorganic particles is Wh, and the width of the porous resin film is W2, Wh <W2 A porous film in which a portion that is satisfied and does not substantially have a porous layer containing inorganic particles is present in one or both of the width direction, and a portion having a porous layer containing inorganic particles has air permeability. A portion not having a porous layer containing inorganic particles exists in both the width direction, and when one width length is Δ1 (mm) and the other width length is Δ2 (mm), Δ1 and Δ2 are The porous film according to claim 1 satisfying the following.
| Δ1-Δ2 | <0.5 mm
0.5mm ≦ Δ1 ≦ 5mm
0.5mm ≦ Δ2 ≦ 5mm The porous film according to claim 1 or 2, wherein the cross-sectional shape of the edge portion in the longitudinal direction of the porous layer containing inorganic particles has a curve, a corner, or a chamfer. When the thickness of the porous resin film when applying a load of 0.06 kg / cm ² and D1, and the thickness of the porous resin film when applying a load of 6 kg / cm ² and D2, 75% ≦ D2 The porous film according to any one of claims 1 to 3, which satisfies / D1. The porous film in any one of Claims 1-4 in which the porous layer containing an inorganic particle exists in both surfaces of the porous resin film. The porous film in any one of Claims 1-5 used for an electrical storage device separator. An electricity storage device using the porous film according to claim 6 as an electricity storage device separator. A porous layer containing inorganic particles exists on both sides of the porous resin film, the width of the porous layer containing inorganic particles on the positive electrode side of the porous film is W3, and the width of the porous layer containing inorganic particles on the negative electrode side When W1 is W, the width of the active material layer of the positive electrode is W (positive electrode), and the width of the active material layer of the negative electrode is W (negative electrode), 0 ≦ W1−W3 ≦ 20 mm, and An electricity storage device using the porous film according to claim 5 as an electricity storage device separator, wherein W3 ≧ W (positive electrode) and W1 ≧ W (negative electrode).

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