JP2019016436A - Laminated film roll and method of manufacturing the same - Google Patents

Abstract

To provide: a laminated film roll including a laminated film wound thereon and capable of manufacturing an electrochemical element with high yield, the laminated film roll being capable of suppressing lamination deviation when a positive electrode and a negative electrode are laminated to form an electrode body while a laminated film comprising an inorganic particle layer formed on a polyolefin microporous film is used as a separator, and a method of manufacturing the same.SOLUTION: A laminated film roll 10 includes a core 1 having a cylindrical shape and a laminated film 2 wound around the core 1. In the laminated film roll, the difference ▵Rbetween the maximum outer diameter Dand the minimum outer diameter Din a width direction is 0.05-1.5 mm, and the laminated film 2 includes a polyolefin microporous film and an inorganic particle layer containing inorganic particles formed on the surface of the polyolefin microporous film.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a laminated film roll and a method for producing the same.

  Conventionally, there are electrochemical elements such as a lithium ion battery, a polymer lithium battery, and an electric double layer capacitor. Generally as a separator for isolating the positive electrode and negative electrode of an electrochemical element, the resin porous film | membrane which has a thermoplastic resin as a main component is used. In particular, a separator made of a porous resin membrane mainly composed of polyolefin is stable against harsh redox atmospheres such as lithium ion batteries, and the pores are closed near the melting point of the constituent resin, so-called shutdown characteristics. Is widely used.

However, a separator made of a porous resin film containing a thermoplastic resin as a main component lacks the ability to maintain the film at a temperature equal to or higher than the melting point of the thermoplastic resin, so that the film is likely to break. When a film breakage of the separator occurs in the electrochemical element, there is a possibility that a short-circuit phenomenon occurs in which the positive electrode and the negative electrode are in direct contact.
For this reason, a laminated film having a resin porous film and a heat resistant layer containing a material having high heat resistance such as inorganic particles formed on the surface thereof is used as the separator.

For example, Patent Document 1 describes a separator having a heat-resistant porous layer containing 70% by volume or more of heat-resistant fine particles on the surface of a resin porous film.
In Patent Document 2, a polyolefin resin porous membrane has a wetting index (surface tension of the resin porous membrane) of at least one surface of 40 mN / m or more, and a separator provided with a porous layer made of an inorganic filler and a resin binder on the surface. Is described.
Patent Document 3 describes a separator in which a surface having a wettability of 40 mN / m or more is coated with a heat-resistant layer.
Patent Document 4 describes a method for producing a laminated porous film in which a coating layer containing a filler and a resin binder is laminated on a polyolefin resin porous film.

JP 2008-123996 A JP 2008-186722 A JP 2010-21033 A JP 2013-116966 A

  However, when a conventional laminated film having a porous resin film and a heat-resistant layer is used as a separator for an electrochemical device, the separator, the positive electrode, and the negative electrode cannot be accurately laminated in the process of forming the electrode body, and the stacking error It was easy to occur. In particular, when a separator is wound together with a positive electrode and a negative electrode to form a wound body, winding failure due to winding deviation tends to occur. For this reason, it has been required to suppress the stacking deviation in the step of forming the electrode body and to improve the yield of the electrochemical device.

  The present invention has been made in view of the above circumstances, and is a laminated film in which an inorganic particle layer is formed on a polyolefin microporous film, which is used as a separator and laminated with a positive electrode and a negative electrode to form an electrode body. It is an object of the present invention to provide a laminated film roll wound with a laminated film capable of suppressing the stacking deviation in the case of being formed and manufacturing an electrochemical element with a high yield, and a method for manufacturing the same.

In order to solve the above problems, the present inventors generate an electrode body by laminating a separator made of a laminated film in which an inorganic particle layer is formed on a polyolefin microporous film, and a positive electrode and a negative electrode. Focusing on the stacking deviation, we conducted extensive research.
As a result, as the laminated film roll wound with the laminated film used as the separator, the smaller the difference ΔR ₁ between the maximum outer diameter and the minimum outer diameter in the width direction, the more the laminating shift in the step of forming the electrode body Has been found to be suppressed. This is because by reducing ΔR ₁ of the laminated film roll, the tension applied to the laminated film becomes uniform when the laminated film is unwound from the laminated film roll, and the distortion of the laminated film due to the unwinding. It is estimated that this is because the separator can be positioned with high accuracy.

Furthermore, the inventors have repeatedly studied, and by forming ΔR ₁ of the laminated film roll in the range of 0.05 to 1.5 mm, an electrode body is formed using the laminated film unwound from the laminated film roll as a separator. The present invention has been completed by confirming that the stacking deviation can be sufficiently prevented.
That is, the present invention adopts the following configuration.

(1) It consists of a cylindrical core and a laminated film wound around the core,
The difference ΔR ₁ between the maximum outer diameter and the minimum outer diameter in the width direction is 0.05 to 1.5 mm,
The laminated film roll comprising a polyolefin microporous film and an inorganic particle layer containing inorganic particles formed on the surface thereof.

(2) The laminated film roll according to (1), wherein the inorganic particle layer has a thickness variation in the width direction of 0.8 μm or less.
(3) The laminated film roll according to (1), wherein variation in the basis weight of the inorganic particle layer is 0.6 g / m ² or less.

(4) The inorganic particle layer is formed by drying a coating liquid containing inorganic particles, and the surface tension of the coating liquid is 35 mN / m or less (1) The laminated film roll according to any one of to (3).
(5) The laminated film roll according to any one of (1) to (4), wherein the polyolefin microporous film has a wetting index of 35 mN / m or less.

(6) A method for producing a laminated film roll according to any one of (1) to (5),
A core of cylindrical shape, made of a polyolefin microporous film wound on the core, the difference △ R ₂ between the maximum outer diameter and the minimum outer diameter in the width direction, a microporous film which is a 0.05~1.2mm Unwinding the polyolefin microporous film from a roll;
A step of forming a laminated film by applying a coating liquid containing inorganic particles and having a viscosity of 5 to 80 mPa · s on the polyolefin microporous film and drying to form an inorganic particle layer;
And a step of winding the laminated film around a cylindrical core.

(7) The method for producing a laminated film roll according to (6), wherein a surface tension of the coating liquid is not more than a wetting index of the polyolefin microporous film.
(8) The method for producing a laminated film roll according to (6) or (7), wherein the coating liquid has a surface tension of 35 mN / m or less.
(9) The method for producing a laminated film roll according to any one of (6) to (8), wherein the polyolefin microporous film has a wetting index of 35 mN / m or less.

The laminated film roll of the present invention is a film in which a laminated film having a polyolefin microporous film and an inorganic particle layer containing inorganic particles formed on the surface thereof is wound around a core, and has a maximum outer diameter in the width direction. The difference ΔR _{1 from the} minimum outer diameter is 0.05 to 1.5 mm. For this reason, when the laminated film unwound from the laminated film roll is used as a separator and laminated with the positive electrode and the negative electrode to form an electrode body, the amount of sag when unwinding the laminated film is small, and the tension applied to the laminated film Becomes uniform. Therefore, positioning of the separator can be performed accurately. As a result, an electrode body in which the stacking deviation between the positive and negative electrodes and the separator (laminated film) is suppressed is obtained. In particular, when a laminated film unwound from the laminated film roll of the present invention is used as a separator and wound together with a positive electrode and a negative electrode to form a wound body, the separator, the positive electrode, and the negative electrode can be wound with high accuracy. Deviation can be suppressed. Therefore, the winding defect of the wound body due to the winding deviation can be sufficiently prevented, and the wound body can be produced with a high yield.

  The laminated film wound around the laminated film roll of the present invention has an inorganic particle layer containing inorganic particles on the surface of the polyolefin microporous film. For this reason, heat resistance is favorable and it is suitable as a separator of an electrochemical element. Specifically, an electrochemical device using a laminated film unwound from the laminated film roll of the present invention as a separator has excellent safety at high temperatures.

According to the method for producing a laminated film roll of the present invention, the laminated film roll of the present invention having a difference ΔR ₁ between the maximum outer diameter and the minimum outer diameter in the width direction of 0.05 to 1.5 mm is obtained.

It is a schematic diagram for demonstrating the laminated film roll of this embodiment. It is a cross-sectional schematic diagram for demonstrating an example of the laminated film 2 which comprises the laminated film roll 10 shown in FIG. It is the schematic which showed an example of the manufacturing apparatus of a laminated film roll. It is the schematic perspective view which showed an example of the measuring device which measures the external shape change of the width direction of a roll.

Hereinafter, the laminated film roll of the present invention and the method for producing the laminated film roll will be described in detail with examples.
"Laminated film roll"
FIG. 1 is a schematic diagram for explaining the laminated film roll of the present embodiment.
A laminated film roll 10 shown in FIG. 1 includes a cylindrical core 1 and a laminated film 2 wound around the core 1. The laminated film 2 is used as a separator for an electrochemical element. Specifically, the laminated film 2 unwound from the laminated film roll 10 can be suitably used as a separator for a lithium secondary battery.

The laminated film roll 10 shown in FIG. 1 has a difference ΔR ₁ between the maximum outer diameter D ₁ and the minimum outer diameter D _{2 in} the width direction of 0.05 to 1.5 mm. When ΔR ₁ exceeds 1.5 mm, the tension applied to the laminated film 2 becomes non-uniform when the laminated film 2 is unwound from the laminated film roll 10. For this reason, the distortion of the laminated film 2 resulting from unwinding the laminated film 2 increases, and the amount of sag of the laminated film 2 unwound from the laminated film roll 10 increases. As a result, when the laminated film 2 is used as a separator, the separator, the positive electrode, and the negative electrode cannot be accurately laminated in the step of forming the electrode body, and stacking deviation is likely to occur. Therefore, ΔR ₁ is 1.5 mm or less and preferably 1.2 mm or less.

On the other hand, in order to obtain the laminated film roll 10 having ΔR ₁ of less than 0.05 mm, it is necessary to greatly improve the accuracy of the manufacturing equipment used when the laminated film 2 is wound around the core 1, and the cost increases. It becomes. Therefore, ΔR ₁ is 0.05 mm or more, and more preferably 0.1 mm or more.

The width of the laminated film roll 10 is preferably 300 to 5000 mm. As the width of the laminated film roll 10 is narrower, a laminated film roll 10 having a smaller ΔR ₁ is easily obtained. When the width of the laminated film roll 10 is 2000 mm or less, the laminated film roll 10 having ΔR ₁ of 1.5 mm or less can be easily obtained.

  The length (winding length) of the laminated film 2 wound around the core 1 is preferably 100 to 20000 m. The longer the winding length of the laminated film 2, the greater the number of electrochemical elements that can be produced using one laminated film roll 10 when the laminated film 2 is used as a separator for electrochemical elements. Therefore, the trouble of replacing the laminated film roll 10 is saved, and the productivity of the electrochemical device is improved. Therefore, the winding length of the laminated film 2 is preferably 100 m or more, more preferably 2000 m or more, and particularly preferably 5000 m or more.

On the other hand, when the winding length of the layered film 2 is too long, winding accuracy relative to the core 1 of the laminated film 2 tends to decrease, the maximum outer diameter D ₁ and the minimum outer diameter D in the width direction of the laminated film roll 10 _It becomes difficult to adjust the difference ΔR ₁ from ₂ within the above range. For this reason, the winding length of the laminated film 2 is preferably 20000 m or less, more preferably 15000 m or less, and particularly preferably 10,000 m or less.

FIG. 2 is a schematic cross-sectional view for explaining an example of the laminated film 2 constituting the laminated film roll 10 shown in FIG. As shown in FIG. 2, the laminated film 2 includes a polyolefin microporous film 20 and an inorganic particle layer 3 formed on the surface of the polyolefin microporous film 20.
As in the laminated film 2 shown in FIG. 2, the inorganic particle layer 3 may be formed on only one layer of the polyolefin microporous film 20 (upper surface in FIG. 2), or a plurality of layers on one surface. It may be formed, or one or more layers may be formed on both sides of the polyolefin microporous film.

  The thickness (total thickness) of the laminated film 2 is preferably 6 μm or more in order to ensure the function required for the separator (the function of separating the positive electrode and the negative electrode). Moreover, when the laminated film 2 is used as a separator for an electrochemical element, the thickness of the laminated film 2 is preferably 50 μm or less from the viewpoint of suppressing a decrease in energy density of the electrochemical element.

When the thickness of the polyolefin microporous film 20 forming the laminated film 2 is Ta (μm) and the thickness of the inorganic particle layer 3 is Tb (μm), the ratio Ta / Tb between Ta and Tb is 5 or less. Preferably, it is preferably 4 or less. Further, the ratio Ta / Tb is preferably 1 or more, and more preferably 2 or more. When the ratio Ta / Tb is 1 to 5, the thermal contraction of the entire laminated film 2 is effectively suppressed. Therefore, when the laminated film 2 having the ratio Ta / Tb of 1 to 5 is used as a separator for an electrochemical element, occurrence of a short circuit due to thermal contraction of the laminated film 2 (separator) can be highly suppressed.
In addition, when the inorganic particle layer 3 exists in the laminated film 2 in multiple layers, such as when the inorganic particle layer 3 exists in both surfaces of the polyolefin microporous film 20, thickness Tb is the total thickness (total of the inorganic particle layer 3). Thickness).

When the laminated film 2 is used as a separator for an electrochemical device, the porosity of the entire laminated film 2 is 30 in a dry state from the viewpoint of securing a sufficient amount of electrolyte solution and improving ion permeability. % Or more is preferable. On the other hand, from the viewpoint of ensuring the strength of the laminated film 2 and preventing an internal short circuit when used as a separator, the porosity of the laminated film 2 is preferably 70% or less in a dry state.
In order to set the porosity of the laminated film 2 to 30 to 70%, the porosity of the polyolefin microporous film 20 is preferably 30 to 70%, and the porosity of the inorganic particle layer 3 is 20 to 60%. It is preferable that

  The peel strength at 180 ° between the polyolefin microporous film 20 and the inorganic particle layer 3 in the laminated film 2 is preferably 0.5 N / cm or more, and more preferably 1.0 N / cm or more. When the peel strength between the polyolefin microporous film 20 and the inorganic particle layer 3 satisfies the above value, the effect of suppressing the thermal contraction of the entire laminated film 2 by the inorganic particle layer 3 becomes better, and the laminated film 2 is used as a separator. This improves the safety of the electrochemical device. The upper limit of the peel strength at 180 ° between the polyolefin microporous film 20 and the inorganic particle layer 3 is usually about 5 N / cm.

The peel strength at 180 ° between the polyolefin microporous film 20 and the inorganic particle layer 3 in the laminated film 2 is a value measured by the following method.
First, a test piece having a size of 5 cm long × 2 cm wide is cut out from the laminated film 2. Subsequently, an adhesive tape is affixed on the area | region of 2 cm x 2 cm from the one end in the surface of the inorganic particle layer 3 of a test piece. The size of the adhesive tape is about 2 cm wide and about 5 cm long, and the adhesive tape is attached so that one end of the adhesive tape and one end of the test piece are aligned. Then, using a tensile tester, the end of the test piece with the adhesive tape attached is opposite to the end of the adhesive tape and the end of the adhesive tape is opposite to the end attached to the test piece. The strength is measured when the inorganic particle layer 3 is peeled off by holding the side and pulling at a pulling speed of 10 mm / min.

  The peel strength at 180 ° between the polyolefin microporous film 20 and the inorganic particle layer 3 in the laminated film 2 is determined by selecting the type of binder included in the inorganic particle layer 3, adjusting the binder content, and adjusting the inorganic particle layer 3. It can be adjusted as appropriate by adjusting the surface tension of the coating liquid used when forming the film.

(Polyolefin microporous film)
The polyolefin microporous film 20 is a base material of the laminated film 2. The polyolefin microporous film 20 plays a role of separating the positive electrode and the negative electrode when the laminated film 2 is used as a separator of an electrochemical element, for example.
As the polyolefin microporous film 20 forming the laminated film 2, a general-purpose polyolefin microporous film applied to a separator of an electrochemical element can be used.

  The thickness of the polyolefin microporous film 20 is preferably 5 to 30 μm. If the polyolefin microporous film 20 is too thin, the shutdown characteristics may be weakened when the laminated film 2 is used as a separator for an electrochemical element. If the polyolefin microporous film 20 is too thick, when the laminated film 2 is used as a separator for an electrochemical element, the energy density of the electrochemical element may be lowered. On the other hand, if the polyolefin microporous film 20 is too thick, the heat shrinkage of the polyolefin microporous film 20 becomes large, and the effect of suppressing the heat shrinkage of the entire laminated film 2 by the inorganic particle layer 3 may be insufficient.

  The polyolefin microporous film 20 preferably has a compression modulus of 95 MPa or more and 150 MPa or less, more preferably 100 to 140 MPa, and particularly preferably 105 to 130 MPa. When the compression modulus of the polyolefin microporous film 20 is 95 MPa or more and 150 MPa or less, even if the laminated film 2 is wound around the core 1 to form the laminated film roll 10 and then unwound from the laminated film roll 10, the laminated film 2 The shape of is hard to be damaged. Therefore, it is possible to more effectively suppress the misalignment when the laminated film 2 is used as a separator and the electrode body is formed by laminating the positive electrode and the negative electrode.

When the compression modulus of the polyolefin microporous film 20 is in the above range, the polyolefin microporous film 20 unwound from the microporous film roll around which the polyolefin microporous film 20 is wound when the laminated film roll 10 is manufactured. The amount of sagging is small. For this reason, the laminated film roll 10 is preferable because the difference ΔR ₁ between the maximum outer diameter D ₁ and the minimum outer diameter D _{2 in} the width direction is small.

The polyolefin microporous film 20 preferably contains at least one of polypropylene and polyethylene. When the polyolefin microporous film 20 contains polyethylene, it melts in the vicinity of its melting point (about 135 ° C.), and at about 140 ° C. or less, the pores are blocked to stop the battery reaction. It becomes possible to make it. On the other hand, when the polyolefin microporous film 20 contains polypropylene, the melting point (approximately 170 ° C.) is sufficiently higher than the normal use temperature range (approximately 120 ° C. or less) of the battery. It becomes easy to construct a microporous film having a small thickness.
The polyolefin microporous film 20 preferably contains at least polyethylene from the viewpoint of providing shutdown characteristics to the electrochemical element when the laminated film 2 is used as a separator for the electrochemical element.

When the polyolefin microporous film 20 contains polypropylene, it is preferable to contain polypropylene having a weight average molecular weight of 500,000 or more. In this case, the microporous film roll wound with the polyolefin microporous film 20 used as the material of the laminated film roll 10 tends to have a small difference ΔR ₂ between the maximum outer diameter and the minimum outer diameter in the width direction. For this reason, the laminated film roll 10 is preferable because it tends to have a small difference ΔR ₁ between the maximum outer diameter D ₁ and the minimum outer diameter D _{2 in} the width direction.

When the polyolefin microporous film 20 contains polyethylene, it is preferable to contain polyethylene having a weight average molecular weight of 350,000 or more. In this case, the microporous film roll wound with the polyolefin microporous film 20 used as the material of the laminated film roll 10 tends to have a small difference ΔR ₂ between the maximum outer diameter and the minimum outer diameter in the width direction. For this reason, the laminated film roll 10 is preferable because it tends to have a small difference ΔR ₁ between the maximum outer diameter D ₁ and the minimum outer diameter D _{2 in} the width direction.

The polyolefin microporous film 20 may be a single-layer polyethylene microporous film, a single-layer polypropylene microporous film, or a multilayer structure including a polypropylene layer and a polyethylene layer. .
As shown in FIG. 2, the multi-layer polyolefin microporous film 20 preferably has a three-layer structure in which a polyethylene layer 21 is an intermediate layer and polypropylene layers 22 and 22 are outer layers. When the polyolefin microporous film 20 is a laminated microporous film having a three-layer structure shown in FIG. 2, the heat resistance and mechanical strength are excellent. Furthermore, since the polyolefin microporous film 20 shown in FIG. 2 has a relatively small thermal shrinkage at the shutdown temperature, the electrochemical element having higher safety and reliability when the laminated film 2 is used as a separator for the electrochemical element. Is obtained.

(Inorganic particle layer)
The inorganic particle layer 3 contains inorganic particles and improves the heat resistance of the laminated film 2. The inorganic particle layer 3 may be formed of a single inorganic particle layer as shown in FIG. 2 or may be a laminate in which a plurality of inorganic particle layers are laminated.

The thickness of the inorganic particle layer 3 (when a plurality of inorganic particle layers 3 are laminated on the laminated film 2), the thickness of the plurality of inorganic particle layers is preferably 1 μm or more, and preferably 2 μm or more. More preferably, it is 4 μm or more. If the thickness of the inorganic particle layer 3 is too thin, the effect of suppressing the thermal contraction of the entire laminated film 2 cannot be obtained sufficiently, and the heat resistance of the laminated film 2 may be insufficient.
The thickness of the inorganic particle layer 3 is preferably 10 μm or less, more preferably 8 μm or less, and particularly preferably 6 μm or less. When the thickness of the inorganic particle layer 3 is too thick, the thickness of the entire laminated film 2 is increased.

The inorganic particle layer 3 preferably has a thickness variation in the width direction of the laminated film roll 10 of 0.8 μm or less, more preferably 0.6 μm or less, and particularly preferably 0.4 μm or less. . The smaller the variation in the thickness of the inorganic particle layer 3 in the width direction, the easier it is to adjust ΔR ₁ to the target range.
The inorganic particle layer 3 preferably has a basis weight variation of 0.6 g / m ² or less, and more preferably 0.4 g / m ² or less. As variation in the basis weight of the inorganic particle layer 3 is small, easily adjusted to the target range of △ R _1.

Variation in the thickness of the inorganic particle layer 3 in the width direction of the laminated film roll 10 can be measured by the following method.
The laminated film 2 is cut out from the laminated film roll 10 by about 50 cm in the longitudinal direction to obtain a test piece. Next, the test piece is folded so that a crease is generated in a direction perpendicular to the longitudinal direction, and the laminated film 2 is folded to a thickness of 10 sheets. Next, the thickness of the test piece in a folded state is measured at a uniform interval in the width direction (the direction along the crease) using a thickness measuring instrument, and the thickness at each measurement point (X ₁ , X ₂ , X ₃ ... X _m : m is the number of measurement points). Here, the number of measurement points: m may be a value of about 25.

Moreover, about the polyolefin microporous film 20 before forming the inorganic particle layer 3 used as a material of the laminated film 2, the thickness is measured by the method shown below in the same manner as the laminated film 2 cut out from the laminated film roll 10. .
That is, the polyolefin microporous film 20 is cut out about 50 cm in the longitudinal direction from the microporous film roll to obtain a test piece made of the polyolefin microporous film 20. Subsequently, the test piece which consists of the polyolefin microporous film 20 is folded up similarly to the case where the thickness of the laminated film 2 is measured, and the polyolefin microporous film 20 is folded in a thickness of 10 sheets. Next, the thickness of the test piece in the folded state is measured in the same manner as when the thickness of the laminated film 2 is measured, and the thickness at each measurement point (Y ₁ , Y ₂ , Y ₃ ... Y _m : m Is the number of measurement points). Here, the number of measurement points: m is the same as when the thickness of the laminated film 2 is measured.

With respect to the position of each measurement point corresponding to the test piece of the laminated film 2 in the folded state and the test piece of the polyolefin microporous film 20 in the folded state, the lamination for 10 sheets is performed according to the following formula. The thickness of the inorganic particle layer 3 at each measurement point is calculated from the thickness (X _m ) of the membrane 2 and the thickness (Y _m ) of the test piece of the polyolefin microporous film 20 for ten sheets.
Thickness of the inorganic particle layer 3 at each measurement point = (X _m −Y _m ) / 10
And the difference of the maximum value in the calculation result of the thickness of the inorganic particle layer 3 in each measurement point is calculated | required, and it is set as the dispersion | variation in the thickness of the inorganic particle layer 3 in the width direction.

The variation in the basis weight of the inorganic particle layer 3 in the width direction of the laminated film roll 10 can be measured by the following method.
The laminated film 2 is cut about 50 cm in the longitudinal direction from the laminated film roll 10 to obtain fragments. Next, about 5 to 10 rectangular test pieces having a length of 10 cm in the longitudinal direction and a length of 5 cm in the width direction are cut out from the pieces at equal intervals in the width direction. The weight of each test piece obtained (S ₁ , S ₂ , S ₃ ... S _n : n is a value corresponding to the position of each test piece) is measured.

Moreover, about the polyolefin microporous film 20 before forming the inorganic particle layer 3 used as a material of the laminated film 2, the test piece is cut out in the same manner as the laminated film 2 cut out from the laminated film roll 10, and the weight is measured. .
That is, the polyolefin microporous film 20 is cut out from the microporous film roll by about 50 cm in the longitudinal direction to obtain a fragment made of the polyolefin microporous film 20. Next, a test piece having a position and a number corresponding to the test piece cut out from the piece of the laminated film 2 is cut out from the piece made of the polyolefin microporous film 20. Thereafter, the weight of each test piece made of the microporous polyolefin film 20 (T ₁ , T ₂ , T ₃ ... T _n : n is a value corresponding to the position of each test piece) is measured.

Using the test piece of the laminate film 2 and the test piece of the polyolefin microporous film 20 corresponding to the positions cut out from the fragments, the test piece of the polyolefin microporous film 20 and the weight of the test piece of the laminate film 2 (S _n ) The difference (S _n -T _n ) with respect to the weight (T _n ) is calculated, and the basis weight of the inorganic particle layer 3 at the position of each test piece is calculated.
And the difference of the maximum value in the calculation result of the fabric weight of the inorganic particle layer 3 in the position of each test piece is calculated | required, and it is set as the dispersion | variation in the fabric weight of the inorganic particle layer 3 in the width direction.

The inorganic particle layer 3 preferably includes inorganic particles having electrical insulation.
Examples of the inorganic particles contained in the inorganic particle layer 3 include oxide particles such as iron oxide, silica, alumina, TiO ₂ , BaTiO ₃ , and MgO; nitride particles such as aluminum nitride and silicon nitride; calcium fluoride, fluorine Insoluble ion-binding particles such as barium fluoride and barium sulfate; Covalent bonding particles such as silicon and diamond; Clay particles such as montmorillonite; In addition, the inorganic particles may be materials derived from mineral resources such as boehmite, zeolite, apatite, kaolin, mullite, spinel, olivine, mica, or these artificial products. An inorganic particle may be used individually by 1 type, and may use 2 or more types together. Among the above, the inorganic particles contained in the inorganic particle layer 3 are preferably any one or more selected from alumina, silica, and boehmite.

The average particle size of the inorganic particles is preferably 0.01 μm or more, and more preferably 0.1 μm or more. Further, the average particle size of the inorganic particles is preferably 3 μm or less, and more preferably 2 μm or less.
The average particle diameter of the inorganic particles can be defined as, for example, a number average particle diameter measured by dispersing the inorganic particles in a medium in which the inorganic particles are not dissolved using a laser scattering particle size distribution meter (for example, “LA-920” manufactured by HORIBA).

  As a form of the inorganic particles, for example, it may have a shape close to a sphere or may have a plate shape. From the viewpoint of short circuit prevention, the form of the inorganic particles is preferably plate-like particles or secondary particles in which primary particles are aggregated. Typical examples of the plate-like particles include plate-like alumina and plate-like boehmite. Typical secondary particles include secondary particulate alumina, secondary particulate boehmite, and the like.

The aspect ratio of the plate-like particles (the ratio of the maximum length in the plate-like particles to the thickness of the plate-like particles) is preferably 2 or more, more preferably 5 or more, and particularly preferably 10 or more. . Further, the aspect ratio of the plate-like particles is preferably 100 or less, and more preferably 50 or less.
The aspect ratio of the plate-like particles can be obtained by, for example, analyzing an image taken with a scanning electron microscope (SEM).

  The ratio of the inorganic particles in the inorganic particle layer 3 is preferably 70% by volume or more, more preferably 80% by volume or more, and particularly preferably 90% by volume or more. When the proportion of the inorganic particles in the inorganic particle layer 3 is 70% by volume or more, the heat shrinkage suppressing effect of the laminated film 2 due to the inorganic particle layer 3 being formed on the surface of the polyolefin microporous film 20 becomes remarkable. .

The inorganic particle layer 3 may contain a binder. The binder in the inorganic particle layer 3 contributes to adhesion between the inorganic particles contained in the inorganic particle layer 3, adhesion between the inorganic particles and other components, and adhesion between the inorganic particle layer 3 and the polyolefin microporous film 20.
As the binder contained in the inorganic particle layer 3, a conventionally known binder can be used, the electrochemical stability inside the electrochemical element is good, and the stability of the electrochemical element with respect to the electrolytic solution is good. It is preferable to use one.

  Specific examples of the binder contained in the inorganic particle layer 3 include an ethylene-vinyl acetate copolymer (EVA, one having a vinyl acetate-derived structural unit of 20 to 35 mol%), an ethylene-ethyl acrylate copolymer, and the like. Ethylene-acrylic acid copolymer, fluororesin [polyvinylidene fluoride (PVDF), etc.], fluorine-based rubber, styrene-butadiene rubber (SBR), carboxymethylcellulose (CMC), hydroxyethylcellulose (HEC), polyvinyl alcohol (PVA) Organic binders such as polyvinyl butyral (PVB), polyvinyl pyrrolidone (PVP), poly N-vinyl acetamide, acrylic resin, polyurethane, nylon, polyester, polyvinyl acetal, and epoxy resin are preferably used. A binder may be used individually by 1 type and may use 2 or more types together.

  As the binder, a (meth) acrylic acid ester copolymer having a structure obtained by polymerizing (meth) acrylic acid esters as a main component of the monomer is preferably used. In this specification, “(meth) acrylic acid” means at least one of acrylic acid and methacrylic acid.

  As the binder, among (meth) acrylic acid ester copolymers, those having a glass transition temperature (Tg) of −20 ° C. or lower are more preferable. As the (meth) acrylic acid ester copolymer having a Tg of −20 ° C. or less, the terminal of the side chain ester group is preferably an alkyl group having 2 to 10 carbon atoms, and more specifically, the side The above-mentioned copolymer in which the main terminal of the chain ester group is an n-propyl group, an iso-propyl group, an n-butyl group, a sec-butyl group, or an n-hexyl group is more preferable. If the carbon number of the terminal alkyl group of the side chain ester group is too small, the Tg of the binder becomes higher and the flexibility is lowered. Moreover, when there are too many carbon atoms of the terminal alkyl group of a side chain ester group, side chains will crystallize and the flexibility of a binder will fall on the contrary.

  As the binder, a heat resistant resin having a heat resistant temperature of 150 ° C. or higher may be used. As the heat-resistant resin having a heat-resistant temperature of 150 ° C. or higher, it is preferable to use a highly flexible resin such as an ethylene-acrylic acid copolymer, fluorine-based rubber, or SBR. Specific examples of the heat-resistant resin having a heat-resistant temperature of 150 ° C. or higher include EVA “Evaflex series (trade name)” manufactured by Mitsui DuPont Polychemical Co., Ltd., EVA manufactured by Nihon Unicar Co., Ltd., ethylene manufactured by Mitsui DuPont Polychemical Co., Ltd. Ethyl acrylate copolymer (EEA) "Evaflex-EEA series (trade name)", EEA made by Nihon Unicar, Fluororubber "Daiel Latex series (trade name)" by Daikin Industries, SBR made by JSR “TRD-2001 (product name)”, SBR “BM-400B (product name)” manufactured by Nippon Zeon Co., Ltd., and the like.

  The content of the binder in the inorganic particle layer 3 is preferably 0.5 parts by weight or more with respect to 100 parts by weight of the inorganic particles, from the viewpoint of more effectively exerting the action due to the use of the binder. More preferably, it is more preferably 2 parts by weight or more. Moreover, when there is too much content of the binder in the inorganic particle layer 3, the void | hole of the inorganic particle layer 3 will be filled up with a binder, and the permeability | transmittance of ion may fall, and there exists a possibility that the characteristic of an electrochemical element may appear badly. . From this, the content of the binder in the inorganic particle layer 3 is preferably 10 parts by weight or less, more preferably 7 parts by weight or less, and more preferably 5 parts by weight or less with respect to 100 parts by weight of the inorganic particles. It is particularly preferred.

(core)
The core 1 forming the laminated film roll 10 has a cylindrical shape. The material of the core 1 is not particularly limited, but is preferably formed of a material having high rigidity in order to suppress dimensional change. Specifically, the core 1 can be formed of resin and / or paper.

The outer diameter (diameter) of the core 1 is preferably 100 mm or more, more preferably 150 mm or more, and particularly preferably 200 mm or more. By increasing the outer diameter of the core 1, the number of the laminated films 2 wound around the core 1 when the length of the laminated film 2 is the same (hereinafter sometimes referred to as “the number of turns”) is reduced. Can do. As a result, the outer diameter of the laminated film roll 10 is likely to be uniform, and the difference ΔR ₁ between the maximum outer diameter D ₁ and the minimum outer diameter D _{2 in} the width direction is easily adjusted to the above range.

  On the other hand, if the outer diameter of the core 1 is too large, it becomes difficult to handle a wound body when the laminated film 2 unwound from the laminated film roll 10 is used as a separator, and the productivity may be reduced. For this reason, the outer diameter of the core 1 is preferably 500 mm or less, more preferably 450 mm or less, and particularly preferably 400 mm or less.

Moreover, in order to easily adjust ΔR ₁ in the laminated film roll 10 within the above range, it is preferable to use a core 1 having a small side cylindricity. Specifically, the cylindricity of the side surface of the core 1 is preferably 0.2 mm or less, and more preferably 0.1 mm or less.

"Production method of laminated film roll"
Next, as an example of the manufacturing method of the laminated film roll, the manufacturing method of the laminated film roll 10 shown in FIG. 1 will be described as an example.
In order to manufacture the laminated film roll 10, first, a microporous film roll around which the polyolefin microporous film 20 is wound is prepared. Then, the polyolefin microporous film 20 is unwound from the microporous film roll.
Next, the laminated film 2 is formed by forming the inorganic particle layer 3 on the polyolefin microporous film 20. Thereafter, the obtained laminated film 2 is wound around the cylindrical core 1. Thereby, the laminated film roll 10 is obtained.

When manufacturing the laminated film roll 10, the microporous film roll used as the material of the laminated film 2 includes a cylindrical core and a polyolefin microporous film 20 wound around the core. In the present embodiment, a microporous film roll having a difference ΔR ₂ between the maximum outer diameter and the minimum outer diameter in the width direction of 0.05 to 1.2 mm is used. As a result, the outer diameter of the laminated film roll 10 obtained by winding the laminated film 2 obtained by forming the inorganic particle layer 3 on the unrolled polyolefin microporous film 20 around the cylindrical core tends to be uniform. Become.

As a result of intensive studies by the present inventors, it has been found that the flatness of a microporous film roll comprising a cylindrical core and a polyolefin microporous film 20 wound around the core varies from lot to lot. Specifically, in the microporous film roll, the difference ΔR ₂ between the maximum outer diameter and the minimum outer diameter in the width direction is in the range of 0.05 to 1.2 mm, and the above Δ It has been found that there are cases where R ₂ is insufficient in flatness with an outer diameter exceeding 1.2 mm.

Therefore, the present inventors pay attention to the relationship between ΔR ₂ of the microporous film roll used as the material of the laminated film roll 10 and ΔR ₁ of the laminated film roll 10 produced using the same, and further study Advanced. As a result, when a microporous film roll having ΔR ₂ of 0.05 to 1.2 mm was used, it was produced as compared with a case of using a microporous film roll having ΔR ₂ exceeding 1.2 mm. It has been found that ΔR ₁ of the laminated film roll 10 becomes small.

This is because when △ R ₂ of the microporous film roll is 1.2mm or less, when unwinding polyolefin microporous film 20 of a microporous film roll, it becomes uniform tension applied to the polyolefin microporous film 20 This is presumably because the amount of sag of the polyolefin microporous film 20 resulting from unwinding is reduced. That is, when the amount of sag of the polyolefin microporous film 20 is small, it becomes easy to uniformly apply a coating liquid containing inorganic particles on the polyolefin microporous film 20, and the inorganic particle layer 3 having a uniform thickness can be obtained. Moreover, when the amount of sag of the polyolefin microporous film 20 is small, the laminated film 2 obtained by forming the inorganic particle layer 3 on the polyolefin microporous film 20 can be wound with high accuracy.

Furthermore, the present inventors have repeatedly studied to manufacture the laminated film roll 10 in which the difference ΔR ₁ between the maximum outer diameter D ₁ and the minimum outer diameter D _{2 in} the width direction is 0.05 to 1.5 mm. It was found that it was necessary to form the inorganic particle layer 3 with good flatness on the polyolefin microporous film 20.
The inorganic particle layer 3 is formed by applying a coating liquid containing inorganic particles on the polyolefin microporous film 20 unwound from the microporous film roll and drying it. In order to produce a laminated film roll 10 having ΔR ₁ of 0.05 to 1.5 mm, the present inventors have intensively studied, and as a material for the laminated film roll 10, ΔR ₂ is 1.2 mm or less. It has been found that the inorganic particle layer 3 having good flatness may be formed by using a porous film roll and a coating liquid having a surface tension smaller than the wetting index of the polyolefin microporous film 20. In this case, the laminated film 2 that has the inorganic particle layer 3 with good flatness and can be wound with high accuracy with little distortion is formed. Therefore, by winding up the laminated film 2, a laminated film roll 10 having ΔR ₁ of 0.05 to 1.5 mm is obtained.

When the surface tension of the coating liquid containing the inorganic particles used when forming the inorganic particle layer 3 is about the same as or smaller than the wetting index of the polyolefin microporous film 20, it is formed on the polyolefin microporous film 20. Since the coating liquid can be applied uniformly, the inorganic particle layer 3 with good flatness can be obtained.
Specifically, the surface tension of the coating liquid containing inorganic particles is preferably 35 mN / m or less, more preferably 33 mN / m or less, and particularly preferably 31 mN / m or less. Usually, the surface tension (wetting index) of the polyolefin microporous film 20 not subjected to hydrophilic treatment such as corona discharge treatment is about 31 to 34 mN / m, and is 35 mN / m or less. When the surface tension of the coating liquid is 31 mN / m or less, the surface tension of the coating liquid becomes a value equal to or less than the wetting index of the polyolefin microporous film 20, which is preferable.

  If the surface tension of the coating liquid containing inorganic particles is too low, the coating liquid may enter the pores of the polyolefin microporous film 20 to block the pores or escape to the opposite side of the polyolefin microporous film 20. Arise. For this reason, the surface tension of the coating liquid containing inorganic particles is preferably 15 mN / m or more, and more preferably 20 mN / m or more.

  For example, a coating liquid (aqueous coating liquid) in which inorganic particles are dispersed in a dispersion medium containing 70% by mass or more of water has a surface tension exceeding 35 mN / m, and the surface tension (wetting index) of the polyolefin microporous film The difference becomes larger. In this case, when the coating liquid is applied to the polyolefin microporous film, the coating liquid is repelled by the polyolefin microporous film. For this reason, it is difficult to uniformly apply the coating liquid to the polyolefin microporous film, and the inorganic particle layer formed by drying has insufficient flatness.

  As a method for preventing the coating liquid from being repelled on the polyolefin microporous film 20, a method of subjecting the polyolefin microporous film 20 to a surface treatment is also conceivable. For example, Patent Document 2 and Patent Document 3 describe a technique in which the surface of a polyolefin microporous film is subjected to corona discharge treatment, plasma treatment, or the like, so that the wettability of the polyolefin microporous film surface is 40 mN / m or more. Yes.

  However, if the surface treatment is excessively applied to the polyolefin microporous film 20, the polyolefin microporous film 20 is damaged by heat accompanying the surface treatment. The polyolefin microporous film that has been greatly damaged by excessive surface treatment may have a reduced mechanical strength, so it is preferable to perform an appropriate amount of surface treatment according to the surface tension of the coating liquid. .

The surface tension (wetting index (mN / m)) of the polyolefin microporous film 20 used in the present invention can be measured by a method based on Japanese Industrial Standard (JIS) K-6768.
The surface tension of the coating liquid can be measured by a conventionally known measurement method such as a plate method, a pendant drop method, or a maximum bubble pressure method.

  The surface tension of the coating liquid is, for example, a method of changing the type and content of the dispersion medium in the coating liquid, and a method of changing the type and content of the surfactant contained in the coating liquid as necessary. It can be adjusted by.

  The viscosity of the coating liquid containing the inorganic particles used when forming the inorganic particle layer 3 is 5 to 80 mPa · s, and preferably 10 to 50 mPa · s. When the viscosity of the coating liquid is 80 mPa · s or less, it becomes easy to uniformly apply a coating liquid containing inorganic particles on the polyolefin microporous film 20. For this reason, a coating film with good flatness is obtained by applying the coating liquid, and the inorganic particle layer 3 with good flatness is formed by drying the coating film. Therefore, the outer diameter of the laminated film roll 10 obtained by winding the laminated film 2 around a cylindrical core is likely to be uniform. On the other hand, when the viscosity of the coating liquid is 5 mPa · s or more, a coating film that becomes the inorganic particle layer 3 having a required thickness can be easily formed.

  The viscosity of the coating liquid is, for example, contained as needed, a method of changing the kind, shape, content, etc. of inorganic particles in the coating liquid, a method of changing the kind, content, etc. of the dispersion medium in the coating liquid. It can be adjusted by a method of changing the type and content of the binder and / or thickener.

The coating liquid applied on the polyolefin microporous film 20 contains the above inorganic particles. As the coating solution, for example, a solution obtained by dispersing or dissolving inorganic particles in a water-based or organic solvent-based medium (dispersion medium) can be used.
The coating liquid may contain the above binder, thickener, dispersant, surfactant and the like as necessary.

(Dispersion medium)
Examples of the dispersion medium include water, organic solvents (aromatic hydrocarbons such as toluene; furans such as tetrahydrofuran; ketones such as methyl ethyl ketone and methyl isobutyl ketone), and a mixed solvent of water and an organic solvent. The dispersion medium preferably contains 70% by mass or more of water, more preferably 90% by mass or more, and particularly preferably substantially only water.

(Thickener)
As the thickener, those that can be dissolved or dispersed satisfactorily with respect to the medium (dispersion medium) used in the coating liquid are preferably used. Moreover, as a thickener, it is preferable to use what has a high thickening effect | action with a small amount of content.

  As thickeners, cellulose derivatives such as carboxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose; natural polysaccharides such as xanthan gum, welan gum, gellan gum, guar gum, carrageenan; starches such as dextrin and pregelatinized starch; polyethylene glycol, polyacrylic Examples include acid, polyvinyl alcohol, polyvinyl pyrrolidone, poly N-vinylacetamide, vinyl methyl ether-maleic anhydride copolymer, and the like. These thickeners may be used individually by 1 type, and may use 2 or more types together.

Among the above thickeners, one or more selected from cellulose derivatives, natural polysaccharides, polyvinyl alcohol, polyvinyl pyrrolidone, and poly N-vinylacetamide are preferably used. These thickeners are preferable because they have high solubility in water and a high thickening effect can be obtained in a small amount.
Among the above thickeners, compounds that also have a function as a binder can be used as a binder that also serves as a thickener.

  The content of the thickener in the coating liquid is determined according to the viscosity of the coating liquid to be set. For example, the content of the thickener is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, and particularly preferably 3 parts by mass or less with respect to 100 parts by mass of the inorganic particles. . Moreover, in order to exhibit a sufficient thickening effect by including a thickener in a coating liquid, it is preferable that content of a thickener shall be 0.1 mass part or more.

(Dispersant)
The dispersant is used to disperse the inorganic particles in the dispersion medium. Dispersants include various anionic, cationic, and nonionic surfactants; polymer systems such as polycarboxylic acid, polyacrylic acid, polymethacrylic acid, polycarboxylate, polyacrylate, and polymethacrylate A dispersing agent; and the like can be used. A dispersing agent may be used individually by 1 type, and may use 2 or more types together.

  Among the above dispersants, since the action of dispersing inorganic particles in a dispersion medium is strong, an ion dissociable acid group (carboxyl group, sulfonic acid group, amino acid group, maleic acid group, etc.) or an ion dissociable acid Those containing a plurality of bases (such as carboxylate groups, sulfonate groups, and maleate groups) are preferred, and polycarboxylates, polyacrylates, and polymethacrylates are more preferred. When the polymer dispersant is a salt (having an acid base), an ammonium salt is preferable.

  Specifically, as the dispersant, “ADEKATO (product name) series”, “ADEKA NOL (product name) series” manufactured by ADEKA, “SN Dispersant (product name) series” manufactured by San Nopco, “Polity (product name) series”, “Armin (product name) series”, “Duomin (product name) series”, “Homogenol (product name) series”, “Leodoll (product name) series”, “ “Amito (trade name) series”, “Falback (trade name) series”, “Ceramisole (trade name) series”, “Polystar (trade name) series” manufactured by NOF Corporation, “Ajisper ( (Trade name) series ”,“ Aron dispersant (trade name) series ”manufactured by Toagosei Co., Ltd., and the like can be used.

  The content of the dispersant in the coating liquid is preferably 0.05 parts by mass or more and 0.1 parts by mass or more with respect to 100 parts by mass of the inorganic particles from the viewpoint of effectively exhibiting the action of the dispersant. It is more preferable that it is 0.3 mass part or more. When the coating liquid contains 0.05 parts by mass or more of the dispersant with respect to 100 parts by mass of the inorganic particles, the individual inorganic particles are sufficiently separated and dispersed in the coating liquid, and the inorganic particles A good dispersion state is maintained for a long time. For this reason, during the process of applying the coating liquid containing inorganic particles on the polyolefin microporous film 20, the state of the coating liquid does not change, and the inorganic particle layer 3 having more uniform and good flatness is obtained. It is done.

  On the other hand, if the content of the dispersing agent in the coating liquid is too large, not only the effect is saturated, but also the residual in the inorganic particle layer 3 formed by applying the coating liquid, and moisture in the inorganic particle layer 3. Adsorb. Moisture in the inorganic particle layer 3 is brought into the battery by using the laminated film 2 as a separator of an electrochemical element, and becomes a factor of deteriorating battery characteristics. For this reason, the content of the dispersant is preferably 2 parts by mass or less, more preferably 1 part by mass or less, and 0.8 parts by mass or less with respect to 100 parts by mass of the inorganic particles. Particularly preferred.

(Surfactant)
The surfactant is used to adjust the surface tension of the coating liquid. Examples of the surfactant include hydrocarbon surfactants, fluorine surfactants, silicone surfactants, and the like. Surfactant may be used individually by 1 type and may use 2 or more types together.

  Examples of hydrocarbon-based surfactants include anionic surfactants such as fatty acid salts, cholates, linear alkylbenzene sulfonate sodium and sodium lauryl sulfate; cationic surfactants such as tetraalkylammonium salts; And amphoteric surfactants having both an anionic site and a cationic site; and nonionic surfactants such as alkyl glucosides.

Examples of the fluorine-based surfactant include those in which a linear alkyl group, a perfluoroalkenyl group, etc. are arranged on a hydrophobic group (perfluorooctane sulfonic acid, perfluorocarboxylic acid, etc.).
Examples of the silicone surfactant include polydimethylsiloxane, polyether-modified polydimethylsiloxane, and polymethylalkylsiloxane.

  The content of the surfactant in the coating liquid is preferably such that the surface tension of the coating liquid is about the same as or smaller than the surface tension (wetting index) of the polyolefin microporous film 20. Specifically, the content of the surfactant is preferably 0.05 parts by mass or more, more preferably 0.07 parts by mass or more with respect to 100 parts by mass of the medium, and 0.1 mass by mass. Part or more is particularly preferable.

  When there is too much content of surfactant in a coating liquid, the adhesiveness of the polyolefin microporous film 20 and the inorganic particle layer 3 in the laminated film 2 will fall, for example, the peeling strength in 180 degrees will become a suitable value. It becomes difficult to become. When the adhesion between the polyolefin microporous film 20 and the inorganic particle layer 3 is lowered, there is a possibility that the effect of suppressing the thermal shrinkage of the laminated film 2 by the inorganic particle layer 3 becomes insufficient. Further, when the content of the surfactant in the coating liquid is too large, the coating liquid and / or medium passes through the pores of the polyolefin microporous film 20 to the surface opposite to the side on which the inorganic particle layer 3 is formed. Betrayal is likely to occur. When the strike-through occurs, the coating liquid and / or the dispersion medium wets a backup roll or the like of the apparatus for applying the coating liquid, the handling of the polyolefin microporous film 20 is lowered, and the coating liquid is not easily applied uniformly. Therefore, the content of the surfactant in the coating liquid is preferably 1.5 parts by mass or less, more preferably 1 part by mass or less, with respect to 100 parts by mass of the medium, and 0.5 parts by mass. More preferably, it is as follows.

  The coating liquid containing the inorganic particles used when forming the inorganic particle layer 3 is a known method, using inorganic particles and, if necessary, a binder, a thickener, a dispersant, a surfactant, and the like. Is dispersed or dissolved in a dispersion medium.

The inorganic particle layer 3 is formed by applying a coating liquid containing inorganic particles on the polyolefin microporous film 20 and drying it. Thereby, the laminated film 2 is formed.
Examples of the method for applying the coating liquid onto the polyolefin microporous film 20 include a method using a coating apparatus such as a gravure coater, a knife coater, a reverse roll coater, and a die coater.

  The drying conditions for drying the applied coating liquid may be any temperature lower than the melting point of the polyolefin forming the resin of the polyolefin microporous film 20. For example, in order to prevent shrinkage of the polyolefin microporous film 20 during drying, the drying temperature is preferably 150 ° C. or less, and more preferably 145 ° C. or less. On the other hand, the drying temperature is preferably 60 ° C. or higher, and more preferably 80 ° C. or higher in order to increase the drying efficiency and shorten the drying time.

  Next, the manufacturing apparatus of the laminated film roll 10 is demonstrated using drawing. FIG. 3 is a schematic view showing an example of a laminated film roll manufacturing apparatus. The manufacturing apparatus shown in FIG. 3 includes a coating device 41 for coating a coating liquid on the polyolefin microporous film 20, a drying device 42 for drying the polyolefin microporous film 20 coated with the coating liquid, and a laminated film obtained after drying. And a winding device that winds 2 around a cylindrical core 1.

In order to form the laminated film 2 using the manufacturing apparatus shown in FIG. 3, first, the polyolefin microporous film 20 is unwound from the microporous film roll 25. Next, a coating liquid containing inorganic particles is applied onto the polyolefin microporous film 20 by a coater as the coating device 41.
Thereafter, the polyolefin microporous film 20 coated with the coating liquid is transported to the drying zone of the drying device 42 and dried using dry air at a predetermined temperature to form the inorganic particle layer 3. It is formed.

Next, the formed laminated film 2 is wound around the cylindrical core 1 by a winding device. The method for winding the laminated film 2 around the core 1 is not particularly limited, and the winding is performed so that the difference ΔR ₁ between the maximum outer diameter D ₁ and the minimum outer diameter D _{2 in} the width direction is 0.05 to 1.5 mm. Winding conditions such as winding speed and tension can be appropriately controlled, and winding can be performed by a conventionally known method.
The laminated film roll 10 of this embodiment is obtained by the above process.

  The laminated film 2 unwound from the laminated film roll 10 of this embodiment can be used as a separator of an electrochemical element, for example. There is no restriction | limiting in particular as an electrochemical element which can apply the laminated film 2. FIG. For example, as an electrochemical element to which the laminated film 2 can be applied, various electrochemical elements having a non-aqueous electrolyte can be cited. Specific examples include lithium ion batteries (primary batteries and secondary batteries), polymer lithium batteries, and electric double layer capacitors. Among these, in particular, the laminated film 2 is suitable as a separator for an electrochemical element that is applied to uses that require safety at high temperatures.

A laminated film roll 10 of the present embodiment is obtained by winding a laminated film 2 having a polyolefin microporous film 20 and an inorganic particle layer 3 containing inorganic particles formed on the surface thereof around a core 1, and having a width. The difference ΔR ₁ between the maximum outer diameter D ₁ and the minimum outer diameter D _{2 in the} direction is 0.05 to 1.5 mm. For this reason, for example, when using the laminated film 2 unwound from the laminated film roll 10 as a separator and laminating the positive electrode and the negative electrode to form an electrode body, the amount of sag when unwinding the laminated film 2 is small, and the laminated film The tension applied to 2 becomes uniform. Therefore, positioning of the separator can be performed accurately. As a result, an electrode body in which the stacking deviation between the positive electrode and the negative electrode and the separator (laminated film 2) is suppressed is obtained. In particular, when the laminated film 2 unwound from the laminated film roll 10 is used as a separator and wound together with the positive electrode and the negative electrode to form a wound body, the separator, the positive electrode, and the negative electrode can be wound with high accuracy, and the winding deviation Can be suppressed. Therefore, the winding defect of the wound body due to the winding deviation can be sufficiently prevented, and the wound body can be produced with a high yield.

  The laminated film 2 wound around the laminated film roll 10 of the present embodiment has an inorganic particle layer 3 containing inorganic particles on the surface of the polyolefin microporous film 20. For this reason, heat resistance is favorable and it is suitable as a separator of an electrochemical element. Specifically, when the inside of the electrochemical device reaches a temperature equal to or higher than the melting point of the polyolefin resin forming the polyolefin microporous film 20, the thermal contraction of the laminated film 2 is suppressed by the inorganic particle layer 3. At the same time, a short circuit due to direct contact between the positive electrode and the negative electrode is prevented. Therefore, the electrochemical element using the laminated film 2 unwound from the laminated film roll 10 of this embodiment as a separator has excellent safety at high temperatures.

In the manufacturing method of the laminated film roll 10 of the present embodiment, a microporous film roll having a difference ΔR ₂ between the maximum outer diameter and the minimum outer diameter in the width direction of 0.05 to 1.2 mm is used. The inorganic particle layer 3 is formed using a coating liquid having a surface tension smaller than the wetting index of the porous film 20. For this reason, the laminated film 2 which has the inorganic particle layer 3 with favorable flatness and can be wound with high accuracy with little distortion is formed. Therefore, the laminated film roll 10 having ΔR ₁ of 0.05 to 1.5 mm is obtained by winding up the obtained laminated film 2.

  In the manufacturing method of the laminated film roll 10 of this embodiment, when forming the inorganic particle layer 3, when the coating liquid whose viscosity is 5-80 mPa * s is used, on the polyolefin microporous film 20, it is much more uniform. It becomes easy to apply the coating liquid. For this reason, the laminated film roll 10 which has a more uniform outer diameter is obtained.

The laminated film roll of the present invention is not limited to the laminated film roll 10 of the above-described embodiment. For example, the laminated film 2 unwound from the laminated film roll 10 may be used for producing the electrode body as it is, but after the laminated film 2 is slit to a width suitable for producing the electrode body, May be used. In this case, the laminated body 2 having a width suitable for the production of the electrode body may be wound once and used as a new laminated film roll.
In addition, since ΔR ₁ of the laminated film roll 10 is 0.05 to 1.5 mm, the laminated body 2 that is slit and has a width suitable for the production of the electrode body can be wound with high accuracy with little distortion. . Therefore, the new laminated film roll obtained by winding the laminated body 2 having a width suitable for the production of the electrode body tends to have a uniform outer diameter, and the difference ΔR between the maximum outer diameter and the minimum outer diameter in the width direction. ₃ is easy to adjust so that it may be 1.5 mm or less. The laminated film roll of the present invention includes a new laminated film roll wound up again as described above.

  Hereinafter, the present invention will be described in detail based on examples. However, the following examples do not limit the present invention.

Example 1
A microporous film roll was prepared in which a polyolefin microporous film having a three-layer structure shown below was wound around a cylindrical core. The difference ΔR ₂ between the maximum outer diameter and the minimum outer diameter in the width direction of the prepared microporous film roll was 0.8 mm. The difference ΔR ₂ between the maximum outer diameter and the minimum outer diameter in the width direction of the microporous film roll was measured by the method shown below.

"Three-layer polyolefin microporous film"
An intermediate layer made of polyethylene having a weight average molecular weight of about 390,000 and a thickness of 7.0 μm, and laminated on both sides of the intermediate layer, having a weight average molecular weight of about 650,000 (molecular weight distribution: 11) and a thickness of 5.5 μm It consists of an outer layer made of polypropylene.
(Total thickness: 18.0 μm, compression modulus: 122.4 MPa)

“Measuring method of ΔR ₂ ”
ΔR ₂ was determined using a measuring instrument 50 shown in FIG.
FIG. 4 is a schematic perspective view showing an example of a measuring instrument 50 that measures an outer shape change in the width direction of the roll. The measuring instrument 50 shown in FIG. 4 includes two contact-type shape sensors (linear gauges manufactured by Mitsutoyo) 52a and 52b, moving means 54a and 54b, and a guide 51.
The contact-type shape sensors 52 a and 52 b are disposed opposite to each other in contact with the outer surface of the roll 53 with the center of the roll 53 interposed therebetween. The moving means 54 a and 54 b support the two contact-type shape sensors 52 a and 52 b, respectively, and move the contact-type shape sensors 52 a and 52 b from the width direction one end 53 a to the other end 53 b along the outer shape of the roll 53. The guide 51 is provided along the outer surface of the roll 53 in the width direction of the roll 53, and supports the moving means 54 a and 54 b so as to be movable in the width direction of the roll 53.

Specifically, ΔR ₂ was determined by the following method using the measuring device 50 shown in FIG. The contact-type shape sensors 52a and 52b are moved along the outer shape of the roll 53 from the one end 53a in the width direction to the other end 53b by the moving means 54a and 54b, and the change in the outer diameter in the width direction of the roll 53 is continued over the entire width. And measured. The maximum outer diameter and the minimum outer diameter in the width direction were obtained from the measurement results, and ΔR ₂ , which is the difference between the maximum outer diameter and the minimum outer diameter, was calculated.

Moreover, the coating liquid containing an inorganic particle was obtained by disperse | distributing or dissolving the inorganic particle, binder, thickener, and surfactant which are shown below in the dispersion medium shown below in the ratio shown below.
The obtained coating liquid containing inorganic particles had a viscosity at 25 ° C. of 20 mPa · s and a surface tension of 30 mN / m.
The viscosity was measured using a tuning fork type vibration viscometer (SV-10) manufactured by A & D. The surface tension was measured using an automatic dynamic surface tension meter (DP-D) manufactured by Kyowa Interface Chemical Co., Ltd.

“Inorganic particles” boehmite powder (plate, average particle size 1 μm, aspect ratio 10), 100 parts by weight “binder” butyl acrylate-acrylic acid copolymer (Tg: −30 ° C.), 100 parts by weight of inorganic particles 3 parts by weight “Thickener” carboxymethylcellulose, 1 part by weight “surfactant” perfluorooctane sulfonic acid for 100 parts by weight of inorganic particles, 0.1 part by weight “dispersion medium” for 100 parts by weight of water water

The polyolefin microporous film having a three-layer structure is unwound from the microporous film roll, and the coating liquid containing the inorganic particles is applied to one side of the polyolefin microporous film by the coating device 41 of the manufacturing apparatus shown in FIG. It was applied and dried at 130 ° C. by a drying device 42 to form an inorganic particle layer having a thickness of 5 μm, thereby obtaining a laminated film.
Subsequently, the formed laminated film was wound around a resin-made cylindrical core having an outer diameter of 200 mm by a winding device of the manufacturing apparatus shown in FIG. 3 to obtain a laminated film roll having a width of 850 mm. The winding length of the laminated film in the laminated film roll was 6800 m.

(Example 2)
The same microporous film roll as in Example 1 was prepared.
Moreover, the coating liquid containing an inorganic particle was obtained by disperse | distributing or dissolving the following inorganic particle, thickener, and surfactant in the dispersion medium shown below in the ratio shown below.
About the coating liquid containing the obtained inorganic particle, the viscosity and surface tension were measured by the method similar to Example 1. FIG. As a result, the viscosity at 25 ° C. was 30 mPa · s, and the surface tension was 30 mN / m.

“Inorganic particles” boehmite powder (plate, average particle size 1 μm, aspect ratio 10), 100 parts by weight “Thickener” poly N-vinylacetamide, 1 part by weight “Thickener” for 100 parts by weight of inorganic particles Polyvinylpyrrolidone, 4 parts by mass “surfactant” perfluorooctane sulfonic acid with respect to 100 parts by weight of inorganic particles, 0.1 parts by mass “dispersion medium” water with respect to 100 parts by mass of water

A laminated film was obtained in the same manner as in Example 1 using the coating liquid containing the above inorganic particles and the same microporous film roll as in Example 1.
Thereafter, the formed laminated film was wound around the same core as in Example 1 by a winding device of the manufacturing apparatus shown in FIG. 3 to obtain a laminated film roll having a width of 680 mm. The winding length of the laminated film in the laminated film roll was 6000 m.

(Comparative Example 1)
A laminated film roll was obtained in the same manner as in Example 1 except that a microporous film roll having a difference ΔR ₂ between the maximum outer diameter and the minimum outer diameter in the width direction of 1.5 mm was used.
(Comparative Example 2)
The content of carboxymethyl cellulose contained in the coating liquid containing inorganic particles is 5 parts by mass with respect to 100 parts by weight of the inorganic particles, and the viscosity of the coating liquid containing inorganic particles is 90 mPa · s and the surface tension is 30 mN / m. A laminated film roll was obtained in the same manner as in Example 1 except that those were used.

Differences for laminated film roll of Examples 1-2 and Comparative Examples 1-2 were prepared in the same manner as △ R ₂ of the microporous film roll, the maximum outer diameter D ₁ and the minimum outer diameter D ₂ in the widthwise direction ΔR ₁ was measured. The results are shown in Table 1.
Moreover, by the method mentioned above, about the laminated film roll of Examples 1-2 and Comparative Examples 1-2, the dispersion | variation in the thickness of the inorganic particle layer in the width direction and the dispersion | variation in the fabric weight of the inorganic particle layer in the width direction are carried out. It was measured. The results are shown in Table 1.

Using the produced laminated film rolls of Examples 1 and 2 and Comparative Examples 1 and 2, lithium ion secondary batteries were produced as follows.
The laminated film was unwound from the laminated film roll and slit to a width of 60 mm. Then, a laminated film having a width of 60 mm is wound around a winding core together with a positive electrode (width 57 mm, length 680 mm) and a negative electrode (width 58 mm, length 700 mm) for a lithium ion secondary battery, and a cylindrical battery (size: diameter) A wound body for 18 mm and length 65.0 mm (18650 type) was produced. The winding length of the laminated film was 790 mm.

For each of Examples 1 and 2 and Comparative Examples 1 and 2, 1000 wound bodies were prepared and inserted into a cylindrical battery can to assemble a lithium ion secondary battery. I investigated. The results are shown in Table 1.
In addition, the thing which produced the insertion defect of the winding body at the time of battery assembly, and the thing which produced the short circuit in the battery after an assembly were judged as the assembly defect.

As shown in Table 1, in Examples 1 and 2 where ΔR ₁ is 1.5 mm or less, there is no assembly failure, and in comparison with Comparative Examples 1 and 2 where ΔR ₁ exceeds 1.5 mm, Assembly failure was suppressed.
The occurrence of assembly failure in Comparative Examples 1 and 2 was caused by unwinding the laminated film from the laminated film roll with ΔR ₁ exceeding 1.5 mm. This is considered to be due to the fact that sufficient accuracy could not be ensured in the process of winding the laminated film as a separator around the winding core together with the positive electrode and the negative electrode.

DESCRIPTION OF SYMBOLS 1 ... Core, 2 ... Laminated film, 3 ... Inorganic particle layer, 10 ... Laminated film roll, 20 ... Polyolefin microporous film, 21 ... Polyethylene layer, 22 ... Polypropylene Layer, 41 ... coating device, 42 ... drying device, 50 ... measuring instrument, 51 ... guide, 52a, 52b ... contact type sensor, 53 ... roll, 54a, 54b ..Movement means, D ₁ ... Maximum outer diameter, D ₂ .

Claims (9)

It consists of a cylindrical core and a laminated film wound around the core,
The difference ΔR ₁ between the maximum outer diameter and the minimum outer diameter in the width direction is 0.05 to 1.5 mm,
The laminated film roll comprising a polyolefin microporous film and an inorganic particle layer containing inorganic particles formed on the surface thereof.   The laminated film roll according to claim 1, wherein the inorganic particle layer has a thickness variation in the width direction of 0.8 μm or less. The laminated film roll according to claim 1, wherein a variation in the basis weight of the inorganic particle layer is 0.6 g / m ² or less. The inorganic particle layer is formed by drying a coating liquid containing inorganic particles,
The surface tension of the said coating liquid is 35 mN / m or less, The laminated film roll as described in any one of Claims 1-3 characterized by the above-mentioned.   The laminated film roll according to any one of claims 1 to 4, wherein the polyolefin microporous film has a wetting index of 35 mN / m or less. It is a manufacturing method of the lamination film roll according to any one of claims 1 to 5,
A core of cylindrical shape, made of a polyolefin microporous film wound on the core, the difference △ R ₂ between the maximum outer diameter and the minimum outer diameter in the width direction, a microporous film which is a 0.05~1.2mm Unwinding the polyolefin microporous film from a roll;
A step of forming a laminated film by applying a coating liquid containing inorganic particles and having a viscosity of 5 to 80 mPa · s on the polyolefin microporous film and drying to form an inorganic particle layer;
And a step of winding the laminated film around a cylindrical core.   The method for producing a laminated film roll according to claim 6, wherein a surface tension of the coating liquid is not more than a wetting index of the polyolefin microporous film.   The surface tension of the said coating liquid is 35 mN / m or less, The manufacturing method of the laminated film roll of Claim 6 or Claim 7 characterized by the above-mentioned.   The method for producing a laminated film roll according to any one of claims 6 to 8, wherein the polyolefin microporous film has a wetting index of 35 mN / m or less.

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