JP7375850B2 - Adhesive film for metal terminals and batteries - Google Patents

Description

The present invention relates to an adhesive film for metal terminals and a battery.

Conventionally, various types of batteries have been developed, and packaging materials have become essential components for sealing battery elements such as electrodes and electrolytes in all batteries. Traditionally, metal packaging materials were often used for battery packaging, but in recent years, with the increasing performance of electric vehicles, hybrid electric vehicles, computers, cameras, mobile phones, etc., batteries are now required to have a variety of shapes. At the same time, there is a demand for thinner and lighter weight devices. However, metal packaging materials, which have been widely used in the past, have the disadvantage that it is difficult to keep up with the diversification of shapes, and there is also a limit to the reduction in weight.

Therefore, in recent years, film-like packaging materials in which a base layer, an adhesive layer, a barrier layer, and a heat-fusible resin layer are sequentially laminated have been developed as a packaging material that can be easily processed into various shapes and can be made thinner and lighter. Laminated bodies have been proposed. When using such a film-like packaging material, by heat-sealing the periphery of the packaging material with the heat-fusible resin layers located in the innermost layer of the packaging material facing each other, , the battery element is sealed with the packaging material.

A metal terminal protrudes from the heat-sealed portion of the packaging material, and the battery element sealed with the packaging material is electrically connected to the outside through the metal terminal electrically connected to the electrode of the battery element. That is, among the heat-sealed portions of the packaging material, the portions where the metal terminals are present are heat-sealed with the metal terminals sandwiched between the heat-fusible resin layers. Since the metal terminal and the heat-fusible resin layer are made of different materials, adhesion tends to decrease at the interface between the metal terminal and the heat-fusible resin layer.

For this reason, an adhesive film is sometimes disposed between the metal terminal and the heat-fusible resin layer for the purpose of increasing the adhesion between them.

JP2015-79638A

Such an adhesive film is required not only to have high adhesion to the packaging material and the metal terminal, but also to have excellent resistance to the electrolyte sealed by the packaging material.

Under these circumstances, the main object of the present invention is to provide an adhesive film for metal terminals that has high adhesion to packaging materials and metal terminals and also has excellent electrolyte resistance. Furthermore, another object of the present invention is to provide a battery using the adhesive film for metal terminals.

The present inventors conducted extensive studies to solve the above problems. As a result, an adhesive film for metal terminals, which is interposed between a metal terminal electrically connected to an electrode of a battery element and a packaging material for sealing the battery element, is provided. is composed of a laminate including at least one polypropylene layer and at least one acid-modified polypropylene layer, and the acid-modified polypropylene layer covers the surface layer of at least one side of the adhesive film for metal terminals. The polypropylene layer has a sea-island structure when its cross section is observed with an electron microscope, and when the total thickness of the acid-modified polypropylene layer is 1, the total thickness of the polypropylene layer is 0. It has been found that an adhesive film for metal terminals having a value in the range of .7 or more and 3.5 or less has high adhesion to the packaging material and the metal terminal, and is also excellent in electrolyte resistance. The present invention was completed through further studies based on this knowledge.

That is, the present invention provides the inventions of the following aspects.
Item 1. An adhesive film for a metal terminal that is interposed between a metal terminal electrically connected to an electrode of a battery element and a packaging material that seals the battery element,
The adhesive film for metal terminals is composed of a laminate including at least one polypropylene layer and at least one acid-modified polypropylene layer,
The acid-modified polypropylene layer constitutes a surface layer on at least one side of the adhesive film for metal terminals,
When the cross section of the polypropylene layer was observed using an electron microscope, a sea-island structure was observed,
An adhesive film for a metal terminal, wherein the total thickness of the acid-modified polypropylene layers is 1, and the total thickness of the polypropylene layers is in the range of 0.7 or more and 3.5 or less.
Item 2. Item 2. The adhesive film for metal terminals according to Item 1, wherein the polypropylene layer contains block polypropylene.
Item 3. Item 3. The adhesive film for metal terminals according to item 1 or 2, wherein the polypropylene layer is made of unstretched polypropylene.
Item 4. Items 1 to 3, wherein the polypropylene layer has a laminated structure in which a layer made of random polypropylene, a layer made of block polypropylene, and a layer made of random polypropylene are laminated in this order. The adhesive film for metal terminals according to any one of the above.
Item 5. Item 5. The adhesive film for metal terminals according to any one of Items 1 to 4, wherein a melting peak is observed in a range of 150° C. or higher and 165° C. or lower when the adhesive film for metal terminals is measured with a differential scanning calorimeter. .
Item 6. Item 6. The adhesive film for metal terminals according to any one of Items 1 to 5, wherein the adhesive film for metal terminals has a thickness residual rate of 50% or more as measured by the following measuring method.
An aluminum plate with a thickness of 100 μm and the adhesive film for metal terminals are prepared.
The thickness A (μm) of the adhesive film for metal terminals is measured.
The adhesive film for metal terminals is stacked on the center portion of the aluminum plate so that the length direction and the width direction of the aluminum plate and the adhesive film for metal terminals are aligned.
Prepare two metal plates that are longer than the length of the aluminum plate and have a width of 7 mm, and cover the entire surface of the adhesive film for metal terminals. The metal plate is heated and pressurized under the conditions of 190° C., surface pressure of 1.27 MPa, and time of 3 seconds to obtain a laminate of the aluminum plate and the metal terminal adhesive film.
The thickness B (μm) of the heated and pressurized portion of the laminate is measured.
The remaining thickness of the adhesive film for metal terminals is calculated using the following formula.
Thickness residual rate (%) of adhesive film for metal terminals = (Thickness B-100) / Thickness A x 100
Section 7. Item 7. The adhesive film for metal terminals according to any one of items 1 to 6, wherein the adhesive film for metal terminals has a heat shrinkage rate of 70 to 90% in the machine direction.
Section 8. The packaging material is composed of a laminate including at least a base layer, a barrier layer, and a heat-fusible resin layer in this order,
Item 8. The adhesive film for metal terminals according to any one of Items 1 to 7, wherein the adhesive film for metal terminals is interposed between the heat-fusible resin layer and the metal terminal.
Item 9. A battery element comprising at least a positive electrode, a negative electrode, and an electrolyte, a packaging material for sealing the battery element, and a metal terminal electrically connected to each of the positive electrode and the negative electrode and protruding outside the packaging material. A battery comprising:
A battery, wherein the adhesive film for metal terminals according to any one of Items 1 to 8 is interposed between the metal terminals and the packaging material.
Item 10. Use of a laminate comprising at least one polypropylene layer and at least one acid-modified polypropylene layer,
The acid-modified polypropylene layer constitutes a surface layer on at least one side of the adhesive film for metal terminals,
When the cross section of the polypropylene layer was observed using an electron microscope, a sea-island structure was observed,
When the total thickness of the acid-modified polypropylene layer is 1, the total thickness of the polypropylene layer is within a range of 0.7 or more and 3.5 or less,
Use of the laminate as an adhesive film for a metal terminal, which is interposed between a metal terminal electrically connected to an electrode of a battery element and a packaging material for sealing the battery element.

According to the present invention, it is possible to provide an adhesive film for metal terminals that has high adhesion to packaging materials and metal terminals, and also has excellent electrolyte resistance. Furthermore, according to the present invention, it is also possible to provide a battery using the adhesive film for metal terminals.

1 is a schematic plan view of a battery of the present invention; FIG. 2 is a schematic cross-sectional view taken along line AA' in FIG. 1. FIG. 2 is a schematic cross-sectional view taken along line BB' in FIG. 1. FIG. FIG. 1 is a schematic cross-sectional view of the adhesive film for metal terminals of the present invention. FIG. 1 is a schematic cross-sectional view of the adhesive film for metal terminals of the present invention. FIG. 2 is a schematic cross-sectional view of a packaging material used in the battery of the present invention. FIG. 3 is a schematic diagram for explaining a method of measuring seal strength in an example. FIG. 3 is a schematic diagram for explaining a method of measuring seal strength in an example. FIG. 3 is a schematic diagram for explaining a method of measuring seal strength in an example. FIG. 3 is a schematic diagram for explaining a method of measuring seal strength in an example. "Polymer microphotograph collection - Polymers seen with the naked eye 1. Shape and function of molecular assembly" (Editor: Japan Society of Polymer Science, Publisher: Yamamoto, Publisher: Baifukan Co., Ltd., first published on May 30, 1986) This is a transmission electron micrograph (scale bar is 5 μm) shown as “C” on page 29 of the publication.

The adhesive film for metal terminals of the present invention is an adhesive film for metal terminals that is interposed between a metal terminal electrically connected to an electrode of a battery element and a packaging material that seals the battery element. The adhesive film for metal terminals is composed of a laminate including at least one polypropylene layer and at least one acid-modified polypropylene layer, and the acid-modified polypropylene layer has the adhesive property for metal terminals. The polypropylene layer constitutes the surface layer on at least one side of the film, and when a cross section of the polypropylene layer is observed using an electron microscope, a sea-island structure is observed, and when the total thickness of the acid-modified polypropylene layer is 1, It is characterized in that the total thickness of the layers is within a range of 0.7 or more and 3.5 or less. Hereinafter, the adhesive film for metal terminals of the present invention and the battery of the present invention using the same will be described in detail.

In this specification, the numerical range indicated by "~" means "more than" or "less than". For example, the expression 2 to 15 mm means 2 mm or more and 15 mm or less.

1. Adhesive film for metal terminals The adhesive film for metal terminals of the present invention is interposed between a metal terminal electrically connected to an electrode of a battery element and a packaging material for sealing the battery element. . Specifically, as shown in FIGS. 1 to 3, for example, the adhesive film 1 for metal terminals of the present invention attaches a metal terminal 2 electrically connected to an electrode of a battery element 4 and a battery element 4. It is interposed between the packaging material 3 to be sealed. Further, the metal terminal 2 protrudes to the outside of the packaging material 3, and is held between the packaging material 3 via the metal terminal adhesive film 1 at the peripheral edge 3a of the heat-sealed packaging material 3. In the present invention, the heat when heat-sealing the packaging material is usually in the range of about 160 to 220°C, and the pressure is usually in the range of about 0.5 to 2.0 MPa.

The adhesive film 1 for metal terminals of the present invention is provided to enhance the adhesion between the metal terminals 2 and the packaging material 3. By increasing the adhesion between the metal terminals 2 and the packaging material 3, the sealing performance of the battery element 4 is improved. As described above, when heat sealing the battery element 4, the battery element is sealed in such a way that the metal terminal 2 electrically connected to the electrode of the battery element 4 protrudes outside the packaging material 3. . At this time, the metal terminal 2 made of metal and the heat-fusible resin layer 34 (layer formed of heat-fusible resin such as polyolefin) located at the innermost layer of the packaging material 3 are made of different materials. Therefore, if an adhesive film is not used, the sealing performance of the battery element tends to deteriorate at the interface between the metal terminal 2 and the heat-fusible resin layer 34. Furthermore, even when an adhesive film is used, if the adhesive film has low electrolyte resistance, the sealing performance of the battery element tends to be low.

For example, as shown in FIGS. 4 and 5, the adhesive film 1 for metal terminals of the present invention is composed of a laminate including at least one polypropylene layer 11 and at least one acid-modified polypropylene layer 12. The acid-modified polypropylene layer 12 constitutes the surface layer on at least one side of the adhesive film 1 for metal terminals, and when the cross section of the polypropylene layer 11 is observed with an electron microscope, a sea-island structure is observed; , when the total thickness of the acid-modified polypropylene layer 12 is 1, the total thickness of the polypropylene layer 11 is set within the range of 0.7 to 3.5. As a result, the adhesive film 1 for metal terminals of the present invention has high adhesion to packaging materials and metal terminals, and also has excellent electrolyte resistance, so it effectively improves the sealing performance of battery elements. be able to.

From the viewpoint of further improving the electrolyte resistance while further increasing the adhesion with the packaging material and the metal terminal, the total thickness of the polypropylene layer 11 when the total thickness of the acid-modified polypropylene layer 12 is 1. is preferably within the range of about 0.75 to 3.2, more preferably within the range of about 0.8 to 2.0.

In the adhesive film for metal terminals 1 of the present invention, the acid-modified polypropylene layer 12 constitutes the surface layer on at least one side of the adhesive film for metal terminals. The acid-modified polypropylene layer 12 made of acid-modified polypropylene has better adhesion to metal materials than the polypropylene layer 11 made of polypropylene. Therefore, by arranging the adhesive film 1 for metal terminals of the present invention between the metal terminals 2 and the packaging material 3 so that the acid-modified polypropylene layer 12 is located on the metal terminal 2 side, the battery element Sealing performance can be effectively improved.

The adhesive film 1 for metal terminals of the present invention only needs to include at least one polypropylene layer 11 and at least one acid-modified polypropylene layer 12, respectively. Preferred laminated configurations of the adhesive film 1 for metal terminals of the present invention include, for example, a configuration in which one polypropylene layer 11 and one acid-modified polypropylene layer 12 are laminated, as shown in FIG. As shown, examples include a structure in which one acid-modified polypropylene layer 12 is laminated on both sides of a polypropylene layer 11. As described later, one polypropylene layer 11 has a plurality of layers made of the same or different polypropylene laminated in succession, and even if the plurality of layers constitute one polypropylene layer 11, good. Similarly, one acid-modified polypropylene layer 12 has a plurality of consecutively laminated layers made of the same or different acid-modified polypropylene, and the plurality of layers constitute one acid-modified polypropylene layer 12. You can leave it there.

Specific examples of preferable laminated structures of the adhesive film 1 for metal terminals of the present invention include a two-layer structure of acid-modified polypropylene layer 12/polypropylene layer 11; Examples include a three-layer structure in which acid-modified polypropylene layer 12 / polypropylene layer 11 / acid-modified polypropylene layer 12 / polypropylene layer 11 / acid-modified polypropylene layer 12 are laminated in this order; Among these, a two-layer structure of acid-modified polypropylene layer 12/polypropylene layer 11 and a three-layer structure in which acid-modified polypropylene layer 12/polypropylene layer 11/acid-modified polypropylene layer 12 are laminated in this order are more preferable.

It is preferable that all layers of the adhesive film 1 for metal terminals of the present invention are composed of polyolefin. More specifically, the adhesive film 1 for metal terminals of the present invention preferably includes only the acid-modified polypropylene layer 12 and the polypropylene layer 11, and further includes another polyolefin layer composed of polyolefin. It is also preferable that Specific examples of the polyolefin constituting the polyolefin layer include polyethylene, acid-modified polyethylene, and the like. In the acid-modified polyethylene, the component for acid-modifying ethylene is not particularly limited, but includes, for example, unsaturated carboxylic acids or anhydrides thereof used for acid modification as exemplified in the acid-modified polypropylene layer 12 described below.

The thickness of the adhesive film 1 for metal terminals of the present invention is not particularly limited, but from the viewpoint of further improving the electrolyte resistance while further increasing the adhesion to the packaging material and the metal terminal, it is preferably 40 mm. -200 μm, more preferably about 55-150 μm, still more preferably about 60-110 μm.

Moreover, from the viewpoint of further improving the electrolyte resistance while further increasing the adhesion with the packaging material and the metal terminal, when the adhesive film 1 for metal terminals of the present invention was measured with a differential scanning calorimeter, Preferably, a melting peak is observed in the range of 150 to 165°C.

Further, from the same viewpoint, it is preferable that the adhesive film for metal terminals 1 of the present invention has a thickness residual rate of about 50% or more as measured by the following measuring method, It is preferably about 55% or more, and preferably about 60% or more. The upper limit of the thickness remaining rate is preferably about 90% or less, preferably about 85% or less, and preferably about 80% or less. The range of the thickness residual rate is preferably about 55 to 90%, about 55 to 85%, about 55 to 80%, about 60 to 90%, about 60 to 85%, and about 60 to 80%. It will be done. By using the adhesive film 1 for metal terminals having a residual rate of 50% or more, short circuit between the barrier layer contained in the packaging material and the metal terminal can be effectively suppressed, and the packaging material and the metal It becomes possible to further improve the adhesion with the adhesive film for terminals. Furthermore, by using the adhesive film 1 for metal terminals having a residual rate of 90% or less, it is possible to suitably follow the shape of the step of the metal terminal, and it is also possible to suitably cover the ends of the metal terminal. I can do it.

(Measurement of remaining thickness of adhesive film for metal terminals)
An aluminum plate (pure aluminum, JIS H4160-1994 A1N30H-O) with a thickness of 100 μm and an adhesive film for metal terminals are prepared. The thickness A (μm) of the adhesive film for metal terminals is measured with a microgauge. The adhesive film for metal terminals is placed over the center of the aluminum plate so that the length and width directions of the aluminum plate and the adhesive film for metal terminals are aligned. At this time, the acid-modified polypropylene layer of the adhesive film for metal terminals and the aluminum plate are arranged so as to be in contact with each other. Prepare two metal plates that are longer than the length of the aluminum plate and have a width of 7 mm, cover the entire surface of the adhesive film for metal terminals, and heat them at a temperature of 190°C from above and below the aluminum plate and the adhesive film for metal terminals. Heating and pressing are performed under conditions of a pressure of 1.27 MPa and a time of 3 seconds to obtain a laminate of an aluminum plate and an adhesive film for metal terminals. The thickness B (μm) of the heated and pressurized portion of the laminate is measured using a microgauge. The remaining thickness of the adhesive film for metal terminals is calculated using the following formula.
Thickness residual rate (%) of adhesive film for metal terminals = (Thickness B-100) / Thickness A x 100
Note that the length direction is a longitudinal direction corresponding to the long side of the object in plan view, and the width direction is a short direction corresponding to the short side of the object in plan view. If the sizes in the length direction and width direction are the same (square), either direction may be taken as the length direction or the width direction.

In addition, when measuring the residual rate, depending on the area of the adhesive film for metal terminals, it is also possible to measure by applying a pressure load so that the surface pressure becomes 1.27 MPa. Specifically, it can be converted using the following formula: [Pressure load (N) by metal plate]/[Area (mm ² ) of pressurizing adhesive film for metal terminal] = Surface pressure (MPa). Note that the pressure load (N) applied by the metal plate can be adjusted by adjusting the diameter and air pressure of the cylinder that adjusts the pressure of the metal plate.

In measuring the thickness residual rate of the adhesive film for metal terminals described above, if the measurement is performed under the conditions of temperature 190°C, surface pressure 1.27 MPa, and time 3 seconds, the length of the adhesive film for metal terminals and the aluminum plate is For example, if the adhesive film for metal terminals is 70 mm long and 5 mm wide and can be measured (methods such as cutting may be used), the adhesive film for metal terminals of this size is not limited. Using the film and an aluminum plate having a length of 60 mm and a width of 25 mm, the remaining thickness of the adhesive film for metal terminals can be suitably measured. In addition, [Area (mm ² ) to press the adhesive film for metal terminals] is the area of the overlapped portion of the aluminum plate and the adhesive film for metal terminals, and for example, the adhesive film for metal terminals of these sizes If a film and an aluminum plate are used, the area will be 60 mm x 5 mm. Moreover, the thickness of the aluminum plate does not substantially change due to heating and pressurization when obtaining a laminate of the aluminum plate and the adhesive film for metal terminals. Even if the sizes of the adhesive films for metal terminals to be measured are different, as long as the above measurements can be made, there is no need to change the size of the aluminum plate.

The melt mass flow rate (MFR) of the entire adhesive film 1 for metal terminals of the present invention is not particularly limited, but the viewpoint is to further improve the electrolyte resistance while further increasing the adhesion to the packaging material and the metal terminal. , preferably about 1 to 15, more preferably about 2 to 12, and still more preferably about 3 to 10. The melt mass flow rate (MFR) of the entire adhesive film 1 for metal terminals is a value measured using a melt indexer at a measurement temperature of 230 ° C. and a load of 2.16 kg, according to a method compliant with the provisions of JIS K7210:2014. It is.

Further, the lower limit of the heat shrinkage rate (%) in the machine direction (MD) of the adhesive film 1 for metal terminals of the present invention is preferably about 70% or more, more preferably about 75% or more, and even more preferably about The upper limit is preferably about 95% or less, more preferably about 92% or less, still more preferably about 90% or less. Further, the range of the heat shrinkage rate (%) is preferably about 70 to 95%, about 70 to 92%, about 70 to 90%, about 75 to 95%, about 75 to 92%, 75 to 90%. %, about 80-95%, about 80-92%, and about 80-90%. The method for measuring the heat shrinkage rate (%) is as follows.

(Method of measuring heat shrinkage rate (%))
The adhesive film for metal terminals is cut into a size of 50 mm length (MD) x width 4 mm (TD) to prepare a test piece. Next, the length M (mm) of the test piece is measured using a metal ruler. Next, the longitudinal ends of the test piece are fixed to the wire mesh with tape, and the test piece is suspended from the wire mesh. In this state, the test piece was placed in an oven heated to 190° C. for 120 seconds, and then the test piece was taken out together with the wire gauze and allowed to cool naturally at room temperature (25° C.). Next, the length N (mm) of the test piece that has been naturally cooled to room temperature is measured using a metal ruler. The heat shrinkage rate of the adhesive film for metal terminals is calculated using the formula below.
Heat shrinkage rate (%) = (length N/length M) x 100

In addition, when sealing a battery element, if the adhesive film for metal terminals is heat-sealed while being sandwiched between the metal terminal and the packaging material, the pressure from the metal plate used for heat-sealing There are parts where the adhesive film for metal terminals does not change in size, and parts where pressure is not applied due to the distance from the metal plate and it contracts. At this time, even the portions to which pressure is not applied are appropriately thermally contracted toward the portions to which pressure is applied, thereby effectively preventing the thickness of the portions to which pressure is applied from becoming too thin. On the other hand, if the heat shrinkage of the adhesive film for metal terminals is too large, the adhesive film 1 for metal terminals is installed on top of the metal terminals, and the adhesive film for metal terminals There is a possibility that the adhesive film moves due to heat shrinkage, causing a shift in the positional relationship between the metal terminal and the adhesive film for metal terminal. Therefore, it is desirable that the adhesive film 1 for metal terminals of the present invention has an appropriate heat shrinkage rate. In addition, as an appropriate heat shrinkage rate of the adhesive film 1 for metal terminals of the present invention, for example, the lower limit of the heat shrinkage rate (%) in the machine direction (MD) mentioned above is 70% or more. It will be done.

(Polypropylene layer 11)
In the present invention, the polypropylene layer 11 is a layer made of polypropylene. Further, when the cross section of the polypropylene layer 11 is observed using an electron microscope, a sea-island structure is observed. Observation of a sea-island structure in the cross section of the polypropylene layer 11 means that a sea portion and an island portion are observed, for example, as in the electron micrograph shown in FIG. 11. Figure 11 is "Polymer microphotograph collection: Polymers seen with the naked eye 1. Shape and function of molecular assembly" (editor: The Society of Polymer Science and Technology, publisher: Yamamoto, publisher: Baifukan Co., Ltd., May 1986) This is a transmission electron micrograph (scale bar is 5 μm) shown as “C” on page 29 of the first edition published on March 30th. The sea-island structure in the cross section of the polypropylene layer 11 can be confirmed by staining the cross section of the polypropylene layer with osmium tetroxide (OsO ₄ ) and observing an electron micrograph, as shown in FIG. In addition, although the sea part is brighter than the island part in FIG. 11, depending on the measurement method and conditions, the sea part may appear darker than the island part. In any case, if the sea part and the island part can be distinguished, the area ratio of the island part in the sea-island structure can be measured.

In the sea-island structure of the polypropylene layer 11, the area ratio of the island portion is not particularly limited, but from the viewpoint of further improving the electrolyte resistance while further increasing the adhesion with the packaging material and the metal terminal, Preferably it is about 10 to 50%, more preferably about 20 to 40%. The method for measuring the area ratio of island portions in the sea-island structure of the polypropylene layer 11 is as follows. Note that if the area ratio of the island portion is 2% or less, it is evaluated that the island substantially does not have a sea-island structure.

(Method for measuring the area ratio of island parts in sea-island structure)
An adhesive film for metal terminals is embedded in a thermosetting epoxy resin and cured. A cross section in the desired direction (cross section along TD) was prepared using a commercially available rotary microtome (UC6 manufactured by LEICA) and a diamond knife. Cross sections are prepared at ℃. Stain the embedding resin overnight with ruthenium tetroxide. When dyed, the polypropylene expands, so the expanded portion is trimmed with a microtome, and the section, which is approximately 100 nm thick and further cut by approximately 1 to 2 μm, is observed as follows. The stained cross section was observed with a field emission scanning electron microscope (for example, Hitachi High-Technologies S-4800 TYPE1, measurement conditions: 3kV 20mA High WD6mm detector (Upper)) and an image (magnification: 10,000x) was obtained. get. Next, using image processing software that can binarize images (for example, image analysis software WinROOF (Ver. 7.4) manufactured by Mitani Shoji Co., Ltd.), the island part and the sea part of the sea-island structure are binarized for the image. , the ratio of the area occupied by the island portion (total area of the island portion/area of the measurement range of the image) is determined.As for specific image processing conditions, for example, the conditions described in Examples are adopted.

A sea-island structure is observed when the cross section of the polypropylene layer 11 is observed using an electron microscope photograph, thereby increasing the cold resistance strength while maintaining the excellent heat resistance of the adhesive film for metal terminals. Further, the adhesion between the packaging material and the metal terminal is improved, and the electrolyte resistance is also improved.

Further, in the present invention, it is preferable that the polypropylene layer 11 is made of unstretched polypropylene. The fact that the polypropylene layer 11 is made of unstretched polypropylene and not drawn polypropylene can be confirmed by analyzing the polypropylene layer 11 using an X-ray diffraction method. Specifically, when wide-angle X-ray diffraction of the polypropylene layer 11 made of unstretched polypropylene is measured, the intensity of the peak corresponding to the 040 plane calculated from the diffraction pattern of the polypropylene crystal corresponds to the 110 plane of the polypropylene crystal. The peak intensity ratio (peak intensity of 040 plane/peak intensity of 110 plane) falls within the range of 0.5 to 1.5, and the polypropylene layer composed of stretched polypropylene falls outside this range. That is, in the present invention, when wide-angle X-ray diffraction is measured, the polypropylene layer 11 has a ratio of the intensity of the peak corresponding to the 110 plane of the polypropylene crystal to the intensity of the peak corresponding to the 040 plane calculated from the diffraction pattern of the polypropylene crystal ( It is made of polypropylene in which the peak intensity of the 040 plane/the peak intensity of the 110 plane falls within the range of 0.5 to 1.5.

Note that the peak corresponding to the 110 plane appears around 2θ=14°, and the peak corresponding to the 040 plane appears around 2θ=17°. The measurement conditions for wide-angle X-ray diffraction are Soller/PCS (aperture angle of the incident parallel slit): 5.0 deg, IS length (length of the longitudinal restriction slit): 10.0 mm, and PSA open (the aperture angle of the light-receiving PSA is open). ), Soller (aperture angle of light-receiving parallel slit): 5.0 deg, 2θ/θ: 2 to 40 deg, and step is 0.04 deg.

Further, it can be confirmed by analyzing the polypropylene layer 11 by Raman spectroscopy that the polypropylene layer 11 is made of unstretched polypropylene and not drawn polypropylene. Specifically, when a polypropylene layer is analyzed by Raman spectroscopy, the height of the crystalline peak intensity "A" that appears at about 809 cm ^-1 and the high amorphous peak intensity that appears at about 842 cm ^-1 When the ratio of "B" (A/B) is 1.6 or less, it can be confirmed that the polypropylene layer 11 is made of unstretched polypropylene. The measurement conditions were a laser wavelength of 633 nm, a grating of 600 gr/mm, a confocal hole of 100 μm, a microscope lens of 10 times, an exposure time of 15 seconds, and one integration. The Raman spectrum was measured so that the MD and the incident laser polarization plane were parallel. In addition, the straight line connecting 710 cm ^-1 and 925 cm ^-1 was taken as the baseline. As for the analysis conditions, the peak heights at 809 cm ^-1 and 842 cm ^-1 after baseline correction were calculated as peak intensities. Note that the above-mentioned height "A" of the crystalline peak intensity appearing at about 809 cm ^-1 is a peak attributed to a combination mode of main chain CC stretching and CH3 bending vibration. Further, the height "B" of the amorphous peak intensity appearing at about 842 cm ^-1 is a peak attributed to the CH3 bending vibration mode.

In the present invention, the method for confirming the MD of the polypropylene layer 11 is as follows. For a cross section in the length direction of the polypropylene layer 11 and each cross section (10 cross sections in total) in a direction perpendicular to the cross section in the length direction by changing the angle by 10 degrees from a direction parallel to the cross section in the length direction. , respectively, to confirm the sea-island structure by observing them with electron micrographs. Next, in each cross section, the shape of each individual island is observed. Regarding the shape of each island, the straight line distance connecting the leftmost end in the direction perpendicular to the thickness direction of the polypropylene layer 11 and the rightmost end in the perpendicular direction is defined as the diameter y. In each cross section, the average of the top 20 diameters y of the island shape is calculated in descending order of diameter y. The direction parallel to the cross section where the average diameter y of the island shape is the largest is determined to be the MD.

The polypropylene contained in the polypropylene layer 11 is preferably a crystalline or Examples include amorphous polypropylene. Examples of the composition in which the polypropylene layer 11 has the sea-island structure described above include a composition in which the polypropylene layer 11 contains a polypropylene block copolymer, a composition in which the polypropylene block copolymer and a polypropylene random copolymer are contained, a composition in which the polypropylene layer 11 contains a polypropylene block copolymer and a polypropylene random copolymer, and a composition in which the polypropylene layer 11 contains a polypropylene block copolymer and a polypropylene random copolymer, homopolypropylene and random polypropylene. Examples include compositions containing polyethylene components. Among these, it is more preferable that the polypropylene layer 11 contains block polypropylene, and it is even more preferable that the polypropylene layer 11 is constituted by block polypropylene. The proportion of propylene contained in the block polypropylene is preferably about 10 to 90% by mass, more preferably about 30 to 80% by mass.

In the adhesive film 1 for metal terminals of the present invention, the polypropylene layer 11 may be only one layer, or may be two or more layers. Further, one polypropylene layer 11 may have a plurality of layers made of the same or different polypropylene stacked in succession, and the plurality of layers may constitute one polypropylene layer 11. Preferably, the polypropylene layer 11 includes a layer made of block polypropylene.

A preferred embodiment of the single polypropylene layer 11 is a laminate of a layer made of random polypropylene and a layer made of block polypropylene, particularly a layer made of random polypropylene and a layer made of block polypropylene. It is preferable to have a laminated structure (three-layer structure) in which a layer made of polypropylene and a layer made of random polypropylene are laminated in this order.

In the present invention, when a plurality of layers made of polypropylene are successively laminated, these layers are collectively referred to as one polypropylene layer 11. Similarly, when a plurality of layers made of acid-modified polypropylene are successively laminated, these layers are collectively referred to as one acid-modified polypropylene layer 12.

The thickness of one polypropylene layer 11 is not particularly limited as long as the total thickness of the polypropylene layers 11 is within the range of 0.7 to 3.5, where the total thickness of the acid-modified polypropylene layers 12 is 1. However, from the viewpoint of further improving the electrolyte resistance while further increasing the adhesion with the packaging material and the metal terminal, the thickness is preferably about 15 to 80 μm, more preferably about 20 to 70 μm. Although the details of the mechanism are not clear, if the thickness of the acid-modified polypropylene layer is too large, cohesive failure of the acid-modified polypropylene layer tends to occur, and the adhesion of the adhesive film for metal terminals tends to decrease. It is in.

From the viewpoint of further improving the electrolyte resistance while further increasing the adhesion with the packaging material and the metal terminal, in the adhesive film 1 for metal terminals, the polypropylene layer 11 has a thickness that is smaller than the thickness of the adhesive film 1 for metal terminals. It is preferable that the polypropylene layer 11 accounts for about 40% or more, more preferably about 45% or more, and as an upper limit, it is preferable that the polypropylene layer 11 accounts for about 85% or less of the thickness of the adhesive film 1 for metal terminals. It is more preferable that it accounts for 80% or less. The preferable range of the thickness of the polypropylene layer 11 in the thickness of the adhesive film 1 for metal terminals includes about 40 to 85% and about 45 to 80%.

The melting peak temperature of the polypropylene layer 11 is not particularly limited, but is preferably about 140 to 165°C, from the viewpoint of further improving the electrolyte resistance while further increasing the adhesion with the packaging material and the metal terminal. More preferably, the temperature is about 150 to 160°C. In the present invention, the melting peak temperature of the polypropylene layer 11 is a value measured using a differential scanning calorimeter (DSC), with a heating rate of 10°C/min and a temperature measurement range of -50 to 200°C. , measured using an aluminum pan as the sample pan.

(Acid-modified polypropylene layer 12)
In the present invention, the acid-modified polypropylene layer 12 is a layer made of acid-modified polypropylene. It is preferable that a sea-island structure is also observed in the acid-modified polypropylene layer 12 when its cross section is observed using an electron micrograph. The method for confirming the sea-island structure in the acid-modified polypropylene layer 12 is the same as the method for confirming the above-described polypropylene layer 11.

In the sea-island structure of the acid-modified polypropylene layer 12, the area ratio of the island portion is not particularly limited, but from the viewpoint of further improving the electrolyte resistance while further increasing the adhesion with the packaging material and the metal terminal. is preferably about 10 to 50%, more preferably about 20 to 40%. The method for measuring the area ratio of the island portion in the sea-island structure of the acid-modified polypropylene layer 12 is the same as the method for measuring the polypropylene layer 11 described above, except that the acid-modified polypropylene layer 12 is used as the measurement target. Note that if the area ratio of the island portion is 2% or less, it is evaluated that the island substantially does not have a sea-island structure.

The acid-modified polypropylene is not particularly limited as long as it is acid-modified polypropylene, but polypropylene graft-modified with an unsaturated carboxylic acid or its anhydride is preferably used. Examples of the unsaturated carboxylic acid or anhydride thereof used for acid modification include maleic acid, acrylic acid, itaconic acid, crotonic acid, maleic anhydride, and itaconic anhydride.

The acid-modified polypropylene is preferably a crystalline or amorphous polypropylene such as homopolypropylene, a block copolymer of polypropylene (for example, a block copolymer of propylene and ethylene), or a random copolymer of polypropylene (for example, a random copolymer of propylene and ethylene). Examples include polypropylene. Among these, it is preferable to include a block copolymer of polypropylene (block polypropylene) or a random copolymer of polypropylene (random polypropylene). Note that the fact that the acid-modified polypropylene layer 12 is a layer made of acid-modified polypropylene can be analyzed by infrared spectroscopy, gas chromatography-mass spectrometry, or the like, and the analysis method is not particularly limited. For example, when maleic anhydride-modified polypropylene is measured by infrared spectroscopy, peaks derived from maleic anhydride are detected at wave numbers around 1760 cm ^-1 and around 1780 cm ^-1 wave numbers. However, if the degree of acid modification is low, the peak may become small and may not be detected. In that case, it can be analyzed by nuclear magnetic resonance spectroscopy.

In the adhesive film 1 for metal terminals of the present invention, the acid-modified polypropylene layer 12 may have only one layer, or may have two or more layers. Furthermore, one acid-modified polypropylene layer 12 has a plurality of consecutively laminated layers made of the same or different acid-modified polypropylene, and the plurality of layers constitute one acid-modified polypropylene layer 12. You can.

A preferred embodiment of the single acid-modified polypropylene layer 12 includes a layer composed of maleic anhydride-modified polypropylene.

The thickness of one acid-modified polypropylene layer 12 is particularly if the total thickness of the polypropylene layers 11 is within the range of 0.7 to 3.5 when the total thickness of the acid-modified polypropylene layers 12 is 1. Although not limited, from the viewpoint of further improving the electrolyte resistance while further increasing the adhesion with the packaging material and the metal terminal, the thickness is preferably about 10 μm or more, more preferably about 15 μm or more, and the upper limit is: Preferably it is about 40 μm or less, more preferably about 35 μm or less, and still more preferably about 30 μm or less.

The melting peak temperature of the acid-modified polypropylene layer 12 is not particularly limited, but is preferably 130 to 165°C from the viewpoint of further improving the electrolyte resistance while further increasing the adhesion to the packaging material and the metal terminal. temperature, more preferably about 140 to 160°C. In the present invention, the melting peak temperature of the acid-modified polypropylene layer 12 is a value measured in the same manner as the method for measuring the melting peak temperature of the polypropylene layer 11.

From the viewpoint of improving the sealing strength while suppressing the crushing of the adhesive film for metal terminals during heat sealing, in the adhesive film 1 for metal terminals of the present invention, the softening point of the polypropylene layer 11 and the softening point of the acid-modified polypropylene layer 12 are adjusted. As for the absolute value of the difference in softening points, the upper limit is preferably about 40°C or less, more preferably about 30°C or less, and still more preferably about 20°C or less, and the lower limit is preferably about 0°C or more, more preferably about 20°C or less. The temperature is preferably about 5°C or higher, more preferably about 10°C or higher. The softening points of the polypropylene layer 11 and the acid-modified polypropylene layer 12 are values measured as follows.

(Method of measuring softening point)
The values were measured using a scanning thermal microscope (NanoTA manufactured by Anasys), the cantilever model of the thermal probe was EX-AN2-200, and the heating rate was 5° C./s. Moreover, the softening point was taken as the peak top temperature.

The adhesive film 1 for metal terminals of the present invention may contain various additives such as a lubricant, an antioxidant, an ultraviolet absorber, and a light stabilizer, if necessary. Note that depending on the type, content, etc. of the additive, the adhesive film 1 for metal terminals may change color.

The content of the lubricant contained in the entire adhesive film 1 for metal terminals is preferably about 0 to 2000 ppm.

(Measurement of lubricant amount)
The content of the lubricant contained in the entire adhesive film 1 for metal terminals is a value measured using a gas chromatograph mass spectrometer (GC-MS). Specifically, the additives in the adhesive film for metal terminals are extracted into methanol that is boiled and refluxed, and the resulting methanol extract is analyzed by GC-MS. Measure the amount of lubricant contained in the entire adhesive film.

The lubricant is not particularly limited, but preferably includes an amide lubricant. Specific examples of amide lubricants include saturated fatty acid amides, unsaturated fatty acid amides, substituted amides, methylolamides, saturated fatty acid bisamides, unsaturated fatty acid bisamides, and the like. Specific examples of saturated fatty acid amides include lauric acid amide, palmitic acid amide, stearic acid amide, behenic acid amide, hydroxystearic acid amide, and the like. Specific examples of unsaturated fatty acid amides include oleic acid amide and erucic acid amide. Specific examples of substituted amides include N-oleyl palmitic acid amide, N-stearyl stearic acid amide, N-stearyl oleic acid amide, N-oleyl stearic acid amide, N-stearyl erucic acid amide, and the like. Furthermore, specific examples of methylolamide include methylolstearamide and the like. Specific examples of saturated fatty acid bisamides include methylene bisstearamide, ethylene biscapric acid amide, ethylene bislauric acid amide, ethylene bisstearic acid amide, ethylene bishydroxystearic acid amide, ethylene bisbehenic acid amide, and hexamethylene bis stearic acid amide. Examples include acid amide, hexamethylene bisbehenic acid amide, hexamethylene hydroxystearic acid amide, N,N'-distearyl adipic acid amide, N,N'-distearyl sebacic acid amide, and the like. Specific examples of unsaturated fatty acid bisamides include ethylene bisoleic acid amide, ethylene biserucic acid amide, hexamethylene bisoleic acid amide, N,N'-dioleyladipic acid amide, and N,N'-dioleyl sebacic acid amide. Examples include. Specific examples of fatty acid ester amides include stearamide ethyl stearate. Specific examples of aromatic bisamides include m-xylylene bisstearamide, m-xylylene bishydroxystearamide, and N,N'-distearylisophthalic acid amide. One type of lubricant may be used alone, or two or more types may be used in combination.

Moreover, the adhesive film 1 for metal terminals of the present invention may contain a filler as necessary. When the adhesive film 1 for metal terminals contains a filler, the filler functions as a spacer, so that short circuits between the metal terminals 2 and the barrier layer 33 of the packaging material 3 can be more effectively prevented. It becomes possible to suppress this. The particle size of the filler is in the range of about 0.1 to 35 μm, preferably about 5.0 to 30 μm, and more preferably about 10 to 25 μm. In addition, when a filler is added to the adhesive film 1 for metal terminals, it is preferably included in the polypropylene layer 11 and/or the acid-modified polypropylene layer 12, and the content of the filler is determined from the polypropylene layer 11 and the acid-modified polypropylene layer 12. For 100 parts by mass of the resin component forming the layer 12, about 5 to 30 parts by mass, more preferably about 10 to 20 parts by mass, respectively.

As the filler, both inorganic and organic fillers can be used. Examples of inorganic fillers include carbon (carbon, graphite), silica, aluminum oxide, barium titanate, iron oxide, silicon carbide, zirconium oxide, zirconium silicate, magnesium oxide, titanium oxide, calcium aluminate, calcium hydroxide. , aluminum hydroxide, magnesium hydroxide, calcium carbonate, and the like. Examples of organic fillers include fluororesin, phenol resin, urea resin, epoxy resin, acrylic resin, benzoguanamine/formaldehyde condensate, melamine/formaldehyde condensate, polymethyl methacrylate crosslinked product, polyethylene crosslinked product, etc. Can be mentioned. From the viewpoint of shape stability, rigidity, and content resistance, aluminum oxide, silica, fluororesin, acrylic resin, and benzoguanamine formaldehyde condensate are preferred, and among these, spherical aluminum oxide and silica are particularly preferred. As a method of mixing the filler into the resin component forming the polypropylene layer 11 and/or the acid-modified polypropylene layer 12, the two are melt-blended in advance using a Banbury mixer, etc., and the master batch is made into a predetermined mixing ratio. , a direct mixing method with a resin component, etc. can be adopted.

Moreover, the adhesive film 1 for metal terminals may each contain a pigment as necessary. As the pigment, various inorganic pigments can be used. As a specific example of the pigment, carbon (carbon, graphite) exemplified in the above-mentioned filler can be preferably exemplified. Carbon (carbon, graphite) is a material generally used inside batteries, and there is no risk of elution into the electrolyte. In addition, a sufficient coloring effect can be obtained with a large coloring effect that does not impede adhesiveness, and the resin does not melt due to heat, making it possible to increase the apparent melt viscosity of the added resin. Furthermore, it is possible to prevent the pressurized portion from becoming thin during thermal bonding (sealing), thereby preventing a decrease in sealing strength.

When a pigment is added to the adhesive film 1 for metal terminals, it is preferably included in the polypropylene layer 11 and/or the acid-modified polypropylene layer 12, and the amount added is, for example, carbon black with a particle size of about 0.03 μm. When using, about 0.05 to 0.3 parts by mass, preferably 0.1 to 0.2 parts by mass, respectively, per 100 parts by mass of the resin component forming the polypropylene layer 11 and the acid-modified polypropylene layer 12. The degree is mentioned. By adding a pigment to the adhesive film 1 for metal terminals, the presence or absence of the adhesive film 1 for metal terminals can be detected with a sensor or visually inspected. In addition, when adding a filler and a pigment to the polypropylene layer 11 and/or the acid-modified polypropylene layer 12, the filler and the pigment may be added to the same polypropylene layer 11 and/or the acid-modified polypropylene layer 12, From the viewpoint of not inhibiting the thermal fusion properties of the adhesive film 1 for metal terminals, it is preferable to add the filler and pigment separately to the polypropylene layer 11 and the acid-modified polypropylene layer 12.

The adhesive film 1 for metal terminals of the present invention can be manufactured by laminating at least one polypropylene layer and at least one acid-modified polypropylene layer. The method of laminating at least one polypropylene layer and at least one acid-modified polypropylene layer is not particularly limited, and can be carried out using, for example, a thermal lamination method, a sandwich lamination method, an extrusion lamination method, or the like.

The method for interposing the adhesive film 1 for metal terminals between the metal terminals 2 and the packaging material 3 is not particularly limited, and for example, as shown in FIGS. The adhesive film 1 for metal terminals may be wrapped around the metal terminals 2 in the areas where the metal terminals 2 are covered. Although not shown, the adhesive film 1 for metal terminals is arranged on both sides of the metal terminals 2 so as to cross the two metal terminals 2 in the portion where the metal terminals 2 are sandwiched between the packaging materials 3. You may.

[Metal terminal 2]
The adhesive film 1 for metal terminals of the present invention is used by being interposed between the metal terminal 2 and the packaging material 3. The metal terminal 2 (tab) is a member electrically connected to the electrode (positive electrode or negative electrode) of the battery element 4, and is made of a metal material. The metal material constituting the metal terminal 2 is not particularly limited, and examples thereof include aluminum, nickel, copper, and the like. For example, the metal terminal 2 connected to the positive electrode of a lithium ion battery is usually made of aluminum or the like. Further, the metal terminal connected to the negative electrode of a lithium ion battery is usually made of copper, nickel, or the like.

The surface of the metal terminal 2 is preferably subjected to a chemical conversion treatment from the viewpoint of improving electrolyte resistance. For example, when the metal terminal 2 is made of aluminum, specific examples of chemical conversion treatment include known methods of forming an acid-resistant film using phosphate, chromate, fluoride, triazine thiol compound, etc. . Among the methods for forming an acid-resistant film, phosphoric acid chromate treatment using a method composed of three components: a phenol resin, a chromium (III) fluoride compound, and phosphoric acid is suitable.

The size of the metal terminal 2 may be appropriately set depending on the size of the battery used. The thickness of the metal terminal 2 is preferably about 50 to 1000 μm, more preferably about 70 to 800 μm. Further, the length of the metal terminal 2 is preferably about 1 to 200 mm, more preferably about 3 to 150 mm. Further, the width of the metal terminal 2 is preferably about 1 to 200 mm, more preferably about 3 to 150 mm.

[Packaging material 3]
Examples of the packaging material 3 include those having a laminate structure consisting of a laminate including at least a base material layer 31, a barrier layer 33, and a heat-fusible resin layer 34 in this order. FIG. 6 shows an example of the cross-sectional structure of the packaging material 3 in which a base layer 31, an adhesive layer 32, a barrier layer 33, an adhesive layer 35, and a heat-fusible resin layer 34 are laminated in this order. . The adhesive layer 32 is a layer provided as necessary for the purpose of increasing the adhesion between the base material layer 31 and the barrier layer 33. Further, the adhesive layer 35 is a layer provided as necessary for the purpose of increasing the adhesion between the barrier layer 33 and the heat-fusible resin layer 34 .

In the packaging material 3, the base material layer 31 is the outermost layer, and the heat-fusible resin layer 34 is the innermost layer. When assembling the battery, the battery element 4 is sealed by bringing the heat-fusible resin layers 34 located at the periphery of the battery element 4 into contact with each other and thermally welding them. Note that although FIGS. 1 to 3 illustrate the battery 10 using an embossed type packaging material 3 formed by embossing molding or the like, the packaging material 3 may be of an unmolded pouch type. good. Note that pouch types include three-sided seals, four-sided seals, pillow types, etc., but any type may be used.

[Base material layer 31]
In the packaging material 3, the base material layer 31 is a layer that functions as a base material of the packaging material, and is a layer that forms the outermost layer.

The material forming the base layer 31 is not particularly limited as long as it has insulation properties. Examples of the material forming the base layer 31 include polyester, polyamide, polyolefin, epoxy resin, acrylic resin, fluororesin, polyurethane, silicone resin, phenol resin, polyetherimide, polyimide, and mixtures and copolymers thereof. etc.

The thickness of the base material layer 31 is, for example, about 10 to 50 μm, preferably about 15 to 30 μm.

[Adhesive layer 32]
In the packaging material 3, the adhesive layer 32 is a layer disposed on the base layer 31 as necessary in order to impart adhesiveness to the base layer 31. That is, the adhesive layer 32 is provided between the base material layer 31 and the barrier layer 33 as necessary.

The adhesive layer 32 is formed of an adhesive that can bond the base material layer 31 and the barrier layer 33 together. The adhesive used to form the adhesive layer 32 may be a two-component curing adhesive or a one-component curing adhesive. Further, the adhesive used for forming the adhesive layer 32 is not particularly limited, and may be any one of a chemical reaction type, a solvent volatilization type, a heat melt type, a heat pressure type, and the like.

The thickness of the adhesive layer 32 is, for example, about 2 to 50 μm, preferably about 3 to 25 μm.

[Barrier layer 33]
In the packaging material, the barrier layer 33 is a layer that not only improves the strength of the battery packaging material but also has the function of preventing water vapor, oxygen, light, etc. from entering the inside of the battery. Specific examples of the metal constituting the barrier layer 33 include aluminum, stainless steel, and titanium, with aluminum being preferred. The barrier layer 33 can be formed of, for example, a metal foil, a metal vapor deposited film, an inorganic oxide vapor deposited film, a carbon-containing inorganic oxide vapor deposited film, a film provided with these vapor deposited films, etc., and may be formed of a metal foil. is preferable, and it is more preferable to use aluminum alloy foil. From the viewpoint of preventing wrinkles and pinholes from occurring in the barrier layer 33 during the production of battery packaging materials, the barrier layer is made of, for example, annealed aluminum (JIS H4160:1994 A8021H-O, JIS H4160: It is more preferable to use a soft aluminum alloy foil such as 1994 A8079H-O, JIS H4000:2014 A8021P-O, JIS H4000:2014 A8079P-O).

The thickness of the barrier layer 33 is not particularly limited as long as it functions as a barrier layer against water vapor, etc., but may be, for example, about 10 to 50 μm, preferably about 10 to 40 μm.

[Adhesive layer 35]
In the packaging material 3, the adhesive layer 35 is a layer provided as necessary between the barrier layer 33 and the heat-fusible resin layer 34 in order to firmly adhere the heat-fusible resin layer 34.

The adhesive layer 35 is formed of an adhesive that can bond the barrier layer 33 and the heat-fusible resin layer 34 together. The composition of the adhesive used to form the adhesive layer is not particularly limited, but examples include resin compositions containing acid-modified polyolefins. Examples of the acid-modified polyolefin include the same ones as those described for the acid-modified polypropylene layer 12. In addition, polyethylene such as low density polyethylene, medium density polyethylene, high density polyethylene, linear low density polyethylene, etc. is acid-modified with an unsaturated carboxylic acid or its anhydride (for example, as exemplified in the acid-modified polypropylene layer 12). Examples can also be given.

The thickness of the adhesive layer 35 is, for example, about 1 to 40 μm, preferably about 2 to 30 μm.

[Thermofusible resin layer 34]
In the packaging material 3, the heat-fusible resin layer 34 corresponds to the innermost layer, and is a layer that seals the battery element by thermally welding the heat-fusible resin layers to each other during battery assembly.

The resin component used for the heat-fusible resin layer 34 is not particularly limited as long as it can be heat-welded, and examples thereof include polyolefin and acid-modified polyolefin.

Examples of the polyolefin include the same ones as those exemplified for the polypropylene layer 11, and polyethylenes such as low density polyethylene, medium density polyethylene, high density polyethylene, and linear low density polyethylene. Further, as the acid-modified polyolefin, the same ones as those described for the adhesive layer 35 can be mentioned.

Further, the thickness of the heat-fusible resin layer 34 is not particularly limited, but is preferably about 2 to 2000 μm, more preferably about 5 to 1000 μm, and even more preferably about 10 to 500 μm.

2. battery 10
The battery 10 of the present invention includes at least a battery element 4 including a positive electrode, a negative electrode, and an electrolyte, a packaging material 3 that seals the battery element 4, and a packaging material 3 that is electrically connected to each of the positive and negative electrodes. 3 and a metal terminal 2 protruding outward. The battery 10 of the present invention is characterized in that the adhesive film 1 for metal terminals of the present invention is interposed between the metal terminal 2 and the packaging material 3.

Specifically, a battery element 4 including at least a positive electrode, a negative electrode, and an electrolyte is wrapped in a packaging material 3 with metal terminals 2 connected to each of the positive and negative electrodes protruding outward, and the metal of the present invention is The terminal adhesive film 1 is interposed between the metal terminal 2 and the heat-fusible resin layer 34, and the flange portion of the packaging material (in the area where the heat-fusible resin layers 34 contact each other) is attached to the periphery of the battery element 4. The battery 10 using the packaging material 3 is provided by covering the packaging material so that the peripheral edge 3a) can be formed and heat-sealing the heat-sealing resin layers 34 of the flange parts to each other. Ru. Note that when the packaging material 3 is used to house the battery element 4, the packaging material 3 is used so that the heat-fusible resin layer 34 is on the inside (the surface in contact with the battery element 4).

The battery of the present invention may be either a primary battery or a secondary battery, but is preferably a secondary battery. There are no particular restrictions on the type of secondary battery; examples include lithium-ion batteries, lithium-ion polymer batteries, lead-acid batteries, nickel-metal hydride batteries, nickel-cadmium batteries, nickel-iron batteries, and nickel-zinc batteries. Examples include batteries, silver oxide/zinc oxide batteries, metal-air batteries, polyvalent cation batteries, capacitors, and capacitors. Among these secondary batteries, lithium ion batteries and lithium ion polymer batteries are preferred.

In addition, when measuring the thickness of the packaging material, metal terminal, and adhesive film for metal terminals that make up the battery, at the part where the packaging material, adhesive film for metal terminals, and metal terminal are laminated, the packaging The preferred thickness of the material is about 10 to 65 μm, the thickness of the metal terminal is about 50 to 1000 μm, and the preferable thickness of the adhesive film for metal terminals is about 30 to 80 μm. The preferred total thickness of the packaging material and the adhesive film for metal terminals is about 40 to 145 μm.

The present invention will be explained in detail by showing Examples and Comparative Examples below. However, the present invention is not limited to the examples.

In Examples and Comparative Examples, evaluation of measurement of melting peak temperature, measurement of thermal shrinkage rate, measurement of seal strength, measurement of thickness residual ratio, measurement of electrolyte resistance and measurement of area ratio of island parts in sea-island structure was done as follows. The results are shown in Table 1.

(Measurement of melting peak temperature)
The adhesive film for metal terminals was measured using a differential scanning calorimeter (DSC). As the device, "DSC-60 Plus" manufactured by Shimadzu Corporation was used. The measurement conditions were a temperature increase rate of 10°C/min, a temperature measurement range of -50 to 200°C, and an aluminum pan was used as the sample pan.

(Measurement of heat shrinkage rate)
The adhesive film for metal terminals was cut into a size of 50 mm length (MD) x width 4 mm (TD) to prepare a test piece. Next, the length M (mm) of the test piece was measured using a metal ruler. Next, the lengthwise end of the test piece was fixed to a wire mesh with tape, and the test piece was suspended from the wire mesh. In this state, the test piece was placed in an oven heated to 190° C. for 120 seconds, and then the test piece was taken out together with the wire gauze and allowed to cool naturally at room temperature (25° C.). Next, the length N (mm) of the test piece that had been naturally cooled to room temperature was measured using a metal ruler. The heat shrinkage rate of the adhesive film for metal terminals was calculated using the following formula.
Heat shrinkage rate (%) = (length N/length M) x 100

(Measurement of seal strength)
As shown in the schematic diagram of FIG. 7, the packaging material 3 was cut into a size of 150 mm length (MD) x width 60 mm (TD). Further, the adhesive film 1 for metal terminals was cut into a size of 75 mm length (MD) x width 60 mm (TD). In addition, a metal terminal 2 (aluminum plate, length 60 mm, width 25 mm, thickness 0.1 mm) was prepared. Next, as shown in the schematic diagram of FIG. 8, the packaging material 3 was folded in half in the length direction at the center P of the MD, with the heat-fusible resin layer facing inside. Next, the adhesive film 1 for metal terminals and the metal terminal 2 (aluminum plate, length 60 mm, width 25 mm, thickness 0.1 mm) were stacked, and the package was folded in two as shown in the schematic diagram of FIG. Insert between material 3. At this time, the acid-modified polypropylene layer of the metal terminal adhesive film 1 was placed in contact with the metal terminal 2. A cross-sectional view from the side is shown in Figure 8b. In this state, as shown in the schematic diagram of FIG. 9a, heat sealing is performed from both sides of the packaging material 3 under the conditions of a sealing width of 7.0 mm, a sealing temperature of 190° C., a surface pressure of 1.0 MPa, and a sealing time of 3 seconds. A laminate was obtained. In the heat-sealed portion S of FIG. 9, the direction of the seal width corresponds to the MD of the packaging material. Next, a sample was cut out from the laminate at the position indicated by the two-dot chain line in the schematic diagram of FIG. 9b so that the width of the heat-sealed portion S (TD of the packaging material) was 15 mm. The obtained sample packaging material 3 and the metal terminal adhesive film 1 were separated in the 180° direction to the position of the heat-sealed portion S. A cross-sectional view of the sample in this state viewed from the side is shown in FIG. 9c. Next, the seal strength (N/15 mm) was measured using a tensile tester (AG-Xplus manufactured by Shimadzu Corporation) at a speed of 300 mm/min, a distance between chucks of 50 mm, and a T-peel method. . At this time, as shown in FIG. 2/Packaging material 3'' is sandwiched between the lower chucks, and with the packaging material 3 spaced apart in the 180° direction being sandwiched between the upper chucks, the packaging material 3 and the metal terminal adhesive film 1 are peeled off. The seal strength was measured.

(Evaluation of electrolyte resistance)
The adhesive film for metal terminals was cut into a size of 15 mm (MD) x 100 mm (TD) to prepare a test piece. Next, the test piece was immersed in an electrolytic solution (1M LiPF ₆ solution (ethylene carbonate: dimethyl carbonate: diethyl carbonate = 1:1:1, volume ratio) and stored in an oven at 85 ° C. for 24 hours. After taking out the test piece and washing it with water, the test piece was visually observed.A case where there was no separation between the layers of the test piece was rated "A", and a case where there was separation between the layers of the test piece was rated "C". ”.

(Measurement of remaining thickness of adhesive film for metal terminals)
An aluminum plate (pure aluminum, JIS H4160-1994 A1N30H-O) with a length of 60 mm, a width of 25 mm, and a thickness of 100 μm and the adhesive film for metal terminals with a length of 70 mm and a width of 5 mm were prepared. Next, the thickness A (μm) of the adhesive film for metal terminals was measured using a microgauge. Next, the adhesive film for metal terminals was stacked on the central part of the aluminum plate so that the length direction and the width direction of the aluminum plate and the adhesive film for metal terminals were aligned. Next, prepare two metal plates that are longer than the length of the aluminum plate and have a width of 7 mm. Next, cover the entire surface of the adhesive film for metal terminals, and then Heating and pressurization were performed under the conditions of 190° C., surface pressure of 1.27 MPa, and time of 3 seconds to obtain a laminate of an aluminum plate and an adhesive film for metal terminals. Next, the thickness B (μm) of the heated and pressurized portion of the laminate was measured using a microgauge. The remaining thickness of the adhesive film for metal terminals was calculated using the following formula. At this time, the thickness B is measured from one central part of the laminate and both longitudinal ends of the laminate (both ends of the part where the aluminum plate and the adhesive film for metal terminals are laminated) to the center. It was taken as the average value of a total of 3 locations, 2 locations of 10 mm toward the end.
Thickness residual rate (%) of adhesive film for metal terminals = (Thickness B-100) / Thickness A x 100

<Method for measuring the area ratio of island parts in sea-island structure>
An adhesive film for metal terminals was embedded in a thermosetting epoxy resin and cured. A cross section in the desired direction (cross section along TD) was prepared using a commercially available rotary microtome (UC6 manufactured by LEICA) and a diamond knife. Cross sections were prepared at ℃. The entire embedding resin was stained with ruthenium tetroxide overnight. When dyed, the polypropylene swells, so the swollen part was trimmed with a microtome, and the section, which was about 100 nm thick and further cut by about 1 to 2 μm, was observed as follows. Observe the stained cross section with a field emission scanning electron microscope (for example, Hitachi High-Technologies S-4800 TYPE1, measurement conditions: 3 kV 20 mA High WD 6 mm detector (Upper)) and create an image (magnification: 10,000 times). Obtained. Next, using image processing software that can binarize images (for example, image analysis software WinROOF (Ver. 7.4) manufactured by Mitani Shoji Co., Ltd.), the island part and the sea part of the sea-island structure are binarized for the image. , the ratio of the area occupied by the island part (total area of the island part/area of the measurement range of the image) was calculated.The specific image processing conditions are as follows.In this measurement, the island part The island area was observed to be brighter than the ocean area because the area was stained more than the ocean area.
[Image processing conditions]
3x3pix averaging binarization: Automatic binarization Isolated point removal: Removes an object or background consisting of one pixel.
Deletion: Deleting particles by determining the shape feature value or density feature value (recognizes an area of 0.005 μm ² as noise)

<Manufacture of adhesive film for metal terminals>
(Example 1)
As a polypropylene layer, a three-layer unstretched polypropylene film (CPP, total thickness 50 μm, melting peak temperature 155 ℃) was prepared. Next, maleic anhydride-modified polypropylene was laminated on both sides of the unstretched polypropylene film by extrusion lamination, so that acid-modified polypropylene layer (25 μm)/polypropylene layer (50 μm)/acid-modified polypropylene layer (25 μm) were formed in this order. A laminated adhesive film for metal terminals was manufactured. When the heat shrinkage rate of the obtained adhesive film for metal terminals was measured, it showed a high value of 83.0%.

(Example 2)
As a polypropylene layer, a three-layer unstretched polypropylene film (CPP, total thickness 60 μm, melting peak temperature 155 ℃) was prepared. Next, maleic anhydride-modified polypropylene was laminated on both sides of the unstretched polypropylene film by extrusion lamination to form an acid-modified polypropylene layer (20 μm)/polypropylene layer (60 μm)/acid-modified polypropylene layer (20 μm) in this order. A laminated adhesive film for metal terminals was manufactured. When the heat shrinkage rate of the obtained adhesive film for metal terminals was measured, it showed a high value of 81.3%.

(Example 3)
As a polypropylene layer, a three-layer unstretched polypropylene film (CPP, total thickness 50 μm, melting peak temperature 155 ℃) was prepared. Next, maleic anhydride-modified polypropylene is laminated on one side of the unstretched polypropylene film by extrusion lamination to produce an adhesive film for metal terminals in which an acid-modified polypropylene layer (16 μm)/a polypropylene layer (50 μm) are laminated. did. When the heat shrinkage rate of the obtained adhesive film for metal terminals was measured, it showed a high value of 80.1%.

(Example 4)
As a polypropylene layer, a three-layer unstretched polypropylene film (CPP, total thickness 30 μm, melting peak temperature 155 ℃) was prepared. Next, maleic anhydride-modified polypropylene is laminated on one side of the unstretched polypropylene film by extrusion lamination to produce an adhesive film for metal terminals in which an acid-modified polypropylene layer (36 μm)/a polypropylene layer (30 μm) are laminated. did. When the heat shrinkage rate of the obtained adhesive film for metal terminals was measured, it showed a high value of 88.1%.

(Example 5)
As a polypropylene layer, a three-layer unstretched polypropylene film (CPP, total thickness 30 μm, melting peak temperature 155 ℃) was prepared. Next, maleic anhydride-modified polypropylene was laminated on both sides of the unstretched polypropylene film by an extrusion lamination method to form an acid-modified polypropylene layer (18 μm)/polypropylene layer (30 μm)/acid-modified polypropylene layer (18 μm) in this order. A laminated adhesive film for metal terminals was manufactured. When the heat shrinkage rate of the obtained adhesive film for metal terminals was measured, it showed a high value of 88.1%.

(Example 6)
As the polypropylene layer, a block polypropylene layer (60 μm) of an unstretched polypropylene film (CPP, total thickness 60 μm, melting peak temperature 159° C.) was prepared. Next, maleic anhydride-modified polypropylene was laminated on both sides of the unstretched polypropylene film by extrusion lamination to form an acid-modified polypropylene layer (20 μm)/polypropylene layer (60 μm)/acid-modified polypropylene layer (20 μm) in this order. A laminated adhesive film for metal terminals was manufactured. When the heat shrinkage rate of the obtained adhesive film for metal terminals was measured, it showed a high value of 81.7%.

(Example 7)
As a polypropylene layer, a three-layer unstretched polypropylene film (CPP, total thickness 30 μm, melting peak temperature 155 ℃) was prepared. Next, maleic anhydride-modified polypropylene was laminated on both sides of the unstretched polypropylene film by an extrusion lamination method to form a metal laminated layer of acid-modified polypropylene layer (16 μm)/polypropylene layer (30 μm)/acid-modified polypropylene (16 μm). An adhesive film for terminals was manufactured. When the heat shrinkage rate of the obtained adhesive film for metal terminals was measured, it showed a high value of 88.7%.

(Comparative example 1)
As a polypropylene layer, a three-layer unstretched polypropylene film (CPP, total thickness 30 μm, melting peak temperature 155 ℃) was prepared. Next, maleic anhydride-modified polypropylene was laminated on both sides of the unstretched polypropylene film by extrusion lamination, so that acid-modified polypropylene layer (35 μm)/polypropylene layer (30 μm)/acid-modified polypropylene layer (35 μm) were formed in this order. A laminated adhesive film for metal terminals was manufactured.

(Comparative example 2)
As a polypropylene layer, a three-layer unstretched polypropylene film (CPP, total thickness 25 μm, melting peak temperature 155 ℃) was prepared. Next, maleic anhydride-modified polypropylene is laminated on one side of the unstretched polypropylene film by extrusion lamination to produce an adhesive film for metal terminals in which an acid-modified polypropylene layer (41 μm)/a polypropylene layer (25 μm) are laminated. did.

(Comparative example 3)
A stretched polypropylene film (OPP, homopolypropylene, thickness 50 μm, melting peak temperature 165° C.) was prepared as the polypropylene layer. Next, maleic anhydride-modified polypropylene was laminated on both sides of the stretched polypropylene film by extrusion lamination, and acid-modified polypropylene layer (25 μm)/polypropylene layer (50 μm)/acid-modified polypropylene layer (25 μm) were laminated in this order. An adhesive film for metal terminals was produced.

When the cross sections of the unstretched polypropylene layers used in Examples 1 to 5 and Comparative Examples 1 and 2 were stained with ruthenium tetroxide (RuO ₄ ) and the scanning electron micrographs were observed, a sea-island structure was observed. On the other hand, when the stretched polypropylene layer used in Comparative Example 3 was similarly observed, no sea-island structure was observed.

(Manufacture of packaging materials)
An aluminum foil (thickness: 40 μm) was prepared, which was chemically treated (phosphoric acid chromate treatment) on both sides with a chemical conversion treatment liquid consisting of three components: phenol resin, fluoride chromium (trivalent) compound, and phosphoric acid. Next, one side of this aluminum foil and a biaxially stretched nylon film (thickness: 25 μm) were laminated via a urethane adhesive. Next, the other side of the aluminum foil and the unstretched polypropylene film (thickness: 30 μm) are sandwich-laminated with acid-modified polypropylene resin (thickness: 15 μm, polypropylene graft-modified with unsaturated carboxylic acid), and the acid-modified polypropylene film is coated with hot air. Packaging in which biaxially stretched nylon film (25 μm) / aluminum foil (thickness 40 μm) / acid-modified polypropylene resin (thickness 15 μm) / unstretched polypropylene film (15 μm) are laminated in this order by heating to a temperature above the softening point of the resin. manufactured the material. The seal strength described above was measured using the obtained packaging material.

In Table 1, PP means polypropylene and PPa means acid-modified polypropylene.

As shown in Table 1, it is composed of a laminate including at least one polypropylene layer and at least one acid-modified polypropylene layer, and the acid-modified polypropylene layer is on at least one side of the adhesive film for metal terminals. When the cross section of the polypropylene layer was observed using a scanning electron microscope, a sea-island structure was observed. The adhesive films for metal terminals of Examples 1 to 5, in which the total thickness of Furthermore, it can be seen that the electrolyte resistance is also excellent. On the other hand, although the polypropylene layer has the above-mentioned sea-island structure, the total thickness of the polypropylene layer is outside the range of 0.7 to 3.5 when the total thickness of the acid-modified polypropylene layer is 1. The adhesive films for metal terminals of Examples 1 and 2 had poor adhesion to the packaging material and the metal terminal. In addition, although the adhesive film for metal terminals of Comparative Example 3 satisfies the above range but does not have the above-mentioned sea-island structure in the polypropylene layer, it has good adhesion to packaging materials and metal terminals and electrolyte resistance. was inferior to In addition, in Examples 1 to 7, when the island portion area of the sea-island structure of the polypropylene layer was measured by binarization, all had a large value of 28.0% or more, and the acid-modified polypropylene layer It also had a large value of 24.5% or more. On the other hand, in Comparative Example 3, when the area of the island portion of the polypropylene layer was measured by binarization, the area ratio was a very low value of 1.57%, and the polypropylene layer had a sea-island structure. It has been confirmed that this has not been done.

1 Adhesive film for metal terminal 2 Metal terminal 3 Packaging material 3a Periphery of packaging material 4 Battery element 10 Battery 11 Polypropylene layer 12 Acid-modified polypropylene layer 31 Base layer 32 Adhesive layer 33 Barrier layer 34 Heat-fusible resin layer 35 Adhesive layer P Center S Heat sealed part

Claims (13)

An adhesive film for a metal terminal that is interposed between a metal terminal electrically connected to an electrode of a battery element and a packaging material that seals the battery element,
The adhesive film for metal terminals is composed of a laminate including at least one polypropylene layer and at least one acid-modified polypropylene layer,
The acid-modified polypropylene layer constitutes a surface layer on at least one side of the adhesive film for metal terminals,
When the cross section of the polypropylene layer was observed using an electron microscope, a sea-island structure was observed,
The sea -island structure of the polypropylene layer is a structure in which sea portions and island portions can be distinguished from the brightness when observing an electron micrograph of a cross section of the polypropylene layer stained with ruthenium tetroxide (RuO 4 ) _;
When the cross section of the acid-modified polypropylene layer was observed using an electron microscope, a sea-island structure was observed;
The sea-island structure of the acid-modified polypropylene layer is a structure in which sea portions and island portions can be distinguished from brightness when observing an electron micrograph of a cross section of the acid-modified polypropylene layer stained with ruthenium tetroxide (RuO ₄ ). In the sea-island structure of the acid-modified polypropylene layer, the area ratio of the island portion is 10% or more and 50% or less,
An adhesive film for a metal terminal, wherein the total thickness of the acid-modified polypropylene layers is 1, and the total thickness of the polypropylene layers is in the range of 0.7 or more and 3.5 or less. An adhesive film for a metal terminal that is interposed between a metal terminal electrically connected to an electrode of a battery element and a packaging material that seals the battery element,
The adhesive film for metal terminals is composed of a laminate including two polypropylene layers and at least one acid-modified polypropylene layer,
The acid-modified polypropylene layer constitutes a surface layer on at least one side of the adhesive film for metal terminals,
When the cross section of the polypropylene layer was observed using an electron microscope, a sea-island structure was observed,
The sea -island structure of the polypropylene layer is a structure in which sea portions and island portions can be distinguished from the brightness when observing an electron micrograph of a cross section of the polypropylene layer stained with ruthenium tetroxide (RuO 4 ) _;
Of the two polypropylene layers, the polypropylene layer on the acid-modified polypropylene layer side has a thickness of 50 μm or more,
An adhesive film for a metal terminal, wherein the total thickness of the acid-modified polypropylene layers is 1, and the total thickness of the polypropylene layers is in the range of 0.7 or more and 3.5 or less. The adhesive film for metal terminals according to claim 1 or 2, wherein the polypropylene layer contains block polypropylene. The adhesive film for a metal terminal according to any one of claims 1 to 3, wherein the entire polypropylene layer is made of unstretched polypropylene. The adhesive film for metal terminals according to any one of claims 1 to 4, wherein a melting peak is observed in a range of 150°C or more and 165°C or less when the adhesive film for metal terminals is measured with a differential scanning calorimeter. Adhesive film. The adhesive film for metal terminals according to any one of claims 1 to 5, wherein the adhesive film for metal terminals has a thickness residual rate of 50% or more as measured by the following measuring method.
An aluminum plate with a thickness of 100 μm and the adhesive film for metal terminals are prepared.
The thickness A (μm) of the adhesive film for metal terminals is measured.
The adhesive film for metal terminals is stacked on the center portion of the aluminum plate so that the length direction and the width direction of the aluminum plate and the adhesive film for metal terminals are aligned.
Prepare two metal plates that are longer than the length of the aluminum plate and have a width of 7 mm, and cover the entire surface of the adhesive film for metal terminals. The metal plate is heated and pressurized under the conditions of 190° C., surface pressure of 1.27 MPa, and time of 3 seconds to obtain a laminate of the aluminum plate and the metal terminal adhesive film.
The thickness B (μm) of the heated and pressurized portion of the laminate is measured.
The remaining thickness of the adhesive film for metal terminals is calculated using the following formula.
Thickness residual rate (%) of adhesive film for metal terminals = (Thickness B-100) / Thickness A x 100 The adhesive film for metal terminals according to any one of claims 1 to 6, wherein the adhesive film for metal terminals has a heat shrinkage rate of 70 to 90% in the machine direction. The packaging material is composed of a laminate including at least a base layer, a barrier layer, and a heat-fusible resin layer in this order,
The adhesive film for metal terminals according to any one of claims 1 to 7, wherein the adhesive film for metal terminals is interposed between the heat-fusible resin layer and the metal terminal. A method for producing an adhesive film for a metal terminal, which is interposed between a metal terminal electrically connected to an electrode of a battery element and a packaging material that seals the battery element, the method comprising:
comprising a step of laminating at least one polypropylene layer and at least one acid-modified polypropylene layer,
The adhesive film for metal terminals is composed of a laminate including at least one polypropylene layer and at least one acid-modified polypropylene layer,
The acid-modified polypropylene layer constitutes a surface layer on at least one side of the adhesive film for metal terminals,
When the cross section of the polypropylene layer was observed using an electron microscope, a sea-island structure was observed,
The sea -island structure of the polypropylene layer is a structure in which sea portions and island portions can be distinguished from the brightness when observing an electron micrograph of a cross section of the polypropylene layer stained with ruthenium tetroxide (RuO 4 ) _;
When the cross section of the acid-modified polypropylene layer was observed using an electron microscope, a sea-island structure was observed;
The sea-island structure of the acid-modified polypropylene layer is a structure in which sea portions and island portions can be distinguished from brightness when observing an electron micrograph of a cross section of the acid-modified polypropylene layer stained with ruthenium tetroxide (RuO ₄ ). can be,
In the sea-island structure of the acid-modified polypropylene layer, the area ratio of the island portion is 10% or more and 50% or less,
A method for producing an adhesive film for a metal terminal, wherein the total thickness of the acid-modified polypropylene layers is 1, and the total thickness of the polypropylene layers is in the range of 0.7 or more and 3.5 or less. A method for producing an adhesive film for a metal terminal, which is interposed between a metal terminal electrically connected to an electrode of a battery element and a packaging material that seals the battery element, the method comprising:
It comprises a step of laminating two polypropylene layers and at least one acid-modified polypropylene layer,
The adhesive film for metal terminals is composed of a laminate including two polypropylene layers and at least one acid-modified polypropylene layer,
The acid-modified polypropylene layer constitutes a surface layer on at least one side of the adhesive film for metal terminals,
When the cross section of the polypropylene layer was observed using an electron microscope, a sea-island structure was observed,
The sea-island structure of the polypropylene layer is a structure in which sea portions and island portions can be distinguished from the brightness when observing an electron micrograph of a cross section of the polypropylene layer stained with ruthenium tetroxide (RuO 4 ) _;
Of the two polypropylene layers, the polypropylene layer on the acid-modified polypropylene layer side has a thickness of 50 μm or more,
A method for producing an adhesive film for a metal terminal, wherein the total thickness of the acid-modified polypropylene layers is 1, and the total thickness of the polypropylene layers is in the range of 0.7 or more and 3.5 or less. A metal terminal with an adhesive film for a metal terminal, the adhesive film for a metal terminal according to any one of claims 1 to 8 being attached to a metal terminal. A battery element comprising at least a positive electrode, a negative electrode, and an electrolyte, a packaging material for sealing the battery element, and a metal terminal electrically connected to each of the positive electrode and the negative electrode and protruding to the outside of the packaging material. A battery comprising:
A battery, wherein the adhesive film for metal terminals according to any one of claims 1 to 8 is interposed between the metal terminals and the packaging material. A kit comprising a battery packaging material for use in a battery and the adhesive film for metal terminals according to any one of claims 1 to 8,
The battery includes at least a battery element including a positive electrode, a negative electrode, and an electrolyte, the battery packaging material for sealing the battery element, and electrically connected to each of the positive electrode and the negative electrode. and the metal terminal protruding outside the packaging material,
The kit is used so that the metal terminal adhesive film is interposed between the metal terminal and the battery packaging material during use.