CN110808342B - Adhesive film for metal terminal - Google Patents

Adhesive film for metal terminal Download PDF

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Publication number
CN110808342B
CN110808342B CN201911035695.6A CN201911035695A CN110808342B CN 110808342 B CN110808342 B CN 110808342B CN 201911035695 A CN201911035695 A CN 201911035695A CN 110808342 B CN110808342 B CN 110808342B
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China
Prior art keywords
adhesive film
metal terminal
layer
polypropylene
acid
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CN201911035695.6A
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CN110808342A (en
Inventor
平木健太
高萩敦子
山下力也
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Dai Nippon Printing Co Ltd
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Dai Nippon Printing Co Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/10—Primary casings; Jackets or wrappings
    • H01M50/102—Primary casings; Jackets or wrappings characterised by their shape or physical structure
    • H01M50/105—Pouches or flexible bags
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/10—Primary casings; Jackets or wrappings
    • H01M50/116—Primary casings; Jackets or wrappings characterised by the material
    • H01M50/124—Primary casings; Jackets or wrappings characterised by the material having a layered structure
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/10—Primary casings; Jackets or wrappings
    • H01M50/183—Sealing members
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B15/00—Layered products comprising a layer of metal
    • B32B15/04—Layered products comprising a layer of metal comprising metal as the main or only constituent of a layer, which is next to another layer of the same or of a different material
    • B32B15/08—Layered products comprising a layer of metal comprising metal as the main or only constituent of a layer, which is next to another layer of the same or of a different material of synthetic resin
    • B32B15/09—Layered products comprising a layer of metal comprising metal as the main or only constituent of a layer, which is next to another layer of the same or of a different material of synthetic resin comprising polyesters
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/06—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material
    • B32B27/08—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material of synthetic resin
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/32—Layered products comprising a layer of synthetic resin comprising polyolefins
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B33/00—Layered products characterised by particular properties or particular surface features, e.g. particular surface coatings; Layered products designed for particular purposes not covered by another single class
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B7/00—Layered products characterised by the relation between layers; Layered products characterised by the relative orientation of features between layers, or by the relative values of a measurable parameter between layers, i.e. products comprising layers having different physical, chemical or physicochemical properties; Layered products characterised by the interconnection of layers
    • B32B7/04—Interconnection of layers
    • B32B7/12—Interconnection of layers using interposed adhesives or interposed materials with bonding properties
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/78—Cases; Housings; Encapsulations; Mountings
    • H01G11/80—Gaskets; Sealings
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/10—Primary casings; Jackets or wrappings
    • H01M50/116—Primary casings; Jackets or wrappings characterised by the material
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/10—Primary casings; Jackets or wrappings
    • H01M50/172—Arrangements of electric connectors penetrating the casing
    • H01M50/174—Arrangements of electric connectors penetrating the casing adapted for the shape of the cells
    • H01M50/178—Arrangements of electric connectors penetrating the casing adapted for the shape of the cells for pouch or flexible bag cells
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/50—Current conducting connections for cells or batteries
    • H01M50/543—Terminals
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/50—Current conducting connections for cells or batteries
    • H01M50/543—Terminals
    • H01M50/552—Terminals characterised by their shape
    • H01M50/553—Terminals adapted for prismatic, pouch or rectangular cells
    • H01M50/557—Plate-shaped terminals
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2250/00—Layers arrangement
    • B32B2250/02—2 layers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2250/00—Layers arrangement
    • B32B2250/03—3 layers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2250/00—Layers arrangement
    • B32B2250/24—All layers being polymeric
    • B32B2250/242—All polymers belonging to those covered by group B32B27/32
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2250/00—Layers arrangement
    • B32B2250/40—Symmetrical or sandwich layers, e.g. ABA, ABCBA, ABCCBA
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2307/00—Properties of the layers or laminate
    • B32B2307/70—Other properties
    • B32B2307/714—Inert, i.e. inert to chemical degradation, corrosion
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2457/00—Electrical equipment
    • B32B2457/10—Batteries
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Sealing Battery Cases Or Jackets (AREA)
  • Laminated Bodies (AREA)
  • Electric Double-Layer Capacitors Or The Like (AREA)
  • Connection Of Batteries Or Terminals (AREA)

Abstract

The invention provides an adhesive film for a metal terminal, which has high adhesion to a packaging material and the metal terminal and is excellent in electrolyte resistance. An adhesive film for a metal terminal, which is present between a metal terminal electrically connected to an electrode of a battery element and a packaging material for sealing the battery element, wherein the adhesive film for a metal terminal is composed of a laminate comprising at least 1 polypropylene layer and at least 1 acid-modified polypropylene layer, the acid-modified polypropylene layer constitutes a surface layer on at least one surface side of the adhesive film for a metal terminal, and a sea-island structure is observed when a cross section of the polypropylene layer is observed by an electron micrograph, and wherein in the sea-island structure of the polypropylene layer, an area ratio of an island portion is 10% to 50%, and a total thickness of the polypropylene layers is 0.7 to 3.5 when the total thickness of the acid-modified polypropylene layers is 1.

Description

Adhesive film for metal terminal
The application date of the present case is12 month and 15 days 2017Application No. is201780018097.0The invention name "Metal end Adhesive film for secondary battery and batteryDivisional application of
Technical Field
The present invention relates to an adhesive film for a metal terminal and a battery.
Background
Various types of batteries have been developed, but among all batteries, a packaging material for enclosing battery elements such as electrodes, electrolytes, and the like is an indispensable component. Conventionally, metal packaging materials have been used in many cases as battery packaging bodies, but in recent years, with the increasing performance of electric vehicles, hybrid vehicles, personal computers, cameras, cellular phones, and the like, batteries are required to have various shapes, and also to be thin and lightweight. However, the metal packaging materials that are used in many cases at present have disadvantages that they are difficult to cope with the diversification of shapes and that their weight reduction is limited.
Therefore, in recent years, as a packaging material which can be easily processed into various shapes and can be made thin and light in weight, a film-shaped laminate in which a base material layer, an adhesive layer, a barrier layer, and a heat-fusible resin layer are sequentially laminated has been proposed. When such a film packaging material is used, the battery element is sealed with the packaging material by heat-sealing and heat-sealing the edge portions of the packaging material in a state where the heat-fusible resin layers located in the innermost layers of the packaging material are opposed to each other.
The metal terminals protrude from the heat-sealed portion of the packaging material, and the battery element packaged by the packaging material is electrically connected to the outside through the metal terminals electrically connected to the electrodes of the battery element. That is, of the portions of the packaging material that are heat-sealed, the portions where the metal terminals are present are heat-sealed in a state where the metal terminals are sandwiched by the heat-fusible resin layer. Since the metal terminal and the heat-fusible resin layer are made of different materials, adhesion tends to be reduced at the interface between the metal terminal and the heat-fusible resin layer.
Therefore, an adhesive film may be disposed between the metal terminal and the heat-fusible resin layer in order to improve adhesion between them.
Documents of the prior art
Patent document
Patent document 1: japanese laid-open patent publication No. 2015-79638
Disclosure of Invention
Technical problem to be solved by the invention
Such an adhesive film is required to have not only high adhesion to a packaging material and a metal terminal but also excellent resistance to an electrolyte enclosed in the packaging material.
Under such circumstances, a main object of the present invention is to provide an adhesive film for a metal terminal, which has high adhesion to a packaging material and a metal terminal and is excellent in electrolyte resistance. It is another object of the present invention to provide a battery using the adhesive film for a metal terminal.
Technical solution for solving technical problem
The present inventors have conducted intensive studies in order to solve the above-mentioned problems. As a result, it was found that an adhesive film for a metal terminal, which is present between a metal terminal electrically connected to an electrode of a battery element and a packaging material for packaging the battery element, and which is composed of a laminate comprising at least 1 polypropylene layer and at least 1 acid-modified polypropylene layer, wherein the acid-modified polypropylene layer constitutes a surface layer on at least one surface side of the adhesive film for a metal terminal, and wherein a sea-island structure is observed when a cross section of the polypropylene layer is observed by an electron microscope photograph, and wherein the total thickness of the polypropylene layer is in a range of 0.7 to 3.5 when the total thickness of the acid-modified polypropylene layer is 1, has high adhesion to the packaging material and the metal terminal, and is excellent in electrolyte resistance. The present invention has been completed based on the above findings and further studies.
That is, the present invention provides the following embodiments.
Item 1. an adhesive film for a metal terminal, which is present between a metal terminal electrically connected to an electrode of a battery element and a packaging material for packaging the battery element, wherein,
the adhesive film for a metal terminal comprises a laminate comprising at least 1 polypropylene layer and at least 1 acid-modified polypropylene layer,
the acid-modified polypropylene layer constitutes a surface layer on at least one surface side of the adhesive film for a metal terminal,
when the cross section of the polypropylene layer was observed by an electron micrograph, the sea-island structure was observed,
when the total thickness of the acid-denatured polypropylene layer is 1, the total thickness of the polypropylene layers is in the range of 0.7 to 3.5.
The adhesive film for a metal terminal according to claim 1, wherein the polypropylene layer contains block polypropylene.
The adhesive film for a metal terminal according to claim 1 or 2, wherein the polypropylene layer is composed of an unstretched polypropylene.
The adhesive film for a metal terminal according to any one of claims 1 to 3, wherein the polypropylene layer has a laminated structure in which a layer composed of atactic polypropylene, a layer composed of block polypropylene and a layer composed of atactic polypropylene are laminated in this order.
The adhesive film for a metal terminal according to any one of items 1 to 4, wherein a melting peak is observed in a range of 150 ℃ to 165 ℃ when the adhesive film for a metal terminal is measured by a differential scanning calorimeter.
The adhesive film for a metal terminal according to any one of claims 1 to 5, wherein the adhesive film for a metal terminal has a thickness residual ratio of 50% or more as measured by the following measurement method:
preparing an aluminum plate having a thickness of 100 μm and the adhesive film for the metal terminal;
measuring the thickness A (μm) of the adhesive film for a metal terminal;
stacking the adhesive film for metal terminals on a central portion of the aluminum plate so that a longitudinal direction and a width direction of the aluminum plate and the adhesive film for metal terminals are aligned;
preparing 2 metal plates having a length longer than the aluminum plate and a width of 7mm, and heating and pressing the metal plates from the upper and lower sides of the aluminum plate and the adhesive film for metal terminals under conditions of a temperature of 190 ℃, a surface pressure of 1.27MPa, and a time of 3 seconds to obtain a laminate of the aluminum plate and the adhesive film for metal terminals, so as to cover the entire surface of the adhesive film for metal terminals;
measuring the thickness B (mum) of the heated and pressed part of the laminated body;
the residual thickness ratio of the adhesive film for metal terminals was calculated by the following equation,
the adhesive film for a metal terminal has a residual thickness ratio (%) (thickness B-100)/thickness a × 100.
The adhesive film for a metal terminal according to any one of claims 1 to 6, wherein the heat shrinkage rate in the flow direction of the adhesive film for a metal terminal is 70 to 90%.
The adhesive film for a metal terminal according to any one of claims 1 to 7, wherein the packaging material is composed of a laminate comprising at least a base material layer, a barrier layer and a heat-fusible resin layer in this order,
the adhesive film for metal terminals is present between the heat-fusible resin layer and the metal terminals.
The battery according to item 9, comprising: a battery element including at least a positive electrode, a negative electrode, and an electrolyte; a packaging material for packaging the battery element; and a metal terminal electrically connected to the positive electrode and the negative electrode, respectively, and protruding outside the packaging material, wherein the adhesive film for a metal terminal according to any one of items 1 to 8 is present between the metal terminal and the packaging material.
Item 10. use of a laminate comprising at least 1 polypropylene layer and at least 1 acid-modified polypropylene layer as an adhesive film for a metal terminal,
the acid-modified polypropylene layer constitutes a surface layer on at least one surface side of the adhesive film for a metal terminal,
when the cross section of the polypropylene layer was observed by electron micrographs, a sea-island structure was observed,
when the total thickness of the acid-modified polypropylene layers is 1, the total thickness of the polypropylene layers is in the range of 0.7 to 3.5,
the adhesive film for metal terminals is present between the metal terminals electrically connected to the electrodes of the battery element and the packaging material for sealing the battery element.
ADVANTAGEOUS EFFECTS OF INVENTION
The present invention can provide an adhesive film for a metal terminal, which has high adhesion to a packaging material and a metal terminal and is excellent in electrolyte resistance. Further, the present invention can provide a battery using the adhesive film for a metal terminal.
Drawings
Fig. 1 is a schematic top view of a battery of the present invention.
Fig. 2 is a schematic sectional view taken along line a-a' of fig. 1.
Fig. 3 is a schematic sectional view taken along line B-B' of fig. 1.
Fig. 4 is a schematic sectional view of the adhesive film for a metal terminal of the present invention.
Fig. 5 is a schematic sectional view of the adhesive film for metal terminals of the present invention.
Fig. 6 is a schematic sectional view of a packaging material for a battery of the present invention.
Fig. 7 is a schematic diagram for explaining a method of measuring the seal strength of the example.
Fig. 8 is a schematic diagram for explaining a method of measuring the seal strength of the example.
Fig. 9 is a schematic diagram for explaining a method of measuring the seal strength of the example.
Fig. 10 is a schematic diagram for explaining a method of measuring the seal strength of the example.
FIG. 11 is a transmission electron microscope photograph (scale bar: 5 μm) shown with "C" on page 29 of "shape and function of polymer 1. molecular assembly seen by eye of polymer microphotograph" (editor: society of society, publisher: Shanben, release unit: Kagaku culture shop, Showa and 61 years, first edition release at 5.30.g.).
Detailed Description
The adhesive film for a metal terminal of the present invention is present between a metal terminal electrically connected to an electrode of a battery element and a packaging material for sealing the battery element, and is characterized in that the adhesive film for a metal terminal is composed of a laminate comprising at least 1 polypropylene layer and at least 1 acid-modified polypropylene layer, the acid-modified polypropylene layer constitutes a surface layer on at least one surface side of the adhesive film for a metal terminal, a sea-island structure is observed when a cross section of the polypropylene layer is observed by an electron micrograph, and the total thickness of the polypropylene layers is in the range of 0.7 to 3.5 when the total thickness of the acid-modified polypropylene layers is 1. The adhesive film for a metal terminal of the present invention and the battery of the present invention using the same will be described in detail below.
In the present specification, the numerical ranges indicated by "to" mean "above" and "below". For example, the expression of 2 to 15mm means 2mm to 15 mm.
1. Adhesive film for metal terminal
The adhesive film for a metal terminal of the present invention is present 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 fig. 1 to 3, for example, the adhesive film 1 for a metal terminal of the present invention is present between a metal terminal 2 electrically connected to an electrode of a battery element 4 and a packaging material 3 for packaging the battery element 4. The metal terminal 2 protrudes outside the packaging material 3, and is sandwiched between the packaging material 3 and the metal terminal adhesive film 1 at the edge 3a of the heat-sealed packaging material 3. In the present invention, the heat at the time of heat-sealing the packaging material is usually in the range of about 160 to 220 ℃ and the pressure is usually in the range of about 0.5 to 2.0 MPa.
The adhesive film 1 for a metal terminal of the present invention is provided to improve the adhesion between the metal terminal 2 and the packaging material 3. By improving the adhesion between the metal terminal 2 and the packaging material 3, the sealing property of the battery element 4 is improved. As described above, when the battery element 4 is heat-sealed, the battery element is sealed in such a manner that the metal terminals 2 electrically connected to the electrodes of the battery element 4 protrude outside the packaging material 3. At this time, since the metal terminal 2 made of metal and the heat-fusible resin layer 34 (a layer made of a heat-fusible resin such as polyolefin) located at the innermost layer of the packaging material 3 are made of different kinds of materials, the sealing property of the battery element tends to be lowered at the interface between the metal terminal 2 and the heat-fusible resin layer 34 without using an adhesive film. Even if an adhesive film is used, if the adhesive film has low electrolyte resistance, the sealing property of the battery element tends to be low.
For example, as shown in fig. 4 and 5, the adhesive film 1 for a metal terminal of the present invention is composed of a laminate having at least 1 polypropylene layer 11 and at least 1 acid-modified polypropylene layer 12, the acid-modified polypropylene layer 12 constitutes a surface layer of the adhesive film 1 for a metal terminal on at least one surface side, a sea-island structure is observed when a cross section of the polypropylene layer 11 is observed by an electron micrograph, and the total thickness of the polypropylene layer 11 is set within a range of 0.7 to 3.5 when the total thickness of the acid-modified polypropylene layers 12 is 1. Thus, the adhesive film 1 for a metal terminal of the present invention has high adhesion to a packaging material and a metal terminal, and is excellent in electrolyte resistance, and therefore, the sealing properties of a battery element can be effectively improved.
From the viewpoint of further improving the adhesion to the packaging material and the metal terminal and further improving the electrolyte resistance, the total thickness of the polypropylene layer 11 when the total thickness of the acid-modified polypropylene layer 12 is defined as 1 is preferably in the range of about 0.75 to 3.2, more preferably about 0.8 to 2.0.
In the adhesive film 1 for a metal terminal of the present invention, the acid-denatured polypropylene layer 12 constitutes a surface layer on at least one surface side of the adhesive film for a metal terminal. The acid-modified polypropylene layer 12 made of acid-modified polypropylene has superior adhesion to a metal material as compared with the polypropylene layer 11 made of polypropylene. Therefore, the adhesive film 1 for a metal terminal of the present invention is disposed between the metal terminal 2 and the packaging material 3 so that the acid-modified polypropylene layer 12 is positioned on the metal terminal 2 side, and the sealing property of the battery element can be effectively improved.
The adhesive film 1 for a metal terminal of the present invention may be formed by providing at least 1 polypropylene layer 11 and at least 1 acid-modified polypropylene layer 12. As a preferable lamination structure of the adhesive film 1 for a metal terminal of the present invention, for example, a structure in which each 1 layer of the polypropylene layer 11 and the acid-modified polypropylene layer 12 is laminated as shown in fig. 4, and a structure in which each 1 layer of the acid-modified polypropylene layer 12 is laminated on both surfaces of the polypropylene layer 11 as shown in fig. 5, and the like can be cited. As will be described later, a plurality of layers made of the same or different polypropylenes may be continuously laminated in the 1-layer polypropylene layer 11, and the plurality of layers may constitute the 1-layer polypropylene layer 11. Also, a plurality of layers composed of the same or different acid-modified polypropylene may be continuously laminated in the 1 acid-modified polypropylene layer 12, and the plurality of layers constitute the 1 acid-modified polypropylene layer 12.
Specific examples of a preferable lamination structure of the adhesive film 1 for a metal terminal of the present invention include: 2-layer structure of acid modified polypropylene layer 12/polypropylene layer 11; sequentially laminating 3 layers of acid modified polypropylene layer 12/polypropylene layer 11/acid modified polypropylene layer 12; the 5-layer structure of the acid-modified polypropylene layer 12/polypropylene layer 11/acid-modified polypropylene layer 12, etc. are laminated in this order, and among these, the 2-layer structure of the acid-modified polypropylene layer 12/polypropylene layer 11 and the 3-layer structure of the acid-modified polypropylene layer 12/polypropylene layer 11/acid-modified polypropylene layer 12 are more preferable.
The adhesive film 1 for a metal terminal of the present invention is preferably composed of polyolefin in all layers. More specifically, the adhesive film 1 for a metal terminal of the present invention is also preferably configured to include only the acid-modified polypropylene layer 12 and the polypropylene layer 11, and is also preferably configured to further include another polyolefin layer made of polyolefin. Specific examples of the polyolefin constituting the polyolefin layer include polyethylene and acid-modified polyethylene. In the acid-modified polyethylene, the component for acid-modifying the ethylene is not particularly limited, and examples thereof include unsaturated carboxylic acids and acid anhydrides thereof for acid modification exemplified in the acid-modified polypropylene layer 12 described later.
The thickness of the adhesive film 1 for a metal terminal of the present invention is not particularly limited, but is preferably about 40 to 200 μm, more preferably about 55 to 150 μm, and even more preferably about 60 to 110 μm, from the viewpoint of further improving the adhesion to a packaging material and a metal terminal and further improving the electrolyte resistance.
In addition, from the viewpoint of further improving the adhesion to the packaging material and the metal terminal and further improving the electrolyte solution resistance, when the adhesive film 1 for a metal terminal of the present invention is measured using a differential scanning calorimeter, it is preferable that a melting peak is observed in the range of 150 to 165 ℃.
From the same viewpoint, the adhesive film 1 for a metal terminal of the present invention preferably has a thickness residual ratio of about 50% or more, preferably about 55% or more, and preferably about 60% or more, as measured by the following measurement method. The upper limit of the thickness residual ratio is preferably about 90% or less, preferably about 85% or less, and preferably about 80% or less. The thickness residual ratio 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%. By using the adhesive film 1 for a metal terminal having a residual rate of 50% or more, short-circuiting between the barrier layer contained in the packaging material and the metal terminal can be effectively suppressed, and the adhesion between the packaging material and the adhesive film for a metal terminal can be further improved. By using the adhesive film 1 for a metal terminal having a residual ratio of 90% or less, the shape of the step of the metal terminal can be satisfactorily followed, and the end of the metal terminal can be satisfactorily covered.
(measurement of residual ratio of thickness of adhesive film for Metal terminal)
An aluminum plate (pure aluminum, JIS H4160-1994A 1N 30H-O) having a thickness of 100 μm and an adhesive film for a metal terminal were prepared. The thickness a (μm) of the adhesive film for metal terminals was measured by a micrometer. The adhesive film for metal terminals is laminated on the central portion of the aluminum plate so that the longitudinal direction and the width direction of the aluminum plate and the adhesive film for metal terminals coincide with each other. At this time, the acid-modified polypropylene layer of the adhesive film for metal terminals was disposed in contact with the aluminum plate. 2 pieces of metal plates having a length longer than that of the aluminum plate and a width of 7mm were prepared, and heat and pressure were applied from both upper and lower sides of the aluminum plate and the adhesive film for metal terminals under conditions of a temperature of 190 ℃, a surface pressure of 1.27MPa, and a time of 3 seconds so as to cover the entire surface of the adhesive film for metal terminals, thereby obtaining a laminate of the aluminum plate and the adhesive film for metal terminals. The thickness B (μm) of the heated and pressed portion of the laminate was measured by a micrometer. The thickness residual ratio of the adhesive film for metal terminals was calculated by the following equation.
The adhesive film for metal terminals has a residual thickness ratio (%) (thickness B-100)/thickness A × 100
The longitudinal direction is a long side direction corresponding to a long side of the object in a plan view, and the width direction is a short side direction corresponding to a short side of the object in a plan view. When the sizes in the longitudinal direction and the width direction are the same (square), the longitudinal direction and the width direction can be arbitrarily determined.
In the measurement of the residual ratio, a pressure load was applied so that the surface pressure became 1.27MPa depending on the area of the adhesive film for metal terminals. Specifically, the pressure load (N) can be applied by [ using a metal plate ]]Area of adhesive film for pressure metal terminal (mm) 2 )]The formula is expressed in terms of surface pressure (MPa). The pressing load (N) by the metal plate can be adjusted according to the diameter and the air pressure of a cylinder for adjusting the pressure of the metal plate.
In the measurement of the thickness residual ratio of the adhesive film for metal terminals, if the measurement is performed under the conditions of the temperature of 190 ℃, the surface pressure of 1.27MPa, and the time of 3 seconds, the length and the width of the adhesive film for metal terminals and the aluminum plate are not limited, and for example, when the measurement is possible using the adhesive film for metal terminals having the length of 70mm and the width of 5mm (the measurement may be performed by a method such as cutting), the thickness residual ratio of the adhesive film for metal terminals can be measured favorably using the adhesive film for metal terminals having the size and the aluminum plate having the length of 60mm and the width of 25 mm. Note that [ area of adhesive film for pressure metal terminal (mm) ] 2 )]The area of the portion where the aluminum plate and the adhesive film for metal terminal overlap each other is, for example, the above-mentioned size of the area of the adhesive film for metal terminalIn the case of the plastic film and the aluminum plate, the area is 60mm × 5 mm. Further, the thickness of the aluminum plate is not substantially changed by heating and pressing when a laminate of the aluminum plate and the adhesive film for metal terminals is obtained. Even if the size of the adhesive film for metal terminals to be measured is different, the size of the aluminum plate may not be changed as long as the measurement can be performed.
The melt Mass Flow Rate (MFR) of the entire adhesive film 1 for a metal terminal of the present invention is not particularly limited, but is preferably about 1 to 15, more preferably about 2 to 12, and even more preferably about 3 to 10, from the viewpoint of further improving the adhesion to a packaging material and a metal terminal and further improving the electrolyte resistance. The melt Mass Flow Rate (MFR) of the entire adhesive film 1 for metal terminals is a value in accordance with JIS K7210: 2014 under a load of 2.16kg at a measurement temperature of 230 ℃ and measured using a melt index meter.
The heat shrinkage (%) in the flow direction (MD) of the adhesive film 1 for metal terminals according to the present invention may preferably be about 70% or more in the lower limit, more preferably about 75% or more, even more preferably about 80% or more in the upper limit, and may preferably be about 95% or less, more preferably about 92% or less, even more preferably about 90% or less in the upper limit. The range of the thermal shrinkage (%) is preferably about 70 to 95%, about 70 to 92%, about 70 to 90%, about 75 to 95%, about 75 to 92%, about 75 to 90%, about 80 to 95%, about 80 to 92%, and about 80 to 90%. The heat shrinkage (%) was measured as follows.
(method of measuring Heat shrinkage (%) in the test paper)
The adhesive film for a metal terminal was cut into a size of 50Mm (MD) by 4mm (TD) in length as a test piece. Next, the length M (mm) of the test piece was measured using a metal ruler. Next, the end of the test piece in the longitudinal direction was fixed to a metal mesh with an adhesive tape, and the test piece was suspended on the metal mesh. In this state, the test piece was placed in a furnace heated to 190 ℃ for 120 seconds, then taken out together with the metal mesh, and naturally cooled at room temperature (25 ℃). Next, the length n (mm) of the test piece naturally cooled to room temperature was measured using a metal ruler. The thermal shrinkage of the adhesive film for a metal terminal was calculated by the following formula.
Heat shrinkage (%) (length N/length M) × 100
When the battery element is sealed and heat-sealed in a state in which the metal terminal adhesive film is sandwiched between the metal terminal and the packaging material, there are a portion where the metal terminal adhesive film does not undergo dimensional change due to pressure from the metal plate used for heat sealing, and a portion where the metal terminal adhesive film is separated from the metal plate and does not undergo pressure-induced shrinkage. In this case, the portion to which no pressure is applied is also appropriately thermally shrunk to the portion to which pressure is applied, and thus the thickness of the portion to which pressure is applied can be effectively suppressed 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 for metal terminals may move due to the heat shrinkage in a warm-up step or the like before the adhesive film 1 for metal terminals is provided on the metal terminals and heat-sealed, and the positional relationship between the metal terminals and the adhesive film for metal terminals may be deviated. Therefore, the adhesive film 1 for a metal terminal of the present invention preferably has a suitable heat shrinkage rate. As a suitable heat shrinkage rate of the adhesive film 1 for a metal terminal of the present invention, for example, the lower limit value of the heat shrinkage rate (%) in the flow direction (MD) may be 70% or more.
(Polypropylene layer 11)
In the present invention, the polypropylene layer 11 is a layer composed of polypropylene. When the cross section of the polypropylene layer 11 was observed by an electron micrograph, a sea-island structure was observed. The cross section of the polypropylene layer 11 shows a sea-island structure, and for example, as shown in an electron micrograph in fig. 11, sea portions and island portions are observed. FIG. 11 is a transmission electron micrograph (5 μm scale bar) shown by "C" on page 29 of "shape and function of Polymer 1. molecular aggregate" visually observed in Micromicrograph of Polymer "(compiler: society of society, publisher: Shanben, issue Unit: Kagaku culture shop, Showa and first edition issue at 5/30/61). As shown in fig. 11, in the cross section of the polypropylene layer 11The sea-island structure can be formed by using osmium tetroxide (OsO) in the cross-section of the polypropylene layer 4 ) After staining, the staining was confirmed by electron micrograph observation. Although the sea portion is brighter than the island portion in fig. 11, the sea portion may appear darker than the island portion depending on the measurement method and conditions. In any case, as long as the sea portion and the island portion can be distinguished, the area ratio of the island portion 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, and is preferably about 10 to 50%, more preferably about 20 to 40%, from the viewpoint of further improving the adhesion to the packaging material and the metal terminal and further improving the electrolyte resistance. The method of measuring the area ratio of the island portion in the sea-island structure of the polypropylene layer 11 is as follows. When the island portion area ratio is 2% or less, it can be evaluated that the island structure is not substantially present.
(method of measuring the area ratio of island portion in island-and-island Structure)
An adhesive film for a metal terminal is embedded in a thermosetting epoxy resin and cured. A section in the desired direction (section along TD) was produced using a commercially available rotary microtome (UC 6 manufactured by LEICA) and a diamond knife, and at this time, a section was produced at-70 ℃ using a freezing microtome using liquid nitrogen. Evening-th dyed with ruthenium tetroxide along with the embedding resin. Since the dyed polypropylene was swollen, the swollen portion was trimmed off with a microtome, and a portion of about 1 to 2 μm was further cut out to a thickness of about 100nm and observed as follows. The stained section was observed with a field emission scanning electron microscope (for example, S-4800 TYPE1 manufactured by Hitachi High-Technologies Corporation, measurement condition: 3kV20mA High WD6mm detector (Upper)) to obtain an image (magnification: 10000 times). Next, image processing software capable of binarizing an image (for example, a trigeminal image analysis software WinROOF (ver7.4)) is used to binarize island portions and sea portions of a sea-island structure of the image and determine the ratio of the area occupied by the island portions (the total area of the island portions/the area of the measurement range of the image).
When the cross section of the polypropylene layer 11 is observed by an electron micrograph, the sea-island structure is observed, and the cold resistance strength can be improved while maintaining the excellent heat resistance of the adhesive film for a metal terminal. In addition, the adhesiveness to the packaging material and the metal terminal is improved, and the electrolyte resistance is further improved.
In the present invention, the polypropylene layer 11 is preferably made of unstretched polypropylene. The polypropylene layer 11 is composed of non-stretched polypropylene, but not of stretched polypropylene, and this can be confirmed by analyzing the polypropylene layer 11 by X-ray diffraction. Specifically, when the wide-angle X-ray diffraction of the polypropylene layer 11 made of the unstretched polypropylene is measured, the ratio of the peak intensity corresponding to the 110 plane of the polypropylene crystal to the peak intensity corresponding to the 040 plane (peak intensity of 040 plane/peak intensity of 110 plane) calculated from the diffraction pattern of the polypropylene crystal is in the range of 0.5 to 1.5, and the polypropylene layer made of the stretched polypropylene is out of this range. That is, in the present invention, the polypropylene layer 11 is composed of polypropylene having a ratio of a peak intensity corresponding to the 110 plane of the polypropylene crystal to a peak intensity corresponding to the 040 plane (peak intensity of 040 plane/peak intensity of 110 plane) in the range of 0.5 to 1.5 as calculated from a diffraction pattern of the polypropylene crystal in the measurement of wide-angle X-ray diffraction.
The peak corresponding to 110 plane appeared in the vicinity of 14 ° 2 θ, and the peak corresponding to 040 plane appeared in the vicinity of 17 °. The measurement conditions using wide-angle X-ray diffraction were: Soller/PCS (angle of opening of incident parallel slit): 5.0deg, IS Long side (Long side limits slit length): 10.0mm, PSA open (open angle of light-receiving PSA), Soller (open angle of light-receiving parallel slit): 5.0deg, 2 θ/θ: 2-40 deg, step by step of 0.04 deg.
Note that the polypropylene layer 11 is formed of non-stretched polypropylene, and is not formed of stretched polypropylene, and this can be confirmed by analyzing the polypropylene layer 11 by raman spectroscopy. Specifically, when the polypropylene layer was analyzed by Raman spectroscopy, it appeared at about 809cm －1 Crystals of (2)The height "A" of the intensity of the sexual peak occurs at about 842cm －1 When the ratio (a/B) of the height "B" of the amorphous peak intensity of (a) is 1.6 or less, it can be confirmed that the polypropylene layer 11 is composed of unstretched polypropylene. The measurement conditions were laser wavelength 633nm, grating 600gr/mm, confocal aperture 100 μm, microscope lens 10 times, exposure time 15sec, cumulative number 1 time, and raman spectrum was measured on a cross section parallel to the MD (Machine Direction) of the polypropylene layer 11 so that the MD is parallel to the incident laser polarization plane. In addition, the connection length is 710cm －1 And 925cm －1 The straight line of (2) is taken as a base line. Analysis conditions were 809cm after baseline correction －1 And 842cm －1 The peak height at (b) was calculated as the peak intensity. Note that the peak appears at about 809cm as described above －1 The height "a" of the peak intensity of crystallinity of (1) is a peak attributed to a combination pattern of main chain CC stretching and CH3 variable angle shaking. In addition, it occurs at about 842cm －1 The height "B" of the amorphous peak intensity of (a) is a peak attributed to the CH3 mode of angular variation.
In the present invention, the MD of the polypropylene layer 11 is confirmed as follows. The sea-island structure was confirmed by observing each of the cross section in the longitudinal direction of the polypropylene layer 11 and each of the cross sections in the direction perpendicular to the cross section in the longitudinal direction (10 cross sections in total) by changing the angle by 10 degrees from the cross section in the longitudinal direction to the cross section in the direction parallel to the cross section in the longitudinal direction by an electron micrograph. Next, the shape of each island was observed for each cross section. The shape of each island is defined as a diameter y, which is a straight line distance connecting a leftmost end in a direction perpendicular to the thickness direction of the polypropylene layer 11 and a rightmost end in the perpendicular direction. For each cross section, when the paths y of the island shape are sorted from large to small, the average of the maximum 20 paths y is calculated. The direction parallel to the cross section of the island shape with the average maximum diameter y is determined as MD.
The polypropylene contained in the polypropylene layer 11 is preferably crystalline or amorphous polypropylene such as homopolypropylene, a block copolymer of polypropylene (for example, a block copolymer of propylene and ethylene), a random copolymer of polypropylene (for example, a random copolymer of propylene and ethylene), or the like. The composition of the sea-island structure of the polypropylene layer 11 includes, for example: the polypropylene layer 11 contains a composition of a block copolymer of polypropylene; a composition containing a block copolymer of polypropylene and a random copolymer of polypropylene; contains homopolypropylene, atactic polypropylene and polyethylene. Of these, the polypropylene layer 11 more preferably contains block polypropylene, and still more preferably consists of block polypropylene. Among them, the proportion of propylene contained in the block polypropylene is preferably about 10 to 90 mass%, more preferably about 30 to 80 mass%.
In the adhesive film 1 for a metal terminal of the present invention, the polypropylene layer 11 may be only 1 layer, or 2 or more layers. In addition, a plurality of layers made of the same or different polypropylenes may be continuously laminated in the 1 polypropylene layer 11, and the plurality of layers may constitute the 1 polypropylene layer 11. The polypropylene layer 11 preferably contains a layer composed of block polypropylene.
As a preferred embodiment of the 1-layer polypropylene layer 11, a laminate of a layer composed of random polypropylene and a layer composed of block polypropylene is preferred, and a laminate structure (3-layer structure) in which a layer composed of random polypropylene, a layer composed of block polypropylene and a layer composed of random polypropylene are laminated in this order is particularly preferred.
In the present invention, when a plurality of layers made of polypropylene are continuously laminated, these layers are collectively referred to as a 1-layer polypropylene layer 11. Similarly, in the case where a plurality of layers made of acid-modified polypropylene are continuously laminated, these layers are collectively referred to as 1 acid-modified polypropylene layer 12.
The thickness of the 1-layer polypropylene layer 11 is not particularly limited as long as the total thickness of the polypropylene layer 11 is in the range of 0.7 to 3.5, based on the total thickness of the acid-modified polypropylene layer 12 being 1, and is preferably about 15 to 80 μm, more preferably about 20 to 70 μm, from the viewpoint of further improving the adhesion to the packaging material and the metal terminal and further improving the electrolyte resistance. Although the detailed mechanism is not clear, when the thickness of the acid-modified polypropylene layer is too large, the acid-modified polypropylene layer tends to be easily broken by aggregation, and the adhesiveness to the adhesive film for a metal terminal tends to be easily lowered.
From the viewpoint of further improving the adhesion to the packaging material and the metal terminal and further improving the electrolyte solution resistance, the polypropylene layer 11 in the adhesive film 1 for the metal terminal preferably occupies about 40% or more, more preferably about 45% or more, of the thickness of the adhesive film 1 for the metal terminal, and as an upper limit, the polypropylene layer 11 preferably occupies about 85% or less, more preferably about 80% or less, of the thickness of the adhesive film 1 for the metal terminal. The preferred range of the thickness of the polypropylene layer 11 is about 40 to 85%, and about 45 to 80% based on the thickness of the adhesive film 1 for metal terminals.
The melting peak temperature of the polypropylene layer 11 is not particularly limited, and from the viewpoint of further improving the adhesion to the packaging material and the metal terminal and further improving the electrolyte resistance, it is preferably about 140 to 165 ℃, and more preferably about 150 to 160 ℃. In the present invention, the melting peak temperature of the polypropylene layer 11 is measured by a Differential Scanning Calorimeter (DSC), the temperature rise rate is 10 ℃/min, the temperature measurement range is-50 to 200 ℃, and the measurement is performed using an aluminum pan as a sample pan.
(acid-modified Polypropylene layer 12)
In the present invention, the acid-modified polypropylene layer 12 is a layer composed of acid-modified polypropylene. It is also preferable that the acid-modified polypropylene layer 12 has a sea-island structure when a cross section is observed using an electron micrograph. The method of confirming the sea-island structure in the acid-modified polypropylene layer 12 is the same as that in the polypropylene layer 11 described above.
In the sea-island structure of the acid-modified polypropylene layer 12, the area ratio of the island portion is not particularly limited, and is preferably about 10 to 50%, more preferably about 20 to 40%, from the viewpoint of further improving the adhesion to the packaging material and the metal terminal and further improving the electrolyte resistance. 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 object to be measured is the acid-modified polypropylene layer 12. When the island portion area ratio is 2% or less, it is evaluated that the island structure is not substantially present.
The acid-modified polypropylene is not particularly limited as long as it is an acid-modified polypropylene, and a polypropylene graft-modified with an unsaturated carboxylic acid or an acid anhydride thereof 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.
Examples of the acid-modified polypropylene include crystalline and amorphous polypropylenes such as homopolypropylene, a block copolymer of polypropylene (for example, a block copolymer of propylene and ethylene), and a random copolymer of polypropylene (for example, a random copolymer of propylene and ethylene). Of these, a block copolymer containing polypropylene (block polypropylene) or a random copolymer containing polypropylene (random polypropylene) is preferable. The acid-modified polypropylene layer 12 can be analyzed by an infrared spectroscopy method, a gas chromatography-mass spectrometry method, or the like, and the analyzing method is not particularly limited. For example, when maleic anhydride-modified polypropylene is measured by infrared spectroscopy, the wavenumber is 1760cm －1 Neighborhood and wavenumber 1780cm －1 Peaks derived from maleic anhydride were detected in the vicinity. However, when the acid modification degree is low, the peak becomes small and may not be detected. In this case, the analysis can be performed by nuclear magnetic resonance spectroscopy.
In the adhesive film 1 for a metal terminal of the present invention, the acid-modified polypropylene layer 12 may be only 1 layer, or 2 or more layers. Further, a plurality of layers made of the same or different acid-denatured polypropylene may be continuously laminated in the 1 acid-denatured polypropylene layer 12, and the plurality of layers may constitute the 1 acid-denatured polypropylene layer 12.
As a preferred embodiment of the 1 acid-modified polypropylene layer 12, a layer composed of maleic anhydride-modified polypropylene can be mentioned.
The thickness of the 1-layer acid-modified polypropylene layer 12 is not particularly limited as long as the total thickness of the polypropylene layer 11 is in the range of 0.7 to 3.5 when the total thickness of the acid-modified polypropylene layer 12 is 1, but from the viewpoint of further improving the adhesion to the packaging material and the metal terminal and further improving the electrolyte resistance, it is preferably about 10 μm or more, more preferably about 15 μm or more, and the upper limit thereof is preferably about 40 μm or less, more preferably about 35 μm or less, and further preferably about 30 μm or less.
The melting peak temperature of the acid-modified polypropylene layer 12 is not particularly limited, and from the viewpoint of further improving the adhesion to a packaging material or a metal terminal and further improving the electrolyte resistance, it is preferably about 130 to 165 ℃, more preferably about 140 to 160 ℃. In the present invention, the melting peak temperature of the acid-modified polypropylene layer 12 is a value measured by the same method as the method for measuring the melting peak temperature of the polypropylene layer 11.
From the viewpoint of suppressing the pressure-holding of the adhesive film for a metal terminal at the time of heat sealing and improving the sealing strength, in the adhesive film 1 for a metal terminal of the present invention, the upper limit is preferably about 40 ℃ or less, more preferably about 30 ℃ or less, further preferably about 20 ℃ or less, and the lower limit is preferably about 0 ℃ or more, more preferably about 5 ℃ or more, further preferably about 10 ℃ or more, as the absolute value of the difference between the softening point of the polypropylene layer 11 and the softening point of the acid-modified polypropylene layer 12. The softening points of the polypropylene layer 11 and the acid-modified polypropylene layer 12 are values measured by the following procedure.
(method of measuring softening Point)
The temperature was measured at a temperature rise rate of 5 ℃ per second using a scanning thermal microscope (NanoTA manufactured by Anasys) with a cantilever type of a thermal probe EX-AN 2-200. In addition, the softening point is the peak top temperature.
The adhesive film 1 for a metal terminal of the present invention may contain various additives such as a lubricant, an antioxidant, an ultraviolet absorber, and a light stabilizer, if necessary. Depending on the type and content of the additive, the adhesive film 1 for metal terminals may be discolored.
The content of the lubricant contained in the entire adhesive film 1 for metal terminals is preferably about 0 to 2000 ppm.
(measurement of slip dose)
The content of the lubricant contained in the entire adhesive film 1 for a metal terminal was measured by a gas chromatography mass spectrometer (GC-MS). Specifically, the additive in the adhesive film for metal terminals was extracted into methanol in a boiling reflux, and the obtained methanol extract was analyzed by GC-MS to measure the amount of lubricant contained in the entire adhesive film for metal terminals.
The lubricant is not particularly limited, but preferably an amide-based lubricant is used. Specific examples of the amide-based lubricant include saturated fatty acid amides, unsaturated fatty acid amides, substituted amides, methylol amides, saturated fatty acid bisamides, and unsaturated fatty acid bisamides. Specific examples of the saturated fatty acid amide include lauramide, palmitamide, stearamide, behenamide, and hydroxystearamide. Specific examples of the unsaturated fatty acid amide include oleamide and erucamide. Specific examples of the substituted amide include N-oleyl palmitamide, N-stearyl stearamide, N-stearyl oleamide, N-oleyl stearamide, N-stearyl erucamide and the like. Specific examples of the methylolamide include methylolstearylamide and the like. Specific examples of the saturated fatty acid bisamide include methylene bisstearamide, ethylene biscapramide, ethylene bislauramide, ethylene bisstearamide, ethylene bishydroxystearamide, ethylene bisbehenamide, hexamethylene bisstearamide, hexamethylene bisbehenamide, hexamethylene hydroxystearamide, N '-distearyldiadipamide, N' -distearyldisebacamide, and the like. Specific examples of the unsaturated fatty acid bisamide include ethylene bisoleamide, ethylene biserucamide, hexamethylene bisoleamide, N '-dioleyl adipamide, N' -dioleyl sebacamide, and the like. Specific examples of the fatty acid ester amide include stearamide ethyl stearate. Specific examples of the aromatic bisamide include xylylene bisstearamide, xylylene bishydroxystearamide, and N, N' -distearyl isophthalamide. The number of the lubricants may be 1 or 2 or more.
The adhesive film 1 for a metal terminal of the present invention may contain a filler as needed. By including the filler in the adhesive film 1 for a metal terminal, the filler functions as a Spacer (Spacer), and therefore, short circuit between the metal terminal 2 and the barrier layer 33 of the packaging material 3 can be more effectively suppressed. The particle size of the filler is, for example, about 0.1 to 35 μm, preferably about 5.0 to 30 μm, and more preferably about 10 to 25 μm. When a filler is added to the adhesive film 1 for a metal terminal, the filler is preferably contained in the polypropylene layer 11 and/or the acid-modified polypropylene layer 12, and the content of the filler is preferably about 5 to 30 parts by mass, more preferably about 10 to 20 parts by mass, per 100 parts by mass of the resin components forming the polypropylene layer 11 and the acid-modified polypropylene layer 12.
As the filler, any of inorganic and organic fillers can be used. Examples of the inorganic filler include: carbon (carbon, graphite), silica, alumina, barium titanate, iron oxide, silicon carbide, zirconia, zirconium silicate, magnesium oxide, titanium oxide, calcium aluminate, calcium hydroxide, aluminum hydroxide, magnesium hydroxide, calcium carbonate, and the like. Examples of the organic filler include: fluorine resins, phenol resins, urea resins, epoxy resins, acrylic resins, benzoguanamine-formaldehyde condensates, melamine-formaldehyde condensates, polymethyl methacrylate crosslinked products, polyethylene crosslinked products, and the like. From the viewpoint of shape stability, rigidity, and content resistance, alumina, silica, fluorine resin, acrylic resin, and benzoguanamine/formaldehyde condensate are preferable, and spherical alumina and silica are particularly preferable among these. As a mixing method for mixing a filler with a resin component for forming the polypropylene layer 11 and/or the acid-modified polypropylene layer 12, a method of melt-blending both components using a banbury mixer or the like in advance to make a master batch to a predetermined mixing ratio, a method of directly mixing the components with the resin component, or the like can be employed.
The adhesive film 1 for metal terminals may contain a pigment, if necessary. As the pigment, various inorganic pigments can be used. As a specific example of the pigment, carbon (carbon, graphite) exemplified as the filler can be preferably exemplified. Carbon (carbon, graphite) is a material generally used in the battery, and is not likely to be eluted into the electrolyte. Further, the coloring effect is large, a sufficient coloring effect can be obtained by an amount added to such an extent that the adhesiveness is not inhibited, and the apparent melt viscosity of the resin to which the coloring effect is added can be increased without melting by heat. Further, the thinning of the pressure portion at the time of thermal bonding (at the time of sealing) can be prevented, and the reduction of the sealing strength can be prevented.
When a pigment is added to the adhesive film 1 for a metal terminal, the pigment is preferably contained in the polypropylene layer 11 and/or the acid-modified polypropylene layer 12, and when carbon black having a particle diameter of about 0.03 μm is used as an addition amount thereof, the amount of the pigment is about 0.05 to 0.3 parts by mass, preferably about 0.1 to 0.2 parts by mass, relative to 100 parts by mass of the resin components forming the polypropylene layer 11 and the acid-modified polypropylene layer 12, respectively. 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 by a sensor or can be visually checked. In the case where the filler and the pigment are added 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, but the filler and the pigment are preferably added separately to the polypropylene layer 11 and the acid-modified polypropylene layer 12 from the viewpoint of not inhibiting the heat-sealability of the adhesive film 1 for a metal terminal.
The adhesive film 1 for a metal terminal of the present invention can be produced by laminating at least 1 polypropylene layer and at least 1 acid-modified polypropylene layer. As a method of laminating at least 1 polypropylene layer and at least 1 acid-modified polypropylene layer, there is no particular limitation, and for example, a heat lamination method, a sandwich lamination method, an extrusion lamination method, or the like can be used.
The method of allowing the adhesive film 1 for metal terminals to be present between the metal terminal 2 and the packaging material 3 is not particularly limited, and for example, as shown in fig. 1 to 3, the metal terminal 2 may be wound with the adhesive film 1 for metal terminals in a portion where the metal terminal 2 is sandwiched by the packaging material 3. Although not shown, the adhesive film 1 for a metal terminal may be disposed on both sides of the metal terminal 2 so as to cross 2 metal terminals 2 in a portion where the metal terminal 2 is sandwiched by the packaging material 3.
[ Metal terminal 2]
The adhesive film 1 for a metal terminal of the present invention is used so as to be present between the metal terminal 2 and the packaging material 3. The metal terminal 2 (connection end) is electrically connected to an 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, and copper. For example, the metal terminal 2 connected to the positive electrode of the lithium ion battery is generally made of aluminum or the like. The metal terminal connected to the negative electrode of the lithium ion battery is generally made of copper, nickel, or the like.
From the viewpoint of improving the electrolyte resistance, the surface of the metal terminal 2 is preferably subjected to a chemical surface treatment. For example, when the metal terminal 2 is formed of aluminum, a known method for forming an acid-resistant coating such as phosphate, chromate, fluoride, or triazine thiol compound can be mentioned as a specific example of the chemical surface treatment. In the method for forming the acid-resistant coating, it is preferable to use a phosphoric acid chromate treatment composed of 3 components of a phenolic resin, a chromium (III) fluoride compound, and phosphoric acid.
The size of the metal terminal 2 may be appropriately set according to the size of the battery used. The thickness of the metal terminal 2 is preferably about 50 to 1000 μm, and more preferably about 70 to 800 μm. The length of the metal terminal 2 is preferably about 1 to 200mm, more preferably about 3 to 150 mm. The width of the metal terminal 2 is preferably about 1 to 200mm, and more preferably about 3 to 150 mm.
[ packaging Material 3]
The wrapping material 3 has a laminated structure including 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 a mode in which a base material layer 31, an adhesive layer 32, a barrier layer 33, an adhesive layer 35, and a heat-fusible resin layer 34 are sequentially laminated as an example of the cross-sectional structure of the packaging material 3. The adhesive layer 32 is a layer provided as needed for the purpose of improving adhesion between the base layer 31 and the barrier layer 33. The adhesive layer 35 is a layer provided as needed for the purpose of improving 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 side, and the heat-fusible resin layer 34 is the innermost layer side. When the battery is assembled, the battery element 4 is sealed by bringing the thermally fusible resin layers 34 located around the battery element 4 into surface contact with each other and thermally fusing the layers, thereby sealing the battery element 4. In fig. 1 to 3, the battery 10 is shown in the case of using an embossed packaging material 3 formed by embossing or the like, but the packaging material 3 may be an unshaped pouch type (pouch type). The bag type includes three-side seal, four-side seal, pillow type, and the like, and may be any type.
[ 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 an outermost layer.
The material forming the base layer 31 is not particularly limited as long as it has insulation properties. Examples of the material for forming the base layer 31 include polyester, polyamide, polyolefin, epoxy resin, acrylic resin, fluororesin, polyurethane, silicone resin, phenol resin, polyetherimide, polyimide, and a mixture or copolymer thereof.
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 material layer 31 as necessary in order to impart adhesion to the base material layer 31. That is, the adhesive layer 32 is provided between the base layer 31 and the barrier layer 33 as necessary.
The adhesive layer 32 is formed of an adhesive capable of bonding the base layer 31 and the barrier layer 33. The adhesive used to form adhesive layer 32 may be a 2-liquid curing adhesive or a 1-liquid curing adhesive. The adhesive used for forming adhesive layer 32 is also not particularly limited, and may be any of a chemical reaction type, a solvent volatilization type, a hot melt type, a hot press 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 not only enhances the strength of the packaging material for a battery, but also has a function of preventing water vapor, oxygen, light, and the like from entering the inside of the battery. Specific examples of the metal constituting the barrier layer 33 include aluminum, stainless steel, and titanium, and aluminum is preferable. The barrier layer 33 may 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, or the like, and is preferably formed of a metal foil, and more preferably an aluminum alloy foil. In the production of the battery packaging material, the barrier layer is more preferably formed of a soft aluminum alloy foil such as annealed aluminum (JIS H4160: 1994A 8021H-O, JIS H4160: 1994A 8079H-O, JIS H4000: 2014A 8021P-O, JIS H4000: 2014A 8079P-O) from the viewpoint of preventing wrinkles and pinholes from being generated in the barrier layer 33.
The thickness of the barrier layer 33 is not particularly limited as long as it can function as a barrier layer for water vapor or the like, and may be, for example, about 10 to 50 μm, preferably about 10 to 40 μm.
[ adhesive layer 35]
In the wrapping material 3, the adhesive layer 35 is a layer provided between the barrier layer 33 and the heat-fusible resin layer 34 as needed in order to firmly adhere the heat-fusible resin layer 34.
The adhesive layer 35 is formed of an adhesive capable of bonding the barrier layer 33 and the heat-fusible resin layer 34. The composition of the adhesive for forming the adhesive layer is not particularly limited, and examples thereof include resin compositions containing acid-modified polyolefins. Examples of the acid-modified polyolefin include those described in the acid-modified polypropylene layer 12. Further, polyethylene such as low density polyethylene, medium density polyethylene, high density polyethylene, and linear low density polyethylene, which is acid-modified with an unsaturated carboxylic acid or an acid anhydride thereof (for example, those exemplified in the acid-modified polypropylene layer 12), can be exemplified.
The thickness of the adhesive layer 35 is, for example, about 1 to 40 μm, preferably about 2 to 30 μm.
[ Heat-fusible resin layer 34]
The heat-fusible resin layer 34 in the packaging material 3 corresponds to an innermost layer, and is a layer for sealing the battery element by heat-fusing the heat-fusible resin layers to each other at the time of assembling the battery.
The resin component used for the heat-fusible resin layer 34 is not particularly limited as long as it can be heat-fused, and examples thereof include polyolefins and acid-modified polyolefins.
Examples of the polyolefin include the same polyolefin as exemplified for the polypropylene layer 11, and polyethylene such as low density polyethylene, medium density polyethylene, high density polyethylene, and linear low density polyethylene. The acid-modified polyolefin may be the same as the polyolefin described in the adhesive layer 35.
The thickness of the heat-fusible resin layer 34 is not particularly limited, and may be preferably about 2 to 2000 μm, more preferably about 5 to 1000 μm, and still more preferably about 10 to 500 μm.
2. Battery 10
The battery 10 of the present invention includes: a battery element 4 including at least a positive electrode, a negative electrode, and an electrolyte; a packaging material 3 for packaging the battery element 4; and metal terminals 2 electrically connected to the positive electrode and the negative electrode, respectively, and protruding outside the packaging material 3. The battery 10 of the present invention is characterized in that the adhesive film 1 for a metal terminal of the present invention is present between the metal terminal 2 and the packaging material 3.
Specifically, the battery 10 using the packaging material 3 is provided by wrapping the battery element 4 having at least the positive electrode, the negative electrode, and the electrolyte with the packaging material 3 so that the adhesive film 1 for a metal terminal of the present invention is present between the metal terminal 2 and the heat-fusible resin layer 34 in a state where the metal terminal 2 connected to each of the positive electrode and the negative electrode protrudes to the outside and that the flange portions (the edge portions 3a of the packaging material, which are the regions where the heat-fusible resin layers 34 are in contact with each other) of the packaging material can be formed around the battery element 4, and heat-sealing the heat-fusible resin layers 34 of the flange portions to seal them. When the battery element 4 is housed in the packaging material 3, the heat-fusible resin layer 34 of the packaging material 3 is used so as to be on the inner side (the surface in contact with the battery element 4).
The battery of the present invention may be any of a primary battery and a secondary battery, and is preferably a secondary battery. The type of the secondary battery is not particularly limited, and examples thereof include a lithium ion battery, a lithium ion polymer battery, a lead storage battery, a nickel hydrogen storage battery, a nickel cadmium storage battery, a nickel iron storage battery, a nickel zinc storage battery, a silver-zinc oxide storage battery, a metal air battery, a polyvalent cation battery, a capacitor (condenser), and a capacitor (capacitor). Among these secondary batteries, lithium ion batteries and lithium ion polymer batteries are preferably cited.
When the thickness of the packaging material, the metal terminal, and the adhesive film for the metal terminal constituting the battery, and the thickness of the portion where the packaging material, the adhesive film for the metal terminal, and the metal terminal are laminated are measured, the preferable thickness of the packaging material is about 10 to 65 μm, the preferable thickness of the metal terminal is about 50 to 1000 μm, the preferable thickness of the adhesive film for the metal terminal is about 30 to 80 μm, and the total of the preferable thickness of the packaging material and the preferable thickness of the adhesive film for the metal terminal is about 40 to 145 μm.
Examples
The present invention will be described in detail below with reference to examples and comparative examples. However, the present invention is not limited to the examples.
In examples and comparative examples, the melting peak temperature, the heat shrinkage rate, the seal strength, the thickness residual ratio, and the electrolyte resistance and the area ratio of island portions in the sea-island structure were evaluated as follows. The respective 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). "DSC-60 Plus" manufactured by Shimadzu corporation was used as the device. In addition, as for the measurement conditions, the temperature rise rate was set to 10 ℃/min, the temperature measurement range was set to-50 to 200 ℃, and an aluminum plate was used as a sample plate.
(measurement of Heat shrinkage percentage)
The adhesive film for metal terminals was cut into a size of 50Mm (MD) in length by 4mm (TD) in width to prepare a test piece. Next, the length M (mm) of the test piece was measured using a metal ruler. Then, the end of the test piece in the longitudinal direction was fixed to the metal net with an adhesive tape so that the test piece was suspended from the metal net. In this state, the steel sheet was left in a furnace heated to 190 ℃ for 120 seconds, taken out together with the metal mesh, and naturally cooled at room temperature (25 ℃). Next, the length n (mm) of the test piece naturally cooled to room temperature was measured using a metal ruler. The heat shrinkage of the adhesive film for metal terminals was calculated by the following equation.
Heat shrinkage (%) (length N/length M) × 100
(measurement of seal Strength)
As shown in the schematic view of fig. 7, the packaging material 3 is cut into a size of 150mm in length (md) by 60mm in width (td). The adhesive film 1 for metal terminals was cut into a size of 75mm in length (md) x 60mm in width (td). Further, a metal terminal 2 (an aluminum plate, length 60mm, width 25mm, thickness 0.1mm) was prepared. Next, as shown in the schematic diagram of fig. 8, the wrapping material 3 is folded in two in the longitudinal direction at the center P of the MD so that the heat-fusible resin layer is positioned inside. Next, the adhesive film 1 for a metal terminal and the metal terminal 2 (aluminum plate, length 60mm, width 25mm, thickness 0.1mm) were stacked and inserted between the two-folded packaging materials 3 as shown in the schematic diagram of fig. 8. At this time, the acid-modified polypropylene layer of the adhesive film 1 for metal terminals is disposed in contact with the metal terminals 2. Fig. 8b shows a cross-sectional view from the transverse direction. In this state, as shown in the schematic view of fig. 9a, heat sealing was performed from both sides of the wrapping material 3 under conditions of a sealing width of 7.0mm, a sealing temperature of 190 ℃, a surface pressure of 1.0MPa, and a sealing time of 3 seconds, to obtain a laminate. 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 of the two-dot chain line in the schematic view of fig. 9b so that the width of the heat-sealed portion S (TD of the wrapping material) was set to 15 mm. The packaging material 3 of the obtained sample and the adhesive film 1 for metal terminal were separated in the direction of 180 ° up to the position of the heat-sealed portion S. Fig. 9c is a cross-sectional view of the sample in this state as viewed in the lateral direction. Next, the seal strength (N/15mm) was measured using a tensile tester (AG-Xplus manufactured by Shimadzu corporation) under the conditions of a speed of 300mm/min, an inter-jig distance of 50mm, and a T-shaped peeling method. At this time, as shown in fig. 10, in a laminate in which the wrapping material 3/the adhesive film for metal terminal 1/the metal terminal 2/the wrapping material 3 are sequentially laminated, the wrapping material 3 and the adhesive film for metal terminal 1 are peeled off in a state where the portion of "the adhesive film for metal terminal 1/the metal terminal 2/the wrapping material 3" is sandwiched by a lower jig and the wrapping material 3 separated in the 180 ° direction is sandwiched by an upper jig, and the seal strength is measured.
(evaluation of electrolyte resistance)
The adhesive film for metal terminals was cut into a size of 15Mm (MD). times.100 mm (TD), to prepare a test piece. Next, the test piece was immersed in an electrolyte (1M LiPF) 6 The solution (ethylene carbonate, dimethyl carbonate, diethyl carbonate, volume ratio) of (1) to (1) was stored at 85 ℃ for 24 hours in a furnace. Next, the test piece was taken out, washed with water, and then visually observed. The test piece was evaluated as "a" when no delamination occurred between the layers, and as "C" when delamination occurred between the layers.
(measurement of residual Rate of thickness of adhesive film for Metal terminal)
An aluminum plate (pure aluminum type, JIS H4160-1994A 1N 30H-O) having a length of 60mm, a width of 25mm and a thickness of 100 μm and the adhesive film for a metal terminal having a length of 70mm and a width of 5mm were prepared. Next, the thickness a (μm) of the adhesive film for metal terminals was measured using a thickness meter. Next, the adhesive film for metal terminals was laminated on the central portion of the aluminum plate so that the longitudinal direction and the width direction of the aluminum plate and the adhesive film for metal terminals were aligned. Next, 2 metal plates having a length longer than that of the aluminum plate and a width of 7mm were prepared, and then, heating and pressing were performed from both upper and lower sides of the adhesive film for metal terminals under conditions of a temperature of 190 ℃, a surface pressure of 1.27MPa, and a time of 3 seconds so as to cover the entire surface of the adhesive film for metal terminals, thereby obtaining a laminate of the aluminum plate and the adhesive film for metal terminals. Next, the thickness B (μm) of the heated and pressed portion of the laminate was measured using a thickness meter. The thickness residual ratio of the adhesive film for metal terminals was calculated by the following formula. In this case, the thickness B is an average value of 3 points in total, 1 point in the center of the laminate and 2 points 10mm from both ends in the longitudinal direction of the laminate (both ends of the portion where the aluminum plate and the metal terminal adhesive film are laminated) to the center.
The adhesive film for metal terminals has a residual thickness ratio (%) (thickness B-100)/thickness A × 100
< method for measuring area ratio of island portion in island-and-island structure >
The metal terminal is embedded in thermosetting epoxy resin with an adhesive film and cured. A cross section in the desired direction (cross section along TD) was prepared using a commercially available rotary microtome (UC 6 manufactured by LEICA) and a diamond knife, and at this time, the cross section was prepared at-70 ℃ using a freezing microtome using liquid nitrogen. Along with the embedding resin, ruthenium tetroxide was used for staining overnight. Since the polypropylene swelled after dyeing, the swollen portion was trimmed off using a microtome, and a portion cut out to a thickness of about 100nm and about 1 to 2 μm was observed as follows. For the stained section, an image (magnification: 10000 times) observed using a field emission TYPE scanning electron microscope (for example, S-4800 TYPE1 manufactured by High-Technologies Corporation, measurement condition: 3kV20mA High WD6mm detector (Upper)) was obtained. Next, image processing software capable of binarizing an image (for example, a trigeminal image analysis software WinROOF (ver7.4) was used to binarize island portions and sea portions of a sea-island structure in the image and determine the ratio of the area occupied by the island portions (the total area of the island portions/the area of the measurement range of the image) — specific image processing conditions are as follows.
[ image processing conditions ]
3x3pix averaging
Binarization: automatic binarization
Removing isolated points: an object or background consisting of only 1 pixel is removed.
Removing: determining shape characteristic value or concentration characteristic value, and removing particles (0.005 μm 2 Area of (1) is recognized as noise)
< production of adhesive film for metal terminal >
(example 1)
As the polypropylene layer, an unstretched polypropylene film (CPP, total thickness 50 μm, melting peak temperature 155 ℃ C.) having a 3-layer structure in which a random polypropylene layer (6 μm)/block polypropylene layer (38 μm)/random polypropylene layer (6 μm) were sequentially laminated was prepared. Next, maleic anhydride-modified polypropylene was laminated on both surfaces of the unstretched polypropylene film by an extrusion lamination method, to produce an adhesive film for a metal terminal, in which an acid-modified polypropylene layer (25 μm)/a polypropylene layer (50 μm)/an acid-modified polypropylene layer (25 μm) were laminated in this order. The heat shrinkage of the resulting adhesive film for a metal terminal was measured and found to have a high value of 83.0%.
(example 2)
As the polypropylene layer, an unstretched polypropylene film (CPP, total thickness 60 μm, melting peak temperature 155 ℃ C.) having a 3-layer structure in which a random polypropylene layer (8 μm)/block polypropylene layer (44 μm)/random polypropylene layer (8 μm) were sequentially laminated was prepared. Then, maleic anhydride-modified polypropylene was laminated on both surfaces of the non-stretched polypropylene film by an extrusion lamination method, to produce an adhesive film for metal terminals, in which an acid-modified polypropylene layer (20 μm)/a polypropylene layer (60 μm)/an acid-modified polypropylene layer (20 μm) were sequentially laminated. The heat shrinkage of the resulting adhesive film for a metal terminal was measured and found to have a high value of 81.3%.
(example 3)
As the polypropylene layer, an unstretched polypropylene film (CPP, total thickness 50 μm, melting peak temperature 155 ℃ C.) having a 3-layer structure in which a random polypropylene layer (6 μm)/block polypropylene layer (38 μm)/random polypropylene layer (6 μm) were sequentially laminated was prepared. Next, maleic anhydride-modified polypropylene was laminated on one surface of the unstretched polypropylene film by an extrusion lamination method to produce an adhesive film for a metal terminal, in which an acid-modified polypropylene layer (16 μm)/polypropylene layer (50 μm) was laminated. The heat shrinkage of the resulting adhesive film for metal terminals was measured and found to be as high as 80.1%.
(example 4)
As the polypropylene layer, an unstretched polypropylene film (CPP, total thickness 30 μm, melting peak temperature 155 ℃ C.) having a 3-layer structure in which a random polypropylene layer (4 μm)/block polypropylene layer (22 μm)/random polypropylene layer (4 μm) were sequentially laminated was prepared. Then, maleic anhydride-modified polypropylene was laminated on one surface of the unstretched polypropylene film by an extrusion lamination method to produce an adhesive film for a metal terminal, in which an acid-modified polypropylene layer (36 μm)/polypropylene layer (30 μm) was laminated. The heat shrinkage of the resulting adhesive film for a metal terminal was measured and found to be as high as 88.1%.
(example 5)
As the polypropylene layer, an unstretched polypropylene film (CPP, total thickness 30 μm, melting peak temperature 155 ℃ C.) having a 3-layer structure in which a random polypropylene layer (4 μm)/block polypropylene layer (22 μm)/random polypropylene layer (4 μm) were sequentially laminated was prepared. Next, maleic anhydride-modified polypropylene was laminated on both surfaces of the unstretched polypropylene film by an extrusion lamination method, to produce an adhesive film for a metal terminal, in which an acid-modified polypropylene layer (18 μm)/a polypropylene layer (30 μm)/an acid-modified polypropylene layer (18 μm) were laminated in this order. The heat shrinkage of the resulting adhesive film for a metal terminal was measured and found to be as high as 88.1%.
(example 6)
As the polypropylene layer, an unstretched polypropylene film (CPP, total thickness 60 μm, melting peak temperature 159 ℃ C.) of a block polypropylene layer (60 μm) was prepared. Next, maleic anhydride-modified polypropylene was laminated on both surfaces of the unstretched polypropylene film by an extrusion lamination method, to produce an adhesive film for a metal terminal, in which an acid-modified polypropylene layer (20 μm)/a polypropylene layer (60 μm)/an acid-modified polypropylene layer (20 μm) were sequentially laminated. The heat shrinkage of the resulting adhesive film for a metal terminal was measured and found to have a high value of 81.7%.
(example 7)
As the polypropylene layer, an unstretched polypropylene film (CPP, total thickness 30 μm, melting peak temperature 155 ℃ C.) having a 3-layer structure in which a random polypropylene layer (4 μm)/block polypropylene layer (22 μm)/random polypropylene layer (4 μm) were sequentially laminated was prepared. Next, maleic anhydride-modified polypropylene was laminated on both sides of the unstretched polypropylene film by an extrusion lamination method, to produce an adhesive film for a metal terminal, in which an acid-modified polypropylene layer (16 μm)/a polypropylene layer (30 μm)/acid-modified polypropylene (16 μm) was laminated. The heat shrinkage of the resulting adhesive film for a metal terminal was measured and found to be as high as 88.7%.
Comparative example 1
As the polypropylene layer, an unstretched polypropylene film (CPP, total thickness 30 μm, melting peak temperature 155 ℃ C.) having a 3-layer structure in which a random polypropylene layer (4 μm)/block polypropylene layer (22 μm)/random polypropylene layer (4 μm) were sequentially laminated was prepared. Then, maleic anhydride-modified polypropylene was laminated on both surfaces of the non-stretched polypropylene film by an extrusion lamination method, to produce an adhesive film for metal terminals, in which an acid-modified polypropylene layer (35 μm)/a polypropylene layer (30 μm)/an acid-modified polypropylene layer (35 μm) were sequentially laminated.
Comparative example 2
As the polypropylene layer, an unstretched polypropylene film (CPP, total thickness 25 μm, melting peak temperature 155 ℃ C.) having a 3-layer structure in which a random polypropylene layer (3 μm)/block polypropylene layer (3 μm)/random polypropylene layer (19 μm) were sequentially laminated was prepared. Then, maleic anhydride-modified polypropylene was laminated on one surface of the unstretched polypropylene film by an extrusion lamination method to produce an adhesive film for a metal terminal, in which an acid-modified polypropylene layer (41 μm)/polypropylene layer (25 μm) was laminated.
Comparative example 3
As the polypropylene layer, a stretched polypropylene film (OPP, homopolypropylene, thickness 50 μm, melting peak temperature 165 ℃ C.) was prepared. Then, maleic anhydride-modified polypropylene was laminated on both surfaces of the stretched polypropylene film by an extrusion lamination method, to produce an adhesive film for a metal terminal, in which an acid-modified polypropylene layer (25 μm)/a polypropylene layer (50 μm)/an acid-modified polypropylene layer (25 μm) were laminated in this order.
Ruthenium tetroxide (RuO) was used for the cross-section of the unstretched polypropylene layers used in examples 1 to 5 and comparative examples 1 and 2 4 ) After dyeing, when a scanning electron micrograph was observed, a sea-island structure was observed. On the other hand, when the same observation was made with respect to the stretched polypropylene layer used in comparative example 3, no sea-island structure was observed.
(production of packaging Material)
An aluminum foil (40 μm thick) was prepared by subjecting both surfaces to chemical surface treatment (phosphoric acid chromate treatment) using a chemical surface treatment solution composed of a phenol resin, a chromium (trivalent) fluoride compound, and a phosphoric acid 3 component. Then, one surface of the aluminum foil and a biaxially stretched nylon film (thickness: 25 μm) were laminated with a urethane adhesive interposed therebetween. Next, the other side of the aluminum foil and the non-stretched polypropylene film (thickness 30 μm) were laminated with an acid-modified polypropylene resin (thickness 15 μm, polypropylene graft-modified with an unsaturated carboxylic acid) in an interlayer manner, and heated with hot air to a temperature equal to or higher than the softening point of the acid-modified polypropylene resin, to produce a packaging material in which a biaxially stretched nylon film (25 μm)/aluminum foil (thickness 40 μm)/acid-modified polypropylene resin (thickness 15 μm)/non-stretched polypropylene film (15 μm) were laminated in this order. The obtained packaging material was used to measure the seal strength as described above.
[ Table 1]
Figure BDA0002251429430000291
In table 1, PP means polypropylene and PPa means acid-modified polypropylene.
As shown in table 1, the adhesive films for metal terminals of examples 1 to 5, which were composed of a laminate comprising at least 1 polypropylene layer and at least 1 acid-modified polypropylene layer, the acid-modified polypropylene layer constituted at least the surface layer on at least one surface side of the adhesive film for metal terminals, and the sea-island structure was observed in a scanning electron micrograph of the cross section of the polypropylene layer, and the total thickness of the polypropylene layers was in the range of 0.7 to 3.5 when the total thickness of the acid-modified polypropylene layers was 1, were high in both sealing strength (i.e., adhesiveness) with the packaging material and the metal terminal, and were excellent in both electrolyte resistance. On the other hand, the adhesive films for metal terminals of comparative examples 1 and 2, which have the sea-island structure described above in the polypropylene layer, have poor adhesion to the packaging material and the metal terminal when the total thickness of the acid-denatured polypropylene layer is 1 and the total thickness of the polypropylene layer is out of the range of 0.7 to 3.5. The adhesive film for a metal terminal of comparative example 3, which does not have the sea-island structure in the polypropylene layer, satisfies the above range, and is inferior in adhesion to a packaging material and a metal terminal and in electrolyte solution resistance. In examples 1 to 7, the sea-island structure of the polypropylene layer had a value as large as 28.0% or more when the area of the island portion was measured by binarization, and the acid-modified polypropylene layer also had a value as large as 24.5% or more. On the other hand, in comparative example 3, regarding the sea-island structure of the polypropylene layer, when the area of the island portion was measured by binarization, the ratio of the area was very low as 1.57%, and it was confirmed that the polypropylene layer had substantially no sea-island structure.
Description of the symbols
1 adhesive film for metal terminal
2 Metal terminal
3 packaging material
3a edge portion of packaging material
4 cell element
10 cell
11 Polypropylene layer
12 acid modified polypropylene layer
31 base material layer
32 adhesive layer
33 barrier layer
34 Heat-fusible resin layer
35 adhesive layer
P center
S parts of heat seal

Claims (28)

1. An adhesive film for a metal terminal, characterized in that:
which is an adhesive film for a metal terminal, which is present between a metal terminal electrically connected to an electrode of a battery element and a packaging material for packaging the battery element,
the adhesive film for metal terminals comprises a laminate comprising at least 1 polypropylene layer and at least 1 acid-modified polypropylene layer,
the acid-modified polypropylene layer constitutes a surface layer on at least one surface side of the adhesive film for a metal terminal,
the sea-island structure was observed when the cross section of the polypropylene layer was observed using an electron micrograph,
in the sea-island structure of the polypropylene layer, the area ratio of the island part is 10% to 50%,
when the total thickness of the acid-modified polypropylene layers is 1, the total thickness of the polypropylene layers is in the range of 0.7 to 3.5.
2. The adhesive film for a metal terminal according to claim 1, wherein:
the polypropylene layer is composed of unstretched polypropylene.
3. The adhesive film for a metal terminal according to claim 1 or 2, wherein:
when the adhesive film for a metal terminal is measured by a differential scanning calorimeter, a melting peak is observed in a range of 150 ℃ to 165 ℃.
4. The adhesive film for a metal terminal according to claim 1 or 2, wherein:
the adhesive film for a metal terminal has a thickness residual ratio of 50% or more, as measured by the following measurement method:
preparing an aluminum plate having a thickness of 100 μm and the adhesive film for the metal terminal;
measuring the thickness a (μm) of the adhesive film for a metal terminal;
stacking the adhesive film for metal terminal on a central portion of the aluminum plate so that a longitudinal direction and a width direction of the aluminum plate and the adhesive film for metal terminal are aligned;
preparing 2 metal plates having a length longer than the aluminum plate and a width of 7mm, and heating and pressing the metal plates from above and below the aluminum plate and the adhesive film for a metal terminal under conditions of a temperature of 190 ℃, a surface pressure of 1.27MPa, and a time of 3 seconds so as to cover the entire surface of the adhesive film for a metal terminal, thereby obtaining a laminate of the aluminum plate and the adhesive film for a metal terminal;
measuring the thickness B (μm) of the heated and pressed portion of the laminate;
the remaining thickness ratio of the adhesive film for metal terminals was calculated by the following equation,
the adhesive film for a metal terminal has a residual thickness ratio (%) (thickness B-100)/thickness a × 100.
5. The adhesive film for a metal terminal according to claim 1 or 2, wherein:
the adhesive film for a metal terminal has a thermal shrinkage ratio of 70 to 90% in the flow direction.
6. The adhesive film for a metal terminal according to claim 1 or 2, wherein:
the packaging material is composed of a laminate comprising at least a base material layer, a barrier layer and a heat-fusible resin layer in this order,
the adhesive film for metal terminals is present between the thermally fusible resin layer and the metal terminals.
7. An adhesive film for a metal terminal, characterized in that:
which is an adhesive film for a metal terminal, which is present between a metal terminal electrically connected to an electrode of a battery element and a packaging material for packaging the battery element,
the adhesive film for metal terminals comprises a laminate comprising at least 1 polypropylene layer and at least 1 acid-modified polypropylene layer,
the acid-modified polypropylene layer constitutes a surface layer on at least one surface side of the adhesive film for a metal terminal,
the sea-island structure was observed when the cross section of the polypropylene layer was observed using an electron micrograph,
wherein the total thickness of the polypropylene layers is in the range of 0.7 to 3.5, when the total thickness of the acid-modified polypropylene layers is 1,
when the adhesive film for a metal terminal is measured by a differential scanning calorimeter, a melting peak is observed in a range of 150 ℃ to 165 ℃,
the polypropylene layer contains a block polypropylene,
the block polypropylene contains 30 to 80 mass% of propylene.
8. The adhesive film for a metal terminal according to claim 7, wherein:
the laminated structure of the adhesive film for the metal terminal is a 3-layer structure of acid modified polypropylene layer/acid modified polypropylene layer,
the polypropylene layer accounts for 40-80% of the thickness of the adhesive film for metal terminals.
9. The adhesive film for a metal terminal according to claim 7 or 8, wherein:
the polypropylene layer is composed of unstretched polypropylene.
10. The adhesive film for a metal terminal according to claim 7 or 8, wherein:
the polypropylene layer has a laminated structure in which a layer made of atactic polypropylene, a layer made of block polypropylene and a layer made of atactic polypropylene are laminated in this order.
11. The adhesive film for a metal terminal according to claim 7 or 8, wherein:
the adhesive film for a metal terminal has a thermal shrinkage rate of 70 to 90% in the flow direction.
12. The adhesive film for a metal terminal according to claim 7 or 8, wherein:
the packaging material is composed of a laminate comprising at least a base material layer, a barrier layer and a heat-fusible resin layer in this order,
the adhesive film for metal terminals is present between the thermally fusible resin layer and the metal terminals.
13. An adhesive film for a metal terminal, characterized in that:
which is an adhesive film for a metal terminal, which is present between a metal terminal electrically connected to an electrode of a battery element and a packaging material for packaging the battery element,
the adhesive film for metal terminals comprises a laminate comprising at least 1 polypropylene layer and at least 1 acid-modified polypropylene layer,
the acid-modified polypropylene layer constitutes a surface layer on at least one surface side of the adhesive film for a metal terminal,
the sea-island structure was observed when the cross section of the polypropylene layer was observed using an electron micrograph,
wherein the total thickness of the polypropylene layers is in the range of 0.7 to 3.5, when the total thickness of the acid-modified polypropylene layers is 1,
the polypropylene layer contains a block polypropylene,
the block polypropylene contains 30 to 80 mass% of propylene,
the adhesive film for a metal terminal has a thickness residual ratio of 50% or more, as measured by the following measurement method:
preparing an aluminum plate having a thickness of 100 μm and the adhesive film for the metal terminal;
measuring the thickness a (μm) of the adhesive film for a metal terminal;
stacking the adhesive film for metal terminal on a central portion of the aluminum plate so that a longitudinal direction and a width direction of the aluminum plate and the adhesive film for metal terminal are aligned;
preparing 2 metal plates having a length longer than the aluminum plate and a width of 7mm, and heating and pressing the metal plates from above and below the aluminum plate and the adhesive film for a metal terminal under conditions of a temperature of 190 ℃, a surface pressure of 1.27MPa, and a time of 3 seconds so as to cover the entire surface of the adhesive film for a metal terminal, thereby obtaining a laminate of the aluminum plate and the adhesive film for a metal terminal;
measuring the thickness B (μm) of the heated and pressed portion of the laminate;
the thickness residual ratio of the adhesive film for metal terminals was calculated by the following equation,
the adhesive film for a metal terminal has a residual thickness ratio (%) (thickness B-100)/thickness a × 100.
14. The adhesive film for a metal terminal according to claim 13, wherein:
the laminated structure of the adhesive film for the metal terminal is a 3-layer structure of acid modified polypropylene layer/acid modified polypropylene layer,
the polypropylene layer accounts for 40-80% of the thickness of the adhesive film for the metal terminal.
15. The adhesive film for a metal terminal according to claim 13 or 14, wherein:
the polypropylene layer is composed of unstretched polypropylene.
16. The adhesive film for a metal terminal according to claim 13 or 14, wherein:
the polypropylene layer has a laminated structure in which a layer made of atactic polypropylene, a layer made of block polypropylene and a layer made of atactic polypropylene are laminated in this order.
17. The adhesive film for a metal terminal according to claim 13 or 14, wherein:
when the adhesive film for a metal terminal is measured by a differential scanning calorimeter, a melting peak is observed in a range of 150 ℃ to 165 ℃.
18. The adhesive film for a metal terminal according to claim 13 or 14, wherein:
the adhesive film for a metal terminal has a thermal shrinkage rate of 70 to 90% in the flow direction.
19. The adhesive film for a metal terminal according to claim 13 or 14, wherein:
the packaging material is composed of a laminate comprising at least a base material layer, a barrier layer and a heat-fusible resin layer in this order,
the adhesive film for metal terminals is present between the thermally fusible resin layer and the metal terminals.
20. An adhesive film for a metal terminal, characterized in that:
which is an adhesive film for a metal terminal, which is present between a metal terminal electrically connected to an electrode of a battery element and a packaging material for packaging the battery element,
the adhesive film for a metal terminal is composed of a laminate comprising at least 1 polypropylene layer and at least 1 acid-modified polypropylene layer,
the acid-modified polypropylene layer constitutes a surface layer on at least one surface side of the adhesive film for a metal terminal,
the sea-island structure was observed when the cross section of the polypropylene layer was observed using an electron micrograph,
wherein the total thickness of the polypropylene layers is in the range of 0.7 to 3.5, when the total thickness of the acid-modified polypropylene layers is 1,
the adhesive film for a metal terminal has a thermal shrinkage ratio of 70 to 90% in the flow direction,
the polypropylene layer contains a block polypropylene,
the block polypropylene contains 30 to 80 mass% of propylene.
21. The adhesive film for a metal terminal according to claim 20, wherein:
the laminated structure of the adhesive film for the metal terminal is a 3-layer structure of acid modified polypropylene layer/acid modified polypropylene layer,
the polypropylene layer accounts for 40-80% of the thickness of the adhesive film for metal terminals.
22. The adhesive film for a metal terminal according to claim 20 or 21, wherein:
the polypropylene layer is composed of unstretched polypropylene.
23. The adhesive film for a metal terminal according to claim 20 or 21, wherein:
the polypropylene layer has a laminated structure in which a layer made of atactic polypropylene, a layer made of block polypropylene and a layer made of atactic polypropylene are laminated in this order.
24. The adhesive film for a metal terminal according to claim 20 or 21, wherein:
when the adhesive film for a metal terminal is measured by a differential scanning calorimeter, a melting peak is observed in a range of 150 ℃ to 165 ℃.
25. The adhesive film for a metal terminal according to claim 20 or 21, wherein:
the packaging material is composed of a laminate comprising at least a base material layer, a barrier layer and a heat-fusible resin layer in this order,
the adhesive film for the metal terminal is present between the heat-fusible resin layer and the metal terminal.
26. An adhesive film for a metal terminal, characterized in that:
which is an adhesive film for a metal terminal, which is present between a metal terminal electrically connected to an electrode of a battery element and a packaging material for packaging the battery element,
the adhesive film for metal terminals comprises a laminate comprising at least 1 polypropylene layer and at least 1 acid-modified polypropylene layer,
the acid-modified polypropylene layer constitutes a surface layer on at least one surface side of the adhesive film for a metal terminal,
the sea-island structure was observed when the cross section of the polypropylene layer was observed using an electron micrograph,
wherein the total thickness of the polypropylene layers is in the range of 0.7 to 3.5, when the total thickness of the acid-modified polypropylene layers is 1,
when the adhesive film for a metal terminal is measured by a differential scanning calorimeter, a melting peak is observed in a range of 150 ℃ to 165 ℃,
the laminated structure of the adhesive film for the metal terminal is a 3-layer structure of acid modified polypropylene layer/acid modified polypropylene layer,
the ratio of the thickness of the polypropylene layer to the thickness of the adhesive film for a metal terminal is 40 to 80%,
the polypropylene layer contains a block of polypropylene,
the proportion of propylene contained in the block polypropylene is 30 to 80 mass%.
27. An adhesive film for a metal terminal, characterized in that:
which is an adhesive film for a metal terminal, which is present between a metal terminal electrically connected to an electrode of a battery element and a packaging material for packaging the battery element,
the adhesive film for a metal terminal is composed of a laminate comprising at least 1 polypropylene layer and at least 1 acid-modified polypropylene layer,
the acid-modified polypropylene layer constitutes a surface layer on at least one surface side of the adhesive film for a metal terminal,
the sea-island structure was observed when the cross section of the polypropylene layer was observed using an electron micrograph,
wherein the total thickness of the polypropylene layers is in the range of 0.7 to 3.5, when the total thickness of the acid-modified polypropylene layers is 1,
the laminated structure of the adhesive film for the metal terminal is a 3-layer structure of acid modified polypropylene layer/acid modified polypropylene layer,
the ratio of the thickness of the polypropylene layer to the thickness of the adhesive film for a metal terminal is 40 to 80%,
the polypropylene layer contains a block polypropylene,
the block polypropylene contains 30 to 80 mass% of propylene,
the adhesive film for a metal terminal has a thickness residual ratio of 50% or more, as measured by the following measurement method:
preparing an aluminum plate having a thickness of 100 μm and the adhesive film for the metal terminal;
measuring the thickness a (μm) of the adhesive film for a metal terminal;
stacking the adhesive film for metal terminals on a central portion of the aluminum plate so that a longitudinal direction and a width direction of the aluminum plate and the adhesive film for metal terminals are aligned;
preparing 2 metal plates having a length longer than the aluminum plate and a width of 7mm, and heating and pressing the metal plates from above and below the aluminum plate and the adhesive film for a metal terminal under conditions of a temperature of 190 ℃, a surface pressure of 1.27MPa, and a time of 3 seconds so as to cover the entire surface of the adhesive film for a metal terminal, thereby obtaining a laminate of the aluminum plate and the adhesive film for a metal terminal;
measuring the thickness B (μm) of the heated and pressed portion of the laminate;
the thickness residual ratio of the adhesive film for metal terminals was calculated by the following equation,
the adhesive film for a metal terminal has a residual thickness ratio (%) (thickness B-100)/thickness a × 100.
28. An adhesive film for a metal terminal, characterized in that:
which is an adhesive film for a metal terminal, which is present between a metal terminal electrically connected to an electrode of a battery element and a packaging material for packaging the battery element,
the adhesive film for metal terminals comprises a laminate comprising at least 1 polypropylene layer and at least 1 acid-modified polypropylene layer,
the acid-modified polypropylene layer constitutes a surface layer on at least one surface side of the adhesive film for a metal terminal,
the sea-island structure was observed when the cross section of the polypropylene layer was observed using an electron micrograph,
wherein the total thickness of the polypropylene layers is in the range of 0.7 to 3.5, when the total thickness of the acid-modified polypropylene layers is 1,
the adhesive film for a metal terminal has a thermal shrinkage rate of 70 to 90% in the flow direction,
the laminated structure of the adhesive film for the metal terminal is a 3-layer structure of acid modified polypropylene layer/acid modified polypropylene layer,
the ratio of the thickness of the polypropylene layer to the thickness of the adhesive film for a metal terminal is 40 to 80%,
the polypropylene layer contains a block polypropylene,
the block polypropylene contains 30 to 80 mass% of propylene.
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