Insulating resin film for lead and lead with insulating resin film

Abstract

To provide an insulating resin film for a lead which is excellent in dimensional stability at the time of thermocompression bonding to a conductor.SOLUTION: An insulating resin film for a lead, comprising a first layer having a first surface and a second surface located opposite to the first surface, and a second layer laminated on the second surface of the first layer, wherein a first loss factor / a second loss factor, which is a ratio of a first loss factor at a first temperature obtained by adding 10 °C to a melting peak temperature of the first layer to a second loss factor at a second temperature of 50 °C, is 1.5 or more and 7.0 or less.SELECTED DRAWING: Figure 4A

Description

[Technical Field]

[0001] The present disclosure relates to an insulating resin film for a lead and a lead with an insulating resin film. [Background technology]

[0002] Patent Document 1 discloses an electricity storage device that includes at least an electricity storage device element having a positive electrode, a negative electrode, and an electrolyte, an exterior material for an electricity storage device that seals the electricity storage device element, and metal terminals that are electrically connected to the positive electrode and the negative electrode, respectively, and protrude outside the exterior material for an electricity storage device, wherein an adhesive film for metal terminals is interposed between the metal terminals and the exterior material for an electricity storage device. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2021 / 201213 Summary of the Invention [Problem to be solved by the invention]

[0004] Laminated batteries have been used in which a laminate including a positive electrode, a separator, and a negative electrode is sealed in an exterior body together with an electrolyte solution. In laminated batteries, leads with insulating resin films are arranged so as to cross the sealing portion of the exterior body in order to connect the positive electrode and the negative electrode to an external device.

[0005] The lead with insulating resin film has a plate-shaped conductor and insulating resin films disposed on the top and bottom surfaces of the conductor. The insulating resin films are thermocompression bonded to the outer casing, thereby bonding and sealing the conductor and the outer casing.

[0006] However, when conventionally used insulating resin films are thermocompressed to a conductor to form a lead with an insulating resin film, at least a portion of the insulating resin film may thermally shrink or melt, resulting in a large change in dimension.

[0007] If the insulating resin film undergoes dimensional changes when it is thermocompressed to the conductor, wrinkles may form on the surface of the insulating resin film, causing problems with appearance or problems with adhesion to the outer casing.

[0008] An object of the present disclosure is to provide an insulating resin film for leads that has excellent dimensional stability when thermocompression bonded to a conductor. [Means for solving the problem]

[0009] The insulating resin film for leads of the present disclosure includes a first layer having a first surface and a second surface located opposite the first surface, and a second layer laminated on the second surface of the first layer, wherein the first loss factor / second loss factor, which is the ratio of a first loss factor at a first temperature obtained by adding 10°C to a peak melting temperature of the first layer, to a second loss factor at a second temperature of 50°C, is 1.5 or more and 7.0 or less. [Effects of the Invention]

[0010] According to the present disclosure, it is possible to provide an insulating resin film for leads that has excellent dimensional stability when thermocompression bonded to a conductor. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is an explanatory diagram of a battery to which a lead with an insulating resin film according to one embodiment of the present disclosure is applied. [Figure 2] FIG. 2 is a top view of a lead with an insulating resin film according to one embodiment of the present disclosure. [Figure 3] FIG. 3 is a cross-sectional view taken along line AA in FIG. [Figure 4A] FIG. 4A is a schematic cross-sectional view of an insulating resin film for leads according to one embodiment of the present disclosure. [Figure 4B] FIG. 4B is a schematic cross-sectional view of an insulating resin film for leads according to another embodiment of the present disclosure. [Figure 5A] FIG. 5A is a cross-sectional view taken along line BB in FIG. 2, and is an explanatory diagram for evaluation of filling ability. [Figure 5B] FIG. 5B is a cross-sectional view taken along line BB in FIG. 2, and is an explanatory diagram for evaluation of filling ability. [Figure 6] FIG. 6 is a table showing the evaluation results of the experimental examples. DETAILED DESCRIPTION OF THE INVENTION

[0012] The embodiments for carrying out the invention are described below.

[0013] [Description of the embodiments of the present disclosure] First, embodiments of the present disclosure will be listed and described. In the following description, the same or corresponding elements will be denoted by the same reference numerals, and the same description will not be repeated.

[0014] (1) An insulating resin film for leads according to one embodiment of the present disclosure includes a first layer having a first surface and a second surface opposite to the first surface, and a second layer laminated on the second surface of the first layer, wherein the first layer has a first loss factor at a first temperature obtained by adding 10°C to a peak melting temperature, and a second loss factor at a second temperature of 50°C, where the first loss factor / second loss factor is a ratio of 1.5 to 7.0.

[0015] In this specification, an insulating resin film for a lead may be referred to as an "insulating resin film," and a lead with an insulating resin film may be referred to as a "lead."

[0016] By setting the first loss factor / second loss factor of the first layer to 7.0 or less, dimensional change in the first layer can be prevented when the insulating resin film is thermocompression bonded to a conductor, resulting in an insulating resin film with excellent dimensional stability. This is because, by setting the first loss factor / second loss factor of the first layer to 7.0 or less, the ratio of the loss modulus, i.e., viscosity, decreases, making the film closer to an elastic body, thereby reducing dimensional change when thermocompression bonded to a conductor.

[0017] By setting the first loss coefficient / second loss coefficient of the first layer to 1.5 or more, the first layer deforms appropriately to fit the shape of the conductor when the insulating resin film is thermocompression bonded to the conductor, thereby reducing the gap between the insulating resin film and the conductor.

[0018] (2) In the above (1), the first loss factor may be 0.15 or more and 0.9 or less.

[0019] By setting the first loss factor to 0.9 or less, dimensional changes in the first layer can be prevented when the insulating resin film is thermocompression bonded to a conductor, and an insulating resin film with excellent dimensional stability can be obtained.

[0020] By setting the first loss factor to 0.15 or more, the first layer deforms appropriately to fit the shape of the conductor when the insulating resin film is thermocompression bonded to the conductor, thereby reducing the gap between the insulating resin film and the conductor.

[0021] (3) In the above (1) or (2), the first layer may contain a polyolefin resin.

[0022] Because polyolefin resins have excellent cross-linking properties, the loss factor of the first layer can be easily controlled by including a polyolefin resin in the first layer. Furthermore, the glass transition point and melting point of polyolefin resins are sufficiently higher than the operating temperatures of various batteries, such as lithium-ion secondary batteries, to which a lead having an insulating resin film according to an embodiment of the present disclosure is expected to be applied. Therefore, when the first layer includes a polyolefin resin, adhesion between the exterior body and the lead can be improved in a battery using a lead having an insulating resin film according to an embodiment of the present disclosure. Furthermore, since a layer containing a polyolefin resin is often disposed on the surface of the exterior body that comes into contact with the lead, the inclusion of a polyolefin resin in the first layer also improves adhesion between the exterior body and the lead having an insulating resin film according to an embodiment of the present disclosure.

[0023] (4) In any of the above (1) to (3), the first layer may contain a crosslinking agent.

[0024] The inclusion of a crosslinking agent in the first layer allows the first layer to be crosslinked, and the degree of crosslinking in the first layer can be easily controlled by the blending ratio of the crosslinking agent. Therefore, the inclusion of a crosslinking agent in the first layer also allows the loss factor of the first layer to be controlled.

[0025] (5) In the above (4), the content of the crosslinking agent in the first layer based on the mass may be equal to or less than the content of the crosslinking agent in the second layer based on the mass.

[0026] By setting the content ratio of the cross-linking agent by mass of the first layer equal to or less than the content ratio of the cross-linking agent by mass of the second layer, the degree of cross-linking of the first layer can be equal to or less than that of the second layer. By setting the degree of cross-linking of the first layer equal to or less than that of the second layer, the first layer can be appropriately deformed when the insulating resin film is thermocompression bonded to the conductor, and the gap between the conductor and the insulating resin film can be reduced.

[0027] (6) In the above (4) or (5), the first layer may have a higher content of the crosslinking agent on a mass basis on the second surface than on the first surface.

[0028] In the first layer, the content of the cross-linking agent in the second surface is greater than that in the first surface, so that the first surface that comes into contact with the conductor can be appropriately deformed when the insulating resin film is thermocompression bonded to the conductor, thereby reducing the gap between the conductor and the insulating resin film.

[0029] Furthermore, when the insulating resin film is thermocompression bonded to the conductor, the second surface is less likely to deform than the first surface, and therefore the dimensional stability of the insulating resin film can be improved.

[0030] (7) A lead with an insulating resin film according to one embodiment of the present disclosure has a plate-shaped conductor having rectangular upper and lower surfaces, and an insulating resin film including a first insulating resin film arranged on the upper surface of the conductor and a second insulating resin film arranged on the lower surface of the conductor, wherein the insulating resin film is an insulating resin film for a lead according to any one of (1) to (6), and is laminated in the order of the conductor, the first layer, and the second layer.

[0031] A lead with an insulating resin film according to one aspect of the present disclosure has an insulating resin film according to one aspect of the present disclosure thermocompression bonded to a conductor.

[0032] The insulating resin film according to one embodiment of the present disclosure has excellent dimensional stability when thermocompression-bonded to a conductor. Therefore, the lead with an insulating resin film according to one embodiment of the present disclosure can have an insulating resin film with desired dimensions. Furthermore, the gap between the conductor and the insulating resin film can be sufficiently reduced.

[0033] According to one aspect of the present disclosure, a lead with an insulating resin film can be prevented from causing wrinkles or the like on the surface of the insulating resin film, and therefore, when the outer casing is thermocompressed, adhesion to the outer casing can be improved.

[0034] [Details of the embodiments of the present disclosure] Specific examples of an insulating resin film for leads and a lead with an insulating resin film according to one embodiment of the present disclosure (hereinafter referred to as "the present embodiment") will be described below with reference to the drawings. Note that the present invention is not limited to these examples, but is defined by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0035] In this specification, the names of components and the names of characteristic values ​​may be described by adding "first," "second," etc., such as "first layer," "second layer," "first insulating resin film," "second insulating resin film," "first loss factor," and "second loss factor." The terms "first," "second," etc., are used merely to distinguish between components and characteristic values ​​and to prevent confusion during description, and do not represent arrangement, priority, etc. Therefore, when there is no particular risk of confusion or when referring to components collectively, they may be simply referred to as "layer," "insulating resin film," and "loss factor." [Insulating resin film for leads] Fig. 1 is an explanatory diagram of a configuration example in which a lead with an insulating resin film having an insulating resin film for a lead of this embodiment is applied to a battery. Fig. 2 is a top view of a lead with an insulating resin film having an insulating resin film of this embodiment. Fig. 3 is a schematic cross-sectional view taken along line AA in Fig. 1.

[0036] Fig. 4A is a schematic cross-sectional view of an insulating resin film according to one embodiment of the present disclosure, and Fig. 4B is a schematic cross-sectional view of an insulating resin film according to another embodiment of the present disclosure.

[0037] First, a lead with an insulating resin film provided with the insulating resin film of this embodiment and a battery using the lead will be described. (1) About batteries As shown in FIG. 1, a battery 10 can have an outer casing 11, an electrode laminate 12 in which a positive electrode, a separator, and a negative electrode are laminated and impregnated with an electrolyte solution, and a lead 13 connected to the electrode laminate 12. (exterior body) The exterior body 11 is a container that houses and seals the electrode stack 12 and the electrolyte solution. The exterior body 11 can have at least one resin layer on the surface facing the electrode stack 12 so that thermocompression bonding can be performed.

[0038] For example, as shown in FIG. 3, the exterior body 11 can have a structure in which a first resin layer 111, a metal layer 112, and a second resin layer 113 are laminated.

[0039] 1, a seal portion 110 is formed on the periphery of the exterior body 11, and the electrode stack 12 and the electrolyte are sealed by the seal portion 110. The area surrounded by the seal portion 110 is the area sealed by the exterior body 11. (2) Leads with insulating resin film 1, 2, and 3, the lead 13 with an insulating resin film of this embodiment can have a plate-shaped conductor 14 having a rectangular upper surface 141 and a rectangular lower surface 142, and an insulating resin film 15 for the lead. The insulating resin film 15 includes a first insulating resin film 151 disposed on the upper surface 141 of the conductor 14, and a second insulating resin film 152 disposed on the lower surface 142 of the conductor 14.

[0040] The conductor 14 and insulating resin film 15, which are components of the lead 13, will be described. (2-1) Conductor Conductor 14 is a member for connecting electrode stack 12 disposed within exterior housing 11 with devices disposed outside exterior housing 11. Conductor 14 may have a plate-like shape, and upper surface 141 and lower surface 142 (see FIG. 3) may have a rectangular shape. As shown in FIG. 2, upper surface 141 of conductor 14 has two opposing sides, side 21 and side 22, and sides 23 and 24 that intersect with sides 21 and 22. However, the rectangular shape does not mean a strict geometric shape, and conductor 14 may have a shape with rounded corners.

[0041] In the following description, when the conductor 14 is viewed from above along the vertical direction of the upper surface 141, the axis along the two selected opposing sides, sides 21 and 22, is defined as the X-axis, and the axis perpendicular to the X-axis is defined as the Y-axis.

[0042] There are no particular limitations on the material of the conductor 14, and it is possible to use, for example, various materials used for lead conductors. Examples of materials for the conductor 14 include metal materials such as aluminum, titanium, nickel, copper, aluminum alloys, titanium alloys, nickel alloys, and copper alloys, as well as materials obtained by plating these metal materials with nickel, gold, or the like. (2-2) Insulating resin film 3, the insulating resin film 15 can include a first insulating resin film 151 disposed on the upper surface 141 of the conductor 14 and a second insulating resin film 152 disposed on the lower surface 142 of the conductor 14. As shown in FIGS. 2 and 3, on the upper surface 141 and the lower surface 142, the first insulating resin film 151 and the second insulating resin film 152 are disposed so as to expose, but not cover, both end portions of the conductor 14 along the Y axis, i.e., both end portions including sides 21 and 22. Therefore, on the upper surface 141 and the lower surface 142 of the conductor 14, the first insulating resin film 151 and the second insulating resin film 152 are disposed so as to cover, across, the conductor 14 along the X axis, the intermediate portion of the conductor 14 other than both end portions along the Y axis.

[0043] The upper surface 141 and the lower surface 142 of the conductor 14 refer to the surfaces that face the exterior body 11 of the battery 10 when the battery 10 is manufactured.

[0044] 2, the two ends of the conductor 14 along the Y-axis refer to the first end region 25 including the side 21 and the second end region 26 including the side 22. The intermediate portion is the portion located between the first end region 25 and the second end region 26.

[0045] The first end region 25 is a portion that is exposed to the outside of the exterior body 11 when the lead 13 is applied to a battery, for example, and its size can be selected so that it can be connected to external devices. The second end region 26 is a portion that is located inside the exterior body 11 when the lead 13 is applied to a battery, for example, and is connected to the electrode laminate 12, and its size can be selected so that it can be connected to the electrode laminate 12. The first end region 25 and the second end region 26 may have the same size, such as area, or may be different.

[0046] Therefore, the length L14 of the conductor 14 along the Y axis is longer than the length L15 of the insulating resin film 15. Also, the length W15 of the insulating resin film 15 is longer than the length W14 of the conductor 14 along the X axis.

[0047] 2, the first insulating resin film 151 and the second insulating resin film 152 are arranged so as to overlap and protrude from both ends of the conductor 14 along the X-axis. In the portions protruding from the conductor 14, the first insulating resin film 151 and the second insulating resin film 152 are in direct contact with each other and are bonded together.

[0048] The lead 13 is in close contact with the sealing portion 110 (see FIG. 1) at the insulating resin film 15 portion. (3) Insulating resin film for leads The insulating resin film 15 is placed on the portion of the lead 13 that contacts the exterior body 11 and is bonded to the conductor 14 by thermocompression bonding to form the lead 13 .

[0049] Conventional insulating resin films 15 may shrink or melt and undergo dimensional changes when heated during thermocompression bonding. If a large dimensional change occurs in insulating resin film 15 during thermocompression bonding to conductor 14, wrinkles may form on the surface of insulating resin film 15, causing problems with appearance and problems with adhesion to exterior body 11. For this reason, there has been a demand for insulating resin film 15 with excellent dimensional stability that can reduce dimensional changes during thermocompression bonding to conductor 14.

[0050] In this specification, an insulating resin film with excellent dimensional stability means an insulating resin film that does not wrinkle when thermocompressed to a conductor and can reduce the gap between the conductor and the insulating resin film. Specifically, for example, this means an insulating resin film that is rated A in terms of shrinkability and filling ability, as explained in the experimental examples.

[0051] As shown in Figures 4A and 4B, the insulating resin film 15 of this embodiment can have a structure in which multiple layers containing resin are laminated. For example, as shown in Figure 4A, the insulating resin film 15 can have a structure in which a first layer 31 and a second layer 32 are laminated. Also, as shown in Figure 4B, the insulating resin film 15 can have a third layer 33 in addition to the first layer 31 and the second layer 32. The insulating resin film 15 can also have a structure in which four or more layers are laminated.

[0052] When insulating resin film 15 has multiple layers, each layer can have a separate function. When insulating resin film 15 includes two layers, for example, first layer 31 may be an adhesive layer that adheres to conductor 14. Furthermore, second layer 32 may be a heat-resistant layer that increases mechanical strength by making leads 13 less likely to be crushed when thermocompression-bonded to exterior body 11. As shown in FIG. 4B , when insulating resin film 15 further includes third layer 33, third layer 33 may be an adhesive layer that increases adhesion to exterior body 11.

[0053] According to the investigations of the inventors of the present invention, it has been confirmed that when insulating resin film 15 is thermocompression bonded to conductor 14, it is mainly first layer 31 that experiences large dimensional changes.

[0054] Based on the above findings, the inventors of the present invention conducted further studies and found that by providing first layer 31 with a predetermined loss factor, it is possible to reduce the thermal shrinkage of insulating resin film 15 when insulating resin film 15 is thermocompression bonded to conductor 14, and that first layer 31 can deform appropriately to match the shape of conductor 14, thereby completing the present invention.

[0055] As shown in Figures 4A and 4B, the insulating resin film 15 of this embodiment can have a first layer 31 having a first surface 400 exposed to the outside and a second surface 401 located opposite the first surface 400, and a second layer 32 laminated to the second surface 401 of the first layer 31.

[0056] The first surface 400 of the first layer 31 is the surface that is thermocompression bonded to the conductor 14. The second surface 401 of the first layer 31 is the interface with the second layer 32.

[0057] Each layer will be described below. (3-1) 1st layer (3-1-1) Loss coefficient of the first layer The first layer 31 can have a first loss factor / second loss factor, which is a ratio between a first loss factor that is a loss factor at a first temperature obtained by adding 10°C to the peak melting temperature, and a second loss factor that is a loss factor at a second temperature of 50°C, of ​​1.5 or more and 7.0 or less.

[0058] The loss factor tan δ is the ratio of the loss modulus (G") to the storage modulus (G'). That is, the loss factor can be calculated using the following formula:

[0059] Loss factor (tanδ) = loss modulus (G´) ÷ storage modulus (G´) The storage modulus (G´) represents elasticity and is the component of the energy generated by external forces and strains in an object that is stored internally.

[0060] The loss modulus (G´´) represents viscosity and is the component of the energy generated by external forces and strain in an object that is diffused to the outside due to heat generation, etc.

[0061] The loss factor tan δ is an index that represents the balance between viscosity and elasticity. The larger the loss factor value, the greater the viscosity, and the smaller the value, the greater the elasticity.

[0062] When insulating resin film 15 is thermocompression-bonded to conductor 14, first layer 31 is heated to melt at least a portion thereof. Therefore, the first loss factor at the first temperature, which is the melting peak temperature plus 10°C, means the loss factor of first layer 31 in the state in which insulating resin film 15 is thermocompression-bonded to conductor 14.

[0063] The second loss factor at the second temperature of 50° C. means the loss factor in the state before the insulating resin film 15 is heated for thermocompression bonding to the conductor 14.

[0064] The value of the loss factor varies depending on the type of resin contained in the first layer 31. Therefore, to avoid the influence of the type of resin, the ratio of the first loss factor at the first temperature to the second loss factor at the second temperature, i.e., first loss factor / second loss factor, is used as an index.

[0065] According to the investigations of the present inventors, by setting the first loss factor / second loss factor of the first layer 31 to 7.0 or less, dimensional change in the first layer 31 can be prevented when the insulating resin film 15 is thermocompression bonded to the conductor 14, resulting in an insulating resin film with excellent dimensional stability. This is because, by setting the first loss factor / second loss factor of the first layer 31 to 7.0 or less, the ratio of the loss modulus, i.e., the viscosity, decreases, making the insulating resin film closer to an elastic body, thereby reducing dimensional change when the insulating resin film 15 is thermocompression bonded to the conductor 14. From the viewpoint of particularly improving the dimensional stability of the insulating resin film 15, the first loss factor / second loss factor of the first layer 31 may be 6.5 or less, 6.0 or less, 5.5 or less, or 5.2 or less.

[0066] However, for example, if the first loss coefficient / second loss coefficient of the first layer 31 is made excessively small, the first layer 31 cannot deform to fit the shape of the conductor 14 when the insulating resin film 15 is thermocompression-bonded to the conductor 14, and a gap may occur between the insulating resin film 15 and the conductor 14.

[0067] By setting the first loss factor / second loss factor of the first layer 31 to 1.5 or more, the first layer 31 can be appropriately deformed to fit the shape of the conductor 14 when the insulating resin film 15 is thermocompression bonded to the conductor 14, thereby reducing the gap between the insulating resin film 15 and the conductor 14. From the viewpoint of particularly reducing the gap between the insulating resin film 15 and the conductor 14, the first loss factor / second loss factor of the first layer 31 may be 1.6 or more, 1.7 or more, or 2.1 or more.

[0068] The first loss factor of the first layer 31 may be equal to or greater than 0.15 and equal to or less than 0.9.

[0069] By setting the first loss factor to 0.9 or less, it is possible to prevent dimensional change in the first layer 31 when the insulating resin film 15 is thermocompression bonded to the conductor 14, thereby providing an insulating resin film with excellent dimensional stability. From the viewpoint of particularly improving the dimensional stability of the insulating resin film 15, the first loss factor may be 0.8 or less, or may be 0.7 or less.

[0070] By setting the first loss factor to 0.15 or more, the first layer 31 can be appropriately deformed to fit the shape of the conductor 14 when the insulating resin film 15 is thermocompression bonded to the conductor 14, thereby reducing the gap between the insulating resin film 15 and the conductor 14. From the viewpoint of particularly reducing the gap between the insulating resin film 15 and the conductor 14, the first loss factor of the first layer 31 may be 0.18 or more, or may be 0.20 or more. (3-1-2) Materials for the first layer (thermoplastic resin) The first layer 31 may contain a thermoplastic resin so that it can be thermocompression bonded to the conductor 14. The thermoplastic resin may be one or more selected from polyolefin resin, polyester resin, polystyrene resin, polyvinyl chloride resin, etc. Examples of the polyolefin resin include polyethylene, polypropylene, acid-modified polyolefin resin such as acid-modified polyethylene, acid-modified polypropylene, etc. Examples of the polyester resin include polyethylene terephthalate resin, etc. Examples of the acid-modified polyolefin include maleic anhydride-modified polyolefin.

[0071] The first layer 31 may contain a polyolefin resin. Because polyolefin resins have excellent cross-linking properties, the loss factor of the first layer 31 can be easily controlled by including a polyolefin resin in the first layer 31. Furthermore, the glass transition point and melting point of polyolefin resins are sufficiently higher than the operating temperatures of various batteries, such as lithium-ion secondary batteries, to which the lead having the insulating resin film 15 of this embodiment is expected to be applied. Therefore, the inclusion of a polyolefin resin in the first layer 31 improves the adhesion between the exterior body and the lead in a battery using the lead having the insulating resin film 15 of this embodiment. Furthermore, since a layer containing a polyolefin resin is often disposed on the surface of the exterior body that comes into contact with the lead, the inclusion of a polyolefin resin in the first layer 31 also improves the adhesion between the exterior body and the lead having the insulating resin film 15 of this embodiment. (Crosslinking agent) The loss factor tan δ of the first layer 31 can be selected depending on the material contained in the first layer 31 and the degree of cross-linking of the first layer 31.

[0072] The first layer 31 is a layer that is provided for the purpose of deforming and conforming to the shape of the conductor 14 when the insulating resin film 15 is thermocompression bonded to the conductor 14, and therefore has not conventionally been cross-linked. However, according to the studies of the present inventors, by appropriately cross-linking the first layer 31, the loss factor of the first layer 31 can be controlled and dimensional stability when the insulating resin film 15 is thermocompression bonded to the conductor 14 can be improved. Therefore, the first layer 31 can also be cross-linked. Furthermore, the first layer 31 may contain a cross-linking agent.

[0073] By including a cross-linking agent in the first layer 31, the first layer 31 can be cross-linked, and the degree of cross-linking in the first layer 31 can be easily controlled by adjusting the blending ratio of the cross-linking agent. Therefore, by including a cross-linking agent in the first layer 31, the loss factor of the first layer 31 can also be controlled.

[0074] The crosslinking agent contained in the first layer 31 is not particularly limited and can be selected depending on the crosslinking method, etc. The crosslinking agent may, for example, include a compound containing at least two unsaturated groups in the molecule. The crosslinking agent may be one or more selected from triallyl isocyanurate (TAIC (registered trademark)), trimethylolpropane trimethacrylate, tris(2-acryloyloxyethyl) isocyanurate, etc. The blending ratio of the crosslinking agent in the first layer 31 is not particularly limited, but may be more than 0 parts by mass and 10 parts by mass or less, or 0.1 parts by mass or more and 5 parts by mass or less, per 100 parts by mass of the resin component.

[0075] 4A and 4B, the insulating resin film 15 may also include a second layer 32. The second layer 32 may be a heat-resistant layer that increases the mechanical strength and makes the leads 13 less likely to be crushed when thermocompression-bonded to the exterior body 11. Therefore, the degree of cross-linking in the second layer 32 may be equal to or greater than that of the first layer 31.

[0076] Therefore, the content of the cross-linking agent in the first layer 31 on a mass basis may be equal to or less than the content of the cross-linking agent in the second layer 32 on a mass basis.

[0077] The degree of crosslinking in each layer can be controlled by the amount of electron beam irradiation used during crosslinking, the blending ratio of the crosslinking agent in each layer, and the like.

[0078] Therefore, by setting the content of the cross-linking agent in the first layer 31 by mass to be equal to or less than the content of the cross-linking agent in the second layer 32 by mass, the degree of cross-linking in the first layer 31 can be equal to or less than that of the second layer 32. By setting the degree of cross-linking in the first layer 31 to be equal to or less than that of the second layer 32, when the insulating resin film 15 is thermocompression bonded to the conductor 14, the first layer 31 can be appropriately deformed, and the gap between the conductor 14 and the insulating resin film 15 can be reduced.

[0079] The content ratio of the cross-linking agent may also vary within the first layer 31. For example, the content ratio of the cross-linking agent on a mass basis may be greater in the second surface 401 of the first layer 31 than in the first surface 400.

[0080] The first surface 400 of the first layer 31 is the surface exposed to the outside of the insulating resin film 15, and is the surface that comes into direct contact with the conductor 14 when the insulating resin film 15 is thermocompression bonded to the conductor 14. The second surface 401 is the interface with the second layer 32.

[0081] Therefore, in the first layer 31, the content ratio of the cross-linking agent on a mass basis of the second surface 401 is greater than that of the first surface 400, so that the first surface 400 in contact with the conductor 14 can be appropriately deformed when the insulating resin film 15 is thermocompression bonded to the conductor 14. Therefore, the gap between the conductor 14 and the insulating resin film 15 can be reduced.

[0082] Furthermore, when insulating resin film 15 is thermocompression bonded to conductor 14, second surface 401 is less likely to deform than first surface 400, and therefore dimensional stability of insulating resin film 15 can be improved.

[0083] The method for crosslinking the first layer 31 is not particularly limited, and for example, the first layer 31 may be crosslinked by irradiation with ionizing radiation such as accelerated electron beams or gamma rays. (additives) The first layer 31 may contain any additives other than the thermoplastic resin and crosslinking agent, such as one or more additives selected from a flame retardant, an ultraviolet absorber, a light stabilizer, a heat stabilizer, a lubricant, a colorant, and the like. (3-2) 2nd layer, 3rd layer The second layer 32 and the third layer 33 may also contain a thermoplastic resin, a crosslinking agent, and an additive. The thermoplastic resin, crosslinking agent, and additive described for the first layer 31 can be used for the thermoplastic resin, crosslinking agent, and additive, so a description thereof will be omitted.

[0084] The first layer 31, the second layer 32, and the third layer 33 may have the same or different compositions. When the first layer 31, the second layer 32, and the third layer 33 are functionally separated, for example, the second layer 32 can be used as a heat-resistant layer, and therefore the degree of crosslinking can be made equal to or greater than that of the first layer 31. Therefore, the blending ratio of the crosslinking agent contained in the second layer 32 and the degree of irradiation with ionizing radiation during crosslinking can also be selected. The composition, degree of crosslinking, etc. of the third layer 33 can also be selected to, for example, increase adhesion to the exterior body 11.

[0085] The thickness T31 of the first layer 31, the thickness T32 of the second layer 32, and the thickness T33 of the third layer 33 may be the same or different from each other. The thickness T31 of the first layer 31, the thickness T32 of the second layer 32, and the thickness T33 of the third layer 33 may each be, for example, 30 μm or more and 200 μm or less.

[0086] Here, we have described the cases where the insulating resin film 15 includes a first layer 31 and a second layer 32, and the cases where it includes a first layer 31, a second layer 32, and a third layer 33, respectively, but the number of layers that the insulating resin film 15 has is not limited to two or three layers, and may be four or more layers. (4) Manufacturing method of insulating resin film for leads The method for manufacturing the insulating resin film 15 of this embodiment is not particularly limited, and the insulating resin film 15 can be manufactured so that the loss factor tan δ of the first layer 31 has a predetermined characteristic.

[0087] For example, the method for producing the insulating resin film of this embodiment can include a layer forming step and a bonding step.

[0088] In the layer formation step, it is possible to form each layer of the insulating resin film 15. There are no particular limitations on the specific method for forming each layer of the insulating resin film 15, but each layer can be formed by kneading the thermoplastic resin, crosslinking agent, etc. contained in each layer and extruding the mixture.

[0089] In the laminating step, the layers of the insulating resin film 15 formed in the layer forming step are stacked and can be laminated by thermocompression bonding or the like.

[0090] When crosslinking is performed for each layer of the insulating resin film 15, the crosslinking may be performed for each layer after the layer forming step and before the laminating step. Alternatively, the crosslinking may be performed collectively on the obtained laminate after the laminating step.

[0091] The second loss coefficients of the first layer 31 and the second layer 32 may be approximately the same. The first loss coefficient of the first layer 31 may be larger than the first loss coefficient of the second layer 32.

[0092] When crosslinking is performed in both the first layer 31 and the second layer 32, the first loss factor of the first layer 31 can be made larger than the first loss factor of the second layer 32 by making the content of the crosslinking agent in the first layer 31 smaller than the content of the crosslinking agent in the second layer 32.

[0093] Furthermore, when crosslinking is performed on both the first layer 31 and the second layer 32, the intensity of ionizing radiation, such as accelerated electron beams or gamma rays, applied to the first layer 31 may be lower than the intensity of ionizing radiation applied to the second layer 32. This allows the first loss factor of the first layer 31 to be larger than the first loss factor of the second layer 32. The first loss factor of the first layer 31 can be adjusted. When crosslinking the first layer 31 and the second layer 32 together, the first loss factor of the first layer 31 can be larger than the first loss factor of the second layer 32 by making the content of crosslinking agent in the first layer 31 smaller than the content of crosslinking agent in the second layer 32. [Leads with insulating resin film] The lead 13 with an insulating resin film of this embodiment can have a plate-shaped conductor 14 having a rectangular upper surface 141 and a rectangular lower surface 142, and an insulating resin film 15. The insulating resin film 15 includes a first insulating resin film 151 disposed on the upper surface 141 of the conductor 14, and a second insulating resin film 152 disposed on the lower surface 142 of the conductor 14.

[0094] The insulating resin film 15 is an insulating resin film for a lead according to one embodiment of the present disclosure, and is laminated in the order of the conductor 14, the first layer 31, and the second layer 32, for example, as shown in Fig. 3. That is, the insulating resin film 15 can be disposed on the conductor 14 so that the first layer 31 and the second layer 32 are laminated in this order from the position closest to the conductor 14.

[0095] The lead with an insulating resin film of this embodiment has an insulating resin film 15 according to one aspect of the present disclosure bonded to a conductor 14 by thermocompression bonding.

[0096] The insulating resin film 15 according to one aspect of the present disclosure has excellent dimensional stability when thermocompression bonded to the conductor 14. Therefore, the lead 13 with an insulating resin film of this embodiment can have an insulating resin film with desired dimensions. In addition, the gap between the conductor 14 and the insulating resin film 15 can be sufficiently reduced.

[0097] According to the lead 13 with insulating resin film of this embodiment, it is possible to prevent wrinkles and the like from occurring on the surface of the insulating resin film 15, and therefore it is possible to improve adhesion with the outer casing 11 when the outer casing 11 is thermocompression bonded.

[0098] The lead with insulating resin film of this embodiment has been explained in "(2) Lead with insulating resin film" in the section on insulating resin film for leads, so explanation will be omitted. [Example]

[0099] Specific examples will be described below, but the present invention is not limited to these examples and includes equivalents and modifications within the scope of the effects of the present invention. 1. Evaluation Method The insulating resin films produced in the following experimental examples were evaluated as follows. (1) Melting peak temperature, first temperature The melting peak temperature was evaluated using DSC (Differential Scanning Calorimetry).

[0100] First, the first layer 31 was heated from room temperature (25°C) to 200°C at a heating rate of 20°C / min using a DSC (model: DSC 204 F1 phoenix, manufactured by NETZCH), and then cooled to room temperature (25°C) once (1 cycle).

[0101] Next, the temperature was raised again from room temperature (25°C) to 200°C at a rate of 20°C / min (2 cycles). The endothermic peak temperature that appeared during the 2nd cycle was taken as the melting peak temperature. To measure the melting peak temperature, the first layer was heated and cooled in a nitrogen atmosphere in both the 1st and 2nd cycles.

[0102] The first temperature was determined as the temperature obtained by adding 10°C to the melting peak temperature.

[0103] After the first cycle of heat treatment, the melting peak temperature is determined from the DSC curve of the second cycle, thereby avoiding the influence of the thermal history that the first layer 31 has undergone during manufacturing, etc., and enabling stable evaluation of the physical properties of the resin of the first layer 31. (2) Loss factor The loss factor of the first layer 31 was measured while the temperature of the first layer 31 was increased from room temperature (25°C) to 200°C at a rate of 10°C / min.

[0104] The loss factor was measured using a dynamic viscoelasticity measuring device (model: DVA220, manufactured by IT Measurement & Control Co., Ltd.) The first layer 31 in the form of a film was subjected to measurement in a tensile mode by applying a load, with the strain amount being 0.08% and the frequency being 10 Hz.

[0105] From the loss factor tan δ obtained at each temperature, the first loss factor at the first temperature, which is the melting peak temperature plus 10°C, and the second loss factor at the second temperature, which is 50°C, were calculated. In the following experimental examples, the melting peak temperature was 140°C in all cases, so the first temperature was set to 150°C.

[0106] Furthermore, the ratio of the first loss factor to the second loss factor, i.e., first loss factor / second loss factor, was calculated and is shown in the column "first loss factor / second loss factor" in Fig. 6. (3) Evaluation of shrinkage, embedding, and overall evaluation Leads with insulating resin film as shown in Figures 2 and 3 were fabricated, and the shrinkage and embedding properties were evaluated by observing each part.

[0107] An aluminum plate with a thickness of 0.4 mm was used as the conductor 14. Note that the thickness of the conductor 14 is the thickness of the portion excluding the end portion 14A, which has a tapered cross section, as shown in Figures 5A and 5B.

[0108] The insulating resin film 15 has a length L15 of 20 mm along the Y axis and extends 1 cm on each side from the conductor 14; in other words, in Figure 2, the length W15 along the X axis is 2 cm longer than the length W14 of the conductor 14 along the X axis.

[0109] Then, insulating resin film 15 was placed on each of upper surface 141 and lower surface 142 of conductor 14, and heated at 150° C. for 2 minutes while applying a pressure of 0.05 MPa, thereby thermocompression bonding insulating resin film 15 to conductor 14. (Evaluation of shrinkage) The appearance of the obtained lead with insulating resin film was observed, and if no wrinkles were confirmed in the insulating resin film 15, the shrinkage was rated as A, and if wrinkles were confirmed in the insulating resin film 15, the shrinkage was rated as B. (Evaluation of embedding ability) The resulting lead with insulating resin film was observed in cross section along line BB in Figure 2. Schematic cross-sectional views along line BB are shown in Figures 5A and 5B.

[0110] As shown in Figures 5A and 5B, the conductor 14 used has a tapered shape in which the thickness decreases toward the end 14A corresponding to the side 23 and the side 24 in Figure 2. Therefore, as shown in Figure 5A, when the insulating resin film 15 was unable to deform to follow the shape of the end 14A of the conductor 14 during thermocompression bonding, and a gap 51 was observed between the end 14A of the conductor 14 and the insulating resin film 15, the filling ability was evaluated as B. In contrast, as shown in Figure 5B, when the insulating resin film 15 was deformed to follow the shape of the end 14A of the conductor 14 during thermocompression bonding, and no gap was observed between the end 14A of the conductor 14 and the insulating resin film 15, the filling ability was evaluated as A.

[0111] In the following experimental examples, the insulating resin film 15 has a first layer 31 and a second layer 32, but the individual layers are not shown in FIGS. 5A and 5B.

[0112] When the evaluation of shrinkage and the evaluation of embedding ability were both A, the overall evaluation was rated as A. When the evaluation of either shrinkage or embedding ability was B, the overall evaluation was rated as B.

[0113] If the overall rating is A, the insulating resin film for leads can be evaluated as having excellent dimensional stability when thermocompression bonded to a conductor. 2. Insulating resin film manufacturing conditions The insulating resin films produced in each experiment will be described below.

[0114] Experimental Examples 4, 5, 6, and 7 are working examples, and Experimental Examples 1, 2, 3, 8, and 9 are comparative examples. [Experimental Example 1] (1) Layer formation process (1-1) First layer formation process The first layer 31 was produced by the following procedure.

[0115] Polypropylene resin, which is a thermoplastic resin, and triallyl isocyanurate, which is a crosslinking agent, were mixed and extrusion-molded to produce a film-shaped first layer 31. Triallyl isocyanurate was added in an amount of 0.5 parts by mass per 100 parts by mass of polypropylene resin.

[0116] In this experimental example, the film obtained after extrusion molding was used as the first layer 31, and was not crosslinked. (1-2) Second layer formation process The second layer 32 was produced by the following procedure.

[0117] A thermoplastic polypropylene resin and a crosslinking agent, triallyl isocyanurate, were mixed and extruded to produce a film. Triallyl isocyanurate was added in an amount of 0.5 parts by mass per 100 parts by mass of polypropylene resin.

[0118] The film obtained after extrusion was irradiated with an electron beam at an acceleration voltage of 200 kV and an exposure dose of 200 kGy to crosslink the film, thereby producing the second layer 32. (2) Bonding process The first layer 31 and the second layer 32 obtained in the layer forming step were bonded together by thermocompression bonding to form an insulating resin film of Experimental Example 1.

[0119] The evaluation results are shown in Figure 6. [Experimental Examples 2 to 9] In the first layer forming step, the film obtained after extrusion molding was irradiated with an electron beam under the conditions shown in FIG. 6 to crosslink it.

[0120] Except for the above points, the insulating resin film was produced under the same conditions as in Experimental Example 1.

[0121] The evaluation results are shown in Figure 6.

[0122] According to FIG. 6, the first layer of Experimental Examples 4 to 7 has a ratio of first loss factor / second loss factor of 1.5 or more and 7.0 or less.

[0123] The overall evaluation of the insulating resin films of Experimental Examples 4 to 7 was A, confirming that the insulating resin films of Experimental Examples 4 to 7 have a first layer that has excellent dimensional stability when thermocompression bonded to the conductor 14. [Explanation of symbols]

[0124] 10 batteries 11 Exterior body 110 Seal part 111 1st resin layer 112 Metal layer 113 Second resin layer 12 Electrode laminate 13 Leads (leads with insulating resin film) 14 Conductors 141 Top surface 142 Bottom surface 14A End 15 Insulating resin film 151 First insulating resin film 152 Second insulating resin film 16 test specimens 21 sides 22 sides 23 sides 24 sides 25 First end area 26 Second end area L14 length W14 length L15 length W15 length 31 1st layer 32 2nd layer 33 3rd layer 400 Page 1 401 2nd page T31 Thickness T32 thickness T33 Thickness 51 Gap XX axis YY axis ZZ axis

Claims

1. a first layer having a first surface and a second surface opposite the first surface; a second layer laminated on the second surface of the first layer, an insulating resin film for leads, wherein a first loss factor / second loss factor, which is a ratio of a first loss factor at a first temperature obtained by adding 10°C to a peak melting temperature of the first layer to a second loss factor at a second temperature of 50°C, is 1.5 or more and 7.0 or less.

2. 2. The insulating resin film for leads according to claim 1, wherein the first loss factor is 0.15 or more and 0.9 or less.

3. 3. The insulating resin film for leads according to claim 1, wherein the first layer contains a polyolefin resin.

4. 3. The insulating resin film for leads according to claim 1, wherein the first layer contains a crosslinking agent.

5. 5. The insulating resin film for leads according to claim 4, wherein the content of the cross-linking agent in the first layer based on the mass of the first layer is equal to or less than the content of the cross-linking agent in the second layer based on the mass of the second layer.

6. The insulating resin film for leads according to claim 4 , wherein the content of the cross-linking agent on a mass basis is greater on the second surface of the first layer than on the first surface.

7. a plate-shaped conductor having rectangular upper and lower surfaces; an insulating resin film including a first insulating resin film disposed on the upper surface of the conductor and a second insulating resin film disposed on the lower surface of the conductor; 3. A lead with an insulating resin film, wherein the insulating resin film is the insulating resin film for a lead according to claim 1 or 2, and the conductor, the first layer, and the second layer are laminated in this order.

Images