JP2009289542A - Laminated film, and exoergic object packing body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a laminated film excellent in a heat-radiation property compared with the conventional film, and to obtain an exoergic object packing body. <P>SOLUTION: In the laminated film having a protection layer 1 made of a plastic film, a metal layer 3 formed on the protection layer and made of a metal foil, a heat-melting layer 5 made of the plastic film formed on the metal layer, and an adhesive layer 2 formed between the metal layer and the heat-melting layer, it is characterized in that a heat-absorbing function is given to the adhesive layer 2. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a laminate film having efficient heat transfer and heat dissipation effects, and a heating material package using the film.

  As is well known, a laminate film has a structure in which a metal foil is sandwiched between layers made of plastic. In particular, laminate films using aluminum foil have excellent performance in moisture proofing, gas barrier properties, and light shielding properties, and are widely used in chemical industrial products and pharmaceuticals as packaging materials.

  In recent years, from the viewpoint of protecting the global environment, energy saving of various industrial equipment and home appliances has become an urgent issue. In particular, in automobile technology, HEV is considered to be the core of future self-runners as a method that can improve fuel efficiency without impairing driving performance, increase vehicle cost, and expect the most volume sales.

At present, nickel metal hydride batteries are used as a power supply system for HEVs, but attention has been focused on the development of lithium ion secondary batteries for HEVs with higher energy density.
Conventional lithium ion secondary batteries are mainly square lithium ion secondary batteries as used in mobile phones. However, as interest in HEV and aviation applications increases, performances such as space saving, high energy density, and high rate are required. Therefore, development of a thin and lightweight laminated lithium secondary battery has been advanced from the battery container of a metal can.

  That is, a lithium ion secondary battery having a high energy density was obtained by changing the exterior container from a metal to an aluminum laminate film. However, although the laminated lithium secondary battery has a high energy density, when an excessive stress such as a charge / discharge stress or an overcharge is applied, the lithium cell generates heat and expands. And in the worst case, it may rupture and trigger a fire.

  From the above phenomenon, the laminate type lithium ion secondary battery has a disadvantage that the battery life is reduced due to the expansion of heat generation, and the amount of electric power is suppressed by reducing the stress to prevent the expansion of heat generation. Therefore, how to efficiently dissipate the heat inside the lithium cell is important for the development of a laminate type laminated ion secondary battery with high output and long life.

Until now, in Patent Document 1, although it is a structure inside an assembled battery, in order to efficiently release the heat inside the lithium cell to the outside, a conductor is brought into contact with one surface of the exterior of the cell and the heat is released to the outside. is doing. Moreover, in patent document 2, the thermal radiation layer is formed in the lithium polymer battery exterior body surface, and the thermal radiation performance is improved.
JP 2007-123016 A JP 2006-114575 A

The techniques disclosed in Patent Documents 1 and 2 described above efficiently release heat that has reached the metal layer of the exterior body such as a laminate film to the outside.
However, since the metal used for the laminate film, such as aluminum, has the property of reflecting infrared rays, the heat generated inside the exterior body is reflected by the metal in the exterior body and stored inside.

In addition, when a heat conductor sheet is installed on the exterior surface to improve heat dissipation characteristics, it is effective when the temperature inside the exterior material is higher than the external temperature. In the case where the temperature is exceeded, there is a possibility that the heat conductive sheet has a heating effect on the package.
Here, if the heat absorption function is imparted to the heat generating element side of the laminate film metal layer, the heat dissipation of the current laminate film can be enhanced.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a laminate film that can improve heat dissipation as compared with the conventional one, and a heating material package using the film as an exterior material of a heating element. To do.

A laminate film according to the present invention includes a protective layer made of a plastic film, a metal layer made of a metal foil formed on the protective layer, and a heat-sealing layer made of a plastic film formed on the metal layer. In the laminate film comprising the metal layer and the adhesive layer formed between the heat-sealing layers, the adhesive layer, or the heat-sealing layer, or the metal layer and the adhesive layer, or the adhesive layer and the heat-sealing layer, or A heat absorption function is imparted to at least one of the outer sides of the heat-fusible layer.
Moreover, the heating material package according to the present invention is characterized in that the laminate film is used as an exterior material for a heating element.

According to the present invention, the heat generating element side on the metal layer, specifically, the adhesive layer or the thermal fusion layer, or the metal layer and the adhesive layer, or the adhesive layer and the thermal fusion layer, or the outer side of the thermal fusion layer. By imparting a heat absorption function to at least one of these, the heat dissipation of the laminate film can be enhanced. In addition, according to the heating material package using such a laminate film, heat from the heating element is not reflected by the metal layer and is absorbed by the heat-sealing layer, so that it is efficiently conducted to the metal layer, The heat dissipation characteristics can be improved.
In addition, when the temperature inside the package of the heat generating element is regarded as important, for example, in a laminated lithium ion secondary battery, the improvement of heat dissipation characteristics can suppress the decomposition of the electrolyte solution at a temperature higher than the reference value It is possible to improve battery life and reliability.

Hereinafter, the laminate film and the heating material package according to the present invention will be described.
In the present invention, stretched polyester resin or nylon film can be used as the material for the protective layer. Here, examples of the stretched polyester resin include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, copolymerized polyester, and polycarbonate. Examples of the nylon film include nylon 6, nylon 6,6, a copolymer of nylon 6 and nylon 6,6, and nylon 6,10.
In the present invention, the protective layer is used for improving the mechanical strength, improving the pinhole resistance and the insulation from the battery outer body, and may be a single layer. Even if pinholes are formed, the two or more layers may be used so that the pinholes do not penetrate across the front and back of the protective layer. For example, when laminating in two layers, the same kind and the same material such as stretched polyester and stretched polyester, or nylon film and nylon film may be combined, or different types and different materials such as stretched polyester and nylon film may be combined. You may laminate.
When too many protective layers are laminated, the mechanical strength and the like are improved, but the heat dissipation characteristics are lowered, and the battery life may be shortened accordingly, so about two layers are preferable.

  In the present invention, the metal layer is a layer for preventing water vapor from entering the inside of the battery, in particular, the lithium ion battery from the outside, stabilizing the pinhole of the metal layer alone and the processing suitability, and providing a pinhole-resistant. Therefore, metals such as aluminum and nickel are used.

  In the present invention, as the heat-fusible layer, polyolefin resin such as polyethylene, ethylene-α-olefin copolymer, polypropylene, propylene-α-olefin copolymer, ethylene-vinyl acetate copolymer or ethylene-α, β Acid-modified products and silane-modified products of ethylene copolymers such as unsaturated carboxylic acid copolymers are used.

  In the present invention, the adhesive layer is a layer provided for adhering the metal layer and the heat fusion layer as the inner layer of the outer package, and is selected from materials used for the heat fusion layer. Specifically, for example, an acid-modified polyolefin resin, a polyolefin resin graft-modified with an unsaturated carboxylic acid, a copolymer of ethylene or propylene and acrylic acid, or methacrylic acid, or a metal-crosslinked polyolefin resin is used. Can do.

Hereinafter, the laminate film of the present invention will be described with reference to the drawings. In addition, this invention is not limited to a following example.
(Example 1)
Please refer to FIG. In the figure, reference numerals 1 and 2 are two-layered protective layers, reference numeral 1 is a protective layer made of polyethylene terephthalate (PET), and reference numeral 2 is a protective layer made of nylon. In these laminated protective layers, a metal layer 3 made of aluminum (Al) foil, an adhesive layer 4 and a heat fusion layer 5 made of polypropylene (PP) are sequentially formed. Here, the adhesive layer 4 is provided with a heat absorption function, and is composed of a black colored layer obtained by kneading a double-sided adhesive PP with a heat absorbent. As the material for the adhesive layer 4, a material that does not have a problem in adhesiveness when used after kneading can be used, and materials used for pigments, such as carbon and metal oxides, can be used. In Example 1, carbon was used. In the adhesive layer 4, carbon can be colored black with the highest heat absorption efficiency by kneading with double-sided adhesive PP, but is not limited to black and may be any material that increases the heat absorption efficiency by kneading.

  As described above, the laminate film according to Example 1 is obtained by kneading a heat absorbing agent on the protective layer 1 made of PET, the protective layer 2 made of nylon, the metal layer 3 made of Al foil, and the double-sided adhesive PP. The heat-absorbing layer 4 and the heat-bonding layer 5 made of PP are sequentially formed.

(Example 2)
Please refer to FIG. However, the same members as those in FIG.
Reference numeral 6 in the figure is an adhesive layer made of double-sided adhesive PP. On the adhesive layer 6, a heat fusion layer 7 having a heat absorption function is formed. The heat sealing layer 7 is obtained by kneading carbon with PP.
As described above, the laminate film according to Example 2 includes a protective layer 1 made of PET, a protective layer 2 made of nylon, a metal layer 3 made of Al foil, an adhesive layer 6 made of double-sided adhesive PP, and PP. The heat-sealing layer 7 provided with a heat absorption function obtained by kneading carbon is sequentially formed.

(Example 3)
Please refer to FIG. However, the same members as those in FIG. 1 and FIG.
Reference numeral 8 in the figure is a heat absorbing sheet having a heat absorbing function formed on the heat-fusible layer 5. Here, as the heat-absorbing sheet 8, a material that has good adhesion to the heat-fusible layer 5 and that does not affect the inside of the packaging material (material wrapped by the laminate film), specifically, PP is kneaded with graphite. Examples include, but are not limited to: For example, carbon or metal oxide can be used instead of the graphite.

  As described above, the laminate film according to Example 3 includes a protective layer 1 made of PET, a protective layer 2 made of nylon, a metal layer 3 made of Al foil, an adhesive layer 6 made of double-sided adhesive PP, and PP. The heat sealing layer 5 and the heat absorbing sheet 8 having a heat absorbing function are sequentially formed.

Example 4
Please refer to FIG. However, the same members as those in FIGS.
Reference numeral 9 in the figure is a heat absorption sheet formed between the metal layer 3 and the adhesive layer 6 and having a heat absorption function. As the heat absorbing sheet 9, a double-sided adhesive PP kneaded with graphite was used. For example, carbon or metal oxide can be used instead of the graphite.
As described above, the laminate film according to Example 4 is the heat formed by kneading graphite on the protective layer 1 made of PET, the protective layer 2 made of nylon, the metal layer 3 made of Al foil, and the double-sided adhesive PP. The heat absorbing sheet 9 having an absorbing function, the adhesive layer 6 made of double-sided adhesive PP, and the heat fusion layer 5 made of PP are sequentially formed.

(Example 5)
Please refer to FIG. However, the same members as those in FIGS.
Reference numeral 10 in the figure is a heat absorbing sheet having a heat absorbing function, which is formed between the adhesive layer 6 and the heat sealing layer 5. As the heat absorbing sheet 10, a double-sided adhesive PP kneaded with graphite was used. For example, carbon or metal oxide can be used instead of the graphite.
As described above, the laminate film according to Example 5 includes a protective layer 1 made of PET, a protective layer 2 made of nylon, a metal layer 3 made of Al foil, a heat absorbing sheet 10 having a heat absorbing function, and a modified PP. The heat-absorbing layer 10 having a heat-absorbing function obtained by kneading graphite with double-sided adhesive PP, and the heat-sealing layer 5 made of PP are sequentially formed.

(Examples 6 to 8)
The laminate film of Example 6 is not shown, but on a protective layer made of PET, a protective layer made of nylon, a metal layer made of Al foil, an adhesive layer having a heat absorption function made of double-sided adhesive PP, and PP. Thus, the heat fusion layer having the heat absorption function is sequentially formed.

  Although not shown, the laminate film of Example 7 is made of a protective layer made of PET, a protective layer made of nylon, a metal layer made of Al foil, an adhesive layer having a heat absorption function made of double-sided adhesive PP, and PP. The heat sealing layer having a heat absorption function is sequentially formed.

  Although not shown, the laminate film of Example 8 is made of a protective layer made of PET, a protective layer made of nylon, a metal layer made of Al foil, an adhesive layer having a heat absorption function made of double-sided adhesive PP, and PP. The heat sealing layer having a heat absorption function and the heat absorption sheet having a heat absorption function are sequentially formed.

(Conventional example 1)
Please refer to FIG. However, the same members as those in FIG. 1 and FIG.
The laminate film of Conventional Example 1 includes a protective layer 1 made of PET, a protective layer 2 made of nylon, a metal layer 3 made of Al foil, an adhesive layer 11 made of double-sided adhesive PP, and a heat fusion layer 12 made of PP. Are sequentially formed.

In order to compare the heat dissipation characteristics of the laminate films according to Example 1 and Conventional Example 1, a heat dissipation experiment was performed as shown in FIG. That is, the laminate film 22 according to the above example and the conventional laminate film 23 were contacted and fixed on the heat generating plate 21 so that the heat fusion layer side was in contact with the heat generating plate 21.
First, the heating plate 21 to which the laminate films 22 and 23 were bonded in the state of FIG. 7 was heated to 65 ° C. Next, in order to compare the heat dissipation of the subsequent laminate films 22 and 23, a thermography was placed on the surface of the protective layer 1 of the laminate film, and the change in temperature was observed. As a result, the conventional laminate film 23 reached 65 ° C. after 15.5 seconds of heat generation, whereas the laminate film 22 of the present invention reached 65 ° C. after 3.7 seconds of heat generation. From this result, it was confirmed that the laminate film 22 of the present invention has a higher heat absorption rate than the conventional laminate film 23. The results are as shown in Table 1 below.
Moreover, when the heat dissipation experiment similar to the above was done also about the laminate film which concerns on other Examples 2-8, the result shown in following Table 1 was obtained. In Table 1, “+” means that a function is imparted, and “double-sided adhesive PP + heat absorption” indicates double-sided adhesive PP imparted with a heat absorption function.

From Table 1, it can be seen that all the laminated films of the present invention have a faster heat absorption rate than the conventional laminated film. However, in Example 7 with many heat absorption layers, it can be seen that the time to reach 65 ° C. is long and the heat absorption rate is slow. Also, in the example in which the heat absorption layer is one layer, the film of Examples 2 and 3 that is not in contact with the metal layer is more heated than the film of Example 1 in which the metal layer is in contact with the heat absorption layer. It can be seen that the absorption rate is slow.
From the above results, it is desirable to provide a heat absorption layer at a position closer to the metal layer, and it can be seen that the heat dissipation effect of the laminate film is reduced when the number of heat absorption layers is too large.

(Conventional example 2)
The laminate film of Conventional Example 2 has a configuration in which a metal plate made of aluminum is attached to the outer surface of the laminate film of Conventional Example 1 for heat dissipation. Specifically, the laminate film of Conventional Example 2 is, on a metal plate made of aluminum, a protective layer made of PET, a protective layer made of nylon, a metal layer made of Al foil, an adhesive layer made of double-sided adhesive PP, and The heat sealing layer made of PP is sequentially formed.

Example 9
In Example 9, when the laminate film according to the present invention is actually used as a heating element packaging material, what effect is obtained as compared with the case where a conventional laminate film is used as a heating element packaging material. We investigated whether it was possible. The investigation was conducted using a laminated lithium secondary battery in which a heat generating element was a lithium ion cell. Further, in the lithium ion cell, a positive electrode made of a positive electrode active material, an Al current collector, a negative electrode active material, and a negative electrode made of a Cu current collector are laminated with a separator interposed therebetween, and a positive electrode terminal on the positive electrode current collector, A negative electrode terminal was joined on the negative electrode current collector, and an electrode group was used so that the negative electrode terminal had a rated capacity of 1 Ah.

  Two electrode groups are prepared, one in a battery pack using the laminate film of the present invention shown in FIG. 1, and the other in a battery pack using a conventional laminate film. Make a laminate film large enough to wrap the electrode group in a U shape so that the protective layer 1 is on the outside, put the battery group in such a way that the positive and negative terminals come out from the top, heat seal left and right, After injecting the electrolyte into each, the upper end portion was sealed under reduced pressure to obtain a laminated lithium secondary battery of 3.6 V, 1 Ah.

  Next, in order to compare a laminate type lithium ion secondary battery using the laminate film of the present invention as an exterior material and a laminate type lithium ion secondary battery using a conventional laminate film as an exterior material, at 25 ° C. A charge / discharge cycle test was performed in the set incubator. This charge / discharge cycle test was performed at a constant current / constant voltage (CC / CV) of 1C rate, and the charging voltage was 4.2V and the discharging voltage was 2.8V. In addition, it was set as the lifetime when 80% of the rated capacity was cut.

  The result is shown in FIG. In FIG. 8, the horizontal axis indicates the number of cycles, and the vertical axis indicates the capacity retention rate. In the conventional product using the laminate film of the comparative example as the exterior material, the capacity retention rate after 1400 cycles is 79.9%. there were. On the other hand, in the product of the present invention in which the laminate film of the present invention was used as an exterior material, the capacity retention rate after the lapse of 1400 cycles was 85.4%. In FIG. 8, curve a indicates the comparative example, curve b indicates the case of Example 1, curve c indicates the case of Example 2, curve d indicates the case of Example 3, and curve e indicates the case of the laminate film of Example 6.

  Thus, in this example, since the IC rate was tested using a lithium ion cell with a rated capacity of 1 Ah, the difference from the conventional product was 5.5% after 1400 cycles. However, it is clear that if the test is performed at a higher rate, the amount of heat generated from the lithium ion cell becomes larger, and if a high-capacity lithium ion cell is used, heat is more likely to accumulate. It is also clear that it appears larger.

  From the above experimental results, it was confirmed that the heat absorption rate of the laminate film of the present invention was higher than that of the conventional laminate film. In addition, the high heat conduction speed from the heat generating element side to the laminate film proves that the heat release speed of the laminate film is fast.

  From the above experimental results, when the laminate film of the present invention is used as an exterior material for a lithium ion cell, the capacity retention rate is higher than that of a lithium ion cell using the current laminate film as an exterior material. The lithium ion cell proved to have better heat dissipation characteristics than the lithium ion cell using the current product.

From the above, the following is considered.
1) The laminate film according to the present invention increases the amount of heat released from the heat generating element in a predetermined direction due to the excellent heat absorption performance from the heat fusion layer to the metal layer direction compared to the laminate film currently used. The heat dissipation efficiency of the heat generating means can be increased.
2) Since the laminate film according to the present invention is handled in the same manner as the current laminate film, it is very easy to apply to the system in which the current laminate film is used for the exterior of the heating element.
3) Therefore, the laminate film of the present invention can be used as an exterior material for power generation elements such as a laminated lithium ion secondary battery, and can also be applied to equipment such as home appliances that require heat dissipation in a predetermined direction. It is.

  Note that the present invention is not limited to the above-described embodiments as they are, and can be embodied by modifying the components without departing from the scope of the invention in the implementation stage. Further, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the above embodiments. For example, some components may be deleted from all the components shown in the embodiments. Furthermore, you may combine suitably the component covering different embodiment.

FIG. 1 is a cross-sectional view of a laminate film according to Example 1 of the present invention. FIG. 2 is a cross-sectional view of a laminate film according to Example 2 of the present invention. FIG. 3 is a cross-sectional view of a laminate film according to Example 3 of the present invention. FIG. 4 is a cross-sectional view of a laminate film according to Example 4 of the present invention. FIG. 5 is a cross-sectional view of a laminate film according to Example 5 of the present invention. FIG. 6 is a cross-sectional view of a laminate film according to a comparative example. FIG. 7 is an explanatory diagram for comparing the heat dissipation characteristics of the laminate films according to the present invention and a comparative example. FIG. 8 is a characteristic diagram showing the relationship between the capacity retention rate and the number of cycles of laminate films according to Examples 1, 2, 3, 6 and Comparative Examples of the present invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1, 2 ... Protective layer, 3 ... Metal layer, 4, 6 ... Adhesive layer, 5, 7 ... Heat-fusion layer, 8, 9, 10 ... Heat absorption sheet, 21 ... Heat generating plate, 22 ... Laminate film.

Claims (4)

A protective layer made of a plastic film, a metal layer made of a metal foil formed on the protective layer, a heat-fusible layer made of a plastic film formed on the metal layer, and the metal layer and heat-fused In a laminate film comprising an adhesive layer formed between layers,
A heat absorbing function is imparted to at least one of the adhesive layer, the heat-seal layer, the metal layer and the adhesive layer, the adhesive layer and the heat-seal layer, or the outside of the heat-seal layer. Laminated film. The laminate film according to claim 1, wherein a heat absorbing function is imparted by kneading a heat absorbing agent to at least one of the adhesive layer and the heat-fusible layer. A heating material package comprising the laminate film according to claim 1 or 2 as an exterior material for a heating element. The heating element package according to claim 3, wherein the heating element is a battery element.

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