Impact-resistant tape

Abstract

To provide an impact-resistant tape capable of protecting an element housed in a housing from external vibration and impact.SOLUTION: An impact-resistant tape includes a shrinkage film having a maximum shrinkage force of 450 mN or more, and a buffer film disposed on one surface of the shrinkage film, and having maximum shrinkage force smaller than that of the shrinkage film and a thickness of 30 μm or more. The shrinkage film and the buffer film are bonded at a plurality of dot-like and / or linear bonding sections arranged at intervals.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an impact resistant tape. [Background technology]

[0002] In recent years, many small, portable electronic devices have been developed and are used for a variety of purposes. Compared to stationary electronic devices, these electronic devices are required to have higher resistance to shock and vibration, and the various electronic components used in these devices are also required to be shock-resistant and vibration-resistant. For example, electrolytic capacitors, which are widely used in electronic devices, contain a capacitor element and an electrolyte solution within a housing. When subjected to external shock or vibration, the capacitor element of such electrolytic capacitors moves within the housing, easily causing damage to the capacitor element or disconnection. Therefore, measures such as placing a protective member between the capacitor element and the housing to improve shock resistance have been considered.

[0003] For example, Patent Document 1 describes wrapping a heat-shrinkable tape that shrinks in the width direction around a capacitor element. In this method, after the capacitor element wrapped with the heat-shrinkable tape is placed in a housing, heat is applied to the heat-shrinkable tape to cause wrinkles. This reduces the gap between the housing and the capacitor element, thereby preventing the capacitor element from moving within the housing. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-251837 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the method of Patent Document 1 does not allow for control of the position or height of wrinkles in the heat-shrinkable tape. Furthermore, this method makes it difficult to create wrinkles of sufficient height in the heat-shrinkable tape, and the gap between the housing and the capacitor element cannot be fully filled. Therefore, the capacitor element is not stable within the housing, and the impact resistance and vibration resistance of the electrolytic capacitor cannot be fully improved.

[0006] The present invention has been made in view of the above-mentioned problems, and specifically aims to provide an impact-resistant tape that can protect elements housed in a housing from external impacts and vibrations. [Means for solving the problem]

[0007] The present invention provides the following impact-resistant tape. [1] An impact-resistant tape comprising a shrink film having a maximum shrink force of 450 mN or more and a buffer film arranged on one side of the shrink film, the maximum shrink force of which is smaller than that of the shrink film and the thickness of which is 30 μm or more, wherein the shrink film and the buffer film are joined at a plurality of spaced apart dot-like and / or linear joints. [2] The impact-resistant tape according to [1], wherein when the shrink film and the buffer film are each cut into 50 mm squares, immersed in 10 mL of ethylene glycol, and heated at 140°C for 48 hours, the volume change rate before and after heating is within ±10%. [3] The impact-resistant tape according to [1] or [2], wherein the shrink film is a stretched film containing polyphenylene sulfide and / or cycloolefin polymer. [4] The impact-resistant tape according to any one of [1] to [3], further comprising a pressure-sensitive adhesive layer disposed on the other surface of the shrinkable film. [5] The impact-resistant tape according to [4], wherein the thickness of the pressure-sensitive adhesive layer is 3 μm or more and 100 μm or less. [Effects of the Invention]

[0008] The shock-resistant tape of the present invention can protect elements housed in a housing from external vibrations and shocks. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1A is a plan view of an impact-resistant tape according to one embodiment of the present invention, and FIG. 1B is a cross-sectional view taken along line AA in FIG. 1A. [Figure 2] FIG. 2A is a schematic diagram of an impact-resistant tape according to one embodiment of the present invention when used in an electrolytic capacitor; FIG. 2B is a partially enlarged cross-sectional view taken along line BB in FIG. 2A, showing the state of the electrolytic capacitor before heat treatment; and FIG. 2C is a partially enlarged cross-sectional view taken along line BB in FIG. 2A, showing the state of the electrolytic capacitor after heat treatment. DETAILED DESCRIPTION OF THE INVENTION

[0010] The impact-resistant tape of the present invention is a tape that is attached to or wrapped around the surface of an element that is housed in a housing and used. The impact-resistant tape is used to restrict movement of the element within the housing and to prevent collisions between the element and the housing. Hereinafter, an example will be described in which the impact-resistant tape is used as a member for protecting a capacitor element of an electrolytic capacitor, but the impact-resistant tape of the present invention is not limited to use in electrolytic capacitors.

[0011] FIG. 1A shows a plan view of an impact-resistant tape 10 according to one embodiment of the present invention. FIG. 1B shows a cross-sectional view taken along line AA in FIG. 1A. FIG. 2A shows a perspective view of an electrolytic capacitor 20 using the impact-resistant tape 10. In the electrolytic capacitor 20, a capacitor element 22 to which the impact-resistant tape 10 is attached is housed in a housing 24. FIGS. 2B and 2C show partially enlarged cross-sectional views taken along line BB in FIG. 2A. Note that FIG. 2B shows the electrolytic capacitor 20 in a state before heating, while FIG. 2C shows the electrolytic capacitor 20 in a state after heating. Note that in FIGS. 2A to 2C, the housing 24 is shown as a transparent member, indicated by a dashed line, to illustrate the internal state of the electrolytic capacitor 20.

[0012] 1B and 2B, impact-resistant tape 10 of this embodiment has shrink film 12 with a maximum contractile force of 450 mN or more, and buffer film 14 with a thickness of 30 μm or more and a maximum contractile force smaller than that of shrink film 12, which is arranged on one side of shrink film 12. In impact-resistant tape 10, as shown in FIG. 1A, shrink film 12 and buffer film 14 are joined at a plurality of joining portions 16 arranged with gaps between them.

[0013] The impact-resistant tape 10 is used by being attached to the capacitor element 22 via an adhesive or adhesive layer (not shown) so that the shrink film 12 side faces the capacitor element 22 (see FIG. 2A). Furthermore, before being heated, that is, before or when the impact-resistant tape 10 is attached to the capacitor element 22, and also when the impact-resistant tape 10 is attached to the capacitor element 22 and then housed in the housing 24, the shrink film 12 and the buffer film 14 are positioned so that they are in close contact with each other without any gaps (see FIGS. 1B and 2B). The close contact between the shrink film 12 and the buffer film 14 makes it easier to house the capacitor element 22 with the impact-resistant tape 10 attached in the housing 24.

[0014] After the impact-resistant tape 10 and the capacitor element 22 are housed in the housing 24, the electrolytic capacitor 20 (impact-resistant tape 10) is heated, causing the shrink film 12 to shrink. As a result, the spacing between the bonded portions 16 narrows, as shown in FIG. 2C . At this time, the buffer film 14 has a smaller maximum contraction force than the shrink film 12 and rises without following the shrinkage of the shrink film 12. A gap then forms between the shrink film 12 and the buffer film 14, causing wrinkles in the buffer film 14. In this embodiment, wrinkles are formed by the excess buffer film 14 between two adjacent bonded portions 16, so the position of the wrinkles can be controlled by adjusting the position of the bonded portions 16. Furthermore, the height of the wrinkles can be adjusted by adjusting the spacing between the bonded portions 16 and the degree of shrinkage of the shrink film 12. In other words, the impact-resistant tape 10 of this embodiment allows wrinkles of a desired height to be formed in a desired position around the capacitor element 22. Furthermore, when such wrinkles occur, the outer diameter of the member (hereinafter also referred to as the "joint member") that wraps the shock-resistant tape 10 around the capacitor element 22 increases, making it difficult for the joint member to move within the housing 24. Furthermore, according to the shock-resistant tape 10 of this embodiment, external shocks and vibrations can be absorbed by the elasticity of the buffer film 14 and the gap that occurs between the buffer film 14 and the shrink film 12. Therefore, external vibrations and shocks are not easily transmitted to the capacitor element 22, and the capacitor element 22 can be reliably protected.

[0015] As a result of extensive research, the inventors have found that in order to sufficiently increase the diameter of the connecting member, it is extremely important to combine a shrink film 12 having a maximum shrink force of 450 mN or more with a buffer film 14 having a thickness of 30 μm or more, as will be described in detail in the Examples below. The reason for this is unclear, but is thought to be as follows: If the maximum shrink force of the shrink film 12 is 450 mN or more, the shrink amount of the shrink film 12 increases, making it easier to create a sufficient gap between the shrink film 12 and the buffer film 14. Furthermore, if the thickness of the buffer film 14 is 30 μm or more, the buffer film 14 is less likely to be crushed by its own weight, making it easier for individual wrinkles to form between the joints 16. Therefore, it is thought that the outer diameter of the capacitor element 22 (connecting member) to which the impact-resistant tape 10 is attached increases. Each component of the impact-resistant tape 10 of this embodiment will be described in detail below.

[0016] (1) Shrink film The shrink film 12 of this embodiment may be any film that can be shrunk by heat and has a maximum shrinkage force of 450 mN or more. The direction in which the shrink film 12 has a maximum shrinkage force of 450 mN or more may be the MD direction (the machine direction when the film is produced) of the shrink film 12, the TD direction (the direction perpendicular to the machine direction when the film is produced), or any other direction. Furthermore, the maximum shrinkage force of the shrink film 12 in multiple directions may be 450 mN or more.

[0017] Here, the term "maximum shrinkage force" in this specification refers to the maximum shrinkage force exhibited by the shrink film 12 when the shrink film 12 is heated using a thermomechanical analyzer (TMA). The maximum shrinkage force is the maximum value of the shrinkage force measured in accordance with JIS K 7197:1991.

[0018] During measurement, the shrinkage force is measured in the direction in which the shrink film 12 shrinks the most (hereinafter also referred to as the "maximum shrinkage direction"). If the maximum shrinkage direction of the shrink film 12 is unknown, the shrinkage force is measured in multiple directions to identify the maximum shrinkage direction. Then, the maximum shrinkage force is identified for that maximum shrinkage direction.

[0019] When the shrink film 12 is heated for 20 minutes at a temperature not lower than its glass transition temperature (Tg) + 10°C and not higher than Tg + 30°C, the shrinkage percentage in the maximum shrinkage direction is preferably not lower than 30% and not higher than 80%, and more preferably not lower than 50% and not higher than 80%. If the shrinkage percentage when heated for 20 minutes at the above temperature is within this range, the individual wrinkles that occur when the buffer film 14 is heated tend to become larger. The shrinkage percentage is measured as follows: The length of the shrink film 12 in the maximum shrinkage direction before heating (25°C) is measured. Next, the shrink film 12 is heated at the above temperature for 20 minutes, and the length in the same direction after heating is measured. The ratio of the shrink length to the length before heating, i.e., {(length before heating - length after heating) / length before heating x 100} is calculated, and this is the shrinkage percentage.

[0020] Here, there are no particular limitations on the method for controlling the maximum shrinkage force of the shrink film 12 in the maximum shrinkage direction to 450 mN or more. One example is a method in which the shrink film is made into a uniaxially stretched film. Normally, when a film is stretched in a specific direction, the stretched direction becomes the maximum shrinkage direction. Furthermore, the greater the stretching ratio, the greater the maximum shrinkage force. Therefore, if the shrink film 12 is made into a uniaxially stretched film, it is possible to easily adjust the maximum shrinkage direction and maximum shrinkage force by changing the stretching direction and stretching ratio. When the shrink film 12 is made into a uniaxially stretched film, the stretching ratio is appropriately selected according to the desired maximum shrinkage force, and is usually preferably 1.5 times or more and 3.0 times or less, and more preferably 2.0 times or more and 2.5 times or less. However, the shrink film 12 is not limited to a uniaxially stretched film, and a biaxially stretched film or the like may also be used.

[0021] The thickness of the shrink film 12 is not particularly limited and is selected appropriately depending on the desired thickness of the impact-resistant tape 10, but is preferably 20 μm or more and 80 μm or less, and more preferably 30 μm or more and 50 μm or less. When the thickness of the shrink film 12 is within this range, the strength of the shrink film 12 tends to be high.

[0022] Here, there are no particular restrictions on the type of resin that constitutes the shrink film 12, and it is selected appropriately depending on the application. When the impact-resistant tape 10 is used for an electrolytic capacitor as in this embodiment, it is preferable that the shrink film 12 has excellent heat resistance and chemical resistance.

[0023] Specifically, when a sample of shrink film 12 cut into a 50 mm square is immersed in 10 mL of ethylene glycol and heated at 180°C for 48 hours, the volume change rate before and after heating, i.e., {(volume after heating - volume before heating) / volume before heating x 100} preferably falls within ±10%. If the volume change rate is within this range, shrink film 12 is less likely to deteriorate due to heat or the electrolyte when shrinking shrink film 12 or when electrolytic capacitor 20 is used, and its performance is less likely to decrease.

[0024] The material constituting the shrink film 12 is not particularly limited, but from the viewpoint of heat resistance and chemical resistance, it is preferable that it contains at least one of polyphenylene sulfide and cycloolefin polymer, and it may contain both of these.

[0025] The polyphenylene sulfide may have a structure in which p-phenylene groups and sulfur atoms are alternately bonded, and may partially contain structures other than those described above, as long as the purpose and effect of this embodiment are not impaired. The polyphenylene sulfide may be a commercially available product. Examples of commercially available products include TORELINA A900 (manufactured by Toray Industries, Inc.), FORTRON KPS (e.g., FORTRON KPS W-312, manufactured by Kureha Corporation), B-06P (manufactured by Tosoh Corporation), ASPEX-PPS (manufactured by Aspect Corporation), DSP-B100, PRIMEF 4010, PRIMEF 7002, and PRIMEF 7010 (manufactured by DIC Corporation).

[0026] The cycloolefin polymer may be any polymer having a cycloolefin structure in the main chain. Examples of such cycloolefin polymers include ring-opening polymers of cycloolefin monomers, addition polymers of cycloolefin monomers, and copolymers of cycloolefin monomers with linear olefins. Examples of the cycloolefin structure of the cycloolefin polymer include monocyclic rings such as cyclobutene, cyclopentene, cyclooctene, cyclododecene, and 1,5-cyclooctadiene; bicyclic rings such as 2-norbornene and norbornadiene; tricyclic rings such as dicyclopentadiene and dihydrodicyclopentadiene; tetracyclic rings such as tetracyclododecene, ethylidenetetracyclododecene, and phenyltetracyclododecene; pentacyclic rings such as tricyclopentadiene; and heptacyclic rings such as tetracyclopentadiene.

[0027] The cycloolefin polymer may be a commercially available product, and examples thereof include the Zeonex series (e.g., Zeonex 690R, Zeonex T62R, etc.) and the Zeonor series (Zeon Corporation), the Sumilite series (Sumitomo Bakelite Co., Ltd.), the Arton series (JSR Corporation), the Apel series (Mitsui Chemicals, Inc.), Topas (Ticona), and the Optretz series (Hitachi Chemical Co., Ltd.).

[0028] The shrink film 12 of this embodiment may contain resins (other resins) and components other than polyphenylene sulfide and cycloolefin polymer, as long as the purpose and effects of this embodiment are not impaired. Examples of other components include plasticizers, stabilizers, antioxidants, surfactants, and pigments. The shrink film 12 may contain only one of these, or two or more. However, the total amount of other resins and other components is preferably 10% by mass or less of the total amount of the shrink film 12.

[0029] (2) Buffer film The buffer film 14 may be any film having a maximum shrinkage force smaller than that of the shrink film 12 and a thickness of 30 μm or more. In this specification, the phrase "the maximum shrinkage force of the buffer film 14 is smaller than that of the shrink film 12" means that when the maximum shrinkage forces of the buffer film 14 are compared in a direction parallel to the maximum shrinkage direction of the shrink film 12, the maximum shrinkage force of the buffer film 14 is smaller than the maximum shrinkage force of the shrink film 12 in that direction. In this embodiment, it is preferable that the maximum shrinkage force of the buffer film 14 is smaller than the maximum shrinkage force of the shrink film 12 by 400 mN or more.

[0030] Here, the buffer film may be a stretched film, but it is preferable that it is an unstretched film from the viewpoint that the maximum shrinkage force in each direction can be reduced.

[0031] Furthermore, when the buffer film 14 is heated for 20 minutes at a temperature that is at least 10°C above the glass transition temperature (Tg) of the shrink film 12 and not more than 30°C above Tg, the shrinkage percentage in the maximum shrinkage direction is preferably 30% or less, and more preferably 10% or less. If the shrinkage percentage when the buffer film 14 is heated for 20 minutes at the above temperature is within this range, the difference in the amount of shrinkage between the buffer film 14 and the shrink film 12 can be made even greater when the shrink film 12 is shrunk, and as described above, large wrinkles are more likely to occur in the buffer film 14. The method for measuring the shrinkage percentage of the buffer film 14 is the same as the method for measuring the shrinkage percentage of the shrink film 12.

[0032] The thickness of buffer film 14 is preferably 30 μm or more and 80 μm or less, and more preferably 40 μm or more and 60 μm or less. If the thickness of buffer film 14 is 30 μm or more, buffer film 14 will have an appropriate hardness, and as described above, large wrinkles will easily occur in buffer film 14 when shock-resistant tape 10 is heated. In addition, buffer film 14 will be less likely to be crushed by external impacts, etc., and capacitor element 22 can be protected.

[0033] Here, the type of resin constituting the buffer film 14 is not particularly limited and may be appropriately selected depending on the application. When the impact-resistant tape 10 is used for an electrolytic capacitor as in this embodiment, it is preferable that the buffer film 14 has excellent heat resistance and chemical resistance.

[0034] Specifically, when a sample of the buffer film 14 cut into a 50 mm square is immersed in 10 mL of ethylene glycol and heated at 180°C for 48 hours, the volume change rate before and after heating, i.e., {(volume after heating - volume before heating) / volume before heating x 100}, preferably falls within ±10%. If the volume change rate is within this range, the buffer film 14 is less likely to be deteriorated by heat or the electrolyte when the shrink film 12 is thermally shrunk or when the electrolytic capacitor 20 is used, and its performance is less likely to decrease.

[0035] The material constituting the buffer film 14 is not particularly limited, but from the viewpoint of heat resistance and chemical resistance, it is preferable that the buffer film 14 contains at least one of polyphenylene sulfide and cycloolefin polymer, and it may contain both. Furthermore, the buffer film 14 may contain the same resin as the shrink film 12 described above, or a different resin. However, if the buffer film 14 contains the same resin, the constituent resins of the buffer film 14 and the shrink film 12 are more likely to be compatible with each other when the joint 16 is formed by heat welding or the like, and the joint strength is likely to be high. Note that the preferred polyphenylene sulfide and preferred cycloolefin polymer are the same as those described for the shrink film 12 above.

[0036] Here, the buffer film 14 preferably contains an elastomer in addition to the polyphenylene sulfide and cycloolefin polymer. The inclusion of an elastomer in addition to the polyphenylene sulfide and cycloolefin polymer improves the slipperiness of the surface of the buffer film 14, facilitating lamination of the buffer film 14 and the shrink film 12 during the manufacture of the impact-resistant tape 10. The type of elastomer is not particularly limited as long as it has good compatibility with the polyphenylene sulfide and cycloolefin polymer. Examples of elastomers include styrene-based, olefin-based, ester-based, urethane-based, amide-based, PVC (polyvinyl chloride)-based, and acrylic-based elastomers. The buffer film 14 may contain only one type of elastomer, or two or more types.

[0037] Here, the ratio of the total amount of polyphenylene sulfide and cycloolefin polymer to the total amount of elastomer contained in the buffer film 14 is preferably 99.5:0.5 to 80:20, and more preferably 99:1 to 90:10. When the amount of elastomer is within this range, the above-mentioned effect of addition is easily obtained.

[0038] The buffer film 14 of this embodiment may contain resins other than polyphenylene sulfide, cycloolefin polymer, and elastomer (other resins) and other components, as long as the purpose and effect of this embodiment are not impaired. Examples of other components include plasticizers, stabilizers, antioxidants, surfactants, and pigments. The buffer film 14 may contain only one of these, or two or more of them. However, the total amount of other resins and other components is preferably 10% by mass or less of the total amount of the buffer film 14.

[0039] (3)Joint part The bonded portion 16 is the region where the shrink film 12 and the buffer film 14 are bonded together. The impact-resistant tape 10 may have a plurality of dot-like and / or linear bonded portions 16 arranged with gaps between them, and in this embodiment, a plurality of circular (dot-like) bonded portions 16 are regularly arranged with gaps between them.

[0040] Here, there are no particular limitations on the method for joining the shrink film 12 and the buffer film 14 at the joint 16. For example, the joint 16 may be an area where the shrink film 12 and the buffer film 14 are welded by a known thermal welding method (heat sealing, impulse sealing, ultrasonic sealing, laser welding, etc.), an area where the shrink film 12 and the buffer film 14 are joined by an adhesive or the like, or an area where the shrink film 12 and the buffer film 14 are joined by using a fastener or the like.

[0041] The shape of each joint 16 is not limited and may be dot-like, linear, or a combination thereof. When the joints 16 are dot-like, each point may have any shape, such as a circle, ellipse, ring, triangle, square, polygon, or X-shape. When the joints 16 are linear, each line may have any shape, such as a straight line, curved line, wavy line, zigzag line, or dashed line. The shapes of the multiple joints 16 may be the same or different. Furthermore, the sizes of the multiple joints 16 may be the same or different.

[0042] Furthermore, the size of each bond 16 is not particularly limited as long as sufficient bond strength is obtained. For example, when the bond 16 is dot-shaped, the maximum diameter of each bond 16 is preferably 1.0 mm to 2.0 mm, more preferably 1.2 mm to 1.8 mm, and even more preferably 1.4 mm to 1.6 mm. When the bond 16 is linear, the width of each line is preferably 0.5 mm to 5 mm, preferably 1.0 mm to 4 mm, and more preferably 1.5 mm to 3 mm.

[0043] Here, the joints 16 may be randomly arranged on the impact-resistant tape 10, but are preferably arranged regularly. Regularly arranging the joints 16 facilitates regular wrinkles in the buffer film 14. Furthermore, particularly when the joints 16 are arranged regularly along the maximum shrinkage direction of the shrink film 12, wrinkles of a desired height are more easily formed in the buffer film 14 at regular intervals. For example, in FIG. 1A , in which the joints 16 are arranged in a grid pattern, if the MD direction is the maximum shrinkage direction of the shrink film 12, when the impact-resistant tape 10 is heated, the shrink film 12 shrinks significantly in the MD direction. This causes the buffer film 14 to lift between two adjacent joints 16 in the MD direction, resulting in regular wrinkles parallel to the TD direction. Furthermore, in FIG. 1A , if the TD direction is the maximum shrinkage direction of the shrink film 12, regular wrinkles parallel to the MD direction will form. In this way, by adjusting the direction of maximum shrinkage of the shrink film 12 and arranging the joints 16 regularly, wrinkles can be generated regularly in the buffer film 14 in the desired direction.

[0044] Here, the spacing between adjacent joints 16 along the maximum shrinkage direction of the shrink film 12 is appropriately selected depending on the application of the impact-resistant tape 10, the thickness of the buffer film 14, etc. When the impact-resistant tape 10 is used in an electrolytic capacitor 20 as in this embodiment, the spacing between adjacent joints 16 is preferably 3 mm or more and 20 mm or less, more preferably 5 mm or more and 15 mm or less, and even more preferably 5 mm or more and 10 mm or less. When the spacing between adjacent joints 16 is within this range, wrinkles of the desired height are easily formed in the buffer film 14. Furthermore, the spacing between adjacent joints 16 can be appropriately adjusted depending on the application.

[0045] (4) Other The impact-resistant tape 10 of this embodiment may have a configuration other than the above-mentioned shrink film 12, buffer film 14, and joint portion. For example, the shrink film 12 may have an adhesive layer (not shown) on the surface opposite to the buffer film 14. If the impact-resistant tape 10 has an adhesive layer, it becomes possible to easily attach the impact-resistant tape 10 to the capacitor element 22.

[0046] Examples of adhesives constituting the adhesive layer include acrylic, urethane, and rubber-based resin adhesives. The adhesive layer may contain only one of these, or two or more. The thickness of the adhesive layer is preferably 3 μm to 100 μm, more preferably 5 μm to 50 μm, and even more preferably 14 μm to 45 μm, with the upper limit being particularly preferably 30 μm or less. If the thickness of the adhesive layer is greater than 100 μm, it becomes difficult to control the film thickness during coating.

[0047] The adhesive strength of the adhesive layer is preferably 1 N / 15 mm or more and 20 N / 15 mm or less, and more preferably 2 N / 15 mm or more and 10 N / 15 mm or less. The adhesive strength can be determined, for example, by measuring peel strength. Specifically, it can be determined by fixing shrink film 12 to capacitor element 22 via the adhesive layer and then measuring the stress generated when peeling it from capacitor element 22 at a constant speed. If the adhesive strength of the adhesive layer is within this range, shrink film 12 will be less likely to peel from the surface of capacitor element 22 when it shrinks.

[0048] Here, the impact-resistant tape 10 does not necessarily have to have the adhesive layer. For example, when using the impact-resistant tape 10, an adhesive may be applied to a desired area of ​​the shrink film 12 and then attached to the capacitor element 22. Examples of adhesives in this case include acrylic, urethane, and rubber-based resin adhesives. In this case, the thickness of the adhesive is preferably 3 μm or more and 100 μm or less, and more preferably 3 μm or more and 30 μm or less. Furthermore, the adhesive strength of the adhesive is preferably the same as that of the adhesive layer.

[0049] (5) Manufacturing method of impact-resistant tape The method for producing the impact-resistant tape 10 of this embodiment is not particularly limited, but it can be produced, for example, by the following method, which can be modified as appropriate to suit the desired shape and performance of the impact-resistant tape 10.

[0050] First, the shrink film 12 and the buffer film 14 are prepared. Then, the buffer film 14 is superimposed on one side of the shrink film 12, and the joint 16 is formed at a predetermined position. As mentioned above, there are no particular limitations on the method for forming the joint 16, and it may be heat welding, adhesion with an adhesive, or the like. When the joint 16 is formed by heat welding, the heat welding may be performed from the shrink film 12 side or the buffer film 14 side.

[0051] If necessary, an adhesive layer may be formed by a conventional method on the surface of the shrink film 12 opposite to the buffer film 14.

[0052] (6)Applications As described above, the impact-resistant tape 10 of this embodiment is very useful as a member for protecting the capacitor element 22 of the electrolytic capacitor 20. When using the impact-resistant tape 10 in the electrolytic capacitor 20, the impact-resistant tape 10 is first attached to the capacitor element 22, and the electrolytic capacitor 20 is then housed in the housing 24. At this time, the manner in which the impact-resistant tape 10 is attached to the capacitor element 22 is appropriately selected depending on the shape, type, dimensions, etc. of the electrolytic capacitor 20. For example, the impact-resistant tape may be wrapped around the capacitor element 22 one or more times, or the impact-resistant tape may be attached partially to only a desired region of the capacitor element 22.

[0053] After the capacitor element 22 is housed in the housing 24, an electrolyte is poured into the housing 24 and the housing 24 is sealed. The type of electrolyte that can be used is not particularly limited as long as it does not impair the objectives and effects of this embodiment; any electrolyte used in known electrolytic capacitors can be used. The housing 24 is then sealed, and the housing 24 is heated from the outside at a predetermined temperature for a predetermined time. The heating temperature is selected based on the shrink temperature of the shrink film; typically, it is preferably at least Tg + 10°C and at most Tg + 30°C. The heating time is preferably 10 to 120 minutes, more preferably 20 to 60 minutes. By setting the heating temperature and heating time within the above ranges, the shrink film 12 shrinks, resulting in the desired wrinkles in the buffer film 14. The heating method for the electrolytic capacitor is not particularly limited; for example, a known method, such as heating in an oven, can be used.

[0054] However, the use of the above-mentioned impact-resistant tape is not limited to electrolytic capacitors, and it can also be used to protect electrical storage devices such as electric double layer capacitors and high heat-resistant lithium ion capacitors from impact and vibration. When the impact-resistant tape 10 is used for these purposes, the heating temperature and heating time for shrinking the shrink film 12 and creating wrinkles in the buffer film 14 are the same as those described above. [Example]

[0055] Specific examples of the present invention will be described below together with comparative examples, but the present invention is not limited to these.

[0056] [Examples 1-1 to 1-6 and Comparative Examples 1-1 to 1-6] (1) Preparation of impact-resistant tape Four types of uniaxially stretched PPS films (Fortron KPS W-312P, glass transition temperature: 93°C) were prepared as shrink films. Specifically, a 20 μm thick film stretched 2 times in the MD direction, a 50 μm thick film stretched 2 times in the MD direction, a 15 μm thick film stretched 2.5 times in the MD direction, and a 40 μm thick film stretched 2.5 times in the MD direction were prepared. The dimensions of each shrink film were 80 mm in the MD direction and 20 mm in the TD direction.

[0057] Three types of unstretched buffer films (20 μm, 40 μm, and 60 μm thick) containing PPS (Fortron KPS W-312P, manufactured by Kureha Corporation) and hydrogenated styrene-based thermoplastic elastomer (SEPTON 8007L, manufactured by Kuraray Co., Ltd.) in a mass ratio of 99:1 were prepared. Each buffer film measured 80 mm × 20 mm.

[0058] The shrink film and buffer film were combined and stacked as shown in Table 1 below. Then, the film was placed on an iron plate with the shrink film facing downwards, and a soldering iron set to a temperature of 320°C was used to heat-melt the two films at 10 mm intervals in both the TD and MD directions to form joints.

[0059] (Measurement of physical properties of each film) The physical properties of the shrink film and the buffer film used in the preparation of the above impact-resistant tape were measured as follows.

[0060] Maximum contractile force The maximum shrinkage force in the MD direction of each shrink film and each buffer film was measured using a thermomechanical analyzer (TMA) in accordance with JIS K 7197: 1991. The results are shown in Table 1.

[0061] Shrinkage rate The shrinkage rate in the MD direction when each shrink film was heated at 110°C for 20 minutes was determined, i.e., {(length in the MD direction before heating (25°C) - length in the MD direction after heating) / length in the MD direction before heating x 100}. The results are shown in Table 1.

[0062] Heat and chemical resistance Each shrink film (PPS film) was cut into a 50mm x 50mm square, immersed in 10mL of ethylene glycol, and heated at 140°C for 48 hours. The volume change rate before and after heating, i.e., {(volume after heating - volume before heating) / volume before heating x 100}, was then determined. The results were within ±10% range, regardless of thickness.

[0063] (2) Making a capacitor A wound capacitor element (manufactured by Nippon Chemi-Con Corporation) with an outer diameter of 16.0 mm and a height of 30.0 mm was prepared. A 7-10 μm thick acrylic emulsion adhesive (Orivine BPW6166, manufactured by Toyochem Co., Ltd.) was applied to the shrink film of each impact-resistant tape prepared above to form an adhesive layer. The impact-resistant tape was then attached to the stop tape on the periphery of the capacitor element via the adhesive.

[0064] The capacitor element with the shock-resistant tape attached was placed in an aluminum capacitor cylinder (housing) with an inner diameter of approximately 17.3 mm, immersed in an electrolyte (ethylene glycol), and sealed. The aluminum cylinder with the capacitor element inserted was then placed in a gear oven at 110°C for 20 minutes, removed, and cooled to room temperature.

[0065] [evaluation] The outer diameter of the capacitor element with the shock-resistant tape attached before heating was measured, as well as the outer diameter of the capacitor element with the shock-resistant tape attached after heating. The gap was calculated by subtracting the outer diameter of the element including the attached shock-resistant tape after the test from the inner diameter of the housing. Furthermore, the formation of wrinkles was visually confirmed. The results are shown in Table 1.

[0066] The results were evaluated according to the following criteria, with △ and above being in the range where there is no problem in practical use. ○: Wrinkles in contact with the wall of the aluminum cylinder were observed almost evenly around the entire circumference of the element. △: Wrinkles were observed where the aluminum tube wall was in contact, but the wrinkles were only formed partially. ×: No wrinkles were observed, or the wrinkles that were formed did not contact the wall of the aluminum tube.

[0067] [result] [Table 1]

[0068] As shown in Table 1 above, impact-resistant tapes that combined a shrink film with a maximum shrinkage force of 450 mN or more with a buffer film with a smaller shrinkage rate than the shrink film and a thickness of 30 μm or more all had small gaps between the capacitor element and the housing, and were evaluated as good (Examples 1-1 to 1-6). In contrast, when the maximum shrinkage amount of the shrink film was less than 450 mN (Comparative Examples 1-1 to 1-3) or when the buffer film was less than 30 μm thick (Comparative Examples 1-1, 1-4 to 1-6), the gap was not sufficiently small.

[0069] [Examples 2-1, 2-2, and Comparative Example 2-1] (1) Preparation of impact-resistant tape Impact-resistant tapes were produced in the same manner as in Example 1-1, etc., except that the shrink film and buffer film combinations shown in Table 2 were used, and joints were formed by heat-melting two films at a 5 mm pitch in each of the TD and MD directions. The shrink film was a film made of PPS (Fortron KPS W-312P, manufactured by Kureha Corporation) stretched twice in the MD direction, and the buffer film was an unstretched film containing PPS (Fortron KPS W-312P, manufactured by Kureha Corporation) and a hydrogenated styrene-based thermoplastic elastomer (SEPTON 8007L, manufactured by Kuraray Co., Ltd.) in a mass ratio of 99:1.

[0070] Table 2 also shows the maximum shrinkage force in the MD direction of the shrink film and each buffer film, and the shrinkage percentage when the shrink film was heated at 110°C for 20 minutes. These measurements were made using the same method as above.

[0071] (2) Making a capacitor A wound capacitor element (manufactured by Nippon Chemi-Con Corporation) with an outer diameter of 16.0 mm and a height of 30.0 mm was prepared. A 7-10 μm thick acrylic emulsion adhesive (Orivine BPW6166, manufactured by Toyochem Co., Ltd.) was applied to the shrink film of each impact-resistant tape prepared above. The impact-resistant tape was then attached to the stop tape on the outer periphery of the capacitor element via the adhesive. The aluminum cylinder with the capacitor element inserted was then placed in a gear oven at 110°C for 20 minutes, removed, and cooled to room temperature.

[0072] [evaluation] As in Example 1-1, the outer diameter of the capacitor element after the impact-resistant tape was attached before heating was measured, and the outer diameter of the capacitor element after the impact-resistant tape was attached after heating was measured. The gap was calculated by subtracting the outer diameter of the element including the attached impact-resistant tape after the test from the inner diameter of the housing. Furthermore, the location of wrinkle formation was visually confirmed. The evaluation criteria were the same as above. The results are shown in Table 2. For comparison, Table 2 also shows the results of Comparative Example 1-4, Example 1-1, and Example 1-2.

[0073] [result] [Table 2]

[0074] As shown in Table 2 above, in impact-resistant tapes that combine a shrink film with a maximum shrinkage force of 450 mN or more and a buffer film with a smaller shrinkage rate than the shrink film and a thickness of 30 μm or more, the gap between the capacitor element and the housing was small even when the joint pitch was changed, and the tapes were evaluated as good (Examples 2-1 and 2-2). In contrast, when the thickness of the buffer film was less than 30 μm (Comparative Example 2-1), the gap was not sufficiently small.

[0075] [Examples 3-1 to 3-3] (1) Preparation of impact-resistant tape A 45 μm thick film containing COP (ZEONEX690R, manufactured by Zeon Corporation, glass transition temperature: 136°C) and stretched twice in the MD direction was prepared as a shrink film. Another 45 μm thick film containing COP (ZEONEXT62R, manufactured by Zeon Corporation, glass transition temperature: 154°C) and stretched twice in the MD direction was prepared. The dimensions of both shrink films were 80 mm in the MD direction and 20 mm in the TD direction.

[0076] As buffer films, two types of unstretched films containing COP (ZEONEX690R, manufactured by Zeon Corporation) with thicknesses of 50 μm and 70 μm, and a 50 μm unstretched film containing COP (ZEONEXT62R, manufactured by Zeon Corporation) were prepared. The dimensions of each buffer film were 80 mm × 20 mm.

[0077] Impact-resistant tapes were produced in the same manner as in Example 1-1, etc., except that the shrink film and buffer film combinations shown in Table 3 were used and two films were heat-melted at a pitch of 10 mm in each of the TD and MD directions to form joints.

[0078] (Measurement of physical properties of each film) The physical properties of the shrink film and the buffer film used in the preparation of the above impact-resistant tape were measured as follows.

[0079] Maximum contractile force The maximum shrinkage force in the MD direction of the shrink film and each buffer film was measured using a thermomechanical analyzer (TMA) in accordance with JIS K 7197: 1991. The results are shown in Table 3.

[0080] Shrinkage rate The shrinkage rate in the MD direction when the shrink film was heated at 1.50°C for 20 minutes (Examples 3-1 and 3-2) or at 170°C for 20 minutes (Example 3-3) was determined, i.e., {(length in the MD direction before heating (25°C) - length in the MD direction after heating) / length in the MD direction before heating x 100}. The results are shown in Table 3.

[0081] Heat and chemical resistance A 50mm x 50mm square was cut out of shrink film (COP film), immersed in 10mL of ethylene glycol, and heated at 140°C for 48 hours. The volume change rate before and after heating, i.e., {(volume after heating - volume before heating) / volume before heating x 100}, was determined and found to be 2%.

[0082] (2) Making a capacitor A wound capacitor element (manufactured by Nippon Chemi-Con Corporation) with an outer diameter of 16.0 mm and a height of 30.0 mm was prepared. A 7-10 μm thick acrylic emulsion adhesive (Orivine BPW6166, manufactured by Toyochem Co., Ltd.) was applied to the shrink film of each impact-resistant tape prepared above. The impact-resistant tape was then attached to the stop tape on the outer periphery of the capacitor element via the adhesive. The aluminum cylinder with the capacitor element inserted was then placed in a gear oven at 150°C for 20 minutes (Examples 3-1 and 3-2) or in a gear oven at 170°C for 20 minutes (Example 3-3), then removed and cooled to room temperature.

[0083] [evaluation] As in Example 1-1, the outer diameter of the capacitor element after the impact-resistant tape was attached before heating and the outer diameter of the capacitor element after the impact-resistant tape was attached after heating were measured. The gap was calculated by subtracting the outer diameter of the element after the impact-resistant tape was attached after the test from the inner diameter of the housing. Furthermore, the location of wrinkle formation was visually confirmed. The evaluation criteria were the same as above. The results are shown in Table 3.

[0084] [result] [Table 3]

[0085] As shown in Table 3 above, impact-resistant tapes that combine a shrink film with a maximum shrink force of 450 mN or more and a buffer film with a smaller shrink rate than the shrink film and a thickness of 30 μm or more had a smaller gap between the capacitor element and the housing, and were evaluated as good, even when the type of resin was changed (Examples 3-1 to 3-3).

[0086] [Examples 4-1 and 4-2, and Comparative Example 4-1] (1) Preparation of impact-resistant tape An impact-resistant tape was produced in the same manner as in Example 1-1 shown in Tables 1 and 2. The shrink film was a film made of PPS (Fortron KPS W-312P, manufactured by Kureha Corporation) stretched twice in the MD direction, and the buffer film was an unstretched film containing PPS (Fortron KPS W-312P, manufactured by Kureha Corporation) and a hydrogenated styrene-based thermoplastic elastomer (SEPTON 8007L, manufactured by Kuraray Co., Ltd.) in a mass ratio of 99:1.

[0087] (2) Making a capacitor A wound capacitor element (manufactured by Nippon Chemi-Con Corporation) with an outer diameter of 16.0 mm and a height of 40.0 mm was prepared. An acrylic emulsion adhesive (Orivine BPW6166 manufactured by Toyochem Co., Ltd.) was applied to the shrink film of each of the impact-resistant tapes prepared above to thicknesses of 10 μm and 40 μm. The impact-resistant tape, measuring 80 mm in length in the winding direction and 30 mm in width, was then attached to the stop tape on the outer periphery of the capacitor element. The capacitor element with the shock-resistant tape attached was placed in an aluminum capacitor cylinder (housing) with an inner diameter of approximately 17.3 mm, immersed in an electrolyte (ethylene glycol), and sealed. The aluminum cylinder with the capacitor element inserted was then left to stand in a gear oven at 110°C for 60 minutes, then removed and cooled to room temperature.

[0088] [evaluation] After heating, the capacitors were dropped to apply a drop impact of 4500G, and X-ray observations and electrical characteristics were measured for each impact load. The impact was applied vertically with the capacitor's lead wires placed horizontally on the ground. Electrical characteristics were measured using an LCR meter, and failure was determined when an open or short circuit was confirmed. X-ray observations were performed to check the condition of the internal tabs, and failure was determined when a break was observed. The number of impact loads at which failure was first confirmed through electrical characteristics or X-ray observations was recorded as the number of impact loads at failure. The results are shown in Table 4.

[0089] [result] [Table 4]

[0090] As shown in Table 4 above, capacitors using impact-resistant tape were able to withstand more impact loads before failure compared to capacitors not using impact-resistant tape. Also, the thicker the adhesive applied to attach the impact-resistant tape to the capacitor element, the more impact loads could be sustained before failure such as an open or short circuit was confirmed, demonstrating improved impact resistance. [Industrial Applicability]

[0091] The shock-resistant tape of the present invention can protect elements housed in a housing from external vibrations and shocks, and is therefore extremely useful in the field of manufacturing various electronic components. [Explanation of symbols]

[0092] 10. Shock-resistant tape 12 Shrink film 14 Buffer film 16 Joint 20 electrolytic capacitors 22 Capacitor element 24 cabinets

Claims

1. a shrink film having a maximum shrinkage force of 450 mN or more; a buffer film disposed on one surface of the shrink film, the buffer film having a maximum shrink force smaller than that of the shrink film and a thickness of 30 μm or more; and The shrink film and the buffer film are joined at a plurality of spaced apart dot and / or line joints. Anti-shock tape.

2. The shrink film and the buffer film are each cut into a 50 mm square, immersed in 10 mL of ethylene glycol, and heated at 140°C for 48 hours, and the volume change rate before and after heating is within ±10%. The impact-resistant tape according to claim 1.

3. The shrink film is a stretched film containing polyphenylene sulfide and / or cycloolefin polymer. The impact-resistant tape according to claim 1.

4. Further comprising a pressure-sensitive adhesive layer disposed on the other surface of the shrink film; The impact-resistant tape according to claim 1.

5. The thickness of the pressure-sensitive adhesive layer is 3 μm or more and 100 μm or less. The impact-resistant tape according to claim 4.

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