JP2021054657A - Film wound body - Google Patents

Abstract

To provide a film wound body and a method for producing a film wound body in which a pressure-sensitive adhesive portion having a stable adhesive force even against the surface of the porous film is adhesively fixed to the surface of the porous film so as to be peelable.SOLUTION: The present invention relates to a film wound body composed by winding a long porous film around a winding core, in which an adhesive portion provided at an end of the long porous film is adhesively fixed to a surface of the long porous film so as to be peelable. The adhesive portion comprises: a film base material; and an adhesive layer consisting of a thick film region having a thickness of 5 μm or more and a thin film region having a thickness of less than 5 μm with respect to the reference plane whose plane is estimated by the least-squares method from a shape of a height image of the adhesive layer surface. The area ratio of the thick film region to the entire region of the adhesive layer is 5 to 45%.SELECTED DRAWING: Figure 1

Description

The present invention is a film wound body in which a long porous film is wound around a winding core, and an adhesive portion provided at the end of the long porous film is adhesively fixed to the surface of the long porous film so as to be peelable. The present invention relates to a method for producing a film wound body.

The manufacturing process of a film winding body formed by winding a long porous film used for a separator for a non-aqueous electrolyte secondary battery around a winding core is described in Patent Document 1 and the like, but the most of the film winding body. It is generally practiced to attach and fix the film winding end portion to the film winding body with a tape or a label sticker containing identification information of the film product so that the outer peripheral portion does not collapse (Patent Documents). See 2.).

International Publication No. 2013/084988 Japanese Unexamined Patent Publication No. 2018-037312

In recent years, with the sophistication of characteristics required by customers, a plurality of inspection steps may be provided at the final stage of the manufacturing process of a film wound body to confirm that the product has a predetermined performance. In this case, if the end of the film winding is fixed with tape or the like, the adhesive strength weakens as the tape or the like is applied or peeled off multiple times in each inspection process, and after the inspection process is completed. Even if the tape or the like is attached, the tape may be peeled off during the subsequent transportation or storage, and the film winding body may be unwound.

In order to prevent the film winding body from collapsing, after all the inspection processes are completed, the tape that fixed the film winding end may be peeled off and a new tape may be reattached before packing. It is conceivable, but if the film winding end is fixed with a label sticker containing the identification information of the film product, the wrong label sticker may be manually attached.

As a pressure-sensitive adhesive layer suitable for label seals that are expected to be repeatedly stuck and peeled off, a re-sticking type spherical pressure-sensitive adhesive typified by Post-it is well known. Paper is a typical example of the adherend, and the mechanism of good reattachability is that the adhesive is spherical and the contact area is small just by placing the label sticker on the adherend. Although it does not stick to the body, when pressure is applied from above the label sticker, the spherical adhesive is crushed and the contact area becomes large, so that the label sticker can secure a sufficiently stable adhesive force to the adherend. In addition, when the label sticker is peeled off, the spherical adhesive is peeled off from the adherend while returning to the spherical shape, so that the adhesive layer of the label sticker can maintain almost the initial state and can be reattached multiple times. Become.

However, when the adherend is a porous long film used for a separator for a non-aqueous electrolyte secondary battery or the like, when the label seal is pressure-bonded to the porous film, a plurality of dozens of them are present on the surface of the porous film. When the spherical adhesive permeates the holes on the order of nm and the label seal is peeled off from the porous film, a part of the spherical adhesive remains on the porous film side, and the amount of the spherical adhesive on the adhesive layer side of the label seal increases. It may decrease and the adhesive strength of the label seal may be significantly reduced.

Further, even if the reattachable type spherical adhesive is used, if a large amount of spherical adhesive is present in the adhesive layer of the label seal and the adhesive strength is too high, when the label seal is peeled off from the surface of the porous film, the surface of the porous film and the spherical adhesive are spherical. Since the contact area with the adhesive is large and the adhesive strength is strong, the structure of the porous film itself may be destroyed.

Therefore, an object of the present invention is a method for producing a film wound body or a film wound body in which an adhesive portion having a stable adhesive force on the surface of a porous film is adhesively fixed to the surface of the porous film so as to be peelable. To provide.

In order to solve the above problems, the film winding body according to the present invention is formed by winding a long porous film around a winding core, and an adhesive portion provided at an end portion of the long porous film is formed by the long porous film. A film winder that is adhesively fixed to the film surface so that it can be peeled off.
The adhesive portion has a thick film region having a thickness of 5 μm or more and a thickness of less than 5 μm with respect to a reference plane whose plane is estimated by the least squares method from the shape of the height image of the film base material and the surface of the adhesive layer. It is composed of an adhesive layer composed of a thin film region, and is characterized in that the area ratio of the thick film region to the entire region of the adhesive layer is 5 to 45%.

According to such a film wound body according to the present invention, sufficient adhesive strength of the adhesive portion is secured even after repeated sticking and peeling in each of a plurality of inspection steps, so that high performance without unwinding. A flexible film winder can be provided.

The film wound body of the present invention is preferably used when the long porous film is made of a porous film. When the long porous film is made of a porous film, the adhesive constituting the adhesive layer penetrates into the pores on the surface of the long porous film, and when the adhesive portion is peeled off from the long porous film in the inspection process. The adhesive may move from the adhesive portion to the long porous film side and reduce the adhesive strength. However, in the film wound body of the present invention, the adhesive portion has a thickness of 5 μm or more from the film base material and the reference surface. It is composed of an adhesive layer composed of a thick film region having a thick film region and a thin film region having a thickness of less than 5 μm, and is configured such that the area ratio of the thick film region to the entire region of the adhesive layer is 5 to 45%. Sufficient adhesive strength of the adhesive portion is ensured even after repeated sticking and peeling in each of a plurality of inspection steps.

In the film wound body of the present invention, it is preferable that the adhesive portion contains identification information of the long porous film. Since the adhesive portion of the film wound body of the present invention has sufficient adhesive strength even after repeated sticking and peeling in each of a plurality of inspection steps, a two-dimensional bar code or the like is printed on this portion. It is useful from the viewpoint of product management to give the product identification information of the long porous film.

In the film wound body of the present invention, it is preferable that the pressure-sensitive adhesive layer is made of an acrylic spherical pressure-sensitive adhesive. By using an acrylic spherical adhesive for the adhesive layer, a sea-island structure is formed on the surface of the adhesive layer, and when the label sticker is attached (crimped) to the porous film, the spherical adhesive is crushed and spreads, and the contact area with the porous film is increased. It becomes large and can impart a sufficiently stable adhesive force. Further, when the label seal is peeled off from the porous film, the spherical pressure-sensitive adhesive tries to return to a spherical shape, but since a part of the spherical pressure-sensitive adhesive has penetrated into the pores of the porous film, the spherical pressure-sensitive adhesive is on the porous film side. A part of is migrated. However, although it depends on the conditions of the sticking pressure, the peeling speed, and the peeling angle, if the sea-island structure of the initial adhesive layer is adjusted, a sufficiently stable adhesive force can be given to the adhesive part after repeated sticking and peeling. it can.

On the other hand, in the label seal using an acrylic adhesive that does not contain a spherical adhesive, the surface of the adhesive layer is flat, and when the label seal is attached (crimped) to the porous film, the contact area with the porous film becomes almost the entire surface. Sufficiently stable adhesive strength can be imparted. However, when peeling, cohesive destruction that breaks between the layers of the adhesive layer is unlikely to occur, and the structure of the porous film itself tends to be easily destroyed without peeling at the interface between the surface of the porous film and the adhesive layer. A label sticker with low strength peels off well at the interface between the surface of the porous film and the adhesive layer, but the adhesive strength is too weak to impart sufficient stable adhesive strength to the adhesive portion, so that it is difficult to control the adhesive strength.

In the film wound body of the present invention, it is preferable that the adhesive force of the adhesive portion on the surface of the long porous film is 0.5 to 4.0 N / 15 mm. That is, the adhesive strength is maintained in the range of 0.5 to 4.0 N / 15 mm at the end of the inspection step provided at the final stage of the film wound body manufacturing process, so that the film is being conveyed or stored thereafter. It is possible to effectively prevent the film winding body from collapsing.

According to the film winding body of the present invention, it is possible to provide a high-performance film winding body that does not collapse.

The schematic shape of the film wound body which concerns on one Embodiment of this invention is shown, (a) is a front view, (b) is a side view. It is an observation view by the laser microscope which shows the thick film region and thin film region of the adhesive layer in the film winding body of this invention.

Hereinafter, desirable embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a schematic shape of a film winding body 1 according to an embodiment of the present invention. In the front view 1 (a), in the film winding body 1, a long porous film 2 made of a porous film is wound around a core 3, and a label seal (adhesive portion) 4 is a film end portion. It is attached to the surface of the long porous film 2 so as to straddle 5. Since the back surface of the label sticker 4 is coated with a reattachable acrylic spherical adhesive that can be peeled off and reattached, it can be easily peeled off from the surface of the long porous film 2. Further, as shown in side view 1 (b), a bar code is printed on the label sticker 4, and the width W and the outside can be obtained by reading the bar code of the label sticker 4 with a bar code reader (not shown). The identification information (production lot, etc.) of the film winding body 1 having the diameter D can be grasped. A one-dimensional bar code is printed on the illustrated label sticker 4, but in addition to the two-dimensional bar code, various readable codes may be added to the label sticker 4 by printing or other methods.

The long porous film 2 made of a porous film can be produced by a known method. For example, as described in Patent Document 1, (1) a step of adding a film-forming solvent to polyolefin and then melt-kneading to prepare a polyolefin solution, and (2) extruding the polyolefin solution from a die lip and then cooling. A step of forming a gel-like molded product, (3) a step of stretching the gel-like molded product in at least a uniaxial direction (primary stretching step), (4) a step of removing a film-forming solvent, and (5) a obtained film. A polyolefin microporous film can be produced by a method including (6) a step of stretching the dried film again in at least the uniaxial direction (secondary stretching step). Since the polyolefin microporous film (raw fabric) as produced by the above method has a width of several hundred mm to several thousand mm, a slit (cutting) step for achieving a desired width is usually carried out. After that, it is wound around a winding core 3, and finally, a label sticker 4 or the like is attached to the surface of the long porous film 2 so as to straddle the film end portion 5.

The film winding body 1 produced in this manner is suitably used as a separator for a non-aqueous electrolyte secondary battery, etc., but in recent years, the safety of the battery has been required, and the demand for the battery separator has also increased. Therefore, it is often subjected to a large number of inspection processes before shipping. Then, it is necessary to attach or remove the label sticker 4 each time the inspection process is performed a plurality of times. However, if the adhesive strength weakens as the number of repetitions increases, the label is displayed during transportation or storage of the film winding body 1. The seal 4 may be peeled off and the film may be unwound. Therefore, the adhesive strength of the label seal 4 of the film winding body 1 in the shipping state is controlled based on the area ratio of the thick film region and the thin film region of the adhesive layer provided on the back surface of the label seal 4.

For the measurement of the area ratio, for example, a shape analysis laser microscope VK-X150 (manufactured by KEYENCE CORPORATION) and a multi-file analysis application VK-H1XM (manufactured by KEYENCE CORPORATION) are used to measure the height threshold from the reference plane of the adhesive layer. In a plane of 5 μm, the region where the pressure-sensitive adhesive is present is defined as a “thick film region”, and the other region is defined as a “thin film region”. The area of the thick film region having a thickness of 5 μm or more and the area of the thin film region having a thickness of less than 5 μm with respect to the reference plane whose plane is estimated by the least squares method from the shape of the height image of the surface of the adhesive layer, and the adhesive By configuring the adhesive layer so that the area ratio of the thick film region to the entire region of the layer is 5 to 45%, the adhesive strength of the label seal 4 can be controlled within an appropriate range. Specifically, the initial area ratio is set so that the desired area ratio can be maintained in the shipping state after the expected number of peelings (number of inspection steps) of the label sticker 4 attached to the film winding body. It may be set and an adhesive may be applied to achieve this.

FIG. 2 schematically shows an observation diagram by a laser microscope showing a thick film region 7 and a thin film region of the adhesive layer in the film winding body 1. The region observed as an island shape is the thick film region 7, and the other region observed as a sea shape is the thin film region. In FIG. 2, one of the island-shaped regions is displayed in white as an example of the thick film region 7, but in FIG. 2, a large number of thick film regions 7 can be read in addition to the white display portion. ..

FIG. 2 is an observation of a cross section having a height threshold value of 5 μm from the reference surface of the adhesive layer. Therefore, it can be seen that the pressure-sensitive adhesive is applied to the thick film region 7 with a thickness of 5 μm or more from the reference surface, and the pressure-sensitive adhesive is applied to the thin film region with a thickness of less than 5 μm from the reference surface. In this way, it is possible to observe the abundance ratio of the pressure-sensitive adhesive at a height corresponding to a thickness of 5 μm from the reference plane and adjust the area ratio of the thick film region 7 to the entire region of the pressure-sensitive adhesive layer in the range of 5 to 45%. It has an important significance in controlling the adhesive strength of the label seal 4 within an appropriate range and effectively preventing the film winding body from collapsing. The area ratio of the thick film region 7 can be easily calculated by specifying the thick film region 7 by using an image processing method. Specifically, the adhesive strength of the label seal 4 is preferably 0.5 to 4.0 N / 15 mm with respect to the long porous film 2.

The method for measuring each characteristic of the adhesive layer of the label sticker will be described below.

(1) Adhesive strength of label seal In the measurement of the adhesive strength of the label seal of the film wound body at the time of shipment, a label seal having a size of 15 mm × 100 mm has a thickness of 19.5 μm (vacancy ratio of 45%) and a width of 61. When affixing the 5 mm porous film to the outermost circumference of the film winding body, fix the film winding body, set the film winding body and the label seal in the longitudinal direction, and set the film winding body to the outermost circumference of the film winding body. Along the curved surface, the film was crimped once with a rubber roller weighing 2 kg. The label sticker and the film were cut out from the outermost circumference of the film winding body in a state of being attached, and used as a measurement sample.

For the adhesive strength measurement, a tensile tester (INSTRON, model 5543) was used in an environment of 23 ° C. and 50% RH, and the end of the label seal of the measurement sample was attached to the upper fixing jig (chuck) of the tensile tester. , The end of the porous film on the same side as the end of the label seal fixed to the lower fixing jig was fixed, and the label seal was peeled off from the porous film at a peeling speed of 100 mm / min, and the obtained stroke was obtained. (Distance) -The average value of stresses with a stroke of 20 mm to 70 mm in which the stress of the stress curve was stable was defined as the label seal adhesive force (N / 15 mm).

(2) Area ratio The surface of the adhesive layer of the label sticker is observed with a shape analysis laser microscope VK-X150 (manufactured by KEYENCE CORPORATION) at a magnification of 10 times with an objective lens, an image is captured, and a multi-file analysis application VK-H1XM ( The plane was estimated by the minimum square method from the shape of the height image obtained by KEYENCE CORPORATION), and the reference plane was set. The entire height data was rotated so that the set reference plane was horizontal, and further offset in the height direction so that the height of the reference plane became 0. In the image data thus obtained, the value obtained by dividing the cross-sectional area cut at the height threshold value of 5 μm from the reference plane of the region of 1 mm × 1 mm by the area of the entire region (1 mm ² ) is defined as the area ratio (%). did.

Next, the present invention will be described in more detail with reference to Examples and Comparative Examples.
The film winding body 1 described with reference to FIG. 1 was prepared. At this time, the outer diameter is 200 mm, the inner diameter is 76.4 mm, the width is 63.5 mm, and the core 3 of the material ABS is slit (cut) to have a film thickness of 19.5 μm (vacancy ratio of 45%) and a width of 61.5 mm. The long porous film 2 was obtained by winding the porous film of No. 1 for 1500 m. For the label sticker 4, a repeat 5019 (Yupo 80UV) manufactured by Lintec Corporation having a size of 15 mm × 100 mm was used. The pressure-sensitive adhesive composition of the label seal 4 is composed of a spherical pressure-sensitive adhesive composed of an acrylic polymer and a binder pressure-sensitive adhesive containing an emulsion containing an acrylic acid ester copolymer as a main component, and the base material is a polypropylene-based adhesive having a thickness of 80 μm. It consists of synthetic paper.

Prepare label stickers having different area ratios in areas where the adhesive layer surface of the label sticker 4 to be attached to the end of the long porous film 2 has a height threshold of 5 μm or more from the reference surface, and then peeled and reattached. The number of attachments was changed to one cycle.

[Example 1]
The label sticker attached to the end of the long porous film was peeled off, and the area ratio of the region having a height threshold of 5 μm or more from the reference surface of the adhesive layer surface of the label seal was measured. It was 8.4%. The label sticker was reattached to the end of the long porous film (the number of times the label sticker was reattached was one cycle). Further, the sticking method at that time was that the film was crimped once with a rubber roller having a weight of 2 kg along the curved surface of the outermost circumference of the film winding body.

[Example 2]
The label sticker attached to the end of the long porous film was peeled off and reattached, and then peeled off and reattached twice (the number of times the label sticker was reattached was 3 cycles). Finally, before attaching the label sticker, the area ratio of the region having a thickness of 5 μm or more from the reference surface on the surface of the adhesive layer of the label sticker was measured, and the area ratio was 5.1%. In the final method of attaching the label sticker, the film was crimped once with a rubber roller having a weight of 2 kg along the curved surface of the outermost circumference of the film winding body.

[Example 3]
The label sticker attached to the end of the long porous film was peeled off, and the area ratio of the region having a height threshold of 5 μm or more from the reference surface of the adhesive layer surface of the label seal was measured. It was 44.0%. The label sticker was reattached to the end of the long porous film (the number of times the label sticker was reattached was one cycle). Further, the sticking method at that time was that the film was crimped once with a rubber roller having a weight of 2 kg along the curved surface of the outermost circumference of the film winding body.

[Comparative Example 1]
The label sticker attached to the end of the long porous film was peeled off, and the area ratio of the region having a height threshold of 5 μm or more from the reference surface of the adhesive layer surface of the label seal was measured. It was 2.3%. The label sticker was reattached to the end of the long porous film (the number of times the label sticker was reattached was one cycle). Further, the sticking method at that time was that the film was crimped once with a rubber roller having a weight of 2 kg along the curved surface of the outermost circumference of the film winding body.

[Comparative Example 2]
The label sticker attached to the end of the long porous film was peeled off, and the area ratio of the region having a height threshold of 5 μm or more from the reference surface of the adhesive layer surface of the label seal was measured. It was 46.0%. The label sticker was reattached to the end of the long porous film (the number of times the label sticker was reattached was one cycle). Further, the sticking method at that time was that the film was crimped once with a rubber roller having a weight of 2 kg along the curved surface of the outermost circumference of the film winding body.

Two reels of each of the film winders of Examples 1 to 3 and Comparative Examples 1 and 2 were prepared, one reel was used for measuring the adhesive strength of the label seal, and the other reel was used during storage of the film winder. It was used to confirm the presence or absence of peeling of the label sticker.

The adhesive strength of the label sticker was measured once with a rubber roller weighing 2 kg along the curved surface of the outermost circumference of the film winding body in order to reduce the difference in crimping force between people when sticking the label sticker. .. In addition, the method of peeling the label sticker is also to reduce the difference in peeling speed and peeling angle by humans, so that the label sticker and the film are cut out from the outermost circumference of the film winding body in a pasted state, and a tensile tester is used. The adhesive strength of the label sticker was measured by the above-mentioned measuring method. The film base material of the label sticker is not particularly limited, but from the viewpoint of printability, flexibility, and dust generation, a polypropylene synthetic paper having a film thickness of 80 μm, a width of 15 mm, and a length of 100 mm is used as the adhesive layer. Used an acrylic spherical adhesive from the viewpoint of reattachability.

Whether or not the label seal is peeled off during storage of the film wound body is determined by storing each film wound body in an environment of 23 ° C. and 50% RH for 30 days, and the label seal is peeled off from the outermost film surface of the film wound body. It was visually confirmed whether or not it was peeled off, and if it was peeled off, it was evaluated as "Yes", and if it was not peeled off, it was evaluated as "No".

Table 1 shows the number of times the label sticker is reattached (cycle) and the height threshold of 5 μm or more from the reference surface of the adhesive layer surface of the label sticker before finally attaching the label sticker to the end of the long porous film. The result of measuring the area ratio of the area with the thickness of, the adhesive strength of the label sticker attached to the end of the long porous film, and the result of the presence or absence of peeling of the label sticker during storage of the film wound body. Are shown in Examples 1 to 3 and Comparative Examples 1 and 2.

As shown in Table 1, in Examples 1 and 3 based on the present invention, the number of times the label sticker is reattached is one cycle, and the thickness of the label sticker's adhesive layer surface with respect to the reference surface is 5 μm or more. Since the area ratio of the area to be held is 5% or more and the label seal secures the minimum adhesive force of 0.5 N / 15 mm or more for adhesively fixing and holding the end portion of the film, the film wound body is stored. No peeling of the label sticker occurred.

In Example 2, the number of reattachments is increased to 3 cycles as compared with Example 1, but the area ratio of the region having a thickness of 5 μm or more from the reference surface of the adhesive layer surface of the label sticker is 5. % Or more, the label seal secures the minimum adhesive strength of 0.5 N / 15 mm or more that holds the film end by adhesive fixing, so that the label seal does not peel off during storage of the film wound body. It was.

On the other hand, in Comparative Example 1, the number of times the label sticker is reattached is one cycle, the area ratio of the region having a thickness of 5 μm or more from the reference surface of the adhesive layer surface of the label sticker is less than 5%, and the label. Since the seal has less than 0.5 N / 15 mm, which is the minimum adhesive force for adhesively fixing and holding the end portion of the film, peeling of the label seal occurred during storage of the film wound body.

In Comparative Example 2, the number of times the label sticker is reattached is one cycle, the area ratio of the region having a thickness of 5 μm or more from the reference surface of the adhesive layer surface of the label sticker is 46.0%, and the label sticker. Has secured 0.5N / 15mm or more, which is the minimum adhesive force for adhesively fixing and holding the end of the film, so the label seal did not peel off during storage of the film wound body, but the adhesive force was measured. Occasionally, when the label sticker was peeled off, a part of the porous film was attached to the surface of the adhesive layer of the label sticker. This is because the contact area between the label seal and the porous membrane is increased, so that the amount of the adhesive penetrating into the pores of the porous membrane is increased, and as a result, the adhesive strength is increased. This is due to the fact that the structure of the membrane was destroyed and a part of the porous membrane was transferred to the adhesive layer of the label seal.

The film wound body according to the present invention can be used as a constituent material of a separator for a non-aqueous electrolyte secondary battery and the like.

1 Film winding body 2 Long porous film 3 Core
4 Label sticker (adhesive part)
5 Film end 7 Thick film region

Claims (6)

A film wound body in which a long porous film is wound around a winding core, and an adhesive portion provided at an end portion of the long porous film is adhesively fixed to the surface of the long porous film so as to be peelable. ,
The adhesive portion has a thick film region having a thickness of 5 μm or more and a thickness of less than 5 μm with respect to a reference plane whose plane is estimated by the least squares method from the shape of the height image of the film base material and the surface of the adhesive layer. A film wound body comprising an adhesive layer composed of a thin film region, wherein the area ratio of the thick film region to the entire region of the adhesive layer is 5 to 45%. The film wound body according to claim 1, wherein the long porous film is made of a porous film used as a separator for a non-aqueous electrolytic solution secondary battery. The film wound body according to claim 1 or 2, wherein the adhesive portion contains identification information of the long porous film. The film wound body according to any one of claims 1 to 3, wherein the adhesive layer is made of an acrylic spherical pressure-sensitive adhesive. The film wound body according to any one of claims 1 to 4, wherein the adhesive force of the adhesive portion to the surface of the long porous film is 0.5 to 4.0 N / 15 mm. The method for producing a film wound body according to any one of claims 1 to 5, wherein the adhesive portion provided at the end portion of the long porous film is peeled off and reattached at least once.

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