Core and separator roll
A core prevents or reduces misalignment of a battery separator wound around the core. The core has one or more grooves in the outer peripheral surface thereof. The grooves extend substantially in the width direction of the core. The grooves have a depth of 30 μm or greater, and the following condition (1) is satisfied: N/D >0.0025 (1) where D is the outer circumference in mm of the core and N is the number of the grooves in the outer peripheral surface.
1. A core for allowing a battery separator to be wound around an outer peripheral surface thereof, comprising two or more grooves in the outer peripheral surface, the two or more grooves extending in a direction intersecting a direction in which the battery separator is wound,
the two or more grooves having a depth of 30 μm or greater, and
the following condition (1) being satisfied:
N/D> 0.0025 (1)
where D is an outer circumference in mm of the core and N is the number of the two or more grooves in the outer peripheral surface.
2. The core according to claim 1 , wherein the two or more grooves have a depth of 1000 μm or less.
3. The core according to claim 1 , wherein the two or more grooves have a depth of 50 μm or greater.
4. The core according to claim 1 , wherein N/D<0.1.
5. The core according to claim 1 , wherein the two or more grooves have at least one end thereof at an edge of the core.
6. The core according to claim 1 , wherein the outer peripheral surface has a width, wherein the width is a dimension of the outer peripheral surface in a direction perpendicular to the direction in which the battery separator is wound, and wherein the two or more grooves are longer than half the width of the outer peripheral surface.
7. The core according to claim 1 , wherein the two or more grooves are at an angle of 15 degrees or less to a straight line perpendicular to the direction in which the battery separator is wound.
8. A separator roll comprising:
the core as set forth in claim 1 ; and
a battery separator wound around the core.
9. The separator roll according to claim 8 , wherein when a distance between an outer peripheral surface of the core and an outer peripheral surface of the wound separator roll having T turns is equal to or less than 10 mm, a distance between the outer peripheral surface of the core and an outer peripheral surface of the wound separator roll having T+1 turns is greater than 10 mm, wherein a misalignment between an edge of a first layer of the separator roll wound around the core and a corresponding edge of a P-th layer of the separator roll wound around the core is 1.5 mm or less, wherein P is an integer of 2 or more and T or less.
10. The core according to claim 1 , wherein the two or more grooves have both of opposite ends thereof positioned at opposite edges of the core.
11. The core according to claim 1 , wherein at least two of the two or more grooves intersect each other.