1. A method for producing a secondary battery including an electrode plate group in which a positive electrode plate and a negative electrode plate are wound or stacked with a separator interposed therebetween and a battery case in which the electrode plate group and an electrolyte are contained, the method comprising the steps of:
a) forming a positive electrode active material layer on a surface of a current collector core material of a positive electrode and a negative electrode active material layer on a surface of a current collector core material of a negative electrode;
b) forming a porous protective film on a surface of at least one of the positive electrode active material layer and the negative electrode active material layer to form a positive electrode plate and a negative electrode plate;
c) forming, after the step b), a plurality of grooves at least in a surface of the porous protective film;
d) forming, after the step c), an electrode plate group by winding or stacking the positive electrode plate and the negative electrode plate with a separator interposed therebetween; and
e) placing and injecting, after the step d), the electrode plate group and the electrolyte in the battery case, and sealing the battery case,
wherein in the step c), the plurality of grooves are formed simultaneously in the surface of the porous protective film and in a surface of the at least one of the active material layers.
2. The method of claim 1, wherein in the step c), the grooves are formed, using rollers each having projections formed on a circumference surface thereof, so that only the projections of the circumference surface of each of the rollers are in contact with the surface of the porous protective film.
3. The method of claim 1, wherein the porous protective film is formed so as to have a thickness of 2 \u03bcm or more and 20 \u03bcm or less.
4. The method of claim 1, wherein each of the grooves has a cross-sectional shape in which each of opening top portions and groove bottom corner portions of the groove has an arc shape.
5. The method of claim 1, wherein the grooves are formed so that each of the grooves has a depth of 4 \u03bcm or more and 20 \u03bcm or less.
6. The method of claim 1, wherein the grooves are formed so that a total volume of the grooves is 0.1% or more and 10% or less of a sum of a volume of the active material layer and a volume of the porous protective film.
7. The method of claim 1, wherein the grooves are formed so that each of the grooves extends from one end of the at least one of the electrodes to the other end thereof in a widthwise direction thereof.
8. The method of claim 1, wherein the grooves are formed so that each of the grooves extends so as to be perpendicular with or tilted from a longitudinal direction of the at least one of the electrode plates.
9. The method of claim 1, wherein the porous protective film contains at least one of silica and alumina.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A worn article, comprising a fitting portion that fits around a torso of a wearer, and an absorbent portion covering a crotch of the wearer and absorbing body fluid from the wearer, wherein:
the absorbent portion includes a first end portion and a second end portion that are connected to the fitting portion;
the first end portion of the absorbent portion can be detached from the fitting portion; and
a cover sheet is provided covering at least a portion of the first end portion.
2. A worn article according to claim 1, wherein:
the cover sheet is processed so that the cover sheet is tearable; and
a fastener member for detachably fastening together the absorbent portion and the fitting portion is placed on the absorbent portion or the fitting portion in a vicinity of the processed portion of the cover sheet.
3. A worn article according to claim 1, wherein:
the fitting portion includes an abdominal-side portion covering an abdominal side of the wearer, and a back-side portion covering a back side of the wearer;
the first end portion of the absorbent portion is connected to the abdominal-side portion of the fitting portion, and the second end portion of the absorbent portion is connected to the back-side portion of the fitting portion;
the first end portion is detachably touch-fastened to the fitting portion; and
a portion of the cover sheet that is covering the first end portion or a vicinity thereof is formed to be tearable.
4. A worn article according to claim 3, wherein:
in the touch-fastened first end portion, an inner surface of the absorbent portion is facing an outer surface of the abdominal-side portion of the fitting portion, and an inner surface of the cover sheet is facing an outer surface of the absorbent portion; and
the fitting portion, the absorbent body and the cover sheet are layered in this order starting from an inner side in a position corresponding to the first end portion.
5. A worn article according to claim 3, wherein a tearable portion for tearing the cover sheet is formed in the cover sheet by processing the cover sheet, so that at least a portion of the first end portion will be exposed when the cover sheet is torn along the tearable portion.
6. A worn article according to claim 3, wherein the cover sheet covers at least an upper edge of the first end portion of the absorbent portion.
7. A method for producing a worn article according to claim 4, wherein a member forming the absorbent portion and the cover sheet are placed on a web forming the fitting portion while carrying the web, the method comprising the steps of:
processing a portion of the cover sheet to be tearable;
carrying the web in a longitudinal direction of the web;
placing the member forming the absorbent portion on the web so that the member overlaps at least a portion of the web; and
placing the member forming the absorbent portion on the cover sheet so that the member overlaps at least a portion of the cover sheet processed to be tearable,
wherein the member forming the absorbent portion is sandwiched between the cover sheet processed to be tearable and the web as a result of carrying out the above steps.