Open-type disposable diaper with crotch stretch unit

An open-type disposable diaper comprising:

• a backsheet;
• a front waistline region;
• a back waistline region;
• a crotch region positioned between the front waistline region and the back waistline region;
• a pair of leg hole openings;
• an absorber spanning the crotch region and extending to the front waistline region and back waistline region, the absorber including an absorber core;
• a product longitudinal direction from the front waistline region towards the back waistline region;
• a product widthwise direction perpendicular to the product longitudinal direction;
• a crotch stretch unit arranged in the crotch region between the absorber and the backsheet and being stretchable in the product longitudinal direction;
• a pair of leg stretch units formed along the leg hole openings and being stretchable in at least the product longitudinal direction;
• and
• a waist stretch unit formed in the back waistline region and being stretchable in the product widthwise direction;
• wherein, in a plan view of the open-type disposable diaper,
• the absorber has an absorber core arrangement region where the absorber core is arranged,
• the absorber core arrangement region is enclosed by the crotch stretch unit, the leg stretch units, and the waist stretch unit, and is not stretchable,
• a length of the absorber core arrangement region in the product longitudinal direction is longer than a half of a length of the crotch stretch unit in the product longitudinal direction,
• the absorber includes, in the back waistline region, a first low rigidity region where a basis weight is lower than a remaining region of the absorber or where the absorber core is not arranged,
• the waist stretch unit has a region overlapping the first low rigidity region,
• a dimension of the first low rigidity region in the product widthwise direction gradually increases away from the crotch stretch unit in the product longitudinal direction,
• the absorber further includes, in the crotch region, a second low rigidity region and a third low rigidity region,
• the crotch stretch unit has opposing ends in the product longitudinal direction, and
• the second and third low rigidity regions extend in the product widthwise direction along the opposing ends of the crotch stretch unit.