JP4809197B2 - Method and apparatus for producing liquid permeable sheet - Google Patents

Description

  The present invention relates to a method and an apparatus for manufacturing a liquid permeable sheet.

  For example, sanitary napkins are known as absorbent articles that absorb liquid excreted from the human body such as menstrual blood. This absorbent article has an absorbent body made of pulverized pulp or the like, and the surface side (the side in contact with human skin, the skin side) of this absorbent body is covered with a liquid-permeable sheet 17.

  The liquid permeable sheet 17 is formed by, for example, welding and joining two nonwoven fabric sheets 16 and 14 by so-called embossing. FIG. 1 shows an explanatory view of this embossing in a side view. In this embossing process, two nonwoven fabric sheets 16 and 14 are sandwiched between the rotating upper roll 31 and the lower roll 51 so that a plurality of joint recesses 15 (hereinafter also referred to as embossing) are formed on the nonwoven fabric sheets 16 and 14. The two sheets 16 and 14 are joined together.

More specifically, the lower roll 51 is a smooth roll, but the upper roll 31 is an emboss roll in which a plurality of convex portions 33 are formed on the outer peripheral surface 31a, and these rolls 31, 51 are nonwoven fabric sheets 16, 14 respectively. It is heated to near the melting point. Therefore, as shown in FIG. 2, when the two nonwoven fabric sheets 16 and 14 pass through the gap between the upper roll 31 and the lower roll 51, the top surface 33 a of the convex portion 33 of the upper roll 31 and the lower roll 51. The portion sandwiched by the smooth outer peripheral surface 51a is melted to form a joint recess 15 (emboss), and the two nonwoven fabric sheets 16 and 14 are joined by the joint recess 15 (see Patent Document 1). ).
JP 2002-159534 A

  However, as shown in FIG. 2, compared with the embossing roll 31, the smooth roll 51 reduces the nonwoven fabric sheet 14 almost uniformly over the entire surface by the amount of the space S between the convex part 33 and the convex part 33. As a result, the bulkiness of the liquid-permeable sheet 17 is deteriorated. Further, the smooth roll 51 has a longer contact time with the nonwoven fabric sheet 14 as much as there is no space S. As a result, the surface 14b on the smooth roll 51 side of the nonwoven fabric sheet 14 is easily melted over the entire surface, and the bulkiness is increased. It will promote the deterioration.

  Therefore, as a measure for improving the bulkiness, for example, as shown in FIG. 3, a protrusion 43 having the same size as the upper roll 31 may be formed on the lower roll 41 in correspondence with the protrusion 33 of the upper roll 31. Conceivable. And under ideal design conditions, as shown in FIG. 4A, the top surface 33a of the convex portion 33 of the upper roll 31 and the top surface 43a of the convex portion 43 of the lower roll 41 coincide with each other during clamping. The range sandwiched between the convex portions 33 and 43 is equal to the area of the top surfaces 33a and 43a of the convex portions 33 and 43.

  However, in general, a roll has a backlash of a rotation driving gear, a mechanical backlash of a roll bearing (direction along the rotation axis), and the like. Relative position with respect to the circumferential direction of the roll and the rotation axis direction.

  Therefore, when such a deviation occurs under the same specifications of the convex portion 33 of the upper roll 31 and the convex portion 43 of the lower roll 41 as shown in FIG. 3, the schematic diagram of FIG. 4B shows. In this way, the range (shaded portion) sandwiched between the top surface 33a of the convex portion 33 of the upper roll 31 and the top surface 43a of the convex portion 41a of the lower roll 41 is the design dimension (shaded portion) shown in FIG. 4A. As a result, the joint strength of the joint recess may be reduced.

  The present invention has been made in view of the conventional problems as described above, and provides a method and an apparatus for manufacturing a liquid-permeable sheet capable of effectively preventing a decrease in the bonding strength of the bonding recess. Objective.

The main invention for achieving the above object is:
A method of manufacturing a liquid-permeable sheet by joining a plurality of sheets by sandwiching and pressing the plurality of sheets in a gap between a pair of rolls rotating with the outer peripheral surfaces thereof facing each other and having their outer peripheral surfaces facing each other. Because
A plurality of convex portions are formed on the outer peripheral surface of one roll of the pair of rolls, and the plurality of convex portions are formed on the outer peripheral surface of the other roll in correspondence with the convex portions. A convex part for forming a joint concave part by sandwiching the sheets is formed,
The method for producing a liquid-permeable sheet, wherein the top surface of the convex portion of the one roll and the top surface of the convex portion of the other roll corresponding to the convex portion have different sizes in a predetermined direction. It is.

In addition, a liquid permeable sheet is manufactured by joining a plurality of sheets by sandwiching a plurality of sheets into a gap between a pair of rolls rotating with the rotation axes aligned in parallel and facing the outer peripheral surfaces. A device that performs
A plurality of convex portions are formed on the outer peripheral surface of one roll of the pair of rolls, and the plurality of convex portions are formed on the outer peripheral surface of the other roll in correspondence with the convex portions. A convex part for forming a joint concave part by sandwiching the sheets is formed,
The liquid-permeable sheet manufacturing apparatus, wherein the top surface of the convex portion of the one roll and the top surface of the convex portion of the other roll corresponding to the convex portion have different sizes in a predetermined direction. It is.

  Other features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method and manufacturing apparatus of a liquid-permeable sheet which can prevent effectively the joining strength fall of a joining recessed part can be provided.

  At least the following matters will become clear from the description of the present specification and the accompanying drawings.

A method of manufacturing a liquid-permeable sheet by joining a plurality of sheets by sandwiching and pressing the plurality of sheets in a gap between a pair of rolls rotating with the outer peripheral surfaces thereof facing each other and having their outer peripheral surfaces facing each other. Because
A plurality of convex portions are formed on the outer peripheral surface of one roll of the pair of rolls, and the plurality of convex portions are formed on the outer peripheral surface of the other roll in correspondence with the convex portions. A convex part for forming a joint concave part by sandwiching the sheets is formed,
The method for producing a liquid-permeable sheet, wherein the top surface of the convex portion of the one roll and the top surface of the convex portion of the other roll corresponding to the convex portion have different sizes in a predetermined direction. It is.
According to such a method of manufacturing a liquid permeable sheet, it is possible to effectively prevent the bonding strength of the bonding concave portion from being lowered due to a shift in the relative position of the pair of rolls in the predetermined direction.

  Details are as follows. Of the convex portion of the one roll and the convex portion of the other roll facing each other at the time of clamping, the convex portion with the larger top surface with respect to the predetermined direction has the smaller top surface with respect to the predetermined direction. It protrudes outward in the same direction from the convex part. Therefore, even if the relative position of the pair of rolls is shifted in the predetermined direction by the amount of protrusion, there is no change in the size of the range where the protrusions are clamped, and the bonding strength of the bonding recesses is reduced. Can be effectively prevented.

A method for producing such a liquid-permeable sheet,
The predetermined direction is a direction along the rotation axis,
It is desirable that the top surface of the convex portion of the one roll protrudes outside the top surface of the other convex portion on both sides in the direction along the rotation axis.
According to such a method for manufacturing a liquid-permeable sheet, even if the relative position of the pair of rolls is shifted to either side in the direction along the rotation axis, it is possible to effectively reduce the bonding strength of the bonding recess. Can be prevented.

A method for producing such a liquid-permeable sheet,
The convex portion of the one roll is preferably a rib extending continuously over the entire width of the plurality of sheets in the direction along the rotation axis.
According to such a method for manufacturing a liquid-permeable sheet, even if the relative position between the pair of rolls is shifted to either side in the direction along the rotation axis, it is possible to reliably reduce the bonding strength of the bonding recess. Can be prevented.

A method for producing such a liquid-permeable sheet,
The predetermined direction is a circumferential direction of the roll,
It is desirable that the top surface of the convex portion of the other roll protrudes outside the top surface of the one convex portion on both sides in the circumferential direction of the roll.
According to such a method for manufacturing a liquid-permeable sheet, even if the relative position between the pair of rolls is shifted in any direction in the circumferential direction of the roll, it is possible to effectively prevent a reduction in the bonding strength of the bonding recess. be able to.

A method for producing such a liquid-permeable sheet,
The convex portion of the other roll is preferably a rib extending continuously over the entire length in the circumferential direction.
According to such a method for producing a liquid-permeable sheet, even if the relative position between the pair of rolls is shifted to either side in the circumferential direction, it is possible to reliably prevent a decrease in the bonding strength of the bonding recess. it can.

A method for producing such a liquid-permeable sheet,
It is desirable that a pressing roll for pressing at least one of the plurality of sheets against the convex portion of the roll is provided on the entry side of the gap of the roll.
According to such a method of manufacturing a liquid permeable sheet, the sheet pressed against the convex portion of the roll by the pressing roll enters the space between the convex portion and the convex portion adjacent to each other in the roll. Therefore, the amount of the sheet entering the space between the adjacent convex portions can be increased, and as a result, the bulkiness of the liquid-permeable sheet can be increased.

A method for producing such a liquid-permeable sheet,
The liquid permeable sheet is a sheet for covering from the skin side of the human body an absorber that absorbs liquid excreted from the human body,
The plurality of sheets are composed of a surface sheet positioned on the skin side when worn, and an intermediate sheet positioned on the absorber side,
Of the pair of rolls, it is preferable that the pressing roll is provided only for a roll that comes into contact with the top sheet in the gap.
According to such a method for producing a liquid-permeable sheet, it is possible to produce a liquid-permeable sheet having excellent touch to human body and excellent liquid permeability to the absorbent body.

In addition, a liquid permeable sheet is manufactured by joining a plurality of sheets by sandwiching a plurality of sheets into a gap between a pair of rolls rotating with the rotation axes aligned in parallel and facing the outer peripheral surfaces. A device that performs
A plurality of convex portions are formed on the outer peripheral surface of one roll of the pair of rolls, and the plurality of convex portions are formed on the outer peripheral surface of the other roll in correspondence with the convex portions. A convex part for forming a joint concave part by sandwiching the sheets is formed,
The liquid-permeable sheet manufacturing apparatus, wherein the top surface of the convex portion of the one roll and the top surface of the convex portion of the other roll corresponding to the convex portion have different sizes in a predetermined direction. It is.
According to such a liquid permeable sheet manufacturing apparatus, it is possible to effectively prevent a decrease in the bonding strength of the bonding recess due to a shift in the relative position of the pair of rolls in the predetermined direction.

=== Manufacturing Method of the First Embodiment ===
<< Application Example of Liquid Permeable Sheet 17 >>
First, an application example of the liquid permeable sheet 17 manufactured by the manufacturing method of the first embodiment will be described. Here, the liquid permeable sheet 17 is applied to a sanitary napkin as the absorbent article 1. In the following description, the side in contact with the human body is referred to as the front side, and the side in contact with the underwear is described as the back side.

  FIG. 5A is a plan view of the surface side of the absorbent article 1. 5B is a cross-sectional view taken along the line BB in FIG. 5A. As shown in FIG. 5A, the absorbent article 1 has an overall shape that is long in a predetermined direction. Hereinafter, this predetermined direction is referred to as a longitudinal direction, and a direction orthogonal to the longitudinal direction is referred to as a width direction.

  As shown in FIGS. 5A and 5B, the absorbent article 1 has a substantially rectangular flat plate shape in which pulverized pulp mixed with a superabsorbent polymer is wrapped in a liquid-permeable sheet (not shown) such as tissue paper. Absorber 12, surface sheet 14 provided so as to cover at least the surface side of absorber 12, the intermediate sheet 16 disposed between surface sheet 14 and absorber 12, and absorber 12 The back sheet 18 for preventing leakage of the liquid absorbed by the back surface and both ends of the top sheet 14 in the width direction to prevent leakage of liquid from both ends of the absorbent article 1 in the width direction. And a pair of side sheets 20 provided so as to cover along the longitudinal direction.

As shown to FIG. 5A, the surface sheet 14 is a substantially rectangular liquid-permeable sheet a little larger than the planar shape of the absorber 12, The material is 0.02-0.15 (g / cm < ³ >), for example. ), And a basis weight of 15 to 70 (g / cm ² ) is used. Examples of the nonwoven fabric include air through, spun bond, needle punch, melt blown, thermal bond, and chemical bond. The constituent fibers of the nonwoven fabric are thermoplastic resin fibers, such as polyethylene, polyethylene terephthalate, polypropylene, polyethylene / polyethylene terephthalate sheath-core composite fiber, polyethylene / polypropylene sheath-core composite fiber, polyester. And polyamide-based fibers.

  The intermediate sheet 16 is a rectangular liquid-permeable sheet having a higher liquid holding power than the top sheet 14, and the material exemplified in the top sheet 14 is used. However, a sheet having a higher density than the surface sheet 14 is used in order to improve the absorbability of the liquid from the surface sheet 14.

  The topsheet 14 and the intermediate sheet 16 are joined by a plurality of joint recesses 15 formed by embossing, which will be described later, and as shown in FIGS. 5A and 5B, On the front surface and the back surface of the intermediate sheet 16, an emboss 15 as the bonding recess 15 is formed over substantially the entire surface. The sheet 17 formed by joining both the sheets 14 and 16 corresponds to a “liquid permeable sheet” manufactured by the manufacturing method of the first embodiment. This manufacturing method will be described later.

  The back sheet 18 is a liquid-impermeable sheet made of, for example, polyethylene, polypropylene, or the like, and the shape thereof is a substantially rectangular shape that is larger than the absorber 12 in both the longitudinal direction and the width direction as shown in FIG. 5A. Is. And the said back surface sheet 18 is joined to the liquid permeable sheet 17 in the both ends of a longitudinal direction in the state which mounted the absorber 12 on the surface, Thereby, by this, the back surface sheet 18 and the liquid permeable sheet 17 of The absorber 12 is held therebetween.

  As shown in FIG. 5B, an undergarment fixing adhesive 19 for applying the absorbent article 1 to the inner surface of the undergarment during use is applied to the back surface of the back sheet 18. Further, wing portions 18f are formed to extend outward in the width direction at both ends in the width direction of the back sheet 18, and an undergarment fixing adhesive 19 is also applied to the back surfaces of the wing portions 18f and 18f. . When the absorbent article 1 is fixed to the underwear, the wing portions 18f and 18f are folded outward and fixed to the outer surface of the underwear by the underwear fixing adhesive 19.

<< Method for Producing Liquid Permeable Sheet 17 >>
FIG. 6 is a side view of the production line of the liquid permeable sheet 17. The production line for the liquid permeable sheet 17 is, for example, a part of the production line for the absorbent article 1. That is, the liquid permeable sheet 17 manufactured in the manufacturing line of the liquid permeable sheet 17 is conveyed downstream in the flow direction of the line in a continuous sheet state. The other parts such as the absorbent body 12 manufactured in step 1 are sequentially attached to finally form the absorbent article 1. Here, only the production line of the liquid permeable sheet 17 will be described.

  As shown in FIG. 6, a pair of upper and lower reels 201 and 203 are installed at the first processing position P <b> 1 of the production line for the liquid permeable sheet 17. An intermediate sheet roll 16r wound in a roll shape and a surface sheet roll 14r wound in a roll shape are attached to the upper reel 201 and the lower reel 203, respectively. From the upper reel 201, the intermediate sheet 16 is fed out in a continuous sheet state, and from the lower reel 203, the top sheet 14 is fed out in a continuous sheet state. To the next processing position P2 downstream in the flow direction.

  Incidentally, here, while the intermediate sheet roll 16r is attached to the upper reel 201 and the surface sheet roll 14r is attached to the lower reel 203, it may be upside down. However, when the absorbent body 12 is placed and supplied on the liquid permeable sheet 17 at the downstream side, it is preferable that the intermediate sheet 16 is positioned on the top sheet 14. As shown in the drawing, the intermediate sheet roll 16r may be assigned to the upper reel 201 and the front sheet roll 14r may be assigned to the lower reel 203.

  At the processing position P2, a joining device 211 is provided for embossing the intermediate sheet 16 and the top sheet 14 while superimposing the intermediate sheet 16 and the top sheet 14 on top of each other and joining the two sheets 16 and 14 together.

  FIG. 7 is a front view of this joining apparatus 211 (that is, a view shown by arrows VII-VII in FIG. 6). The joining device 211 includes a pair of upper and lower embossing rolls 61, 71 rotating with the outer peripheral surfaces 61a, 71a facing each other while aligning the rotation axes C61, C71 in parallel, and the embossing rolls 61, 71 as the rotation axes C61, 71. And a rotation drive mechanism 221 for rotating around C71.

  The upper and lower embossing rolls 61 and 71 are steel cylinders having the same diameter, and both end portions thereof in the rotational axis direction are supported by the housing 213 of the joining device 211 via radial bearings, thrust bearings 215, and the like. Thus, it can rotate around the rotation axis. In this example, the upper embossing roll 61 is supported by the housing 213 so as not to be moved up and down, but the lower embossing roll 71 is supported by a lifting mechanism 217 such as a hydraulic cylinder so as to be lifted and lowered. Therefore, the size of the gap between the upper embossing roll 61 and the lower embossing roll 71 is adjusted by the lifting operation of the lifting mechanism 217. Further, a heating element (not shown) for heating the embossing rolls 61, 71 is incorporated in each embossing roll 61, 71, and by adjusting the amount of generated heat, the embossing rolls 61, 71 have a heating element (not shown). Temperature adjustment of the postscript convex parts 63 and 73 of the outer peripheral surfaces 61a and 71a is performed.

  As shown in FIG. 7, the rotational drive mechanism 221 distributes the drive torque from the motor 223 serving as a drive source for the rotational operation of the upper and lower embossing rolls 61 and 71 to the upper and lower embossing rolls 61 and 71. And a pair of upper and lower spindles 227a and 227b for transmitting the distributed drive torque to the upper and lower embossing rolls 61 and 71. Then, the uniaxial driving torque supplied from the motor 223 is distributed to the biaxial driving torque by a pair of gears 225a and 225b meshing with each other in the pinion stand 225, and these biaxial driving torques are respectively transmitted to the gear 225a. , 225b is transmitted to the upper embossing roll 61 and the lower embossing roll 71 via the upper spindle 227a and the lower spindle 227b, so that the upper and lower embossing rolls 61, 71 rotate at the same peripheral speed. It has become.

  According to such a joining device 211, as shown in FIG. 6, the intermediate sheet 16 and the top sheet 14 are passed through the gap between the rotating upper and lower embossing rolls 61 and 71 in a state where they are stacked one above the other. In this case, the projection 63 formed on the outer circumferential surface 61 a of the upper embossing roll 61 and the projection 73 formed on the outer circumferential surface 71 a of the lower embossing roll 71 corresponding to the projection 63 are intermediate. The sheet 16 and the top sheet 14 are pinched. Here, at this time, the convex portions 63 and 73 are heated to a temperature near the melting point of the constituent fibers of the intermediate sheet 16 and the top sheet 14 by the heating element. Therefore, the portions of the intermediate sheet 16 and the top sheet 14 sandwiched between the convex portions 63 and the convex portions 73 are melted to become the joint concave portions 15, and thus the intermediate sheet 16 and the top sheet 14 are integrally joined, These joined sheets 17 are sent as a liquid permeable sheet 17 downstream in the flow direction.

  FIGS. 8 to 10 are explanatory diagrams of the arrangement pattern of the convex portions 63 and 73 formed on the outer peripheral surfaces 61a and 71a of the upper and lower embossing rolls 61 and 71. FIG. FIG. 8 shows a front view of the upper embossing roll 61 and the lower embossing roll 71, and FIG. 9 shows the outer peripheral surfaces 61 a and 71 a of the upper embossing roll 61 and the lower embossing roll 71 in a circumferential direction. . FIG. 10A is an explanatory diagram of the convex portion 63 of the upper embossing roll 61, and FIG. 10B is an explanatory diagram of the convex portion 73 of the lower embossing roll 71. FIG. 11A and FIG. 11B are explanatory diagrams of a pinching range in which pinching is performed between the convex portion 63 of the upper embossing roll 61 and the convex portion 73 of the lower embossing roll 71.

  As shown in FIGS. 8 and 9, on the smooth outer peripheral surface 61a of the upper embossing roll 61, island-shaped convex portions 63 are formed in a lattice shape with a formation pitch P1 in the rotation axis direction and a formation pitch P2 in the circumferential direction. Are formed on the smooth outer peripheral surface 71a of the lower embossing roll 71 at the formation pitch P1 in the rotation axis direction and at the formation pitch P2 in the circumferential direction. The island-shaped convex part 73 is formed in the shape. In the ideal state where the joining device 211 has no mechanical play regarding the rotation axis direction and the circumferential direction, as shown in FIG. 11A, the top surface centers C63a of the protrusions 63 and 73 corresponding to each other at the time of clamping. C73a matches.

  As shown in FIGS. 10A and 10B, the convex portions 63 and 73 are substantially rectangular parallelepiped shapes for the upper and lower embossing rolls 61 and 71, and the flat top surfaces 63a and 73a have the same dimensions as each other. It is a rectangle. However, the upper embossing roll 61 and the lower embossing roll 71 are different from each other in the longitudinal direction of the top surfaces 63a and 73a of the convex portions 63 and 73, that is, the top of the convex portion 63 of the upper embossing roll 61. The longitudinal direction of the surface 63a faces the rotation axis direction of the roll, but the longitudinal direction of the top surface 73a of the convex portion 73 of the lower embossing roll 71 faces the circumferential direction of the roll and is orthogonal to each other.

  Therefore, as shown in FIG. 11A, the top surface 63a of the convex portion 63 of the upper embossing roll 61 is larger than the top surface 73a of the convex portion 73 of the lower embossing roll 71 with respect to the rotation axis direction. As shown in FIG. 11B, the top surface 73 a of the convex portion 73 of the lower embossing roll 71 is conversely larger than the top surface 63 a of the convex portion 63 of the upper embossing roll 61. More specifically, as shown in FIG. 11A, the top surface 63a of the convex portion 63 of the upper embossing roll 61 is X1 more than the top surface 73a of the convex portion 73 of the lower embossing roll 71 on both sides in the rotational axis direction. While protruding outward, the top surface 73a of the convex portion 73 of the lower embossing roll 71 is conversely the top surface 63a of the convex portion 63 of the upper embossing roll 61 on both sides in the circumferential direction as shown in FIG. 11B. Also, only X1 protrudes outside.

  Therefore, even if the relative positions of the upper and lower embossing rolls 61 and 71 deviate from the ideal state described above in the direction of the rotation axis and in the circumferential direction, as long as the deviation amount is within the range of the protrusion amount X1 described above, FIG. As shown in Fig. 12A, the pinching range sandwiched between the convex portion 63 of the upper embossing roll 61 and the convex portion 73 of the lower embossing roll 71 at the time of pinching is the same as the design dimension indicated by the oblique lines in FIG. As a result, a decrease in the bonding strength of the bonding recess 15 formed by these protrusions 63 and 73 is effectively prevented.

  The protrusion amount X1 in the rotation axis direction is determined based on, for example, a cumulative tolerance in the rotation axis direction obtained by accumulating dimensional tolerances in the rotation axis direction of the joining device 211 in FIG. Is determined based on, for example, a cumulative circumferential tolerance obtained by accumulating all the dimensional tolerances in the circumferential direction of the rolls of the joining device 211. The main tolerance of the former is the clearance in the rotational axis direction of the thrust bearing 215 and the like, while the main tolerance of the latter is that of the pair of gears 225a and 225b in the pinion stand 225. Examples include backlash. However, the protrusion amount X1 may be determined based on other reasons.

  FIG. 13 is a plan view of the upper surface side and the lower surface side of the liquid permeable sheet 17 manufactured by the embossing rolls 61 and 71 according to the first embodiment. Since the liquid permeable sheet 17 is produced by being pressed at the intersection of the convex portion 63 of the upper embossing roll 61 and the convex portion 73 of the lower embossing roll 71, the liquid permeable sheet 17 is formed on the upper and lower surfaces of the liquid permeable sheet 17. Are formed in a lattice shape with a pitch P2 in the flow direction of the line and with a pitch P1 in the width direction perpendicular to the flow direction.

=== Manufacturing Method of Second to Seventh Embodiments ===
Hereinafter, the manufacturing method of 2nd thru | or 7th embodiment is demonstrated. Each embodiment is different from the first embodiment described above in terms of the arrangement pattern of the convex portions on the outer peripheral surfaces 61a and 71a of the upper embossing roll 61 and the lower embossing roll 71.

<< Second Embodiment >>
14 and 15 are explanatory diagrams of the arrangement pattern of the convex portions according to the second embodiment. FIG. 14 shows a front view of the upper embossing roll 61 and the lower embossing roll 71, and FIG. 15 shows the outer peripheral surfaces 61a and 71a of the upper embossing roll 61 and the lower embossing roll 71 developed in the circumferential direction.

  In this 2nd Embodiment, although the arrangement pattern of the convex part 63 of the upper embossing roll 61 is the same as 1st Embodiment, the arrangement pattern of the convex part of the lower embossing roll 71 is different. That is, among the convex portions of the outer peripheral surface 71a of the lower embossing roll 71, all the convex portions having the same position in the rotation axis direction are connected over the entire length in the circumferential direction. As shown, annular ribs 74 along the circumferential direction are formed on the outer peripheral surface 71a of the lower embossing roll 71 at a pitch P1 in the rotation axis direction.

  Therefore, in the case of the second embodiment, even if the relative position between the upper embossing roll 61 and the lower embossing roll 71 is greatly shifted in the circumferential direction, the rib 74 of the lower embossing roll 71 extends over the entire length in the circumferential direction. Therefore, the clamping range with the convex part 63 of the upper embossing roll 61 can be maintained to be the same as the design dimension, and as a result, the joint concave part 15 formed by the convex part 63 and the rib 74 is joined. Strength reduction is reliably prevented.

  FIG. 16 is a plan view of the upper surface side and the lower surface side of the liquid-permeable sheet 17 manufactured by the embossing rolls 61 and 71 according to the second embodiment. Since the pressure is applied at the intersection between the convex portion 63 of the upper embossing roll 61 and the rib 74 of the lower embossing roll 71, the pitch P1 in the width direction is formed on the upper and lower surfaces of the liquid-permeable sheet 17 as shown in FIG. In addition, joint recesses 15 are formed in a lattice shape with a pitch P2 in the flow direction. However, since the rib 74 along the circumferential direction contacts the lower surface of the liquid-permeable sheet 17 that comes into contact with the lower embossing roll 71, a groove along the flow direction as shown in FIG. 15a is formed at a pitch P1 in the width direction.

<< Third Embodiment >>
17 and 18 are explanatory diagrams of the arrangement pattern of the protrusions of the third embodiment. FIG. 17 shows a front view of the upper embossing roll 61 and the lower embossing roll 71, and FIG. 18 shows the outer peripheral surfaces 61a and 71a of the upper embossing roll 61 and the lower embossing roll 71 in a circumferential direction.

  In the third embodiment, contrary to the second embodiment described above, the arrangement pattern of the convex portions 73 of the lower embossing roll 71 is the same as that of the first embodiment, but the convex portion of the upper embossing roll 61 is the same. The arrangement pattern is different from that of the first embodiment. That is, among the convex portions of the outer peripheral surface 61a of the upper embossing roll 61, all the convex portions having the same circumferential position are connected over the rotational axis direction, and as a result, in FIG. 17 and FIG. As shown, on the outer peripheral surface 61a of the upper embossing roll 61, linear ribs 64 along the rotational axis direction are formed at a pitch P2 in the circumferential direction.

  Therefore, in the case of the third embodiment, even if the relative position between the upper embossing roll 61 and the lower embossing roll 71 is greatly displaced in the rotational axis direction, the ribs 64 of the upper embossing roll 61 are liquid in the rotational axis direction. Since it spans the length corresponding to the full width of the permeable sheet 17, the pressure-holding range with the convex part 73 of the lower embossing roll 71 can be maintained at the same dimension as the design dimension. As a result, these ribs A decrease in the bonding strength of the bonding recess 15 formed by the 64 and the protrusion 73 is reliably prevented.

  FIG. 19 is a plan view of the upper surface side and the lower surface side of the liquid permeable sheet 17 manufactured by the embossing rolls 61 and 71 according to the third embodiment. Since the pressure is applied at the intersection between the rib 64 of the upper embossing roll 61 and the convex portion 73 of the lower embossing roll 71, as shown in FIG. 19, the upper surface and the lower surface of the liquid permeable sheet 17 have a pitch P1 in the width direction. In addition, joint recesses 15 are formed in a lattice shape with a pitch P2 in the flow direction. However, the upper surface of the liquid permeable sheet 17 that comes into contact with the ribs 64 of the upper embossing roll 61 comes into contact with the ribs 64 along the rotation axis direction, so that the upper surface has a width direction as shown in FIG. Are formed at a pitch P2 in the flow direction.

<< Fourth Embodiment >>
20 and 21 are explanatory diagrams of the arrangement pattern of the convex portions according to the fourth embodiment. 20 shows a front view of the upper embossing roll 61 and the lower embossing roll 71, and FIG. 21 shows the outer peripheral surfaces 61a and 71a of the upper embossing roll 61 and the lower embossing roll 71 in a circumferential direction.

  The fourth embodiment is a combination of the second embodiment and the third embodiment, that is, the arrangement pattern of the convex portions of the lower embossing roll 71 is the same as that of the second embodiment, but the upper embossing roll. The arrangement pattern of the convex portions 61 is the same as that in the third embodiment. Specifically, as shown in FIG. 21, annular ribs 74 along the circumferential direction are formed on the outer peripheral surface 71a of the lower embossing roll 71 at a pitch P1 in the rotation axis direction, and the upper embossing On the outer peripheral surface 61a of the roll 61, linear ribs 64 along the rotational axis direction are formed at a pitch P2 in the circumferential direction.

  Therefore, in the case of the fourth embodiment, the rib 64 of the upper embossing roll 61 and the upper embossing roll 61 and the lower embossing roll 71, regardless of whether the relative position of the upper embossing roll 61 and the rotational axis direction is greatly shifted The clamping pressure range of the lower embossing roll 71 with the rib 74 can be maintained the same as the design dimension, and as a result, the bonding strength of the bonding recess 15 formed by these ribs 64 and 74 is reliably reduced. Is prevented.

  FIG. 22 is a plan view of the upper surface side and the lower surface side of the liquid permeable sheet 17 manufactured by the embossing rolls 61 and 71 according to the fourth embodiment. Since the pressure is applied at the intersection of the rib 64 of the upper embossing roll 61 and the rib 74 of the lower embossing roll 71, as shown in FIG. 22, the upper and lower surfaces of the liquid-permeable sheet 17 have a pitch P1 in the width direction and Bonding recesses 15 are formed in a lattice shape with a pitch P2 in the flow direction. Further, since the rib 64 along the rotational axis is in contact with the upper surface of the liquid permeable sheet 17 that comes into contact with the upper embossing roll 61, the upper surface is along the width direction as shown in FIG. The grooves 15b are formed at a pitch P2 in the circumferential direction. On the other hand, the lower surface of the liquid-permeable sheet 17 that contacts the lower embossing roll 71 is in contact with the rib 74 along the circumferential direction. As shown in FIG. 22, grooves 15a along the flow direction are formed at a pitch P1 in the width direction.

  Incidentally, in the fourth embodiment, annular ribs 64 are formed on the upper embossing roll 61 at a constant pitch P1 over the rotational axis direction, and linear ribs 74 are formed on the lower embossing roll 71 in the circumferential direction. However, the present invention is not limited to this. For example, as shown in the development view in the circumferential direction of the outer peripheral surfaces 61a and 71a of the upper and lower embossing rolls 61 and 71 in FIG. 23, the ribs according to the circumferential position of the linear rib 64 in the upper embossing roll 61 The pitches P21, P22,..., P26 at which 64 is formed may be changed in the circumferential direction, and the rib 74 is formed according to the position of the annular rib 74 in the lower embossing roll 71 in the rotational axis direction. The pitches P11, P12, and P13 may be changed with respect to the rotation axis direction.

<< Fifth Embodiment >>
24 and 25 are explanatory diagrams of the arrangement pattern of the convex portions according to the fifth embodiment. FIG. 24 shows a front view of the upper embossing roll 61 and the lower embossing roll 71, and FIG. 25 shows the outer peripheral surfaces 61a and 71a of the upper embossing roll 61 and the lower embossing roll 71 developed in the circumferential direction.

  In the fifth embodiment, the upper and lower embossing rolls 61 and 71 are not ribs, but are substantially rectangular parallelepiped island-shaped convex portions 65 and 73 formed in the direction of the rotation axis as in the first embodiment. P1 is formed at a formation pitch P2 in the circumferential direction. However, it differs from the first embodiment in that the longitudinal direction of the top surface 65a of the convex portion 65 of the upper embossing roll 61 and the longitudinal direction of the top surface 73a of the convex portion 73 of the lower embossing roll 71 are aligned. That is, the longitudinal direction of the top surface 65a of the convex portion 65 of the upper embossing roll 61 and the longitudinal direction of the top surface 73a of the convex portion 73 of the lower embossing roll 71 are both directed in the circumferential direction, and these directions are aligned. Yes. And in such 5th Embodiment, as shown in FIG. 25, the magnitude | size of the top surface 65a of the convex part 65 of the upper embossing roll 61 rotates rather than the top surface 73a of the convex part 73 of the lower embossing roll 71. By being formed small in both the axial direction and the circumferential direction, the bonding strength of the bonding recess 15 can be lowered when the relative positions of the upper embossing roll 61 and the lower embossing roll 71 are shifted in the rotation axis direction and the circumferential direction. Is preventing.

  FIG. 26 is a plan view of the upper surface side and the lower surface side of the liquid-permeable sheet 17 manufactured by the embossing rolls 61 and 71 according to the fifth embodiment. Since the convex portion 65 of the upper embossing roll 61 and the convex portion 73 of the lower embossing roll 71 are sandwiched, as shown in FIG. 26, the upper surface and the lower surface of the liquid permeable sheet 17 have a pitch P1 in the width direction and Bonding recesses 15c are formed in a lattice shape with a pitch P2 in the flow direction. However, the shape of the joint recess 15c is a rectangle having the same shape as the top surface 65a of the convex portion 65 of the upper embossing roll 61 having the smaller top surface 65a.

<< Sixth Embodiment >>
27 and 28 are explanatory diagrams of the arrangement pattern of the convex portions according to the sixth embodiment. FIG. 27 shows a front view of the upper embossing roll 61 and the lower embossing roll 71, and FIG. 28 shows the outer peripheral surfaces 61a and 71a of the upper embossing roll 61 and the lower embossing roll 71 developed in the circumferential direction.

  In the sixth embodiment, the upper and lower embossing rolls 61 and 71 have substantially rectangular parallelepiped island-shaped protrusions 63 and 73 formed in the rotation axis direction, similarly to the protrusions of the first embodiment. P1 is formed at the formation pitch P2 in the circumferential direction, and corresponds to the longitudinal direction of the top surface 63a of the convex portion 63 of the upper embossing roll 61 and the convex portion 63 as in the first embodiment. The longitudinal direction of the top surface 73a of the convex portion 73 of the lower embossing roll 71 is orthogonal to each other.

  However, the convex arrangement pattern of the sixth embodiment has a zigzag shape in which convex portions adjacent to each other in the circumferential direction are alternately positioned in the rotation axis direction. Specifically, on the outer peripheral surface 61a of the upper embossing roll 61, a row of convex portions 63 (hereinafter referred to as a convex portion row) in which the convex portions 63 are arranged at a formation pitch P1 along the rotation axis direction is provided in the circumferential direction. Although arranged at the formation pitch P2, the convex rows adjacent to each other in the circumferential direction are shifted by a half pitch (= P1 / 2) in the rotation axis direction, and constitute the mutual convex rows. The convex portions 63 are alternately positioned with respect to the rotation axis direction. Similarly, on the outer peripheral surface 71a of the lower embossing roll 71 corresponding to each of the convex portions 63, similarly, the convex row, in which the convex portions 73 are arranged at the formation pitch P1 along the rotation axis direction, is mutually circumferential. The convex rows adjacent in the direction are arranged so as to be shifted by a half pitch (= P1 / 2) in the rotation axis direction.

  FIG. 29 is a plan view of the upper surface side and the lower surface side of the liquid-permeable sheet 17 manufactured by the embossing rolls 61 and 71 according to the sixth embodiment. Since the convex portion 63 of the upper embossing roll 61 and the convex portion 73 of the lower embossing roll 71 are sandwiched, as shown in FIG. 29, the upper surface and the lower surface of the liquid permeable sheet 17 are arranged in the flow direction as a whole. Adjacent joint recesses 15 are formed in a staggered pattern alternately positioned in the width direction.

<< Seventh Embodiment >>
30 and 31 are explanatory diagrams of the arrangement pattern of the convex portions according to the seventh embodiment. 30 shows a front view of the upper embossing roll 61 and the lower embossing roll 71, and FIG. 31 shows the outer peripheral surfaces 61a and 71a of the upper embossing roll 61 and the lower embossing roll 71 in a circumferential direction. FIG. 32 is a plan view of the upper surface side and the lower surface side of the liquid permeable sheet 17 manufactured by the embossing rolls 61 and 71 according to the seventh embodiment.

  The seventh embodiment is a combination of the above-described fourth embodiment and the second embodiment. That is, basically, the upper embossing roll 61 is formed with a rib 64 in the rotation axis direction, and the lower embossing roll 71 is formed with a circumferential rib 74, but on the outer circumferential surface 61 a of the upper embossing roll 61. In some regions R61, island-shaped convex portions 63 are provided instead of the ribs 74. Then, by forming the island-shaped convex portions 63 by thinning out from the formation pitch P1 × P2 of the second embodiment described above, as shown in FIG. 32, with respect to the predetermined range R17 in the liquid permeable sheet 17 Thus, the number of the joint recesses 15 is formed so as to be thinner than the formation pitch P1 × pitch P2 of the second embodiment described above.

  As shown in FIG. 31, the partial region R61 is, for example, a central portion in the rotation axis direction, and is formed at two locations in the circumferential direction. In this partial region R61, every other island-like convex portion 63 is thinned out. Therefore, according to the embossing rolls 61 and 71 according to the seventh embodiment, as shown in FIG. 32, over the predetermined range R17 in the flow direction at the center in the width direction of the liquid permeable sheet 17, rather than the surroundings. A region having a low density of the bonding recess 15 is formed. Since the predetermined region R17 corresponds to a portion where the rib 74 of the upper embossing roll 61 is not provided, the groove 15b along the width direction is not formed on the upper surface of the liquid permeable sheet 17.

=== Other Embodiments ===
As mentioned above, although embodiment of this invention was described, this invention is not limited to this embodiment, The deformation | transformation as shown below is possible.

  In the above-described embodiment, two sheets of the front sheet 14 and the intermediate sheet 16 are illustrated as an example of the plurality of sheets. However, the number of sheets is not limited to this as long as it is a plurality of sheets. It may be more than one.

  In the above-described embodiment, as shown in FIG. 6, no separate rolls are installed in the gap between the upper and lower embossing rolls 61 and 71 in the vicinity of the upper and lower embossing rolls 61 and 71. 33, a pressing roll 81 is arranged opposite to the lower embossing roll 71 while being positioned on the entry side of the gap, whereby the top sheet 14 is lowered on the entry side of the gap. You may make it press on the convex part 73 of the outer peripheral surface 71a of the embossing roll 71 previously. And according to such a structure, the surface sheet 14 pressed on the lower embossing roll 71 enters the space S between the convex portions 73 and 73 adjacent to each other in the lower embossing roll 71, and the amount of the intrusion is Since it increases, the bulkiness of the liquid-permeable sheet 17 can be improved further.

  In addition, whether the pressing roll 81 is provided for both the upper and lower embossing rolls 61 and 71, or for either one of the upper or lower embossing rolls, is relative to the liquid permeable sheet 17 to be manufactured. It is determined according to the required quality.

  For example, if a liquid-permeable sheet 17 having a high bulkiness is desired, it may be provided for both the upper and lower embossing rolls 61 and 71. However, as in the application example described above, the liquid-permeation of a sanitary napkin is possible. In the case of the adhesive sheet 17, as shown in FIG. 33, it is preferable to provide the pressing roll 81 only against the lower embossing roll 71 with which the topsheet 14 abuts. The reason for this is that the surface sheet 14 located on the skin side of the human body is good because the contact area is reduced and the touch is excellent if there are irregularities, but on the other hand, the intermediate sheet located on the absorber 12 side. Regarding the sheet 16, not only does the sheet surface not touch the skin even if the sheet surface has irregularities, it does not contribute to the touch, but conversely, if the sheet surface has irregularities, the contact portion with the absorber 12 This is because the liquid (menstrual blood) that has passed through the top sheet 14 is difficult to smoothly transfer to the absorber 12.

  Desirably, a convex portion (not shown in FIG. 33) is formed on the outer peripheral surface of the pressing roll 81 so as to correspond to the space S (FIG. 33) between the convex portions 73 adjacent to each other in the lower embossing roll 71. ), And the convex portion of the pressing roll 81 makes it easier for the topsheet 14 to enter the space S, thereby further improving the bulkiness of the liquid-permeable sheet 17. it can. For example, when the convex portion of the lower embossing roll 71 is a rib 74 as shown in FIG. 20, as shown in the perspective view of FIG. 34, it corresponds to the groove 74t as the space S between the adjacent ribs 74, 74. Thus, the rib 84 may be formed on the outer peripheral surface 81 a of the pressing roll 81.

It is a side view which shows the mode of the conventional embossing. It is a side view which shows the mode of the embossing. It is a side view which shows the mode of the embossing of an improvement measure. It is a schematic diagram for description of the problem of the embossing. 5A is a plan view of the surface side of the absorbent article 1, and FIG. 5B is a cross-sectional view taken along the line BB in FIG. 5A. 4 is a side view of a production line for the liquid permeable sheet 17. FIG. It is a front view of the joining apparatus 211. It is a front view of the upper embossing roll 61 and the lower embossing roll 71 which concern on 1st Embodiment. It is the figure which expand | deploys and shows the outer peripheral surfaces 61a and 71a of the upper embossing roll 61 and the lower embossing roll 71 in the circumferential direction. FIG. 10A is an explanatory diagram of the convex portion 63 of the upper embossing roll 61, and FIG. 10B is an explanatory diagram of the convex portion 73 of the lower embossing roll 71. 11A and 11B are explanatory diagrams of the relationship of the protrusion amount X1 between the top surface 63a of the convex portion 63 of the upper embossing roll 61 and the top surface 73a of the convex portion 73 of the lower embossing roll 71. FIG. It is explanatory drawing of the reason for the strength reduction of the joining recessed part 15 being prevented. It is a top view of the upper surface side and lower surface side of the liquid-permeable sheet 17 manufactured with the embossing rolls 61 and 71 which concern on 1st Embodiment. It is a front view of the upper embossing roll 61 and the lower embossing roll 71 which concern on 2nd Embodiment. It is the figure which expand | deploys and shows the outer peripheral surfaces 61a and 71a of the upper embossing roll 61 and the lower embossing roll 71 in the circumferential direction. It is a top view of the upper surface side and lower surface side of the liquid-permeable sheet 17 manufactured with the embossing rolls 61 and 71 which concern on 2nd Embodiment. It is a front view of the upper embossing roll 61 and the lower embossing roll 71 which concern on 3rd Embodiment. It is the figure which expand | deploys and shows the outer peripheral surfaces 61a and 71a of the upper embossing roll 61 and the lower embossing roll 71 in the circumferential direction. It is a top view of the upper surface side and lower surface side of the liquid-permeable sheet 17 manufactured with the embossing rolls 61 and 71 which concern on 3rd Embodiment. It is a front view of the upper embossing roll 61 and the lower embossing roll 71 which concern on 4th Embodiment. It is the figure which expand | deploys and shows the outer peripheral surfaces 61a and 71a of the upper embossing roll 61 and the lower embossing roll 71 in the circumferential direction. It is a top view of the upper surface side and lower surface side of the liquid-permeable sheet 17 manufactured with the embossing rolls 61 and 71 which concern on 4th Embodiment. It is a figure which expand | deploys and shows the outer peripheral surfaces 61a and 71a of the embossing rolls 61 and 71 of the modification concerning 4th Embodiment in the circumferential direction. It is a front view of the upper embossing roll 61 and the lower embossing roll 71 which concern on 5th Embodiment. It is the figure which expand | deploys and shows the outer peripheral surfaces 61a and 71a of the upper embossing roll 61 and the lower embossing roll 71 in the circumferential direction. It is a top view of the upper surface side and lower surface side of the liquid-permeable sheet 17 manufactured with the embossing rolls 61 and 71 which concern on 5th Embodiment. It is a front view of the upper embossing roll 61 and the lower embossing roll 71 which concern on 6th Embodiment. It is the figure which expand | deploys and shows the outer peripheral surfaces 61a and 71a of the upper embossing roll 61 and the lower embossing roll 71 in the circumferential direction. It is a top view of the upper surface side and lower surface side of the liquid-permeable sheet 17 manufactured with the embossing rolls 61 and 71 which concern on 6th Embodiment. It is a front view of the upper embossing roll 61 and the lower embossing roll 71 which concern on 7th Embodiment. It is the figure which expand | deploys and shows the outer peripheral surfaces 61a and 71a of the upper embossing roll 61 and the lower embossing roll 71 in the circumferential direction. It is a top view of the upper surface side and lower surface side of the liquid-permeable sheet 17 manufactured with the embossing rolls 61 and 71 which concern on 7th Embodiment. It is a side view for description of other embodiments. It is a perspective view for description of other embodiments.

Explanation of symbols

1 absorbent articles,
12 absorber, 14 surface sheet, 14r surface sheet roll,
15 joint recess, 15a groove, 15b groove, 15c joint recess,
16 intermediate sheet, 16r intermediate sheet roll, 17 liquid permeable sheet,
18 Back sheet, 18f wing part, 19 Underwear fixing adhesive,
20 side sheet, 61 upper embossing roll, 61a outer peripheral surface,
63 convex part, 63a top surface, 64 rib, 65 convex part, 65a top surface,
71 lower embossing roll, 71a outer peripheral surface, 73 convex portion, 73a top surface,
74 rib, 74t groove, 81 pressing roll, 81a outer peripheral surface, 84 rib,
201 reel, 203 reel,
211 Joining device, 213 housing, 217 lifting mechanism,
221 rotation drive mechanism, 223 motor, 225 pinion stand,
225a gear, 225b gear, 227a spindle, 227b spindle,
C61 rotation axis, C71 rotation axis, C63a top surface center, C73a,
P1 processing position, P2 processing position, S space

Claims (8)

A method of manufacturing a liquid-permeable sheet by joining a plurality of sheets by sandwiching and pressing the plurality of sheets in a gap between a pair of rolls rotating with the outer peripheral surfaces thereof facing each other and having their outer peripheral surfaces facing each other. Because
A plurality of convex portions are formed on the outer peripheral surface of one roll of the pair of rolls, and the plurality of convex portions are formed on the outer peripheral surface of the other roll in correspondence with the convex portions. A convex part for forming a joint concave part by sandwiching the sheets is formed,
The method for producing a liquid-permeable sheet, wherein the top surface of the convex portion of the one roll and the top surface of the convex portion of the other roll corresponding to the convex portion have different sizes in a predetermined direction. . A method for producing a liquid-permeable sheet according to claim 1,
The predetermined direction is a direction along the rotation axis,
The top surface of the convex portion of the one roll protrudes outside the top surface of the other convex portion on both sides in the direction along the rotation axis. Method. A method for producing a liquid-permeable sheet according to claim 2,
The method for producing a liquid-permeable sheet, wherein the convex portion of the one roll is a rib that continuously extends over the entire width of the plurality of sheets in a direction along the rotation axis. A method for producing a liquid-permeable sheet according to any one of claims 1 to 3,
The predetermined direction is a circumferential direction of the roll,
The top surface of the convex portion of the other roll protrudes outward from the top surface of the one convex portion on both sides in the circumferential direction of the roll. . It is a manufacturing method of the liquid-permeable sheet according to claim 4,
The method for producing a liquid-permeable sheet, wherein the convex portion of the other roll is a rib extending continuously over the entire length in the circumferential direction. A method for producing a liquid-permeable sheet according to any one of claims 1 to 5,
A liquid permeable sheet characterized in that a pressing roll for pressing at least one of the plurality of sheets against a convex portion of the roll is provided on the entry side of the gap of the roll. Production method. It is a manufacturing method of the liquid-permeable sheet according to claim 6,
The liquid permeable sheet is a sheet for covering from the skin side of the human body an absorber that absorbs liquid excreted from the human body,
The plurality of sheets are composed of a surface sheet positioned on the skin side when worn, and an intermediate sheet positioned on the absorber side,
The method for producing a liquid-permeable sheet, wherein the pressing roll is provided only to a roll that contacts the top sheet in the gap in the pair of rolls. An apparatus for manufacturing a liquid-permeable sheet by joining a plurality of sheets by sandwiching and pressing the plurality of sheets into a gap between a pair of rolls rotating with their outer peripheral surfaces aligned in parallel and facing the outer peripheral surfaces. Because
A plurality of convex portions are formed on the outer peripheral surface of one roll of the pair of rolls, and the plurality of convex portions are formed on the outer peripheral surface of the other roll in correspondence with the convex portions. A convex part for forming a joint concave part by sandwiching the sheets is formed,
The liquid-permeable sheet manufacturing apparatus, wherein the top surface of the convex portion of the one roll and the top surface of the convex portion of the other roll corresponding to the convex portion have different sizes in a predetermined direction. .