Patent Description:
A known configuration of a mask to be worn on the face includes: a mask body that at least partially covers the face of a wearer; and ear hook portions, constituting a pair, each being coupled to the mask body, i.e., a pair of members that can be hung on the ears of the wearer in order to hold the mask body at a wearing position.

A sheet-shaped ear hook used for a mask is known. For example, a mask disclosed in PTL <NUM> includes a single sheet-shaped ear hook sheet extending on the same plane with both ear hook portions connected to each other at the connection portion. PTL <NUM> indicates that the ear hook portion is made of a stretchable spunbond nonwoven fabric or the like.

PTL <NUM>: <CIT>
Document <CIT>, which discloses the preamble of claim <NUM>, relates to a mask that comprises a main body part for covering the nasal cavity and mouth and a hooking part for hooking the main body part to the body. The hooking part comprises a sheet-like material, an elastic member fixed to the sheet-like material in an extended state and wrinkles, formed when the sheet-like material is contracted, accompanying the elastic contraction of the elastic member.

Document <CIT> concerns an absorbent article including a stretchable sheet that is a laminate of a non-stretchable first sheet layer, a non-stretchable second sheet layer, and an elastic film disposed between the first and second sheet layers, and the elastic film is stretchable at least in the front-back direction. The first sheet layer is bonded to the second sheet layer at a large number of joints directly or through the elastic film and the joints are arrayed at intervals. The stretchable sheet is contracted by a contraction force of the elastic film and can be stretched by an external force applied in the front-back direction. The leg portion is also contracted by a contraction force of the elastic film and can be stretched by an external force applied in the width direction.

It is preferable that a portion of the sheet-shaped ear hook portion which extends in the left-and-right direction of the face as disclosed in PTL <NUM> is easily stretched when being put on. It is preferable that the portion of the ear hook portion situated behind the ear when the mask is put on (while the mask is worn) is not stretched and deformed so much, because the state of contact with the skin behind the ear can be stably maintained. Therefore, it is desirable that the stretching characteristic or the deformation characteristic of the sheet-shaped ear hook portion is different depending on the position in order to improve the ease of wearing and fit. However, such a study has not been made in the past.

In view of the above, it is an object of the invention to provide an ear hook portion for a mask that is improved in ease of wearing and fit. This object is solved by the subject-matters of the independent claims. Further embodiments are the subject of the further claims. Thus, the present invention is set out by the set of appended claims. In the following, parts of the description and drawing referring to examples, which are not covered by the claims are not presented as embodiments of the invention, but as illustrative examples useful for understanding the invention. Means for Solving the Problem.

The present invention relates to an ear hook portion for mask, the ear hook portion being made of a material including: a stretchable portion material; and a first surface sheet material and a second surface sheet material coupled, via a plurality of coupling portions, to both surfaces of the stretchable portion material in such a state that the stretchable portion material is stretched, the ear hook portion including: a proximal portion fixed to a mask body; an ear back placement portion to be situated at a back of an ear of a wearer; an upper transition portion extending, on an upper side, from the proximal portion to the ear back placement portion; and lower transition portion transitioning, on a lower side, from the proximal portion to the ear back placement portion, wherein a number of the plurality of coupling portions per unit area in the ear back placement portion is greater than a number of the plurality of coupling portions per unit area in each of the upper transition portion and the lower transition portion.

According to the invention an ear hook portion for a mask that is improved in ease of wearing and fit can be provided.

Hereinafter, examples of the present disclosure are described in detail with reference to the drawings. In each of the drawings, unless otherwise explained, the same or corresponding components may be denoted with the same reference numerals and the description thereof may be omitted. The drawings are schematic for helping understanding of the disclosure.

First, a basic configuration of a mask according to the present embodiment is explained. The mask according to the present embodiment may be a mask capable of covering the face of a wearer, more specifically, covering at least the nose and the mouth of a wearer. The mask according to this embodiment can have a function of preventing foreign matter from reaching the face and preventing droplets generated by the wearer from being scattered, and is also referred to as a sanitary mask or surgical mask.

<FIG> is a plan view of a mask <NUM>. <FIG> is a view of the mask <NUM> as seen from the outside, i.e., from the side exposed to the outside and facing away from the face when the mask <NUM> is worn. <FIG> is a plan view of the mask <NUM> as seen from the inside (face side). Furthermore, <FIG> is a cross-sectional view taken along line I-I of <FIG>.

As illustrated in <FIG>, the mask <NUM> according to the present example includes: a mask body <NUM> which is disposed in front of the face of the wearer when the mask is worn and can mainly cover the nose and mouth of the wearer; and ear hook portions 20a, 20a, constituting the pair, coupled to the mask body <NUM>. The mask body <NUM> has a height direction (height direction) D1 corresponding to the height direction of the wearer's face when wearing the mask and a left-and-right direction (left-and-right direction) D2 orthogonal to the height direction D1. In the form of <FIG>, the mask body <NUM> has a rectangular shape in a plan view having long sides in the left-and-right direction D2, but the shape of the mask body <NUM> in a plan view is not limited to the shape as illustrated in the drawings.

As illustrated in <FIG> and <FIG>, the mask body <NUM> has a pleated structure <NUM> formed by multiple pleats arranged side by side in the height direction D1. The pleats of the pleated structure <NUM> are formed by folding a sheet constituting the body <NUM> at fold lines along the left-and-right direction D2. In a state in which multiple pleats are formed, the side portions (the ends in the left-and-right direction D2) of the mask body <NUM> are joined and fixed by pressure bonding or the like. Therefore, when the mask <NUM> is used, the pleats of the pleated structure <NUM> are extended in the height direction D1, so that the center in the left-and-right direction D2 is curved so as to protrude toward the outer surface side of the mask <NUM>, and can be deformed into a shape adapted to the three-dimensional shape of the face. The specific configuration of the pleated structure <NUM> is not particularly limited and may be a conventional configuration formed in a mask body.

The mask body <NUM> may have a multilayer structure formed by laminating multiple layers. For example, the structure may include at least three layers sandwiched between an outer layer and an inner layer of an intermediate layer having an enhanced function of collecting a foreign matter (dust, pollen, bacteria, viruses, and the like). Each layer constituting the mask body <NUM> preferably includes a fiber-containing layer such as a nonwoven fabric, a woven fabric, a knitted fabric, and the like, and more preferably includes a nonwoven fabric. Examples of the nonwoven fabric include a spunbond nonwoven fabric, a spunlace nonwoven fabric, a meltblown nonwoven fabric, an air through nonwoven fabric, a point bond nonwoven fabric, and the like. A meltblown nonwoven fabric which can contain fine fibers is preferably used for the intermediate layer. The fibers constituting the fiber-containing layer are preferably resin fibers, and the resin types of the resin fibers include polyethylene, polypropylene, polyethylene terephthalate, nylon, and the like. The basis weight of the outer and inner layers may be <NUM> to <NUM>/m<NUM>, preferably <NUM> to <NUM>/m<NUM>. The basis weight of the intermediate layer having a high foreign matter collecting property is preferably <NUM> to <NUM>/m<NUM> and more preferably <NUM> to <NUM>/m<NUM>.

The ear hook portions 20a, 20a, constituting the pair, may be in an annular shape (or in a closed belt shape), or may have a shape that includes an annulus in a plan view. When being worn, the ear hook portions 20a can be hung on the ears by allowing the ears of the wearer to enter the inside of the ring of each ear hook portion 20a, i.e., an opening <NUM> at the center of each ear hook portion 20a.

As illustrated in <FIG> and <FIG>, the ear hook portions 20a, 20a, constituting the pair, is formed as a single sheet-shaped or a continuous ear hook portion sheet <NUM> in which the ear hook portions 20a, 20a are separably coupled to each other at the center in the left-and-right direction D2. In this case, the term "single sheet" herein refers to a form composed of one continuous sheet, and the "single sheet" is a concept that can include a stacked body in which multiple layers are stacked. The ear hook portions 20a, 20a, constituting the pair, are in a sheet form, and therefore, when the ear hook portion 20a is hung on the ear, the ear hook portion 20a can be brought into surface contact with the back surface behind the ear (or the back of the ear), i.e., the skin on the rear side with respect to the ear and/or the back of the earlobe, so that the load on the ear can be reduced. Accordingly, even when worn for a long period of time, pain and discomfort can be reduced. Furthermore, because the ear hook portions 20a, 20a, constituting the pair, are in a sheet form (i.e., constituted by the ear hook portion sheet <NUM>), the ear hook portions 20a, 20a, constituting the pair, can be positioned at the same time during manufacturing, and therefore, manufacturing of the mask is also easy.

The ear hook portion sheet <NUM> is configured so as to be able to form the ear hook portions 20a, 20a, constituting the pair, separated from each other by breaking the ear hook portion sheet <NUM> at a predetermined position at the start of use. Specifically, in the form of <FIG>, the ear hook portions 20a, 20a, constituting the pair, are coupled by a coupling portion <NUM>. The type of coupling at a separable coupling portion <NUM> between the ear hook portions 20a, 20a constituting the pair is not particularly limited, but is preferably separable by pulling with a usual force of the user. For example, it may be formed as perforations as illustrated in <FIG>. The coupling portion <NUM> may also be formed by reducing the thickness of the sheet or by other means to weaken the border between the ear hook portions 20a, 20a constituting the pair or to increase stress.

As illustrated in <FIG>, the ear hook portions 20a, 20a, constituting the pair, or the ear hook portion sheet <NUM> in a single sheet shape are superposed on the mask body <NUM>. The ear hook portion sheet <NUM> may have a shape and a size that does not protrude from the mask body <NUM> at least in the left-and-right direction D2 in a plan view. With this configuration, a length of the ear hook portion sheet <NUM> in the left-and-right direction D2 may be <NUM> to <NUM>% of the length of the mask <NUM> in the left-and-right direction D2. With such configuration, masks can be continuously manufactured by superposing and coupling the mask body <NUM> and the ear hook portion sheet <NUM> without requiring complicated processes such as folding and bending of the ear hook portion sheet <NUM>. The length of one ear hook portion 20a in the left-and-right direction D2 is <NUM> to <NUM>, preferably <NUM> to <NUM>.

The ear hook portions 20a, 20a, constituting the pair, may be directly or indirectly coupled to side portions (end portions in the left-and-right direction D2) of the body <NUM>. Specifically, the portions on the outer sides of the ear hook portions 20a, 20a, constituting the pair, in the left-and-right direction D2 are connected to the body <NUM>, and the other portions are not connected to the body <NUM>. To start to use the mask <NUM> according to the present example, before putting on the mask <NUM>, the user releases the coupling, at the coupling portion <NUM>, between the ear hook portions 20a, 20a, constituting the pair, separates the ear hook portions 20a, 20a from each other (also referred to as a separation operation), and opens, sideways in the left-and-right direction D2, the portions of the ear hook portions 20a, 20a that are not coupled to the body <NUM> (also referred to as an expansion operation).

As illustrated in <FIG> and <FIG>, the ear hook portions 20a, 20a, constituting the pair, may be coupled to both side portions of the mask body <NUM> via sheet-shaped auxiliary materials <NUM>, <NUM>, respectively. By interposing the auxiliary material <NUM> in the coupling between the ear hook portion 20a and the mask body <NUM>, the mask <NUM> can be formed without directly coupling the ear hook portion 20a and the mask body <NUM>. Therefore, the coupling between the ear hook portion 20a and the auxiliary material <NUM> and the coupling between the mask body <NUM> and the auxiliary material <NUM> can be formed separately in appropriate forms. In addition, it is possible to avoid using a portion of the ear hook portion 20a for fixation with the mask body <NUM>. Therefore, by using the auxiliary material <NUM>, the ear hook portion 20a can be moved more freely relative to the mask body <NUM> than in the case where the ear hook portion 20a is directly coupled to the mask body <NUM>, and the position of the ear hook portion 20a relative to the ear can be set more freely when the ear hook portion 20a is attached to the ear. In the form illustrated in <FIG>, the mask body <NUM> and the sheet-shaped auxiliary material <NUM> are superposed and coupled at a first side coupling portion <NUM>. The sheet-shaped ear hook portion 20a and the sheet-shaped auxiliary material <NUM> are superposed and coupled at a second side coupling portion <NUM>.

The auxiliary material <NUM> may be a sheet-shaped member extending in the entire height direction D1 of the mask <NUM>. The length (width) W of the auxiliary material <NUM> in the left-and-right direction D2 is preferably <NUM> to <NUM>, depending on the size and configuration of the entire mask <NUM> and the sizes, shapes, and materials of the body <NUM> and the ear hook portions 20a. The basis weight of the auxiliary material <NUM> may be <NUM> to <NUM>/m2. The thickness of the auxiliary material <NUM> may be <NUM> to <NUM>,<NUM>.

The auxiliary material <NUM> may be formed of a non-stretchable material or a material with small stretchability, or may be formed of a material having a certain degree of stretchability. The auxiliary material <NUM> may include, for example, a stretchable nonwoven fabric. In this case, the auxiliary material <NUM> is preferably stretchable at least in the left-and-right direction D2, but the stretchability of the auxiliary material <NUM> is preferably smaller than that of the ear hook portion 20a. The auxiliary material <NUM> may be formed of a material whose shape can be irreversibly deformed when a force is applied.

For example, the first side coupling portion <NUM> and the second side coupling portion <NUM> can be formed by means of coupling the opposing surfaces of the members by applying pressure and/or heat, such as heat sealing, ultrasonic sealing, non-heating embossing, and the like. Among them, it is preferable to use heat sealing because reliable bonding is possible.

When the auxiliary material <NUM> is provided, the length in the left-right direction D2 of the ear hook portion sheets <NUM> constituting the pair of ear hook portions 20a, 20a is shorter than the length in the left-right direction D2 of the mask <NUM>. As a result, an outer end <NUM> of the ear hook portion 20a in the left-right direction D2 and an outer end <NUM> of the body <NUM> in the left-right direction D2 can be shifted, so that the auxiliary material <NUM> can be pasted to a position in proximity to the end portion of the mask body <NUM> in the left-right direction D2 that is not covered with the ear hook portion 20a.

At the start of use of the mask <NUM>, the user can pull the ear hook portions 20a, 20a constituting the pair in the opposite directions by pinching or holding them with their respective hands. As a result, the separable coupling portion <NUM> can be first uncoupled. If the coupling portion <NUM> includes perforations formed along the border line between the ear hook portions 20a, 20a constituting the pair, the perforations can be broken to separate the ear hook portions 20a, 20a along the border line. Thereafter, the user can open the ear hook portions 20a, 20a constituting the pair outward (as indicated by arrows) in the left-and-right direction D2 toward the sides indicated by the arrows in <FIG> while holding the ear hook portions 20a, 20a, constituting the pair.

<FIG> illustrates a state in which the ear hook portions 20a, 20a, constituting the pair, are opened outward in the left-and-right direction D2 from the state illustrated in <FIG>. <FIG> is a cross-sectional view taken along line II-II of <FIG>. As illustrated in <FIG> and <FIG>, when the ear hook portions 20a, 20a constituting the pair are opened, the ear hook portions 20a, 20a are turned over, i.e., the surface of the ear hook portions 20a, 20a constituting the pair facing the body <NUM> in the state before start of use is exposed.

After the user holds the ear hook portions 20a, 20a, constituting the pair, and opens them outward in the left-and-right direction D2, the mask body <NUM> is placed on the face of the wearer so that the surface on the face side of the mask body <NUM> faces the face of the wearer, and the ear hook portions 20a, 20a are hung on the respective ears of the wearer.

In the state before start of use (<FIG>), the ear hook portions 20a, 20a, constituting the pair, (the ear hook portion sheet <NUM>) in the form of a single sheet are superposed on the mask body <NUM>. The ear hook portions 20a, 20a, constituting the pair, may be superposed on any of the surfaces of the mask body <NUM>, but it is preferable that they are superposed on the outer surface of the mask body <NUM> as illustrated in the drawing. Thus, when the mask <NUM> is worn, the contact with the inner surface (surface on the face side) of the mask body <NUM> can be reduced or substantially eliminated.

For example, when the user puts the mask <NUM> on himself/herself, the mask <NUM> is placed on his/her face so that the inner surface of the mask body <NUM> faces his/her face, and while pressing the outer surface of the mask body <NUM> with one hand, the coupling of the ear hook portions 20a, 20a at the coupling portion <NUM> is released by the other hand, and one ear hook portion 20a is hung on the ear. After switching the hand holding the mask body <NUM> to the other hand, the other ear hook portion 20a can be hung on the ear with the hand that was originally holding the mask body <NUM>.

Also, while the mask <NUM> is placed with the outside of the mask <NUM> facing upward (with the outer surface of the body <NUM> facing upward), the user opens the ear hook portions 20a, 20a, constituting the pair, outwardly in the left-and-right direction D2 by holding them with hands. Thereafter, the mask <NUM> is moved to the face of another wearer while the ear hook portions 20a, 20a constituting the pair are held, and the mask body <NUM> is arranged at a desired position of the wearer's face, and at this occasion, the ear hook portions 20a, 20a constituting the pair can be hung on the ears of the wearer while the way of holding the mask <NUM> is not changed. Therefore, the mask <NUM> according to the present example can be suitably used when the mask is worn by a person who has difficulty wearing the mask by himself or herself, such as a child or a sick person.

To hold the ear hook portions 20a, 20a, the user may also hold the tab portions <NUM>, <NUM> protruding outward from the respective rings of the ear hook portions 20a, 20a in a plan view. By handling the ear hook portions 20a, 20a by holding the tab portions <NUM>, <NUM>, it is possible to perform the separation operation and the expansion operation of the mask more hygienically. As illustrated in <FIG>, it is preferable that the tab portions <NUM>, <NUM> protrude beyond the outer edge of the mask body <NUM>, particularly beyond the lower end of the mask body <NUM>.

A mark <NUM> that allows front and back (the outer and inner surfaces) of the body <NUM> to be distinguished from each other may be formed on the outer surface and/or the inner surface of the body <NUM> by embossing, printing, sewing, or the like. The form of the mark <NUM> is not limited as long as it can be visually recognized by the user. As illustrated in <FIG> and <FIG>, the mark <NUM> may be letters, numbers, a symbol, a figure, a logo, or the like. If the mark <NUM> includes characters, the side on which the user can read the characters correctly can be recognized as the outer surface.

<FIG> describe an embodiment of the invention. <FIG> is a partially enlarged cross-sectional view of a material constituting the ear hook portion 20a or the ear hook portion sheet <NUM> taken along the left-and-right direction D2. As illustrated in <FIG>, the material constituting the ear hook portion 20a or the ear hook portion sheet <NUM> may be a sheet obtained by laminating multiple layers. In the example of <FIG>, the material is provided with a stretchable material (a stretchable film) <NUM>, and a first surface sheet material <NUM> is provided on a first surface that is one of the surfaces of the stretchable material (a stretchable film) <NUM>, and a second surface sheet material <NUM> is provided on a second surface that is a surface on the side opposite from the first surface. The stretchable portion material is a portion material that can be stretched in at least one direction by applying a tensile force, and that has a property of returning to an original length (natural length) when the applied tensile force is released (an external force is not applied).

As illustrated in <FIG>, in this example, a stretchable film <NUM> is used as a stretchable portion material. Examples of materials of the stretchable film <NUM> include polyolefin such as polyethylene and polypropylene, polyurethane, and the like. With respect to the stretchability of the stretchable film <NUM>, it is preferable that the maximum stretch rate is <NUM> to <NUM> times the natural length, as measured by a tensile testing machine. The stretchable film <NUM> may have a function of allowing moisture to pass through.

In place of the stretchable film, a thread-like stretchable body aggregate formed by arranging side by side multiple thread-like stretchable bodies (or thread-like elastic bodies) such as yarn rubber may be provided. However, a stretchable portion member in the form of a film, i.e., a film in the form of a flat molded body having a substantially uniform thickness, is preferable in that high stretchability or extensibility is obtained and handling during manufacture is easy.

Specifically, in the material illustrated in <FIG>, the first surface sheet material and the second surface sheet material are coupled to both surfaces (the first surface and the second surface) of the stretchable film <NUM> by multiple coupling portions <NUM>, <NUM>,. , in a state where the stretchable film <NUM> is stretched. In order to obtain the material illustrated in <FIG>, first, as illustrated in <FIG>, a tensile external force T is applied to the stretchable film <NUM> to stretch the stretchable film <NUM> from its natural length, and the first surface sheet material <NUM> and the second surface sheet material <NUM> are intermittently coupled at multiple coupling portions <NUM>, <NUM>,. (to be described later) in the natural state in which the first surface sheet material <NUM> and the second surface sheet material <NUM> are not shrunk. Thereafter, the tensile external force T is released to relax the stretchable film <NUM>, so that the material in the natural state illustrated in <FIG> is obtained.

The state of the material illustrated in <FIG> is the natural state, i.e., a state in which no external force is applied (a state having a natural length). In this state, the first surface sheet material <NUM> and the second surface sheet material <NUM>, which are flat when the tensile external force T illustrated in <FIG> is applied, are formed with wrinkles (pleats), and are wavy in a cross section (<FIG>). This is because, when the length of the stretchable film <NUM> returns to the natural length, portions other than the portions coupled by the multiple coupling portions <NUM>, <NUM>,. rise so as to be separated from the stretchable film <NUM>.

In this manner, a large number of pleats are formed on the surface of the ear hook portion 20a (the ear hook portion sheet <NUM>). Therefore, when the surface of the ear hook portion 20a comes into contact with the skin, the material of the ear hook portion 20a does not come into contact with the entire surface of the skin, and a space is formed between the ear hook portion 20a and the skin, so that the feeling of sticking to the skin can be reduced and the fit can be improved. When the ear hook portion 20a (the ear hook portion sheet <NUM>) is formed of the material, the stretch direction (extension direction) of the stretchable film <NUM> is configured to follow the left-and-right direction D2 of the mask. As a result, multiple wrinkles extending approximately along the height direction D1 of the mask <NUM> are formed on the surface of the ear hook portion 20a (the ear hook portion sheet <NUM>).

The first surface sheet material <NUM> and the second surface sheet material <NUM> may be the same or different. The first surface sheet material <NUM> and the second surface sheet material <NUM> preferably have a fiber structure. Examples of the fiber structures include a nonwoven fabric, a woven fabric, a knitted fabric, and the like. Among them, a nonwoven fabric is preferably used because of its good touch and breathability, and it contributes to the fit. Examples of nonwoven fabric include an air-through nonwoven fabric, a spunbond nonwoven fabric, a spunlace nonwoven fabric, a needle punch nonwoven fabric, a chemical bond nonwoven fabric, and the like. Among them, a spunbond nonwoven fabric having no pilling and high strength, an air-through nonwoven fabric having softness, and the like can be suitably selected. The fibers contained in the nonwoven fabric are preferably resin fibers, and the resin types of the resin fibers include polyethylene, polypropylene, polyethylene terephthalate, nylon, and the like. In a case where the first surface sheet material <NUM> or the second surface sheet material <NUM> is nonwoven fabric, the basis weight of the nonwoven fabric may be <NUM> to <NUM>/m<NUM>, and more particularly, preferably <NUM> to <NUM>/m<NUM>.

When the ear hook portion 20a according to the present example is made of a material in which both surfaces of the stretchable film <NUM> are covered by the first surface sheet material <NUM> and the second surface sheet material <NUM>, direct contact between the stretchable film <NUM> and the skin can be avoided when the mask is worn, and the fit can be improved.

The coupling portions <NUM>, <NUM>,. can be formed by using fusing means such as ultrasonic sealing or heat sealing, or by using an adhesive or the like, but it is preferable to form the coupling portions by fusing means, especially by ultrasonic sealing, because it enables more reliable bonding. In the present example, the first surface sheet material <NUM>, the stretchable film <NUM>, and the second surface sheet material <NUM> all contain a thermoplastic resin or are made of a thermoplastic resin, and therefore, at the coupling portions (fused portions) <NUM>, <NUM>,. , the three layers are fused and integrated by welding the layers together. Depending on the formation conditions of the fused portion, a through hole may be formed in the bonded portion. In this case, the breathability y of the ear hook portion 20a (the ear hook portion sheet <NUM>) can be improved.

<FIG> is a plan view of the ear hook portions 20a, 20a (the ear hook portion sheet <NUM>) according to a present embodiment of the invention. As illustrated in <FIG>, the ear hook portion 20a may be in an annular shape (or in a closed belt shape) in a plan view, or may have a shape that includes an annulus. The ear hook portion 20a includes a proximal portion <NUM> fixed to the mask body <NUM> (coupled to the mask body <NUM> via the auxiliary material in the form of <FIG>), an ear back placement portion <NUM> situated behind the ear of the wearer, an upper transition portion <NUM> transitioning, above the ear hook portion 20a, from the proximal portion <NUM> to the ear back placement portion <NUM>, and a lower transition portion <NUM> transitioning, below the ear hook portion 20a, from the proximal portion <NUM> to the ear back placement portion <NUM>. The proximal portion <NUM> and the ear back placement portion <NUM> extend substantially along the height direction D1 and are opposed to each other. The upper transition portion <NUM> and the lower transition portion <NUM> extend approximately along the left-and-right direction D2 and face each other.

In the embodiment illustrated in <FIG>, the shape of the ring included in the ear hook portion 20a is generally a rectangular belt shape, but may be generally a circular or elliptical shape. The ear hook portion 20a may have a shape having three places where the direction is greatly changed along the circumferential direction of the ring (i.e., a triangular belt shape) or a shape having five or more such places (i.e., a polygonal belt shape other than the rectangular belt shape).

The ear hook portions 20a, 20a (the ear hook portion sheet <NUM>) are made of the material described above, i.e., a material including: the stretchable portion member <NUM>; and the first surface sheet material <NUM> and the second surface sheet material <NUM> coupled to each other by multiple coupling portions <NUM>, <NUM>,. in a state where the stretchable portion member <NUM> is stretched. However, as illustrated in <FIG>, the distribution of the multiple coupling portions <NUM>, <NUM>,. is not uniform. Specifically, the ear hook portions 20a, 20a include: sparse distribution areas R1A, R1B (which may be collectively referred to as R1) in which the coupling portions <NUM>, <NUM>,. are sparsely distributed; and a dense distribution area R2 in which the coupling portions <NUM>, <NUM>,. are more densely distributed. It is preferable that the sparse distribution areas R1A, R1B have the same configuration.

<FIG> is a partially enlarged plan view of the sparse distribution areas R1A, R1B. <FIG> is a partially enlarged plan view of the dense distribution area R2. As illustrated in <FIG>, in the dense distribution area R2, the density of the formed coupling portions <NUM>, <NUM>,. , i.e., a number N<NUM> per unit area, is greater than the density of the coupling portions <NUM>, <NUM>,. formed in the sparse distribution areas R1A, R1B, i.e., a number N<NUM> per unit area. The number per unit area is the number measured in the maximum stretched state of the ear hook portion 20a or the ear hook portion sheet <NUM>. The maximum stretched state refers to a state in which the surface sheet material becomes a natural length by stretching the ear hook portion 20a or the ear hook portion sheet <NUM>, i.e., a state in which the wrinkles of the surface sheet material are not substantially seen.

As illustrated in <FIG>, the ear back placement portion <NUM> may have the dense distribution area R2, the upper transition portion <NUM> may have the upper sparse distribution area R1A, and the lower transition portion <NUM> may have the lower sparse distribution area R1B. Furthermore, the ear back placement portion <NUM> may include the dense distribution area R2, the upper transition portion <NUM> may include the upper sparse distribution area R1A, and the lower transition portion <NUM> may include the lower sparse distribution area R1B. Therefore, the number of coupling portions per unit area in the ear back placement portion <NUM> is greater than the number of coupling portions per unit area in the upper transition portion <NUM> and greater than the number of coupling portions per unit area in the lower transition portion <NUM>.

In the embodiment illustrated in <FIG>, the proximal portion <NUM> also includes the dense distribution area R2, and the proximal portion <NUM> does not necessarily have the dense distribution area R2. However, in a case where both the proximal portion <NUM> and the ear back placement portion <NUM> have the dense distribution area R2, it is preferable that the ear hook portion sheet <NUM> is manufactured easily. Specifically, the belt-shaped dense distribution area R2 can be continuously formed along the conveying direction (corresponding to the left-and-right direction D2) of the ear hook portion sheet band 20A serving as the ear hook portion sheet <NUM> (explained later with reference to <FIG> and <FIG>). The sparse distribution areas R1A, R1B can also be formed in a continuous belt shape along the conveying direction on both sides of the dense distribution area R2 in the belt shape.

The fact that the coupling portion is formed more densely in the ear back placement portion <NUM> means that the first surface sheet material <NUM>, the stretchable portion member <NUM>, and the second surface sheet material <NUM> are fixed together at more positions per unit area in the ear back placement portion <NUM>. Therefore, the ear back placement portion <NUM> has a relatively large resistance to stretching and is not easily stretched. Since the ear back placement portion <NUM> is usually worn such that it is in surface contact with the back of the ear, i.e., the skin on the rear side with respect to the ear and/or the back of the earlobe, and therefore, when the ear back placement portion <NUM> is greatly stretched and deformed, discomfort may occur due to friction with the skin. However, according to the above configuration of the present example, such discomfort can be reduced.

Furthermore, because the coupling portion is formed more densely, the first surface sheet material <NUM>, the stretchable portion member <NUM>, and the second surface sheet material <NUM> are less likely to be detached, and the strength of the ear back placement portion <NUM> is increased. Therefore, even if a relatively large force is applied to the vicinity of the coupling portion <NUM> in the separation operation of the ear hook portions 20a, 20a, constituting the pair, the structure of the material is less likely to be broken.

In contrast, in the upper transition portion <NUM> and the lower transition portion <NUM>, which are arranged along the left-and-right direction D2 of the face when worn, the coupling points are formed more sparsely, and this means that the number of positions where the first surface sheet material <NUM>, the stretchable portion member <NUM>, and the second surface sheet material <NUM> are fixed together is relatively small per unit area. Therefore, the upper transition portion <NUM> and the lower transition portion <NUM> have a relatively small resistance to tension and are easily stretched. Therefore, while putting on the mask, it is possible to smoothly carry out the operation of hanging the ear hook portions 20a, 20a on the ear, in which the upper transition portion <NUM> and the lower transition portion <NUM> can be stretched in the left-and-right direction D2 with a relatively small force.

In this way, the densities of the coupling portions <NUM>, <NUM>,. are changed to change the stretching characteristic depending on the position of the ear hook portion 20a, so that the fit can be improved by reducing discomfort while being worn, and the operating for putting on the mask is facilitated.

When the ear hook portion sheet <NUM> is cut into a predetermined shape from a material having the stretchable film <NUM> sandwiched between the first surface sheet material <NUM> and the second surface sheet material <NUM> as in the present embodiment the edge portion of the stretchable film <NUM> is easily pulled inward from the edge portion of the first surface sheet material <NUM> and the edge portion of the second surface sheet material <NUM> due to compressive stress acting in the surface direction at the cutting position. In this case, since the first surface sheet material <NUM> and the second surface sheet material <NUM> project from the edge, they can be easily detached off from the edge. In particular, in the center of the ear hook portion sheet <NUM> in the left-right direction D2, i.e., in the ear back placement portion <NUM>, the edge is likely to come into contact with the skin, so that the possibility of detachment can be higher than other portions of the ear hook portion 20a. Therefore, since the ear back placement portion <NUM> has the dense distribution area R2 having a large number of coupling portions <NUM>, <NUM>,. per unit area, the above described drawing-in of the stretchable film <NUM> hardly occurs, and the ear back placement portion <NUM> hardly breaks. Furthermore, if the first surface sheet material <NUM> and the second surface sheet material <NUM> protrude from the edge, the appearance may be reduced, but if the stretchable film <NUM> can be prevented from being pulled in the ear back placement portion <NUM>, which is conspicuous, the appearance of not only the ear hook portions 20a, 20a but also the entire mask <NUM> can be improved.

The number N<NUM> per unit area of the coupling portions <NUM>, <NUM>,. in the dense distribution area R2 is preferably <NUM> to <NUM> pieces/cm<NUM>, and more preferably <NUM> to <NUM> pieces/cm<NUM>. The number N<NUM> per unit area of the coupling portions <NUM>, <NUM>,. in the sparse distribution area R1 may be <NUM> to <NUM> pieces/cm<NUM>, and more preferably <NUM> to <NUM> pieces/cm<NUM>. The ratio (N<NUM>/N<NUM>) of the number N<NUM> per unit area of the coupling portions <NUM>, <NUM>,. in the dense distribution area R2 to the number N<NUM> per unit area of the coupling portions <NUM>, <NUM>,. in the sparse distribution area R1 preferably <NUM> to <NUM>, and more preferably <NUM> to <NUM>.

Furthermore, as illustrated in <FIG>, the area S<NUM> of each one of the coupling portions <NUM> in the dense distribution area R2 may be smaller than the area S<NUM> of each one of the coupling portions <NUM> in the sparse distribution area R1. Furthermore, the ear back placement portion <NUM> includes the dense distribution area R2, and therefore, the upper transition portion <NUM> includes the upper sparse distribution area R1A, and the lower transition portion <NUM> includes the lower sparse distribution area R1B, and therefore, the area of each one of the coupling portions in the ear back placement portion <NUM> may be smaller than the area of each one of the coupling portions in the upper transition portion <NUM> and smaller than the area of each one of the coupling portions in the lower transition portion <NUM>.

Thus, the area S2 of each one of the coupling portions <NUM> in the dense distribution area R2 is small, and therefore, deformation such as curving or bending of the entire dense distribution area R2 can be performed more freely. Since the ear back placement portion <NUM> includes the dense distribution area R2, the ear back placement portion <NUM> can be deformed to conform to the shape of the portion behind the ear of the user and/or the shape of the ear. Furthermore, if the area of each one of the coupling portions is excessively large, the user may feel the hardness when it comes into contact with the skin, which may lead to discomfort. Therefore, the unpleasantness or discomfort can be reduced by reducing the area S<NUM> of each one of the coupling portions <NUM> in the ear back placement portion <NUM> pressed against the portion behind the ear and/or the back side of the ear.

Furthermore, the area of the coupling portion being small means that the peripheral length per area of the coupling portion is long. When a force is exerted such that the first surface sheet material <NUM>, the stretchable portion member <NUM>, and the second surface sheet material <NUM> are detached from each other, the detaching starts at the peripheral edge of the coupling portion where the coupling portion is particularly strongly coupled, and therefore, since the peripheral length per area of the coupling portion is long, resistance to detachment of the first surface sheet material <NUM>, the stretchable portion member <NUM>, and the second surface sheet material <NUM> from each other at the initial stage also increases. Therefore, the ear back placement portion <NUM> including the dense distribution area R2 can be configured to be less likely to be detached and to be stronger.

The area S2 of each one of the coupling portions <NUM> in the dense distribution area R2 is preferably <NUM> to <NUM><NUM>, more preferably <NUM> to <NUM><NUM>. The area S1 of each one of the coupling portions <NUM> in the sparse distribution area R1 is preferably <NUM> to <NUM><NUM>, more preferably <NUM> to <NUM><NUM>. The ratio (S2/S1) of the area S2 of each one of the coupling portions <NUM> in the dense distribution area R2 to the area S1 of each one of the coupling portions <NUM> in the sparse distribution area R1 is preferably <NUM> to <NUM>, and more preferably <NUM> to <NUM>.

Furthermore, as illustrated in <FIG>, a pitch px2 in the left-and-right direction D2 between the coupling portions <NUM>, <NUM>,. in the dense distribution area R2 may be smaller than a pitch px1 in the left-and-right direction D2 of the coupling portions <NUM>, <NUM>,. in the sparse distribution area R1. The ear back placement portion <NUM> includes the dense distribution area R2, the upper transition portion <NUM> includes upper sparse distribution area R1A, and the lower transition portion <NUM> includes the lower sparse distribution area R1B, so that the pitch of the coupling portion in the left-and-right direction D2 in the ear back placement portion <NUM> may be smaller than the pitch of the coupling portion in the left-and-right direction D2 in the upper transition portion <NUM> and smaller than the pitch of the coupling portion in the left-and-right direction D2 in the lower transition portion <NUM>.

If the pitch of the coupling portions in the left-and-right direction D2 is small, the intervals at which the first surface sheet material <NUM>, the stretchable portion member <NUM>, and the second surface sheet material <NUM> are fixed is small in the left-and-right direction D2. Since the ear hook portions 20a, 20a (the ear hook portion sheet <NUM>) are stretched mainly in the left-and-right direction D2, the ease of stretch of the ear back placement portion <NUM> and the ease of stretch of the upper transition portion <NUM> and the lower transition portion <NUM> can be further changed depending on the difference in the pitch in the left-and-right direction D2, so that the fit can be improved and the effect of facilitating the operation for putting on the mask can be further enhanced.

The pitch px2 of the coupling portions <NUM>, <NUM>,. in the left-right direction D2 in the dense distribution area R2 may also be smaller than the pitch px1 of the coupling portions <NUM>, <NUM>,. in the left-right direction D2 in the sparse distribution area R1. The pitch of the coupling portion in the left-and-right direction D2 in the ear back placement portion <NUM> may be smaller than the pitch of the coupling portion in the left-and-right direction D2 in the upper transition portion <NUM>, and may be smaller than the pitch of the coupling portion in the left-and-right direction D2 in the lower transition portion <NUM>.

The pitch px2 of the coupling portion <NUM> in the left-and-right direction D2 in the dense distribution area R2 is preferably <NUM> to <NUM>, more preferably <NUM> to <NUM>. The pitch px1 of the coupling portion <NUM> in the left-and-right direction in the sparse distribution area R1 is preferably <NUM> to <NUM>, more preferably <NUM> to <NUM>. Furthermore, the ratio (px2/px1) of the pitch px2 of the coupling portion <NUM> in the left-and-right direction in the dense distribution area R2 to the pitch px1 of the coupling portion <NUM> in the left-and-right direction in the sparse distribution area R1 is preferably <NUM> to <NUM>, and more preferably <NUM> to <NUM>. Note that the pitch is a pitch measured in the maximum stretch state of the ear hook portion 20a or the ear hook portion sheet <NUM>.

A pitch py2 of the coupling portions <NUM>, <NUM>,. in the height direction D1 in the dense distribution area R2 may be either smaller or larger than or about the same as the pitch py1 of the coupling portions <NUM>, <NUM>,. in the height direction D1 in the sparse distribution area R1. However, the pitch py2 of the coupling portions <NUM>, <NUM>,. in the height direction D1 in the dense distribution area R2 is preferably smaller than the pitch py1 of the coupling portions <NUM>, <NUM>,. in the height direction D1 in the sparse distribution area R1, because the coupling portions <NUM>, <NUM>,. in the dense distribution area R2 can be formed more densely.

As illustrated in <FIG>, the coupling portions <NUM>, <NUM>,. in the plan view are preferably arranged in a zigzag pattern, but may be arranged in a lattice pattern. Alternatively, the arrangement may be neither zigzag nor lattice. For example, as illustrated in <FIG>, a row of coupling portions arranged along the left-and-right direction D2 may be arranged side by side in the height direction D1, and adjacent rows may be slightly shifted in the left-and-right direction D2 by a distance smaller than <NUM>/<NUM> of the pitch px2 in the left-and-right direction D2.

Furthermore, the shape of the coupling portion <NUM> may be circular (<FIG>), elliptical (<FIG>), or other shapes, for example, a polygonal shape, regardless of whether it is in the sparse distribution area R1 or the dense distribution area R2. As illustrated in <FIG>, the shape of the coupling portion <NUM> in the sparse distribution area R1 (R1A, R1B) may be different from the shape of the coupling portion <NUM> in the dense distribution area R2. If the shape of the coupling portion <NUM> in the dense distribution area R2 is an elliptical shape having a long diameter in the height direction D1, the length of the coupling portion <NUM> in the left-and-right direction D2 can be shortened, so that the interval of the wrinkles formed in the material can be reduced and the height of the wrinkles can be made smaller, and accordingly, the appearance can be improved.

The sum of the areas of the multiple coupling portions <NUM>, <NUM>,. may be <NUM> to <NUM>% of the areas of the ear hook portions 20a, 20a (the ear hook portion sheet <NUM>). The ratio of the area of the multiple coupling portions <NUM>, <NUM>,. is a value measured in the maximum stretch state of the ear hook portion 20a or the ear hook portion sheet <NUM>.

<FIG> is a schematic view of a manufacturing apparatus <NUM> of masks according to an embodiment of the invention. The manufacturing apparatus <NUM> of the masks is provided with a manufacturing apparatus <NUM> of ear hook portions on the upstream thereof. Subsequently, a mask member combining apparatus <NUM> for combining the manufactured ear hook portion for the mask with other members of the mask is provided.

The manufacturing apparatus <NUM> of the ear hook portions is provided with a stretchable film band supply means <NUM> for supplying a stretchable film band (stretchable member band) 5A for forming a stretchable film <NUM>, a first surface sheet material band supply means <NUM> for supplying a first surface sheet material band 2A for forming a first surface sheet material <NUM>, and a second surface sheet material band supply means <NUM> for supplying a second surface sheet material band 3A for forming a second surface sheet material <NUM>. A long material, i.e., a stretchable film band 5A, a first surface sheet material band 2A, and a second surface sheet material band 3A are supplied from each supply means, and then the first surface sheet material band 2A and the second surface sheet material band 3A are placed on one surface (first surface) and the other surface (second surface) of the stretchable film band 5A, respectively, to form a multilayer structure 6A. The multilayer structure 6A is conveyed in a conveying direction Dt.

In this case, the stretchable film band 5A is conveyed in a state of being stretched in the conveying direction Dt, i.e., in a state of applying a tensile force (tension) in the conveying direction Dt. The degree of stretching of the stretchable film band 5A is controlled by the feeding speed of the stretchable film band supply means <NUM> and conveying means (not illustrated). The stretchable film band 5A is preferably stretched, for example, about <NUM> to <NUM> times, preferably about <NUM> to <NUM> times, of the natural length. In contrast, the first surface sheet material band 2A and the second surface sheet material band 3A are conveyed in a state having a natural length (a state in which they are not pulled). Therefore, the surfaces of the first surface sheet material band 2A and the second surface sheet material band 3A laid on the respective surfaces of the stretchable film band 5A have a state without wrinkles.

Subsequently, the multilayer structure 6A is fed to the coupling means <NUM>, so that discontinuous coupling portions, i.e., welded portions, are formed over the entire multilayer structure 6A between the stretchable film band 5A and the first surface sheet material band 2A and between the stretchable film band 5A and the second surface sheet material band 3A. The coupling means <NUM> is preferably ultrasonic sheet means, but other means such as welding may be used. The stacked body 8A can be obtained by coupling the layers of the multilayer structure 6A at the multiple discontinuous coupling portions with the coupling means <NUM>.

<FIG> also illustrates an enlarged cross-sectional view of portion III. Multiple coupling portions <NUM>, <NUM>,. are intermittently formed between the stretchable film band 5A and the first surface sheet material band 2A and between the stretchable film band 5A and the second surface sheet material band 3A. In this case, as described with reference to <FIG> and <FIG>, in the coupling portions <NUM>, <NUM>,. , areas having different densities of the coupling portions <NUM>, <NUM>,. are formed in the obtained ear hook portions 20a, 20a (the ear hook portion sheet <NUM>) (described later with reference to <FIG>).

Furthermore, the stacked body 8A is fed to relaxing means <NUM>. In the relaxing means <NUM>, the tension applied to the stretchable film band 5A in the conveying direction Dt is loosened. Although the degree to which the tension is loosened by the relaxing means <NUM> is not limited, it is preferable that the tension is loosened until the stretchable film band 5A returns to its natural length. The stretchable film band 5A is contracted by relaxing the stretchable film band 5A. In this case, the first surface sheet material band 2A, the stretchable film band 5A, and the second surface sheet material band 3A are coupled by the coupling portions <NUM>, <NUM>,. , and are fixed at these positions. Therefore, when the stretchable film band 5A is contracted and the length is shortened, the portions of the first surface sheet material <NUM> and the second surface sheet material <NUM> which are not coupled by the coupling portions <NUM>, <NUM>,. loosen without following the stretchable film band 5A, and rise from the surface (see also <FIG>). Therefore, the first surface sheet material band 2A and the second surface sheet material band 3A are formed with a large number of small pleats extending along a direction orthogonal to the conveying direction Dt. In the first surface sheet material band 2A and the second surface sheet material band 3A, no force occurs or substantially no force occurs to return to the original length when the pleats are formed.

<FIG> also illustrates an enlarged cross-sectional view of the portion IV. As illustrated in the drawing, in the ear hook portion sheet band 20A, the stretchable film band 5A is flat, but the first surface sheet material band 2A and the second surface sheet material band 3A are shrunk to form wrinkles. In the ear hook portion sheet band 20A, continuous irregularities are formed along the conveying direction Dt as seen in a cross section obtained by cutting the first surface sheet material band 2A and the second surface sheet material band 3A along the conveying direction Dt.

Subsequently, the ear hook portion sheet band 20A is fed to punching means <NUM>. In the punching means <NUM>, the ear hook portion sheet band 20A is punched by a punching die so as to obtain the shape of each ear hook portion sheet <NUM>. In any case, multiple ear hook portion sheets <NUM>, <NUM>,. can be obtained by the punching means <NUM>.

In this manner, a method for manufacturing the ear hook portion sheet <NUM> includes: while the stretchable film band 5A including a first surface and a second surface on a side opposite to the first surface is stretched in the predetermined direction (the conveying direction Dt), placing the first surface sheet material band 2A and the second surface sheet material band 3A on the respective surfaces of the stretchable film band 5A; coupling the stretchable film band 5A with the first surface sheet material band 2A and the second surface sheet material band 3A to obtain the stacked body 8A in which the first surface sheet material band 2A, the stretchable film band 5A, and the second surface sheet material band 3A are coupled at multiple coupling portions; causing the stacked body 8A to contract in the predetermined direction (the conveying direction Dt); and cutting the stacked body 8A to form multiple ear hook portion sheets <NUM> constituting a pair of ear hook portions separably coupled to each other.

The ear hook portion sheets <NUM>, <NUM>,. are fed to the mask member combining apparatus <NUM>. In the mask member combining apparatus <NUM>, an auxiliary material band 30A is provided on one surface of the ear hook portion sheet <NUM>. The mask member combining apparatus <NUM> includes a mask body band supply means <NUM> for supplying a mask body band 10A for forming a mask body. The mask body band supply means <NUM> supplies the mask body band 10A to a surface of the ear hook portion sheet <NUM> that is opposite to the surface where the auxiliary material band 30A is provided. In the embodiment of <FIG>, the auxiliary material band 30A is disposed on the outermost side, but may be disposed between the ear hook portion sheet <NUM> and the mask body band 10A.

After the ear hook portion sheet <NUM>, the auxiliary material band 30A, and the mask body band 10A are combined, the first side coupling portion <NUM> and the second side coupling portion <NUM> (<FIG> and <FIG> and the like) described above are formed, and are coupled at predetermined positions by heat sealing or the like by a coupling and cutting unit <NUM>. Subsequently to the coupling or at the same time as the coupling, cutting is performed. Thus, each of the masks <NUM> can be obtained.

<FIG> schematically illustrates, in a plan view, processes of the mask ear hook portion manufacturing apparatus <NUM> and the mask member combining apparatus <NUM> according to an embodiment of the invention. As illustrated in <FIG>, in the ear hook portion sheet band 20A obtained through the coupling means <NUM> and the relaxing means <NUM>, areas in which the degrees of densities of the coupling portions <NUM>, <NUM>,. are different, i.e., the sparse distribution area R1A, R1B, and the dense distribution area R2, are formed along the conveying direction Dt. The sparse distribution area R1A, R1B, and the dense distribution area R2 are formed in a belt-like shape adjacent to a direction orthogonal to the conveying direction Dt (the width direction of the ear hook portion sheet band 20A). The ear hook portion sheet band 20A having the sparse distribution area R1A, R1B and the dense distribution area R2 is punched by punching means <NUM> to obtain the ear hook portion sheet <NUM>. Thus, the sparse distribution area R1A, R1B and the dense distribution area R2, which are continuous along the conveying direction Dt, are formed adjacent to each other in the direction orthogonal to the conveying direction Dt in the ear hook portion sheet band 20A, so that the degree of density of the coupling portion <NUM> can be changed by the ear back placement portion <NUM> of the ear hook portion 20a to be obtained, the upper transition portion <NUM>, and the lower transition portion <NUM> without greatly changing the setting of the coupling means <NUM>.

Claim 1:
An ear hook portion (20a) for mask (<NUM>), the ear hook portion (20a) being made of a material including: a stretchable portion material; and a first surface sheet material (<NUM>) and a second surface sheet material (<NUM>) coupled, via a plurality of coupling portions (<NUM>, <NUM>, <NUM>), to both surfaces of the stretchable portion material in such a state that the stretchable portion material is stretched,
the ear hook portion (20a) comprising:
a proximal portion (<NUM>) fixed to a mask body (<NUM>);
an ear back placement portion (<NUM>) to be situated at a back of an ear of a wearer;
an upper transition portion (<NUM>) extending, on an upper side, from the proximal portion (<NUM>) to the ear back placement portion (<NUM>); and
a lower transition portion (<NUM>) transitioning, on a lower side, from the proximal portion (<NUM>) to the ear back placement portion (<NUM>),
characterized in that a number of the plurality of coupling portions (<NUM>, <NUM>, <NUM>) per unit area in the ear back placement portion (<NUM>) is greater than a number of the plurality of coupling portions (<NUM>, <NUM>, <NUM>) per unit area in each of the upper transition portion (<NUM>) and the lower transition portion (<NUM>).