Patent Publication Number: US-11649540-B2

Title: Deposition mask and method of manufacturing deposition mask

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a division of U.S. application Ser. No. 16/512,697, filed Jul. 16, 2019, which is a continuation of International Application No. PCT/JP2017/046689, filed Dec. 26, 2017, which claims the benefit of priority from Japanese Patent Application No. 2017-005999, filed Jan. 17, 2017, and Japanese Patent Application No. 2017-238989, filed Dec. 13, 2017. The entire contents of these applications are incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The embodiments of the disclosure relate to a deposition mask and a manufacturing method of a deposition mask. 
     BACKGROUND OF THE INVENTION 
     A display device used in a portable device such as a smart phone and a tablet PC has been recently required to have high fineness, e.g., a pixel density of equal to or more than 400 ppi. In addition, there is increasing demand that the portable device is applicable in the full high-definitions reference. In this case, the pixel density of the display device needs to be equal to or more than 800 ppi, for example. 
     An organic EL display device draws attention because of its excellent responsibility and low power consumption. A known method for forming pixels of an organic EL display device is a method which uses a deposition mask including through-holes that are arranged in a desired pattern, and forms pixels in the desired pattern. To be specific, a deposition mask is firstly brought into tight contact with a substrate for organic EL display device, and then the substrate and the deposition mask in tight contact therewith are put into a deposition apparatus so as to perform a deposition step in which an organic material is deposited on the substrate. Thus, pixels containing an organic material can be formed on the substrate in a pattern corresponding to the pattern of the through-holes of the  + deposition mask. 
     As described in JP5382259B, for example, in the deposition step, the deposition mask is fixed on a frame having a predetermined rigidity. For example, when the deposition mask includes a pair of long side surfaces and a pair of short side surfaces, the deposition mask is fixed on the frame, such that the deposition mask is pulled in the long side direction. Thus, warp of the deposition mask is prevented, while a dimensional precision and a positional precision of pixels can be increased. 
     SUMMARY OF THE INVENTION 
     One of the factors deciding a positional precision of pixels to be formed on a substrate may be a positional precision of a deposition mask with respect to a substrate or a frame. As a reference position of a deposition mask upon positioning, an outer profile of the deposition mask can be used, for example. A position of the profile of the deposition mask can be detected by photographing the deposition mask with the use of a camera, for example. 
     In a step of detecting the position of the profile of the deposition mask based on an image photographed by using a camera or the like, it is preferable that a boundary between a deposition mask area and another area is clearly displayed on the image. However, when scattering of light occurs in a portion defining the profile of the deposition mask, the boundary between the deposition mask area and another area gets blurred in the image. 
     The object of the embodiments of the disclosure is to provide a deposition mask and a method of manufacturing a deposition mask, which are capable of effectively solving such a problem. 
     A first embodiment of the disclosure is a deposition mask in which a plurality of through-holes are formed, comprising: a first surface and a second surface, in which the plurality of through-holes are formed; a pair of long side surfaces connected to the first surface and the second surface, and defining a profile of the deposition mask in a longitudinal direction of the deposition mask; and a pair of short side surfaces connected to the first surface and the second surface, and defining a profile of the deposition mask in a width direction of the deposition mask, wherein: the long side surface includes a first portion that is recessed inside, the first portion including a first end portion positioned along the first surface, and a second end portion positioned along the second surface and positioned inside the first end portion; the through-hole includes a first recess formed on the first surface, and a second recess formed on the second surface and connected to the first recess through a hole connection portion; and the first end portion of the first portion of the long side surface is positioned closer to the first surface than the hole connection portion. The first end portion may correspond to a first connection portion to which the first surface and the long side surface are connected, the first connection portion being positioned at a same plane with the first surface. Alternatively, the first end portion may be positioned outside a first connection portion to which the first surface and the long side surface are connected, the first connection portion being positioned at a same plane with the first surface. 
     A second embodiment of the disclosure is a deposition mask in which a plurality of through-holes are formed, comprising: a first surface and a second surface, in which the plurality of through-holes are formed; a pair of long side surfaces connected to the first surface and the second surface, and defining a profile of the deposition mask in a longitudinal direction of the deposition mask; and a pair of short side surfaces connected to the first surface and the second surface, and defining a profile of the deposition mask in a width direction of the deposition mask; wherein: the long side includes a first portion that is recessed inside, the first position including a first end portion positioned along the first surface, and a second end portion positioned along the second surface and positioned inside the first end portion; and the first end portion corresponds to a first connection portion to which the first surface and the long side surface are connected, the first connection portion being positioned at a same plane with the first surface. 
     In the deposition mask according to the first embodiment or the second embodiment of the disclosure, a distance between a first connection portion and the first end portion of the first portion of the long side surface in a plane direction of the first surface may be equal to or less than 3.5 μm, the first connection portion being positioned at a same plane with the first surface and connecting the first surface and the long side surface. 
     In the deposition mask according to the first embodiment or the second embodiment of the disclosure, the first portion may be positioned inside a virtual plane or line, the virtual plane or line passing the first end portion and the second end portion. 
     In the deposition mask according to the first embodiment or the second embodiment of the disclosure, a thickness of the deposition mask may be equal to or less than 50 μM. 
     In the deposition mask according to the first embodiment or the second embodiment of the disclosure, the second end portion may correspond to a second connection portion to which the second surface and the long side surface are connected, the second connection portion being positioned at a same plane with the second surface. 
     A third embodiment of the disclosure is a manufacturing method of a deposition mask in which a plurality of through-holes are formed, comprising: a step of preparing a metal plate including a first surface and a second surface opposite to the first surface; and a processing step of processing the metal plate to obtain the deposition mask which includes a first surface and a second surface in which the plurality of through-holes are formed, a pair of long side surfaces connected to the first surface and the second surface, and defining a profile of the deposition mask in a longitudinal direction of the deposition mask, and a pair of short side surfaces connected to the first surface and the second surface, and defining a profile of the deposition mask in a width direction of the deposition mask; wherein: the long side surface includes a first portion that is recessed inside, the first portion including a first end portion positioned along the first surface, and a second end portion positioned along the second surface and positioned inside the first end portion; the through-hole includes a first recess formed on the first surface, and a second recess formed on the second surface and connected to the first recess through a hole connection portion; and the first end portion of the first portion of the long side surface is positioned closer to the first surface than the hole connection portion. The processing step may include a second-surface etching step of etching the metal plate along the second surface so as to form the first portion of the long side surface, and the second-surface etching step may be performed such that the first end portion of the first portion corresponds to a first connection portion to which the first surface and the long side surface are connected, the first connection portion being positioned at a same plane with the first surface. Alternatively, the processing step may include a first-surface etching step of etching the metal plate along the first surface so as to form a second portion of the long side surface; and a second-surface etching step of etching the metal plate along the second surface so as to form the first portion of the long side surface, the second portion being positioned between the first end portion of the first portion of the long side surface and the first surface of the metal plate. 
     A fourth embodiment of the disclosure is a manufacturing method of a deposition mask in which a plurality of through-holes are formed, comprising: a step of preparing a metal plate including a first surface and a second surface opposite to the first surface; and a processing step of processing the metal plate to obtain the deposition mask which includes a first surface and a second surface in which the plurality of through-holes are formed, a pair of long side surfaces connected to the first surface and the second surface, and defining a profile of the deposition mask in a longitudinal direction of the deposition mask, and a pair of short side surfaces connected to the first surface and the second surface, and defining a profile of the deposition mask in a width direction of the deposition mask; wherein: the long side surface includes a first portion that is recessed inside, the first portion including a first end portion positioned along the first surface, and a second end portion positioned along the second surface and positioned inside the first end portion; the processing step includes a second-surface etching step of etching the metal plate along the second surface so as to form the first portion of the long side surface; and the second-surface etching step is performed such that the first end portion of the first portion corresponds to a first connection portion to which the first surface and the long side surface are connected, the first connection portion being positioned at a same plane with the first surface. 
     In the manufacturing method of the deposition mask according to the third embodiment or the fourth embodiment of the disclosure, a distance between a first connection portion and the first end portion of the first portion of the long side surface in a plane direction of the first surface may be equal to or less than  3 . 5  the first connection portion being positioned at a same plane with the first surface and connecting the first surface and the long side surface. 
     According to the embodiments of the disclosure, the profile of the deposition mask can be precisely detected. 
    
    
     
       BRIEF DESCRIPTION OF THE DRA. INGS 
         FIG.  1    is a view showing a deposition apparatus comprising a deposition mask apparatus according to an embodiment of the disclosure. 
         FIG.  2    is a sectional view showing an organic EL display device manufactured by using the deposition mask apparatus shown in  FIG.  1   . 
         FIG.  3    is a plan view showing the deposition mask apparatus according to the embodiment of the disclosure. 
         FIG.  4    is a perspective view showing a deposition mask. 
         FIG.  5    is a partial plan view showing effective areas of the deposition mask shown in  FIG.  3   . 
         FIG.  6    is a sectional view along the VI-VI line in  FIG.  5   . 
         FIG.  7    is a sectional view along the VII-VII line in  FIG.  5   . 
         FIG.  8    is a sectional view along the VIII-VIII line in  FIG.  5   . 
         FIG.  9    is an enlarged sectional view showing a through-hole shown in  FIG.  5    and an area near thereto. 
         FIG.  10    is a sectional view along the X-X line in  FIG.  4   . 
         FIG.  11    is a plan view showing the deposition mask seen from the side of a first surface. 
         FIG.  12    is a plan view showing the deposition mask seen from the side of a second surface. 
         FIG.  13    is a schematic view for generally describing an example of a manufacturing method of a deposition mask. 
         FIG.  14    is a view showing a step of forming a resist film on a metal plate. 
         FIG.  15    is a view showing a step of bringing an exposure mask into tight contact with the resist film. 
         FIG.  16    is a view showing a step of developing the resist film. 
         FIG.  17    is a view showing a first-surface etching step. 
         FIG.  18    is a view showing a step of coating a first recess with a resin. 
         FIG.  19    is a view showing a second-surface etching step. 
         FIG.  20    is a view showing the second-surface etching step succeeding to  FIG.  19   . 
         FIG.  21    is a view showing a step of removing the resin and a resist pattern from the metal plate. 
         FIG.  22 A  is a plan view showing an intermediate product obtained by processing the metal plate. 
         FIG.  22 B  is an enlarged view showing an area of the intermediate product of  FIG.  22 A , which is surrounded by dotted lines indicated by the symbol XXIIB. 
         FIG.  23    is a view showing a step of separating a deposition mask portion from a support portion. 
         FIG.  24    is an enlarged plan view showing a deposition mask obtained from the intermediate product. 
         FIG.  25    is a view showing a step of manufacturing a deposition mask apparatus. 
         FIG.  26    is a sectional view showing a modification example of a long side surface of the deposition mask. 
         FIG.  27    is a view showing an observation result of a section of a long side surface of a deposition mask according to Example 1. 
         FIG.  28 A  is a view showing a result of the deposition mask shown in  FIG.  27   , when observed from the side of the first surface. 
         FIG.  28 B  is a view showing a result of the deposition mask shown in  FIG.  27   , when observed from the side of the second surface. 
         FIG.  29 A  is a view showing an observation result of a section of a long side surface of a deposition mask according to Example 2. 
         FIG.  29 B  is an enlarged sectional view showing a second portion of the long side surface shown in  FIG.  29 A . 
         FIG.  30    is a view showing an observation result of a section of a long side surface of a deposition mask according to Example 3. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     An embodiment of the disclosure will be described herebelow with reference to the drawings. In the drawings attached to the specification, a scale dimension, an aspect ratio and so on are changed and exaggerated from the actual ones, for the convenience of easiness in illustration and understanding. 
       FIGS.  1  to  25    are views for describing an embodiment of the disclosure. In the below embodiment and the modification example, a manufacturing method of a deposition mask, which is used for patterning an organic material on a substrate in a desired pattern when an organic EL display device is manufactured, is described by way of example. However, not limited thereto, the disclosure can be applied to a manufacturing method for a deposition mask for various uses. 
     In this specification, terms “plate”, “sheet” and “film” are not differentiated from one another based only on the difference of terms. For example, the “plate” is a concept including a member that can be referred to as sheet or film. 
     In addition, the term “plate plane (sheet plane, film plane)” means a plane corresponding to a plane direction of a plate-like (sheet-like, film-like) member as a target, when the plate-like (sheet-like, film-like) member as a target is seen as a whole in general. A normal direction used to the plate-like (sheet-like, film-like) member means a normal direction with respect to a plate plane (sheet surface, film surface) of the member. 
     Further, in this specification, terms specifying shapes, geometric conditions and their degrees, e.g., “parallel”, “orthogonal”, “same”, “similar” etc., and values of a length, an angle and a physical property are not limited to their strict definitions, but construed to include a range capable of exerting a similar function. 
     Firstly, a deposition apparatus  90  that performs a deposition process in which a deposition material is deposited on an object is described with reference to  FIG.  1   . As shown in  FIG.  1   , the deposition apparatus  90  includes therein a deposition source (e.g., crucible  94 ), a heater  96 , and a deposition mask apparatus  10 . The deposition apparatus  90  further includes exhaust means for exhausting an inside of the deposition apparatus  90  into a vacuum atmosphere. The crucible  94  accommodates a deposition material  98  such as an organic luminescence material. The heater  96  heats the crucible  94  to evaporate the deposition material  98  under vacuum atmosphere. The deposition mask apparatus  10  is disposed oppositely to the crucible  94 . 
     Herebelow, the deposition mask apparatus  10  is described. As shown in  FIG.  1   , the deposition mask apparatus  10  includes a deposition mask  20 , and a frame  15  supporting the deposition mask  20 . The frame  15  supports the deposition mask  20  in such a manner that the deposition mask  20  is tensed in its plane direction, in order that the deposition mask  20  is not warped. As shown in  FIG.  1   , the deposition mask apparatus  10  is disposed in the deposition apparatus  90  such that the deposition mask  20  faces a substrate to which the deposition material  98  is to be deposited, such as an organic EL substrate  92 . In the description below, a surface of the deposition mask  20 , which is on the side of the organic EL substrate  92 , is referred to as a first surface  20   a,  and a surface positioned oppositely to the first surface  20   a  is referred to as a second surface  20   b,  but the present invention is not limited thereto. 
     As shown in  FIG.  1   , the deposition mask apparatus  10  may include a magnet  93  located on a surface of the organic EL substrate  93 , which surface is opposed to the deposition mask  20 . Due to the provision of the magnet  93 , the deposition mask  20  can be drawn toward the magnet  93  by a magnetic force, so that the deposition mask  20  can be brought into tight contact with the organic EL substrate  92 . Thus, generation of shadow in a deposition step can be prevented, whereby a dimensional precision and a positional precision of the deposition material  98  with respect to the EL substrate  92  can be improved. 
       FIG.  3    is a plan view of the deposition mask apparatus  10 , when seen from the side of the first surface  20   a  of the deposition mask  20 . As shown in  FIG.  3   , the deposition mask apparatus  10  includes a plurality of deposition masks  20 . In this embodiment, each deposition mask  20  includes a rectangular shape extending in a longitudinal direction D 1 . In the deposition mask apparatus  10 , the deposition masks  20  are arranged side by side in a width direction D 2  intersecting the longitudinal direction D 1  of the deposition masks  20 . Each deposition mask  20  is fixed on the frame  15  by welding, for example, at both ends of the deposition mask  20  in the longitudinal direction D 1 . 
       FIG.  4    is perspective view showing the deposition mask  20 . The deposition mask  20  comprises metal plate-like base member  21 , and a plurality of through-holes  25  passing through the base member  21 . The deposition material  98 , which includes evaporated from the crucible  94  to reach the deposition mask apparatus  10 , passes through the through-holes  25  of the deposition mask  20  to adhere to the organic EL substrate  92 . Thus, the organic material  98  can be deposited on the surface of the organic EL substrate  92  in a desired pattern corresponding to the positions of the through-holes  25  of the deposition mask. 
       FIG.  2    is a sectional view showing an organic EL display device  100  manufactured by using the deposition apparatus of  FIG.  1   . The organic EL display device  100  includes the organic EL substrate  92 , and pixels containing the patterned deposition material  98 . 
     When colored display by a plurality of colors is desired, the deposition apparatuses  90  provided with deposition masks corresponding to respective colors are respectively prepared, and the organic EL substrate  92  is put into the respective deposition apparatuses  90  in sequence. Thus, for example an organic luminescence material for red color, an organic luminescence material for green color, and an organic luminescence material for blue color can be deposited onto the organic EL substrate  92  in sequence. 
     The deposition process is sometimes performed inside the deposition apparatus  90  in a high-temperature atmosphere. In this case, during the deposition process, the deposition masks  20 , the frame  15  and the organic EL substrate  92 , which are held inside the deposition apparatus  90 , are also heated. At this time, each of deposition mask  20 , the frame  15  and the organic EL substrate  92  develop dimensional change behaviors based on their respective thermal expansion coefficients. In this case, when the thermal expansion coefficients of the deposition mask  20 , the frame  15  and the organic EL substrate  92  largely differ from one another, positioning displacement occurs because of the difference in dimensional change. As a result, the dimensional precision and the positional precision of the deposition material to be adhered to the organic EL substrate  92  lower. 
     In order to avoid this problem, the thermal expansion coefficients of the deposition mask  20  and the frame  15  are preferably equivalent to the thermal expansion coefficient of the organic EL substrate  92 . For example, when a glass substrate is used as the organic EL substrate  92 , an iron alloy containing nickel can be used as a main material of the deposition mask  20  and the frame  15 . For example, an iron alloy containing equal to or more than 30% by mass and equal to or less than 54% by mass of nickel can be used as a material of the substrate constituting the deposition masks  20 . Concrete examples of an iron alloy containing nickel may be an invar material containing equal to or more than 34% by mass and equal to or less than 38% by mass of nickel, a super invar material containing cobalt in addition to equal to or more than 30% by mass and equal to or less than 34% by mass of nickel, or a low thermal expansion Fe—Ni based plated alloy containing equal to or more than 38% by mass and equal to or less than 54% by mass of nickel. 
     During the deposition step, if the deposition mask  20 , the frame  15  and the organic EL substrate  92  do not reach high temperatures, it is not particularly necessary that the thermal expansion coefficients of the deposition mask  20  and the frame  15  are equivalent to the thermal expansion coefficient of the organic EL substrate  92 . In this case, a material other than the aforementioned iron alloy can be used as a material for forming the deposition mask  20 . For example, it is possible to use an iron alloy other than the iron alloy containing nickel, such as an iron alloy containing chrome. As an iron alloy containing chrome, an iron alloy that is so-called stainless can be used, for example. In addition, it is possible to use alloy other than an iron alloy, such as nickel, or nickel-cobalt alloy. 
     Next, the deposition mask  20  is described in detail. An outer contour of the deposition mask  20  is firstly described. As shown in  FIGS.  3  and  4   , the deposition mask  20  includes the aforementioned first surface  20   a  and the second surface  20   b  in which the through-holes  25  formed therein, and a pair of long side surfaces  26  and a pair of short side surfaces  27  that are connected to the first surface  20   a  and the second surface  20   b.  The pair of long side surfaces  26  extends in the longitudinal direction D 1  of the deposition mask  20 . When the deposition mask  20  is seen along a normal direction of the first surface  20   a,  the pair of long side surfaces  26  defines a profile of the deposition mask  20  in the longitudinal direction D 1 . The pair of short side surfaces  27  extends in the width direction D 2  of the deposition mask  20 . When the deposition mask  20  is seen along the normal direction of the first surface  20   a,  the pair of short side surfaces  27  defines a profile of the deposition mask  20  in the width direction D 2 . In the example shown in  FIGS.  3  and  4   , the width direction D 2  is orthogonal to the longitudinal direction Dl. In the description below, a portion at which the first surface  20   a  and the long side surface  26  are connected is referred to as a first connection portion  20   e,  and a portion at which the second surface  20   b  and the long side surface  26  are connected is referred to as a second connection portion  20   f.  The first connection portion  20   e  is positioned at a same plane with the first surface  20   a.  The second connection portion  20   f  is positioned at a same plane with the second surface  20   b.    
     Next, the structure of the deposition mask  20  related to the through-holes  25  is described. As shown in  FIGS.  3  and  4   , the deposition mask  20  includes at least one effective area  22  in which through-holes  25  extending from the first surface  20   a  to reach the second surface  20   b  are formed, and a surrounding area  23  around the effective area  22 . The effective area  22  is an area of the deposition mask  20 , which faces a display area of the organic EL substrate  92 . 
     In the example shown in  FIGS.  3  and  4   , the deposition mask  20  includes a plurality of the effective areas  22  that are arranged at predetermined intervals along the longitudinal direction D 1  of the deposition mask  20 . One effective area  22  corresponds to a display area of one organic EL display device  100 . Thus, the deposition mask apparatus  10  shown in  FIG.  1    enables a multifaceted deposition of the organic EL display devices  100 . Namely, a pattern of the organic material  98  corresponding to the plurality of organic EL display devices  100  can be formed on one organic substrate  92  with the use of one deposition mask  20 . 
     As shown in  FIGS.  3  and  4   , the effective area  22  has, for example, a profile of a substantially quadrangular shape in plan view, more precisely, a substantially rectangular shape in plan view. Although not shown, each effective area  22  can have profiles of different shapes depending on a shape of the display area of the organic EL substrate  92 . For example, each effective area  22  may have a circular profile. 
     Herebelow, a sectional shape of the effective area  22  is described in detail.  FIG.  5    is an enlarged plan view showing the effective area  22  when seen from the side of the second surface  20   b  of the deposition mask  20 . As shown in  FIG.  5   , in the illustrated example, the plurality of through-holes  25  formed in each effective area  22  are arranged in the effective area  22  at predetermined pitches along two directions orthogonal to each other. An example of the through-hole  25  is described in further detail with reference mainly to  FIGS.  6  to  8   .  FIGS.  6  to  8    are sectional views along the VI-VI direction to VIII-VIII direction of the effective area  22  of  FIG.  5   . 
     As shown in  FIGS.  6  to  8   , the plurality of through-holes  25  pass through the deposition mask  20  from the first surface  20   a,  which is one side along a normal direction N of the deposition mask  20 , to the second surface  20   b,  which is the other side along the normal direction N of the deposition mask  20 . In the illustrated example, as described in detail later, first recesses  30  are formed by etching in the first surface  20   a  of the deposition mask  20 , and second recesses  35  are formed in the second surface  20   b  of the deposition mask  20 . Each of the first recesses  30  is connected to each of the second recesses  35 , so that the second recess  35  and the first recess  30  are formed to communicate with each other. Each through-hole  25  is composed of the second recess  35  and the first recess  30  connected to the second recess  35 . 
     As shown in  FIGS.  6  to  8   , an opening area of each second recess  35 , in a cross-section along a plate plane of the deposition mask  20  at each position along the normal direction N of the deposition mask, gradually decreases from the side of the second surface  20   b  of the deposition mask  20  toward the side of the first surface  20   a  thereof. Similarly, an opening area of each first recess  30 , in a cross-section along the plate plane of the deposition mask  20  at each position along the normal direction N of the deposition mask, gradually decreases from the side of the first surface  20   a  of the deposition mask  20  toward the side of the second surface  20   b  thereof. 
     As shown in  FIGS.  6  to  8   , a wall surface  31  of the first recess  20  and a wall surface  36  of the second recess  35  are connected through a circumferential hole connection portion  41 . The hole connection portion  41  is defined by a ridge line of a bulging part where the wall surface  31  of the first recess  30 , which is inclined with respect to the normal direction N of the deposition mask  20 , and the wall surface  36  of the second recess  35 , which is inclined with respect to the normal direction of the deposition mask  20 , are merged with each other. The hole connection portion  41  defines a through-portion  42  where an area of the through-hole  25  is minimum in plan view of the deposition mask  20 . 
     As shown in  FIGS.  6  to  8   , the adjacent two through-holes  25  in the first surface  20   a  of the deposition mask  20  are spaced apart from each other along the plate plane of the deposition mask  20 . Namely, as in the below-described manufacturing method, when the first recesses  30  are composed of etching the base member  21  along the first surface  20   a  of the deposition mask  20 , the first surface  20   a  remains between the adjacent two first recesses  30 . 
     Similarly, as shown in  FIGS.  6  and  8   , the adjacent two second recesses  35  may be spaced apart from each other along the plate plane of the deposition mask  20 , on the side of the second surface  20   b  of the deposition mask  20 . Namely, the second surface  20   b  of the deposition mask  20  may remain between the adjacent two second recesses  35 . In the below description, this portion of the effective area  22  of the second surface  20   b  of the deposition mask  20 , which is not etched and thus remains, is also referred to as a top portion  43 . By manufacturing the deposition mask  20  such that such a top portion  43  remains, the deposition mask  20  can include a sufficient strength. Thus, it can be prevented that the deposition mask  20  is damaged during conveyance, for example. However, when a width β of the top portion  43  is too large, there is a possibility that shadow occurs in the deposition step, which lowers utilization efficiency of the deposition material  98 . Thus, the deposition mask  20  is preferably manufactured such that the width β of the top portion  43  is excessively large. For example, the width β of the top portion  43  is preferably equal to or less than 2 μm. In general, the width β of the top portion  43  varies depending on a direction along which the deposition mask  20  is severed. For example, the width β of the top portion  43  shown in  FIG.  6    and that of  FIG.  8    may differ from each other. In this case, the deposition mask  30  may be formed such that the width  13  of the top portion  43  is equal to or less than 2 μm, regardless of a direction along which the deposition mask  20  is severed. The shadow means a phenomenon in which a surface area and/or a thickness of a layer of the deposition material  98  on the substrate lack, because a part of the deposition material  98 , which came from the deposition source to reach the deposition mask  20 , hits the wall surface  31  of the first recess  30  of the deposition mask  20  and/or the wall surface  36  of the second recess  35  thereof so as not to reach the substrate such as the organic EL substrate  92 . 
     As shown in  FIG.  7   , the etching process may be performed such that adjacent two second recesses  35  are connected to each other, depending on their positions. Namely, there may be a part where no second surface  20   b  remains between the adjacent two second recesses  35 . In addition, although not shown, the etching process may be performed such that adjacent two second recesses  35  are connected over the whole area of the second surface  20   b.    
     When the deposition mask apparatus  10  is received in the deposition apparatus  90  as shown in  FIG.  1   , the first surface  20   a  of the deposition mask  20  faces the organic EL substrate  92 , and the second surface  20   b  of the deposition mask  20  is located along the crucible  94  holding the deposition material  98 . Thus, the deposition material  98  adheres to the organic EL substrate  92  through the second recess  35  whose opening area gradually decreases. As indicated by the arrow in  FIG.  6    extending from the second surface  20   b  toward the first surface  20   a,  the deposition material  98  not only moves from the crucible  94  toward the organic EL substrate  92  along the normal direction N of the organic EL substrate  92 , but also sometimes moves along a direction largely inclined with respect to the normal direction N of the organic EL substrate  92 . At this time, when the thickness of the deposition mask  20  is large, most of the diagonally moving deposition material  98  reaches the wall surface  36  of the second recess  35  to adhere thereto, before the deposition material  98  passes through the through-holes  25  to reach the organic EL substrate  92 . Thus, in order to improve utilization efficiency of the deposition material  98 , it is preferable that the thickness t of the deposition mask  20  is reduced so that heights of the wall surface  36  of the second recess  35  and the wall surface  31  of the first recess  30  are reduced. Namely, it can be said that it is preferable that a base member  21 , which has the thickness t as small as possible, as long as the strength of the deposition mask  20  is ensured, is used as the base member  21  for constituting the deposition mask  20 . In consideration of this point, the thickness t of the deposition mask  20  in this embodiment is preferably set to be equal to or less than 50 μm, e.g., equal to or more than 5 μm and equal to or less than 50 μm. The thickness t of the deposition mask  20  may be equal to or less than 30 μm, may be equal to or less than 25 μm, may be equal to or less than 20 μm, may be equal to or less than 18 μm, may be equal to or less than 15 μm, or may be equal to or less than 13 μm. By reducing the thickness t of the deposition mask  20 , it can be prevented that the deposition material  98  hits the wall surface  31  of the first recess  30  and/or the wall surface  36  of the second recess  35  in the deposition step, whereby generation of shadow can be prevented. In addition, the thickness of the metal plate  64  may be equal to or more than 2 μm, may be equal to or more than 5 μm, may be equal to or more than 10 μm, or may be equal to or more than 15 μm. The thickness t is a thickness of the surrounding area  23 , i.e., a thickness of a part of the deposition mask  20  where the first recess  30  and the second recess  35  are not formed. Therefore, the thickness t can be said as a thickness of the base member  21 . In addition, the thickness t can be said as a thickness of the metal plate  64  constituting the base member  21  of the deposition mask  20 . 
     In  FIG.  6   , a minimum angle defined by a line L 1 , which passes the connection portion  31  including the minimum opening area of the through-hole  25  and another given position of the wall surface  36  of the second recess  35 , with respect to the normal direction N of the deposition mask  20  is represented by a symbol θ 1 . In order that the diagonally moving deposition material  98  can be caused to reach the organic EL substrate  92  with being caused to reach the wall surface  36  as much as possible, it is advantageous that the angle θ 1  is increased. In order to increase the angle θ 1 , it is effective to reduce the aforementioned width β of the top portion  43 , as well as to reduce the thickness t of the deposition mask  20 . 
     In  FIG.  8   , the symbol a represents a width of a portion (hereinafter also referred to as “rib portion”) of the effective area  22  of the first surface  20   a  of the deposition mask  20 , which is not etched and thus remains. A width α of the rib portion and a size r 2  of the through-portion  42  are suitably determined depending on a size of an organic EL display device and the number of display pixels. For example, the width a of the rib portion is equal to or more than 5 μm and equal to or less than 40 μm, and the size r 2  of the through-portion  42  is equal to or more than 10 μm and equal to or less than 60 μtm. 
     Although not limited, the deposition mask  20  according to this embodiment is particularly effective when an organic EL display device including a pixel density of equal to or more than  450  ppi is manufactured. Herebelow, a size example of the deposition mask  20  required for manufacturing an organic EL display device having such a high pixel density is described with reference to  FIG.  9   .  FIG.  9    is an enlarged sectional view showing the through-hole  25  of the deposition mask  20  shown in  FIG.  6    and an area near thereto. 
     In  FIG.  9   , as parameters related to the shape of the through-hole  25 , a distance from the first surface  20   a  of the deposition mask  20  up to the hole connection portion  41  thereof along the normal direction N of the deposition mask  20 , i.e., a height of the wall surface  31  of the first recess  30  is represented by a symbol r 1 . Further, a size of the first recess  30  in a part where the first recess  30  is connected to the second recess  35 , i.e., a size of the through-portion  42  is represented by a symbol r 2 . In addition, in  FIG.  9   , an angle that is defined by a line L 2 , which connects the hole connection portion  41  and a distal edge of the first recess  30  in the first surface  21   a  of the base member  21 , with respect to the normal direction N of the base member  21  is represented by a symbol θ 2 . 
     When an organic EL display device having a pixel density of equal to or more than 450 ppi is manufactured, the size r 2  of the through-portion  42  is preferably set to be equal to or more than 10 and equal to or less than 60 μm. Due to this size, it is possible to provide the deposition mask  20  capable of manufacturing an organic EL display device having a high pixel density. Preferably, the height r 1  of the wall surface  31  of the first recess  30  is set to be equal to or less than 6 μm. 
     Next, the aforementioned angle θ 2  shown in  FIG.  9    is described. The angle θ 2  corresponds to a maximum value of an inclined angle of the deposition material  98  that can reach the organic EL substrate  92 , out of the deposition material  98  that comes in an inclined manner with respect to the normal direction N of the base member  21  and passes through the through-portion  42  near the through-connection portion  41 . This is because the deposition material  98  coming at an inclined angle greater than the angle  02  adheres to the wall surface  31  of the first recess  30 , before the deposition material  98  reaches the substrate  92 . Thus, by decreasing the angle θ 2 , it can be prevented that the deposition material  98  coming at a large inclined angle and passing through the through-portion  42  adheres to the substrate  92 . Therefore, it can be prevented that the deposition material  98  adheres to a portion of the organic EL substrate  92 , which is outside a part overlapping with the through-portion  42 . Namely, to decrease the angle θ 2  can prevent variation in surface area and thickness of the deposition material  98  adhering to the organic EL substrate  92 . From this point of view, the through-hole  25  is formed such that the angle θ 2  is equal to or less than 45 degrees, for example.  FIG.  9    shows the example in which the size of the first recess  30  in the first surface  21   a,  i.e., the opening size of the through-hole  25  in the first surface  21   a  is larger than the size r 2  of the first recess  30  in the through-connection portion  41 . Namely, the value of the angle θ 2  is a positive value. However, although not shown, the size r 2  of the first recess  30  in the through-connection portion  41  may be larger than the size of the first recess  30  in the first surface  21   a.  Namely, the value of the angle θ 2  may be a negative value. 
     Next, a sectional shape of the surrounding area  23  is described in detail.  FIG.  10    is a sectional view of the deposition mask  20  when cut along the X-X line in  FIG.  4   . As shown in  FIG.  10   , the long side surface  26  constituting an end portion of the surrounding area  23  includes a first portion  261  which is a surface that is recessed inside. In this embodiment, the first portion  261  is a curved surface that is curved to be recessed inside. When the long side surface  26  is seen from outside along a plane direction of the first surface  20   a,  the first portion  261  includes a first end portion  261   a  that defines a profile of the first portion  261  along the first surface  20   a,  and a second end portion  261   b  that defines a profile of the first portion  261  along the second surface  20   b.  When the term “inside” is used for the long side surface  26 , as indicated by the arrow Al in  FIG.  10    and below-described  FIG.  22 B , the “inside” means a center side in the width direction D 2  of the deposition mask  20 . As shown in  FIGS.  4  and  10   , the “center side” means a side of a centerline C that passes an intermediate point of the deposition mask  20  in the width direction D 2 . In addition, as shown by the arrow A 2  in  FIG.  10    and the below-described  FIG.  22 B , the “outside” means a side away from the centerline C of the deposition mask  20  in the width direction D 2  of the deposition mask  20 . In addition, the term “recessed inside” means that the first portion  261  is positioned inside a virtual line or plane connecting the first end portion  261   a  of the first portion  261  along the first surface  20   a  and the second end portion  261   b  of the first portion  261   a  along the second surface  20   b.  Although not shown, the first portion  261  may include a flat surface. Namely, it is not necessary that the first portion  261  is formed only of a curved surface. In addition, the first portion  261  may locally include an irregular surface having a zigzag shape. 
     As shown in  FIG.  10   , the first end portion  261   a  of the first portion  261  is positioned outside the second end portion  261   b.  As described below, such a first portion  261  is formed by etching a metal plate constituting the base member  21  along the second surface  20   b.  A distance γ between the first end portion  261   a  and the second end portion  261   b  in the width direction D 2  is, for example, equal to or more than 5 μm and equal to or less than 50 μm. 
     In the example shown in  FIG.  10   , the second end portion  261   b  of the first portion  261  corresponds to the second connection portion  20   f  at which the second surface  20   b  and the long side surface  26  are connected. In other words, the first portion  261  spreads up to the second surface  20   b.  In addition, in the example shown in  FIG.  10   , the first end portion  261   a  of the first portion  261  corresponds to the first connection portion  20   e  at which the first surface  20   a  and the long side surface  26  are connected. In other words, the first portion  261  spreads up to the first surface  20   a.    
     Next, a shape of the long side surface  26  in plan view is described.  FIG.  11    is a plan view of the long side surface  26  when seen from the side of the first surface  20   a  along the normal direction of the first surface  20   a.  In addition,  FIG.  12    is a plan view of the long side surface  26  when seen from the side of the second surface  20   b  along the normal direction of the second surface  20   b.    
     As shown in  FIG.  11   , when the long side surface  26  is seen from the side of the first surface  20   a,  the first portion  261  is invisible. In this case, the profile of the deposition mask  20  in the longitudinal direction D 1  is defined by the first connection portion  20   e  at which the first surface  20   a  and the long side surface  26  are connected. In this case, an area near to the first connection portion  20   e  is formed of the flat first surface  20   a.  Thus, the position of the profile of the deposition mask  20  in the longitudinal direction D 1  can be easily detected. 
     On the other hand, as apparent from  FIG.  12   , when the long side surface  26  is seen from the side of the second surface  20   b,  the first portion  261  is visible. In the first portion  261 , light is scattered in various directions. Thus, in the example shown in  FIG.  12   , the first portion  261  is observed as a portion that seems darker than the second surface  20   b,  or is displayed as such a portion in an image. In addition, the first portion  261  has a width corresponding to the distance  y  in  FIG.  10   . Thus, at a position of the profile of the deposition mask  20  when seen from the side of the second surface  20   b,  there is an unclear portion corresponding to the width of the first portion  261 . Thus, as compared with a case in which the first portion  261  is seen from the side of the first surface  20   a,  it is more difficult to detect a position of the profile of the deposition mask  20  in the longitudinal direction D 1 , when seen from the side of the second surface  20   b.  Thus, in a step of positioning the deposition mask  20  with respect to the organic EL substrate  92  or the frame  15 , it is easy to adjust the position of the deposition mask  20  based on a result of an image of the deposition mask  20  photographed from the side of the first surface  20   a,  whereby a positional precision can be improved. 
     Next, a manufacturing method of a deposition mask  20  is described. 
     Firstly, a metal plate  64  for manufacturing a deposition mask is prepared. The metal plate  64  is prepared in the form of a roll obtained by winding an elongated metal plate. As the metal plate  64 , a metal plate made of an iron alloy containing nickel is used, for example. A thickness of the metal plate  64  is equal to or more than 5 μm and equal to or less than  50  A rolling method or a plating deposition method can be employed as a method of manufacturing the metal plate  64  having a desired thickness. 
     Next, a method of manufacturing the deposition mask  20  with the use of the metal plate  64  is described with reference mainly to  FIGS.  13  to  24   . In the below-described manufacturing method of the deposition mask  20 , as shown in  FIG.  13   , the metal plate  64  is processed such that a plurality of deposition mask portions including the through-holes  25  are formed on the metal plate  64  (processing step), and then the deposition mask portions are separated from the metal plate  64  (separation step), so that the sheet-like deposition masks  20  can be obtained. 
     The step of processing the metal plate  64  includes a step of etching the elongated metal plate  64  by using a photolithographic technique to form first recesses  30  along a first surface  64   a  of the metal plate  64 , and a step of etching the metal plate  64  by using a photographic technique to form second recesses  35  along a second surface  64   b  of the metal plate  64 . By communicating the first recesses  30  and the second recesses  35  formed in the metal plate  64  to each other, the through-holes  25  are manufactured in the metal plate  64 . In the below-described example, the step of forming the first recesses  30  is performed before the step of forming the second recesses  35 , and a step of sealing the manufactured first recesses  30  is performed between the step of forming the first recesses  30  and the step of forming the second recesses  35 . Herebelow, the respective steps are described in detail. 
       FIG.  13    shows a manufacturing apparatus  60  for manufacturing the deposition masks  20 . As shown in  FIG.  13   , a roll  62  including a core  61  around which the metal plate  64  is wound is prepared. By rotating the core  61  to reel out the roll  62 , the metal plate  64  extending like a strip is supplied, as shown in  FIG.  13   . 
     The supplied metal plate  64  is conveyed to a processing apparatus (etching means)  70  by a conveyor roller  72 . Respective processes shown in  FIGS.  14  to  21    are performed by the processing apparatus  70 . In this embodiment, the plurality of depositions masks  20  is allocated in a width direction of the metal plate  64 . In other words, the metal plate  64  is processed such that the below-described deposition mask portions, which will be separated from the metal plate  64  to provide the deposition masks  20 , are aligned in the width direction of the metal plate  64 . In this case, preferably, the plurality of deposition masks  20  are allocated to the metal plate  64  such that the direction of a long side surface  26  of the deposition mask portion, i.e., the deposition mask  20  corresponds to the longitudinal direction of the eloigned metal plate  64 . 
     As shown in  FIG.  14   , resist films  65   c,    65   d  each containing a negative-type photosensitive resist material are firstly formed on the first surface  64   a  and the second surface  64   b  of the metal plate  64 . For example, the resist films  65   c,    65   d  are formed by applying a coating liquid containing a negative-type photosensitive resist material onto the first surface  64   a  and the second surface  64   b  of the metal plate  64 , and then by drying the coating liquid. 
     Then, exposure masks  68   a,    68   b,  which do not allow light transmit through areas of the resist films  65   c,    65   d  to be removed therefrom, are prepared. As shown in  FIG.  15   , the exposure masks  68   a,    68   b  are located on the resist films  65   c,    65   d,  respectively. For example, glass dry plates, which do not allow light to transmit through the areas to be removed from the resist films  65   c,    65   d,  are used as the exposure masks  68   a,    68   b.  Thereafter, the exposure masks  68   a,    68   b  are sufficiently brought into tight contact with the resist films  65   c,    65   d  by vacuum bonding. 
     A positive-type photosensitive resist material may be used. In this case, an exposure mask, which allows light to transmit through an area to be removed of the resist film, is used. 
     Thereafter, the resist films  65   c,    65   d  are exposed across the exposure masks  68   a,    68   b  (exposure step). Further, in order to form an image on the exposed resist films  65   c,    65   d,  the resist films  65   c,    65   d  are developed (development step). Thus, as shown in  FIG.  16   , a first resist pattern  65   a  can be formed on the first surface  64   a  of the metal plate  64 , and a second resist pattern  65   b  can be formed on the second surface  64   b  of the metal plate  64 . The development step may include a resist heating step for increasing a hardness of the resist films  65   c,    65   d,  or for more securely adhering the resist films  65   c,    65   d  to the metal plate  64 . The resist heating step can be performed at a temperature equal to or more than a room temperature and equal to or less than 400° C., for example. In  FIG.  16    and the below-described  FIGS.  17  to  21   , a manufacturing step of the effective area  22  is shown on the right side, and a manufacturing step of the surrounding area  23  is shown on the left side. 
     As shown in  FIG.  16   , the first resist pattern  65   a  provided on the effective area  22  has a hole  66   a  located at a position where the first recess  30  is formed in the first surface  64   a  thereafter. On the other hand, the first resist pattern  65   a  provided on the surrounding area  23  covers a portion which becomes the long side surface  26  of the first surface  64   a  thereafter. In addition, the second resist pattern  65   b  includes a hole  66   b  located at a position where the second recess  35  is formed in the second surface  64   b  of the effective area  22  thereafter, and an opening  66   d  located at a portion which becomes the long side surface  26  of the second surface  64   b  of the surrounding area  23  thereafter. A size M 2  of the opening  66   d  is larger than a size M 1  of the hole  66   b.  The size M 2  of the opening  66   d  is equal to or more than 50 μm, for example. 
     Then, as shown in  FIG.  17   , a first-surface etching step is performed, in which areas of the first surface  64   a  of the metal plate  64 , which are not covered with the first resist pattern  65   a,  are etched by using a first etchant. For example, the first etchant is jetted to the first surface  64   a  of the metal plate  64  across the first resist pattern  65   a,  from a nozzle disposed on the side facing the first surface  64   a  of the conveyed metal plate  64 . As a result, as shown in  FIG.  17   , the areas of the metal plate  64 , which correspond to the holes  66   a  in the first surface  64   a  of the metal plate  64 , are eroded by the first etchant. Thus, the plurality of first recesses  30  are formed in the first surface  64   a  of the metal plate  64 . The first etchant to be used is an etchant containing ferric chloride solution and hydrochloric acid, for example. As described above, the first resist pattern  65   a  provided on the surrounding area  23  covers the portion which becomes the long side surface  26  of the first surface  64   a  thereafter. Thus, the first recess  30  is not formed in the portion of the first surface  64   a,  which becomes the long side surface  26  thereafter. 
     Thereafter, as shown in  FIG.  18   , the first recesses  30  are coated with a resin  69  resistant to a second etchant that is used in a succeeding second-surface etching step. Namely, the first recesses  30  are sealed with the resin  69  resistant to the second etchant. In the example shown in  FIG.  18   , a film of the resin  69  is formed to cover not only the formed first recesses  30  but also the first surface  64   a  (first resist pattern  65   a ). 
     Then, as shown in  FIG.  19   , the second-surface etching step is performed, in which areas of the second surface  64   b  of the metal plate  64 , which correspond to the holes  66   b  and the openings  66   d,  are etched so as to form the second recesses  35  in the second surface  64   b.    FIG.  20    is a view showing a state in which the second-surface etching step further proceeds. As shown in  FIG.  20   , in the area of the metal plate  64 , which corresponds to the effective area  22 , the second-surface etching step is performed until the first recess  30  and the second recess  35  communicate with each other so that the through-hole  25  is formed. On the other hand, in the area of the metal plate  64 , which corresponds to the surrounding area  23 , the second-surface etching step is performed until the second recess  35  reaches the first surface  64   a.  As described above, the size M 2  of the opening  66   d  of the second resist pattern  65   b  positioned on the surrounding area  23  is larger than the size M 1  of the hole  66   b  of the second resist pattern  65   b  positioned on the effective area  22 . Thus, as shown in  FIG.  20   , the etching in the thickness direction of the metal plate  64  can be made to progress more quickly in the surrounding area  23  than the effective area  22 . Similarly to the first etchant, the second etchant to be used is an etchant containing ferric chloride solution and hydrochloric acid, for example. 
     The erosion by the second etchant develops in a part where the metal plate  64  is in contact with the second etchant. Thus, the erosion develops not only in the normal direction N (thickness direction) of the metal plate  64  but also in a direction along the plate plane of the metal plate  64 . Preferably, the second-surface etching step is ended before two second recesses  35 , which are respectively formed on positions facing adjacent two holes  66   a  of the second resist pattern  65   b,  merge on the reverse side of the second resist pattern  65   b  positioned between the two holes  66   a.  Thus, as shown in  FIG.  20   , the aforementioned top portion  43  can remain in the second surface  64   b  of the metal plate  64 . 
     Thereafter, as shown in  FIG.  21   , the resin  69  is removed from the metal plate  64 . For example, the resin  69  can be removed by using an alkali-based peeling liquid. When the alkali-based peeling liquid is used, as shown in  FIG.  21   , the resist patterns  65   a,    65   b  are removed simultaneously with the removal of the resin  69 . However, after the removal of the resin  69 , the resist patterns  65   a,    65   b  may be removed separately from the resin  69 . 
     As shown in  FIG.  21   , in the area of the metal plate  64 , which corresponds to the surrounding area  23 , since the second recess  35  reaches the first surface  64   a,  the long side surface  26  separated from another part of the metal plate  64  in the width direction D 2  can be formed. The long side surface  26  includes the first portion  261  based on the second recess  35  which was formed in the second surface  64   b  of the metal plate  64  correspondingly to the opening  66   d of the second resist pattern  65   b.  In this case, the first end portion  261   a  of the first portion  261  corresponds to the first connection portion  20   e  at which the long side surface  26  and the first surface  64   a  (first surface  20   a ) are connected. 
       FIG.  22 A  is a plan view showing an intermediate product  50  obtained by processing the deposition masks  20  to form the through-holes  25 , as described above. The intermediate product  50  includes the plurality of deposition mask portions  51  and a support portion  56 . A conveying direction of the metal plate  64  in the manufacturing step of the deposition masks  20  corresponds to the longitudinal direction D 1 . 
     Each deposition mask portion  51  is a portion of the metal plate  64 , which becomes the deposition mask  20  by separation. As shown in  FIG.  22 A , the deposition mask portions  51  are arranged side by side in the width direction D 2 . 
     The support portion  56  is a portion that surrounds the plurality of deposition mask portions  51  in a plan view, and is partially connected to the deposition mask portions  51 . In the example shown in  FIG.  22 A , the support portion  56  is a portion of the metal plate  64 , which is other than the deposition mask portions  51 . As shown in  FIG.  22 A , the deposition mask portions  51  are connected to the support portion  56  at the short side surfaces  27  through a connection portion  54 . 
       FIG.  22 B  is an enlarged view showing an area of the intermediate product of  FIG.  22 A , which is surrounded by dotted lines indicated by the symbol XXIIB. In the aforementioned connection portion  54 , the short side surface  27  of the deposition mask portion  51  includes a plurality of projections  53   a  protruding toward the support portion  56  so as to be connected to the support portion  56 . For example, between the short side surface  27  of the intermediate product  50  and the support portion  56  thereof, a plurality of second through-portions  55   b  passing through the metal plate  64  are arranged side by side along a direction in which the short side surface  27  extends. A size K of the second through-portion  55   b  in the width direction D 2  is equal to or more than 30 μm, for example, or equal to or less than 100 μm, for example. The projection  53   a  is positioned between two second through-portions  55   b  that are adjacent in the direction in which the short side surface  27  extends. On the other hand, the long side surface  26  of the deposition mask portion  51  is not connected to the support portion  56 . In other words, in the intermediate product  50 , between the long side surface  26  of the deposition mask portion  51  and the support portion  56 , a first through-portion  55   a  passing through the metal plate  64  extends along a direction in which the long side surface  26  extends. A size S of the first through-portion  55   a  in the width direction D 2  is equal to or more than 0.1 mm, for example, or equal to or less than 5 mm, for example. 
     As described above, the first through-portion  55   a  constituting the long side surface  26  is formed by performing the second-surface etching step until the second recess  35  reaches the first surface  64   a.  In this case, the first end portion  261   a  of the aforementioned portion  261  included in the long side surface  26 , which is formed by the second-surface etching step, is positioned on the first surface  64   a  of the metal plate  64 . Namely, the first end portion  261   a  of the first portion  261  corresponds to the first connection portion  20   e  at which the first surface  20   a  of the deposition mask  20  and the long side surface  26  thereof are connected. 
     Similarly to the first through-portion  55   a  constituting the long side surface  26 , the second through-portions  55   b  constituting the short side surface  27  are formed by performing the second-surface etching step until the second recess  35  reaches the first surface  64   a.    
     The fact that the first through-portion  55   a  and the second through-portion  55   b  are formed by performing the second-surface etching step until the second recess  35  reach the first surface  64   a  means that the first through-portion  55   a  and the second through-portion  55   b  do not include the first recess  30  connected to the second recess  35 . An advantage obtained by the fact that the first through-portion  55   a  and the second through-portion  55   b  do not include the first recess  30  is described below. 
     After the first-surface etching step, the metal plate  64  is conveyed to a location where the second-surface etching step is performed. At this time, when the first recess  30  is formed in the first-surface etching step in a portion of the metal plate  64 , at which the long side surface  26  or the short side surface  27  is formed thereafter, the metal plate  64  may crack from the first recess  30  during the conveyance. Since the first recess  30  formed in the portion where the long side surface  26  is formed has a size equivalent to that of the deposition mask  20  in the longitudinal direction D 1 , cracking is particularly likely to generate from this first recess  30 . 
     On the other hand, in this embodiment, the first through-portion  55   a  or the second through-portion  55   b  does not include the first recess  30 . Thus, in the first-surface etching step, no first recess  30  is formed in a portion of the metal plate  64 , at which the long side surface  26  or the second side surface  27  is formed thereafter. Therefore, when the metal plate  64  is conveyed to a location where the second-surface etching step is performed after the first-surface etching step, it can be prevented that the metal plate  64  is defectively conveyed, e.g., the metal plate  64  cracks. 
     In addition, the fact that the first recess  30  is not formed means that a step of coating the first recess  30  with the resin  69  is unnecessary. If the first recess  30  is formed in a portion at which the long side surface  26  is formed, since a size of the portion is larger than the size of the first recess  30  constituting the through-hole  25 , cost and effort required for coating the first recess with the resin  69  are great. On the other hand, according to this embodiment, since the first through-portion  55   a  or the second through-portion  55   b  does not include the first recess  30 , cost and effort required for coating the first recess  30  with the resin  69  can be saved. 
     Following thereto, the separation step is performed, in which the deposition mask portions  51  of the aforementioned intermediate product  50  are separated from the support portion  56  thereof. As shown in  FIG.  13   , the intermediate product  50  obtained by processing the metal plate  64  is firstly conveyed to a separation apparatus  73  for performing the separation step. For example, the intermediate product  50  is conveyed to the separation apparatus  73  by the conveyor rollers  72 ,  72  that are rotated with sandwiching the intermediate product  50  therebetween. In the intermediate product  50 , when the long side surface  26  of the deposition mask portion  51  is not connected to the support portion  56 , the deposition mask portion  51  tends to shake and/or warp during conveyance. In consideration of this point, the intermediate product  50 , the conveyor rollers  72  or a conveyor path may be equipped with means for restraining shaking and/or warping of the deposition mask portion  51 . For example, the restraint means include a pair of films disposed on the first surface side and the second surface side of the intermediate product  50 . Since the intermediate product  50  is conveyed to the separation apparatus  73  with the intermediate product  50  being sandwiched between the pair of films, shaking and/or warping of the deposition mask portion  51  can be prevented. 
       FIG.  23    is a view showing the separation step of separating the deposition mask portion  51  from the support portion  56 . As described above, the long side surface  26  of the deposition mask portion  51  and the support portion  56  are not connected. Thus, by breaking the connection portion  54  between the short side surface  27  of the deposition mask portion  51  and the support portion  56 , the deposition mask portion  51  can be separated from the support portion  56  so as to obtain the deposition mask  20 .  FIG.  24    is an enlarged plan view showing the deposition mask  20  obtained from the intermediate product  50 . 
     The separation step includes, for example, a breaking step in which the connection portion  54  in the short side surface  27  of the deposition mask portion  51 , which is connected to the support portion  56 , is broken. In this case, as shown in  FIG.  24   , a part of the deposition mask  20  at which the connection portion  54  is broken, e.g., distal ends of the projections  27   a  of the short side surface  27  become broken-out surfaces  27   b.  The broke-out surface  27   b  is a surface including a burr caused by a force exerted from the support portion  56  upon breakage. On the other hand, the long side surface  26  has no broken-out surface. 
     In  FIG.  24   , a symbol E represents a minimum distance in the plane direction of the base member  21 , which is from the first connection portion  20   e  at which the long side surface  26  and the first surface  20   a  are connected, up to the through-hole  25 . The distance E is smaller than a minimum distance in the plane direction of the base member  21 , which is from the connection portion at which the short side surface  27  and the first surface  20   a  are connected, up to the through-hole  25 . Thus, when the long side surface  26  is deformed to have a wavelike shape, for example, a dimensional precision and/or positional precision of the deposition material  98  adhering to the organic EL substrate  92  through the through-holes  25  positioned near to the long side surface  26  lower. However, in this embodiment, the log side surface  26  is not connected to the support portion  56 . Thus, in the separation step of separating the deposition mask portion  51  from the support portion  56 , the long side surface  26  is not subjected to a force from the support portion  56 . Thus, it can be prevented that the long side surface  26  is deformed to have a wavelike shape, for example. As a result, it is possible to adhere the deposition material  98  to the organic EL substrate  92 , with excellent dimensional precision and/or positional precision. 
     Next, a method of manufacturing the deposition mask apparatus  10  by combining the deposition masks  20  and the frame  15 . Firstly, the frame  15  is prepared. Following thereto, as shown in  FIG.  25   , the second surface  20   b  of the deposition mask  20  is fixed on the frame  15  by welding or the like. For example, the frame  15  and the deposition mask  20  are overlapped, and the deposition mask  20  is photographed under this state from the side of the first surface  20   a  by means of a camera, for example. At this time, a tensile force may be applied to the deposition mask  20 . After that, based on the photographed image, a position of the deposition mask  20  with respect to the frame  15  is detected. For example, the position of the profile of the deposition mask  20  in the longitudinal direction D 1  is detected. Then, the position of the deposition mask  20  is adjusted such that the position of the deposition mask  20  with respect to the frame  15  is placed in a predetermined position. 
     According to this embodiment, as described above, when the long side surface  26  is seen from the side of the first surface  20   a , the first portion  261  is invisible. In addition, since the first portion  261  spreads up to the first surface  20   a,  namely, since the first end portion  261   a  of the first portion  261  corresponds to the first connection portion  20   e,  when the long side surface  26  is seen from the side of the first surface  20   a,  a surface of the long side surface  26  other than the first portion  261  is invisible. Thus, the profile of the deposition mask  20  in the longitudinal direction D 1  is clearly defined by the first connection portion  20   e  between the first surface  20   a  and the long side surface  26 . Thus, the position of the profile of the deposition mask  20  in the longitudinal direction D 1  can be easily detected. As a result, the position of the profile of the deposition mask  20  in the longitudinal direction D 1  can be more precisely adjusted with respect to the frame  15 . 
     Next, a deposition method for depositing the deposition material  98  onto a substrate such as the organic EL substrate  92  by means of the deposition mask  20  is described. Firstly, the deposition mask apparatus  10  is positioned such that the deposition mask  20  is opposed to the organic EL substrate  92 . In addition, the deposition mask  20  is brought into tight contact with the organic EL substrate  92  by using the magnet  93 . Under this state, the deposition material  98  is evaporated to reach the organic EL substrate  92  through the deposition mask  20 , so that the deposition material  98  can adhere to the organic EL substrate  92  in a pattern corresponding to the through-holes  25  of the deposition mask  20 . In this embodiment, as described above, the position of the profile of the deposition mask  20  in the longitudinal direction D 1  can be easily detected. Thus, the position of the profile of the deposition mask  20  in the longitudinal direction D 1  can be more precisely adjusted with respect to the organic EL substrate  92 . As a result, it is possible to adhere the deposition material  98  onto the organic EL substrate  92  with excellent positional precision. 
     The above-described embodiment can be variously modified. Herebelow, a modification example is described with reference to the drawings according to need. In the below description and the drawings used in the below description, a part that can be similarly constituted to the above embodiment has the same symbol as that of corresponding part the above embodiment, and overlapped description is omitted. In addition, when the effect obtained by the aforementioned embodiment is apparently obtained in the modification examples, description thereof is possibly omitted. 
     In the above-described embodiment shown in  FIG.  20   , there is described the example in which the long side surface  26  separated from another portion of the metal plate  64  is formed by causing the second recess  35  formed in the second surface  64   b  of the metal plate  64  to reach the first surface  64   a.  In this modification example, there is described an example in which the long side surface  26  separated from another portion of the metal plate  64  is formed by causing the first recess  30  formed in the first surface  64   a  of the metal plate  64  and the second recess  35  formed in the second surface  64   b  thereof to communicate with each other. 
       FIG.  26    is a sectional view showing a long side surface  26  of the deposition mask  20  in this modification example. The long side surface  26  includes a first portion  261 , and a second portion  262  connected to a first end portion  261   a  of the first portion  261  to reach the first surface  20   a.  The second portion  262 , which is a part of the first recess  30  that is formed by etching the first surface  64   a  of the metal plate  64  in the first-surface etching step, is recessed inside. According to this modification example, by forming the first recess  30  in a portion of the first surface  64   a  of the metal plate  64 , which becomes the long side surface  26 , even when the metal plate  64  has a large thickness, e.g., even when the metal plate  64  has a thickness of equal to or more than 20 μm or equal to or more than 30 μm, the long side surface  26  can be formed by etching. Although not shown, the short side surface  27  also may include a second portion formed by the first recess  30 , and a first portion formed by a second recess  35 . 
     When the long side surface  26  or the short side surface  27  include the second portion along the first surface  64   a,  the first-surface etching step is preferably performed such that a size in the width direction D 2  of the first recess  30  formed at a portion the first surface  64   a  of the metal plate  64 , which portion becomes the long side surface  26  or the short side surface  27 , is smaller than a size in the width direction D 2  of the first recess  30  formed in the first surface  64   a  of the metal plate  64 , which portion becomes the through-hole  25 . Thus, when the metal plate  64  is conveyed to a location where the second-surface etching step is performed after the first-surface etching step, it can be prevented that the metal plate  64  cracks from the first recess  30  corresponding to the long side surface  26  or the short side surface  27 . 
     As shown in  FIG.  26   , the first end portion  261   a  of the first portion  261  is positioned outside the first connection portion  20   e  at which the first surface  20   a  of the deposition mask  20  and the second portion  262  of the long side surface  26  are connected. Thus, when the deposition mask  20  is seen from the side of the first surface  20   a,  the second portion  262  is visible, but the first portion  261  is invisible. In the second portion  262 , light is scattered in various directions. Thus, in the example shown in  FIG.  26   , the second portion  262  is observed as a portion that seems darker than the first surface  20   a,  or is displayed as such a portion in an image. Thus, the width of the second portion  262  visible from the side of the first surface  20   a  is preferably small. Thus, when the deposition mask  20  is seen from the side of the first surface  20   a,  it is possible to precisely detect the profile of the deposition mask  20 , i.e., the profile of the long side surface  26  in the longitudinal direction D. 
     In  FIG.  26   , a symbol  8  represents a distance in the plane direction of the first surface  20   a,  which is between the first end portion  261   a  and the first connection portion  20   e.  The distance  8  corresponds to a width of the second portion  262  that is visible when seen from the surface of the first surface  20   a.  The distance  8  is equal to or less than 3.5 μm, for example, or preferably equal to or less than 1.0 μm. 
     In  FIG.  26   , a symbol r 3  represents a distance in the normal direction of the deposition mask  20 , which is from the first surface  20   a  up to the first end portion  261   a.  The distance r 3  is equal to or less than 2 μm and equal to or more than 5 μm, for example. Thus, since the second portion  262  has a smaller surface area so that scattering of light caused by the second portion  262  can be reduced. Thus, when the second portion  262  is seen from the side of the first surface  20   a,  the profile of the deposition mask  20 , namely, the profile of the long side surface  26  in the longitudinal direction D 1  can be more precisely detected. In addition, the distance r 3  is preferably smaller than the height r 1  of the wall surface  31  of the first recess  30  constituting the through-hole  25 . In other words, the first end portion  261   a  of the long side surface  26  is positioned closer to the first surface  20   a  than the hole connection portion  41  of the through-hole  25 . 
     In the above-described embodiment, there is described the example in which, in the long side surface  26  of the deposition mask  20 , the first connection portion  20   e  at which the first surface  20   a  and the long side surface  26  are connected and the first end portion  261   a  of the first portion  261  correspond to each other, or a distance therebetween is equal to or less than 3.5 μm. Thus, when seen from the first surface  20   a,  the profile of the deposition mask  20 , which extends in the longitudinal direction D 1 , can be easily detected. Such a technical idea can be applied to the short side surface  27 , in addition to the long side surface  26  or instead of the long side surface  26 . Namely, although not shown, a connection portion at which the first side surface  20   a  and the short side surface  27  are connected, and an end portion of a recessed inside surface in the short side surface  27  along the first side surface  20  may correspond to each other, or a distance therebetween may be equal to or less than 3.5 μμm. Thus, when seen from the first surface  20   a,  the profile of the deposition mask  20 , namely, the profile of the short side surface  27 , which extends in the width direction D 2 , can be easily detected. 
     In addition, in the above-described embodiment, there is described the example in which the deposition mask portion  51  is separated from the support portion  56  by breaking the connection portion  54  between the connection mask portion  51  and the support portion  56  in the short side surface  27  of the intermediate product  50 . However, the example in which the deposition mask portions  51  are separated from the support portion  56  in the short side surface  27  is not particularly limited. For example, the deposition mask portion  51  may be separated from the support portion  56  by cutting a portion providing the short side surface  27  in the intermediate product  50  by using a processing apparatus such as a laser processing apparatus. In this case, the part providing the short side surface  27  in the metal plate  64  may not be equipped with the plurality of second through-portions  55   b.  Alternatively, a groove having a depth not passing through the metal plate  64  may be formed in the first surface  64   a  or the second surface  64   b  of the part providing the short side surface  27  in the metal plate  64 . In this case, by irradiating the metal plate  64  with a laser beam along the groove, a burr caused by the laser processing can be decreased, and/or an amount of cutting dust generated upon laser processing can be reduced. 
     EXAMPLES 
     Next, the embodiment of the disclosure is further described in detail based on examples, but the embodiment of the disclosure is not limited to the below description of the examples as long as it departs from the scope of the present invention. 
     Example 1 
     The metal plate  64  having a thickness of 25 μm was firstly prepared. Then, the aforementioned processing step was performed so that the plurality of through-holes  25  composed of the first recesses  30  and the second recesses  35  were formed in the metal plate  64 . In addition, the second recess  35  reaching the metal plate  64   a  was formed in a portion of the second surface  64   b  of the metal plate  64 , which portion corresponded to the long side surface  26 .  FIG.  27    shows an observation result of the section of the long side surface  26 . In addition,  FIG.  28 A  shows a result of the deposition mask  20  including the long side surface  26  shown in  FIG.  27   , when observed from the side of the first surface  20   a,  and  FIG.  28 B  shows a result observed from the side of the second surface  20   b.    
     As shown in  FIG.  28 B , when the deposition mask  20  is observed from the side of the second surface  20   b,  the first portion  261  is visible. On the other hand, when the deposition mask  20  is observed from the side of the first surface  20   a,  the first portion is invisible. Thus, the position of the profile of the deposition mask  20  in the longitudinal direction D 1  can be easily detected. 
     Example 2 
     The metal plate  64  having a thickness of 30 μm was prepared. Then, the aforementioned processing step was performed so that the plurality of through-holes  25  composed of the first recesses  30  and the second recesses  35  were formed in the metal plate  64 . In addition, the first recess  30  was formed in a portion of the first surface  64   a  of the metal plate  64 , which portion corresponded to the long side surface  26 , and the second recess  35  in communication with the first recess  30  was formed in a portion of the second surface  64   b,  which portion corresponded to the long side surface  26 .  FIG.  29 A  shows an observation result of the section of the long side surface  26 . The long side surface  26  includes the first portion  261  formed of a part of the second recess  35 , and the second portion  262  formed of a part of the first recess  30 . 
       FIG.  29 B  is an enlarged sectional view showing the second portion  262  of the long side surface  26  of  FIG.  29 A . A distance δ between the first end portion  261   a  and the first connection portion  20   e  was 0.7 μm. 
     When the deposition mask  20  including the long side surface  26  shown in  FIGS.  29 A and  29 B  is seen from the side of the second surface  20   b,  the first portion  261  is visible. On the other hand, when the same deposition mask  20  is seen from the side of the first surface  20   a,  the first portion  261  is invisible but the second portion  262  is visible. Since the distance δ between the first end portion  261   a  and the first connection portion  20   e  is 0.7 μm, a width of the second portion  262  that is visible when the deposition mask  20  is observed from the side of the first surface  20   a  is also 0.7 μm. Thus, even when the deposition mask  20  is observed by using a camera from the side of the first surface  20   a  in a state where a visual field size of the camera in the width direction D 2  is enlarged to be about 3.5 μm, both the first end portion  261   a  and the first connection portion  20   e  can be confirmed. Thus, the profile of the deposition mask  20  can be easily detected. 
     Example 3 
     The deposition mask  20  was manufactured similarly to the aforementioned Example 1, excluding that the metal plate  641  having a thickness of 15 μm was used.  FIG.  30    shows an observation result of the section of the long side surface  26 . As shown in  FIG.  27   , also in this example, similarly to the Example 1, the first portion  261  formed of a curved surface that is curved to be recessed inside spreads from the second surface  20   b  up to the first surface  20   a.  In this case, the first end prion  261   a  of the first portion  261  corresponds to the first connection portion  20   e.  Thus, when the deposition mask  20  is seen from the side of the first surface  20   a,  the first portion  261  is invisible. Thus, when the deposition mask  20  is seen along the normal direction of the first surface  20   a,  the position of the profile of the deposition mask  20  in the longitudinal direction D 1  can be easily detected.