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BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a construction structure of wall surface comprised in an inner wall or an outer wall of a building. 
     2. Description of the Related Art 
     Conventionally, outer and inner walls of buildings are constructed through fitting of a plurality of building boards onto a building frame. A sealing material is provided for joining the building boards, for countering dimensional changes of the building boards over time, and for waterproofing the building. 
     For instance, Japanese Patent Application Publication No. 2003-343024 discloses the feature of providing a hat joiner, having a linear projection, between the end faces of adjacent external facing members, and forming a joint by providing a sealing material at a portion formed between the front face of the linear projection and the end face of the external facing members. 
     However, the joint formed by providing the sealing material is likely to be noticeable, which is problematic. Also, sealing deteriorates over time, and performance in terms of durability, waterproofness and so forth becomes impaired, which is likewise problematic. Further, the passage of time gives rise to discoloration and impaired appearance, and makes it necessary to repair and/or renew the deteriorated sealing material. 
     Accordingly, Japanese Patent Application Publication No. 2003-328529 discloses a vertical joint structure wherein siding panels are arranged on a joiner to which a waterproof material is attached, such that the end portions of the siding panels are butt-joined to each other. 
     No sealing material is required in the structure of Japanese Patent Application Publication No. 2003-328529, and hence the problem of noticeable joints that form by providing a sealing material does not occur, nor is repair or renewal necessary upon deterioration of the sealing over time. However, it is difficult to manufacture the siding panels with good enough precision so as to preclude gaps from appearing upon butt-joining to other siding panels, and the joining portions between siding panels are readily noticeable. Also, the dimensions of the siding panels change over time, and hence gaps appear at the joining portions between siding panels, or small gaps become larger, among other problems. 
     SUMMARY OF THE INVENTION 
     The present invention provides a construction structure of wall surface that has no sealing material and in which a joining portion between building boards is inconspicuous. 
     The present invention provides a construction structure of wall surface. 
     A construction structure of wall surface includes: a hat joiner; and a building board. The hat joiner has a fixing plate portion and a design portion, and the building board has a design portion extending linearly on a surface. A joint at which the design portion of the hat joiner constitutes a design surface, and a joint at which the design portion of the building board constitutes a design surface, are formed in a same direction, by arranging the building board in plurality to left and right, or above and below, of the design portion of the hat joiner. In the present invention, a width of the joint at the design portion of the hat joiner is the same as a width of each of the design portions on the surface of each of the building boards. Alternatively, a color of the design portion of the hat joiner is the same as a color of each of the design portions of each of the building boards. Therefore, a joint at which the design portion of the hat joiner constitutes a design surface cannot be readily distinguished from the design portion of the surface of the building boards, and thus the joint is inconspicuous. Also, no sealing material is provided, and hence the problem of deterioration of the sealing material over time does not occur, which renders unnecessary repairs or renewal associated with deterioration. The building boards are disposed with a gap in between, and hence dimensional changes of the building boards are hardly noticeable, and pose no problem. 
     In the construction structure of wall surface of the present invention, a top section of the design portion of the hat joiner may be disposed flush at the same height as top sections of surfaces of adjacent building boards, or may be disposed higher than surfaces of adjacent building boards. Preferably, the top section of the design portion of the hat joiner is disposed higher than the surfaces of adjacent building boards, since unevenness among the building boards becomes inconspicuous in that case. That is, unevenness occurring between building boards becomes inconspicuous, even if the thicknesses of building boards that are adjacent across the hat joiner are dissimilar, by disposing the top section of the design portion of the hat joiner at a higher position. 
     Accordingly, the top section of the design portion of the hat joiner may be disposed lower than surfaces of adjacent building boards. In this case as well, unevenness between building boards becomes hardly noticeable. 
     The design portions of the building boards may be formed by coating, or may be formed by projections and/or recesses, or by a combination of the foregoing. 
     Also, an end portion of surface of the building board may be chamfered at a joint comprising the design portion of the hat joiner and the building board. In this case, preferably, a shape identical to the chamfer of the end portion of surface of the building board is provided in the design portions of the building boards, in a same direction as that of the chamfer, since, as a result, a joint at which the design portion of the hat joiner constitutes a design surface cannot be readily distinguished from each of the design portions on the surface of each of the building boards, and thus the joint is inconspicuous. 
     The present invention allows providing a construction structure of wall surface that has no sealing material and in which a joining portion between building boards is inconspicuous. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram of an embodiment of a construction structure of wall surface according to the present invention, viewed from above; 
         FIG. 2  is a diagram of the construction structure of wall surface illustrated in  FIG. 1  viewed from the front; 
         FIG. 3  is a perspective-view diagram of a hat joiner of the construction structure of wall surface illustrated in  FIGS. 1 and 2 ; 
         FIG. 4  is a diagram of another embodiment of the construction structure of wall surface according to the present invention, viewed from above; 
         FIG. 5  is a diagram of yet another embodiment of the construction structure of wall surface according to the present invention, viewed from above; 
         FIG. 6  is a diagram of yet another embodiment of the construction structure of wall surface according to the present invention, viewed from above; 
         FIG. 7  is a diagram of the construction structure of wall surface illustrated in  FIG. 6  viewed from the front; 
         FIG. 8  is a diagram of yet another embodiment of the construction structure of wall surface according to the present invention, viewed from above; 
         FIG. 9  is a diagram of yet another embodiment of the construction structure of wall surface according to the present invention, viewed from above; 
         FIG. 10  is a diagram of yet another embodiment of the construction structure of wall surface according to the present invention, viewed from above; and 
         FIG. 11  is a diagram of yet another embodiment of the construction structure of wall surface according to the present invention, viewed from above. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention will be explained in detail below with reference to accompanying drawings. 
       FIGS. 1 and 2  are diagrams, viewed from above and from the front, of an embodiment of a construction structure of wall surface according to the present invention.  FIG. 3  is a perspective-view diagram of a hat joiner of the construction structure of wall surface illustrated in  FIGS. 1 and 2 . 
     The construction structure of wall surface illustrated in  FIGS. 1 and 2  comprises a hat joiner A 1  and building boards B 1 . 
     The hat joiner A 1  comprises a design portion a 11 , connecting portions a 12  and fixing plate portions a 13 , and is an elongated member as illustrated in  FIG. 3 . The design portion a 11  is the most frontward-protruding portion of the hat joiner A 1 . The connecting portions a 12 , a 12  extend backwards from both ends, left and right, of the design portion a 11 , and the fixing plate portions a 13 , a 13  extend each horizontally towards the right and left, from respective connecting portions a 12 , a 12 . On the surface of the building boards B 1  there is provided a plurality of coating films b 11 , as a design portion, so as to traverse vertically the board up and down. The horizontal width of the coating films b 11  is the same as the horizontal width of the design portion a 11  of the hat joiner A 1 . The color of the design portion a 11  of the hat joiner A 1  is also the same as that of the coating films b 11 . 
     In the construction structure of wall surface illustrated in  FIGS. 1 and 2 , two building boards B 1 , B 1  are fixed, left and right, to the hat joiner A 1  that is fixed to a building frame (not shown) in a state where the rear faces of the fixing plate portions a 13  abut the surface of the building frame. The two building boards B 1 , B 1  are fixed so as to be several millimeters spaced apart from the fixing plate portions a 13 , a 13  of the hat joiner A 1 , in order to provide a ventilation layer on the rear face side of the building boards B 1 , B 1 . When the construction structure of wall surface is viewed from the front, a design pattern is formed by a design portion of the coating films b 11  of the building boards B 1 , and by the design portion a 11  of the hat joiner A 1 , as illustrated in  FIG. 2 . However, the horizontal width and the color of the coating films b 11  are the same as those of the design portion a 11  of the hat joiner A 1 , and the coating films b 11  are parallel to the design portion a 11 . Therefore, the mutual joints cannot be readily distinguished, and the joining portion between building boards B 1 , B 1  is inconspicuous. Since no sealing material is present at the joining portion between the building boards B 1 , B 1 , there occurs no deterioration of the sealing material over time. This renders unnecessary repairs or renewal. The design portion a 11  of the hat joiner A 1  is disposed at the same height as the surface of the building boards B 1 , B 1 , and hence the joining portion between the building boards B 1 , B 1  is hardly noticeable. 
       FIG. 4  is a diagram of another embodiment of the construction structure of wall surface according to the present invention, viewed from above. 
     The construction structure of wall surface illustrated in  FIG. 4  comprises a hat joiner A 2  and building boards B 2 . The hat joiner A 2  is identical to the hat joiner A 1  of  FIG. 3 , and comprises a design portion a 21 , connecting portions a 22  and fixing plate portions a 23 . The building boards B 2  are identical to the building boards B 1  illustrated in  FIGS. 1 and 2 , and have a plurality of coating films b 21 , as a design portion, on the surface. In the construction structure of wall surface illustrated in  FIG. 4 , however, the positions of the surface of the building boards B 2  and of the hat joiner A 2  are different from those in the construction structure of wall surface illustrated in  FIGS. 1 and 2 . In the construction structure of wall surface illustrated in  FIG. 4 , the position of the design portion a 21  of the hat joiner A 2  is lower than the surface of the building boards B 2 , B 2 . However, the horizontal width and color of the coating films b 21  in the present the construction structure of wall surface are the same as the horizontal width and color of the design portion a 21  of the hat joiner A 2 , and the coating films b 21  are parallel to the design portion a 21 . Therefore, the mutual joints cannot be readily distinguished, and the joining portion between building boards B 2 , B 2  is inconspicuous. Since no sealing material is present at the joining portion between the building boards B 2 , B 2 , there occurs no deterioration of the sealing material over time. This renders unnecessary repairs or renewal. The position of the design portion a 21  of the hat joiner A 2  is lower than the surface of the building boards B 2 , B 2 , and hence any unevenness that may occur between the building boards B 2 , B 2  becomes inconspicuous. 
       FIG. 5  is a diagram of yet another embodiment of the construction structure of wall surface according to the present invention, viewed from above. 
     The construction structure of wall surface illustrated in  FIG. 5  comprises a hat joiner A 3  and building boards B 3 . The hat joiner A 3  is identical to the hat joiner A 1  of  FIG. 3 , and comprises a design portion a 31 , connecting portions a 32  and fixing plate portions a 33 . However, the building boards B 3  are different from the building boards B 1  of  FIGS. 1 and 2  in that now the design portion is formed by recesses b 31 . The recesses b 31  are provided as a plurality thereof in the surface of the building boards B 3 , so as to traverse vertically the board up and down. The horizontal width of the recesses b 31  is the same as the horizontal width of the design portion a 31  of the hat joiner A 3 . In the construction structure of wall surface illustrated in  FIG. 5 , the positions of the surface of the building boards B 3  and of the hat joiner A 3  are different from those in the construction structure of wall surface illustrated in  FIGS. 1 and 2 . In the construction structure of wall surface illustrated in  FIG. 5 , the height of the surface of the design portion a 31  of the hat joiner A 3  is the same as the height of the surface of the recesses b 31  of the building boards B 3 , B 3 . As a result, the joining portion between the building boards B 3 , B 3  is hardly noticeable also in the construction structure of wall surface illustrated in  FIG. 5 . In this construction structure of wall surface as well, the horizontal width of the recesses b 31  is the same as the horizontal width of the design portion a 31  of the hat joiner A 3 . Therefore, the mutual joints cannot be readily distinguished, and the joining portion between building boards B 3 , B 3  is inconspicuous. Since no sealing material is present at the joining portion between the building boards B 3 , B 3 , there occurs no deterioration of the sealing material over time. This renders unnecessary repairs or renewal. 
       FIGS. 6 and 7  are diagrams, viewed from above and from the front, of yet another embodiment of the construction structure of wall surface according to the present invention. 
     The construction structure of wall surface illustrated in  FIGS. 6 and 7  comprises a hat joiner A 4  and building boards B 4 . The hat joiner A 4  is identical to the hat joiner A 1  of  FIG. 3 , and comprises a design portion a 41 , connecting portions a 42  and fixing plate portions a 43 . However, the building boards B 4  are different from the building boards B 1  of  FIGS. 1 and 2  in that now the design portion is formed by recesses b 41  and oblique portions b 42 , b 43 . The recesses b 41  and oblique portions b 42 , b 43  are provided as a plurality thereof in the surface of the building boards B 4 , so as to traverse vertically the board up and down. The horizontal width and the color of the recesses b 41  are the same as the horizontal width of the design portion a 41  of the hat joiner A 4 . Chamfer portions b 44 , b 45  are provided at the left end and the right end of the surface of the building boards B 4 , so as to traverse vertically the board up and down. The horizontal width and color of the oblique portions b 42 , b 43  are the same as the horizontal width and color of the chamfer portions b 44 , b 45 . In the construction structure of wall surface illustrated in  FIGS. 6 and 7 , the positions of the surface of the building boards B 4  and of the hat joiner A 4  are different from those in the construction structure of wall surface illustrated in  FIGS. 1 and 2 . In the construction structure of wall surface illustrated in  FIGS. 6 and 7 , the height of the surface of the design portion a 41  of the hat joiner A 4  is the same as the height of the surface of the recesses b 41  of the building boards B 4 , B 4 . As a result, the joining portion between the building boards B 4 , B 4  is hardly noticeable also in the construction structure of wall surface. In this construction structure of wall surface as well, the horizontal width of the recesses b 41  is the same as the horizontal width of the design portion a 41  of the hat joiner A 4 . The horizontal width and color of the oblique portions b 42 , b 43  are the same as the horizontal width and color of the chamfer portions b 44 , b 45 . Therefore, the mutual joints cannot be readily distinguished, and the joining portion between building boards B 4 , B 4  is inconspicuous. Since no sealing material is present at the joining portion between the building boards B 4 , B 4 , there occurs no deterioration of the sealing material over time. This renders unnecessary repairs or renewal. Also, breakage becomes less likely by providing the chamfer portions b 44 , b 45  at the left end and the right end of the surface of the building boards B 4 . 
       FIG. 8  is a diagram of yet another embodiment of the construction structure of wall surface according to the present invention, viewed from above. 
     The construction structure of wall surface illustrated in  FIG. 8  comprises a hat joiner A 5  and building boards B 5 . The hat joiner A 5  is identical to the hat joiner A 1  of  FIG. 3 , and comprises a design portion a 51 , connecting portions a 52  and fixing plate portions a 53 . The building boards B 5  are identical to the building boards B 1  illustrated in  FIGS. 1 and 2 , and have a plurality of coating films b 51 , as a design portion, on the surface. In the construction structure of wall surface illustrated in  FIG. 8 , however, the positions of the surface of the building boards B 5  and of the hat joiner A 5  are different from those in the construction structure of wall surface illustrated in  FIGS. 1 and 2 . In the construction structure of wall surface illustrated in  FIG. 8 , the position of the design portion a 51  of the hat joiner A 5  is higher than the surface of the building boards B 5 , B 5 . However, the horizontal width and color of the coating films b 51  in the present the construction structure of wall surface are the same as the horizontal width and color of the design portion a 51  of the hat joiner A 5 , and the coating films b 51  are parallel to the design portion a 51 . Therefore, the mutual joints cannot be readily distinguished, and the joining portion between building boards B 5 , B 5  is inconspicuous. Since no sealing material is present at the joining portion between the building boards B 5 , B 5 , there occurs no deterioration of the sealing material over time. This renders unnecessary repairs or renewal. The position of the design portion a 51  of the hat joiner A 5  is higher than the surface of the building boards B 5 , B 5 , and hence any unevenness that may occur between the building boards B 5 , B 5  becomes inconspicuous. 
       FIG. 9  is a diagram of yet another embodiment of the construction structure of wall surface according to the present invention, viewed from above. 
     The construction structure of wall surface illustrated in  FIG. 9  comprises a hat joiner A 6  and building boards B 6 . The hat joiner A 6  is identical to the hat joiner A 1  of  FIG. 3 , and comprises a design portion a 61 , connecting portions a 62  and fixing plate portions a 63 . However, the building boards B 6  are different from the building boards B 1  of  FIGS. 1 and 2  in that now the design portion is formed by projections b 61 . The projections b 61  are provided as a plurality thereof in the surface of the building boards B 6 , so as to traverse vertically the board up and down. The horizontal width of the projections b 61  is the same as the horizontal width of the design portion a 61  of the hat joiner A 6 . A coating of the same color as that of the design portion a 61  is applied onto the surface of the projections b 61 . In the construction structure of wall surface illustrated in  FIG. 9 , the positions of the surface of the building boards B 6  and of the hat joiner A 6  are different from those in the construction structure of wall surface illustrated in  FIGS. 1 and 2 . In the construction structure of wall surface illustrated in  FIG. 9 , the height of the surface of the design portion a 61  of the hat joiner A 6  is the same as the height of the surface of the projections b 61  of the building boards B 6 , B 6 . As a result, the joining portion between the building boards B 6 , B 6  is hardly noticeable also in the construction structure of wall surface illustrated in  FIG. 9 . In this construction structure of wall surface as well, the horizontal width and color of the projections b 61  are the same as the horizontal width and color of the design portion a 61  of the hat joiner A 6 . Therefore, the mutual joints cannot be readily distinguished, and the joining portion between building boards B 6 , B 6  is inconspicuous. Since no sealing material is present at the joining portion between the building boards B 6 , B 6 , there occurs no deterioration of the sealing material over time. This renders unnecessary repairs or renewal. 
       FIG. 10  is a diagram of yet another embodiment of the construction structure of wall surface according to the present invention, viewed from above. 
     The construction structure of wall surface illustrated in  FIG. 10  comprises a hat joiner A 7  and building boards B 7 . The hat joiner A 7  comprises a design portion a 71 , connecting portions a 72  and fixing plate portions a 73 , but differs from the hat joiner A 1  of  FIG. 3  in that the design portion a 71  is formed to have a cross section shaped as a circular arc. The building boards B 7  are also different from the building boards B 1  of  FIGS. 1 and 2  in that now the design portion is formed by projections b 71 . The projections b 71  are provided as a plurality thereof in the surface of the building boards B 7 , so as to traverse vertically the board up and down. The horizontal width of the projections b 71  is the same as the horizontal width of the design portion a 71  of the hat joiner A 7 . In the construction structure of wall surface illustrated in  FIG. 10 , the positions of the hat joiner A 7  and of the surface of the building boards B 7  are different from those in the construction structure of wall surface illustrated in  FIGS. 1 and 2 . In the construction structure of wall surface illustrated in  FIG. 10 , the height of the top section of the surface of the design portion a 71  of the hat joiner A 7  is identical to the height of the top section of the projections b 71  of the building boards B 7 , B 7 . As a result, the joining portion between the building boards B 7 , B 7  is hardly noticeable also in the construction structure of wall surface illustrated in  FIG. 10 . In this construction structure of wall surface as well, the horizontal width of the projections b 71  is the same as the horizontal width of the design portion a 71  of the hat joiner A 7 . Therefore, the mutual joints cannot be readily distinguished, and the joining portion between building boards  37 , B 7  is inconspicuous. Since no sealing material is present at the joining portion between the building boards B 7 , B 7 , there occurs no deterioration of the sealing material over time. This renders unnecessary repairs or renewal. 
       FIG. 11  is a diagram of yet another embodiment of the construction structure of wall surface according to the present invention, viewed from above. 
     The construction structure of wall surface illustrated in  FIG. 11  comprises a hat joiner A 8  and building boards B 8 . The hat joiner A 8  comprises a design portion a 81 , connecting portions a 82  and fixing plate portions a 83 , but differs from the hat joiner A 1  of  FIG. 3  in that the design portion a 81  has an oblique portion at the left and right ends. The building boards B 8  are also different from the building boards B 1  of  FIGS. 1 and 2  in that now the design portion is formed by projections b 81 . The projections b 81  are provided as a plurality thereof in the surface of the building boards B 8 , so as to traverse vertically the board up and down. The horizontal width of the projections b 81  is the same as the horizontal width of the design portion a 81  of the hat joiner A 8 . Like the design portion a 81 , the projections b 81  have each an oblique portion at the left and right ends. In the construction structure of wall surface illustrated in  FIG. 11 , the positions of the surface of the building boards B 8  and of the hat joiner A 8  are different from those in the construction structure of wall surface illustrated in  FIGS. 1 and 2 . In the construction structure of wall surface illustrated in  FIG. 11 , the height of the top section of the surface of the design portion a 81  of the hat joiner A 8  is identical to the height of the top section of the projections b 81  of the building boards B 8 , B 8 . As a result, the joining portion between the building boards B 8 , B 8  is hardly noticeable also in the construction structure of wall surface illustrated in  FIG. 11 . In this construction structure of wall surface as well, the horizontal width of the projections b 81  is the same as the horizontal width of the design portion a 81  of the hat joiner A 8 . Therefore, the mutual joints cannot be readily distinguished, and the joining portion between building boards B 8 , B 8  is inconspicuous. Since no sealing material is present at the joining portion between the building boards B 8 , B 8 , there occurs no deterioration of the sealing material over time. This renders unnecessary repairs or renewal. 
     Embodiments of the present invention have been explained above, but the present invention is not limited thereto, and can accommodate various modifications without departing from the scope of the invention as set forth in the appended claims. For instance, in  FIGS. 1 to 11 , the joint by the design portion of the hat joiner, as well as and the design portions on the surface of the building boards, are all provided in the form of vertical joints, but may also be provided in the form of horizontal joints 
     As described above, the present invention allows providing a construction structure of wall surface having no sealing material and in which joining portions between building boards are inconspicuous.

Summary:
A construction structure of wall surface includes: a hat joiner; and a building board. The hat joiner has a fixing plate portion and a design portion, and the building board has a design portion extending linearly on a surface. A joint at which the design portion of the hat joiner constitutes a design surface, and a design pattern at which the design portion of the building board constitutes a design surface, are formed in a same direction, by arranging the building board in plurality to left and right, or above and below, of the design portion of the hat joiner. A width of the joint at the design portion of the hat joiner is the same as a width of each of the design portions on the surface of each of the building boards.