Abstract:
The present invention aims to improve the printing accuracy. Further, the invention aims to reduce the size of the screen compared with the conventional processing pattern, and to reduce the cost of the screen. Further, it is also an object of the invention to lengthen the life of the screen. According to the invention, the screen printer for performing the screen printing using the screen plate includes: the table placed facing the screen plate; and the screen sealing unit which nearly seals the space between the screen plate and the table.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a screen printer used for such as printing a resist in case of printing or etching during the process of electrically wiring on a board. The invention relates to, in particular, a screen printer used for a screen printing method in which gas pressure between a screen mesh and a work is made higher than gas pressure at a side of printing using a squeegee of the screen mesh.  
           [0003]    2. Description of the Related Art  
           [0004]    [0004]FIG. 9 shows a conventional technique of a screen printer.  
           [0005]    In FIG. 9, a reference numeral  1  shows a screen,  3  shows a squeegee,  5  shows a screen frame,  6  shows a work,  8  shows ink, and  10  shows a table.  
           [0006]    According to the conventional screen printing, as shown in FIG. 9, a clearance of several mm is placed between the screen  1  and the work  6  which is a board to be processed. After supplied to the screen  1 , the ink is spread by the squeeze  3  toward the user&#39;s side, while the squeegee  3  presses the screen  1  downward with stretching the screen  1  so that the screen  1  adheres to the work  6  of the board, and then the screen  1  is removed from the work  6  of the board due to the tension of the screen. Printing is thus performed on the work  6  of the board.  
           [0007]    As for the clearance between the screen  1  and the work  6 , for example, the clearance of 2-6 mm is placed when the internal size of the screen frame is 500 mm. Further, as greater the internal size of the screen frame becomes; such as 1,000 mm, 2,500 mm, and more, it is also required to make the clearance bigger. There are some problems in the conventional printing method, in which the clearance, for example, of 2-6 mm is placed between the screen  1  and the work  6 . As the screen  1  is stretched for printing, the printing accuracy is not sufficient. It is required to make the screen  1  larger than the work of the board, which increases the cost of the screen  1 . Moreover, as the screen  1  is stretched for printing, the screen  1  does not last long.  
         SUMMARY OF THE INVENTION  
         [0008]    The present invention aims to improve the printing accuracy.  
           [0009]    Further, the invention aims to make the screen smaller compared with the conventional processing pattern, which enables to reduce the cost of the screen.  
           [0010]    Further, the invention aims to lengthen the life of the screen.  
           [0011]    According to the present invention, a screen printer for performing screen printing using a screen plate includes:  
           [0012]    a table placed facing the screen plate;  
           [0013]    a screen sealing unit for nearly sealing a space between the screen plate and the table, and  
           [0014]    the screen sealing unit includes a screen receiving unit placed facing the screen plate and  
           [0015]    a sealing aid unit placed facing the table.  
           [0016]    The screen printer of the invention further includes an elastic body, and the sealing aid unit is placed slidable along the table and is pressed to the screen receiving unit by the table through the elastic body.  
           [0017]    In the screen printer of the invention, the screen sealing unit further includes a packing material, and  
           [0018]    the screen receiving unit has a projection part circularly formed, and the projection part is pressed to the sealing aid unit through the packing material.  
           [0019]    According to another aspect of the invention, a screen printer for performing screen printing using a screen plate and a squeegee, includes a table placed facing the screen plate and having an opening,  
           [0020]    the screen printer performs screen printing on a work placed on the table using the screen plate and the squeegee, and supplies gas having a higher pressure than a pressure of atmosphere of a side of the screen plate opposite to the table, and  
           [0021]    the opening supplies gas to the screen plate, and is formed outside the work placed on the table and at least at one of fore and rear in a printing direction of the squeegee as a long slot which is long in an approximately right angle direction against the printing direction of the squeegee.  
           [0022]    The screen printer of the invention further includes:  
           [0023]    a regulator for controlling a pressure of the gas; and  
           [0024]    an opening valve for releasing a pressure which is increased by the gas supplied into the space between the screen plate and the table.  
           [0025]    In the screen printer of the invention, the screen printer performs screen printing on a work using a squeegee, and  
           [0026]    the table includes a supply hole which is formed at least at one of fore and rear of the table in a printing direction of the squeegee and supplies gas toward the screen plate with an angle slanted to the work.  
           [0027]    In the screen printer of the invention, the supply hole formed at least at one of sides of the table in a printing direction of the squeegee and supplies gas to the screen plate.  
           [0028]    The screen printer of the invention further includes:  
           [0029]    a filter for filtering the gas supplied to the space which is nearly sealed between the screen plate and the table; and  
           [0030]    a compressed gas generating unit for increasing a pressure of the gas filtered and supplying the gas of which the pressure is increased to the supply hole.  
           [0031]    In the screen printer of the invention, the screen printer performs screen printing using ink including solvent, and the gas includes the solvent.  
           [0032]    The screen printer of the invention further includes a supply hole for supplying gas into a space which is nearly sealed by the screen plate, the table, and the screen sealing unit. 
       
    
    
     BRIEF EXPLANATION OF THE DRAWINGS  
       [0033]    A complete appreciation of the present invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:  
         [0034]    [0034]FIG. 1 shows a top view of a table of a screen printer according to the first embodiment of the invention;  
         [0035]    [0035]FIG. 2 shows a cross section of the table of the screen printer according to the first embodiment;  
         [0036]    [0036]FIG. 3 shows another cross section of the table of the screen printer according to the first embodiment;  
         [0037]    [0037]FIG. 4 illustrates printing status of the first embodiment, when a screen sealing unit is omitted;  
         [0038]    [0038]FIG. 5 shows a plumbing diagram of compressed gas;  
         [0039]    [0039]FIG. 6 explains printing in which the pressure of the gas of a part under the screen is made higher than the air pressure;  
         [0040]    [0040]FIG. 7 explains printing in which the pressure of the gas of a part over the screen is made higher than the air pressure;  
         [0041]    [0041]FIG. 8 explains printing in which air is applied to the screen;  
         [0042]    [0042]FIG. 9 explains a conventional screen printing;  
         [0043]    [0043]FIG. 10 shows a top view of a table of a screen printer according to the fifth embodiment of the invention;  
         [0044]    [0044]FIG. 11 shows a cross section of FIG. 10 taken along with a line A-A;  
         [0045]    [0045]FIG. 12 shows a top view of a table of a screen printer according to the sixth embodiment of the invention;  
         [0046]    [0046]FIG. 13 shows a cross section of FIG. 12 taken along with a line B-B;  
         [0047]    [0047]FIG. 14 shows circulation flow diagram of compressed gas; and  
         [0048]    [0048]FIG. 15 shows a plumbing diagram of the seventh embodiment. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0049]    Embodiment 1.  
         [0050]    [0050]FIG. 1 shows a top view of a table of a screen printer according to the first embodiment of the invention.  
         [0051]    In FIG. 1, a reference numeral  10  shows a table,  121  shows an opening which is a part of a supply hole, and  123  shows a suction hole. The opening  121  is formed as a long slot which is long in an approximately right angle direction against the printing direction. The suction hole  123  places and fixes a printing material on the table by sucking. The opening  121  is formed at a position so as not to contact with the printing material when the printing material is fixed to the table by sucking with the suction hole  123 . The opening  121  is formed so as to be equal to or longer than a length of the user&#39;s side in the printing direction out of four sides of the top face of the work  6 . Namely, the width of the opening  121  is at least the width of the work which is placed on the table toward the direction of printing. As discussed below, the opening  121  supplies gas to the screen plate  100 .  
         [0052]    [0052]FIG. 2 shows a cross section of the table of the screen printer according to the first embodiment of the invention.  
         [0053]    In FIG. 2, a reference numeral  1  shows a screen,  5  shows a screen frame,  11  shows a spring support,  100  shows a screen plate,  131  shows a screen receiving unit,  132  shows a sealing aid unit,  133  shows a projection part,  141  shows a sponge which is a part of the first packing material,  142  shows a sponge which is a part of the second packing material, and  150  shows a spring material which is an example of an elastic body. The screen plate  100  has the screen  1  and the screen frame  15 . A screen sealing unit has the screen receiving unit  131  and the sealing aid unit  132 . The screen receiving unit  131  has the projection part  133 . The table  10  is the same as one shown in FIG. 1.  
         [0054]    In FIG. 2, the table  10  is placed facing the screen plate  100 . The table  10  has an approximate square prismatic shape, and the sealing aid unit  132  is retained by a clearance spring at the side of the table  10 . Namely, the sealing aid unit  132  is placed so as to freely slide along the table  10 . The sealing aid unit  132  is formed as an approximate square frame matching the shape of the table  10 , and the sealing aid unit  132  is retained at the side of the table  10  through plural pieces of the spring material  150  by the spring support  11 , of which the bottom face is fixed to the table  10  using plural bolts. The sealing aid unit  132  is pressed and retained by the screen receiving unit  131  through the sponge  142  of which a top face is formed into an approximate square frame matching to the shape of the top face of the sealing aid unit  132 . The screen receiving unit  131  is fixed to the printer body. The projection part  133  which is a part of the screen receiving unit  131  is formed as an approximate square frame shape so as not to stick out of the frame of the sealing aid unit  132  to the inside nor the outside. The projection part  133  is formed as a circular shape and projected downward so as to press the sponge  142 . To make the projection part  133  projected downward, the pressing area is made smaller than a case where the sponge  142  is pressed by a large plane, and the pressure is increased against a certain pressing power compared with the case where the sponge  142  is pressed by the large plane. The sealing aid unit  132  is inserted between the spring support  11  and the projection part  133  through the sponge  142  and held by them with the repulsion power of the spring material  150 , and the sealing aid unit  132  presses the projection part  133 . Namely, the sealing aid unit  132  is pressed to the screen receiving unit  131  by the table  10  through the elastic body. On the other hand, the projection part is pressed to the sealing aid unit  132  through the sponge  142 . The table  10  can slide upward/downward to adjust its position to the size of the material to be printed. At this time, the spring material  150  should be stretchable so as to cover the sliding amount of the table  10 , so that the table  10  presses the projection part  133  even if the table  10  slides.  
         [0055]    Accordingly, the space between the projection part  133  and the sealing aid unit  132  is sealed even if the table  10  slides.  
         [0056]    The top face of the screen receiving unit  131  is fixed to the screen frame  5  of the screen plate  100  through the sponge  141  so as to press the sponge  141 . The sponge  141  is formed as an approximate square frame shape to match the shape of the contacting face of the screen receiving unit  131  and the screen frame  5 .  
         [0057]    Accordingly, the space between the screen receiving unit  131  and the screen frame  5  is sealed.  
         [0058]    Accordingly, the screen sealing unit nearly seals the space between the screen plate  100  and the table  10 .  
         [0059]    [0059]FIG. 3 shows a cross section of the table of the screen printer of the first embodiment.  
         [0060]    In FIG. 3, a reference numeral  122  shows a compressed air supplying unit which is one example of the supplying hole. FIG. 3 illustrates the compressed air supplying unit  122 , which is actually installed in the embodiment of FIG. 2 but not shown in FIG. 2. The table  10  is the same as one in FIGS. 1 and 2. The screen plate  100  is the same as one in FIG. 2. The compressed air supplying unit  122  is provided below the table  10 , connected to the opening  121  placed at the upper face of the table  10  shown in FIG. 1, and the compressed air supplying unit  122  supplies gas to the screen plate  100 .  
         [0061]    [0061]FIG. 4 shows printing status of the first embodiment, in which the screen sealing unit is omitted.  
         [0062]    In FIG. 4, a reference numeral  3  shows a squeegee,  8  shows ink, and  6  shows a work. The opening  121  is the same as one in FIG. 1. The screen  1 , the screen frame  5 , the screen plate  100  are the same as ones in FIG. 2. The compressed air supplying unit  122  is the same as one in FIG. 3. The table  10  is the same as ones in FIGS. 1, 2, and  3 .  
         [0063]    In FIG. 4, printing is performed on the work  6  by movement of the squeegee  3  which presses the work  6  and applies the ink  8  to the work  6 . Namely, the printing direction of the squeegee  3  is the same as the printing direction discussed in the explanation of FIG. 1.  
         [0064]    In FIG. 4, as discussed in the explanation of FIG. 1, the opening  121  is formed at a position where the opening does not contact to the work  6  when the work  6  is fixed to the table by sucking with the suction hole  123 . Namely, the opening  121  is formed outside the work  6  placed on the table  10  and at the rear of the squeegee  3  in the printing direction. The opening  121  applies the gas which is supplied by the compressed air supplying unit  122  to the screen plate  100 . When an atmosphere pressure below the screen  1  becomes higher than an atmosphere pressure above the screen  1 , namely, the atmosphere pressure below the screen  1  is higher than the atmosphere pressure of the side of the screen  1  opposite to the table which is faced the screen plate  100 , it becomes possible to print with easily keeping a clearance between the screen  1  and the work  6  even if the clearance between the screen  1  and the work  6  is small when the printing is performed using the squeegee  3 .  
         [0065]    Here, it is preferable to use either of air and nitrogen for the gas supplied by the opening  121 . Further, it is preferable to use clean air so as to prevent the work  6  from pollution. To prevent the work  6  from pollution, argon, etc. can be used as well as nitrogen which is inert gas.  
         [0066]    [0066]FIG. 5 shows a plumbing diagram of compressed gas.  
         [0067]    In FIG. 5, a reference numeral  200  shows a regulator,  210  shows a valve which is an example of an opening valve, and  220  shows a compressed gas generating/supplying unit. The compressed air supplying unit  122  is the same as ones in FIGS. 3 and 4. The compressed gas generating/supplying unit  220  includes the regulator  200  and the valve  210 .  
         [0068]    In FIG. 5, the regulator  200  controls the pressure of the supplied gas. After printing, the valve  210  releases the pressure which has been increased by the gas supplied to the nearly sealed space between the screen plate  100  and the table  10 .  
         [0069]    The compressed gas generating/supplying unit  220  supplies gas, of which the pressure is higher than the pressure of the atmosphere of the side of the screen  1  opposite to the table  10  placed facing the screen plate  100 , to the compressed air supplying unit  122 .  
         [0070]    As described above, according to the first embodiment, the screen printer for performing screen printing using the screen plate includes:  
         [0071]    the table  10  placed facing the screen plate  100 ; and  
         [0072]    the screen sealing unit which nearly seals the space between the screen plate  100  and the table  10 .  
         [0073]    In the screen printer of the first embodiment, the screen sealing unit has the first and second packing materials and includes:  
         [0074]    the screen receiving unit  131  placed facing the screen plate  100  through the first packing material; and  
         [0075]    the screen sealing aid unit  132  placed facing the screen receiving unit  131  through the second packing material.  
         [0076]    The screen printer of the first embodiment further includes the elastic body, and  
         [0077]    the sealing aid unit  132  is placed so as to freely slide along the table  10  and is pressed to the screen receiving unit  131  by the table  10  through the elastic body.  
         [0078]    According to the first embodiment, the screen receiving unit  131  includes the projection unit  133  which is formed as a circular shape and pressed to the sealing aid unit  132  through the second packing material.  
         [0079]    According to the first embodiment, the elastic body is the spring material.  
         [0080]    According to the first embodiment, the table  10  includes the supply hole which supplies gas to the screen plate  100 .  
         [0081]    The screen printer of the first embodiment performs printing on the work  6  using the squeegee  3 , and  
         [0082]    the supply hole is formed outside the work  6  placed on the table  10  and at least at one side of fore and rear of the printing direction of the squeegee  3 .  
         [0083]    In the screen printer of the first embodiment, the supply hole has the opening  121  is formed as a long slot which is long in an approximately right angle direction against the printing direction.  
         [0084]    According to the first embodiment, the opening  121  is formed so as to have a width equal to or longer than the width of the work  6  placed on the table  10  in the printing direction of the squeegee  3 .  
         [0085]    According to the first embodiment, the gas is either of air and nitrogen.  
         [0086]    The screen printer of the first embodiment further includes the compressed gas generating/supplying unit, which supplies gas having higher pressure than the atmosphere of the side of the screen  1  opposite to the table  10  placed facing the screen plate  100 .  
         [0087]    According to the first embodiment, the compressed gas generating/supplying unit includes:  
         [0088]    the regulator  200  for controlling the pressure of the gas; and  
         [0089]    the opening valve which releases the pressure increased by the gas supplied to the space between the screen plate  100  and the table  10 .  
         [0090]    Embodiment 2.  
         [0091]    [0091]FIG. 6 explains printing by applying gas having higher pressure than the air pressure to the space below the screen.  
         [0092]    In FIG. 6, a reference numeral  1  shows a screen,  3  shows a squeegee,  5  shows a screen frame,  6  shows a work,  10  shows a table,  12  shows a pressure holding frame,  13 , and  15  show high pressure gas supplying pipes. According to the printing method shown in FIG. 6, the gas pressure of the space between the screen  1  and the work  6  is increased so as to become higher than the gas pressure of the squeegee  3  side of the screen  1  by introducing the high pressure gas having higher pressure than the air pressure to the space between the screen  1  and the work  6 . The pressure holding frame  12  is provided between the screen frame  5  of the screen  1  and the table  10 , which seals the space between the screen  1  and the table  10  except the opening. The high pressure gas having higher pressure than the air pressure is introduced through the high pressure gas supplying pipe  15 , so that the pressure of the gas in the space between the screen  1  and the work  6  is made higher than the air pressure.  
         [0093]    The clearance between the work  6  and the screen  1  is preferably set to equal to or less than 2 mm and equal to or greater than 0.01 mm.  
         [0094]    The ink  8  is applied to the screen  1 , and printing is performed on the work  6  using the squeegee  3 .  
         [0095]    During printing, there always exists power to expand toward the side of the screen  1  opposite to the work  6  applied to the screen  1  due to the differential with the air pressure. Accordingly, it becomes possible to perform printing using the squeegee  3  with easily keeping the clearance between the screen  1  and the work  6  even if the clearance between the screen  1  and the work  6  is small.  
         [0096]    Embodiment 3.  
         [0097]    [0097]FIG. 7 explains printing by applying gas having lower pressure than the air pressure to the space over the screen.  
         [0098]    In FIG. 7, according to the printing method of the third embodiment, the gas pressure of the space between the screen  1  and the work  6  is increased so as to become higher than the gas pressure of the squeegee  3  side of the screen  1  by reducing the gas pressure of the squeegee  3  side of the screen  1  so as to become lower than the air pressure. A pressure holding case  20  is provided on the screen  1  at the side opposite to the work  6  to hold the gas pressure lower than the air pressure.  
         [0099]    The gas existing inside the pressure holding case  20  is set to lower than the air pressure by sucking the gas with a suction pipe  16  using a blower or vacuum pump, and so on.  
         [0100]    The clearance between the work  6  and the screen  1  is preferably set to equal to or less than 2 mm and equal to or greater than 0.01 mm.  
         [0101]    The ink  8  is applied to the screen  1 , and printing is performed on the work  6  using the squeegee  3 .  
         [0102]    During printing, there always exists power to expand toward the side of the screen  1  opposite to the work  6  applied to the screen  1  due to the differential with the air pressure. Accordingly, it becomes possible to perform printing using the squeegee  3  with easily keeping the clearance between the screen  1  and the work  6  even if the clearance between the screen  1  and the work  6  is small.  
         [0103]    Embodiment 4.  
         [0104]    [0104]FIG. 8 shows a printing method in which the screen  1  and the work  6  is separated by blowing high pressure gas into the space between the screen  1  and the work  6  in the proceeding direction of the squeegee or along the screen  1  in the proceeding direction of the squeegee.  
         [0105]    A gas nozzle is provided below the screen  1  so as to blow the high pressure gas into the space between the screen  1  and the work  6  so that the gas flows in the proceeding direction of the squeegee or along the screen  1  in the proceeding direction of the squeegee.  
         [0106]    The clearance between the work  6  and the screen  1  is preferably set to equal to or less than 2 mm and equal to or greater than 0.01 mm.  
         [0107]    The ink  8  is applied to the screen  1 , and printing is performed on the work  6  using the squeegee  3 .  
         [0108]    During printing, the screen  1  is separated from the work  6  by blowing the gas having higher pressure than the air pressure toward the screen  1 . Accordingly, it becomes possible to perform printing using the squeegee  3  with easily keeping the clearance between the screen  1  and the work  6  even if the clearance between the screen  1  and the work  6  is small.  
         [0109]    Embodiment 5.  
         [0110]    [0110]FIG. 10 shows a top view of the table of the screen printer according to the fifth embodiment.  
         [0111]    In FIG. 10, a reference numeral  300  shows a hole (an example of the supply hole), and  301  shows a slit.  
         [0112]    [0112]FIG. 11 shows a cross section of FIG. 10 taken along the line A-A.  
         [0113]    Other configuration elements are the same as ones in the first embodiment.  
         [0114]    As shown in FIGS. 10 and 11, the table  10  has, in addition to the opening  121  in FIG. 1, another opening  121  (an example of a supply hole) is provided outside the work  6  which is placed on the table  10 , located at the fore of the printing direction of the squeegee  3 , and formed as a long slot which is long in an approximately right angle direction against the printing direction of the squeegee  3 .  
         [0115]    The two openings  121 , located at the fore and the rear of the printing direction of the squeegee  3 , are formed so as to supply gas against the screen  1  of the screen plate  100  with an angle which is slanted to the work  6 . Namely, the openings are formed so as to slantingly blow gas into the space between the screen  1  and table  10 . A slit  301  which covers a part of the top face of the opening  121  is provided at the opening  121  so as to control the flow of the gas and to supply the gas to the screen  1  of the screen plate  100  with an angle which is slanted to the work  6 .  
         [0116]    Further, a hole  300  is provided outside the work  6  placed on the table  10  at both the fore and the rear of printing direction of the squeegee  3  so as to supply the gas toward the screen  1  of the screen plate  100 .  
         [0117]    Plural holes  300  are provided with a predetermined interval at both sides, however, the holes  300  can be provided at only one side. Further, the hole  300  supplies the gas upward to the screen  1 .  
         [0118]    Here, the screen printer of the invention has one compressed air supplying unit  122  as shown in FIG. 3, however, plural compressed air supplying units can be provided at plural supplying holes, respectively.  
         [0119]    As described above, according to the fifth embodiment, plural supplying units for the gas so as to supply the gas from various directions.  
         [0120]    Further, though the opening  121  supplies the gas upward to the screen  1  in the first embodiment, it is better to form the opening  121  so as to slantingly blow the gas into the space between the screen  1  and the table  10 .  
         [0121]    As described above, according to the fifth embodiment, in the screen printer for printing on the work  6  using the squeegee  3 , the supply hole is formed outside the work  6  placed on the table  10  and formed at least at one of the fore and the rear of the printing direction of the squeegee  3 .  
         [0122]    Further, according to the fifth embodiment, in the screen printer for printing on the work  6  using the squeegee  3 ,  
         [0123]    the table  10  has a supply hole which is formed outside the work  6  placed on the table  10  and formed at least at one of the fore and the rear of the printing direction of the squeegee  3  so as to supply the gas toward the screen plate  100  with the angle which is slanted to the work  6 .  
         [0124]    Further, according to the fifth embodiment, the supply hole is formed outside the work  6  placed on the table  10  and formed at least at one of the fore and the rear of the printing direction of the squeegee  3  so as to supply the gas toward the screen plate  100 .  
         [0125]    Embodiment 6.  
         [0126]    [0126]FIG. 12 shows a top view of a screen printer according to the sixth embodiment.  
         [0127]    [0127]FIG. 13 shows a cross section of FIG. 12 taken along the line B-B.  
         [0128]    In FIG. 13, a reference numeral  320  shows an opening.  
         [0129]    In FIGS. 12 and 13, the openings  121  of the fifth embodiment provided at the fore and the rear are respectively divided into two. The opening  121  is provided between the fixing bolts. Instead of the hole  300  of the fifth embodiment, an opening  320  is provided at the table  10  so as to supply the gas to the space surrounded by the screen plate  100 , the table  10 , the screen receiving unit  131 , and the sponge  142 . Namely, the opening  320  blows the gas from the side of the table.  
         [0130]    Other elements of the present embodiment are the same as ones in the fifth embodiment.  
         [0131]    In this way, it becomes possible to make the printing area large for the predetermined table  10 .  
         [0132]    Embodiment 7.  
         [0133]    [0133]FIG. 14 shows circulation flow diagram of compressed gas.  
         [0134]    In FIG. 14, a reference numeral  401  shows a filter,  402  shows a source of compressed gas (a part of the compressed gas generating unit), and  403  shows a printing unit.  
         [0135]    A circular system of the seventh embodiment sends the gas, which is supplied to the almost sealed space among the screen plate  100  and the table  10 , to the filter  401 , removes foreign objects, that is, filters the gas, sends the gas to the source  402  of compressed gas through the filter  401 , increases the pressure of the gas, and supplies the gas to the compressed air supplying unit  122  of the printing unit  403 .  
         [0136]    In the first embodiment, it is assumed that compressed gas such as dry air or nitrogen is supplied from outside, and the compressed gas which is supplied to the almost sealed space of the device is released to the outside by the valve. The compressed gas is thus assumed to be abandoned.  
         [0137]    However, there might be a case in which evaporation amount of volatile solvent, etc. included in the ink  8  might be large by printing with constantly using the air introduced from the outside or fresh nitrogen compared with printing without using the compressed gas.  
         [0138]    Accordingly, as shown in FIG. 14, the circular system can be provided to circulate the supplied gas inside the device.  
         [0139]    [0139]FIG. 15 shows a plumbing diagram of the seventh embodiment.  
         [0140]    In FIG. 15, a reference numeral  501  shows a pump (an example of a compressed gas generating unit),  502  shows a valve, and  503  shows another valve.  401  shows a filter as well as in FIG. 14. Other configuration elements are the same as ones in FIG. 5.  
         [0141]    The pump  501  of the seventh embodiment can be replaced with a blower.  
         [0142]    At first, the valve  503  is opened, and the valve  502  is closed. The regulator  200  controls the pressure of the gas supplied to the compressed air supplying unit  122 . Once the gas is supplied, the valve  503  is closed, and the valve  502  is opened. After printing, the valve  210  releases the pressure increased by the gas supplied into the almost sealed space between the screen plate and the table  10 .  
         [0143]    After filtered by the filter  401 , the released gas is compressed by the pump  501  and returned to the regulator  200  through the valve  502 . Thus, the gas which has been used once is circulated and recycled.  
         [0144]    In the seventh embodiment, the circulating method is used to restrain the evaporation of the volatile solvent, etc. included in the ink  8 , however, it is possible to use gas including the solvent, which is used for the ink  8 , in itself.  
         [0145]    As discussed above, the screen printer of the seventh embodiment has the compressed gas generating/supplying unit  220 , and the compressed gas generating/supplying unit  220  includes:  
         [0146]    the filter  401  which filters the gas supplied to the space between the screen plate  100  and the table  10 ; and  
         [0147]    the compressed gas generating unit which increases the pressure of the gas filtered by the filter  401  and supplies the gas of which the pressure is increased to the supply hole.  
         [0148]    Further, according to the seventh embodiment, the screen printer performs screen printing using the ink including the solvent, and  
         [0149]    the gas includes the solvent.  
         [0150]    Embodiment 8.  
         [0151]    Another embodiment will be explained, in which an address electrode is formed by printing on a plasma display backplate of 20 inches using silver paste.  
         [0152]    The clearance between the screen  1  and the glass board is set to 0.5 mm, a pressure holding frame is provided between the screen frame and the table which sucks the board, and high pressure air having 0.1 MPa is introduced to a part under the screen frame from a high pressure gas supply pipe.  
         [0153]    The size of the screen  1  is set larger than the size of the printing pattern by about 80 mm.  
         [0154]    Printing is performed using silver paste, which is a product of Namics Corporation, with a stainless  320  mesh.  
         [0155]    Conventionally, the clearance is set to 3-5 mm for printing, however, at this time, there is no problem to print with the clearance of 0.5 mm, keeping the glass board and the screen  1  separated.  
         [0156]    As explained above, by making the pressure of the gas between the screen  1  and the work  6  is made higher than the pressure of the gas at the side of printing using the squeegee of the screen  1 , a force is operated to the screen mesh to expand toward the side of the screen  1  opposite to the work  6 . Accordingly, when printing is performed on the work  6  using the squeegee with the screen  1 , by removing the screen  1  from the work  6  using the differential of the pressure of the gas, it becomes possible to perform screen printing with smaller clearance between the screen mesh and the board than the conventional method.  
         [0157]    To make the pressure of the gas between the screen  1  and the work  6  higher than the pressure of the gas at the side of printing using the squeegee of the screen  1 , the space between the screen  1  and the work  6  is sealed except the opening of the screen  1  and blocked from the outside, and the high pressure gas having higher pressure than the air pressure is introduced into the space between the screen  1  and the work  6 . In this way, the pressure of the gas between the screen  1  and the work  6  is made higher than the air pressure. In another way, by sealing the space of the moving section of the squeegee and the side of printing using the squeegee of the screen  1  except the opening to block from the outside, the pressure of the gas at the side of printing using the squeegee of the screen  1  is made smaller than the air pressure using the blower or the vacuum pump, etc.  
         [0158]    To remove the screen  1  from the work when the screen printing is performed using the high pressure gas, the high pressure gas having higher pressure than the air pressure is blown to the screen  1  so that the high pressure gas should flow into the clearance between the screen  1  and the work  6  in the proceeding direction of the squeegee or along the screen in the proceeding direction of the squeegee.  
         [0159]    It is preferable to set the clearance between the screen  1  and the work  6  to equal to or smaller than 2 mm and equal to or greater than 0.01 mm.  
         [0160]    As has been described, in each of the foregoing embodiments, the printing is performed with the small clearance between the screen  1  and the work  6  except a certain part, which is pressed by the squeegee  3 , by supplying the gas before the printing, or by making the pressure of the gas between the screen  1  and the work  6  smaller than the pressure of the gas at the side of the screen  1  which contacts the squeegee  3  during a series of operation before printing, on printing, and after printing.  
         [0161]    Further, in each of the foregoing embodiments, the gas is supplied from the table  10  or the screen frame  5 , however, the application of the embodiments is not limited to this example. It is possible to supply the gas from any element as long as such element supplies the gas into the nearly sealed space between the screen  1  and the work  6 . For example, the gas can be supplied from the screen receiving unit  131 , the sealing aid unit  132 , the sponges  141 , or  142 .  
         [0162]    As discussed above, the screen printer according to each of the foregoing embodiments has a supply hole which supplies the gas into the space nearly sealed by the screen plate  100 , the table  10  and the screen sealing unit.  
         [0163]    When the screen printing is performed on the work  6  with the screen  1  using the squeegee, by making the pressure of the gas between the screen  1  and the work  6  higher than the pressure of the gas at the side of printing using the squeegee of the screen  1 , the screen can be removed from the work  6  using the differential of the pressure of the gas. Accordingly, it becomes possible to perform the screen printing with smaller clearance between the screen mesh and the board than the conventional method, which lengthens the life of the screen and improves the printing accuracy.  
         [0164]    Having thus described several particular embodiments of the present invention, various alterations, modifications, and improvements will readily occur to those skilled in the art. Such alterations, modifications, and improvements are intended to be part of this disclosure, and are intended to be within the spirit and scope of the present invention. Accordingly, the foregoing description is by way of example only, and is not intended to be limiting. The present invention is limited only as defined in the following claims and the equivalents thereto.