Patent Publication Number: US-10308041-B2

Title: Printing apparatus

Description:
BACKGROUND 
     1. Technical Field 
     The present invention relates to a printing apparatus. 
     2. Related Art 
     A printing apparatus that discharges liquid (ink) to a medium such as paper or a printing sheet from a head and performs printing on the medium is known. 
     For example, a printing apparatus (printer apparatus) disclosed in JP-A-2011-16268 includes a head discharging ink to a medium, a first platen provided in a drawing region to be drawn by the head, a second platen positioned on a downstream side of the drawing region in a transporting direction of the medium, and a guide member (medium pressing member) pressing the medium from a top of the first platen to a top of the second platen. 
     According to this configuration, since the medium is widely pressed by the medium pressing member, skewing of the medium or floating of the medium from the platen is suppressed, and thereby the medium can be stably transported. 
     The medium pressing member is disposed between the head and the platen, and between the head and the medium. In order to increase a quality of the image being printed on the medium, an interval between the head and the medium needs to be reduced, and thus the medium pressing member being disposed between the head and the medium needs to be thin. 
     In the printing apparatus disclosed in JP-A-2011-16268, since a thin medium pressing member is widely provided, compared to a case in which the thin medium pressing member is narrowly provided, a mechanical stiffness of the medium pressing member is weakened, and the medium pressing member is easily deformed. Therefore, in a case in which a force which floats the medium from the platen is strong, the medium pressing member is deformed due to the strong force, floating of the medium from the platen is difficult to be suppressed, and for example, there is a concern that jam of the medium may be generated. Further, if the medium pressing member is deformed, the medium pressing member is interfered with the head, and there is a concern that the head may malfunction. 
     SUMMARY 
     The invention can be realized in the following aspects or application examples. 
     Application Example 1 
     According to this application example, there is provided a printing apparatus including a medium supporting portion that supports a medium being transported in a transporting direction, a printing portion that performs printing on the medium in a printing region, a medium pressing member that is attached to the medium supporting portion and includes a plurality of materials stacked thereon, and a heating portion that heats the medium pressing member, the medium pressing member includes a base portion being attached to the medium supporting portion, and an eaves portion which forms a gap with the medium supporting portion and suppresses floating of the medium from the medium supporting portion, the base portion includes a first material for forming a first surface being attached to the medium supporting portion, and a second material for forming a second surface on an opposite side of the first surface, and a coefficient of thermal expansion of the first material is higher than a coefficient of thermal expansion of the second material. 
     The base portion of the medium pressing member in which the first material having the high coefficient of thermal expansion and the second material having the low coefficient of thermal expansion are sequentially stacked on the medium supporting portion are attached to (are fixed to) the medium supporting portion. When the medium pressing member is heated by the heating portion, the first material thermally extends more than the second material, and thus a force (hereinafter, refer to as deformation force) which deforms the end portion of the base portion in a direction of being separated from the medium supporting portion acts on the medium pressing member. Since the medium pressing member is fixed to the medium supporting portion, a force (Hereinafter, refer to as drag force) against the deformation force acts on the medium pressing member, and deformation of the medium pressing member is suppressed. The drag force is a force pressing the medium pressing member against the medium supporting portion. That is, when the medium pressing member is heated by the heating portion, the force pressing the medium pressing member against the medium supporting portion acts, and the medium pressing member becomes difficult to be deformed. 
     Therefore, even in a case in which the force applied from the medium, which deforms the medium pressing member, is strong, when the medium pressing member is heated by the heating portion, the force (drag force) pressing the medium pressing member against the medium supporting portion acts, the medium pressing member becomes difficult to be deformed, and the medium pressing member is capable of suppressing floating of the medium from the medium supporting portion. Further, if the medium pressing member becomes difficult to be deformed, a concern that the medium pressing member may be interfered with the printing portion and the printing portion may malfunction can be suppressed. 
     Application Example 2 
     In the printing apparatus according to the application example, it is preferable that the medium pressing member include an attaching portion for attaching the base portion to the medium supporting portion, and the attaching portion include a first attaching portion which is disposed on an upstream side of the printing region in the transporting direction, and a second attaching portion which is disposed on a downstream side of the printing region in the transporting direction. 
     The attaching portion attaching (fixing) the base portion to the medium supporting portion is disposed on both of an upstream side of the printing region in the transporting direction and a downstream side of the printing region in the transporting direction, and thus the medium pressing member becomes difficult to be deformed in the printing region. 
     Therefore, in the printing region, the medium pressing member is difficult to be deformed, floating of the medium from the medium supporting portion can be suppressed. 
     Application Example 3 
     In the printing apparatus according to the application example, it is preferable that the first material and the second material be metals. 
     If the first material and the second material are constituted of a metal, compared to a case of being constituted of a resin, heat or liquid resistance is increased, and thus the medium pressing member can be difficult to be deteriorated. 
     Application Example 4 
     In the printing apparatus according to the application example, it is preferable that the first material be a resin, and the second material be a metal. 
     The first material is a foundation on which the medium pressing member is attached to the medium supporting portion. If the first material is constituted of a resin, compared to a case of being constituted of a metal, for example, the first material is easily processed into a complicated shape by a molding process or the like. Therefore, even in a case in which the medium supporting portion has a complicated shape, the medium pressing member can be attached to the medium supporting portion having the complicated shape by processing the first material according to the complicated shape of the medium supporting portion. 
     Application Example 5 
     In the printing apparatus according to the application example, it is preferable that at least any one of the first material and the second material have elasticity, include a warp curved from a center portion toward an end portion so as to be separated from the medium supporting portion in a case in which the base portion is provided on the medium supporting portion, and be disposed along the medium supporting portion in a state in which the warp is corrected in a case in which the base portion is attached to the medium supporting portion. 
     In order to correct the warp which is curved so as to be separated from the medium supporting portion, a force correcting the curved warp needs to act on the medium pressing member. The force correcting the curved warp is a force pulling the medium pressing member to be close to the medium supporting portion, and a force pressing the medium pressing member against the medium supporting portion. Accordingly, when the medium pressing member is attached to the medium supporting portion in a state in which the curved warp to be separated from the medium supporting portion is corrected, the force pressing the medium pressing member against the medium supporting portion (force correcting the curved warp) acts on the medium pressing member. 
     Therefore, when the medium pressing member is heated by the heating portion, the force pressing the medium pressing member against the medium supporting portion (force correcting the curved warp) acts on the medium pressing member with the drag force, and thus the medium pressing member becomes more difficult to be deformed than a case in which only the drag force acts. 
     Application Example 6 
     In the printing apparatus according to the application example, it is preferable that at least any one of the first material and the second material be constituted of a shape memory alloy which memorizes a shape of the warp curved from the center portion toward the end portion so as to be separated from the medium supporting portion in a case of being heated by the heating portion. 
     In a case in which the medium pressing member is heated by the heating portion, from the center portion to the end portion, the medium pressing member (a shape memory alloy) is deformed in a curved warp so as to be separated from the medium supporting portion. In a case in which the medium pressing member is heated by the heating portion, since the medium pressing member is attached to the medium supporting portion in a state in which the curved warp shape is suppressed, a force suppressing the curved warp shape acts on the medium pressing member. The force suppressing the curved warp shape is a force pulling the medium pressing member to be close to the medium supporting portion, and the force pressing the medium pressing member against the medium supporting portion. 
     Therefore, in a case in which the medium pressing member is heated by the heating portion, the force pressing the medium pressing member against the medium supporting portion (force suppressing curved warp shape) acts on the medium pressing member with the drag force, and thus the medium pressing member becomes more difficult to be deformed than a case in which only the drag force acts. 
     Application Example 7 
     In the printing apparatus according to the application example, it is preferable that the heating portion be disposed on an opposite side of the medium pressing member of the medium supporting portion, and heat both the medium pressing member and the medium through the medium supporting portion. 
     Since the same heating portion heats both the medium pressing member and the medium, compared to a case in which different heating portions respectively heat the medium pressing member and the medium, the number of the heating portions can be reduced and low costs can be achieved. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be described with reference to the accompanying drawings, wherein like numbers reference like elements. 
         FIG. 1  is a schematic sectional view illustrating a schematic configuration of a printing apparatus according to Embodiment 1. 
         FIG. 2  is a schematic plan view illustrating vicinity where a medium supporting portion is disposed. 
         FIG. 3  is a schematic sectional view illustrating the vicinity where the medium supporting portion is disposed. 
         FIG. 4  is a schematic sectional view illustrating the vicinity where the medium supporting portion is disposed. 
         FIG. 5  is a schematic sectional view of a medium pressing member taken along V-V line of  FIG. 2 . 
         FIG. 6  is a schematic sectional view illustrating a state of a base portion of the medium pressing member according to Embodiment 1. 
         FIG. 7A  is a schematic sectional view illustrating a state of a base portion of a medium pressing member according to a comparison example. 
         FIG. 7B  is a schematic sectional view illustrating the state of the base portion of the medium pressing member according to the comparison example. 
         FIG. 8  is a schematic sectional view illustrating a medium pressing member mounted on a printing apparatus according to Embodiment 2. 
         FIG. 9  is a schematic sectional view illustrating a state of a base portion of the medium pressing member according to Modification Example 2. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Hereinafter, embodiments of the invention will be described with reference to drawings. Such embodiments indicate aspects of the invention, are not limited thereto, and can be arbitrarily changed within a range of a technical idea of the invention. In addition, in each of following drawings, since each layer or each part is set to have a size of a degree to be recognizable on the drawings, a scale of each layer or each part may be different from the actual scale. 
     Embodiment 1 
     Outline of Printing Apparatus 
       FIG. 1  is a schematic sectional view illustrating a schematic configuration of a printing apparatus according to Embodiment 1.  FIG. 2  is a schematic plan view of vicinity where a medium supporting portion is disposed.  FIGS. 3 and 4  are schematic sectional views of vicinity where the medium supporting portion is disposed. 
     Also, in  FIGS. 1 to 4 , description of unnecessary configuration components will be omitted. Further, in  FIG. 2 , a printing region E is illustrated by being hatched with a dashed line. The printing region E means a region where a head  15  which is an example of a “printing portion” is moved.  FIG. 3  is a sectional view of a base portion  20  of a medium pressing member  19  taken along a transporting direction Y of a medium M, and is a view illustrating a state of the base portion  20  of the medium pressing member  19 .  FIG. 4  is a sectional view of a region, in which an eaves portion  28  of the medium pressing member  19  is disposed, taken along the transporting direction Y of the medium M, and is a view illustrating a state of the eaves portion  28  of the medium pressing member  19 . 
     At first, an outline of a printing apparatus  11  according to the embodiment will be described with reference to  FIGS. 1 to 3 . 
     As illustrated in  FIG. 1 , the printing apparatus  11  according to the embodiment is a large format printer (LFP) handling a relatively large media (medium), and includes a medium supporting portion  32  which supports the medium M being transported in the transporting direction Y by a transporting portion  13 , and a head  15  which is disposed on an opposite side of the medium supporting portion  32  with respect to the medium M and discharges ink. 
     Also, the head  15  is an example of a “printing portion performing printing on a medium in a printing region”. 
     Further, an upstream side medium supporting portion  31  is disposed on an upstream side of the medium supporting portion  32  in the transporting direction Y, and a downstream side medium supporting portion  33  is disposed on a downstream side of the medium supporting portion  32  in the transporting direction Y. The medium M is supported by the upstream side medium supporting portion  31 , the medium supporting portion  32 , and the downstream side medium supporting portion  33 , and is transported using the transporting portion  13  in the transporting direction Y illustrated by an arrow in the drawings. 
     The transporting portion  13  includes a pair of transporting rollers  13   a  and  13   b  in which one is driven by a driving source (not illustrated), and transports the medium M in the transporting direction Y by clipping and rotating the medium M. The pair of transporting rollers  13   a  is disposed on the upstream side of the medium supporting portion  32  in the transporting direction Y, and the pair of transporting rollers  13   b  is disposed on the downstream side of the medium supporting portion  32  in the transporting direction Y. 
     In the printing apparatus  11 , the medium M is transported in a continuous form paper by being unwound from a roll of paper RS, which is wound around a supplying reel  14   a  in a roll shape. Also, ink is discharged from the head  15  to the medium M, and thus an image is printed on the medium M. The medium M on which the image is printed is wound around a winding reel  14   b  in a roll shape. 
     The head  15  is mounted in a carriage  17  which is movable in a width direction X while being able to slide and in contact with guide shafts  16   a  and  16   b  extending to the width direction X intersecting the transporting direction Y of the medium M. In detail, the head  15  is attached to the carriage  17  and is movable in the width direction X with the carriage  17 , such that a nozzle forming surface, in which nozzles discharging ink to the medium M are formed, faces the medium supporting portion  32 . 
     A ink supplying tube  18   a , which can be deformed following the carriage  17  moving in the width direction X, is connected to a connecting tube  18  through a connecting portion  18   b  attached to a part of the carriage  17 . The connecting tube  18  is connected to an ink flowing passage (not illustrated) provided inside the carriage  17 . Ink accommodated in a liquid accommodating portion (not illustrated) is supplied to the head  15  through the ink supplying tube  18   a , the connecting tube  18 , and the ink flowing passage provided inside the carriage  17 . 
     As illustrated in  FIG. 2 , the medium supporting portion  32  is provided with a supporting surface  32   a  having a substantially rectangular shape on a side facing the head  15  based on the width direction X of the medium M as a longitudinal direction, and the medium M is sucked and supported to the supporting surface  32   a  of the medium supporting portion  32 . In the supporting surface  32   a  of the medium supporting portion  32 , a groove portion  46  and a suction hole  47  are provided. The groove portion  46  extends in the width direction X. 
     The medium pressing member  19  is attached to the supporting surface  32   a  of the medium supporting portion  32 . Details thereof will be described later, but the medium pressing member  19  is attached to the medium supporting portion  32 , and has a configuration in which a plurality of materials (first material  21  (refer to  FIG. 5 ) and second material  22  (refer to  FIG. 5 )) are stacked. 
     The medium pressing member  19  is a member (elongated member) which is long in the transporting direction Y and is formed by a half-blanking process or a bending process. The medium pressing member  19  is configured with a first medium pressing member  19 A disposed on a right side in the drawing and a second medium pressing member  19 B disposed on a left side in the drawing. The first medium pressing member  19 A and the second medium pressing member  19 B are a member having the same shape as each other. In description hereinafter, the first medium pressing member  19 A and the second medium pressing member  19 B may be simply referred to as the medium pressing member  19 . 
     As illustrated in  FIG. 3 , a suction chamber forming member  35  is assembled with a lower portion of the medium supporting portion  32 . Also, a negative pressure chamber  36  is formed by the medium supporting portion  32  and the suction chamber forming member  35 . The suction hole  47  described above penetrates through the medium supporting portion  32  and communicates with the negative pressure chamber  36  formed on the lower portion of the medium supporting portion  32 . 
     The suction chamber forming member  35  includes a suction chamber  37  communicating with the negative pressure chamber  36 , and an exhaust fan  38  discharging air in the suction chamber  37  to the outside. When the exhaust fan  38  is driven, the air in the suction chamber  37  is discharged to the outside, the suction chamber  37  becomes negatively pressurized, the negative pressure chamber  36  communicating with the suction chamber  37  also becomes negatively pressurized. The medium M is sucked and supported by the supporting surface  32   a  of the medium supporting portion  32  through the suction hole  47  communicating with the negative pressure chamber  36 . 
     In the printing apparatus  11 , when an image is printed on the medium M by discharging ink from the head  15 , the exhaust fan  38  is driven, the suction chamber  37  and the negative pressure chamber  36  are negatively pressurized, and the medium M is sucked and supported by the supporting surface  32   a  of the medium supporting portion  32  through the suction hole  47 . 
     Return to  FIG. 1 , heaters  41 ,  42 , and  43  are respectively attached to the upstream side medium supporting portion  31 , the medium supporting portion  32 , and the downstream side medium supporting portion  33 . The heaters  41 ,  42 , and  43 , for example, are a tube heater, and are respectively attached to a lower surface (surface opposite to surface supporting medium M) of the upstream side medium supporting portion  31 , the medium supporting portion  32 , and the downstream side medium supporting portion  33  through an aluminum tape or the like. Also, when a power source portion  56  supplies power to the heaters  41 ,  42 , and  43 , the medium M can be heated from a rear side of the medium M. 
     For example, temperatures of a pre-heater  41  and a platen heater  42  are set to approximately 40° C., and a temperature of the after-heater  43  is set to approximately 50° C. higher than the temperature of the pre-heater  41  or the platen heater  42 . 
     Also, the platen heater  42  is an example of a “heating portion”. 
     The pre-heater  41  gradually increases the temperature of the medium M from a room temperature up to a heating temperature (approximately 40° C.) of the platen heater  42  through the upstream side medium supporting portion  31 . The platen heater  42  is disposed on an opposite side of the medium pressing member  19  of the medium supporting portion  32 , heats both the medium pressing member  19  and the medium M through the medium supporting portion  32 , and quickly dries ink landed on the medium M. The after-heater  43  increases the temperature of the medium M up to a temperature (approximately 50° C.) higher than a heating temperature (approximately 40° C.) of the platen heater  42  through the downstream side medium supporting portion  33 , and completely dries the ink landed on the medium M to be fixed to the medium M before the medium M is wound around the winding reel  14   b.    
     When the carriage  17  moves (reciprocates and moves) in the width direction X of the medium M, the ink is discharged from the head  15  with respect to the medium M sucked and supported by the medium supporting portion  32 , the printing apparatus  11  having such a configuration prints an image including letters, figures, and the like on the medium M by alternatively repeating a liquid discharging operation in which the head  15  discharges the ink while moving in the width direction X and a transporting operation in which the medium M is transported in the transporting direction Y by the transporting portion  13 . 
     Medium Pressing Member 
     Next, with reference to  FIG. 2  to  FIG. 4 , the medium pressing member  19  will be described in detail. 
     The medium pressing member  19  is a member, which is attached to the supporting surface  32   a  of the medium supporting portion  32  and suppresses floating of the medium M from the medium supporting portion  32 , and forms an gap with the medium supporting portions  32  on which an end portion of the medium M is disposed. The medium pressing member  19  is disposed between the head  15  and the medium supporting portion  32 , and between the head  15  and the medium M. 
     The medium pressing member  19  is disposed so as to be in contact (interfered) with the head  15  in a case in which the head  15  mounted in the carriage  17  moves in the width direction X. That is, the medium pressing member  19  is disposed so as to be interfered with the head  15  in a case in which the head  15  moves in the printing region E. 
     An interval between the medium supporting portion  32  and the head  15  is approximately 1.5 mm to 2.0 mm. A thickness of the medium M is approximately 0.5 mm or less. Since the medium pressing member  19  is disposed between the head  15  and the medium M, in order to make the medium pressing member  19  not interfere with the head  15 , a thickness of the medium pressing member  19  is preferably 1 mm or less, and more preferably, 0.5 mm or less in consideration of a tolerance of each member. 
     As illustrated in  FIG. 2 , the medium pressing member  19  has a longer shape in the transporting direction Y than the width direction X, and is a thin elongated member having a thickness of 1 mm or less. The medium pressing member  19  includes the base portion  20  being disposed on the center and eaves portions  28  being disposed on both ends of the base portion  20 . That is, in the medium pressing member  19 , one eaves portion  28 , the base portion  20 , and another eaves portion  28  are sequentially disposed along the width direction X. 
     Further, the base portion  20  protrudes to a downstream side of the eaves portion  28  in the transporting direction Y. A knob portion  27  is formed on both end sides of a part protruding to the downstream side of the base portion  20  in the transporting direction Y. A user can grab the knob portion  27 , and moves (slides) the medium pressing member  19  in an extending direction (width direction X) of the groove portion  46 . 
     In plan view, the end portion of the medium M is disposed on a part in which the eaves portion  28  and the medium supporting portion  32  overlap with each other (gap between eaves portion  28  and medium supporting portion  32 ). 
     The medium M has various sizes, and the medium M includes various widths (length of width direction X). In a case in which the mediums M having different sizes are set, a position of the first medium pressing member  19 A is fixed, a position of the second medium pressing member  19 B is moved in the width direction X, and an interval between the first medium pressing member  19 A and the second medium pressing member  19 B is adjusted. 
     As illustrated in  FIGS. 2 and 3 , the base portion  20  of the medium pressing member  19  is disposed so as to be in contact with the supporting surface  32   a  of the medium supporting portion  32 , and is attached to (is fixed to) the medium supporting portion  32  by the attaching portion  23 . 
     The attaching portion  23  includes a first attaching portion  24  which is disposed on a upstream side of the printing region E in the transporting direction Y, and a second attaching portion  25  and the third attaching portion  26  which are disposed on the downstream side of the printing region E in the transporting direction Y. That is, the base portion  20  includes the first attaching portion  24 , the second attaching portion  25 , and the third attaching portion  26  which are sequentially disposed along the transporting direction Y. In other words, the medium pressing member  19  includes at least two attaching portions  23  which attach the base portion  20  to the medium supporting portion  32 . 
     Also, the attaching portion  23  may be configured to be disposed on both the upstream side of the printing region E in the transporting direction Y and the downstream side of the printing region E in the transporting direction Y with respect to, for example, may be configured not to have the third attaching portion  26 , for example, may be configured not to have the second attaching portion  25 , or may be configured so that an attaching portion other than the attaching portions  24 ,  25 , and  26  are attached. 
     The first attaching portion  24  is formed by bending the end portions of the upstream side of the base portion  20  in the transporting direction Y. The first attaching portion  24  is attached so as to grab the end portions of the upstream side (wall surface of medium supporting portion  32 ) of the medium supporting portion  32  in the transporting direction Y, and protrudes from the end portion of the medium supporting portion  32  in a plan view. 
     The base portion  20  is constituted of a material having elasticity. The first attaching portion  24  is a type of a spring member which is elastically deformed. When the first attaching portion  24  grabs the end portions of the upstream side of the medium supporting portion  32  in the transporting direction Y in a state of being elastically deformed, an upstream side of the base portion  20  with respect to the printing region E is fixed to the medium supporting portion  32 . 
     The second attaching portion  25  is formed by cutting a part of the base portion  20  and bending the cut part. Further, an opening  25 A is formed with the second attaching portion  25  by cutting the part of the base portion  20 . As a result, the opening  25 A and the second attaching portion  25  are formed on the downstream side of the printing region E in the transporting direction. 
     The second attaching portion  25  is a type of a spring member which is elastically deformed, and is fitted into an intermediate of the groove portion  46  of the medium supporting portion  32 . When the second attaching portion  25  grabs a wall surface of the medium supporting portion  32  in the groove portion  46  in a state of being elastically deformed, a downstream side of the base portion  20  with respect to the printing region E is fixed to the medium supporting portion  32 . 
     Since the medium pressing member  19  moves in the width direction X in a state in which the second attaching portion  25  is fitted into an intermediate of the groove portion  46 , the second attaching portion  25  has a function of guiding movement of the medium pressing member  19  in the width direction X. 
     The third attaching portions  26  are formed by bending both end portions on the downstream side of the base portion  20  in the transporting direction Y. The third attaching portions  26  are respectively attached so as to grab both the end portions of the downstream side of the medium supporting portion  32  (wall surface of medium supporting portion  32 ) in the transporting direction Y, and protrudes from the end portions of the medium supporting portion  32  in a plan view. 
     The third attaching portion  26  is a type of a spring member which is elastically deformed. When the third attaching portion  26  grabs both the end portions of the downstream side of the medium supporting portion  32  in the transporting direction Y in a state of being elastically deformed, a downstream side of the base portion  20  with respect to the printing region E is fixed to the medium supporting portion  32 . 
     In addition, after a position of the medium pressing member  19  with respect to the medium supporting portion  32  is adjusted so that the second attaching portion  25  is disposed on the intermediate of the groove portion  46 , when the medium pressing member  19  is pushed into the medium supporting portion  32 , the attaching portions  24 ,  25 , and  26  are elastically deformed, the wall surface of the medium supporting portion  32  is grabbed, and the medium pressing member  19  can be attached (fixed) to the medium supporting portion  32 . 
     As illustrated in  FIG. 4 , a gap is formed between the eaves portion  28  of the medium pressing member  19  and the medium supporting portion  32 . An end portion of the medium M is disposed on a gap between the eaves portion  28  and the medium supporting portion  32 . Further, an inclined portion  29  separated from the medium supporting portion  32  toward the upstream side in the transporting direction Y is formed on an upstream side end in the transporting direction Y in the eaves portion  28 . 
     The medium M is unwound from the roll of paper RS in a state of being wound around the supplying reel  14   a , and is transported in the transporting direction Y by the transporting portion  13 . The medium M is easily warped (easily floats) in a direction of being separated from the medium supporting portion  32  by a winding curl of the roll of paper RS which is wound in a roll state. Even in a case in which the medium M is warped by the winding curl, since a distal end of the medium M is guided to the gap between the medium supporting portion  32  and the eaves portion  28  by the inclined portion  29 , the medium M stably passes through the gap between the medium supporting portion  32  and the eaves portion  28 . 
     If the medium M floats from the medium supporting portion  32  and passes over the medium pressing member  19 , there is a concern of a defect of interfering the medium M with the head  15  or a defect such as jam of the medium M. The inclined portion  29  suppresses such a defect. 
     The eaves portion  28  presses the end portion of the medium M between the medium supporting portion  32  and the eaves portion in a case in which the medium M floats from the medium supporting portion  32  by the winding curl, and suppresses floating of the medium M from the medium supporting portion  32 . As a result, a defect, of which the medium M floats from the medium supporting portion  32  by the winding curl, is close to the head  15 , and is interfered with the head  15 , and the head  15  malfunctions, is suppressed. Further, the defect such as jam of the medium M can be also suppressed. 
     In order to increase a printing speed of the printing apparatus  11 , it is necessary to increase the head  15  in size and to lengthen a dimension of the transporting direction Y of the head  15 . Therefore, a length of the transporting direction Y of the medium pressing member  19  needs to be longer. Further, since the printing apparatus  11  deals with relatively large media (medium), compared to a case of dealing with small media (medium), the medium pressing member becomes greater and the length of the transporting direction Y of the medium pressing member  19  becomes longer. 
     However, when the medium pressing member  19  is lengthened, the medium pressing member  19  is easily deformed due to small force, compared to a case in which the medium pressing member  19  is short. Further, since the medium pressing member  19  is a thin elongated member, the medium pressing member  19  is easily deformed due to small force, compared to a case in which the medium pressing member  19  is a thick elongated member. 
     For example, in order to make the medium pressing member  19  be difficult to be deformed, it is considered that the medium pressing member  19  is thickened. However, if the medium pressing member  19  becomes thickened, the interval between the medium supporting portion  32  and the head  15  is lengthened, a flight distance of ink being discharged from the head  15  to the medium M is lengthened, the ink being discharged from the head  15  is difficult to be landed on a target position of the medium M, and a quality of the image being printed on the medium M may be deteriorated. 
     Therefore, in order to suppress deterioration of the quality of the image being printed on the medium M, the interval between the medium supporting portion  32  and the head  15  is preferably short, the medium pressing member  19  is preferably thin, and the medium pressing member  19  is easily deformed due to small force. 
     Meanwhile, if a force from the medium supporting portion  32  toward the head  15  acts on the medium pressing member  19  from the medium M by the winding curl of the roll of paper RS, the medium pressing member  19  is easily deformed from the medium supporting portion  32  toward the head  15 . If the medium pressing member  19  is deformed toward the head  15 , is close to the head  15 , and is interfered with the head  15 , there is a concern that the head  15  may malfunction. 
     Further, if the medium pressing member  19  is deformed from the medium supporting portion  32  toward the head  15 , the medium M is also deformed from the medium supporting portion  32  toward the head  15 , an interval between the head  15  and the medium M becomes not uniformed, there is a concern that the defect of deteriorating a quality of the image being printed on the medium M may generated. Further, there is a concern that the defect such as jam of the medium M may be generated. 
     As seen from the above, since, in the printing apparatus  11  dealing with relatively large media (medium), the length of the medium pressing member  19  becomes longer and is easily deformed, compared to a case of dealing with small media (medium), various defects are easily generated such as a defect such as malfunction of the head  15 , a defect such as deterioration of the quality of the image being printed on the medium M, or the defect such as jam of the medium M. 
     In the embodiment, even in a case in which the medium pressing member  19  becomes greater and the medium pressing member  19  is lengthened, an excellent configuration is provided in which the medium pressing member  19  is difficult to be deformed, the defects described above are not difficult to be generated, and long term reliability or a printing quality of the printing apparatus  11  dealing with relatively large media (medium) can be increased. 
     Hereinafter, details will be described. 
       FIG. 5  is a schematic sectional view of the medium pressing member taken along V-V line of  FIG. 2 .  FIG. 6  is a view corresponding to  FIG. 3 , and is a schematic sectional view illustrating a state of the base portion of the medium pressing member according to the embodiment.  FIGS. 7A and 7B  are views corresponding to  FIG. 6 , and are schematic sectional views illustrating the state of the base portion of the medium pressing member according to a comparison example. 
     In addition,  FIG. 7A  illustrates a state of a base portion  80  of a medium pressing member  79  according to a comparison example in a case in which heating is not performed by the platen heater  42 .  FIG. 7B  illustrates a state of the base portion  80  of the medium pressing member  79  according to the comparison example in a case in which heating is performed by the platen heater  42 . 
     As illustrated in  FIG. 5 , the medium pressing member  19  includes the first material  21  and the second material  22  which are sequentially stacked on the medium supporting portion  32 . 
     The first material  21  is attached to the supporting surface  32   a  of the medium supporting portion  32 , and forms a first surface  21   a  in contact with the medium supporting portion  32 . The first material  21  is constituted of stainless steel for spring (SUS 304). A coefficient of thermal expansion of the first material  21  is approximately 17.3×10 −6 ° C. −1 . The first material  21  is formed by performing a bending process on a base material constituted of the SUS 304. 
     The second material  22  is disposed on an opposite side of the medium supporting portion  32  of the first material  21 , and forms a second surface  22   a  on an opposite side of the first surface  21   a . The second material  22  is constituted of stainless steel for spring (SUS 301). A coefficient of thermal expansion of the second material  22  is approximately 16.9×10 −6 ° C. −1 . The second material  22  is formed by performing the bending process on a base material constituted of the SUS 301. 
     Further, the second material  22  is bonded to the first material  21  through an adhesive (not illustrated). Also, the second material  22  may be directly bonded to the first material  21  by a method such as friction welding. 
     The first material  21  and the second material  22  are a so-called spring plate, and have elasticity. The first material  21  and the second material  22  are constituted of a metal having excellence corrosion resistance, and are difficult to be deteriorated by a chemical solution (for example, ink) or heat, and thus reliability of the medium pressing member  19  can be increased. 
     In the width direction X, the second material  22  protrudes from the first material  21 . A part of the second material  22  protruding from the first material  21  becomes the eaves portion  28  which forms a gap with the medium supporting portion  32 . The end portion of the medium M is disposed on a gap between the part (eaves portion  28 ) of the second material  22  protruding from the first material  21  and the medium supporting portion  32 . 
     As described above, the eaves portion  28  of the medium pressing member  19  is constituted of the second material  22 , forms the gap with the medium supporting portion  32 , and suppresses floating of the medium M from the medium supporting portion  32 . 
     Meanwhile, a part on which the first material  21  and the second material  22  are stacked becomes the base portion  20  of the medium pressing member  19 . That is, in the base portion  20  being attached to the medium supporting portion  32 , the first material  21  constituting the first surface  21   a  being attached to the medium supporting portion  32  and the second material  22  constituting the second surface  22   a  on an opposite side of the first surface  21   a  are sequentially stacked, and the coefficient of thermal expansion of the first material  21  becomes higher than the coefficient of thermal expansion of the second material  22 . 
     As seen from the above, the base portion  20  of the medium pressing member  19  includes a configuration in which the first material  21  having a high coefficient of thermal expansion and the second material  22  having a low coefficient of thermal expansion are sequentially stacked on the medium supporting portion  32 . 
     As illustrated in  FIG. 7A , the base portion  80  of the medium pressing member  79  according to the comparison example has a same point as that of Embodiment 1, in terms of the fact that the first material  21  having the high coefficient of thermal expansion and the second material  22  having the low coefficient of thermal expansion are sequentially stacked on the medium supporting portion  32 . Meanwhile, the comparison example has a different point from Embodiment 1 in terms of the fact that the base portion  80  of the medium pressing member  79  does not include the attaching portion and is not fixed to the medium supporting portion  32 . 
     Further, the comparison example has the same point as Embodiment 1 in terms of the fact that the base portion  80  of the medium pressing member  79  is disposed along the transporting direction Y without acting extra force in a case of not being heated by the platen heater  42  (in a case of being positioned at room temperature). 
     As illustrated in  FIG. 7B , when the medium pressing member  79  is heated by the platen heater  42 , the coefficient of thermal expansion of the first material  21  becomes higher than the coefficient of thermal expansion of the second material  22 , and thus the first material  21  thermally expands more than the second material  22 . Then, the base portion  80  of the medium pressing member  79  is not fixed to the medium supporting portion  32 , and thus is curved (deformed) so as to be separated from the medium supporting portion  32 , from the center portion CA toward the end portion TA. In other words, when the medium pressing member  79  is heated by the platen heater  42 , a force FA (force illustrated by arrow in drawing) deforming the end portion TA in a direction of being separated from the medium supporting portion  32  acts on the base portion  80  of the medium pressing member  79 , and thus the end portion TA of the base portion  80  of the medium pressing member  79  is deformed in a direction of being separated from the medium supporting portion  32 . 
     In the following description, the force FA deforming the end portion TA in the direction of being separated from the medium supporting portion  32  is referred to as a deformation force FA. 
     Meanwhile, it is not illustrated, but in a case in which the coefficient of thermal expansion of the first material  21  is lower than the coefficient of thermal expansion of the second material  22 , when the medium pressing member  79  is heated, the base portion  80  of the medium pressing member  79  is deformed in a shape opposite to that of in  FIG. 7B . In detail, a force, which increases from the end portion TA toward the center portion CA, deforming the end portion TA in the direction of being separated from the medium supporting portion  32  acts on the base portion  80  of the medium pressing member  79 , and thus the center portion CA of the base portion  80  of the medium pressing member  79  is deformed in a direction of being separated from the medium supporting portion  32 . 
     As illustrated in  FIG. 6 , the base portion  20  of the medium pressing member  19  according to the embodiment is disposed along the transporting direction Y without acting extra force in a case of not being heated by the platen heater  42  (in a case of being positioned at room temperature). 
     When the medium pressing member  19  is heated by the platen heater  42 , since the coefficient of thermal expansion of the first material  21  is higher than the coefficient of thermal expansion of the second material  22 , the first material  21  thermally expands more than the second material  22 , and the deformation force FA (refer to  FIG. 7B ) described above acts on the base portion  20  of the medium pressing member  19 . That is, the deformation force FA, which increases from the center portion C toward the end portion T, deforming in the direction of being separated from the medium supporting portion  32  acts on the base portion  20  of the medium pressing member  19 . 
     However, since the end portion T of the base portion  20  of the medium pressing member  19  is fixed to the medium supporting portion  32  by the attaching portion  23 , even when the deformation force FA acts on the base portion  20  of the medium pressing member  19 , deformation of the base portion  20  of the medium pressing member  19  is suppressed. That is, as illustrated in  FIG. 6 , a force F (hereinafter, refer to drag force F) against the deformation force FA acts on the base portion  20  of the medium pressing member  19 , and deformation of the base portion  20  of the medium pressing member  19  is suppressed. 
     The drag force F is a force pressing the medium pressing member  19  against the medium supporting portion  32  and suppresses deformation of the medium pressing member  19 . Therefore, when the medium pressing member  19  is heated by the platen heater  42 , the base portion  20  of the medium pressing member  19  becomes in a state of being pressed by the drag force F against the medium supporting portion  32 , and is difficult to be deformed. 
     Meanwhile, it is not illustrated, but in a case in which the coefficient of thermal expansion of the first material  21  is lower than the coefficient of thermal expansion of the second material  22 , if the medium pressing member  19  is heated, the force, which increases the end portion T toward the center portion C, deforming in the direction of being separated from the medium supporting portion  32  acts on the base portion  20  of the medium pressing member  19 . In this case, the center portion C of the base portion  20  of the medium pressing member  19  is not fixed to the medium supporting portion  32 , and thus is deformed in the direction of being separated from the medium supporting portion  32 . Further, when the center portion C of the base portion  20  of the medium pressing member  19  is deformed in the direction of being separated from the medium supporting portion  32 , and is close to the head  15 , there is a concern that the head  15  may be interfered and the head  15  may malfunction. 
     As seen from the above, when the medium pressing member  19  is heated by the platen heater  42 , in a configuration in which the coefficient of thermal expansion of the first material  21  is lower than the coefficient of thermal expansion of the second material  22 , the medium pressing member  19  is deformed, but in a configuration in which the coefficient of thermal expansion of the first material  21  is higher than the coefficient of thermal expansion of the second material  22 , the medium pressing member  19  is difficult to be deformed. Therefore, in order to make the medium pressing member  19  be difficult to be deformed, it is preferable that the coefficient of thermal expansion of the first material  21  be higher than the coefficient of thermal expansion of the second material  22 . 
     As described above, when the coefficient of thermal expansion of the first material  21  is higher than the coefficient of thermal expansion of the second material  22 , and the medium pressing member  19  is heated by the platen heater  42 , the medium pressing member  19  becomes in a state of being pressed against the medium supporting portion  32  due to the drag force F, and the medium pressing member  19  is difficult to be deformed. Therefore, even when the medium pressing member  19  is increased in size and the medium pressing member  19  is lengthened, the medium pressing member  19  according to the embodiment is difficult to be deformed, and thereby making it possible to increase long term reliability or a printing quality of the printing apparatus  11 . 
     Embodiment 2 
       FIG. 8  is a view corresponding to  FIG. 5 , and is a schematic sectional view of the medium pressing member mounted in the printing apparatus according to Embodiment 2. 
     A medium pressing member  190  according to the embodiment is different from the medium pressing member  19  according to Embodiment 1 in terms of the shapes thereof, and the different point is a main difference between Embodiment 1 and Embodiment 2. 
     Hereinafter, refer to  FIG. 8 , the medium pressing member  190  mounted in the printing apparatus according to the embodiment will be described based on a difference from Embodiment 1. In addition, the same numeral is given to the same configuration part as that of Embodiment 1, and overlapping description will be omitted. 
     As described above  FIG. 8 , in the printing apparatus according to the embodiment, the medium pressing member  190  is attached to the supporting surface  32   a  of the medium supporting portion  32 , and a first material  210  and a second material  220  are sequentially stacked on the medium supporting portion  32 . 
     The first material  210  is constituted of the same material (SUS 304) as the first material  21  of Embodiment 1, and has elasticity. A coefficient of thermal expansion of the first material  210  is approximately 17.3×10 −6 ° C. −1 . The second material  220  is constituted of the same material (SUS 301) as the second material  22  of Embodiment 1, and has elasticity. The coefficient of thermal expansion of the second material  220  is approximately 16.9×10 −6 ° C. −1 . 
     The coefficient of thermal expansion of the first material  210  is higher than the coefficient of thermal expansion of the second material  220 . 
     The first material  210  is formed by performing a bending process on a base material constituted of the SUS 304, and includes a recessed portion  51  in which the center portion is recessed compared to the end portion. That is, the first material  210  includes the recessed portion  51  and a part protruding from the recessed portion  51  in the width direction X. The second material  220  is fitted into the recessed portion  51 . 
     The part protruding from the recessed portion  51  of the first material  210  in the width direction X becomes the eaves portion  28  and forms the gap with the medium supporting portion  32 . Therefore, the eaves portion  28  of the embodiment is constituted of the first material  210 , the eaves portion  28  of Embodiment 1 is constituted of the second material  22 , and this point is a difference between the embodiment and Embodiment 1. 
     A part in which the first material  210  and the second material  220  are stacked on the medium supporting portion  32  becomes the base portion  20 . The base portion  20  of the embodiment has a configuration in which the first material  210  having the high coefficient of thermal expansion and the second material  220  having the low coefficient of thermal expansion are sequentially stacked on the medium supporting portion  32 , and this point is the same as Embodiment 1. 
     Even with the above configuration, since the base portion  20  of the medium pressing member  190  according to the embodiment is the same as Embodiment 1, the same effect as that of Embodiment 1 can be obtained in which, when the medium pressing member  190  is heated by the platen heater  42 , the base portion  20  of the medium pressing member  190  becomes in a state of being pressed against the medium supporting portion  32  by the drag force F, and thus the medium pressing member  190  is difficult to be deformed. 
     The invention is not limited to the above-described embodiments, can be appropriately modified within a range not contrary to the gist or idea of the invention which can be read from claims and the entire specification, and various modification examples are conceivable besides the embodiments described above. 
     Modification Example 1 
     A medium pressing member  19 Z (not illustrated) according to Modification Example 1 is different from the medium pressing member  19  according to Embodiment 1 in terms of a material constituting the first material  21 . 
     Hereinafter, the same numeral is given to the same configuration part as that of Embodiment 1, and this modification example will be described based on a difference from Embodiment 1. 
     The first material  21  of the medium pressing member  19 Z according to the modification example is constituted of a resin (for example, polyacetal resin (POM resin)). The first material  21  is formed by performing a molding process on the POM resin, and the coefficient of thermal expansion of the first material  21  is approximately 100×10 −6 ° C. −1 . 
     The second material  22  is constituted of stainless steel for spring (SUS 301). The coefficient of thermal expansion of the second material  22  is approximately 16.9×10 −6 ° C. −1 . 
     As seen from the above, in the modification example, the first material  21  is constituted of a resin, and the second material  22  is constituted of a metal. Meanwhile, in Embodiment 1, both of the first material  21  and the second material  22  are constituted of a metal. This point is a difference between the modification example and Embodiment 1. 
     Since the base portion  20  of the medium pressing member  19 Z according to the modification example is the same as Embodiment 1, the same effect as that of Embodiment 1 can be obtained in which, when the first material  21  having the high coefficient of thermal expansion and the second material  22  having the low coefficient of thermal expansion are sequentially stacked on the medium supporting portion  32 , and the medium pressing member  19 Z is heated by the platen heater  42 , the base portion  20  of the medium pressing member  19 Z becomes in a state of being pressed against the medium supporting portion  32  by the drag force F, and thus the medium pressing member  19  Z is difficult to be deformed. 
     Further, when the first material  21  is formed by performing the molding process on the resin (POM resin), the first material can be processed so as to have more complicated shape than a case in which the first material  21  is formed by performing the bending process on a metal (Embodiment 1). As a result, regarding a part to which the first material  21  is difficult to be attached in Embodiment 1, the first material  21  of the modification example can be attached thereto. That is, in the modification example, compared to Embodiment 1, a degree of freedom of the part to which the first material  21  is attached can be increased. 
     Further, since the medium pressing member  19 Z according to the modification example is constituted of a resin (POM resin) and a metal (stainless steel for spring), costs can be reduced compared to a case in which the entire medium pressing member is constituted of a metal (stainless steel for spring) (Embodiment 1). 
     Further, the modification example may be applied to the medium pressing member  190  according to Embodiment 2. 
     Modification Example 2 
       FIG. 9  is a view corresponding to  FIG. 3 , and is a schematic sectional view illustrating a state of the base portion of the medium pressing member according to Modification Example 2. In order to easily understand a state of Modification Example 2, in  FIG. 9 , the attaching portion  23  is omitted, and the medium supporting portion  32  is illustrated in a rectangular shape by a two-dotted chain. Further, in  FIG. 9 , the medium pressing member  19 Y which is not fixed to the medium supporting portion  32  is illustrated by a broken line, and the medium pressing member  19 Y which is fixed to the medium supporting portion  32  by the attaching portion  23  (not illustrated) is illustrated by a solid line. 
     In the medium pressing member  19 Y according to the modification example, a shape of the base portion  20  which is not heated by the platen heater  42  is different from that of the medium pressing member  19  according to Embodiment 1. 
     Hereinafter, the same numeral is given to the same configuration part as that of Embodiment 1, and the modification example will be described based on a difference from Embodiment 1. 
     As illustrated in  FIG. 9 , in the base portion  20  of the medium pressing member  19 Y according to the modification example, the first material  21  having the high coefficient of thermal expansion and the second material  22  having the low coefficient of thermal expansion are sequentially stacked on the medium supporting portion  32 , and this point is the same as Embodiment 1. 
     As illustrated in  FIG. 9  with a broken line, from the center portion C toward the end portion T, at least one of the first material  21  and the second material  22  according to the modification example is processed so as to have a warp which is curved so as to be separated from the medium supporting portion  32 . Therefore, in a case in which the base portion  20  of the medium pressing member  19 Y according to the modification example is not heated by the platen heater  42  and is not fixed to the medium supporting portion  32 , from the center portion C toward the end portion T, the base portion includes the warp which is curved so as to be separated from the medium supporting portion  32 . Meanwhile, in a case in which the base portion  20  of the medium pressing member  19  according to Embodiment 1 is not heated by the platen heater  42  and is not being fixed to the medium supporting portion  32 , the based portion is disposed along the transporting direction Y, and does not have the curved warp. 
     Hereinafter, the medium pressing member  19 Y (medium pressing member  19 Y illustrated by broken like of  FIG. 9 ) which is not fixed to the medium supporting portion  32  is referred to as the medium pressing member  19 Y before being attached. 
     As illustrated by a solid line of  FIG. 9 , in a case in which the base portion  20  of the medium pressing member  19 Y according to the modification example is not heated by the platen heater  42  and is fixed to the medium supporting portion  32 , from the center portion C toward the end portion T, the warp which is curved so as to be separated from the medium supporting portion  32  in a direction is corrected, and is disposed along the transporting direction Y. That is, a force FB illustrated by an arrow in the drawing acts on the medium pressing member  19 Y before being attached, and the medium pressing member  19 Y is fixed to the medium supporting portion  32  in a state in which, from the center portion C toward the end portion T, the warp curved so as to be separated from the medium supporting portion  32  is corrected. 
     Therefore, in a case in which the medium pressing member  19 Y is not heated by the platen heater  42 , the force FB acts on the medium pressing member  19 Y. The force FB is a force correcting the curved warp, and is a force pressing the medium pressing member  19 Y against the medium supporting portion  32 . Therefore, even in a case in which heating is not performed by the platen heater  42 , since the medium pressing member  19 Y becomes in a state of being pressed against the medium supporting portion  32  by the force FB, the member is difficult to be deformed. 
     Further, if the medium pressing member  19 Y is heated by the platen heater  42 , the drag force F (refer to  FIG. 6 ) acts with the force FB, and compared to a case in which only the drag force F acts (Embodiment 1), the force pressing the medium pressing member  19 Y against the medium supporting portion  32  becomes stronger, and thus the medium pressing member  19 Y is more difficult to be deformed. 
     Therefore, even in a case in which the medium pressing member is increased in size and the medium pressing member is lengthened, the medium pressing member  19 Y according to the modification example is more difficult to be deformed, and thus long term reliability or a printing quality of the printing apparatus  11  can be further increased, compared to the medium pressing member  19  according to Embodiment 1. 
     Also, in the medium pressing member  19 Y, a configuration component being processed to have warp which is curved so as to be separated from the medium supporting portion  32 , from the center portion C toward the end portion T, may be constituted of only the first material  21 , may be constituted of only the second material  22 , or may be constituted of both the first material  21  and the second material  22 . 
     As seen from the above, in the modification example, at least one of the first material  21  and the second material  22  has elasticity, and in a case in which the base portion  20  is mounted in the medium supporting portion  32 , from the center portion C toward the end portion T, the warp which is curved so as to be separated from the medium supporting portion  32  is included, or in a case in which the base portion  20  is attached to the medium supporting portion  32 , the base portion is disposed along the medium supporting portion  32  in a state in which the warp is corrected. With such a configuration, the medium pressing member  19 Y is more difficult to be deformed, and thus long term reliability or a printing quality of the printing apparatus  11  can be further increased. 
     Further, the modification example may be applied to the medium pressing member  190  according to Embodiment 2. 
     Modification Example 3 
     A medium pressing member  19 X (not illustrated) according to Modification Example 3 is different from the medium pressing member  19  according to Embodiment 1 in terms of the fact that the second material  22  is constituted of a different material. Hereinafter, the same numeral is given to the same configuration part as that of Embodiment 1, and this modification example will be described based on a difference from Embodiment 1. 
     In the medium pressing member  19 X according to Modification Example 3, the first material  21  is constituted of stainless steel for spring (SUS 304), and the second material  22  is constituted of a shape memory alloy (Ni—Ti alloy). Meanwhile, in the medium pressing member  19  according to Embodiment 1, the first material  21  is constituted of stainless steel for spring (SUS 304), and the second material  22  is constituted of stainless steel for spring (SUS 301). That is, the modification example and Embodiment 1 are different from each other in terms of the fact that a configuration material of the second material  22  is different. 
     The coefficient of thermal expansion of the first material  21  is approximately 17.3×10 −6 ° C. −1 , and the coefficient of thermal expansion of the second material  22  is approximately 10×10 −6 ° C. −1 . Accordingly, the coefficient of thermal expansion of the first material  21  is higher than the coefficient of thermal expansion of the second material  22 . 
     Further, the shape memory alloy constituting the second material  22  memorizes a shape of the warp which is curved so as to be separated from the medium supporting portion  32  in a direction from the center portion C toward the end portion T in a case in which heating is performed by the platen heater  42 . That is, the shape memory alloy constituting the second material  22  memorizes a shape (shape of the medium pressing member  19 Y before being attached in Modification Example 2) illustrated by a broken line of  FIG. 9 , in a case in which heating is performed by the platen heater  42 . 
     Then, when the medium pressing member  19 X is heated by the platen heater  42 , a force changing a shape into the memorized shape (a shape of the warp which is curved so as to be separated from the medium supporting portion  32 , from the center portion C toward the end portion T) acts on the second material  22 . The force which tends to change to this memorized shape is a force acting in the same direction as the deformation force FA (refer to  FIG. 7B ). 
     However, the end portion T of the base portion  20  of the medium pressing member  19 X is fixed to the medium supporting portion  32  by the attaching portion  23 , even when the force which tends to change to the memorized shape acts on the base portion  20  of the medium pressing member  19 X, deformation of the base portion  20  of the medium pressing member  19 X is suppressed. That is, even when the force which tends to change to the memorized shape acts on the base portion  20  of the medium pressing member  19 X, a force against the force which tends to be changed acts on the base portion  20  of the medium pressing member  19 X, and thus deformation of the base portion  20  of the medium pressing member  19 X is suppressed. 
     The force against the force which tends to change to the memorized shape is a force acting in the same direction as the drag force F (refer to  FIG. 6 ), and is a force pressing the medium pressing member  19 X against the medium supporting portion  32 . 
     Therefore, when the medium pressing member  19 X is heated by the platen heater  42 , the force (force pressing the medium pressing member  19 X against the medium supporting portion  32 ) against the force which tends to change to the memorized shape acts on the medium pressing member  19 X with the drag force F. Therefore, compared to a case in which only the drag force F acts (Embodiment 1), the force pressing the medium pressing member  19 X against the medium supporting portion  32  becomes stronger, and the medium pressing member  19 X is more difficult to be deformed. 
     Therefore, even in a case in which the medium pressing member is increased in size and the medium pressing member is lengthened, the medium pressing member  19 X according to the modification example is more difficult to be deformed than the medium pressing member  19  according to Embodiment 1, and thus long term reliability or a printing quality of the printing apparatus  11  can be further increased. 
     As seen from the above, in a case in which the second material  22  is heated by the platen heater  42 , the modification example is constituted of a shape memory alloy (For example, Ni—Ti alloy) in which a shape of the warp which is curved so as to be separated from the medium supporting portion  32  in a direction from the center portion C toward the end portion T is memorizes. Further, in a case in which the base portion  20  is attached to the medium supporting portion  32 , the base portion is disposed along the medium supporting portion  32  in a state in which the shape of the warp is corrected. 
     With such a configuration, the medium pressing member  19 X is more difficult to be deformed, and long term reliability or a printing quality of the printing apparatus  11  can be further increased. 
     Also, the first material  21  is set to a shape memory alloy (For example, Ni—Ti alloy), and the second material  22  may be constituted of a material having a low coefficient of thermal expansion than the first material  21 . 
     Further, the modification example may be applied to the medium pressing member  190  according to Embodiment 2. 
     Modification Example 4 
     In a medium pressing member  19 W (not illustrated) according to Modification Example 4, the center portion C of the base portion  20  is fixed to the medium supporting portion  32  and is difficult to be deformed in the direction of being separated from the medium supporting portion  32 . Further, in the medium pressing member  19 W according to the modification example, the coefficient of thermal expansion of the first material  21  is lower than the coefficient of thermal expansion of the second material  22 . 
     This point is a difference between the modification example and Embodiment 1, and hereinafter, the same numeral is given to the same configuration part as that of Embodiment 1, and this modification example will be described based on a difference from Embodiment 1. 
     In the medium pressing member  19 W according to the modification example, the coefficient of thermal expansion of the first material  21  is lower than the coefficient of thermal expansion of the second material  22 , and thus when the medium pressing member  19 W is heated by the platen heater  42 , a force, which increases from the end portion T toward the center portion C, tend to change in the direction of being separated from the medium supporting portion  32  acts on the base portion  20  of the medium pressing member  19 W. The center portion C of the base portion  20  of the medium pressing member  19 W is fixed to the medium supporting portion  32 , and deformation in a direction of being separated from the medium supporting portion  32  is suppressed. That is, when the medium pressing member  19 W is heated by the platen heater  42 , the force pressing the medium pressing member  19 W against the medium supporting portion  32  acts on the medium pressing member  19 W, and deformation of the center portion C of the medium pressing member  19 W is suppressed. 
     Therefore, in a case in which the center portion C of the base portion  20  is fixed to the medium supporting portion  32 , even when the coefficient of thermal expansion of the first material  21  is lower than the coefficient of thermal expansion of the second material  22 , if the medium pressing member  19 W is heated by the platen heater  42 , the force pressing the medium pressing member  19 W against the medium supporting portion  32  acts on the medium pressing member  19 W, and the medium pressing member  19 W becomes difficult to be deformed. 
     As seen from the above, in a case in which the center portion C of the base portion  20  is fixed to the medium supporting portion  32 , the coefficient of thermal expansion of the first material  21  may be lower than the coefficient of thermal expansion of the second material  22 . 
     Modification Example 5 
     The printing apparatus including the medium pressing member according to the embodiments or modification examples described above may be a liquid ejecting device which performs recording by ejecting or discharging liquid (including liquid, a liquid body in which particles of a functional material are dispersed or mixed in liquid, a fluid type body such as gel, and solid which is able to flow and be discharged as liquid) other than the ink. For example, the printing apparatus may be a liquid ejecting device which performs recording by ejecting a liquid type member including a material such as an electrode material or a coloring material (pixel material) being used in a manufacture of a liquid crystal display, an electroluminescence (EL) display, a surface emitting display, and the like in a dispersed or dissolved form. In addition, the printing apparatus may be a fluid ejecting device which ejects a fluid type member such as gel (for example, physical gel) or the like. Also, the invention can be applied to any one of the liquid ejecting devices among these devices. 
     This application claims priority under 35 U.S.C. § 119 to Japanese Patent Application No. 2016-248821, filed Dec. 22, 2016. The entire disclosure of Japanese Patent Application No. 2016-248821 is hereby incorporated herein by reference.