Patent Publication Number: US-7896461-B2

Title: Fluid discharge device, and a printer and media processing device that use the fluid discharge device

Description:
BACKGROUND OF THE INVENTION 
     1. Field of Invention 
     The present invention relates to a fluid discharge device that discharges fluid from the nozzles of a discharge head, and to a printer and a media processing device that use the fluid discharge device. 
     2. Description of Related Art 
     Printers such as inkjet printers typically print by the print head discharging ink droplets from a plurality of nozzles. 
     Such printers may also have a pumping device that seals the nozzle surface of the print head with a cap and vacuums ink from the nozzles in order to unclog clogged nozzles in the print head, or a capping device that seals the nozzle surface of the print head with a cap when not printing (when in the standby mode) in order to prevent the nozzles of the print head from becoming clogged. See, for example, Japanese Unexamined Patent Appl. Pub. JP-A-2006-264243. 
     The surface tension of the ink that is absorbed by a sponge or other absorbent material disposed inside the cap may, however, cause the ink to travel over the inside surface of the cap to an area that comes in contact with the nozzle surface. If the ink I transferred from the absorbent material  95  inside the head cap  82  travels to an area in contact with the nozzle surface  61   a  as shown in  FIG. 12A , a film of ink I is formed between the lip  92  of the cap and the nozzle surface  61   a  the moment the head cap  82  separates from the nozzle surface  61   a  as shown in  FIG. 12B . When this film then breaks, the ink I is scattered and ink droplets cling to the nozzle surface  61   a  as shown in  FIG. 12C . More particularly, because the space inside the head cap  82  is in a vacuum state when the head cap  82  separates from the nozzle surface  61   a,  the film of ink I explodes into the head cap  82 , and the ink I spray easily clings to the ink nozzles of the nozzle surface  61   a . When ink I thus clings to an ink nozzle, it breaks the ink meniscus inside the ink nozzle and causes ink discharge problems. 
     SUMMARY OF THE INVENTION 
     A first aspect of the invention is a fluid discharge device that can suppress discharge defects caused by the adhesion of fluid spray and maintain a good fluid discharge state. A printer and a media processing device according to the present invention have this fluid discharge device. 
     A fluid discharge device according to a first aspect of the invention has a discharge head that has a discharge nozzle for discharging fluid, and a head cap that has an opening that can seal a nozzle surface to which the discharge nozzle of the discharge head is disposed and can contact the nozzle surface so that the discharge nozzle is covered. The fluid discharge device is rendered so that the head cap can move to and away from the nozzle surface. The head cap has a lip part that has a contact portion that contacts the nozzle surface, and the inside circumference surface of the lip part is formed with a centerline average surface roughness Ra of 3.2 or less. 
     Because the centerline average surface roughness Ra of the inside surface of the head cap is less than or equal to access door 3.2, it is difficult for fluid on the head cap to migrate over the inside surface of the head cap. As a result, when the head cap is placed tightly to the nozzle surface of the discharge head, fluid can be substantially prevented from migrating along the lip part and contacting the portion in contact with the nozzle surface. 
     Preferably, the contact portion and outside circumference surface of the lip part are formed with a centerline average surface roughness Ra of 3.2 or less. By thus rendering the contact portion and the outside surface of the lip part as smooth surfaces, accumulation of fluid at the smooth part is suppressed, fluid at the contact portion moves easily down, and adhesion of fluid to the contact portion can be completely or substantially eliminated. This aspect of the invention is further preferable because even if fluid sticks to the outside surface, it is difficult for the fluid to migrate to the contact portion. 
     In a fluid discharge device according to another aspect of the invention, a coarse part with coarser surface roughness than the surface roughness of the contact portion is formed to the lip part at a part of the outside circumference surface separated from the contact portion. Even if some fluid is left in the contact area between the lip part of the head cap and the nozzle surface, the induction of fluid to the coarse part can be effectively promoted, and when the head cap separates from the nozzle surface, any residual fluid is pulled by the effect of surface tension to the coarse part of the outside surface. Leaving fluid in the contact portion of the lip part can thus be prevented, production of fluid spray can be eliminated when the head cap separates from the nozzle surface, discharge defects caused by fluid adhering to the nozzle surface can be prevented, and a good fluid discharge state can be maintained. 
     Further preferably, the fluid discharge device according to another aspect of the invention has the inside circumference surface of the lip part is formed with an inside slope that tapers with gradually decreasing wall thickness toward the peak part of the contact portion to a point when seen in section, and the outside circumference surface of the lip part is formed with an outside slope that tapers with gradually decreasing wall thickness toward the peak part of the contact portion to a point when seen in section. This aspect of the invention is preferable because the contact portion is compressed with the peak rendered by both slope parts being pushed in, and fluid left at the contact part therefore does not scatter. 
     In a fluid discharge device according to another aspect of the invention the smooth parts are formed by reducing the surface roughness of the die used to mold the lip part. 
     With the fluid discharge device according to another aspect of the invention the smooth parts of the lip part can be easily formed by reducing the surface roughness of the die used to mold the lip part, and adhesion of fluid on the discharge nozzle can be suppressed at low cost. 
     Another aspect of the invention is a printer that has the fluid discharge device of the invention and prints on a print medium by discharging ink droplets from the discharge nozzle. 
     The reliability of ink discharge from the ink nozzles of a printer according to this aspect of the invention is high, and high quality printing can thus be assured. 
     Another aspect of the invention is a media processing device that applies an information process to flat media, and has the printer according to the present invention for printing on the media. 
     The media processing device according to this aspect of the invention can print with high quality on the label side of flat print media such as CDs and DVDS. 
     Other objects and attainments together with a fuller understanding of the invention will become apparent and appreciated by referring to the following description and claims taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an external oblique view of a media processing device (publisher) according to the present invention. 
         FIG. 2  is an oblique view from the front of the publisher shown in  FIG. 1  with the front access covers open. 
         FIG. 3  is an oblique view from the front [back?] of the publisher in  FIG. 1  with the case removed. 
         FIG. 4  is an oblique view of the label printer assembly disposed in the publisher in  FIG. 1 . 
         FIG. 5  is an oblique view describing the structure of the head maintenance mechanism in the printer shown in  FIG. 4 . 
         FIG. 6  is a front view describing the structure of the head maintenance mechanism in the printer shown in  FIG. 4 . 
         FIG. 7  shows a portion of the head cap shown in  FIG. 5 ,  FIG. 7A  being an external section view of the head cap shown partially in section, and  FIG. 7B  being an section view, seen from inside the head cap shown partially in section. 
         FIG. 8  is an oblique view describing operation of the head maintenance mechanism in the printer shown in  FIG. 4 . 
         FIG. 9  is a front view describing operation of the head maintenance mechanism in the printer shown in  FIG. 4 . 
         FIG. 10  describes adhesion of ink to the head cap according to the present invention,  FIG. 10A  to  FIG. 10C  being schematic section views of the head cap and the nozzle surface. 
         FIG. 11  is a table describing the relationship between the surface roughness of the lip and the condition of ink. 
         FIG. 12  describes the adhesion of ink in a head cap according to the related art,  FIG. 12A  to  FIG. 12C  being schematic section views of the head cap and the nozzle surface. 
     
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     A preferred embodiment of a fluid discharge device, a printer, and a media processing device according to the present invention is described below with reference to the accompanying figures. 
     The media processing device of the invention is described below using a disc publisher by way of example. 
       FIG. 1  is an external oblique view of the publisher (media processing device) when all units are closed.  FIG. 2  is an external oblique view of the publisher with the access doors and disc tray open.  FIG. 3  is an oblique view from the top front side of the publisher with the case removed.  FIG. 4  is an oblique view of the label printer assembly incorporated in the publisher.  FIG. 5  is an oblique view describing the drive mechanism in the label printer unit. 
     As shown in  FIG. 1 , the publisher  1  is a media processing device that writes data to and/or reads data from, and prints on the label side of, disc-shaped media (data recording media) such as CDs and DVDs, and has a basically box-shaped case  2 . Doors  3  and  4  that open and close to the right and left are attached at the front of the case  2 . An operating panel  5  having various indicators and operating buttons is disposed at the top left part (left as seen from the front) of the case  2 , and support legs  6  project down from the bottom of the case  2  on both right and left sides. A drawer mechanism  7  is disposed between the right and left legs  6 . 
     As shown in  FIG. 2 , the access door  3  on the left side of the device (the right side as seen from the front) opens and closes for access to an open area  8  at the front of the publisher  1 , and is a door that opens and closes for loading unused (blank) media M and removing finished media M from the open area  8 . 
     The access door  4  on the right side of the device (the left side as seen from the front) opens and closes for replacing the ink cartridges  12  of the label printer  11  shown in  FIG. 3 . When the door  4  is open, a cartridge carrier unit  14  with a plurality of cartridge holders  13  arrayed in a vertical stack is exposed. 
     A media stacker  21  (media storage unit) for holding a plurality of unused blank discs M (such as 50) to which data has not been written in a vertical stack, and another media stacker  22  (media storage unit) for similarly holding a plurality of completed discs M or blank discs M (such as 50) are disposed inside the case  2  of the publisher  1 . Media stacker  21  and media stacker  22  are disposed one above the other so that the media M are stored coaxially in the stackers. Both media stacker  21  and media stacker  22  can be freely installed to and removed from predetermined positions. 
     The top media stacker  21  has a pair of right and left curved side walls  24  and  25 . The blank discs M are placed from the top into the blank media stacker  21  between the side walls  24  and  25 , which hold the discs in a substantially coaxial stack. The task of storing or adding the blank discs M to the blank media stacker  21  can be done easily by opening the door  3  and pulling the media stacker  21  out. 
     The bottom media stacker  22  is identically constructed with a pair of right and left curved side walls  27  and  28 , enabling the discs M to be inserted from the top and stored in a substantially coaxial stack. 
     A media transportation mechanism  31  is located behind the media stackers  21  and  22 . The media transportation mechanism  31  has a vertical guide shaft  35  disposed between the main frame  30  and the top plate  33  of the chassis  32 . A transportation arm  36  is supported so that it can move up and down and rotate on the vertical guide shaft  35 . The transportation arm  36  can move vertically up and down along the vertical guide shaft  35  and can pivot right and left on the vertical guide shaft  35  by means of a drive motor  37 . 
     Two media drives  41  are disposed one above the other at the back beside the two stackers  21  and  22  and the media transportation mechanism  31 , and the carriage  62  (see  FIG. 4 ) of the label printer  11  is disposed so that it can move below the media drives  41 . 
     Each of the media drives  41  has a media tray  41   a,  which can move between a data writing position where data is recorded to the media M, and a media transfer position where the media M can be loaded and unloaded from the media tray  41   a . The media drive  41  can read or write data to the media M on the media tray  41   a  when in the retracted position. 
     The label printer  11  also has a media tray  45  that can move between a printing position for printing a label on the label side of the media M, and a media transfer position where the media can be loaded and unloaded from the media tray  45 . 
       FIG. 3  shows the media trays  41   a  of the top and bottom media drives  41  pulled out to the media transfer position, and the media tray  45  of the label printer  11  at the media transfer position. 
     The label printer  11  in this example is an inkjet printer that uses color ink cartridges  12  (for six colors, specifically, black, cyan, magenta, yellow, light cyan, and light magenta) as the ink supply mechanism  60 . The ink cartridges  12  are installed from the front to the individual cartridge holders  13  of the cartridge carrier unit  14 . 
     A space enabling the transportation arm  36  of the media transportation mechanism  31  to move up and down is formed between the pair of right and left side walls  24  and  25  of the one media stacker  21  and between the pair of right and left side walls  27  and  28  of the other media stacker  22 . A space is also formed between the top and bottom media stackers  21  and  22  so that the transportation arm  36  of the media transportation mechanism  31  can pivot horizontally for positioning directly above the bottom media stacker  22 . When media trays  41   a  are pushed into the media drives  41 , the transportation arm  36  of the media transportation mechanism  31  descends and can access the media tray  45  of the label printer  11  at the media transfer position. 
     When both media trays  41   a  are in the data writing position and the media tray  45  for the label printer  11  is at the inside printing position, the transportation arm  36  of the media transportation mechanism  31  can descend below the height of the printer media tray  45 . A guide hole  65  is formed below the media transfer position of the printer media tray  45 . When the media transportation arm  36  descends to this position and releases a disc, the disc passes through the guide hole  65 . A media stacker further described below can also be installed in this guide hole  65  (see  FIG. 2 ). 
     The drawer mechanism  7  has a tray  70  disposed below the main frame  30  so that the tray  70  can slide closed inside the main frame  30  or pull out of the main frame  30  to open. The tray  70  has a recessed stacker unit  71 . When the tray  70  is in the stored (closed) position, the stacker unit  71  is positioned below the guide hole  65 , and the center of the stacker unit  71  is positioned with the center of the stacker unit  71  coaxial to the center axis of the media trays  41   a  and the printer media tray  45  in the media transfer position. The stacker unit  71  accepts media M guided thereinto by the guide hole  65 , and stores a relatively small number of media M (such as 5 to 10). The stacker unit  71  accepts the media M from the top and stores the media M in a coaxial stack. 
     A media stacker  72  (removable media stacker) that can hold more media X than the stacker unit  71  is removably disposed in the guide hole  65  and tray  70  in the closed position (see  FIG. 3 ). This media stacker  72  also has two curved side walls  73  and  74 . Media M can be loaded from the open top between the side walls  73  and  74 , and a plurality of media M (such as 50) can be stored coaxially in a stack between the side walls  73  and  74 . A gap enabling the transportation arm  36  of the media transportation mechanism  31  to move up and down is also formed between the pair of curved side walls  73  and  74 . A handle  75  that is held by the user when installing and removing the media stacker  72  is disposed at the top part of the one side wall  74 . 
     When the media stacker  72  is installed, a blank disc M is taken from the bottom media stacker  22 , written and printed by a media drive  41  and the label printer  11 , and then deposited in the media stacker  72 . 
     When both the top media stacker  21  and the bottom media stacker  22  are loaded to capacity (50+50 discs in this embodiment of the invention) with blank media M, all media M (50) in the bottom media stacker  22  are sequentially processed and stored in the media stacker  72 , and all media M (50) in the top media stacker  21  are then sequentially processed and stored in the emptied bottom media stacker  22 . This enables batch processing the maximum number of media M (50+50) that can be loaded in the top media stacker  21  and the bottom media stacker  22  in a single operation (the “batch processing mode”). 
     If the media stacker  72  is removed, a blank disc M can be removed from the top media stacker  21  or the bottom media stacker  22 , and can be stored in the stacker unit  71  of the tray  70  in the stored (closed) position after the disc is written and printed by the media drive  41  and label printer  11 . 
     The completed media M can thus be removed from the stacker unit  71  by pulling the drawer tray  70  out. More specifically, completed media M can be sequentially removed one by one or plural discs at a time while processing other media M continues and the access door  3  remains closed. This is also referred to herein as the “external discharge mode.” 
     The media M can thus be appropriately conveyed between the media stackers  21 ,  22 , the stacker unit  71  (or media stacker  72 ) of the tray  70 , the media trays  41   a  of the media drives  41 , and the printer media tray  45  of the label printer  11  by moving the transportation arm  36  of the media transportation mechanism  31  in various ways up and down while pivoting right or left. 
     As shown in  FIG. 4 , the label printer  11  has a carriage  62  with an inkjet head  61  having nozzles (not shown in the figure) for discharging ink. The carriage  62  moves bidirectionally horizontally along a carriage guide shaft by means of the drive power from a carriage motor. 
     The label printer  11  has an ink supply mechanism  60  with a cartridge carrier unit  14  in which the ink cartridges  12  are installed. The ink supply mechanism  60  is vertically constructed and is attached perpendicularly to the main frame  30  of the publisher  1 . One end of a flexible ink supply tube  63  is connected to the ink supply mechanism  60 , and the other end of the ink supply tube  63  is connected to the carriage  62 . 
     Ink in the ink cartridges  12  loaded in the ink supply mechanism  60  is supplied through the ink supply tube  63  to the carriage  62 . The ink is supplied to the inkjet head  61  through the damper unit and back pressure adjustment unit (not shown in the figure) disposed to the carriage  62 , and discharged from the ink nozzles (not shown in the figure). 
     A pressurizing mechanism  64  is disposed with the main part at the top of the ink supply mechanism  60 , supplies compressed air to pressurize the inside of the ink cartridge  12  and expels ink from the ink pack in the ink cartridge  12 . 
     A head maintenance mechanism  81  is disposed below the home position (shown in  FIG. 4 ) of the carriage  62 . 
     The head maintenance mechanism  81  has a head cap  82  and a waste ink suction pump  83 . The head cap  82  covers the ink nozzles of the inkjet head  61  exposed below the carriage  62  in the home position. The waste ink suction pump  83  vacuums ink discharged into the head cap  82  by the ink charging operation and the head cleaning operation of the inkjet head  61 . 
     Ink that is removed by the waste ink suction pump  83  of the head maintenance mechanism  81  is discharged through another tube  84  into the waste ink absorption tank  85 . This waste ink absorption tank  85  is an absorption member not shown that is disposed inside the case  86 , and has a cover  88  with numerous ventilation holes  87 . 
     A waste ink catch pan  89  that is a part of the waste ink absorption tank  85  is disposed below the head maintenance mechanism  81  to catch and absorb ink that drips from the head maintenance mechanism  81  with an absorbent material. 
     The head maintenance mechanism  81  is described next. 
       FIG. 5  is an oblique view describing the structure of the head maintenance mechanism, and  FIG. 6  is a front view describing the structure of the head maintenance mechanism.  FIG. 7A  is an external oblique view of the head cap shown partially in section with the inside omitted, and  FIG. 7B  is a section view seen from inside the head cap shown partially in section.  FIG. 8  is an oblique view describing operation of the head maintenance mechanism, and  FIG. 9  is a front view describing operation of the head maintenance mechanism. 
     As shown in  FIG. 5  and  FIG. 6 , the head maintenance mechanism  81  has a head capping mechanism  101  and a wiper mechanism  102 . The head capping mechanism  101  is for sealing the nozzle surface  61   a  of the inkjet head  61 , and the wiper mechanism  102  is for wiping the nozzle surface  61   a.    
     The head capping mechanism  101  has a cap slider  111 . The cap slider  111  is container-shaped, and can slide in the directions to and away from the nozzle surface  61   a  of the inkjet head  61 . 
     A cap holder  112  is held in the recessed top part of the cap slider  111  so that the cap holder  112  can move in and out of the cap slider  111 . The head cap  82  is affixed to the distal end part of the cap holder  112 . 
     As shown in  FIG. 7A  and  FIG. 7B , the head cap  82  is box-shaped with an opening of a size enabling sealing the nozzle surface  61   a,  with the inside of the head cap  82  rendering a storage recess  90 . 
     The head cap  82  includes a case  91  made of hard plastic, for example, and a lip  92  that is made of a flexible elastomer and is disposed to the wall that forms the storage recess  90  of the case  91 . The lip  92  is rendered in unison with the case  91  by means of a double-shot molding process. In this case the case  91  is injection molded in a first step, and the lip  92  is then injection molded from a thermoplastic elastomer in the second step. The lip  92  has an inside slope  93  and an outside slope  94  rendered on the front and back side of the peak  92   a  at the distal end, and when seen in section tapers gradually towards the nozzle surface  61   a  to a narrow point. When the head cap  82  approaches the inkjet head  61 , the near end portion of the lip  92  including the peak  92   a  goes tight to the nozzle surface  61   a.    
     The inside slope  93  of the lip  92  is formed as a smooth part  93   a  with low surface roughness. The outside slope  94  has a smooth part  94   a  with low surface roughness and a coarse part  94   b  with high surface roughness. The smooth part  94   a  is formed in the upper portion of the outside slope  94  from the peak  92   a  to about halfway down from the distal end, and the coarse part  94   b  is formed in the lower half separated from the peak  92   a . The smooth parts  93   a  and  94   a  of the inside slope  93  and outside slope  94  of the lip  92  are rendered with a surface roughness Ra of 2.20 by rendering the corresponding surfaces of the die for molding the lip  92  with a surface roughness Ra of 0.068. The coarse part  94   b  of the outside slope  94  of the lip  92  is rendered with a surface roughness Ra of 4.34 by increasing the surface roughness of the corresponding surface of the die for molding the lip  92  to 1.358 Ra. 
     Because the surface roughness of the smooth parts  93   a  and  94   a  is low, the surface tension of the ink reduces the contact angle of the ink if ink clings to the smooth part. As a result, if ink gets on smooth part  93   a  or  94   a , the effect of gravity causes the ink to easily move down, and the chance of ink moving upward to the peak  92   a  or remaining on the smooth part is reduced. 
     A multiple layer absorption member  95  for absorbing waste ink in the storage recess  90  is held in the head cap  82 . The absorption member  95  is held by a pressure member  96 , and the top surface of the absorption member  95  is positioned below the distal end position of the lip  92 . 
     As shown in  FIG. 4 , a tube  84  is connected to the head cap  82 , and when the carriage  62  is in the standby position and the lip  92  of the head cap  82  is tight against the nozzle surface  61   a,  a waste ink suction pump  83  can be driven to lower the pressure inside the head cap  82  and vacuum ink from the ink nozzles of the inkjet head  61 . The waste ink that is removed from the nozzles travels through the tube  84  and is deposited into the waste ink absorption tank  85 . 
     As shown in  FIG. 5 , the wiper mechanism  102  has a wiper  121 , which is a flat rubber blade made of an elastic material. The wiper  121  is affixed to a wiper slider  122 , which is supported movably to and away from the inkjet head  61  in a direction perpendicular to the direction of inkjet head  61  movement. 
     The wiper  121  can move between a wiping position and a retracted position by moving the wiper slider  122 . As shown in  FIG. 5 , the wiping position is within the path of inkjet head  61  movement and the wiper  121  is moved to the wiping position during the wiping process for wiping ink and other contaminants from the nozzle surface  61   a . As shown in  FIG. 8 , the wiper  121  is removed from the path of inkjet head  61  movement when in the retracted position. 
     As shown in  FIG. 6 , the wiper  121  is disposed with its distal end protruding distance s to the inkjet head  61  side from the nozzle surface  61   a . As a result, when the wiper  121  is disposed to this wiping position and the inkjet head  61  is moved from the home position to the printing area, the wiper  121  rubs against the nozzle surface  61   a  of the inkjet head  61  as shown in  FIG. 9 , the nozzle surface  61   a  is wiped by the wiper  121 , and ink and other foreign matter on the nozzle surface  61   a  is removed. Note that depending on the type of ink, the wiper  121  may be made from a soft plastic. 
     As shown in  FIG. 5  and  FIG. 8 , the wiper mechanism  102  has an absorption member  123  disposed to the path of wiper  121  movement between the wiping position shown in  FIG. 5  and the standby position shown in  FIG. 8 . When the wiper  121  slides while in contact with the absorption member  123 , ink on the wiper  121  is wiped off by the absorption member  123 . 
     Note that the cap slider  111  of the head capping mechanism  101  and the wiper slider  122  of the wiper mechanism  102  both slide as a result of driving the waste ink suction pump  83 . 
     The label printer  11  cleans the inkjet head  61  by means of the head maintenance mechanism  81 . This cleaning process is executed at predetermined times or when initiated by the user, and includes an ink suction cleaning operation in which the head cap  82  is set tight to the nozzle surface  61   a  of the inkjet head  61  and the waste ink suction pump  83  is driven to vacuum the inside and remove ink that has increased in viscosity from the ink nozzles of the inkjet head  61 , and a wiping operation for wiping contamination from the nozzle surface  61   a  of the inkjet head  61  by means of the wiper  121 . 
     The head maintenance mechanism  81  of the label printer  11  can also execute flushing and capping operations. The flushing operation discharges a predetermined amount of ink from the ink nozzles of the inkjet head  61  into the head cap  82  before printing starts or at a regular interval in order to maintain an appropriate ink meniscus in the ink nozzles of the inkjet head  61 . The capping operation sets the head cap  82  tightly to the nozzle surface  61   a  of the inkjet head  61  in order to protect the nozzle surface  61   a  when not printing and prevent clogging of the ink nozzles as a result of evaporation. 
     As shown in  FIG. 10A , in a label printer  53  according to this embodiment of the invention, ink I absorbed by the absorbent material  95  in the storage recess  90  will not travel up along the inside slope  93  and rise to the peak  92   a  as a result of surface tension (capillary action) even if the head cap  82  is set tight against the nozzle surface  61   a  of the inkjet head  61  because the inside slope  93  at the lip  92  of the head cap  82  is a smooth part  93   a  with low surface roughness. As a result, adhesion of ink I where the peak  92   a  touches the nozzle surface  61   a  is substantially eliminated. 
     In addition, because the part of the outside slope  94  from the peak  92   a  down to the coarse part  94   b  is a smooth part  94   a  with low surface roughness, ink in the area of contact with the nozzle surface  61   a  moves easily downward, and leaving ink in this contact area is suppressed. 
     Therefore, as shown in  FIG. 10B , the production of ink spray when the head cap  82  separates from the nozzle surface  61   a  is eliminated and ink is prevented from adhering to the ink nozzles. 
     Furthermore, because a coarse part  94   b  is formed on the outside slope  94  separated from the peak  92   a , even if some ink I is left in the area of contact between the lip  92  of the head cap  82  and the nozzle surface  61   a , the ink left in this contact area moves down through the smooth part  94   a  on the peak  92   a  and is drawn into the coarse part  94   b  of the outside slope  94  due to the strong surface tension effect of the coarse part  94   b  when the head cap  82  separates from the nozzle surface  61   a  as shown in  FIG. 10C . 
     Because ink on the outside slope  94  is attracted by the coarse part  94   b  and collection of fluid on the smooth part  94   a  is thus suppressed, ink is prevented from spraying when the head cap  82  separates from the nozzle surface  61   a , and ink I is prevented from clinging to the ink nozzles. 
     As a result of identifying that the condition of the ink I changes according to the surface roughness of the inside slope  93  at the lip  92  of the head cap  82 , the relationship with surface roughness was further explored experimentally. The results of the tests are described next with reference to  FIG. 11 . 
       FIG. 11  shows the results of tests exploring the relationship between the surface roughness of the lip and the ink condition. As shown in the figure, when the surface roughness Ra of the inside slope  93  of the lip  92  is 4.3, ink I may migrate along the inside slope  93  to the peak  92   a  at the point of contact with the nozzle surface. 
     When the surface roughness Ra is in the range 3.6-4, the ink I may or may not migrate upward along the inside slope  93  depending on other conditions. 
     When the surface roughness Ra is less than or equal to 3.2, the ink I will not rise. It was thus concluded that the surface roughness of the smooth parts  94   a  is preferably less than or equal to 3.2 Ra. 
     The surface roughness Ra of the coarse part  94   b , however, is preferably greater than or equal to 3.6, and it was confirmed that the effect of drawing fluid to the coarse part  94   b  of the outside slope  94  improves as the surface roughness rises. 
     If the surface roughness of the inside slope  93  of the lip  92  is greater than or equal to 3.6 Ra, which is not smooth, ink I absorbed by the absorbent material  95  in the storage recess  90  will migrate along the inside slope  93  as a result of surface tension and rise to the area of contact with the nozzle surface  61   a  as shown in  FIG. 12A . 
     As a result, when the head cap  82  separates from the nozzle surface  61   a  as shown in  FIG. 12B , a film of ink I is formed between the lip  92  and the nozzle surface  61   a . When this film of ink I then breaks, the ink I scatters as shown in  FIG. 12C  and clings to the ink nozzles, resulting in deficient ink discharge from the ink nozzles. 
     Because the inside slope  93  of the lip  92  part of the head cap  82  is a smooth part  93   a  with a surface roughness Ra of 3.2 or less, ink I left on the lip  92  will not migrate up the inside slope  93  in this embodiment of the invention even if the head cap  82  is set tightly against the nozzle surface  61   a  of the inkjet head  61 , and the adhesion of ink to the parts in contact with the nozzle surface  61   a  can be completely or substantially eliminated. 
     Production of ink spray when the head cap  82  separates from the nozzle surface  61   a  can thus be eliminated, discharge defects caused by ink on the ink nozzles can be prevented, and good ink discharge can be maintained. 
     The label side of flat print media M, such as CDs and DVDs, can thus be printed with high quality. 
     More particularly, because a coarse part  94   b  with higher surface roughness than the smooth part  94   a  near the peak  92   a  is rendered on a part of the outside slope  94  of the lip  92  separated from the nozzle surface  61   a , if some ink is left in the area where the lip  92  of the head cap  82  contacts the nozzle surface  61   a , the remaining ink is drawn by the surface tension effect to the coarse part  94   b  of the outside slope  94  when the head cap  82  separates from the nozzle surface  61   a . Ink spray can thus be prevented, and the adhesion of ink on the ink nozzles can be better prevented. 
     The smooth parts  93   a  and  94   a  can be easily formed by polishing or otherwise reducing the surface roughness of the die used to mold the lip  92 , and adhesion of ink on the ink nozzles can thus be prevented at low cost. 
     It will be obvious to one with ordinary skill in the related art that the invention is not limited to the foregoing embodiment and can be changed in many ways without departing from the scope of the accompanying claims. 
     For example, the inside slope  93  of the lip  92  is rendered as a smooth part  93   a  with low surface roughness, and the peak  92   a  and smooth part  94   a  of the outside slope  94  are rendered with the same surface roughness in the foregoing embodiment. However, ink I inside the head cap  82  is effectively prevented from moving to the contact area at the peak  92   a  even if a smooth part  93   a  with low surface roughness is rendered only on the inside slope  93 , while additionally rendering a smooth part  94   a  on the peak  92   a  side of the outside slope  94  can further effectively reduce the amount of ink that tends to stay at the nozzle surface  61   a . 
     In addition, an inside slope  93  and an outside slope  94  are rendered at the distal end side of the contact part of the lip  92 . However, when a slope is rendered on only one side, whether the slope is on the inside circumference side or the slope is on the outside circumference side, the peak part is deflected to one side when the peak part (contact part) is pressed against the nozzle surface  61   a . More particularly, if a slope is not rendered on the inside circumference side and a slope is rendered only on the outside side, the peak part is deflected to the inside, and if a slope is not rendered on the outside circumference side and a slope is rendered only on the inside side, the peak part is deflected to the outside. As a result, when the lip  92  then separates from the nozzle surface  61   a , the peak returns to the original non-deflected position, and the chance of ink left at this contact part being sprayed increases. However, by rendering both an inside slope  93  and an outside slope  94  as in the embodiment described above, the peak  92   a  is simply pushed in and compressed, and ink I left at the contact part is not sprayed. 
     Furthermore, while the contact part may be a contact surface instead of a peak, a contact part that goes to a peak is preferable because less ink can be left at the contact area than when the contact part is a contact surface. 
     In addition, a coarse part  94   b  with higher surface roughness than the smooth part  94   a  on the peak  92   a  side is rendered on the outside slope  94  of the lip  92  at a position removed from the peak  92   a . The smooth part  94   a  may be rendered only where ink can remain easily at the peak  92   a , but rendering the smooth part  94   a  around the entire outside circumference is preferable because orientation is not required for installation and quality control is easier. 
     In addition, the surface roughness of the smooth parts on the inside and outside surfaces is the same in the foregoing embodiment, but the respective surface roughness may differ as long as the surface roughness is less than or equal to a centerline average surface roughness Ra of 3.2. The same surface roughness is preferable, however, because of the simplicity and ease of quality control and managing the dies used to mold the lip part. 
     The foregoing is described using a label printer for printing on the label side of flat media by way of example, but the invention can obviously also be used in printers that print to paper. 
     The foregoing is also described using double-shot molding by way of example, but a lip  92  made of synthetic rubber may be affixed to the case  91  or rendered by insert molding. Double-shot molding is preferred, however, because of simple parts management and low cost. 
     The fluid discharge device of the invention may be used in inkjet printers as in the embodiment described above, but the invention is not so limited. More particularly, the fluid discharge device of the invention may be any fluid discharge device that uses a fluid discharge head to discharge a fluid, such as color agent discharge heads used for manufacturing color filters for liquid crystal displays, electrode material discharge heads used for electrode manufacture in organic electroluminescent displays and field emission displays (FED), and biomaterial discharge heads used in biochip manufacture. The fluid discharge device of the invention may also be used in other devices, such as reagent discharge devices used as precision pipettes. 
     Although the present invention has been described in connection with the preferred embodiments thereof with reference to the accompanying drawings, it is to be noted that various changes and modifications will be apparent to those skilled in the art. Such changes and modifications are to be understood as included within the scope of the present invention as defined by the appended claims, unless they depart therefrom.