Patent Publication Number: US-9403360-B2

Title: Print device and print method

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the priority benefit of Japan application serial no. 2014-044264, filed on Mar. 6, 2014. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification. 
     TECHNICAL FIELD 
     The present disclosure relates to a print device and a print method. 
     DESCRIPTION OF THE BACKGROUND ART 
     Conventionally, ink jet printers employing an ink jet method are widely used (for example, internet URL http://www.mimaki.co.jp.). In the ink jet printer, ink droplets are discharged from nozzles of ink jet heads so that printing is performed. Further, a driving element for discharging ink droplets from each nozzle is provided on each position of each nozzle in the ink jet head. For example, a piezoelectric element is widely used as such a driving element. 
     SUMMARY 
     In recent years, it is desired according to heightening of demanded print quality to discharge ink droplets from nozzles with higher accuracy. For this reason, conventionally, for example, a constitution where ink droplets are discharged from the nozzles more stably is desired. It is, therefore, the present disclosure to provide a print device and a print method that can solve the above problem. 
     In the ink jet printer, in recent years, it is desired to discharge small droplets of small capacity in order to perform more precise printing. Further, when printing is performed by an ink jet method, ink discharged from the nozzles is influenced by air resistance until it reaches media. When the capacity of ink droplets is small, they are easily influenced by the air resistance. 
     Further, it is considered that the influence of the air resistance becomes larger as a discharge speed (initial speed) of the ink droplets is lower. For this reason, when ink droplets of small capacity are discharged, in order to reduce the influence of the air resistance, it is desired that the discharge speed of ink droplets is sufficiently heightened. Therefore, a more concrete example of a constitution in which ink droplets from nozzles can be discharged more stably is a constitution in which the discharge speed can be sufficiently heightened even when the capacity of ink droplets is small. 
     In order to solve the above problem, the present disclosure has the following constitution. 
     (Constitution 1) A print device for performing printing using an ink jet method includes an ink jet head for discharging ink droplets, and a drive signal output section for outputting a drive signal for allowing the ink jet head to discharge ink droplets. The ink jet head includes a nozzle for discharging ink droplets, an ink chamber for storing ink to be supplied to the nozzle at a former stage of the nozzle which has a hole connected to the nozzle on any surface thereof and an opening on a position different from the hole, an opening section thin film that is a thin film for covering the opening of the ink chamber, and a piezoelectric element for applying pressure to the ink chamber through displacement according to the drive signal, and the piezoelectric element is disposed on the opening section thin film with a main surface of the element along the opening section thin film. 
     In such a constitution, the piezoelectric element is displaced according to the drive signal so as to, for example, curve on the opening section thin film. With this displacement, pressure is applied to the ink chamber via the opening section thin film. In this case, when the piezoelectric element is disposed so that its main surface overlaps with the opening of the ink chamber, it can make contact with the opening section thin film on a wider area than a case where it is disposed vertically with respect to the ink chamber. Further, for example, it is considered that the piezoelectric element is displaced into a shape of the ink chamber. For this reason, such a constitution enables the pressure to be stably applied to the ink chamber due to the piezoelectric element. As a result, ink droplets can be discharged from the nozzle more stably. 
     The main surface of the piezoelectric element is the widest surface on the piezoelectric element. Further, arranging the piezoelectric element vertically is arranging the piezoelectric element so that the piezoelectric element elongates and contracts in a direction vertical to the opening section thin film like the arrangement of the piezoelectric element in conventional ink jet heads. 
     In the ink chamber, the hole connected to the nozzle is formed on, for example, a bottom surface of a cavity composing the ink chamber. Further, the opening of the ink chamber is formed on a surface opposed to the bottom surface. 
     (Constitution 2) The piezoelectric element curves with its center portion towards the nozzle according to a change in the drive signal, the pressure is applied to the ink chamber via the opening section thin film, and ink droplets are discharged from the nozzle according to the pressure applied to the ink chamber by the piezoelectric element. In such a constitution, ink droplets can be suitably discharged from the nozzle. 
     (Constitution 3) The piezoelectric element has an electrode that receives the drive signal on one end and the other end in a direction along a surface of the opening section thin film. The direction along a surface of the opening section thin film is a direction perpendicular to a discharge direction of ink droplets from the nozzle. Such a constitution enables the piezoelectric element to be suitably displaced. 
     (Constitution 4) When inner volume of the ink chamber is set to V0 and capacity of single discharge of ink droplets from the nozzle is set to V1, V1/V0 is 0.5 or more. In this case, ink droplets with capacity of 50% or more in the inner volume of the ink chamber are discharged from the nozzle. The proportion V1/V0 between the inner volume of the ink chamber and the capacity of the ink droplets is preferably 0.9 (90%) or more. Further, it is preferable that the proportion V1/V0 is approximately 1.0 (100%). 
     In the constitution of the conventional ink jet head, ink droplets are discharged by, for example, separating partial ink from meniscus formed on the position of the nozzle. More concretely, in the conventional constitution, for example, the piezoelectric element is displaced to a direction where ink is pushed out from the nozzle and then to a direction where the ink is pulled back into the nozzle according to a change in the drive signal (push-pull method). As a result, partial ink pushed out from the nozzle is separated from the meniscus, and the separated ink droplets are allowed to fly toward a medium being subject to print. 
     In this case, since only a part of the ink in the ink chamber is discharged from the nozzle, the proportion V1/V0 between the inner volume of the ink chamber and the capacity of the ink droplets is normally 0.01 (1%) or less. When ink droplets are discharged in this method, a size of the ink droplets is determined according to the balance of a plurality of forces such as a force for pushing out ink from the nozzle and a force for pulling back the ink into the nozzle. For this reason, it is difficult to uniform the size of ink droplets with high accuracy, and thus the capacity of ink droplets (size) might easily vary. 
     When ink droplets are discharged by the above method and the force for pushing out the ink from the nozzle is made to be too strong, the ink droplets become larger simultaneously with a rise in the speed of the ink droplets. For this reason, it is occasionally difficult to make the force for pushing out the ink from the nozzle strong with the size of the ink droplets being small. As a result, when ink droplets of small capacity are discharged, it is occasionally difficult to heighten the discharge speed of the ink droplets. 
     On the contrary, in the constitution 4 where the most part of ink in the ink chamber is discharged as ink droplets, the capacity of the ink droplets varies less occasionally than the case where the ink of only little part (for example, 1% or less) of the inner volume of the ink chamber is discharged. Further, in order to discharge the most part of ink in the ink chamber as ink droplets, not the above push-pull method but a constitution where the ink is pushed out directly by the displacement of the piezoelectric element is considered to be used. In this case, the balance of the ink pushing force and pulling force does not have to be taken into consideration. For this reason, the capacity of ink droplets hardly varies also from this point. 
     In this case, the constitution where the most part of ink in the ink chamber is discharged as ink droplets enables the ink pushing force to be sufficiently strong even when the capacity of the ink droplets is small. For this reason, such a constitution enables ink droplets of small capacity to be discharged suitably at a sufficient discharge speed. As a result, high-definition printing can be performed suitably. 
     In this case, the constitution where the most part of ink in the ink chamber is discharged enables use of the ink chamber whose inner volume is as small as the capacity of ink droplets. For this reason, the ink chamber of small depth can be used. As a result, when the ink chamber is formed by etching, for example, the ink chamber can be manufactured more easily with high accuracy. 
     (Constitution 5) The piezoelectric element is displaced into the shape along the surface on which the hole connected to the nozzle is formed in the ink chamber so as to allow the nozzle to discharge ink droplets. Such a constitution enables the most part of ink in the ink chamber to be suitably discharged when ink droplets are discharged from the nozzle. 
     The displacement of the piezoelectric element into the shape along the surface formed with the hole connected to the nozzle (nozzle formed surface) means the displacement of the piezoelectric element that pushes the most part of ink in the ink chamber to the nozzle. The most part of ink in the ink chamber is, for example, ink that is 50% or more, preferably 90% or more, and more preferably approximately 100% of the inner volume of the ink chamber. Further, the displacement of the piezoelectric element into the shape along the nozzle foil ied surface may mean that the piezoelectric element are displaced so that the opening section thin film and the nozzle formed surface contact or approximately contact with each other. 
     (Constitution 6) The opening of the ink chamber is formed on a surface that is opposed to the nozzle formed surface on which the hole connected to the nozzle is formed in the ink chamber, and when the nozzle is made to discharge ink droplets, the piezoelectric element is displaced so that at least a part of the opening section thin film contacts with at least a part of the nozzle formed surface in the ink chamber. Such a constitution enables the most part of ink in the ink chamber to be suitably discharged when ink droplets are discharged from the nozzle. 
     It is preferable that the nozzle formed surface in the ink chamber is formed into a shape according to the displacement of the piezoelectric element (deflection of the piezoelectric element). For example, it is considered that the nozzle formed surface of the ink chamber has a shape where its depth gradually increases toward the center portion in a direction where one end and the other end of the piezoelectric element formed with the electrode are connected. Such a constitution enables the opening section thin film and the nozzle formed surface to contact with each other more suitably. 
     Further, for example, the portion that contacts with the opening section thin film is considered to be formed flat on the nozzle formed surface of the ink chamber. It is considered that particularly a peripheral portion of the hole connected to the nozzle on the portion that contacts with the opening section thin film is formed into a flat shape. The portion that contacts with the nozzle formed surface on the opening section thin film may be formed into a convex shape. Such constitutions enable the opening section thin film and the nozzle formed surface to contact with each other more suitably. 
     (Constitution 7) An ink storage section for storing ink to be supplied to the ink chamber, and an ink supply route for supplying the ink from the ink storage section to the ink chamber are further provided, and, the piezoelectric element performs first displacement so that its center portion is curved toward a direction opposite to the nozzle according to a change in the drive signal, then performs second displacement so that the center portion is curved towards the direction of the nozzle, ink is supplied from the ink storage section to the ink chamber via the ink supply route according to the first displacement of the piezoelectric element, and ink droplets are discharged from the nozzle according to the second displacement of the piezoelectric element. The ink storage section is an ink cartridge or an ink tank. 
     Such a constitution enables the ink to be suitably charged into the ink chamber according to the first displacement of the piezoelectric element before the ink droplets are discharged from the nozzle. Thereafter, the ink in the ink chamber can be suitably pushed out to the nozzle according to the second displacement of the piezoelectric element. As a result, the discharge of the ink droplets from the nozzle can be suitably performed. 
     In this constitution, it is preferable that the piezoelectric element allows the most part of ink in the ink chamber to be discharged from the nozzle according to the second displacement. In this case, a displacement magnitude of the first displacement is controlled so that the capacity of the ink to be introduced into the ink chamber can be suitably controlled before the discharge. Further, in this case, the inner volume in the ink chamber in the state that the piezoelectric element performs the first displacement can be considered as inner volume V0 in the ink chamber. Such a constitution enables a discharge quantity of ink droplets to be controlled suitably with high accuracy. As a result, high-definition printing can be suitably performed. 
     (Constitution 8) The print device changes the capacity of the ink droplets to be discharged from the nozzle at plural stages so as to perform multi-gradation printing, and the drive signal output section can output plural kinds of drive signals for making the displacement magnitude in the first displacement vary, and selects a drive signal to be supplied to the piezoelectric element for discharging the ink droplets to the nozzle according to the capacity of the ink droplets to be discharged from the nozzle. In this case, the piezoelectric element allows ink droplets of various capacities to be discharged from the nozzle according to any one of the plural kinds of drive signals to be supplied. 
     In such a constitution, different kinds of drive signals for making the displacement magnitude in the first displacement vary are used so that the capacity of the ink droplets to be discharged from the nozzle can be varied according to the drive signals. As a result, the size of dots of ink to be formed on a medium through the nozzle can be varied at plural stages. For this reason, such a constitution enables the multi-gradation printing to be suitably performed. 
     In this case, as to the displacement magnitude of the piezoelectric element in the second displacement, the displacement magnitude is preferably such that most of the ink in the ink chamber after the first displacement is discharged from the nozzle. Such a constitution enables the capacity of the ink droplets to be discharged according to the respective drive signals to be suitably controlled with high accuracy. 
     The ink jet head may have a plurality of nozzles. In this case, the ink jet head has the ink chambers, the opening section thin films and the piezoelectric elements corresponding to the plurality of nozzles. The drive signal output section selects drive signals to be supplied to the nozzles according to the dot size of ink to be formed by the nozzles. Further, the selected drive signals are supplied to the nozzles, respectively. 
     (Constitution 9) A print method for performing printing using an ink jet method includes a step of outputting a drive signal for discharging ink droplets to an ink jet head for discharging ink droplets to the ink jet head, and the ink jet head has a nozzle for discharging ink droplets, an ink chamber having a hole connected to the nozzle on any surface and an opening on a position different from the hole which stores ink to be supplied to the nozzle at a former stage of the nozzle, an opening section thin film for covering the opening of the ink chamber, and a piezoelectric element for applying pressure to the ink chamber through displacement according to the drive signal, and the piezoelectric element is disposed on the opening section thin film so that a main surface of the element is along the opening section thin film. Such a constitution can produce the same effect as the constitution 1. 
     According to the present disclosure, when printing is performed by using the ink jet method, for example, ink droplets can be discharged from the nozzle more stably. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A and 1B  are diagrams illustrating one example of a print device  10  according to one embodiment of the present disclosure;  FIG. 1A  illustrates one example of a constitution of a main section of the print device  10 ;  FIG. 1B  illustrates one example of a constitution of an ink jet head  12  in the print device  10 ; 
         FIGS. 2A and 2B  are diagram illustrating a detailed constitution around a nozzle  102  for discharging ink droplets in the ink jet head  12 ;  FIG. 2A  is a top view illustrating one example of the constitution around the nozzle  102 ;  FIG. 2B  is a cross-sectional view illustrating one example of the constitution around the nozzle  102 ; 
         FIGS. 3A to 3C  are diagrams illustrating one example of an operation for discharging ink droplets from the nozzle  102 ;  FIG. 3A  illustrates a state that a piezoelectric element  106  is not displaced due to a drive signal;  FIG. 3B  illustrates one example of a state that the piezoelectric element  106  is curved according to the drive signal;  FIG. 3C  illustrates one example of a state of respective sections in the ink jet head  12  at timing when the piezoelectric element  106  is curved; 
         FIGS. 4A and 4B  are diagrams describing first displacement that is displacement of the piezoelectric element  106  at timing when ink is supplied to an ink chamber  104 ;  FIG. 4A  illustrates one example of a state of a cross section that the piezoelectric element  106  is curved in the first displacement;  FIG. 4B  illustrates one example of a state of the respective sections of the ink jet head  12  at timing when the piezoelectric element  106  is curved in the first displacement of the piezoelectric element  106 ; 
         FIGS. 5A and 5B  are diagrams describing a case where capacity of the ink droplets is variable at plural stages;  FIG. 5A  illustrates one example of an operation for varying the capacity of the ink droplets at the plural stages;  FIG. 5B  illustrates one example of ink droplets  202   s ,  202   m  and  202   l  with plural kinds of capacities; 
         FIGS. 6A and 6B  illustrate one example of a constitution around the nozzle  102  in a modified example of the constitution of the ink jet head  12 ;  FIG. 6A  illustrates a first modified example of the constitution of the ink jet head  12 ; and  FIG. 6B  illustrates a second modified example of the constitution of the ink jet head  12 . 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     An embodiment of the present disclosure is described below with reference to the drawings.  FIGS. 1A and 1B  illustrate one example of a print device  10  according to one embodiment of the present disclosure.  FIG. 1A  illustrates one example of a constitution of a main section of the print device  10 .  FIG. 1B  illustrates one example of a constitution of an ink jet head  12  in the print device  10 . 
     In this example, the print device  10  is an ink jet printer that performs printing using an ink jet method on a medium  50 , and it has a plurality of ink jet heads  12 , a drive signal output section  14 , an ink tank  16 , and an ink supply route  18 . The plurality of ink jet heads  12  is ink jet heads that discharge ink droplets of different colors, respectively. The plurality of ink jet heads  12  may be ink jet heads for ink of CMYK colors, respectively, for example. 
     The plurality of ink jet heads  12  performs a main scanning operation for discharging ink droplets while moving to a preset main scanning direction (a direction Y in the drawings) so as to discharge ink droplets onto the medium  50 . A sub scanning operation during which the ink jet heads  12  moves to a sub scanning direction (a direction X in the drawing) perpendicular to the main scanning direction relatively with respect to the medium  50  is performed between an interval of the main scanning operations, so that a region of the medium  50  where the main scanning operation is performed is sequentially changed. With these operations, the plurality of ink jet heads  12  performs printing on respective positions on the medium  50 . 
     In this example, each of the ink jet heads  12  has, as shown in  FIG. 1B , a plurality of nozzles  102  arranged in the sub scanning direction. Each of the ink jet heads  12  discharges ink droplets through the nozzles according to a drive signal received from the drive signal output section  14 . 
     Not shown in  FIGS. 1A and 1B , but the ink jet head  12  further has a constitution for discharging ink droplets from nozzles  102 .  FIGS. 1A and 1B , for convenience of the description, illustrate an example of a constitution where only one nozzle row of the plurality of nozzles  102  is arranged in the sub scanning direction. However, when a speed and resolution are improved, a plurality of nozzle rows may be provided. Further, more concrete constitution and operation of the ink jet head  12  are described in detail later. 
     The drive signal output section  14  is a signal output section for outputting drive signals for allowing the plurality of ink jet heads  12  to discharge ink droplets. The drive signal output section  14  outputs drive signals to the nozzles  102  in each of the ink jet heads  12 , respectively, according to an image to be printed. In this example, to output drive signals to the nozzles  102  means outputting the drive signals to piezoelectric elements related to the nozzles  102 . 
     The ink tank  16  is one example of an ink storage section for storing ink to be supplied to the ink chambers in each of the ink jet head  12 . In this example, the ink tank  16  is disposed outside the ink jet heads  12 , and supplies ink to the ink jet heads  12  via the ink supply route  18 . An ink cartridge may be used as the ink storage section, for example. Further, the ink storage section may be disposed inside each of the ink jet heads  12 . The ink supply route  18  is, for example, an ink tube, and it connects the ink tank  16  to the respective ink jet heads  12  so that ink is supplied from the ink tank  16  to the respective ink jet heads  12 . In this constitution, the print device  10  performs printing using the ink jet method on the medium  50 . 
     Except for the above and following description, the print device  10  may have the constitution the same as or similar to that of the known ink jet printer. The print device  10  may further have various constitutions necessary for printing besides the above constitution. More concretely, the print device  10  may further have a driving section for allowing the plurality of ink jet heads  12  to perform the main scanning operation and the sub scanning operation. 
     Known various ink can be used as the ink to be used in the ink jet heads  12 . For example, UV ink that is cured by irradiation with ultraviolet or solvent UV ink obtained by diluting UV ink with organic solvent can be preferably used. Further, solvent ink or latex ink can be preferably used. The print device  10  may further have a constitution for fixing ink on the medium  50  according to a type of ink to be used. When UV ink or solvent UV ink is used, the print device  10  may further have a UV irradiation device. When ink that should be dried (solvent UV ink, solvent ink, latex ink, or emulsion ink) is used, the print device  10  may further have a heater. 
     The constitution and the operation of the ink jet heads  12  in this example are described in more detail below.  FIGS. 2A and 2B  illustrate the more detailed constitution of a periphery of the nozzle  102  for discharging ink droplets in the ink jet head  12 .  FIG. 2A  is a top view illustrating one example of the constitution around the nozzle  102  in a case where an internal constitution of the ink jet head  12  is viewed from a side opposite to a nozzle surface formed with the nozzle  102 .  FIG. 2B  is a cross-sectional view illustrating one example of the constitution around the nozzle  102  taken along alternate long and short dash line AA shown in  FIG. 2A . 
     As shown in  FIG. 1B , in this example, the ink jet head  12  has the plurality of nozzles  102  that is arranged in the sub scanning direction. The plurality of nozzles  102  is formed on a nozzle plate  150 . The ink jet head  12  further has the ink chamber  104 , a thin film  108 , and a piezoelectric element  106  on each position of each of the nozzles  102 . 
     The nozzle plate  150  is a plate-shaped body formed with the hole-shaped nozzles  102  and cavity sections connected to the nozzles  102 , respectively. The nozzle plate  150  may be a common member with respect to the plurality of nozzles  102 . In this case, the nozzle plate  150  is integrally constituted so that the plurality of nozzles  102  and the plurality of cavity sections are formed on one plate-shaped body. The nozzle plate  150  may be composed of, for example, a plurality of members. A liquid repellent layer (water repellent layer) may be formed on the surface of the nozzle plate. 
     In this example, the cavity sections of the nozzle plate  150  are covered with the thin film  108  so as to function as the ink chambers  104 . In this case, the ink chambers  104  mean regions where ink to be supplied to the nozzles  102  is stored at a former stage of the nozzles  102 . Each hole which is connected to each of the nozzle  102  is formed on a surface of the ink jet head  12  opposed to the medium  50  in each of ink chambers  104 . Each of the ink chambers  104  has an opening that is covered with each of the thin films  108  on a position different from each of the holes. More concretely, in the ink chamber  104 , the hole connected to the nozzle  102  is formed on a bottom surface of the cavity composing the ink chamber  104 . As a result, the bottom surface of the ink chamber  104  becomes a nozzle formed surface that is a surface formed with the hole connected to the nozzle  102 . The opening of the ink chamber  104  is formed on a surface opposed to the bottom surface. As a result, the ink chamber  104  stores the ink to be discharged from the nozzle  102  in a position adjacent to the nozzle  102 . 
     The thin film  108  is one example of an opening section thin film that is a thin film covering the opening of the ink chamber  104 . A flexible thin film that deforms according to displacement of the piezoelectric element  106  can be preferably used as the thin film  108 . The thin film  108  is a film that covers the cavity section on the nozzle plate  150  from an opposite side of the nozzle  102 . When the cavity section is covered, the ink chamber  104  is formed between the nozzle and the bottom surface of the cavity section. 
     The piezoelectric element  106  is a driving element for discharging ink droplets from the nozzle  102 . The piezoelectric element  106  is displaced according to a drive signal supplied from the drive signal output section  14  (see  FIGS. 1A and 1B ), so as to press the thin film  108  and apply pressure to the ink chamber  104 . As a result, the piezoelectric element  106  pushes a constant amount of ink in the ink chamber  104  out so as to discharge ink droplets from the nozzle  102 . 
     Further, in this example, the piezoelectric element  106  is a thin film type piezoelectric element that is disposed on the thin film  108  with its main surface along the thin film  108 . In this case, the main surface of the piezoelectric element  106  means, for example, the widest surface on the piezoelectric element  106 . Further, the main surface of the piezoelectric element  106  may be a main surface of the thin film composing the piezoelectric element. 
     More concretely, the piezoelectric element  106  is disposed so that the main surface overlaps with the opening of the ink chamber  104  and the discharge direction of ink droplets from the nozzle  102  is perpendicular to the main surface. The state that the main surface of the piezoelectric element  106  is perpendicular to the discharge direction of the ink droplets may mean a state that they are practically perpendicular to each other according to manufacturing accuracy of the components of the ink jet heads  12  with the piezoelectric element  106  not being displaced. More concretely, to be practically perpendicular may mean being perpendicular on the arrangement of design. 
     Further, in this example, the piezoelectric element  106  has an electrode  110  that receives a drive signal on one end and the other end in a direction along the surface of the thin film  108 . The direction along the surface of the thin film  108  means the direction perpendicular to the discharge direction of ink droplets from the nozzle  102 . 
     In such a constitution, the piezoelectric element  106  is displaced so as to be curved on the thin film  108  according to a drive signal. As a result of this displacement, pressure is applied to the ink chamber  104  via the thin film  108 . For this reason, in this example, the pressure can be applied to the ink chamber  104  stably and suitably. In this example, the displacement of the piezoelectric element  106  is controlled by a drive signal so that a constant amount of ink droplets can be suitably discharged from the nozzle  102 . 
     A known thin piezoelectric element can be preferably used as the piezoelectric element  106 . In this case, the piezoelectric element  106  is stuck on the thin film  108  so as to be disposed as described above. Further, the piezoelectric element  106  may be covered with coating resin on the thin film  108 . Such a constitution enables the piezoelectric element  106  to be disposed stably on the thin film  108 . It is also considered that by carrying out deposition or sputtering on the thin film  108  at a step of manufacturing the ink jet head  12 , the piezoelectric element  106  is formed on the thin film  108 . Such a constitution enables the piezoelectric element  106  to be disposed on a desired position with higher accuracy. 
     The electrode  110  of the piezoelectric element  106  may be disposed on one end and the other end of the piezoelectric element  106  in the direction along the surface of the thin film  108  so as to be partially placed on the thin film  108 . In this case, it is considered that a portion of the electrode  110  to be placed on the thin film  108  is adhered to the thin film  108 . Such a constitution enables the piezoelectric element  106  to be suitably fixed on the thin film  108 . Further, the electrode  110  is not disposed separately from the piezoelectric element  106 , but may be constituted as a part of the piezoelectric element  106 . In this case, it is preferable that the piezoelectric element  106  is formed on the thin film  108  by adhering it on an entire surface. 
     Not shown in the drawing, but the ink jet heads  12  further has an ink channel (ink supply section) that connects the ink supply route  18  (see  FIGS. 1A and 1B ) and the ink chamber  104 . The ink channel preferably has a position and a structure where it is closed or channel resistance increases at predetermined timing according to the operation of the piezoelectric element  106  at the time of discharge of ink droplets. 
     The displacement of the piezoelectric element  106  is described in more detail below. As described in more detail below, in this example, the piezoelectric element  106  discharges all the ink in the ink chamber  104  from the nozzle  102  at each discharge of ink droplets. 
     The operation for discharging ink droplets from the nozzle  102  according to the displacement of the piezoelectric element  106  is described in more detail below.  FIGS. 3A to 3C  illustrate one example of the operation for discharging ink droplets from the nozzle  102 .  FIG. 3A  illustrates a state that a piezoelectric element  106  is not displaced due to a drive signal. In the state that the piezoelectric element  106  is not displaced through a drive signal, the piezoelectric element  106  is not curved, namely, flat. In this case, the ink chamber  104  is charged with a predetermined initial capacity of ink. 
       FIG. 3B  is a diagram illustrating one example of a state that the piezoelectric element  106  is curved according to a drive signal, and illustrates one example of a state of a cross section taken along alternate long and short dash line BB shown in  FIG. 2A  where the piezoelectric element  106  is curved. In this case, the state of the cross section taken along alternate long and short dash line BB shown in  FIG. 2A  means a state of a cross section of a portion taken along alternate long and short dash line BB shown in  FIG. 2A  where the piezoelectric element  106  is curved.  FIG. 3C  illustrates one example of a state of respective sections in the ink jet head  12  at timing when the piezoelectric element  106  is curved. 
     In this example, the piezoelectric element  106  is curved with its center portion toward the nozzle  102  according to a change in the drive signal. As a result, the piezoelectric element  106  applies pressure to the ink chamber  104  via the thin film  108 . Further, ink droplets  202  are discharged from the nozzle  102  according to the pressure applied to the ink chamber  104  by the piezoelectric element  106 . For this reason, the ink droplets  202  can be suitably discharged from the nozzle  102 . 
     Further, in this example, when the ink droplets  202  are discharged from the nozzle  102 , the piezoelectric element  106  is displaced so that at least a part of the thin film  108  comes in contact with at least a part of the bottom surface of the ink chamber  104 . Such a constitution enables most of the ink in the ink chamber  104  to be suitably discharged at the time of the discharge of the ink droplets  202 . 
     The most of the ink in the ink chamber  104  means ink with 50% or more of an inner volume of the ink chamber  104 , preferably 90% or more, and more preferably approximately 100%. More concretely, when the inner volume of the ink chamber  104  is set to V0 and the capacity of single discharge of the ink droplets  202  from the nozzle  102  is set to V1, it is preferable that V1/V0 is 0.5 or more. This corresponds to a case where the capacity of single discharge of the ink droplets  202  from the nozzle is 50% or more of the inner volume in the ink chamber  104 . It is preferable that the proportion V1/V0 between the inner volume of the ink chamber  104  and the capacity of the ink droplets  202  is 0.9 (90%) or more. Further, it is preferable that the proportion V1/V0 is approximately 1.0 (100%). 
     More concretely, the piezoelectric element  106  is displaced so that the entire bottom surface of the ink chamber  104  comes in contact with the thin film  108  at the discharge of ink droplets  202 . As a result, the piezoelectric element  106  allows all the ink in the ink chamber  104  to be discharged as the ink droplets  202  from the nozzle  102 . 
     All the ink in the ink chamber  104  may be almost all ink that is practically all the ink. The discharge of practically all the ink in the ink chamber  104  from the nozzle means discharge of all the ink in the ink chamber  104  from the nozzle in design operation. This may be such that all the ink introduced into the ink chamber  104  before the discharge is discharged without intentionally leaving some ink through an operation for pulling back the ink into the nozzle  102  in the design operation. 
     The contact of the thin film  108  with the entire bottom surface of the ink chamber  104  means, as shown in  FIG. 3C , contact of the thin film  108  with the bottom surface of the ink chamber  104  with the thin film  108  covering the entire bottom surface of the ink chamber  104 . Further, the entire bottom surface of the ink chamber  104  means, for example, a portion of the bottom surface of the ink chamber  104  other than the hole connected to the nozzle  102 . 
     In the constitution of the conventional ink jet heads, a push-pull system is widely used as the system for discharging ink droplets. In this case, ink droplets are discharged by separating some ink from meniscus of the ink formed on the position of the nozzle. 
     In this case, however, since only some ink in the ink chamber is discharged from the nozzle, the proportion V1/V0 between the inner volume of the ink chamber and the capacity of ink droplets is normally about 0.01 (1%) or less. When ink droplets are discharged in this method, a size of the ink droplets is determined according to the balance of a plurality of forces such as a force for pushing out ink from the nozzle and a force for pulling the ink back into the nozzle. For this reason, it is difficult to uniform the size of ink droplets with high accuracy, and thus the capacity of ink droplets (size) might easily vary. 
     In the case where ink droplets are discharged by the push-pull method, for example, when the force for pushing the ink out from the nozzle is made to be too strong, the ink droplets becomes larger simultaneously with a rise in the speed of the ink droplets. For this reason, it is occasionally difficult to make the force for pushing out the ink from the nozzle strong with the size of the ink droplets being small. As a result, when ink droplets of small capacity are discharged, it is occasionally difficult to heighten the discharge speed of the ink droplets. 
     On the contrary, due to the constitution where the most of the ink in the ink chamber  104  is discharged as the ink droplets  202 , the capacity of the ink droplets  202  hardly varies compared to a case where ink whose capacity is only a small part of the inner volume of the ink chamber  104  (for example, about 1% or less) is discharged. In the constitution where the most of the ink in the ink chamber  104  is discharged as the ink droplets  202 , the ink can be directly pushed out not by the push-pull method but only by the displacement of the piezoelectric element  106  to the direction where pressure is applied to the ink chamber  104  at the discharge timing. In this case, the balance between the ink pushing-out force and the pulling-back force does not have to be taken into consideration. For this reason, also from this viewpoint, the capacity of the ink droplets  202  does not easily vary. 
     Further, in the constitution where the most of the ink in the ink chamber  104  is discharged as the ink droplets  202 , even when the capacity of the ink droplets  202  is small, the force for pushing out the ink can be sufficiently made to be strong without considering the operation for pulling back the ink into the ink droplets  202 . As a result, even when the capacity of the ink droplets is small, ink droplets can be discharged at a sufficient discharge speed (initial speed). For this reason, even when small ink droplets with small capacity are discharged, the discharge speed is sufficiently heightened, and an influence of air resistance on the ink droplets can be reduced. As a result, high-definition printing can be performed more suitably. 
     In the constitution where the most of the ink in the ink chamber  104  is discharged, when the inner volume of the ink chamber  104  is small, the ink droplets of necessary capacity can be suitably discharged. For this reason, the ink chamber  104  whose depth is small can be used in this example. As a result, when the ink chamber  104  is formed by etching, the ink chamber  104  can be easily manufactured with high accuracy. 
     More concretely, in this example, the bottom surface of the ink chamber  104  is formed into a shape that matches with the displacement of the piezoelectric element  106 . The displacement of the piezoelectric element  106  means deflection of the piezoelectric element  106  when the piezoelectric element  106  is curved according to a drive signal at the time of the discharge of the ink droplets  202 . More concretely, it is considered that the bottom surface of the ink chamber  104  has a round shape that accords with a curve amount of the piezoelectric element  106  and the shape where the depth becomes larger toward the center in a direction where one end and the other end on the piezoelectric element  106  that are provided with the electrode are connected. Such a constitution enables the thin film  108  and the bottom surface of the ink chamber  104  to contact with each other more suitably at the time of the discharge of the ink droplets  202 . Further, it is considered that the bottom surface has a round shape where the depth becomes larger toward the center also in a direction perpendicular to the direction where the electrodes on the piezoelectric element  106  are connected. 
     When the bottom surface of the ink chamber  104  has such a shape, the piezoelectric element  106  is displaced into a shape along the bottom surface of the ink chamber  104  at the time of the discharge of the ink droplets  202 . As a result, the piezoelectric element  106  discharges the most of the ink in the ink chamber  104  from the nozzle  102 . 
     Further, in this example, the piezoelectric element  106  is disposed so that the main surface overlaps with the opening of the ink chamber  104  via the thin film  108 . For this reason, according to this example, the piezoelectric element  106  can be allowed to contact with the thin film  108  on a wide area suitably. As a result, the piezoelectric element  106  can be displaced also into a shape along the shape of the ink chamber  104 . For this reason, ink droplets can be discharged more stably also from this viewpoint. 
     The above has described only the displacement of the piezoelectric element  106  at the timing of discharging the ink droplets  202  for convenience of the description. In the actual print operation, however, it is considered that before the timing of the discharge of the ink droplets  202 , the piezoelectric element  106  is displaced to an opposite direction so as to supply a predetermined amount of ink into the ink chamber  104 . In this case, the piezoelectric element  106  performs the first displacement such that the center is deformed to the direction opposite to the nozzle  102  according to a change in the drive signal. Thereafter, the second displacement is performed that the center is curved to the direction of the nozzle. In this case, the ink is supplied to the ink chamber  104  from the ink tank  16  via the ink supply route  18  (see  FIGS. 1A and 1B ) according to the first displacement of the piezoelectric element  106 . Ink droplets are discharged from the nozzle  102  according to the second displacement of the piezoelectric element  106 . Therefore, such an operation is described in more detail below. 
       FIGS. 4A and 4B  are diagrams describing the first displacement that is displacement of the piezoelectric element  106  at timing when ink is supplied to the ink chamber  104 .  FIG. 4A  illustrates one example of a state of a cross section taken along alternate long and short dash line BB shown in  FIG. 2A  that the piezoelectric element  106  is curved in the first displacement.  FIG. 4B  illustrates one example of a state of the respective sections of the ink jet head  12  at the timing when the piezoelectric element  106  is curved in the first displacement of the piezoelectric element  106 . 
     In this example, the piezoelectric element  106  performs the first displacement such that the center is deformed to the direction opposite to the nozzle  102  according to a drive signal. In this case, that the center is curved toward the direction opposite to the nozzle  102  is that the piezoelectric element  106  is curved so that the center of the piezoelectric element  106  is separated from the nozzle  102  as shown in the drawings. As a result, the piezoelectric element  106  pulls up the thin film  108  to a direction separated from the nozzle  102 , so as to widen the ink chamber  104 . The ink is pulled into the ink chamber  104  according to this operation. For this reason, such a constitution enables the ink chamber  104  to be charged with the ink suitably before the discharge of ink droplets from the nozzle  102 . 
     In this operation, to pull the ink into the ink chamber  104  means pulling the ink into the ink chamber  104  from the ink tank  16  (see  FIGS. 1A and 1B ) via the ink supply route  18  (see  FIGS. 1A and 1B ). The ink can be pulled by utilizing ink supply pressure from the ink supply route  18  to the ink chamber  104 . In this example, the piezoelectric element  106  performs the first displacement by a preset displacement magnitude according to a drive signal, and the ink of the preset capacity is pulled into the ink chamber  104 . 
     In this case, the first displacement of the piezoelectric element  106  allows the ink to flow into the ink chamber  104 , so that the capacity in the ink chamber  104  becomes larger than the initial capacity before the displacement of the piezoelectric element  106 . For this reason, when the proportion V1/V0 between the inner volume of the ink chamber  104  and the capacity of the ink droplets  202  is considered, the inner volume of the ink chamber  104  in the state that the piezoelectric element  106  performs the first displacement may be considered as inner volume V0 of the ink chamber  104 . 
     After the first displacement, the piezoelectric element  106  performs the second displacement by which the center is curved toward the direction of the nozzle. The second displacement is the displacement of the piezoelectric element  106  described with reference to  FIGS. 3A to 3C . As a result, the piezoelectric element  106  allows most of the ink in the ink chamber  104  to be discharged from the nozzle  102 . It is preferable that the piezoelectric element  106  allows all the ink in the ink chamber  104  to be discharged from the nozzle  102 . 
     In this example, the displacement magnitude of the first displacement is controlled, so that the capacity of the ink to be introduced into the ink chamber  104  before the discharge can be suitably controlled. The second displacement of the piezoelectric element  106  to be performed later enables the ink pulled into the ink chamber  104  to be suitably discharged from the nozzle  102 . For this reason, the desired capacity of ink droplets can be discharged from the nozzle  102  suitably with high accuracy. 
     In the constitution of this example, the second displacement of the piezoelectric element  106  enables most of the ink in the ink chamber  104  to be pushed out from the nozzle  102 . In this case, ink droplets can be discharged from the nozzle  102  at the discharge speed according to a displacement speed in the second displacement. For this reason, the discharge speed of ink droplets can be suitably controlled into a desired speed with high accuracy by adjusting the displacement speed of the piezoelectric element  106  in the second displacement regardless of the capacity of ink droplets. Therefore, according to this example, printing can be suitably performed with higher accuracy. 
     In the second displacement of the piezoelectric element  106 , it is desirable that the displacement speed is sufficiently heightened in order to sufficiently heighten the discharge speed of ink droplets. On the other hand, in the first displacement of the piezoelectric element  106  that is performed in order to pull ink into the ink chamber  104 , it is desirable that the displacement speed is not unnecessarily heightened from viewpoints that ink is suitably pulled into the ink chamber  104  at an inflow velocity according to the supply pressure of ink and unnecessary disturbance that occurs in the ink in the ink chamber  104  is prevented. For this reason, it is considered that the displacement speed of the piezoelectric element  106  in the first displacement is set to be smaller than the displacement speed in the second displacement. In this case, the displacement speed of the piezoelectric element  106  means a progressing amount of the curve of the piezoelectric element  106  per predetermined unit time. 
     It is considered that a push-pull method is used as a method for adjusting the capacity of ink droplets to desired capacity that is different from the method of this example. As described above, however, when the ink droplets are discharged by the push-pull method, since the size of the ink droplets is determined according to the balance of a plurality of forces such as the force for pushing out ink from the nozzle and a force for pulling back the ink into the nozzle, it is difficult to uniform the size of the ink droplets accurately. Further, when small capacity of ink droplets is discharged, it is difficult to heighten the discharge speed of the ink droplets. 
     On the contrary, with the constitution of this example where most of the ink in the ink chamber  104  is discharged from the nozzle  102 , the constant capacity of the ink droplets  202  can be suitably discharged. For this reason, a variation in the capacity of the ink droplets  202  can be repressed suitably and independently from the speed of the ink droplets. Also when the capacity of the ink droplets is mall, the discharge speed can be suitably heightened. 
     As described above, it is preferable that all the ink in the ink chamber  104  is discharged from the nozzle  102  in the second displacement of the piezoelectric element  106 . Such a constitution enables a constant capacity of ink droplets to be suitably discharged with higher accuracy. 
     However, when the ink once pushed out of the nozzle  102  is not pulled back into the nozzle  102  and most of the ink in the ink chamber  104  is discharged as ink droplets from the nozzle  102 , the same effect can be produced although not all the ink in the ink chamber  104  is discharged. For example, it is considered that ink, which is within a range of 70% or more (for example, 70% to 140%) of the inner volume of the ink chamber  104  in the initial state where the piezoelectric element  106  is not displaced, is discharged from the nozzle  102 . The initial state of the piezoelectric element  106  means a state that a voltage is not applied to the piezoelectric element  106 . Such a constitution also enables a constant capacity of ink droplets to be suitably discharged regardless of the balance of a plurality of forces such as the force for pushing out ink from the nozzle  102  and the force for pulling back the ink into the nozzle. 
     Further, as described above, the displacement magnitude of the piezoelectric element  106  to the side opposite to the nozzle  102  is controlled so that the capacity of ink to be introduced into the ink chamber  104  before discharge can be suitably controlled. Thereafter, most of the ink in the ink chamber  104  is discharged from the nozzle  102  so that the desired capacity of ink droplets can be suitably discharged with high accuracy. For this reason, it is considered that the capacity of ink droplets to be discharged from the nozzle  102  is changed at a plurality of stages, and multi-gradation printing is performed in the print device  10  of this example by using this characteristic. 
       FIGS. 5A and 5B  are diagrams describing a case where the capacity of the ink droplets is variable at plural stages.  FIG. 5A  illustrates one example of an operation for varying the capacity of the ink droplets at the plural stages.  FIG. 5B  illustrates one example of ink droplets  202   s ,  202   m  and  202   l  with plural kinds of capacities. 
     When the capacity of ink droplets is variable at plural stages, a constitution in which plural kinds of drive signals for making displacement magnitude in the first displacement different can be output is used as the drive signal output section  14  (see  FIGS. 1A and 1B ). A drive signal to be supplied to each of the piezoelectric elements  106  for allowing each of the nozzles  102  to discharge ink droplets is selected according to the capacity of ink droplets to be discharged from each of the nozzles  102  in the ink jet head  12 . 
     In this case, the piezoelectric element  106  performs the first displacement by the displacement magnitude according to any drive signal in the plural kinds of drive signals to be supplied. As a result, ink is pulled into the ink chamber  104  according to the displacement magnitude in the first displacement. The second displacement for discharging ink droplets from the nozzle  102  is performed thereafter, so that most of the ink in the ink chamber  104  is discharged from the nozzle  102 . In this case, it is preferable that all the ink in the ink chamber  104  is discharged from the nozzle  102 . 
     Such a constitution enables the capacity of ink droplets to be discharged from the nozzle  102  to vary suitably according to the amount of the ink pulled into the ink chamber  104 . As a result, various capacities of ink droplets can be discharged from the nozzle  102  according to the plural kinds of drive signals. For this reason, such a constitution enables the multi-gradation printing to be suitably performed. 
     As to the plural kinds of drive signals, the displacement magnitude of the piezoelectric element  106  in the second displacement may be uniform. The displacement magnitude of the piezoelectric element  106  in the second displacement is displacement magnitude that is compared with the displacement magnitude in the initial state that the piezoelectric element  106  is not displaced. 
     More concretely, as shown in  FIG. 5B , when the capacity of ink droplets is variable at plural stages including three stages of the ink droplets  202   s  with small capacity, the ink droplets  202   m  with middle capacity, and the ink droplets  202   l  with large capacity, the drive signal output section  14  outputs a plurality of drive signals corresponding to the ink droplets  202   s ,  202   m  and  202   l . When the drive signal corresponding to the ink droplets  202   s  is received at timing before discharge of ink droplets, the piezoelectric element  106  is displaced to the side opposite to the nozzle  102  by small displacement magnitude as an arrow indicated by Small in  FIG. 5A  in the first displacement. 
     When the drive signal corresponding to the ink droplets  202   m  is received, the piezoelectric element  106  is displaced to the side opposite to the nozzle  102  by middle displacement magnitude as an arrow indicated by Middle in the first displacement. Further, when the drive signal corresponding to the ink droplets  202   l  is received, the piezoelectric element  106  is displaced to the side opposite to the nozzle  102  by large displacement magnitude as an arrow indicated by Large in the first displacement. Thereafter, the piezoelectric element  106  performs the second displacement for the displacement toward the nozzle  102 , so as to discharge the respective capacities of the ink droplets  202   s ,  202   m , and  202   l  from the nozzle  102 . 
     Such a constitution enables the capacity of ink droplets to be discharged from the nozzle  102  according to the plural kinds of drive signals to vary suitably at plural stages. As a result, ink dots of the plural kinds of sizes can be formed on a medium. Further, in this case, the constitution where most of the ink in the ink chamber  104  is discharged from the nozzle  102  can repress a variation in the capacity of ink droplets suitably. For this reason, such a constitution enables gradation printing using the ink dots of plural kinds of sizes suitably with high accuracy. 
     It is considered that the push-pull method can be used as the method for making the capacity of ink droplets to be discharged from the nozzle variable at plural stages. In this case, however, the discharge speed of ink droplets might vary according to the variation in the capacity of the ink droplets. As a result, it is considered that an error occurs in a striking position of ink droplets due to the variation in the capacity of the ink droplets. More concretely, like this example, the main scanning operation is performed so that printing is performed, the striking position of ink droplets changes according to the discharge speed of ink droplets. For this reason, when the discharge speed changes according to the ink capacity, it might be difficult to control the striking position with high accuracy. 
     On the contrary, in the constitution described with reference to  FIGS. 5A and 5B , since most of the ink in the ink chamber  104  is discharged from the nozzle  102 , as described with reference to  FIGS. 3 and 4 , the capacity of ink droplets and the discharge speed of ink droplets can be controlled independently. As a result, a variation in the discharge speed of ink droplets that is caused by the variation in the capacity of ink droplets can be repressed suitably. As a result, printing can be performed more suitably with higher accuracy. 
     The above has described one example of the preferred constitution of the ink jet head  12 . However, the concrete constitution of the ink jet head  12  is not limited to the above constitution, and various modifications can be made. Therefore, a modified example of the constitution of the ink jet head  12  is described below. 
       FIGS. 6A and 6B  illustrate one example of the constitution around the nozzle  102  in a modified example of the constitution of the ink jet head  12 . The components of the constitution in  FIGS. 6A and 6B  that are denoted by the same reference numerals as those in  FIGS. 1 to 5  have characteristics that are the same as or similar to those of the constitution in  FIGS. 1 to 5  except for the following description. 
       FIG. 6A  illustrates a first modified example of the constitution of the ink jet head  12 . As described above, it is preferable that when ink droplets are discharged, all the ink in the ink chamber  104  is discharged from the nozzle  102 . In order to achieve such a constitution, it is preferable that the thin film  108  is stuck on the bottom surface of the ink chamber  104  as firmly as possible at the time of discharge. 
     It is considered that the thin film  108  having a convex section  122  as shown in  FIG. 6A  concretely is used as a constitution where the thin film  108  is easily stuck on the bottom surface of the ink chamber  104 . In this case, the convex section  122  is a convex portion having a shape according to the shape of the bottom surface of the ink chamber  104 , and is provided on the surface of the thin film  108  opposed to the nozzle  102 . Such a constitution enables the thin film  108  to be firmly stuck on the bottom surface of the ink chamber  104  more suitably at the time of discharging ink droplets. 
       FIG. 6B  illustrates a second modified example of the constitution of the ink jet head  12 . As to the shape of the bottom surface of the ink chamber  104 , a portion that contacts with the thin film  108  may be flat. It is particularly preferable that a peripheral portion of the hole connected to the nozzle  102  in the portion contacting with the thin film  108  is flat. Such a constitution also enables the thin film  108  to be firmly stuck on the bottom surface of the ink chamber  104  more suitably at the time of discharging ink droplets. 
     Further, the nozzle plate  150  may be formed by a plurality of members in the ink jet head  12 . In the constitution shown in  FIG. 6B , the nozzle plate  150  is composed of a first member  152  and a second member  154  that form the plurality of members. The first member  152  and the second member  154  are stuck in an overlapping manner so as to be a plate-shaped member composing the nozzle plate  150 . Each of the first member  152  and the second member  154  is formed with holes and cavities related to the plurality of nozzles  102  and the plurality of ink chambers  104  in the ink jet head  12 . 
     In such a constitution, a part of the upper surface of the second member  154  is used as a part of the bottom surface of the ink chamber  104  so that the depth of the ink chamber  104  can be set suitably with high accuracy as shown in  FIG. 6B . As a result, the inner volume of the ink chamber  104  can be set suitably with high accuracy. Further, the bottom surface of the ink chamber  104  is easily made to be flat. For this reason, such a constitution enables the ink chamber  104  having a desired shape to be formed more suitably. As a result, the capacity of ink droplets can be controlled suitably with higher accuracy. 
     The part of the concrete constitution of the ink jet head  12  other than the modified example can be used. For example, as to the provision of the piezoelectric element  106  onto the thin film  108 , the piezoelectric element  106  is not directly disposed on the thin film  108 , and another member may be provided between the thin film  108  and the piezoelectric element  106 . An elastic member may be disposed between the thin film  108  and the piezoelectric element  106  if necessary. Such a constitution enables the curve of the piezoelectric element  106  to be adjusted more suitably. 
     The above has described the embodiment of the present disclosure, but the technical scope of the present disclosure is not limited to the scope described in the embodiment. The person skilled in the art understands that the embodiment can be variously modified and improved. It is clarified by description in What Is Claimed Is that the modified or improved mode is included in the technical scope of the present disclosure. 
     The present disclosure can be suitably used in print devices.