Patent Publication Number: US-7914116-B2

Title: Droplet discharge head, manufacturing method thereof, and droplet discharge apparatus

Description:
BACKGROUND 
     1. Technical Field 
     The present invention relates to a droplet discharge head, a manufacturing method thereof, and a droplet discharge apparatus. 
     2. Related Art 
     There has been known an inkjet head formed by boding a nozzle plate to the top surface of a head body using an adhesive such as an epoxy resin (for example, see JP-A-07-223316). Also, there has been disclosed an inkjet recording apparatus in which an oxide film or a titanium nitride film is formed as a liquid-resistant thin film (ink-resistant thin film) on the wall surface of a liquid flow path with a silicon substrate used as a liquid chamber forming member so as to prevent eluted silicon from blending into the ink as well as so as to prevent warpage from occurring in the entire liquid chamber forming member due to internal stress of the liquid-resistant thin film (for example, see JP-A-2003-276192). 
     In the above-described related-art droplet discharge apparatuses, an adhesive such as an epoxy adhesive or an acrylic adhesive is used to bond the nozzle plate, liquid chamber forming member, and the like to the droplet discharge head. Therefore, when the droplet discharge head is filled with a discharge liquid such as solution ink such as N-methyl-2-pyrrolidone (NMP), butyl cellosolve, or y-butyrolactone, or alkali ink or when the discharge liquid is discharged from the droplet discharge head, the discharge liquid penetrates the bonding sections so that the adhesive swells. This reduces the durability of the droplet discharge head and therefore reduces the life thereof. Thus, the droplet discharge head must be replaced frequently. Also, in order to prevent the discharge liquid from being contaminated due to the solution of the adhesive, the types of the solvent for the discharge liquid are limited. 
     SUMMARY 
     An advantage of the invention is to provide a droplet discharge head, a manufacturing method thereof, and a droplet discharge apparatus for preventing penetration of a discharge liquid into a bonding section so that the durability of the droplet discharge head is improved and so that the types of the discharge liquid are not limited. 
     According to a first aspect of the invention, a droplet discharge head includes a nozzle substrate having a nozzle opening for discharging a liquid as a droplet; a flow path substrate having a flow path for the liquid, the flow path communicating with the nozzle opening; and a diaphragm constituting a wall surface of the flow path. The nozzle substrate, the flow path substrate, and the diaphragm are bonded together in layers using an adhesive, and a liquid-resistant film resistant to the liquid is continuously formed on surfaces of the nozzle substrate, the flow path substrate, and the diaphragm, the surfaces being in contact with the liquid. 
     According to this configuration, the bonding section between the nozzle substrate and flow path substrate and the bonding section between the flow path substrate and diaphragm are covered with the continuing liquid-resistant film in the flow path for the liquid so that the liquid in the flow path does not make contact with the bonding sections. This prevents the liquid in the flow path from penetrating gaps in the bonding sections or prevents the liquid from making contact with the adhesive exposed on the portions of the bonding sections facing the flow path. This prevents the liquid from penetrating the adhesive to cause the adhesive to swell. Thus, the durability of the droplet discharge head is improved. Also, since the adhesive is isolated from the liquid, the liquid is prevented from being contaminated due to the solution of the adhesive and the types of a dischargeable liquid are not limited by the material of the adhesive. 
     The droplet discharge head according to the first aspect of the invention preferably further includes: a piezoelectric element for changing, via the diaphragm, a volume of a pressure chamber provided in the flow path; and a casing holding the piezoelectric element and having a liquid supply path for supplying the liquid to the flow path. The casing is preferably bonded to the diaphragm using an adhesive, and a surface of the casing facing the liquid supply path is preferably covered with the liquid-resistant film continuously formed from the surface of the diaphragm in contact with the liquid. 
     According to this configuration, the bonding section between the casing and diaphragm is covered with the liquid-resistant film in the flow supply path so that the liquid in the flow path does not make contact with the bonding section. This prevents the liquid in the flow supply path from penetrating a gap in the bonding section or prevents the liquid from making contact with the adhesive exposed on the portion of the bonding section facing the flow path. This prevents the liquid from penetrating the bonding section to cause the adhesive to swell. Thus, the durability of the droplet discharge head is improved. Also, since the adhesive is isolated from the liquid, the liquid is prevented from being contaminated due to the solution of the adhesive and the types of a dischargeable liquid are not limited by the material of the adhesive. 
     In the droplet discharge head according to the first aspect of the invention, the liquid-resistant film is preferably formed of a lyophilic material. 
     According to this configuration, the wettability of internal portions of the droplet discharge head facing the liquid is improved so that the menisci of droplets of the liquid are arranged when the droplets are discharged from the nozzles. Thus, the droplet discharge performance is improved. 
     In the droplet discharge head according to the first aspect of the invention, the liquid-resistant film is preferably formed of a liquid-repellent material. 
     According to this configuration, the characteristic of the liquid-resistant film for isolating the liquid from the bonding section is improved so that the thickness of the liquid-resistant film is reduced. 
     In the droplet discharge head according to the first aspect of the invention, a thickness of the liquid-resistant film is preferably equal to or larger than a thickness of one molecule layer and equal to or less than 1 μm. 
     According to this configuration, the characteristic of the liquid-resistant film for isolating the liquid from the bonding section is sufficiently exhibited. Also, the liquid-resistant film is prevented from affecting the discharge of the liquid. 
     According to a second aspect of the invention, a method for manufacturing a droplet discharge head includes: (a) bonding together a nozzle substrate, a flow path substrate, and a diaphragm in layers using an adhesive, the nozzle substrate having a nozzle opening for discharging a liquid as a droplet, the flow path substrate having a flow path for the liquid, the flow path communicating with the nozzle opening, the diaphragm constituting a wall surface of the flow path; (b) filling the flow path with a material liquid for a liquid-resistant film; and (c) discharging the material liquid from the flow path and heating and then drying the material liquid adhering to surfaces of the nozzle substrate, the flow path substrate, and the diaphragm so that a liquid-resistant film resistant to the liquid-is continuously formed on the surfaces, the surfaces being in contact with the liquid. 
     According to this manufacturing method, the bonding section between the nozzle substrate and flow path substrate and the bonding between the flow path substrate and diaphragm are covered with the continuing liquid-resistant film. Thus, even if the flow path is filled with the liquid when droplets are discharged, the liquid in the flow path does not make contact with the bonding sections. This prevents the liquid in the flow path from penetrating gaps in the bonding sections or prevents the liquid from making contact with the adhesive exposed on the portions of the bonding sections facing the flow path. This prevents the liquid from penetrating the adhesive to cause the adhesive to swell. Thus, the durability of the droplet discharge head is improved. Also, since the adhesive is isolated from the liquid, the liquid is prevented from being contaminated due to the solution of the adhesive and the types of a dischargeable liquid are not limited by the material of the adhesive. 
     In the method for manufacturing a droplet discharge head according to the second aspect of the invention, in step (a), a casing holding a piezoelectric element and having a liquid supply path for supplying the liquid to the flow path is preferably bonded to the diaphragm using an adhesive, the piezoelectric element changing, via the diaphragm, a volume of a pressure chamber provided in the flow path. In step (b), the flow path and the liquid supply path are preferably filled with the material liquid. In step (c), the material liquid adhering to a surface of the casing facing the liquid supply path is preferably heated and then dried so that the liquid-resistant film continuing from a surface of the diaphragm facing the flow path to the surface of the casing facing the liquid supply path is formed. 
     According to this manufacturing method, the bonding section between the casing and diaphragm is covered with the liquid-resistant film. Thus, even if the flow path is filled with the liquid when droplets are discharged, the liquid in the flow path does not make contact with the bonding section. This prevents the liquid in the flow path from penetrating a gap in the bonding section or prevents the liquid from making contact with the adhesive exposed on the portion of the bonding section facing the flow path. This prevents the liquid from penetrating the bonding section to cause the adhesive to swell. Thus, the durability of the droplet discharge head is improved. Also, since the adhesive is isolated from the liquid, the liquid is prevented from being contaminated due to the solution of the adhesive and the types of a discharge liquid are not limited by the material of the adhesive. 
     In the method for manufacturing a droplet discharge head according to the second aspect of the invention, in step (b), the material liquid is preferably a material liquid containing Si. 
     According to this manufacturing method, the liquid-resistant film formed in step (c) becomes, for example, a lyophilic, liquid-resistant film such as SiO x . Thus, the wettability of internal portions of the droplet discharge head facing the liquid is improved so that the menisci of droplets of the liquid are arranged when the droplets are discharged from the nozzles. As a result, the droplet discharge performance is improved. 
     In the method for manufacturing a droplet discharge head according to the second aspect of the invention, in step (b), the material liquid is preferably any one of a fluoro material liquid, a silicone material liquid, and an organopolysiloxane material liquid containing fluorine. 
     According to this manufacturing method, the liquid-resistant film formed in step (c) becomes, for example, a liquid-repellent, liquid-resistant film. Thus, the characteristic of the liquid-resistant film for isolating the liquid from the bonding section is improved so that the liquid-resistant film is thinned. 
     A droplet discharge apparatus according to a third aspect of the invention includes the droplet discharge head according to the first aspect of the invention. 
     Thus, the droplet discharge apparatus is provided that prevents the discharge liquid from penetrating the bonding sections of the droplet discharge head, improves the durability of the droplet discharge head, and does not limit the types of the discharge liquid. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be described with reference to the accompanying drawings, wherein like reference numerals designate like elements. 
         FIG. 1  is a schematic view showing an overall configuration of a droplet discharge apparatus according to an embodiment of the invention. 
         FIG. 2  is a sectional view showing a configuration of a droplet discharge head according to this embodiment. 
         FIG. 3  is a sectional view of a main part of the droplet discharge head according to this embodiment. 
         FIG. 4  is a schematic view showing an outline configuration of the droplet discharge apparatus according to the embodiment of the invention. 
         FIGS. 5A to 5C  are enlarged sectional views showing a process of manufacturing the droplet discharge head according to this embodiment. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Now, an embodiment of the invention will be described with reference to the accompanying drawings. 
       FIG. 1  is a schematic view showing an outline configuration of a droplet discharge apparatus  10 . As shown in  FIG. 1 , the droplet discharge apparatus (liquid spray apparatus)  10  includes a base  31 , a substrate carrier  32 , a head carrier  33 , a droplet discharge head  34 , an ink supply unit  35 , and a controller  40 . The substrate carrier  32  and head carrier  33  are provided on the base  31 . 
     The droplet discharge apparatus  10  also includes a cleaning unit  53  and a capping unit  55 . 
     The substrate carrier  32  includes guide rails  36  disposed on the base  31  along the Y-axis. The substrate carrier  32  moves a slider  37  along the guide rails  36 , for example, using a linear motor (now shown). 
     A stage  39  for positioning and holding the substrate P is fixed to the slider  37 . That is, the stage  39  includes a publicly known absorption holder (not shown) and holds the substrate P on the stage  39  in an absorptive manner by operating the absorption holder. The substrate P is positioned accurately in a predetermined position on the state  39 , for example, using a positioning pin (not shown) of the stage  39  and is held there. 
     The head carrier  33  includes a pair of stands  33   a  set up on a rear portion of the base  31  and a track  33   b  provided on the stands  33   a . In the head carrier  33 , the track  33   b  is disposed along the X axis direction, that is, along a direction orthogonal to the Y axis direction, along which the guide rails of the substrate carrier  32  are disposed. The track  33   b  includes a holding plate  33   c  provided between the stands  33   a  and a pair of guide rails  33   d  provided on the holding plate  33   c . The track  33   b  holds a carriage  42  provided with the droplet discharge head  34  in such a manner that the carriage  42  is movable in the length direction of the guide rails  33   d . The carriage  42  travels on the guide rails  33   d  according to the operation of a linear motor (not shown) and the like so that the droplet discharge head  34  moves in the X axis direction. 
     The carriage  42  is configured so that it is movable, for example, in units of 1 μm in the length direction of the guide rails  33   d , that is, in the X axis direction. Such movement of the carriage  42  is controlled by the controller  40  including a computer and the like. 
     The controller  40  detects and stores information about the positions of the droplet discharge head  34 , that is, the positions (X coordinates) of the droplet discharge head  34  on the guide rails  33   d  and the positions (X coordinates) of the nozzles at that time 
     The droplet discharge head  34  is mounted on the carriage  42  with a mounting unit  43  therebetween in such a manner that it is rotatable. The mounting unit  43  is provided with a motor  44 , to which a supporting axis (not shown) of the droplet discharge head  34  is connected. According to this configuration, the droplet discharge head  34  is rotatable in the circumference direction thereof. The motor is also coupled to the controller  40  so that the rotation of the droplet discharge head  34  in the circumference direction thereof is controlled by the controller  40 . 
     The ink supply unit  35  includes an ink tank  45  that is filled with ink L and an ink supply tube  46  for sending the ink L from the ink tank  45  to the droplet discharge head  34 . 
     The cleaning unit  53  is allowed to clean such as the nozzles of the droplet discharge head  34  when the substrate P is being manufactured, or periodically or as necessary when the droplet discharge head  34  is on standby. Note that when the ink L is discharged onto the substrate P, the cleaning unit  53  is held in a position where the cleaning unit  53  does not interfere with the operation of the droplet discharge head  34 . 
     The capping unit  55  includes a cap  47 , a liquid suction tube  48 , and a suction pump  51  connected to the liquid suction tube  48 . In order to prevent a nozzle opening surface  143   a  (see  FIG. 3 ) of the droplet discharge head  34  from being dried, the capping unit  55  covers the nozzle opening surface  143   a  with the cap  47  when the droplet discharge head  34  is discharging the ink L onto the substrate P or is on standby. 
     Also, the capping unit  55  has a function of initially filling the droplet discharge head  34  with the ink L. When the capping unit  55  performs the initial filling, it also covers the nozzle opening surface  143   a  with the cap  47 . 
     The cap  47  moves vertically along a guide (not shown) or the like provided in the droplet discharge head  34  so that it abuts on and adhere to the nozzle opening surface  143   a  of the droplet discharge head  34  (see  FIG. 4 ). The cap  47  is made of silicone, fluoroplastics, or the like and is coupled to the suction pump  51  for sucking the ink L, via the liquid suction tube  48 . 
     The suction pump  51  is provided with a control mechanism (not shown) including such as a pressure control valve for controlling the degree of pressure reduction for sucking the ink L. The pressure control valve is coupled to the controller  40  so that the increase or reduction of pressure is controlled. When the ink L is discharged onto the substrate P, the capping unit  55  is held in a position where the capping unit  55  does not interfere with the operation of the droplet discharge head  34 . 
       FIG. 2  is a sectional view showing a configuration of the droplet discharge head  34 .  FIG. 3  is a sectional view of a main part of the droplet discharge head  34 . 
     The droplet discharge head  34  according to this embodiment mainly includes an introducer needle unit  117 , a head case  118  (casing), a flow path unit  119 , and an actuator unit  120 . 
     Two ink introducer needles  122  are mounted on the upper surface of the introducer needle unit  117  side-by-side with filters  121  therebetween. The ink introducer needles  122  are loaded with sub-tanks  102 . The introducer needle unit  117  has ink introduction paths  123  corresponding to the ink introducer needles  122 . 
     The upper ends of the ink introduction paths  123  communicate with the ink introducer needles  122  via the filters  121 . The lower ends thereof communicate with case flow paths  125  (liquid supply paths) formed in the head case  118  via packing  128 . 
     The filters  121  are provided to eliminate foreign matters included in the ink L. The filters  121  are formed of, e.g., stainless steel and in the form of meshes. 
     The sub-tanks  102  are formed of a resin material such as polypropylene. The sub-tanks  102  have recesses serving as the ink chambers  127 . The ink chambers  127  are defined by attaching elastic sheets  126  to the opening surfaces of the recesses. 
     Needle connectors  128  into which the ink introducer needles  122  are inserted are provided below the sub-tanks  102  in a downwardly extending manner. The ink chambers  127  in the sub-tanks  102  each take the shape of a shallow mortar. The upstream openings of the connection flow paths  129  communicating with the needle connectors  128  face positions slightly below the centers in the vertical direction on sides of the ink chambers  127 . Tank filters  130  for filtering the ink L are attached to the upstream openings. 
     Sealing members  131  into which the ink introducer needles  122  are inserted are packed fluid-tight in the internal spaces of the needle connectors  128 . As shown in  FIG. 4 , an extending unit  127  having a communication groove  132   a  communicating with the ink chamber  127  is formed in the sub-tank  102 . An ink inlet  133  is provided in a protruding manner on the upper surface of the extending unit  132 . 
     The ink supply tube  46  for supplying the ink L stored in the ink tank  45  of the ink supply unit  35  is connected to the ink inlet  133 . Thus, the ink L passing through the ink supply tube  46  flows into the ink chamber  127  via the ink inlet  133  and communication groove  132   a.    
     The above-described elastic sheets  126  are deformable in the direction in which the ink chambers  127  shrink and in the direction in which the ink chambers  127  swell. A damper function obtained due to the deformation of the elastic sheets  126  absorbs variations in pressure of the ink L. That is, due to the operation of the elastic sheets  126 , the sub-tanks  102  serve as pressure dampers. Thus, the ink L is supplied to the droplet discharge head  34  with pressure variations absorbed in the sub-tanks  102 . 
     The head case  118  is a hollow box-shaped member made of a synthetic resin. The flow path unit  119  is bonded to the lower surface of the head case  118  using an adhesive. Actuator units  120  are contained in containing spaces  137  internally formed in the head case  118 . The introducer needle unit  117  is mounted on the upper surface of the head case  118  opposed to the flow path unit  119  with the packing  124  therebetween. 
     The head case  118  has case flow paths  125  passing through in the height direction. The upper ends of the case flow paths  125  communicate with the ink introduction paths  123  of the introducer needle unit  117  via the packing  124 . 
     The lower ends of the case flow paths  125  communicate with a common ink chamber  144  in the flow path unit  119 . Thus, the ink L introduced by the ink introducer needles  122  is supplied to the common ink chamber  144  via the ink introduction paths  123  and case flow paths  125 . 
     As shown in  FIG. 3 , the actuator unit  120  contained in the containing space  137  of the head case  118  includes multiple piezoelectric vibrators  138  provided in rows in the form of comb-teeth, a fixing plate  139  to which the piezoelectric vibrators  138  are bonded, and a flexible cable  140  that is a wiring member for providing drive signals from the controller  40  to the piezoelectric vibrators  138 . The fixed end of each piezoelectric vibrator  138  is bonded to the fixing plate  139  and the free end thereof protrudes from the top surface of the fixing plate  139 . That is, each piezoelectric vibrator  138  is mounted on the fixing plate in a so-called “cantilever” manner. 
     The fixing plate  139  supporting the piezoelectric vibrators  138  is made of, e.g., stainless steel with a thickness of approximately 1 mm. The actuator unit  120  is contained and fixed in the containing space  137  by attaching the back of the fixing plate  139  to a wall surface defining the containing space  137  in the head case  118 . 
     The flow path unit  119  is manufactured by bonding together flow path unit members, that is, a diaphragm  141 , a flow path substrate  142 , and a nozzle substrate  143  in layers using an adhesive to integrate these members. These flow path unit members are members for forming a string of ink flow path R from the common ink chamber  144  through the ink inlet  145  and a pressure chamber  146  to the nozzles  147 . 
     The pressure chamber  146  is formed as a chamber elongated in a direction orthogonal to the direction in which the nozzles  147  are arranged in rows (nozzle row direction). 
     The common ink chamber  144  is a chamber that communicates with the case flow path  125  and receives the ink L from the ink introducer needle  122 . The ink L received by the common ink chamber  144  is distributed to the pressure chambers  146  via the ink inlet  145 . 
     In this embodiment, a liquid-resistant film C that is resistant to the ink L is continuously formed on a surface  143   r , a surface  142   r , and a surface  141   r  of the nozzle substrate  143 , flow path substrate  142 , and diaphragm  141 , respectively, each facing the ink flow path R, which are surfaces of these members in contact with the ink L. Also, a surface  118   a  of the head case  118  facing the case flow path  125  is covered with the liquid-resistant film C formed continuously from the surface  141   r  of the diaphragm  141  facing the ink flow path R. 
     The liquid-resistant film C is a lyophilic film formed of an Si oxide such as SiO 2 . The liquid-resistant film C is formed with a thickness equal to or larger than the thickness of one molecule layer and equal to or less than 1 μm. 
     The nozzle substrate  143  disposed on the bottom of the flow path unit  119  is a thin metal plate material in which the multiple nozzles  147  are provided in rows in an open manner at a pitch (e.g., 180 dpi) corresponding to the dot formation density. The nozzle substrate  143  according to this embodiment is formed of a plate material made of stainless steel. In this embodiment, a total of 22 rows of the nozzles  147  (that is, nozzle rows) are provided in parallel so as to correspond to each sub-tank  102 . One nozzle row includes, for example, 180 units of nozzles  147 . 
     The flow path substrate  142  disposed between the nozzle substrate  143  and diaphragm  141  is a plate-shaped member in which ink flow paths, specifically, spaces serving as the common ink chamber  144 , ink inlet  145 , and pressure chamber  146  are defined and formed. 
     In this embodiment, the flow path substrate  142  is manufactured by subjecting a Si wafer as a crystalline substrate to anisotropic etching. The diaphragm  141  is a double-structured composite plate member manufactured by forming elastic films in layers on a metal supporting plate made of stainless steel or the like. An island  148  to which the top surface of the piezoelectric vibrator  138  is bonded is formed in a part of the diaphragm  141  corresponding to the pressure chamber  146  by eliminating a part of the supporting plate in the form of a ring by etching or the like. This island serves as a diaphragm unit. That is, the diaphragm  141  elastically deforms an elastic film around the island  148  according to the operation of the piezoelectric vibrator  138 . The diaphragm  141  also serves as a compliance unit  149  for sealing one opening surface of the flow path substrate  142 . Like the diaphragm unit, a part corresponding to the compliance unit  149  is an elastic film left by eliminating the supporting plate by etching or the like. 
     If a drive signal is provided to one of the piezoelectric vibrators  138  via the flexible cable  140  in the droplet discharge head  34 , the piezoelectric vibrator  138  shrinks or swells in the longitudinal direction thereof. Accordingly, the island  148  moves in the direction in which the island  148  comes close to the pressure chamber  146  or in the direction in which the island  148  goes away therefrom. Thus, the volume of the pressure chamber  146  is changed so that a variation occurs in pressure of the ink L in the pressure chamber  146 . Due to this pressure variation, the ink L is discharged as droplets from the nozzles  147 . 
     The ink L used in this embodiment is, for example, solvent ink such as N-methyl-2-pyrrolidone (NMP), butyl cellosolve, or y-butyrolactone, or alkali ink. 
     Next, the operation of this embodiment will be described. 
     As shown in  FIG. 3 , a portion of a bonding section A 1  between the nozzle substrate  143  and flow path substrate  142  facing the ink flow path R and a portion of a bonding section A 2  between the flow path substrate  142  and diaphragm  141  facing the ink flow path R are covered with the continuously formed liquid-resistant film C. Thus, the ink L is blocked by the liquid-resistant film C so that the ink L does not make contact with the bonding sections A 1  and A 2 . This prevents the ink L in the ink flow path R from penetrating gaps in the bonding sections A 1  and A 2  or prevents the ink from making contact with the adhesive exposed on portions of the bonding sections A 1  and A 2  facing the ink flow path R. This prevents the ink L from penetrating the adhesive on the portions of the bonding sections A 1  and A 2  to cause the adhesive to swell. This prevents the flow path substrate  142 , diaphragm  141 , and nozzle substrate  143  from being peeled away from each other. As a result, the durability of the flow path unit  119  and, therefore, that of the droplet discharge head  34  is improved. 
     Also, a part of a bonding section A 3  between the heads case  118  and diaphragm  141  is covered with the liquid-resistant film C so that the ink L in the case flow path  125  does not make contact with the bonding section A 3 . This prevents the ink L in the case flow path  125  from penetrating a gap in the bonding section A 3  or prevents the ink L from making contact with the adhesive exposed on a portion of the bonding section A 3  facing the case flow path  125 . This prevents the ink L from penetrating the bonding section A 3  to cause the adhesive to swell. Thus, the head case  118  and flow path unit  119  are prevented from being peeled away from each other. As a result, the durability of the droplet discharge head  34  is improved. 
     Also, the bonding sections A 1 , A 2 , and A 3  are isolated from the ink L by the liquid-resistant film C so that the adhesive used in the bonding sections A 1 , A 2 , and A 3  is prevented from making contact with the ink L. Thus, the ink L is prevented from being contaminated due to the solution of the adhesive. Therefore, the types of the ink L to be discharged are not limited by the material of the adhesive. 
     Also, the liquid-resistant film C is made of a lyophilic material such as SiO 2 ; therefore, the wettability of parts of the ink flow path R in contact with the ink L in the droplet discharge head  34  is improved. Thus, when the ink L is discharged as droplets from the nozzles  147 , the menisci of droplets are arranged. As a result, droplets of the ink L are discharged with improved performance. 
     Also, if the liquid-resistant film C is formed with a thickness equal to or larger than the thickness of one molecule layer and equal to or less than 1μ, the liquid-resistant film C sufficiently exhibits a liquid-resistant characteristic and an isolation characteristic with respect to the ink L. Also, the thickness of the liquid-resistant film C is sufficiently small; therefore, the film is prevented from affecting the discharge of the ink L. 
     As described above, according to the droplet discharge head  34  according to this embodiment, penetration of the ink L into the bonding sections A 1 , A 2 , and A 3  is prevented. Thus, the durability of the droplet discharge head  34  is improved and the types of the ink L are not limited by the material of the adhesive. Also, the droplet discharge apparatus  10  according to this embodiment includes the droplet discharge head  34 ; therefore, penetration of the ink L into the bonding sections A 1 , A 2 , and A 3  in the droplet discharge head  34  is prevented. Thus, the durability of the droplet discharge head  34  is improved and the types of the ink L are not limited by the material of the adhesive. 
     Method for Manufacturing Droplet Discharge Head 
     Next, a method for manufacturing the droplet discharge head  34  will be described with reference to  FIGS. 5A to 5C . In  FIGS. 5A to 5C , a process of manufacturing the liquid-resistant film C will be mainly described and the description of other processes will be omitted as appropriate. Processes other than the process of manufacturing the liquid-resistant film C may be publicly known processes. 
     First, the nozzle substrate  143 , flow path substrate  142 , and diaphragm  141  are bonded together in layers using an adhesive. The adhesive may be an epoxy adhesive, an acrylic adhesive, or the like. Next, the head case  118  is bonded to the diaphragm  141  using the adhesive (assembly step). 
     Next, as shown in  FIG. 5A , a material liquid B (material liquid for liquid-resistant film) for the liquid-resistant film C is injected from the case flow path  125  of the head case  118  with the nozzle  147  directed upward so that the case flow path  125  of the head case  118  and the ink flow path R of the flow path unit  119  are filled with the material liquid B (material liquid filling step). 
     As the material liquid B, a liquid that contains Si and becomes SiO x  after being baked, such as SiO 2  sol-gel, Si alkoxide, a silane coupling agent (HMDS), or a silanol compound, is used. The viscosity of the material liquid B is adjusted according to the thickness of the liquid-resistant film C to be formed. 
     Next, as shown in  FIG. 5B , the material liquid B is discharged from the case flow path  125  and ink flow path R. As a result, the material liquid B adheres to the surface  143   r ,  142   r , and  141   r  of the nozzle substrate  143 , flow path substrate  142 , and diaphragm  141 , respectively, each facing the ink flow path R and the surface  118   a  of the head case  118  facing the case flow path  125  with a predetermined thickness according to the viscosity of the material liquid B. In this state, the material liquid B is heated and then dried (liquid-resistant film forming process). 
     Thus, as shown in  FIG. 5C , the droplet discharge head  34  is manufactured in which the liquid-resistant film C resistant to the ink L is formed continuously on the surfaces  143   r ,  142   r , and  141   r  facing the ink flow path R and the surface  118   a  facing the case flow path  125 . 
     According to the method for manufacturing the droplet discharge head  34  according to this embodiment, the bonding section A 1  between the nozzle substrate  143  and flow path substrate  142  and the bonding section A 2  between the flow path substrate  142  and diaphragm  141  are covered with the liquid-resistant film C formed continuously on the surfaces  143   r ,  142   r , and  141   r . Therefore, even if the ink flow path R is filled with the ink L when droplets are discharged, the ink L in the ink flow path R is prevented from making contact with the bonding sections A 1  and A 2 . This prevents the ink L in the ink flow path R from penetrating the gaps in the bonding sections A 1  and A 2  or prevents the ink L from making contact with the adhesive exposed on the portions of the bonding sections A 1  and A 2  facing the ink flow path R. This prevents the ink L from penetrating the adhesive to cause the adhesive to swell. Thus, the droplet discharge head  34  is improved. 
     Also, the liquid-resistant film C is formed continuously from the surface  141   r  of the diaphragm  141  facing the ink flow path R to the surface  118   a  of the head case  118  facing the case flow path  125  so that the bonding section A 3  between the head case  118  and diaphragm  141  is covered with the liquid-resistant film C. Therefore, even if the case flow path  125  is filled with the ink L when droplets are discharged, the ink L in the case flow path  125  is prevented from making contact with the bonding section A 3 . This prevents the ink L in the case flow path  125  from penetrating a gap in the bonding section A 3  or prevents the ink L from making contact with the adhesive exposed on the portion of the bonding section A 3  facing the case flow path  125 . This prevents the ink L from penetrating the bonding section A 3  to cause the adhesive to swell. Thus, the durability of the droplet discharge head  34  is improved. 
     Also, the adhesive used in the bonding sections A 1 , A 2 , and A 3  is isolated from the ink L. Thus, the ink L is prevented from being contaminated due to the solution of the adhesive and the types of the ink L are not limited by the material of the adhesive. 
     Also, by using a liquid including Si as the material liquid B, the liquid-resistant film C is formed of a lyophilic material such as SiO x . This improves the wettability of the internal portions of the droplet discharge head  34  facing the ink L, as well as arranges the menisci of droplets of the ink L. Thus, droplets of the ink L are discharged with improved performance. 
     The invention is not limited to the above-described embodiment. For example, a fluoro material liquid, a silicone material liquid, or an organopolysiloxane material liquid containing fluorine may be used in the liquid-resistant film forming step. Thus, a liquid-resistant film formed in the liquid-resistant film forming step becomes a liquid-repellent, liquid-resistant film. By forming the liquid-resistant film using a liquid-repellent material, the characteristic of the liquid-resistant film for isolating the ink from the bonding sections is improved so that the liquid-resistant film is thinned. 
     The entire disclosure of Japanese Patent Application No. 2007-287011, filed Nov. 5, 2007 is expressly incorporated by reference herein.