Abstract:
A droplet discharging head comprises: a pressure chamber; a nozzle plate including a penetration part that couples with the pressure chamber and discharges a droplet; and a droplet guidance part having a tip positioned inside the penetration part. The tip of the droplet guidance part is free from touching an inside wall of the penetration part.

Description:
BACKGROUND 
       [0001]    1. Technical Field 
         [0002]    Several aspects of the present invention relate to a droplet discharging head and a method for manufacturing the same, and a droplet discharging device. 
         [0003]    2. Related Art 
         [0004]    A manufacturing method and its application have been proposed in which a fine pattern such as a metal wiring line is drawn by utilizing a droplet discharging technique employed in such as an inkjet printer superior in controlling a discharge amount and a drawing position. 
         [0005]    For example, JP-A-5-193144 proposes a method with a discharging head in which discharge parts having a conical shape is formed at a droplet discharging side of the discharging head. The head improves straight-flight stability of a droplet and reduces discharged amount variation of a droplet discharged from each discharge part. 
         [0006]    In the proposed droplet discharging head, however, it comes to be difficult to discharge a droplet correctly to a target position due to increased air resistance and the like if the droplet size is further reduced. Hence, it is hard to thoroughly secure the straight-flight stability of a droplet. 
       SUMMARY 
       [0007]    An advantage of the invention is to provide a droplet discharging head capable of stabilizing a droplet discharging direction, a method for manufacturing the droplet discharging head, and a droplet discharging device having the droplet discharging head. 
         [0008]    In the specification, a term “axisymmetric pattern” is defined as follows: when it is rotated around an axis, the pattern substantially coincides with the pattern before rotation at one or more angle within a rotation angle ranging from zero degrees to less than  360  degrees. It is interpreted that a cylindrical column has a pattern coincides at every angle. Here, the term “substantially” is defined as a case in which discharged direction, quantity, and velocity of a droplet discharged are within a predetermined error range. 
         [0009]    Additionally, a term “peaked shape” is defined as a sharp-pointed shape. A term “truncated cone shape” is defined as a shape achieved after removing a peaked shape of a conical shape. 
         [0010]    A droplet discharging head according to a first aspect of the invention includes a pressure chamber, a nozzle plate including a penetration part that couples with the pressure chamber and discharges a droplet, and a droplet guidance part having a tip positioned inside the penetration part. The tip of the droplet guidance part is free from touching an inside wall of the penetration part. 
         [0011]    The head can improve droplet discharge stability. 
         [0012]    In this case, the penetration part preferably includes a tapered shape part tapering toward a droplet discharging direction and a columnar shape part coupled with a small end of the tapered shape. 
         [0013]    The droplet guidance part, the tapered shape part, and the cylindrical columnar part can forcibly direct a droplet in a discharging direction. Thus, straight-flying stability of a droplet can be further improved. 
         [0014]    In this case, the tapered shape part preferably has a truncated cone shape part tapering toward the droplet discharging direction. The columnar shape part preferably has a cylindrical columnar shape coupled with a small end of the truncated cone shape part. The truncated cone shape part and the columnar shape part are preferably disposed coaxially or eccentrically. 
         [0015]    The highly symmetric pattern formed in the penetration part can forcibly direct a droplet in an axis direction when the axes are coaxially aligned and the droplet is discharged in the axis direction. Thus, controlling a droplet landing position can be improved. Although the axes are eccentrically disposed, the discharging direction is highly repeatable. As a result, fluctuation of the landing position can be suppressed. 
         [0016]    In this case, the penetration part preferably includes a first columnar shape part that is disposed to a first surface, which faces the pressure chamber, of the nozzle plate and has a first cross-sectional shape, and a second columnar shape part that is disposed to a discharging surface of the nozzle plate and has a second cross-sectional shape. 
         [0017]    The droplet guidance part is disposed inside the first columnar shape part to adjust a sectional area to manages the following problems: the volume difference between the first and second columnar shape parts, and occurrence and gathering of bubbles produced by a step at their connection part in a droplet discharging head formed by combining columnar shapes. The droplet guidance part can reduce the volume difference and improve discharge performance. 
         [0018]    In this case, the first columnar shape part is preferably a first cylindrical columnar shape having a first radius, and the second columnar shape part is preferably a second cylindrical columnar shape having a second radius smaller than the first radius. The first columnar shape part and the second columnar shape part are preferably disposed coaxially or eccentrically. 
         [0019]    The droplet discharging head formed with shapes having a highly symmetric pattern can improve the straight-flight stability of a droplet. Although the axes are eccentrically disposed, the discharging direction is highly repeatable. As a result, fluctuation of the landing position can be suppressed. 
         [0020]    In this case, the droplet guidance part preferably includes an axisymmetric pattern. 
         [0021]    Since the droplet guidance part has the axisymmetric pattern, a droplet is discharged symmetrically with respect to the axis. As a result, a droplet landing position can be controlled with high accuracy. 
         [0022]    In this case, the tip of the droplet guidance part is preferably positioned within a thickness of the nozzle plate. 
         [0023]    The head can reduce the fluctuation of a droplet discharging direction and adjust a volume change in the penetration part. As a result, discharge stability can be improved. 
         [0024]    In this case, the droplet guidance part is preferably disposed within the thickness of the nozzle plate, and the axisymmetric pattern preferably includes a peaked shape tapering toward the droplet discharging direction, a truncated cone shape tapering toward the droplet discharging direction, a cylindrical columnar shape, and a shape having a bulging part. 
         [0025]    According to the structure, a droplet is easily released at the tip of the droplet guidance part formed in the above shape when discharged. Since the droplet is released at the tip of the droplet guidance part, influence of the shape of the droplet guidance part can be reduced when the droplet is discharged. 
         [0026]    In this case, the droplet guidance part preferably has a first support supporting the droplet guidance part and fixing the droplet guidance part to the first surface of the nozzle plate. 
         [0027]    According to the structure, since the droplet discharge part is fixed to the nozzle plate via the first support, the length of the first support can be within the length ranging from the outer circumference of the penetration part to the droplet guidance part. Therefore, stress received by the first support can be reduced by shortening the first support based on the principle of leverage when force is applied to discharge a droplet to the droplet guidance part or to manufacture the droplet guidance part. As a result, a droplet discharging head having high reliability can be provided. 
         [0028]    In this case, the droplet guidance part preferably has a second support extending toward the pressure chamber so as to be fixed on a wall of the pressure chamber. The wall faces the nozzle plate. 
         [0029]    In the structure, the droplet guidance part is fixed to the wall of the pressure chamber via the second support. Therefore, a mechanism to maintain the positional relationship between the nozzle plate and the droplet guidance part can be disposed at a position away from a part related to the discharge of a droplet. As a result, a structure can be provided that can suppress the occurrence of a turbulent flow in a region in which a droplet is discharged. 
         [0030]    In this case, the droplet guidance part preferably has a second support that extends toward the pressure chamber and bends or branches in the pressure chamber so as to be fixed on a sidewall of the pressure chamber. 
         [0031]    In the structure, the droplet guidance part is, likewise the above, fixed to the sidewall of the pressure chamber via the second support. Therefore, a mechanism to maintain the positional relationship between the nozzle plate and the droplet guidance part can be disposed at a position away from a part related to the discharge of a droplet. As a result, a structure can be provided that can suppress the occurrence of a turbulent flow in a region in which a droplet is discharged. 
         [0032]    According to a second aspect of the invention, a method for manufacturing the droplet discharging head according to the first aspect of the invention includes forming the droplet guidance part having the first support, and fixing the first support on the first surface of the nozzle plate. 
         [0033]    Since the droplet guidance part is fixed to the nozzle plate via the first support, the position of either one of the droplet guidance part and the nozzle plate is fixed, and then the other is fixed after adjusting the position. Therefore, they can easily be positioned. 
         [0034]    According to a third aspect of the invention, a method for manufacturing the droplet discharging head according to the first aspect of the invention includes forming the droplet guidance part and the second support and fixing the droplet guidance part on the wall of the pressure chamber with the second support interposed between the droplet guidance part and the wall. 
         [0035]    Since the droplet guidance part is fixed to the wall of the pressure chamber with the second support, a mechanism to maintain the positional relationship between the nozzle plate and the droplet guidance part is away from a part related to discharge a droplet. The method can be provided that realizes the structure in which the occurrence of a turbulent flow is suppressed by using the step to fix the second support to a position away from the nozzle plate. 
         [0036]    In this case, the droplet guidance part having the first support and the droplet guidance part having the second support are preferably formed by using one of a dry etching method, a light-forming method, and an ion beam forming method. 
         [0037]    The method can provide a step in which a number of droplet guidance parts are manufactured in a short time when the dry etching method is used as a method for manufacturing a droplet discharging head in the step to manufacture the droplet guidance part having the first or second support. Because, the dry etching method can form a number of droplet guidance parts simultaneously. Using the light-forming method can achieve a droplet guidance part having a complicated shape that is hardly manufactured by other methods, providing a manufacturing step of a droplet guidance part having an excellent controllability of a droplet. In addition, using the ion beam forming method can form a droplet guidance part by using a material to which the dry etching method and the light-forming method are hardly applied, providing a manufacturing step of a droplet guidance part using various materials. 
         [0038]    A droplet discharging device according to a fourth aspect of the invention includes the droplet discharging head according to the first aspect of the invention. 
         [0039]    The droplet discharging device can achieve highly accurate drawings since the droplet discharging head is included that discharges a droplet with highly landing accuracy. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0040]    The invention will be described with reference to the accompanying drawings, wherein like numbers reference like elements. 
           [0041]      FIG. 1A  is a plan view illustrating a nozzle plate including a truncated cone shape part and a cylindrical columnar part. 
           [0042]      FIG. 1B  is a sectional view taken along the line A-A of  FIG. 1A . 
           [0043]      FIG. 2A  is a plane view illustrating a droplet guidance part having an axisymmetric pattern. 
           [0044]      FIG. 2B  is a sectional view taken along the line A-A of  FIG. 2A . 
           [0045]      FIG. 3A  is a plane view illustrating a discharge part of a droplet discharging head in which the droplet guidance part is overlapped on the nozzle plate. 
           [0046]      FIG. 3B  is a sectional view taken along the line A-A of  FIG. 3A . 
           [0047]      FIG. 4  is a sectional view illustrating a manufacturing step of a nozzle plate including a truncated cone shape part and a cylindrical columnar part. 
           [0048]      FIG. 5A  is a plane view illustrating a nozzle plate that has a first cylindrical columnar part, a second cylindrical columnar part, and an axisymmetric pattern. The second cylindrical columnar part has a radius smaller than that of the first cylindrical columnar part and is combined with the first cylindrical columnar part. 
           [0049]      FIG. 5B  is a sectional view taken along the line A-A of  FIG. 5A . 
           [0050]      FIG. 6A  is a plan view illustrating a droplet guidance part having an axisymmetric pattern. 
           [0051]      FIG. 6B  is a sectional view taken along the line A-A of  FIG. 6A . 
           [0052]      FIG. 7A  is a plane view illustrating a discharge part included in a droplet discharging head in which the droplet guidance part is overlapped on the nozzle plate. 
           [0053]      FIG. 7B  is a sectional view taken along the line A-A of  FIG. 7A . 
           [0054]      FIGS. 8A and 8B  are sectional views illustrating steps for manufacturing the first cylindrical columnar part and the second cylindrical columnar part. 
           [0055]      FIG. 9A  is a plan view illustrating a step for manufacturing a droplet guidance part. 
           [0056]      FIG. 9B  is a sectional view taken along the line A-A of  FIG. 9A . 
           [0057]      FIG. 10A  is a plan view illustrating a step for manufacturing a droplet guidance part. 
           [0058]      FIG. 10B  is a sectional view taken along the line A-A of  FIG. 10A . 
           [0059]      FIG. 11A  is a plan view illustrating a step for manufacturing a droplet, guidance part. 
           [0060]      FIG. 11B  is a sectional view taken along the line A-A of  FIG. 11A . 
           [0061]      FIG. 12A  is a plan view illustrating a step for manufacturing a droplet guidance part. 
           [0062]      FIG. 12B  is a sectional view taken along the line A-A of  FIG. 12A . 
           [0063]      FIGS. 13A through 13D  are sectional views illustrating steps for manufacturing a droplet discharging head by using a light-forming technique. 
           [0064]      FIG. 14A  is a schematic perspective view illustrating the major part of a structure including a droplet discharging head. 
           [0065]      FIG. 14B  is a schematic sectional view. 
           [0066]      FIGS. 15C and 15D  are sectional views illustrating another structure of a droplet discharging head. 
           [0067]      FIG. 16  is a schematic perspective view of a droplet discharging device. 
       
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     First Embodiment 
       [0068]    As a first embodiment of the invention, a schematic structure and a forming method of a nozzle plate will be described with reference to the following drawings. The nozzle plate includes a truncated cone shape as a tapered shape part and a cylindrical columnar shape disposed at a side adjacent to a small opening diameter of the truncated cone shape.  FIG. 1A  is a plane view illustrating a nozzle plate. The nozzle plate includes a truncated cone shape part having a truncated cone shape (a shape after removing a peaked part, from a conical shape) and a cylindrical columnar shape part connected to the small end of the truncated cone shape, and has an axisymmetric pattern.  FIG. 1B  is a sectional view taken along the line A-A of  FIG. 1A .  FIG. 2A  is a plane view illustrating a droplet guidance part having an axisymmetric pattern.  FIG. 2B  is a sectional view taken along the line A-A of  FIG. 2A .  FIG. 3A  is a plane view illustrating a discharge part of a droplet discharging head in which the droplet guidance part is overlapped on the nozzle plate.  FIG. 3B  is a sectional view taken along the line A-A of  FIG. 3A . 
         [0069]    As shown in  FIG. 1A , a nozzle plate  10  has a truncated cone shape part  11  and a cylindrical columnar part  12  both of which serve as a penetration part.  FIG. 1B , the sectional view taken along the line A-A, shows the relative position between the truncated cone shape part  11  and the cylindrical columnar part  12 . A droplet is supplied from the truncated cone shape part  11  and discharged through the cylindrical columnar part  12 . A droplet guidance part  13  having a conical shape, shown in  FIGS. 2A and 2B , is coaxially arranged and fixed to the truncated cone shape part  11  and the cylindrical columnar part  12 , both of which are shown in  FIG. 1B , of the nozzle plate  10  with a first support  14  supporting the droplet guidance part  13 . As a substitute of the truncated cone shape part  11 , another member may be used that has a shape having different curvatures such as a horn shape. Here, a circular constructional member of the first support  14  can be omitted. The constructional member can employ another shape, which will be described later as a fourth modification.  FIGS. 3A and 3B  show a discharge part  15  included in a droplet discharging head, which is formed by coaxially arranging the droplet guidance part  13  to the truncated cone shape part  11  and the cylindrical columnar part  12  of the nozzle plate  10 . The droplet guidance part  13  is disposed so that the tip thereof is positioned in the vicinity of the border between the truncated cone shape part  11  and the cylindrical columnar part  12 , and the tip does not touch any of the sidewalls of the truncated cone shape part  11  and the cylindrical columnar part  12 , guiding a droplet onto the axes of the truncated cone shape part  11  and the cylindrical columnar part  12 . The tip of the droplet guidance part  13  can be disposed inside the truncated cone shape part  11  and the cylindrical columnar part  12 . The axis of the droplet guidance part  13  is coaxially arranged and fixed to the axes of the truncated cone shape part  11  and the cylindrical columnar part  12 . In this regard, other arrangements than the coaxial arrange can be employed as long as discharging a droplet can be controlled. 
         [0070]    Next, a method for manufacturing the truncated cone shape part  11  and the cylindrical columnar part  12  shown in  FIGS. 1A and 1B  will now be described. As a material for a nozzle plate material  10 a, a stainless steel can be exemplified.  FIG. 4  is a sectional view illustrating a method for manufacturing a nozzle plate having the truncated cone shape part  11  and the cylindrical columnar part  12 .  FIG. 4  shows a punch  21  having a shape of the combination of the truncated cone shape and the cylindrical columnar shape, and a die having a hole  23 . The hole  23  has an inner diameter slightly larger than that of the cylindrical columnar part of the punch  21  so that a punched slug  24  after punching the nozzle plate material  10   a  with the punch  21  can go through the hole  23 . 
         [0071]    First, the nozzle plate material  10   a  is set to the die  22 . Then, the punch  21  is touched to the nozzle plate material  10   a  and the cylindrical columnar shape part of the punch  21  is forced to penetrate the nozzle plate material  10   a.  The punched slug  23  produced during the penetration is passed through the hole  23 . Through the step, the cylindrical columnar part  12  is formed. Simultaneously, the truncated cone shape part  11  is formed by being pressed with the truncated cone shape of the punch  21 . As a result, the nozzle plate  10  (refer to  FIGS. 1A and 1B ) is made using the nozzle plate material  10   a.    
         [0072]    Since the tip of the droplet guidance part  13  is positioned in the truncated cone shape part  11 , a droplet is released at the tip of the droplet guidance part  13  and discharged when the droplet is discharged. The influence of the shape of the droplet guidance part  13  is relaxed in discharging a droplet and a droplet is disposed at a position to be discharged by the droplet guidance part  13  since the droplet is released at the tip. Thus, the droplet is discharged with having straight flying property. As a result, variation in a droplet discharging direction can be suppressed. 
       Second Embodiment 
       [0073]    An example in which two cylindrical columnar parts, each having a different radius, are disposed in a nozzle plate will be described as a second embodiment with reference to the accompanying drawings.  FIG. 5A  is a plane view illustrating a nozzle plate that has a first cylindrical columnar part, a second cylindrical columnar part, and an axisymmetric pattern. The second cylindrical columnar part has a radius smaller than that of the first cylindrical columnar part and is combined with the first cylindrical columnar part.  FIG. 5B  is a sectional view taken along the line A-A of  FIG. 5A .  FIG. 6A  is a plane view illustrating a droplet guidance part having an axisymmetric pattern.  FIG. 6B  is a sectional view taken along the line A-A of  FIG. 6A .  FIG. 7A  is a plane view illustrating a discharge part included in a droplet discharging head in which the droplet guidance part is overlapped on the nozzle plate.  FIG. 7B  is a sectional view taken along the line A-A of  FIG. 7A . 
         [0074]    As shown in  FIGS. 5A and 5B , a nozzle plate  30  has a first cylindrical columnar part  31  and a second cylindrical columnar part  32  both of which serve as a penetration part. A droplet is supplied from the first cylindrical columnar part  31  and discharged through the second cylindrical columnar part  32 . 
         [0075]    A droplet guidance part  33  having a cylindrical columnar shape as an axisymmetric pattern, shown in  FIGS. 6A and 6B , is coaxially arranged and fixed to the first cylindrical columnar part  31  and the second cylindrical columnar part  32 , shown in  FIGS. 5A and 5B , of the nozzle plate  30  with a first support  34  supporting the droplet guidance part  33 . Here, a circular constructional member of the first support  34  can be omitted. The constructional member can employ another shape, which will be described later as the fourth modification. 
         [0076]    As shown in  FIGS. 7A and 7B , the droplet guidance part  33  is disposed inside the first cylindrical columnar part  31  of the nozzle plate  30  so as to penetrate the nozzle plate  30 , thereby forming a discharge part  35  included in a droplet discharging head. The droplet guidance part  33  of the discharge part  35  included in a droplet discharging head is disposed so that the tip thereof is positioned in the vicinity of the border between the first cylindrical columnar part  31  and the second cylindrical columnar part  32 , and the tip does not touch any of the sidewalls of the first cylindrical columnar part  31  and the second cylindrical columnar part  32 , guiding a droplet onto the axes of the first cylindrical columnar part  31  and the second cylindrical columnar part  32 . The tip of the droplet guidance part  33  can be disposed inside the first cylindrical columnar part  31  and the second cylindrical columnar part  32 . This arrangement in which the axis of the droplet guidance part  33  is coaxially disposed to the axes of the first cylindrical columnar part  31  and the second cylindrical columnar part  32  can achieve a structure having high symmetric property. In this regard, other arrangements than the coaxial arrange can be employed as long as discharging a droplet can be controlled. 
         [0077]    Next, a method for manufacturing the first cylindrical columnar part  31  and the second cylindrical columnar part  32 , both of which are shown in  FIGS. 5A and 5B , will be described. As a material for a nozzle plate material  30   a,  a silicon substrate can be exemplified.  FIG. 8A and 8B  are sectional views illustrating steps for manufacturing the first cylindrical columnar part  31  and the second cylindrical columnar part  32 . 
         [0078]    First, as shown in  FIG. 8A , a photoresist layer  36  is formed as a pattern on the nozzle plate material  30   a.  Then, an area corresponding to the second cylindrical columnar part  32  is etched. 
         [0079]    Next, the photoresist layer  36  is removed and a photoresist layer  37  is anew formed as shown in  FIG. 8B . Then, an area corresponding to the first cylindrical columnar part  31  is etched. The order of forming the first cylindrical columnar part  31  and the second cylindrical columnar part  32  does not necessarily follow the above order, but the first cylindrical columnar part  31  may be formed first. Alternatively, the second cylindrical columnar part  32  may be formed from a surface opposite to a surface on which the first; cylindrical columnar part  31  is formed. 
         [0080]    Additionally, they may be formed, by using a technique described in the first embodiment, with a punch and a die. In this case, a ductile material such as a stainless steel is preferably used as a material for the nozzle plate. 
         [0081]    The volume difference or a step at the border between the first cylindrical columnar part  31  and the second cylindrical columnar part  32  may cause an occurrence and gathering of bubbles, adversary affecting discharge stability. Positioning the tip of the droplet guidance part  33  inside the first cylindrical columnar part  31  can reduce the volume difference and control the change of a meniscus position smoothly. As a result, discharge performance and continuous discharge performance can be improved. When a structure is employed in which a bulging part is provided inside the first cylindrical columnar part  31 , the volume difference between the first cylindrical columnar part  31  and the second cylindrical columnar part  32  can be suppressed. Further, a tapered shape extending toward a discharging direction of a droplet in the structure can more stabilize the discharging direction. 
       Third Embodiment 
       [0082]    A third embodiment of the invention will be described below. In the embodiment, a wiring material used for forming a wiring pattern by a droplet discharge method, the droplet discharge method, and a hardening treatment of the wiring material will be described in this order before describing a distinctive method for manufacturing a droplet discharging head. 
         [0083]    Wiring Material 
         [0084]    As a wiring material for forming a wiring pattern by a droplet discharge method, a dispersed solution is used in which conductive fine particles are dispersed in a dispersion medium. According to the embodiment, examples of the conductive fine particles may include: metal fine particles containing any of gold, silver, copper, iron, chromium, manganese, molybdenum, titanium, palladium, tungsten, and nickel; their oxides; and fine particles of a conductive polymer or a super-conductive material. These conductive fine particles may be used by coating their surfaces with an organic matter or the like to improve their dispersibility. The diameter of the conductive fine particle is preferably in the range from 1 nm to 0.1 μm inclusive. Using conductive fine particles having a diameter 0.1 μm or less can prevent the discharge part of a droplet discharging head from being clogged. Using conductive fine particles having a diameter  1  nun or more can control the volume ratio of a coating agent to the conductive fine particles in an adequate range. As a result, the proportion of an organic matter contained in the resulting film can be controlled in an adequate range. 
         [0085]    Here, any dispersion medium can be used as long as it is capable of dispersing the above conductive fine particles and suppressing the aggregation of the particles. As the dispersion medium, the following hydrocarbon compounds can be exemplified: alcohols such as methanol, ethanol, propanol, and butanol; n-heptane, n-octane, decane, dodecane, tetradecane, toluene, xylene, cymene, durene, indene, dipentene, tetrahydronaphthalene, decahydronaphthalene, and cyclohexylbenzene, in addition to water, 
         [0086]    The following ether type compounds also can be exemplified: ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol methyl ethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol methyl ethyl ether, 1,2-dimethoxyethane, bis(2-methoxyethyl) ether, and p-dioxane. 
         [0087]    Further, the following polar compounds can be exemplified: propylene carbonate, γ-butyrolactone, N-methyl-2-pyrrolidone, dimethyl formamide, dimethyl sulfoxide, and cyclohexanone. 
         [0088]    Water, alcohols, hydrocarbon compounds, and ether compounds are preferably used in terms of particle dispersibility, dispersed solution stability, and applicability to a droplet discharge method. Among others, water and hydrocarbon compounds are more preferably used. 
         [0089]    The surface tension of the dispersed solution of the conductive fine particles is preferably within the range from 0.02 N/m to 0.07 N/m inclusive. When a droplet L is discharged by a droplet discharge method, maintaining the surface tension 0.02 N/m or more can suppress the wettability of a functional liquid composition with respect to the surface of the discharge part. As a result, an occurrence of a flight curve can be prevented. In contrast, maintaining the surface tension 0.07 N/m or less can stabilize the meniscus shape at the tip the discharge part. As a result, a discharge amount and discharge timing can be precisely controlled. 
         [0090]    In order to adjust the surface tension, a fluorine-, silicone- or nonionic-based surface tension adjuster, for example, may be added in a small amount to the dispersed solution in a range not largely lowering a contact angle with respect to a substrate. The nonionic surface tension adjuster enhances the wettability of a liquid with respect to a substrate, improves the leveling property of a film, and serves to prevent minute concavities and convexity of the film from being formed. The surface tension adjuster may include, if necessary, organic compounds, such as alcohol, ether, ester, and ketone. 
         [0091]    The viscosity of the dispersed solution is preferably within the range from 1 mPa·s to 50 mPa·s inclusive. When a liquid material is discharged as the droplet L by using a droplet discharge method, maintaining the viscosity 1 mPa·s or more can prevent a functional liquid from flowing out to the periphery of the discharge part. As a result, contamination can be prevented. In contrast, maintaining the viscosity 50 mPa·s or less prevents the discharge part from being clogged. As a result, a smooth discharge can be achieved. 
         [0092]    Droplet Discharge Method 
         [0093]    As the discharge technique of a droplet discharge method, an inkjet method is preferably used that can form fine patterns in an on-demand manner. Examples of the inkjet method include electromechanical converting and electrostatic driving methods. The electromechanical converting method utilizes the characteristic of a piezo element (piezoelectric element) that it is deformed in response to a pulsed electric signal. In the method, the deformation of the piezo element applies pressure, via an elastic material, to a space storing a material, pushing the material out of the space to discharge it from a discharge part. In the electrostatic driving method, pressure produced by attractive and repulsive forces of electrostatic charges is applied to a space in which a material is stored via a flexible material so as to push out the material from the space, thereby discharging the material from a discharge part. Other than the above methods, a thermal method using a heater can be used as a droplet discharge method. 
         [0094]    The droplet discharge method has an advantage in that a desired amount of a material can be adequately disposed to a desired location with little waste of the material. An amount of a liquid material droplet discharged by the droplet discharge methods is, for example, from  1  to 300 nanograms. 
         [0095]    Hardening Treatment of the Wiring Material 
         [0096]    A hardening treatment of the wiring material, called as a firing treatment, is usually carried out in the atmosphere. The treatment also can be performed in an environment of an inert gas, such as nitrogen, argon, and helium, if necessary. The processing temperature for the firing treatment will be determined at an appropriate level, taking into account the boiling point (vapor pressure) of the dispersion medium., the type and pressure of the atmospheric gas, thermal behavioral properties such as the dispersibility and oxidizability of fine particles, the existence and volume of coating material, and the base material heat resistance temperature, or the like. In the embodiment, the wiring material is subjected to a firing treatment under the following conditions: at 200° C., for about 60 minutes, and with a clean oven in the atmosphere. Through the above treatment, wiring layers (not shown) can be formed to secure an electrical contact between fine particles. 
         [0097]    Such firing treatment can be conducted with a hot plate or an electric furnace. Alternatively, lamp annealing can also be employed. Examples of light sources for lamp annealing are not limited to but include: an infrared lamp, a xenon lamp, YAG laser, argon laser, carbon dioxide laser, and excimier laser of XeF, XeCl, XeBr, KrF, IrCl, ArF, ArCl, or the like. The light sources generally have a power ranging from 10 W to 5000 W inclusive, but for the embodiment it is sufficient to provide the range from 100 W to 1000 W inclusive. As described above, a wiring material is disposed by using a droplet discharge method, and then the wiring material is hardened to form a desired wiring pattern. 
       Fourth Embodiment 
       [0098]    As a fourth embodiment, a method for manufacturing a droplet guidance part by using a dry etching method will be described below with reference to the accompanying drawings.  FIGS. 9A to 12A  are plan views illustrating manufacturing steps of a droplet guidance part.  FIGS. 9B to 12B  are sectional views taken along the line A-A of respective plan views. 
         [0099]    First, as step  1  shown in  FIGS. 9A and 9B , a photoresist layer  41  is formed on a silicon substrate  40  as a pattern having a fun shape. Then, the silicon substrate  40  is anisotropic etched by using the photoresist layer  41  as a mask to form a fun-shape hole penetrating the silicon substrate  40 . 
         [0100]    Next, as step  2  shown in  FIGS. 10A and 10B , the photoresist layer  41  is etched so as to be removed. Then, a photoresist layer  41  having a cylindrical columnar shape is anew formed on the central part, surrounding of which is etched off in a fun shape, of the silicon substrate  40 . 
         [0101]    Next, as step  3  shown in  FIGS. 11A and 11B , the silicon substrate  40  is etched with the photoresist layer  42  as a mask. Etched with an etching condition by which the silicon substrate  40  is anisotropic etched and the side surface of the photoresist layer  42  is gradually etched, the silicon substrate  40 , located under the photoresist layer  42 , can be shaped in a tapered form. 
         [0102]    With the above etching condition, a droplet guidance part  43  having a conical shape, and a first support  44  are formed as an axisymmetric pattern having a peaked shape. Here, a circular constructional member of the first support  44  can be omitted. For example, it can be removed simultaneously when the silicon substrate  40  is etched in a fun shape of step  2 . The constructional member can employ another shape, which will be described later as the fourth modification. When the photoresist layer  42  remains since it is not thoroughly etched during processing the silicon substrate  40  in a tapered form, the remains is removed by an additional step. The droplet guidance part  13 , used in the first embodiment and shown in  FIGS. 3A and 3B , can be manufactured by the method. 
         [0103]    Alternatively, dry etching may be employed in which used are silicon oxide as a substitute for the silicon substrate  40 , a nickel mask as a substitute for the photoresist layer  42 , and a mixed gas of carbon tetrafluoride, difluoromethane, and oxygen as an etching gas. Using such materials and gases also can achieve a tapered shape. 
         [0104]    As another manner in step  3 , a droplet guidance part  45  and a first support  46  shown in  FIGS. 12A and 12B  are formed by performing an anisotropic etching with covering the side surface of the photoresist layer  49 . The droplet guidance part  33 , which includes a cylindrical columnar shape having an axisymmetric pattern as shown in  FIGS. 7A and 7B  and is used in the second embodiment, can be manufactured by the method. 
         [0105]    Here, a circular constructional member of the first support  46  can be omitted. For example, it can be removed simultaneously when the silicon substrate  40  is etched in a fun shape of step  2 . The constructional member can employ another shape, which will be described later as the fourth modification. 
         [0106]    As shown in  FIGS. 3A and 3B , the droplet guidance part  13  formed by the above steps can form a discharge part included in a droplet discharging head by fixing the first support  14  on the droplet supply side surface of the nozzle plate  10 . 
         [0107]    Likewise, as shown in  FIGS. 7A and 7B , the droplet guidance part  33  formed by the above steps can form a discharge part included in a droplet discharging head by fixing the first support  34  on the droplet supply side surface of the nozzle plate  30 . 
       Fifth Embodiment 
       [0108]    As a fifth embodiment, a method for manufacturing a droplet guidance part by using a light-forming method or an ion beam method will be described below with reference to the accompanying drawings.  FIGS. 13A to 13D  are sectional views illustrating manufacturing steps using a light-forming technique in order to cope with a case in which a droplet guidance part, used for a discharge part included in a droplet discharging head, has a complicated shape. In the embodiment, a droplet guidance part  52 , shown in  FIG. 13D , having a part of a bulging shape is formed. 
         [0109]    First, as step  1  shown in  FIG. 13A , a light curing resin  51   a  is coated so as to cover a first surface of a substrate  50 . 
         [0110]    Next, as step  2  shown in  FIG. 13B , a desired area is irradiated with light to be cured. As a result, a light cured part  51  is formed, 
         [0111]    Then, as step  3  shown in  FIG. 13C , the light curing resin  51   a  is removed while the light cured part  51  remains. 
         [0112]    By repeating the above steps shown in  FIGS. 13A to 13C , a droplet guidance part  52  having a desired shape (a bulging shape in the embodiment) can be achieved as shown in  FIG. 13D . The light-forming technique can form all shapes, which will be described in a second modification, in addition to the droplet guidance part  13  formed in the first embodiment, and the droplet guidance part  33  formed in the second embodiment. 
         [0113]    Here, an ion beam etching may be used for forming complicated structures. Using a transport-positioning mechanism that relatively changes an ion beam irradiation position can form complicated structures. Processing by using ion beams makes it possible to choose metal as a material to be etched. Since metal shows less aging change, a higher reliable droplet guidance part can be formed. 
       Sixth Embodiment 
       [0114]    As a sixth embodiment, a structure of a droplet discharging head mounted in a droplet discharging device will be described below with reference to the accompanying drawings.  FIGS. 14A and 14B  show a major part of a structure including s droplet discharging head.  FIG. 14A  is the schematic perspective view of the structure.  FIG. 14B  is the schematic sectional view of the structure. 
         [0115]    As shown in  FIG. 14A , a droplet discharging head  80  includes a nozzle plate  59  made of a stainless steel or the like, a vibration plate  61  facing the nozzle plate  59 , and a partition  62  interposed between the nozzle plate  59  and the vibration plate  61  to bond them. Between the nozzle plate  59  and the vibration plate  61 , formed are a plurality of pressure chambers  63  and a liquid reservoir  64  with the partition  62 . The plurality of pressure chambers  63  communicates with the liquid reservoir  64  through a passage  68 . 
         [0116]    The vibration plate  61  has a material supply hole  66 . A material supply device  67  is connected to the material supply hole  66 . The material supply device  67  supplies a material N containing a wiring material and the like to the material supply hole  66 . The supplied material N fully fills in the liquid reservoir  64  and further fully fills the pressure chambers  63  after passing though the passage  68 . In  FIG. 14A , a penetration part  70  is shown simplified as a cylinder hollow shape. The detailed structure adjacent to the penetration part  70  is shown in  FIG. 14B . 
         [0117]    As shown in  FIG. 14B , the nozzle plate  59  has the penetration part  70  to discharge the material N from the pressure chamber  63  like a jet, and a droplet guidance part  74 , which is supported by a first support  75  and controls the flow of the material N. 
         [0118]    Instead of the first support  75 , a support  76  can be used for fixing the droplet guidance part  74  to the vibration plate  61  as shown in  FIG. 15C .  FIG. 15C  is a sectional view illustrating another structure of the droplet discharging head. This fixing method can guide a droplet with suppressing turbulence of a droplet flow compared to the case of using the first support  7   5  for fixing the droplet guidance part  74 . 
         [0119]    Additionally, the second support  76  can be fixed to a sidewall facing the nozzle plate  59  by changing the position of the vibration plate  61  facing the nozzle plate  59 . In this case, a mass addition is avoided that is caused by providing the droplet guidance part  794  and the second support  76  to the vibration plate  61 . The droplet guidance part  74  can be supported without influencing a droplet discharge movement. 
         [0120]    Additionally, as shown in  FIG. 15D , the second support  76  used for fixing the droplet guidance part  74  can be fixed to the partition  62  serving as the sidewall of the pressure chamber  63  by branching the second support  76  in the pressure chamber  63 .  FIG. 15D  is a sectional view illustrating another structure of the droplet discharging head. This fixing method can guide a droplet only by the sidewall of the pressure chamber  63  with suppressing turbulence of a droplet flow caused by the location change of the vibration plate  61 f or the forming the support. In this case, the second support  76  can be supported by the vibration plate  61  when the vibration plate  61  is disposed to the sidewall of the pressure chamber  63 . While the embodiment is described based on a case in which the droplet guidance part  74  is supported by the first support  75 , a case of using the second support  76  can also be followed in the same manner. 
         [0121]    A material pressurization member  69  is fixed on a surface, opposite to a surface facing the pressure chamber  63 , of the vibration plate  61  so as to correspond the pressure chamber  63 . The material pressurization member  69  includes a piezoelectric element  71 , and a pair of electrodes  72   a  and  72   b  sandwiching the piezoelectric element  71 . The piezoelectric element  71  deforms to bulge outwardly as shown with the arrow C by energizing the electrodes  79   a  and  72   b.  The deformation increases the volume of the pressure chamber  63 . As a result, the material N flows in the pressure camber  63  from the liquid reservoir  64  though the passage  68  by an amount equivalent to the increased volume. 
         [0122]    Upon stopping energization to the piezoelectric element  71 , the piezoelectric element  71  and the vibration plate  61  are put back to the original shape, resulting in the volume of the pressure chamber  63  being put back to the original. This recovery increases the pressure of the material N inside the pressure chamber  63 . As a result, the material N is discharged from the penetration part  70  as a droplet. 
         [0123]    Here, the material pressurization member  69  may employ a structure of using electrostatic charges instead of the piezoelectric element. In order to avoid the occurrence of flight curve of the droplet L, and clogging the penetration part  70  and the like, a repellent material layer  73  composed of Ni-tetrafluoroethylene eutectoid plating layer, for example, is formed in the vicinity of the penetration part  70 . 
         [0124]    Next, a method for manufacturing the droplet discharging head of the embodiment will be simply described with reference to  FIGS. 14A and 14B . First, the droplet guidance part  74  is fixed to the penetration part  70  of the nozzle plate  59  with the first support  75 . Then, the partition  62  and the vibration plate  61  are integrally fixed to the nozzle plate  59  so as to form the droplet discharging head  80 . 
         [0125]    While the penetration part  710  composed by combining a truncated cone shape and a cylindrical columnar shape is used in the embodiment, the penetration part  70  composed by combining two cylindrical columnar shapes may be used as described in the second embodiment. In addition, the shapes described in a first modification (described later) may also be used. Further, the shape of the droplet guidance part  74  is not limited to a conical shape or a cylindrical columnar shape. The shapes described in the second modification (described later) may also be used. 
       Seventh Embodiment 
       [0126]    A droplet discharging device according to a seventh embodiment of the invention will now be described.  FIG. 16  is a perspective view illustrating a droplet discharging device  100 . In  FIG. 16 , an X direction is the right-and-left direction of a base  101 , a Y direction is the back and forth direction, and a Z direction is the up and down direction. The droplet discharging device  100  is mainly constituted by the droplet discharging head  80  and a table  103  on which a substrate P is placed. The movement of the droplet discharging device  100  is controlled by a controller  11 ( 0 . 
         [0127]    The table  103  placing the substrate P is allowed to move and to be positioned in the Y direction by a first moving means  102 , and is allowed to oscillate and to be positioned in a θz direction by a motor  104 . On the other hand, the droplet discharging head  80  is allowed to move and to be positioned in the X direction by a second moving means, and is allowed to move and to be positioned in the Z direction by a linear motor  108 . The droplet discharging head  80  is allowed to oscillate and to be positioned in α,β, and γ directions by motors  105 ,  106 , and  107 , respectively. Accordingly, the droplet discharging device  100  can accurately control the position and attitude of a discharge face  81  of the droplet discharging head  80  relative to the substrate P on the table  103 . 
         [0128]    A capping unit  56 , shown in  FIG. 16 , caps the discharge face  81  at the time of standby of the droplet discharging device  100  to prevent the discharge face  81  of the droplet discharging head  80  from being dried. A cleaning unit  58  sucks the inside of the discharge part to remove clogs in the discharge part of the droplet discharging head  80 . The cleaning unit  58  can also wipe the discharge face  81  to remove the dirt on the discharge face  81  of the droplet discharging head  80 . 
         [0129]    The droplet discharging device  100  can achieve highly accurate drawings since the droplet discharging head  80  is mounted that can improve the landing position accuracy of the droplet L. When the droplet discharging device  100  is used for a printing device such as an inkjet printer that uses the droplet L as ink, the printing device can improve its printing quality. 
         [0130]    First Modification 
         [0131]    In the first embodiment, the shape of combining the truncated cone shape part  11  and the cylindrical columnar part  12  shown in  FIGS. 1A and 1B  is exemplified as a part of the penetration part. In the second embodiment, the shape of combining the first cylindrical columnar part  31  and the second cylindrical columnar part  32  shown in  FIGS. 5A and 5B  is exemplified as a part of the penetration part. They are only exemplified. The shape is not limited to these examples. 
         [0132]    Instead of the above examples, the following exemplified shapes may be employed: a polygon, including a regular polygon, pyramid; a conical shape having a star shape cross-section; and a shape excluding the tip part of a conical shape having a oval shape cross-section. The shape is not limited to a conical shape. A polygon prism including a regular polygon prism, a column having a star shape cross-section, and a column having an oval shape cross-section may be used. Additionally, a shape of connecting columnar and conical shapes in a plurality of numbers may be employed. In this regard, connecting them so as to form a shape tapering towards a droplet discharge side is preferable since the shape allows a droplet to flow without interruption. Further, a uniform or nonuniform groove may de formed inside the conical or columnar shapes. 
         [0133]    A shape of connecting a columnar shape having the same cross-section of an area exposed from the above conical shape after cutting off the tip part thereof may be employed for substituting the cylindrical columnar part  12  shown in  FIGS. 1A and 1B , and the second cylindrical columnar part  32  shown in  FIGS. 5A and 5B . In addition, a shape different from the cross-section shape of the area exposed from the above conical shape after cutting off the tip part thereof may be employed. Further, a uniform or nonuniform groove may be formed inside the columnar shapes. 
         [0134]    Furthermore, the axisymmetric pattern is not necessarily required. A pattern having no symmetric axis of rotation can be used. In this case, a droplet is released from a fixed position of the penetration part upon discharging the droplet. As a result, repeatability of landing position can be improved. 
         [0135]    Second Modification 
         [0136]    In the first and second embodiments, the droplet guidance part having a conical or a cylindrical columnar shape is described. However, another shape such as a truncated cone shape, which is a shape of excluding the tip part of a conical shape, may be used. Additionally, the following shapes may be used: pyramids of polygons including regular polygons; a conical shape having a star shape cross-section; a conical shape having an oval shape cross-section; and a shape excluding the tip part of the conical shapes. Further, the following shapes may be used: cylindrical columns; polygon columns including regular polygon columns; a column having a star shape cross-section; a column having an oval shape cross-section; and a shape having a bulging part. Furthermore, the axisymmetric pattern is not necessarily required. A pattern having no symmetric axis of rotation can be used. In this case, a droplet is released from a fixed position of the droplet guidance part upon discharging the droplet. As a result, repeatability of landing position can be improved. Further, the above shapes may be used by additionally forming a uniform or nonuniform groove inside thereof. The formed groove enhances a droplet releasing property, making it possible to discharge a droplet with high straight flying property. 
         [0137]    Third Modification 
         [0138]    In the fourth embodiment, the manufacturing method for forming the droplet guidance part by dry etching is described. The droplet guidance part has a pattern with a peak such as a conical shape or an axisymmetric pattern such as a cylindrical columnar shape. Using the dry etching technique can form various patterns. For example, by only changing the plane shape of the photoresist layer  42  used in step  9 , the following shapes can be achieved: polygons including regular polygons; a conical shape having a star shape cross-section, an oval shape cross-section, or the like; and a shape excluding the tip part of a conical shape. Additionally, using a pattern asymmetric to rotation for the shape of the photoresist layer  42 , a conical pattern asymmetric to rotation can be achieved. 
         [0139]    Likewise, various columnar shapes, each having a cross-section of such as polygons including regular polygons, a star, and an oval shapes can be achieved by performing an anisotropic etching without removing the side surface of the photoresist layer  42  in step  3  of the fourth embodiment. Additionally, using a pattern asymmetric to rotation for the shape of the photoresist layer  42 , a columnar pattern asymmetric to rotation can be achieved. 
         [0140]    Fourth Modification 
         [0141]    The first and second supports are exemplified each of which supports the droplet guidance part mainly with three beams. The number of beams, however, is not limited to three. The droplet guidance part can be supported by other than three beams. For example, single beam, two beams, or more than three beams may be employed. Additionally, the first and second supports are not limited to a shape having a beam. For example, a plane shape having a through hole for a droplet passing through it may be employed. 
         [0142]    Each of the first and second supports includes the circular constructional member at a fixing end thereof. The circular constructional member is not essential. For example, employing a shape excluding the constructional member for supporting the droplet guidance part can reduce a fixing area. The shape of the constructional member is not limited to a round shape, a polygon shape such as a triangle and a quadrangle shapes may be used. Additionally, the following exemplified shapes may be used: rectangle, trapezoid, inequilateral triangle, and oval. Among them, quadrangle and rectangular shapes are preferably used since the droplet guidance part can be cut off together with the support by dicing or the like. 
         [0143]    The entire disclosure of Japanese Patent Application No. 2006-2811,34, filed on Oct. 16, 2006, is expressly incorporated by reference herein.