Patent Publication Number: US-7901734-B2

Title: Method of manufacturing nozzle plate

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a method of manufacturing a nozzle plate, and more particularly, to a method of manufacturing a nozzle plate of which surface is covered with a liquid-repelling film on the liquid droplet ejection side. 
     2. Description of the Related Art 
     There are inkjet recording apparatuses, which form an image on a recording medium by ejecting ink droplets from nozzles formed on a print head, while moving the print head and the recording medium relatively with respect to each other. The print head has a nozzle plate formed with the nozzles (nozzle orifices) on a surface opposing the recording medium. 
     In the inkjet recording apparatus of this kind, it is known that, in order to stabilize the meniscus of the ink in the nozzle and to prevent adherence of ink droplets and soiling to the surface of the nozzle plate (ink droplet ejection surface), a liquid-repelling film is formed on the surface of the nozzle plate. In a method of manufacturing a nozzle plate of this kind, it is necessary to fill the nozzle orifices with resist. 
     For example, Japanese Patent Application Publication No. 09-076492 discloses a method of manufacturing a nozzle plate in which a dry film resist of an anticorrosive high polymer resin, such as a photosensitive film, is filled into the nozzle orifices formed in a nozzle forming substrate, whereupon the dry film resist is made to project by cutting the surface of the nozzle forming substrate by an etching process, and an ink-repelling surface treatment layer is then formed, whereupon the dry film resist is removed. 
     Japanese Patent Application Publication No. 2002-187267 discloses a method of manufacturing a nozzle plate in which a liquid-repelling film is formed on the whole surface of a nozzle forming substrate formed with nozzle orifices, whereupon a photosensitive dry film resist is applied onto the front surface of the nozzle forming substrate and onto the faces from the front surface to the positions where the meniscus is formed on the inner walls of the nozzle orifices, the unmasked liquid-repelling film is removed by etching, a liquid-philic film is formed onto the rear surface of the nozzle forming substrate and onto the inner walls of the nozzle orifices from which the liquid-repelling film has been removed, and the photosensitive dry film resist is then removed. According to this method, the liquid-repelling film is formed on the nozzle plate surface and the faces from the nozzle plate surface to the positions where the meniscus is formed on the inner walls of the nozzle orifices, whereas the liquid-philic film is formed on the rear surface of the nozzle plate and the faces from the rear surface to the positions where the meniscus is formed on the inner walls of the nozzle orifices. 
     In the present specification, the term “liquid-philic” means “having a strong affinity for the liquid (e.g., the ink)”. For example, in the case where the liquid or the ink is an aqueous solution or water-based, the term “liquid-philic” corresponds to “hydrophilic”. On the other hand, in the case where the liquid or the ink is an oleaginous solution or oil-based, the term “liquid-philic” corresponds to “oleophilic”. 
     However, if a resist is used as in the methods disclosed in Japanese Patent Application Publication Nos. 09-076492 and 2002-187267, then a problem arises in the stage of removing resist after forming the liquid-repelling film. 
     More specifically, in the case of a wet method which dissolves the resist by means of a solvent, such as an organic solvent, sulfuric acid and hydrogen peroxide, or the like, it is necessary to form a liquid-repelling film having resistance to organic chemicals, and this method is undesirable from the viewpoint of environmental safety. Furthermore, in the case of a dry method which removes the resist by means of decomposition by burning by means of plasma, it is difficult to remove completely the resist inside the nozzle orifices and nozzle blockage may occur as a result of residual resist. 
     SUMMARY OF THE INVENTION 
     The present invention has been contrived in view of these circumstances, an object thereof being to provide a method of manufacturing a nozzle plate whereby a nozzle plate having a liquid-repelling film formed on the front surface of the liquid droplet ejection side is manufactured by means of a simple manufacturing process, without using resist. 
     In order to attain the aforementioned object, the present invention is directed to a method of manufacturing a nozzle plate having nozzle orifices for ejecting liquid droplets, the method comprising: a hole forming step of forming holes in a nozzle forming substrate, each of the holes passing through the nozzle forming substrate and having openings on a surface of a liquid droplet ejection side and a surface of a side opposite thereto of the nozzle forming substrate, the holes having a larger diameter than the nozzle orifices; a liquid-philic film forming step of forming a liquid-philic film on inner walls of the holes, the liquid-philic film blocking at least a portion of each of the holes; a liquid-repelling film forming step of forming a liquid-repelling film on the surface of the liquid droplet ejection side of the nozzle forming substrate, after performing the liquid-philic film forming step; and a nozzle orifice forming step of forming the nozzle orifices in the holes that are filled with the liquid-repelling film, after performing the liquid-repelling film forming step. 
     According to the present invention, it is possible to manufacture the nozzle plate in which the surface on the liquid droplet ejection side is covered with the liquid-repelling film, and the inner walls of the nozzle orifices are covered with the liquid-philic film, by means of a simple manufacturing process. Furthermore, since no resist is used, then nozzle blockage as a result of residual resist inside the nozzle orifices does not occur. Moreover, since the nozzle orifices are formed after forming the liquid-philic film in the holes having the larger diameter than the nozzle orifices, then it is possible to form the nozzle orifices of very fine diameter, with a high degree of accuracy. 
     Preferably, the liquid-philic film forming step includes a step of forming the liquid-philic film on the surface of the liquid droplet ejection side of the nozzle forming substrate. 
     According to this aspect of the present invention, the liquid-philic film forming step is facilitated. 
     Preferably, the liquid-philic film forming step includes a step of forming the liquid-philic film on the surface of the liquid droplet ejection side and the surface of the side opposite thereto of the nozzle forming substrate. 
     According to this aspect of the present invention, the liquid-philic film forming step is further facilitated. Furthermore, it is also possible to use the liquid-philic film that is formed on the rear surface of the nozzle forming substrate on the opposite side to the liquid droplet ejection side, as an agent for bonding the nozzle forming substrate to another plate member. 
     Preferably, the method further comprises a liquid-philic film removal step of removing the liquid-philic film formed on the surface of the liquid droplet ejection side of the nozzle forming substrate, before performing the liquid-repelling film forming step. 
     According to this aspect of the present invention, non-uniformity of thickness is prevented in the liquid-repelling film formed on the surface of the liquid droplet ejection side of the nozzle forming substrate. 
     Preferably, the liquid-philic film removal step includes a step of roughening the surface of the liquid droplet ejection side of the nozzle forming substrate. 
     According to this aspect of the present invention, bonding characteristics and liquid-repelling characteristics are improved in the liquid-repelling film formed on the surface of the liquid droplet ejection side of the nozzle forming substrate. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The nature of this invention, as well as other objects and advantages thereof, will be explained in the following with reference to the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures and wherein: 
         FIG. 1  is a general compositional view showing an embodiment of an inkjet recording apparatus using an inkjet head according to the present invention; 
         FIG. 2  is a plan perspective diagram showing an embodiment of the structure of a print head; 
         FIG. 3  is a cross-sectional diagram along line  3 - 3  in  FIG. 2 ; 
         FIG. 4  is an enlarged view showing an embodiment of the nozzle arrangement in the print head shown in  FIG. 2 ; 
         FIGS. 5A to 5E  are illustrative diagrams showing steps for manufacturing a nozzle plate; 
         FIGS. 6A to 6C  are partial side cross-sectional diagrams showing a nozzle forming substrate to which a liquid-philic agent has been applied; 
         FIGS. 7A and 7B  are partial side cross-sectional diagrams showing a nozzle forming substrate to which a liquid-repelling agent has been applied; and 
         FIG. 8  is a partial side cross-sectional diagram of a nozzle plate in a case where the step of removing the liquid-repelling agent is omitted. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     General Composition of Inkjet Recording Apparatus 
       FIG. 1  is a general schematic drawing of an inkjet recording apparatus which forms an image forming apparatus according to the present invention. As shown in  FIG. 1 , the inkjet recording apparatus  10  comprises: a printing unit  12  having a plurality of print heads  12 K,  12 C,  12 M, and  12 Y for ink colors of black (K), cyan (C), magenta (M), and yellow (Y), respectively; an ink storing and loading unit  14  for storing inks of K, C, M and Y to be supplied to the print heads  12 K,  12 C,  12 M, and  12 Y; a paper supply unit  18  for supplying recording paper  16 ; a decurling unit  20  for removing curl in the recording paper  16 ; a suction belt conveyance unit  22  disposed facing the nozzle face (ink-droplet ejection face) of the print unit  12 , for conveying the recording paper  16  while keeping the recording paper  16  flat; a print determination unit  24  for reading the printed result produced by the printing unit  12 ; and a paper output unit  26  for outputting image-printed recording paper (printed matter) to the exterior. 
     In  FIG. 1 , a magazine for rolled paper (continuous paper) is shown as an embodiment of the paper supply unit  18 ; however, a plurality of magazines with papers of different paper width and quality may be jointly provided. Moreover, papers may be supplied in cassettes that contain cut papers loaded in layers and that are used jointly or in lieu of magazines for rolled papers. 
     In the case of a configuration in which roll paper is used, a cutter  28  is provided as shown in  FIG. 1 , and the roll paper is cut to a desired size by the cutter  28 . The cutter  28  has a stationary blade  28 A, whose length is not less than the width of the conveyor pathway of the recording paper  16 , and a round blade  28 B, which moves along the stationary blade  28 A. The stationary blade  28 A is disposed on the reverse side of the printed surface of the recording paper  16 , and the round blade  28 B is disposed on the printed surface side across the conveyance path. When cut paper is used, the cutter  28  is not required. 
     In the case of a configuration in which a plurality of types of recording paper can be used, it is preferable that an information recording medium such as a bar code and a wireless tag containing information about the type of paper is attached to the magazine, and by reading the information contained in the information recording medium with a predetermined reading device, the type of paper to be used is automatically determined, and ink-droplet ejection is controlled so that the ink-droplets are ejected in an appropriate manner in accordance with the type of paper. 
     The recording paper  16  delivered from the paper supply unit  18  retains curl due to having been loaded in the magazine. In order to remove the curl, heat is applied to the recording paper  16  in the decurling unit  20  by a heating drum  30  in the direction opposite to the curl direction in the magazine. At this time, the heating temperature is preferably controlled in such a manner that the recording paper  16  has a curl in which the surface on which the print is to be made is slightly rounded in the outward direction. 
     After decurling, the cut recording paper  16  is delivered to the suction belt conveyance unit  22 . The suction belt conveyance unit  22  has a configuration in which an endless belt  33  is set around rollers  31  and  32  so that the portion of the endless belt  33  facing at least the nozzle face of the print unit  12  and the sensor face of the print determination unit  24  forms a plane. 
     The belt  33  has a width that is greater than the width of the recording paper  16 , and a plurality of suction restrictors (not shown) are formed on the belt surface. A suction chamber  34  is disposed in a position facing the sensor surface of the print determination unit  24  and the nozzle surface of the printing unit  12  on the interior side of the belt  33 , which is set around the rollers  31  and  32 , as shown in  FIG. 1 ; and a negative pressure is generated by sucking air from the suction chamber  34  by means of a fan  35 , thereby the recording paper  16  on the belt  33  is held by suction. 
     The belt  33  is driven in the clockwise direction in  FIG. 1  by the motive force of a motor (not shown) being transmitted to at least one of the rollers  31  and  32 , which the belt  33  is set around, and the recording paper  16  held on the belt  33  is conveyed from left to right in  FIG. 1 . 
     Since ink adheres to the belt  33  when a marginless print job or the like is performed, a belt-cleaning unit  36  is disposed in a predetermined position (a suitable position outside the printing area) on the exterior side of the belt  33 . Although the details of the configuration of the belt-cleaning unit  36  are not shown, embodiments thereof include a configuration in which the belt  33  is nipped with a brush roller and a water absorbent roller, an air blow configuration in which clean air is blown onto the belt  33 , or a combination of these. In the case of the configuration in which the belt  33  is nipped with the cleaning roller, it is preferable to make the linear velocity of the cleaning roller different to that of the belt  33 , in order to improve the cleaning effect. 
     Instead of the suction belt conveyance unit  22 , it might also be possible to use a roller nip conveyance mechanism, but since the printing area passes through the roller nip, the printed surface of the paper makes contact with the rollers immediately after printing, and hence smearing of the image is liable to occur. Therefore, the suction belt conveyance mechanism in which nothing comes into contact with the image surface in the printing area is preferable. 
     A heating fan  40  is provided on the upstream side of the print unit  12  in the paper conveyance path formed by the suction belt conveyance unit  22 . This heating fan  40  blows heated air onto the recording paper  16  before printing, and thereby heats up the recording paper  16 . Heating the recording paper  16  before printing means that the ink will dry more readily after landing on the paper. 
     The print unit  12  is a so-called “full line head” in which a line head having a length corresponding to the maximum paper width is arranged in a direction (main scanning direction) that is perpendicular to the paper conveyance direction (sub-scanning direction). The print heads  12 K,  12 C,  12 M and  12 Y forming the print unit  12  are constituted by line heads in which a plurality of ink ejection ports (nozzles) are arranged through a length exceeding at least one edge of the maximum size recording paper  16  intended for use with the inkjet recording apparatus  10 . 
     The print heads  12 K,  12 C,  12 M, and  12 Y corresponding to respective ink colors are disposed in the order, black (K), cyan (C), magenta (M) and yellow (Y), from the upstream side (left-hand side in  FIG. 1 ), following the direction of conveyance of the recording paper  16  (the paper conveyance direction). A color image can be formed on the recording paper  16  by ejecting the inks from the print heads  12 K,  12 C,  12 M, and  12 Y, respectively, onto the recording paper  16  while conveying the recording paper  16 . 
     The print unit  12 , in which the full-line heads covering the entire width of the paper are thus provided for the respective ink colors, can record an image over the entire surface of the recording paper  16  by performing the action of moving the recording paper  16  and the print unit  12  relative to each other in the paper conveyance direction (sub-scanning direction) just once (in other words, by means of a single sub-scan). Higher-speed printing is thereby made possible and productivity can be improved in comparison with a shuttle type head configuration in which a print head moves reciprocally in the main scanning direction. 
     Although a configuration with the KCMY four standard colors is described in the present embodiment, the combinations of the ink colors and the number of colors are not limited to these, and light and/or dark inks can be added as required. For example, a configuration is possible in which print heads for ejecting light-colored inks such as light cyan and light magenta are added. 
     As shown in  FIG. 1 , the ink storing and loading unit  14  has ink tanks for storing the inks of the colors corresponding to the respective print heads  12 K,  12 C,  12 M, and  12 Y, and the respective tanks are connected to the print heads  12 K,  12 C,  12 M, and,  12 Y by means of channels (not shown). The ink storing and loading unit  14  has a warning device (for example, a display device or an alarm sound generator and the like) for warning when the remaining amount of any ink is low, and has a mechanism for preventing loading errors among the colors. 
     The print determination unit  24  has an image sensor for capturing an image of the ink-droplet deposition result of the printing unit  12 , and functions as a device to check for ejection defects such as clogs of the nozzles in the printing unit  12  from the ink-droplet deposition results evaluated by the image sensor (line sensor). 
     The print determination unit  24  of the present embodiment is configured with at least a line sensor having rows of photoelectric transducing elements with a width that is greater than the ink-droplet ejection width (image recording width) of the print heads  12 K,  12 C,  12 M, and  12 Y. This line sensor has a color separation line CCD sensor including a red (R) sensor row composed of photoelectric transducing elements (pixels) arranged in a line provided with an R filter, a green (G) sensor row with a G filter, and a blue (B) sensor row with a B filter. Instead of a line sensor, it is possible to use an area sensor composed of photoelectric transducing elements which are arranged two-dimensionally. 
     The print determination unit  24  reads a test pattern image printed by the print heads  12 K,  12 C,  12 M, and  12 Y for the respective colors, and the ejection of each head is determined. The ejection determination includes the presence of the ejection, measurement of the dot size, and measurement of the dot deposition position. 
     A post-drying unit  42  is disposed following the print determination unit  24 . The post-drying unit  42  is a device to dry the printed image surface, and includes a heating fan, for example. It is preferable to avoid contact with the printed surface until the printed ink dries, and a device that blows heated air onto the printed surface is preferable. 
     In cases in which printing is performed with dye-based ink on porous paper, blocking the pores of the paper by the application of pressure prevents the ink from coming contact with ozone and other substance that cause dye molecules to break down, and has the effect of increasing the durability of the print. 
     A heating/pressurizing unit  44  is disposed following the post-drying unit  42 . The heating/pressurizing unit  44  is a device to control the glossiness of the image surface, and the image surface is pressed with a pressure roller  45  having a predetermined uneven surface shape while the image surface is heated, and the uneven shape is transferred to the image surface. 
     The printed matter generated in this manner is output from the paper output unit  26 . The target print (i.e., the result of printing the target image) and the test print are preferably output separately. In the inkjet recording apparatus  10 , a sorting device (not shown) is provided for switching the outputting pathways in order to sort the printed matter with the target print and the printed matter with the test print, and to send them to paper output units  26 A and  26 B, respectively. When the target print and the test print are simultaneously formed in parallel on the same large sheet of paper, the test print portion is cut and separated by a cutter (second cutter)  48 . The cutter  48  is disposed directly in front of the paper output unit  26 , and is used for cutting the test print portion from the target print portion when a test print has been performed in the blank portion of the target print. The structure of the cutter  48  is the same as the first cutter  28  described above, and has a stationary blade  48 A and a round blade  48 B. 
     Although not shown in the drawing, the paper output unit  26 A for the target prints is provided with a sorter for collecting prints according to print orders. 
     Structure of Print Head 
     Next, the structure of a print head is described. The print heads  12 K,  12 M,  12 C, and  12 Y of the respective ink colors have the same structure, and a reference numeral  50  is hereinafter designated to any of the print heads. 
       FIG. 2  is a perspective plan view showing an embodiment of the configuration of the head  50 .  FIG. 3  is a cross-sectional view taken along line  3 - 3  in  FIG. 2 , showing the inner structure of one of liquid droplet ejection elements (an ink chamber unit for one nozzle  51 ). 
     In order to maximize the resolution of the dots printed on the surface of the recording paper  16 , the nozzle pitch in the head  50  should be minimized. As shown in  FIG. 2 , the head  50  according to the present embodiment has a structure in which a plurality of ink chamber units (droplet ejection elements)  53 , each having a nozzle  51  forming an ink ejection port, a pressure chamber  152  corresponding to the nozzle  51 , and the like, are disposed two-dimensionally in the form of a staggered matrix, and hence the effective nozzle interval (the projected nozzle pitch) as projected in the lengthwise direction of the head (the direction perpendicular to the paper conveyance direction) is reduced and high nozzle density is achieved. 
     As shown in  FIG. 2 , the planar shape of the pressure chamber  52  provided for each nozzle  51  is substantially a square, and the nozzle  51  and an inlet of supplied ink (supply port)  54  are disposed in both comers on a diagonal line of the square. 
     As shown in  FIG. 3 , the nozzle surface (ink ejection surface)  50 A of the print head  50  is constituted by a nozzle plate  60  in which the nozzles (nozzle orifices)  51  are formed. The method of manufacturing the nozzle plate  60  is described later. 
     Furthermore, each pressure chamber  52  is connected through a supply opening  54  to a common flow channel  55 . The common flow channel  55  is connected to an ink tank (not shown), which is a base tank that supplies ink, and the ink supplied from the ink tank is delivered through the common flow channel  55  to the pressure chambers  52 . 
     An actuator  58  provided with an individual electrode  57  is joined to a diaphragm (common electrode)  56  which forms the upper face of each pressure chamber  52 , and the actuator  58  is deformed when a drive voltage is supplied to the individual electrode  57  and the common electrode  56 , and the volume of the pressure chamber  52  is changed, thereby causing ink to be ejected from the nozzle  51 . The actuator  58  is preferably a piezoelectric element. When ink is ejected, new ink is supplied to the pressure chamber  52  from the common flow channel  55  through the supply port  54 . 
     As shown in  FIG. 4 , the plurality of ink chamber units  53  having this structure are composed in a lattice arrangement, based on a fixed arrangement pattern having a row direction which coincides with the main scanning direction, and a column direction which, rather than being perpendicular to the main scanning direction, is inclined at a fixed angle of θ with respect to the main scanning direction. By adopting a structure in which a plurality of ink chamber units  53  are arranged at a uniform pitch d in a direction having an angle θ with respect to the main scanning direction, the pitch P of the nozzles projected so as to align in the main scanning direction is d×cos θ. 
     More specifically, the arrangement can be treated equivalently to one in which the respective nozzles  51  are arranged in a linear fashion at uniform pitch P, in the main scanning direction. By means of this composition, it is possible to achieve a nozzle composition of high density, in which the nozzle columns projected to align in the main scanning direction reach a total of 2400 per inch (2400 nozzles per inch). 
     In a full-line head comprising rows of nozzles that have a length corresponding to the entire width of the image recordable width, the “main scanning” is defined as printing one line or one strip in the width direction of the recording paper (the direction perpendicular to the conveyance direction of the recording paper) by driving the nozzles in one of the following ways: (1) simultaneously driving all the nozzles; (2) sequentially driving the nozzles from one side toward the other; and (3) dividing the nozzles into blocks and sequentially driving the nozzles from one side toward the other in each of the blocks. 
     In particular, when the nozzles  51  arranged in a matrix such as that shown in  FIG. 4  are driven, the main scanning according to the above-described (3) is preferred. More specifically, the nozzles  51 - 11 ,  51 - 12 ,  51 - 13 ,  51 - 14 ,  51 - 15  and  51 - 16  are treated as a block (additionally; the nozzles  51 - 21 ,  51 - 22 , . . . ,  51 - 26  are treated as another block; the nozzles  51 - 31 ,  51 - 32 , . . . ,  51 - 36  are treated as another block; . . . ); and one line is printed in the width direction of the recording paper  16  by sequentially driving the nozzles  51 - 11 ,  51 - 12 , . . . ,  51 - 16  in accordance with the conveyance velocity of the recording paper  16 . 
     On the other hand, “sub-scanning” is defined as to repeatedly perform printing of one line (a line formed of a row of dots, or a line formed of a plurality of rows of dots) formed by the main scanning, while moving the full-line head and the recording paper relatively to each other. 
     According to the present invention, the arrangement of the nozzles is not limited to that of the embodiment illustrated. Moreover, in the present embodiment, a method is employed wherein an ink droplet is ejected by means of the deformation of the actuator  58 , which is, typically, a piezoelectric element, but in implementing the present invention, the method used for ejecting ink is not limited in particular, and instead of a piezo jet method, it is also possible to apply various other types of methods, such as a thermal jet method, wherein the ink is heated and bubbles are caused to form therein, by means of a heat generating body, such as a heater, ink droplets being ejected by means of the pressure of these bubbles. 
     Method for Manufacturing Nozzle Plate 
       FIGS. 5A to 5E  are illustrative diagrams showing steps of manufacturing a nozzle plate  60 . Below the method of manufacturing a nozzle plate  60  is described with reference to these diagrams. 
     Firstly, as shown in  FIG. 5A , preliminary holes  64 , which are larger than the nozzle orifices (nozzles)  51 , are formed by press forming, or the like, at the nozzle orifice forming positions in a nozzle forming substrate  62  made of stainless steel, nickel, resin, or the like. For example, the thickness of the nozzle forming substrate  62  is 50 μm to 100 μm, and the diameter of the preliminary holes  64  is 100 μm. 
     Next, as shown in  FIG. 5B , a liquid-philic agent is applied to the whole surface of the nozzle forming substrate  62  and solidified by drying, or the like, thereby forming a liquid-philic film  66  on the front and rear surfaces of the nozzle forming substrate  62 , and the preliminary holes  64 . Desirably, the liquid-philic film  66  in the preliminary holes  64  is formed so as to completely fill the preliminary holes  64 , as shown in  FIG. 5B . Furthermore, as shown in  FIGS. 6A and 6B , it is also possible to form the liquid-philic film  66  in such a manner that, as well as being disposed on the inner walls of the preliminary holes  64 , the liquid-philic film  66  partially fills each preliminary hole  64 . In this case, the thickness of the liquid-philic film  66  formed on the inner walls of the preliminary holes  64  is designed in such a manner that the diameter of the holes in the portion where the liquid-philic film  66  has been formed on the inner walls of the preliminary holes  64  is smaller than the diameter of the nozzle orifices  51  which are formed in a subsequent processing step. Desirably, the thickness of the liquid-philic film  66  formed on the inner walls of the preliminary holes  64  of the nozzle forming substrate  62  is 1 μm or above, taking account of the accuracy of the subsequent processing steps. If the preliminary holes  64  are in an open state as shown in  FIG. 6C , rather than being blocked off by the liquid-philic film  66 , then the liquid-philic agent is reapplied another time, or a viscosity enhancer is added to the liquid-philic agent, thereby making at least a portion of each preliminary hole  64  becomes blocked off by the liquid-philic film  66 . 
     The liquid-philic agent is, for example, PHEMA (polyhydroxyethyl methacrylate), polysilazane, or a high-molecular-weight polymer containing silicon (Si) or silica (SiO 2 ). The method of applying the liquid-philic agent is desirably a dipping method, and alternatively, vapor deposition, spraying, bar coating, spin coating, or the like, may also be used. 
     In the present embodiment, a case where the liquid-philic film  66  is formed in the preliminary holes  64  and on the front and rear surfaces of the nozzle forming substrate  62  is described as a desirable mode, but the implementation of the present invention is not limited to this, provided that the liquid-philic film  66  is formed at least in the preliminary holes  64 , as described above. If the liquid-philic film  66  is formed on the surface on the ink droplet ejection side (ink ejection surface)  62 A of the nozzle forming substrate  62 , then the formation of the liquid-philic film  66  is facilitated in comparison with a case where the liquid-philic film  66  is formed in the preliminary holes  64  alone. Furthermore, if the liquid-philic film  66  is formed on the rear surface on the opposite side to the ink ejection surface  62 A, as in the present embodiment, then the formation of the liquid-philic film  66  is further facilitated. 
     Next, as shown in  FIG. 5C , the liquid-philic film  66  formed on the ink ejection surface  62 A of the nozzle forming substrate  62  is removed by grinding. The step of removing the liquid-philic film  66  is performed in order to prevent non-uniformities in the thickness of a liquid-repelling film  68 , which is formed in the next step (see  FIG. 5D ). 
     Furthermore, when removing the liquid-philic film  66 , it is also possible to roughen the ink ejection surface  62 A of the nozzle forming substrate  62  simultaneously, by grinding. This improves the adherence and the liquid repelling characteristics of the liquid-repelling film  68  formed in the next step. 
     Next, as shown in  FIG. 5D , a liquid-repelling agent is applied to the ink ejection surface  62 A of the nozzle forming substrate  62 , and solidified by drying, or the like, thereby forming the liquid-repelling film  68 . For example, the liquid-repelling agent is made of polytetrafluoroethylene (PTFE), or a high-molecular-weight polymer containing fluorine (F). The method of applying the liquid-repelling agent is adhesion, dipping, spraying, bar coating, spin coating, or the like. 
       FIGS. 7A and 7B  show embodiments of the application of the liquid-repelling agent in a case where the preliminary holes  64  are partially filled with the liquid-philic film  66  (see  FIGS. 6A and 6B ). In a case of this kind, the liquid-repelling film  68  may be formed by applying the liquid-repelling agent to the ink ejection surface  62 A side of the liquid-philic film  66  that fills the preliminary hole  64 , without forming any gap, as shown in  FIG. 7A , or by applying the liquid-repelling agent in such a manner that a cavity section  70  is formed on the ink ejection surface  62 A side of the liquid-philic film  66  that fills the preliminary holes  64 , as shown in  FIG. 7B . 
     Next, as shown in  FIG. 5E , the nozzle orifices  51  are formed through the portions of the preliminary holes  64  of the nozzle forming substrate  62  which have been filled with the liquid-philic film  66 . The diameter of the nozzle orifices  51  is, for example, approximately 30 μm. The method of processing the nozzle orifices  51  is, for example, laser processing, micro-drilling, ashing using metal masks, blasting, and the like. In the case of ashing, it is desirable to process the nozzle orifices  51  from the side of the ink ejection surface  62 A, which leads to good dimensional accuracy of the nozzle orifices  51 . In the laser processing and the micro-drilling, there is no limitation in particular to the direction in which the nozzle orifices  51  are formed. 
     In this way, it is possible to manufacture the nozzle plate  60  in which the surface on the ink droplet ejection side is covered with the liquid-repelling film  68 , while at the same time, the inner walls of the nozzle orifices  51  are covered with the liquid-philic film  66 . 
     In the above-described method of manufacturing the nozzle plate  60 , the liquid-philic film  66  is formed in the preliminary holes  64  of the nozzle forming substrate  62 , whereupon the liquid-repelling film  68  is formed on the ink ejection surface  62 A of the nozzle forming substrate  62 , and the nozzle orifices  51  having a smaller diameter than the preliminary holes  64  are formed in the portions of the preliminary holes  64  filled with the liquid-philic film  66 . In other words, by using the liquid-philic film  66  instead of resist, it is possible to manufacture the nozzle plate  60  in which the inner walls of the nozzle orifices  51  are covered with the liquid-philic film  66 , without providing an additional liquid-philic treatment onto the inner walls of the nozzle orifices  51 , and therefore the manufacturing steps are simplified. Furthermore, since no resist is used, then there is no occurrence of nozzle blockage as a result of residual resist inside the nozzle orifices  51 . 
     Whereas it is generally difficult to process nozzle orifices  51  of very fine diameter to a high degree of accuracy in a nozzle forming substrate  62  made of a metal, such as stainless steel, in the method of manufacturing the nozzle plate  60  according to the present invention, since the nozzle orifices  51  are formed after forming the liquid-philic film  66  on the preliminary holes  64  having a larger diameter than the nozzle orifices  51 , in the nozzle forming substrate  62 , then it is possible to form the nozzle orifices  51  of a very fine diameter, with a high degree of accuracy. 
     Furthermore, the liquid-philic film  66  formed on the rear surface of the nozzle plate  60  on the side reverse to the ink droplet ejection side, can be used as an adhesive agent when bonding the nozzle plate  60  to another plate member. More specifically, since the nozzle plate  60  can be bonded to the other plate member without using adhesive, then there is no occurrence of nozzle blockage caused by surplus adhesive of the kind that arises when adhesive is used. 
     In the present embodiment, the liquid-philic film  66  formed on the ink ejection surface  62 A of the nozzle forming substrate  62  is removed in the step shown in  FIG. 5C , but if the thickness of the liquid-repelling film  68  can be made uniform in the subsequent step at FIG.  5 D without removing the liquid-philic film  66 , then the step in  FIG. 5C  can be omitted.  FIG. 8  is a cross-sectional diagram showing a portion of a nozzle plate  60  manufactured in a case where the step in  FIG. 5C  is omitted. As shown in  FIG. 8 , in the nozzle plate  60  formed in the case where the step of removing the liquid-philic film  66  is omitted, the liquid-philic film  66  and the liquid-repelling film  68  are sequentially layered on the ink ejection surface  62 A of the nozzle forming substrate  62 . By omitting the step of removing the liquid-philic film  66  in this way, it is possible further to simplify the process of manufacturing the nozzle plate  60 . 
     It should be understood, however, that there is no intention to limit the invention to the specific forms disclosed, but on the contrary, the invention is to cover all modifications, alternate constructions and equivalents falling within the spirit and scope of the invention as expressed in the appended claims.