Patent Publication Number: US-6910760-B2

Title: Liquid discharge head and method for manufacturing recording head

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a liquid discharge head for recording on a recording medium by discharging liquid droplets, such as ink droplets. The invention also relates to the method of manufacture therefor. More particularly, the invention relates to a liquid discharge head that performs ink jet recording. 
     2. Related Background Art 
     The ink jet recording method is one of the so-called non-impact recording methods. The ink jet recording method is capable of performing high-speed recording, and the noises, which are generated at the time of recording, are as small as almost negligible. Also, the ink jet recording method makes it possible to record on various kinds of recording medium, and fix ink on a plain sheet without any particular treatment given thereto. Further, with this method, highly precise images can be obtained at lower costs. With these advantages, the ink jet recording method has been used not only as a printer serving as a peripheral device of a computer, but also, in recent years, it has been used rapidly and widely as recording means for a copying machine, facsimile equipment, a work processor, and the like. 
     As the ink discharge methods generally utilized for ink jet recording, there are the one that adopts electrothermal converting element, such as heater, as element for generating discharge energy used for discharging ink droplets, and the one that uses piezoelectric element, such as piezo-element. With either method, it is possible to control the discharge of ink droplets using electric signals. The principle of the ink discharge method that uses electrothermal converting element is that by the application of voltage to the electrothermal converting element, ink in the vicinity of the electrothermal converting element is boiled instantaneously to discharge ink at high speed by the abrupt development of bubble generated by the phase change of ink taking place as it is boiled. On the other hand, the principle of the ink discharge method that uses piezoelectric element is that by the application of voltage to the piezoelectric element, the piezoelectric element is displaced to discharge ink droplets by the pressure exerted when such displacement takes place. 
     Then, for the ink discharge method using the electrothermal converting element, there is no need for securing a large space for the arrangement of the discharge energy-generating element. Therefore, it has such advantages as to make the structure of the liquid discharge head simpler, and also, to make it easier to effectuate a higher integration of nozzles, among some others. On the other hand, this ink discharge method characteristically has weakness in that the heat and others, which are generated by the electrothermal converting element, are accumulated in the liquid discharge head to cause the volumes of flying ink droplets to vary; the cavitation resulting from bubble extinction may produce unfavorable effect on the electrothermal converting element; and the air dissolved into ink may become remaining bubbles in the liquid discharge head. Such weakness may exert unfavorable influence on the discharge characteristics of ink droplets or the quality of recorded images in some cases. 
     In order to solve these problems, there have been proposed the ink jet recording methods and ink discharge heads in the specifications of Japanese Patent Application Laid-Open No. 54-161935, Japanese Patent Application Laid-Open No. 61-185455, Japanese Patent Application Laid-Open No. 61-249768, and Japanese Patent Application Laid-Open No. 04-10941. In other words, the ink jet recording methods disclosed in the aforesaid specifications are structured so that bubbles generated by driving the electrothermal converting element by means of electric signals are communicated with the air outside. With the adoption of such ink jet recording method, it is attempted to stabilize the volumes of flying ink droplets. Thus, droplets each having extremely small amount of ink can be discharged at high speed, and the enhancement of durability of heater is attempted by eliminating the cavitation generated at the time of bubble extinction, among some other improvements that have been made possible. As a result, it becomes easier to obtain highly precise images in a better condition. In accordance with the specifications of the aforesaid Japanese Patent Applications, the structure arranged to enable bubbles to be communicated with the air outside is such that the shortest distance between the electrothermal converting element and discharge port is made significantly smaller than the conventional art. 
     Now, the description will be made of the conventional liquid discharge head of the kind. The conventional liquid discharge head is provided with an element base plate having the electrothermal converting element for discharging ink, and the orifice base plate bonded to the element base plate so as to form ink flow path. The orifice base plate is provided with plural discharge ports for discharging ink droplets; plural nozzles that enable ink to flow; and the ink supply chamber to supply ink to each of these nozzles. The nozzle is structured with the bubbling chamber where bubble is generated in ink retained therein by means of the electrothermal converting element, and the supply path for supplying ink to this bubbling chamber. For the element base plate, it is arranged to position the electrothermal converting element in the bubbling chamber. Also, there is arranged for the element base plate the supply port for supplying ink to the supply chamber from the backside of the main face adjacent to the orifice base plate. Then, for the orifice base plate, the discharge port is arranged in the position facing the electrothermal converting element on the element base plate. 
     For the conventional liquid discharge head structured as described above, ink is supplied from the supply port into the supply chamber along each of the nozzles, and filled in the bubbling chamber. Ink filled in the bubbling chamber is caused to fly in the direction almost orthogonal to the main surface of the element base plate by means of the bubble, which is generated when ink is given film boiling by the electrothermal converting element. Thus, ink is discharged from the discharge port as ink droplet. 
     Then, higher speed recording should be considered for the recording apparatus provided with the aforesaid liquid discharge head in order to attempt the higher quality output of images, the higher quality of recorded images, the output of higher resolution, and the like. To attain the high-speed recording, it has been attempted to increase the discharge frequency of ink droplets to fly from each of the nozzles of the liquid discharge head, that is, to increase the frequency of discharges, such as disclosed in the specifications of U.S. Pat. Nos. 4,882,595, and 6,158,843. 
     Particularly, in the specification of U.S. Pat. No. 6,158,843, the structure is proposed for the improvement of ink flow from the supply port to the supply path with the arrangement of the space that enables the ink flow path to be narrowed locally or with the arrangement of extruded-fluid resistive element in the vicinity of the supply port. 
     Nevertheless, in the conventional liquid discharge head described above, part of ink filled in the bubbling chamber is pushed back unavoidably to the supply path when ink droplet is discharged by the developed bubble in the bubbling chamber. As a result, the conventional liquid discharge head is encountered with the drawback that the discharge amount of ink droplet tends to be reduced along with the reduction of the volume of ink in the bubbling chamber. 
     Also, in the conventional liquid discharge head, part of pressure exerted on the developing bubble on the supply path side is allowed to escape to the supply path side or pressure loss takes place due to friction between the bubble and the inner walls of the bubbling chamber when part of ink filled in the bubbling chamber is pushed back to the supply path. As a result, the conventional liquid discharge head is encountered with a problem that the discharge speed of ink droplet is reduced along the reduction of bubble pressure. 
     Also, for the conventional liquid discharge head, there is a problem that the volume of small amount of ink filled in the bubbling chamber is caused to vary due to the bubble that is developed in the bubbling chamber, and therefore, the discharge amount of ink droplet is caused to vary accordingly. 
     SUMMARY OF THE INVENTION 
     Here, the present invention is designed to attempt higher discharge speed of liquid droplets, as well as to stabilize the discharge amount thereof. It is an object of the invention to provide a liquid discharge head for which the discharge efficiency of liquid droplets are enhanced, and also, to provide the method of manufacture therefor. 
     In order to achieve the aforesaid object, the liquid discharge head of the present invention comprises a discharge energy generating element for generating energy for discharging a liquid droplet; an element base plate provided with the discharge energy generating element on the main surface thereof; and an orifice base plate bonded to the main surface of the element base plate, being provided with a nozzle having a discharge port portion with a discharge port for discharging a liquid droplet, a bubbling chamber for generating bubble in liquid therein by the discharge energy generating element, and a supply path for supplying liquid to the bubbling chamber, and a supply chamber for supplying liquid to the nozzle. For this liquid discharge head, the bubbling chamber is formed by a first bubbling chamber communicated with the supply path with the main surface of the element base plate as the bottom face thereof for generating bubble in liquid therein by the discharge energy generating element, and also, a second bubbling chamber communicated with the first bubbling chamber, and the central axis of the lower face of the second bubbling chamber and the central axis of the upper face of the second bubbling chamber are in agreement in the direction perpendicular to the base plate, and the sectional area of the upper face with respect to the central axis of the second bubbling chamber is smaller than the sectional area of the lower face with respect to the central axis of the second bubbling chamber, and the sectional area in the direction toward the central axis is continuously changed from the lower face to the upper face of the second bubbling chamber, and on the circumferential portion of the upper face of the first bubbling chamber in parallel with the main surface of the element base plate, and in contact with the opening communicated with the second bubbling chamber, an extrusion is formed continuously to surround the opening in the direction toward the main face of the element base plate. 
     Also, for the liquid discharge head thus structured, the height, the width, or the sectional area of flow path in the nozzle is changed, and the structure is arranged so that the volume of ink is gradually reduced in the direction from the base plate to the discharge port. Then, the structure is arranged to provide such a configuration that in the vicinity of the discharge port, when liquid droplet flies, the flying liquid droplet flies vertically to the base plate, and also, to provide the function to straighten (rectify) the liquid flow. Also, when liquid is discharged, it is made possible to suppress the event that the liquid, which is filled in the bubbling chamber, is pushed out to the supply path side by the bubble, which is generated in the bubbling chamber. As a result, in accordance with this liquid discharge head, the occurrence of variation is suppressed in the discharge volumes of liquid droplets to be discharged, and the discharge volume is secured exactly. Also, for this liquid discharge head, when liquid droplet is discharged, the bubble, which is developed in the bubbling chamber, abuts the inner walls of the control portion in the bubbling chamber, which is formed by the portion having difference in level. As a result, the loss of pressure exerted by bubble can be suppressed. Therefore, in accordance with this liquid discharge head, it becomes possible to secure the bubble developed in the bubbling chamber in good condition sufficiently, hence enhancing the discharge speed of liquid droplet. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view schematically illustrates the entire structure of a liquid discharge head in accordance with the present invention. 
         FIG. 2  is a view that schematically shows the flow of liquid of a liquid discharge head in accordance with a three-opening model. 
         FIG. 3  is a view that schematically shows the liquid discharge head in accordance with an equivalent circuit. 
         FIG. 4  is a partially sectional perspective view that illustrates the structure having one heater and nozzle combined therein for a liquid discharge head in accordance with a first embodiment of the present invention. 
         FIG. 5  is a partially sectional perspective view that illustrates the structure having plural heaters and nozzles combined therein for the liquid discharge head in accordance with the first embodiment of the present invention. 
         FIG. 6  is a side sectional view that illustrates the structure having one heater and nozzle combined therein for the liquid discharge head in accordance with the first embodiment of the present invention. 
         FIG. 7  is a plan sectional view that illustrates the structure having one heater and nozzle combined therein for the liquid discharge head in accordance with the first embodiment of the present invention. 
         FIGS. 8A ,  8 B,  8 C,  8 D, and  8 E are perspective views that illustrate a method for manufacturing the liquid discharge head in accordance with the first embodiment of the present invention;  FIG. 8A  shows an element base plate;  FIG. 8B  illustrates the state where a lower resin layer and an upper resin layer are formed on the element base plate;  FIG. 8C , the state where a covering resin layer is formed;  FIG. 8D , the state where a supply port is formed; and  FIG. 8E , the state where the inner lower resin layer and upper resin layer are dissolved to flow out. 
         FIGS. 9A ,  9 B,  9 C,  9 D, and  9 E are first vertical-sectional views that illustrate each step for manufacturing the liquid discharge head in accordance with the first embodiment of the present invention;  FIG. 9A  shows the element base plate;  FIG. 9B  illustrates the state where the lower resin layer is formed on the element base plate;  FIG. 9C , where the upper resin layer is formed on the element base plate;  FIG. 9D , the state where a pattering formation is given to the upper resin layer formed on the element base plate; and  FIG. 9E , the state where a pattering formation is given to the upper resin layer formed on the element base plate. 
         FIGS. 10A ,  10 B,  10 C, and  10 D are second vertical-sectional views that illustrate each step for manufacturing the liquid discharge head in accordance with the first embodiment of the present invention;  FIG. 10A  shows the state where a resin covering layer is formed, which serves as the orifice base plate;  FIG. 10B , the state where the discharge port portion is formed;  FIG. 10C , the supply port is formed; and  FIG. 10D , the state where the inner lower resin layer and upper resin layer are dissolved to flow out for the completion of the liquid discharge head. 
         FIG. 11  is a view that shows the chemical formula to express the chemical changes of the upper resin layer and the lower layer by the irradiation of electron beam. 
         FIG. 12  shows the graphs of the absorption spectrum curves of the materials in the region of 210 to 330 nm of the lower resin layer and the upper resin layer. 
         FIG. 13  is a partially sectional perspective view that illustrates the structure having one heater and nozzle combined therein for a liquid discharge head in accordance with a second embodiment of the present invention. 
         FIG. 14  is a side sectional view that illustrates the structure having one heater and nozzle combined therein for the liquid discharge head in accordance with the second embodiment of the present invention. 
         FIG. 15  is a partially sectional perspective view that illustrates the structure having one heater and nozzle combined therein for a liquid discharge head in accordance with a third embodiment of the present invention. 
         FIG. 16  is a side sectional view that illustrates the structure having one heater and nozzle combined therein for the liquid discharge head in accordance with the third embodiment of the present invention. 
         FIGS. 17A and 17B  are partially sectional perspective views that illustrate a structure having one heater and nozzle combined therein for a liquid discharge head in accordance with a fourth embodiment of the present invention;  FIG. 17A  shows a nozzle of the first nozzle array;  FIG. 17B , a nozzle of the second nozzle array. 
         FIGS. 18A ,  18 B,  18 C,  18 D, and  18 E are first vertical-sectional views that illustrate each step for manufacturing the liquid discharge head in accordance with the fourth invention;  FIG. 18A  shows the element base plate;  FIG. 18B  illustrates the state where the lower resin layer is formed on the element base plate;  FIG. 18C , where the upper resin layer is formed on the element base plate;  FIG. 18D , the state where a pattering formation is given to the upper resin layer formed on the element base plate and an inclination is formed on the side face; and  FIG. 18E , the state where a pattering formation is given to the upper resin layer formed on the element base plate. 
         FIGS. 19A ,  19 B,  19 C, and  19 D are second vertical-sectional views that illustrate each step for manufacturing the liquid discharge head in accordance with the fourth embodiment of the present invention;  FIG. 19A  shows the state where a resin covering layer is formed, which serves as the orifice base plate;  FIG. 19B , the state where the discharge port portion is formed;  FIG. 19C , the supply port is formed; and  FIG. 19D , the state where the inner lower resin layer and upper resin layer are dissolved to flow out for the completion of the liquid discharge head. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hereinafter, with reference to the accompanying drawings, the description will be made of the specific embodiments of the liquid discharge head that discharges liquid droplets, such as ink, in accordance with the present invention. 
     At first, a liquid discharge head of the present embodiment will be described briefly. The liquid discharge head of the present embodiment is provided, in particular, with means for generating thermal energy as energy to be utilized for discharging liquid ink among those of ink jet recording methods. The liquid discharge head adopts the method whereby to generate changes in the state of ink by the application of thermal energy thus generated. By use of this method, it becomes possible to attain recording characters, images, and the like in high density and high precision. Particularly, in accordance with the present embodiment, heat-generating resistive element is used as means for generating thermal energy, and with the heat-generating resistive element, ink is heated. Then, ink is discharged by the utilization of pressure exerted by the bubble, which is generated when ink is given film boiling. 
     (First Embodiment) 
     Although details will be described later, the recording head  1  of a first embodiment is structured, as shown in  FIG. 1 , with the partition walls extended from the discharge port to the vicinity of supply port in order to form the nozzle that serves as the ink flow path individually for each of the plural heaters serving as heat-generating resistive element. For the liquid discharge head of the kind, the ink discharge means, to which the ink jet recording method is applicable, is provided as disclosed in the specifications of Japanese Patent Application Laid-Open Nos. 04-10940 and 04-10941. Then, the bubble, which is generated at the time of ink discharge, is communicated with the air outside through the discharge port. 
     Then, the liquid discharge head  1  is provided with a first nozzle array  16  in which plural heaters and plural nozzles are provided, and the longitudinal direction of each nozzle is arranged in parallel, and a second nozzle array  17  arranged in the position facing the first nozzle array with the supply chamber between them. The first and second nozzle arrays  16  and  17  are formed so that any one of adjacent nozzles has an interval of 600 dpi pitch, respectively. Also, each nozzle  17  of the second nozzle array is arranged with respect to the first nozzle array  16  so that each pitch of the adjacent nozzles is displaced by ½ pitch from each other. 
     Here, the description will be made briefly of the concept with which to optimize the liquid discharge head  1 , which is provided with the first and second nozzle arrays  16  and  17  having plural heaters and plural nozzles arranged in high density. 
     Generally, as the physical quantity that may exert influence on the discharge characteristics of a liquid discharge head, inertance (inertial force) and resistance (viscosity resistance) act greatly in each nozzle of those provided in the plural number. The kinetic equation of the incompressible fluid that moves in the flow path of any configuration is expressed by the following two formulas:
 
Δ· v =0 (continuous equation)  (1)
 
(∂ v/∂t )+( v ·Δ) v =−Δ( P /ρ)+(μ/ρ)Δ 2   v+f  (navier-stokes equation)  (2)
 
     Given the first and second equations as those having sufficiently small terms against fluid and viscosity, and having no external force, either, and the following approximation is obtainable:
 
Δ 2 P=0  (3)
 
Then, the pressure can be expressed by use of harmonic function.
 
     In the case of the liquid discharge head, expression is possible in accordance with the three-opening model shown in  FIG. 2 , and the equivalent circuit shown in FIG.  3 . 
     The inertance is defined as the “difficulty in movement” when stationary fluid starts to move abruptly. In the electrical expression, it acts similarly as the inductance that impedes the changes of current. In a case of the spring mass model, it is equivalent to the weight (mass). 
     If the inertance is expressed in an equation, it is represented as follows by the ratio to the time differential of second order of the volume V of fluid, that is, the time differential of the flow rate F (=ΔV/Δt), when the pressure difference is given to the opening:
 
(Δ 2   V/Δt   2 )=(Δ F/Δt )=(1 /A )× P   (4)
 
where the A is inertance.
 
     For example, on the assumption that a pseudo-duct flow path of pipe type is taken, giving the density as ρ, the length as L, and the sectional area as So, the inertance Ao of this one-dimensional pseudo-duct flow path is expressed as follows:
 
 Ao=ρ×L/So. 
 
Thus, it is understandable that it is proportional to the length of the flow path, and is inversely proportional to the sectional area.
 
     On the basis of the equivalent circuit shown in  FIG. 3 , it is possible to estimate and analyze the discharge characteristics of a liquid discharge head as a model. 
     In accordance with the liquid discharge head of the present invention, the discharge phenomenon is taken as the phenomenon in which the inertial flow is transited to the flow of viscosity. Particularly, at the early stage of bubbling generated by use of heater in the bubbling chamber, the inertial flow is main, and on the contrary, in the later period of discharge (that is, during the period in which the meniscus formed at the discharge port begins to move to the ink flow path side, and returns when ink is filled up to the opening end face of the discharge port by means of capillary phenomenon), the flow of viscosity becomes main. At this juncture, from the aforesaid relational equation, the inertance contributes greatly to the discharge characteristics, the discharge volume and discharge speed, in particular, at the early stage of bubbling owing to the quantitative relations thereof, and the amount of resistance (viscosity resistance) greatly contributes to the discharge characteristics, the time required for refilling ink (hereinafter, referred to as refilling time), in particularly, in the later period of discharge. 
     Here, the resistance (viscosity resistance) is described by the equation 1, and the stationary Stokes&#39; method expressed as follows:
 
ΔP=ηΔ 2 μ  (5)
 
Hence obtaining the viscosity resistance B. Also, in the later period of discharge, the meniscus is generated in the vicinity of the discharge port as shown by the model shown in  FIG. 2 , and mainly by the suction exerted by capillary force, the flow of ink takes place. Therefore, it can be approximated by use of a two-opening model (one-dimensional flow model).
 
     In other words, it is possible to obtain such approximation by the Poiseuille&#39;s equation 6 that describes the viscous fluid as given below.
 
(Δ V/Δt )=(1/ G )×(1/η){(Δ P/Δx )× S ( x )}  (6)
 
Here, the G is a form factor. Also, the fluid that flows along any pressure difference causes the viscosity resistance B. Therefore, it can be obtained by the following equation 7:
 
 B=∫   0   L {( G ×η)/ S ( x )}Δ x   (7)
 
     Now, as understandable from the equation 7, if a duct flow path of pipe type is assumed with the density being given as ρ, the length as L, and the sectional area as So, the resistance (viscosity resistance) is expressed as follows:
 
 B= 8 η×L /(π× So   2 )  (8)
 
Thus, it is understandable that it is approximately proportional to the length of the nozzle, and is inversely proportional to the square of the sectional area of the nozzle.
 
     As described above, in order to improve any one of the discharge characteristics of the liquid discharge head, the discharge speed, the discharge volume of ink droplet, the refilling time, in particular, it is prerequisite from the relations of the inertance that the amount of inertance from the heat to the discharge port side is made as larger as possible than the amount of inertance from the heater to the supply port side, and that the resistance in the nozzle is made small. 
     With respect to the view points described above, and to the objective that plural heaters and plural nozzles should be arranged in high density as well, the liquid discharge head of the present invention is the one, which is capable of satisfying both of them. 
     Next, with reference to the accompanying drawings, the description will be made of the specific structure of the liquid discharge head in accordance with the present embodiment. 
     As shown in  FIG. 4  to  FIG. 7 , the liquid discharge head is provided with the element base plate  11  having heaters  20  serving as plural discharge energy-generating elements, which are the heat-generating resistive elements, and the orifice base plate  12 , which forms plural ink flow paths by being laminated and bonded to the main surface of the element base plate  11 . 
     The element base plate  11  is formed by, for example, glass, ceramics, resin, metal, or the like, which is generally formed by Si. 
     On the main surface of the element base plate  11 , there are arranged for each of the ink flow paths, the heater  20 , electrodes (not shown) that apply voltage to the heater  20 , and wiring (not shown), which is connected with the electrodes, and arranged respectively by a predetermined wiring pattern. Also, on the main surface of the element base plate  11 , the insulating film  21 , which improves the dispersion of accumulated heat, is provided to cover the heater  20  (see FIG.  8 A). Also, on the main surface of the element base plate  11 , the protection film  22 , which protects the main surface from the cavitation to be generated at the time of bubble extinction, is provided to cover the insulating film  21  (see FIG.  8 A). 
     The orifice base plate  12  is formed by resin material in a thickness of approximately 30 μm. As shown in FIG.  4  and  FIG. 5 , the orifice plate  12  is provided with plural discharge port portions  26  for discharging ink droplets; plural nozzles  27 , in which ink flows, respectively; and the supply chamber  28  that supplies ink to each of the nozzles  27 . The nozzle  27  is provided with the discharge port portion  26  having discharge port  26   a  for discharging ink droplets; the bubbling chamber  31  that enable liquid in it to be bubbled by use of the heater  20  serving as the discharge energy-generating element; and the supply path  32  for supply liquid to the bubbling chamber  31 . 
     The bubbling chamber  31  is formed by a first bubbling chamber  31   a  communicated with the supply path  32  as the bottom face of the main surface of the element base plate  11  for generating bubble in liquid in the bubbling chamber  31   a  by use of the heater  20 , and a second bubbling chamber  31   b  communicated with the opening on the upper face of the first bubbling chamber  31   a , which is in parallel to the main surface of the element base plate  11 , and in which the bubble thus generated is developed. Then, for the circumferential portion on the upper face of the first bubbling chamber  31   a , which is in parallel to the main surface of the element base plate  11  and in contact with the opening communicated with the second bubbling chamber  31   b , an extrusion  33  is formed continuously to surround the opening in the direction toward the main surface of the element base plate  11 . 
     The discharge port portion  26  is arranged to be communicated with the opening on the upper face of the second bubbling chamber  31   b , and a difference in level is provided between the side wall face of the discharge port portion  26  and the side wall face of the second bubbling chamber  31   b.    
     The discharge port  26   a  of the discharge port portion  26  is formed in the position facing the heater  20  provided for the element base plate  11 . Here, it is formed to be a circular hole having a diameter of approximately 15 μm. In this respect, the discharge port  26   a  may be configured almost in the form of a star having spokes as required in terms of the discharge characteristics. 
     The second bubbling chamber  31   b  is formed to be a truncated cone, and the side wall thereof is contracted in the discharge port direction at an inclination of 10 to 45° to the plane orthogonal to the main surface of the element base plate. The upper face thereof is communicated with the opening of the discharge port portion  26  with a difference in level. 
     The first bubbling chamber  31   a  is on the extended line of the supply path  32 , and the bottom end thereof facing the discharge port  26  is formed to be almost rectangular. 
     Here, the nozzle  27  is formed so that the shortest distance HO between the main surface of the heater  20  in parallel to the main surface of the element base plate  11 , and the discharge port  26   a  is made to be 30 μm or less. 
     For the nozzles  27 , the upper face of the first bubbling chamber  31   a  in parallel to the main surface, and the upper face in parallel to the main surface of the supply path  32  adjacent to the bubbling chamber  31  are continuous up to the supply chamber  8  on one and the same plane. 
     For the circumferential portion of the upper face of the first bubbling chamber  31   a  in parallel with the main surface of the element base plate  11 , which is in contact with the opening communicated with the second bubbling chamber  31   b , there is the extrusion  33  formed to surround the opening in the direction toward the main surface of the element base plate  11 . This extrusion is provided with the function as a control portion to control ink to be caused to flow by bubble in the bubbling chamber  31 . 
     It is formed to communicate one end of the supply path  32  the bubbling chamber  31 , and the other end with the supply chamber  28 . 
     In this way, the extrusion  33  that has function as the control portion is provided for the nozzle  27 . Thus, the height to the main surface of the portion of the element base plate  11  across one end of the supply path  32  adjacent to the first bubbling chamber  31   a  is formed to be lower than the height of the other end of the supply path  32  adjacent to the supply chamber  28 . Thus, with the provision of the extrusion  33  for the nozzle  27 , it is made possible to form the sectional area of the ink flow path from the one end of the supply path  32  adjacent to the first bubbling chamber  31   a  to the first bubbling chamber  31   a  to be smaller than the sectional area of the other flow path. 
     Also, as shown in FIG.  4  and  FIG. 7 , the width of the nozzle  27 , which is orthogonal to the ink flow direction on the face of the flow path in parallel to the main surface of the element base plate  11 , is configured to be in the straight form substantially equal over the range from the supply chamber  28  to the bubbling chamber  31 . Also, the inner wall faces of the nozzle  27  facing the main surface of the element base plate  11  are formed to be in parallel with the main surface of the element base plate  11  with the exception of the extrusion  33  over the range from the supply chamber  28  to the bubbling chamber  31 . Here, for the nozzle  27 , the height of the plane of the extrusion  33  facing the main surface of the element base plate  11  is formed to be approximately 10 μm, for example, and the height of the plane of the supply chamber  28  facing the main surface of the element base plate  11  is formed to be approximately 15 μm. Therefore, the height of the extrusion  33  is approximately 5 μm. 
     Also, for the back face of the main surface of the element base plate  11  adjacent to the orifice base plate  12 , the supply port  36  is provided for supplying ink to the supply chamber  28  from this back face side. 
     Also, as shown in FIG.  4  and  FIG. 5 , there are arranged in the supply chamber  28 , the column type nozzle filters  38 , which stand across the element base plate  11  and the orifice base plate  12  per nozzle  27  in each position adjacent to the supply port  36  for filtering the dust particles in ink. The nozzle filter  38  is arranged in the position away from the supply port by approximately 20 μm, for example. Also, the gap between each of the nozzles  38  in the supply chamber  28  is approximately 10 μm, for example. By use of the filter  38 , it becomes possible to prevent the supply path  38  and the discharge port  26  from being clogged by dust particles in order to assure operating discharges in good condition. 
     Now, the description will be made of the operation of discharging ink droplets from the discharge port  26  of the liquid discharge head  1  structured as described above. 
     At first, for the liquid discharge head  1 , the ink, which is supplied from the supply port  36  into the supply chamber  28 , is supplied into each nozzle  27  of the first and second nozzle arrays  16 , and  17 , respectively. The ink, which is supplied to each nozzle  27 , flows along the supply path  32  to be filled in the bubbling chamber  31 . The ink, which is filled in the bubbling chamber  31 , is given film boiling by the heater  20 , and flies in the direction almost orthogonal to the main surface of the element base plate  11  by means of the developing pressure of bubble thus generated. Thus, it is discharged as ink droplet from the discharge port  26   a  of the discharge portion  26 . 
     When the ink, which is filled in the bubbling chamber  31 , is discharged by way of the second bubbling chamber  32   b  by the developing pressure of the bubble generated by the film boiling given by the heater  20  in the first bubbling chamber  31   a , the volume of ink is gradually reduced and the flow of ink is straightened (rectified) in the direction from the element base plate  11  toward the discharge port  26   a , because the second bubbling chamber  31   b  is configured to be truncated cone, and the the side walls thereof are contracted in the direction toward the discharge port at an inclination of 10 to 45° to the plane orthogonal to the main surface of the element base plate, and then, the upper face thereof is communicated with the opening of the discharge port  26  with a difference in level. Thus, in the vicinity of the discharge port  26   a , the liquid droplet flies, and the flying liquid droplet flies vertically to the base plate. 
     When the ink, which is filled in the bubbling chamber  31 , is discharged, part of ink in the bubbling chamber  31  is caused to flow to the supply path  32  side due to the pressure of bubble generated in the bubbling chamber  31 . In the liquid discharge head  1 , when part of ink in the bubbling chamber  31  flows to the supply path  32  side, the extrusion  33  acts as fluid resistance to the ink, which flows from the bubbling chamber  31  side to the supply chamber  28  side through the supply path  32 , because the flow passage of the supply path  32  is narrowed by the presence of the extrusion  33 . As a result, in the liquid discharge head  1 , the flow of ink filled in the bubbling chamber  31  to the supply path  32  side is suppressed by the extrusion  33 . In this manner, the reduction of the amount of ink in the bubbling chamber  31  is prevented, thus reliably securing the volume of ink discharge in good condition. The occurrence of variation in the discharge volumes of liquid droplets to be discharged from the discharge port is then suppressed, and the discharge volume is kept appropriately. 
     For the liquid discharge head  1 , given the inertance from the heater  20  to the discharge port  26  as A 1 , the inertance from the heater  20  to the supply port  36  as A 2 , and the inertance of the entire nozzle  27  as A 0 , it is possible to express the energy distribution ratio η to the discharge port  26  side of the head as follows:
 
η=( A   1   /A   0 )={ A   2 /( A   1   +A   2 )}  (9).
 
Also, the value of each inertance may be obtainable by solving the Laplace equation by use of a three-dimensional finite constituent method solver.
 
     From the aforesaid equation, the energy distribution ratio η to the discharge port  26  side of the head for the liquid discharge head  1  is 0.59. The liquid discharge head  1  is capable of maintaining the values of the discharge speed and volume of discharge at the same level as the conventional ones by keeping the energy distribution ratio η almost at the same value of the conventional liquid discharge head. Also, it is desirable to enable the energy distribution ratio η to satisfy the relations of 0.5&lt;η&lt;0.8. The liquid discharge head  1  is disabled to secure the discharge speed and discharge volume in good condition if the energy distribution ratio η is 0.5 or less, and ink does not flow in good condition if it is 0.8 or more. Then, refilling cannot be performed any longer. 
     Also, when dyestuff-black ink (the surface tension: 47.8×10 −3  N/m, and the viscosity: 1.8 cp, pH 9.8) is used as ink for the liquid discharge head  1 , it becomes possible to reduce the viscosity resistance value B in the nozzle  27  approximately by 40% as compared with the conventional liquid discharge head. The viscosity resistance value B may also be worked out by means of a three-dimensional constituent method solver, and with the establishment of the length of nozzle  27  and the sectional area of nozzle  27 , it is possible to calculate this value of resistance easily. 
     Therefore, the liquid discharge head  1  of the present embodiment becomes capable of making the discharge speed faster than that of the conventional liquid discharge head approximately by 40%. Hence, the response capability of discharge frequency of approximately 25 to 30 kHz can be materialized. 
     Now, with reference to  FIGS. 8A  to  8 E, and FIGS.  9 A to  9 E, and  FIGS. 10A  to  10 D, the brief description will be made of a method for manufacturing the liquid discharge head  1  thus structured. 
     The method for manufacturing the liquid discharge head  1  is completed through a first step of forming an element base plate  11 ; a second step of forming the upper resin layer  42  and lower resin layer  41 , respectively, to structure the ink flow path on the element base plate  11 ; a third step of forming the desired nozzle pattern on the upper resin layer  41 ; a fourth step of forming an inclination on the side face of the resin layer; and a fifth step of forming the desired nozzle pattern on the lower resin layer  42 . 
     Next, in accordance with the method for manufacturing the liquid discharge head  1 , a covering resin layer  43 , which serves as the orifice base plate  12 , is formed on the upper and lower resin layers  41  and  42  in a sixth step; the discharge port portion  26  is formed for the covering resin layer  43  in a seventh step; and the supply port  36  is formed on the element base plate  11  in an eighth step; and the upper and lower resin layers  41  and  42  are dissolved to flow out in a ninth step, thus manufacturing the liquid discharge head  1  through these steps. 
     As shown in FIG.  8 A and  FIG. 9A , the first step is the formation process of the element base plate to form the element base plate  11  in such a manner that on the main surface of the Si chip, for example, plural heaters  20  and the predetermined wiring are provided by means of patterning process or the like in order to apply voltage to the heaters  20 ; an insulating film  21  is provided to cover the heaters  20  for the improvement of capability to disperse accumulated heat; and a protection film  22  is provided to cover the insulating film  21  in order to protect the main surface from the cavitation that occurs when the bubble extinction takes place. 
     As shown in  FIG. 8B ,  FIG. 9B , and  FIG. 9C , the second step is the coating process in which Deep-UV light (hereinafter referred to as DUV light), which is the ultraviolet rays the wavelength of which is 300 nm or less, is irradiated onto the element base plate  11  so as to enable the dissolvable lower resin layer  42  and upper resin layer  41  to be continued when bindings in the molecules are destroyed, and then, each of them is coated by means of spin-coating method. In this coating step, when the upper resin layer  41  is coated by use of the spin-coating method, it is arranged to prevent the lower resin layer  42  and the upper resin layer  41  from being dissolved with each other by using the resin material of thermal bridging type made available by the reaction of dehydrated condensation as the lower resin layer  42 . As the lower resin layer  42 , methyl methacrylate (MMA) and methacrylic acid (MAA) are radically polymerized to obtain polymerized binary polymer (P (MMA-MAA)=90:10), for example, and the liquid, which is obtainable by dissolving such polymer by cyclohexane solvent, is used. Also, for the upper resin layer  41 , the liquid, which is obtainable by dissolving polymethyl isopropenyl ketone (PMIPK) with cyclohexanone solvent, is used.  FIG. 11  is a view that shows the chemical reaction that forms the thermal-bridging film by the reaction of dehydrated condensation of the binary polymer (P (MMA-MAA)) used for the lower resin layer  42 . This reaction of dehydrated condensation makes it possible to form the bridging film having higher strength by heating at a temperature of 180 to 200° C. for a period of 30 minutes to 2 hours. Here, the bridging film is in the form of indissoluble solvent. However, by the irradiation of electron beam, such as DUV light, decomposing reaction as shown in  FIG. 11  occurs, and low molecular formation makes progress. Then, only the portion where the electron beam is irradiated becomes a dissoluble solvent. 
     As shown in FIG.  8 B and  FIG. 9D , the third step is the pattern formation process in which a filter is installed, as means for selecting wavelength, on the exposing device that irradiates DUV light, and cuts off the DUV light having the wavelength of less than 260 nm, and only the one having those of 260 nm or more is transmitted so as to enable the Near-UV light (hereinafter referred to as NUV) having the wavelength of around 260 to 330 nm to be irradiated onto the upper resin layer  41  to be exposed and developed for the formation of desired nozzle pattern thereon. In the third step, when the nozzle pattern is formed on the upper resin layer, there is the difference in sensitivity ratio of approximately 40:1 or more between the upper resin layer  41  and the lower resin layer  42  with respect to the NUV light having wavelength of around 260 to 330 nm. Therefore, the lower resin layer  42  is not exposed, and the P (MMA-MAA) of the lower resin layer  42  is not decomposed at all. Also, being the thermal bridging film, the lower resin layer  42  is not dissolved by developer, either, when the upper resin layer is developed. In this step, when development is performed, a step of forming a recessed portion  33 ′, which becomes the continuous extrusion  33  later, is executed together for the lower resin layer  42  on the circumference of the organic resin pattern that forms the second bubbling chamber  31   b  at that time.  FIG. 12  shows the absorption spectra of the materials of the lower resin layer  42  and the upper resin layer  41  in the region of 210 to 330 nm. 
     In the fourth step, as shown in FIG.  8 B and  FIG. 9D , the upper resin layer  41  is heated at a temperature of 140° C. for 5 to 20 minutes after the pattern formation, thus forming an inclination of 10 to 45° on the side face of the upper resin layer. This angle of inclination has interrelations with the pattern volume (shape and film thickness), and heating temperature and time, and control is possible to obtain a designated angle within the range of the aforesaid angles. 
     As shown in FIG.  8 B and  FIG. 9E , the fifth step is the pattern formation process in which the DUV light of wavelength 210 to 330 nm is irradiated using the aforesaid exposing device so as to enable the lower resin layer to be exposed and developed for the formation of desired nozzle pattern on the lower resin layer  42 . Further, the P (MMA-MAA) material used for the lower resin layer  42  has high resolution, and even in a thickness of approximately 5 to 20 μm, it is possible to form the trench structure having the angle of inclination of approximately 0 to 5° on the sidewalls thereof. Also, if required, it is possible to form more inclination on the sidewalls of the lower resin layer  42  by heating the resin layer  42  after patterning at a temperature of approximately 120 to 140° C. 
     The sixth step is the coating process in which as shown in  FIG. 10A , a transparent covering resin layer  43 , which becomes the orifice base plate  12 , is coated on the upper resin layer  41  and the lower resin layer  42  made dissolvable by the destruction of bridge binding in the molecules by the irradiation of DUV light. 
     In the seventh step, as shown in FIG.  8 C and  FIG. 10B , the UV light is irradiated onto the covering resin layer  43  using the exposing device to enable the portion corresponding to the discharge port portion  26  to be exposed and developed for removal, thus forming the orifice base plate  12 . The inclination on the sidewalls of the discharge port portion  26  to be formed for the orifice base plate  12  should desirably be formed as close as to 0° to the plane orthogonal to the main surface of the element base plate. However, if it is within a range of approximately 0 to 10°, there occurs no problem of any significance. 
     In the eighth step, as shown in FIG.  8 D and  FIG. 10C , chemical etching process and others are executed on the backside of the element base plate  11  to form the supply port  36  on the element base plate  11 . As the chemical etching process, the anisotropic etching that uses strongly basic alkali liquid (KOH, NaOH, TMAH), is applicable, for example. 
     In the ninth step, as shown in FIG.  8 E and  FIG. 10D , the DUV light having wavelength of 330 nm or less is irradiated from the main surface side of the element base plate  11  and transmitted through the covering resin layer  43  so as to dissolve the upper and lower resin layers  41  and  42 , which are the nozzle molding material positioned between the element base plate  11  and the orifice base plate  12 , through the supply port  36 , respectively. 
     In this way, it becomes possible to obtain the chip, which is provided with the discharge port  26   a , the supply port  36 , and the nozzle  27  having the extrusion  33  that serves as the control portion is formed with a difference in level for the supply path  32  communicated with those ports. Then, the liquid discharge head is obtained by electrically connecting this chip with a wired base plate (not shown) and others for driving the heater  20 . 
     Here, in accordance with the method for manufacturing the liquid discharge head  1 , if the upper resin layer  41  and the lower resin layer  42 , which are made dissoluble by destroying the bridge binding in the molecules by the irradiation of the DUV light, are hierarchically structured in the thickness direction of the element base plate  11 , it becomes possible to provide the control portion to be formed with three or more differences in level in the nozzle  27 . For example, the resin material, which is sensitive to the light the wavelength of which is 400 nm or more, is used further for the upper layer side of the upper resin layer. Then, the multiply stepped nozzle structure can be formed. 
     Fundamentally, it is preferable for the method for manufacturing the liquid discharge head  1  of the present embodiment to follow the method for manufacturing a liquid discharge head adopting, as means for discharging ink, the ink jet recording method disclosed in the specifications of Japanese Patent Application Laid-Open No. 04-10940 and Japanese Patent Application Laid-Open No. 04-10941. The method disclosed in the aforesaid specifications of the patent application is the one in which ink droplets are discharged using the structure that enables the bubble generated by the heater to be communicated with the air outside. For example, then, a liquid discharge head, which is capable of discharging ink droplet in an extremely small amount of 50 pl or less, is provided. 
     For the liquid discharge head  1 , bubble is communicated with the air outside. Therefore, the volume of ink droplet discharged from the discharge port  26  depends largely on the volume of ink positioned between the heater  20  and the discharge port  26 , that is, the volume of ink filled in the bubbling chamber  31 . In other words, the volume of ink droplet to be discharged is almost determined by the structure of the bubbling chamber  31  portion of the nozzle  27  of the liquid discharge head  1 . 
     Consequently, the liquid discharge head  1  is made capable of outputting images in high quality without unevenness of ink. As the structure arranged for the liquid discharge head of the present invention, bubble is communicated with the air outside. Therefore, when applied to a liquid discharge head, the shortest distance between the heater and discharge port of which is 30 μm or less, it demonstrates the best effect. However, it can act effectively on any one of the liquid discharge heads if only the head should be arranged to enable ink droplet to fly in the direction orthogonal to the main surface of the element base plate where the heater is provided. 
     As described above, the liquid discharge head  1  is provided with the second bubbling chamber  31   b , which is configured to be truncated cone. With this arrangement the volume of ink is gradually reduced and the flow of ink is made straight in the direction from the element base plate  11  toward the discharge port  26   a , and in the vicinity of the discharge port  26   a , the flying liquid droplet flies vertically with respect to the element base plate  11  when the liquid droplet flies. Also, with the provision of the extrusion  33  that controls the flow of ink in the bubbling chamber  31 , it is attempted to stabilize the volume of ink droplet to be discharged, thus enhancing the discharge efficiency of ink droplets. 
     (Second Embodiment) 
     In accordance with the first embodiment, the second bubbling chamber  31   b , which is configured to be in the form of truncated cone, is formed on the first bubbling chamber  31   a , and the sidewalls of the second bubbling chamber  31   b  are inclined to the plane orthogonal to the main surface of the element base plate  11 , and contracted in the direction toward the discharge port portion  26  at an inclination of 10 to 45°, and then, the structure is arranged so that on the circumferential portion of the upper face of the first bubbling chamber  31   a  in parallel with the main surface of the element base plate  11 , which is in contact with the opening communicated with the second bubbling chamber  31   b , the extrusion  33  that surrounds the opening and directed toward the main surface of the element base plate  11  is formed continuously. Here, for the liquid discharge head  2  in accordance with a second embodiment, the description will be made of the structure in which ink filled in the bubbling chamber is easier to flow to the discharge port. In this respect, for the liquid discharge head  2 , the same reference marks are provided for the same members of the liquid discharge head  1  described above. The descriptions thereof will be omitted. 
     As in the first embodiment, the bubbling chamber  56  of the liquid discharge head  2  of the second embodiment is provided with the first bubbling chamber  56   a  in which bubble is generated by the heater  20 , and the second bubbling chamber  56   b  arranged on the midway from the first bubbling chamber  56   a  to the discharge port portion  53 . The structure is arranged so that the sidewalls of the second bubbling chamber  56   b  are inclined to the plane orthogonal to the main surface of the element base plate  11 , and contracted in the direction toward the discharge port portion  26  at an inclination of 10 to 45°. Further, in the first bubbling chamber  56   a , the wall faces, which are provided for partitioning individually each of the bubbling chambers  56   a  arranged in the plural number, are contracted at an inclination of 0 to 10° to the plane orthogonal to the main surface of the element base plate  11 , and in the discharge port portion  53 , these are contracted in the direction toward the discharge port  53   a  at an inclination of 0 to 5° to the plane orthogonal to the main surface of the element base plate  11 . 
     As shown in FIG.  13  and  FIG. 14 , the orifice base plate  52  provided with the liquid discharge head  2  is formed by resin material in a thickness of approximately 30 μm. As described earlier in conjunction with  FIG. 1 , the orifice base plate  52  is provided with plural discharge ports  53   a  for discharging ink droplets; plural nozzles  54  in which ink flows; and the supply chamber  55  for supplying ink to each of the nozzles  54 . 
     The discharge port  53   a  is formed in a position facing the heater  20  on the element base plate  11 , which is a circular hole having the diameter of approximately 15 μm. In this respect, the discharge port  53  may be configured almost in the form of a star having spokes as required in terms of the discharge characteristics. 
     The nozzle  54  is provided with the discharge port portion  53  having the discharge port  53   a  for discharging liquid droplet; the bubbling chamber  56 , in which bubble is generated in the liquid therein by the heater  20  serving as the discharge energy generating element; and the supply path  57  for supplying liquid to the bubbling chamber  56 . 
     The bubbling chamber  56  is provided with the first bubbling chamber  56   a  communicated with the supply path  57  as the bottom face of the main surface of the element base plate  11  for generating bubble in liquid therein by use of the heater  20 , and a second bubbling chamber  56   b  communicated with the opening on the upper face of the first bubbling chamber  56   a  in parallel with the main surface of the element base plate  11 , in which the bubble generated in the first bubbling chamber  56   a  is developed. Then, for the circumferential portion on the upper face of the first bubbling chamber  56   a , which is in parallel to the main surface of the element base plate  11  and in contact with the opening communicated with the second bubbling chamber  56   b , an extrusion  33  is formed continuously to surround the opening in the direction toward the main surface of the element base plate  11 . 
     The discharge port portion  53  is arranged to be communicated with the opening on the upper face of the second bubbling chamber  56   b , and a difference in level is provided between the sidewall face of the discharge port portion  53  and the sidewall face of the second bubbling chamber  56   b.    
     The bottom end of the first bubbling chamber  56   a , which faces the discharge port  53   a , is formed to be almost rectangular. Also, the first bubbling chamber  56   a  is formed so that the shortest distance OH between the heater  20  in parallel to the main surface of the element base plate  11 , and the discharge port  53   a  becomes 30 μm or less. As described earlier in conjunction with  FIG. 1 , the heater  20  is arranged in the plural number on the element base plate  11 , and when the arrangement density is 600 dpi, the pitch between each of the heaters is approximately 42.5 μm. Then, if the width of the first bubbling chamber  56   a  in the arrangement direction of heater is formed to be 35 μm, the width of nozzle wall that shields between each of the heaters is approximately 7.5 μm. The height of the first bubbling chamber  56   a  from the surface of the element base plate  11  is 10 μm. The height of the second bubbling chamber  56   b  formed on the first bubbling chamber  56   a  is 15 μm. The height of the discharge port portion  53  formed for the orifice base plate  52  is 5 μm. The discharge port  53   a  is configured to be circular, the diameter of which is 15 μm. The second bubbling chamber  56   b  is configured to be truncated cone, and if the diameter of the bottom, which is in contact with the first bubbling chamber  56   a  is 30 μm, the diameter of the upper face on the discharge port portion  53  side is 19 μm, provided that the sidewall of the second bubbling chamber is formed at an inclination of 20°. Then, there is a difference in level of approximately 2 μm, and connection is made with the discharge port portion  53  having the diameter of 15 μm. 
     The height of the extrusion  33 , which is formed on the circumferential portion of the upper face of the first bubbling chamber  56   a  in parallel with the main surface of the element base plate  11 , and in contact with the opening communicated with the second bubbling chamber  56   b , surrounding the opening in the direction toward the main surface of the element base plate  11 , is 3 μm. 
     The bubble, which is generated in the first bubbling chamber  56   a  is developed toward the second bubbling chamber  56   b  and the supply path  57 , and the flow of ink filled in the nozzle  54  is straightened at the discharge port portion  53 . Thus, ink flies from the discharge port  53   a  arranged for the orifice base plate. 
     The supply path  57  is formed so as to enable one end thereof to be communicated with the bubbling chamber  56 , and the end to be communicated with the supply chamber  55 . 
     Here, for the sidewall of the second bubbling chamber  56   b , a larger inclination is provided, and also, an inclination is provided for the first bubbling chamber  56   a . With this arrangement, then, the ink, which is filled in the nozzle, is allowed to move more efficiently to the discharge port portion  53  by bubble generated in the first bubbling chamber  56   a . However, although the first bubbling chamber  56   a , the second bubbling chamber  56   b , and the discharge port portion  53  are all formed in good precision by means of photolithographic process, these are not necessarily formed exactly without any deviation. There are errors of sub-micron order in the alignments thereof. Therefore, in order to enable ink to fly straightly in the direction orthogonal to the main surface of the element base plate  11 , it is necessary for the discharge port portion  53  to straighten the flow of ink for the exact flying direction. For that matter, the inclination of sidewalls of the discharge port portion  53  should be in parallel with the direction orthogonal to the main surface of the element base plate as much as possible. In other words, it is desirable to make the inclination at a value as close as to 0°. 
     Here, however, in order to make the flying droplet as smaller as possible, it is necessary to make the area of the opening smaller still. As a result, if the height (length) of the discharge port portion  53  becomes larger than the opening, the viscosity resistance of ink increases extremely at such portion, which may lead to the deterioration of the discharge characteristics of flying ink. Therefore, for the liquid discharge head  2  of the second embodiment, it is arranged to enable the bubble generated in the first bubbling chamber to be developed more easily up to the second bubbling chamber, and also, to make the flowability of ink filled in the nozzle better in the second bubbling chamber. Further, the structure is arranged to execute the flow-straightening function for flying ink in the discharge direction. Here, although depending on the distance from the surface of the element base plate  11  to the discharge port  53   a , it is desirable to set the height of the second bubbling chamber to be approximately 3 to 25 μm, more desirably, approximately 5 to 15 μm, and also, it is desirable to set the length of the discharge port portion  53  to be approximately 1 to 10 μm, more desirably, approximately 1 to 3 μm. 
     Also, as shown in  FIG. 13 , the nozzle  54  is configured to be almost in the straight form, in which while it is orthogonal to the ink flow path, the width of the flow path in parallel with the main surface of the element base plate  11  is almost equal across the supply chamber  55  to the bubbling chamber  56 . Also, each of the inner wall faces of the nozzle  54  facing the main surface of the element base plate  11  is formed to be in parallel with the main surface of the element base plate  11  across the supply chamber  55  to the bubbling chamber  56 , respectively. Now, the description will be made of the operation of discharging ink droplets from the discharge port  53   a  of the liquid discharge head  2  structured as described above. 
     At first, for the liquid discharge head  2 , the ink, which is supplied from the supply port  36  into the supply chamber  55 , is supplied into each nozzle  54  of the first and second nozzle arrays, respectively. The ink, which is supplied to each nozzle  54 , flows along the supply path  57  to be filled in the bubbling chamber  56 . The ink, which is filled in the bubbling chamber  56 , is given film boiling by the heater  20 , and flies in the direction almost orthogonal to the main surface of the element base plate  11  by means of the developing pressure of bubble thus generated. Thus, it is discharged as ink droplet from the discharge port  53   a.    
     When the ink, which is filled in the bubbling chamber  56 , is discharged, part of ink in the bubbling chamber  56  is caused to flow to the supply path  57  side by the pressure of bubble generated in the bubbling chamber  56 . In the liquid discharge head  2 , the pressure of bubble generated in the first bubbling chamber  56   a  is propagated instantaneously to the second bubbling chamber  56   b , and ink filled in the first and second bubbling chambers  56   a  and  56   b  moves in the second bubbling chamber  56   b . At this juncture, since the inner walls are inclined, the bubble, which is being developed in the first and second bubbling chambers  56   a  and  56   b , abuts against the inner walls. Therefore, the pressure loss is small, and the bubble is developed toward the discharge port  53   a  in good condition. Then, the ink, the flow of which is straightened in the discharge port portion  53 , is allowed to fly from the discharge port  53   a  arranged for the orifice base plate  52  in the direction orthogonal to the main surface of the element base plate  11 . Also, the discharge volume of ink droplet is secured in good condition. As a result, the liquid discharge head  2  is made capable of making the discharge speed higher for the ink droplets to be discharged from the discharge port  53   a . Therefore, as compared with the conventional liquid discharge head, it is possible for the liquid discharge head  2  to enhance the kinetic energy of ink droplet, which is worked out from the discharge speed and the volume of discharge. Hence, wile the discharge efficiency is improved, the characteristics of discharge frequency is made higher as in the case of the liquid discharge head  1  described earlier. 
     Now, the brief description will be made of the method for manufacturing the liquid discharge head  2  structured as described above. The method of manufacture for the liquid discharge head  2  is almost the same as the method of manufacture for the liquid discharge head  1  described earlier. Therefore, while the same reference marks are applied to the same members, the description of the same steps of manufacture will be omitted. 
     The method of manufacture for the liquid discharge head  2  follows the method of manufacture for the liquid discharge head  1  described earlier. As shown in FIG.  8 A and  FIG. 9A , the first step is the formation process of the base plate to form the element base plate  11  by providing plural heaters  20  and the predetermined wiring for applying voltage to those heaters  20  on the Si chip, for example, by means of patterning process and the like. 
     As shown in  FIG. 8B ,  FIG. 9B , and  FIG. 9C , the second step is the coating process in which the DUV light, which is the ultraviolet rays having the wavelength of 330 nm or less, is irradiated onto the element base plate  11  so as to enable the dissolvable lower resin layer  42  and upper resin layer  41  to be continued when bindings in the molecules are destroyed, and then, each of them is coated by means of spin-coating method. In this coating step, the film thickness of the lower resin layer  42  is 10 μm, and the upper resin layer  41  is 15 μm. 
     As shown in FIG.  8 B and  FIG. 9D , the third step is the pattern formation process in which a filter is installed, as means for selecting wavelength, on the exposing device that irradiates DUV light, and cuts off the DUV light having the wavelength of less than 260 nm, and only the one having those of 260 nm or more is transmitted so as to enable the NUV light having the wavelength of around 260 to 330 nm to be irradiated onto the upper resin layer  41  to be exposed and developed for the formation of desired nozzle pattern on the upper bubbling layer  41 . In this step, when development is performed, a step of forming a recessed portion  33 ′, which becomes the continuous extrusion  33  later, is executed together for the lower resin layer  42  on the circumference of the organic resin pattern that forms the second bubbling chamber  56   b  at that time. 
     In the fourth step, as shown in FIG.  8 B and  FIG. 9D , the upper resin layer  41  is heated at a temperature of 140° C. for 10 minutes after the pattern formation, thus forming an inclination of 20° on the side face of the upper resin layer  41 . 
     As shown in FIG.  8 B and  FIG. 9E , the fifth step is the pattern formation process in which the DUV light of wavelength 210 to 330 nm is irradiated using the aforesaid exposing device so as to enable the lower resin layer  42  to be exposed and developed for the formation of desired nozzle pattern on the lower resin layer  42 . 
     The sixth step is the coating process in which as shown in  FIG. 10A , a transparent covering resin layer  43 , which becomes the orifice base plate  12 , is coated on the upper resin layer  41  and the lower resin layer  42  made dissolvable by the destruction of bridge binding in the molecules by the irradiation of DUV light. The film thickness of the covering resin layer  43  is 30 μm. 
     In the seventh step, as shown in FIG.  8 C and  FIG. 10B , the UV light is irradiated onto the covering resin layer  43  using the exposing device to enable the portion corresponding to the discharge port portion  53  to be exposed and developed for removal, thus forming the orifice base plate  52 . The length of the discharge port portion  53  is 5 μm. 
     In the eighth step, as shown in FIG.  8 D and  FIG. 10C , chemical etching process and others are executed on the backside of the element base plate  11  to form the supply port  36  on the element base plate  11 . As the chemical etching process, the anisotropic etching that uses strongly basic alkali solution (KOH, NaOH, TMAH), is applicable, for example. 
     In the ninth step, as shown in FIG.  8 E and  FIG. 10D , the DUV light having wavelength of 330 nm or less is irradiated from the main surface side of the element base plate  11  and transmitted through the covering resin layer  43  so as to dissolve the upper and lower resin layers  41  and  42 , which are the nozzle molding material positioned between the element base plate  11  and the orifice base plate  52 , respectively. 
     In this way, it becomes possible to obtain the chip, which is provided with the discharge port  53   a , the supply port  36 , and the nozzle  54  having the control portion  58  formed with a difference in level for the supply path  57  communicated with them. Then, the liquid discharge head  2  is obtained by electrically connecting this chip with a wired base plate (not shown) and others for driving the heater  20 . 
     As described above, the liquid discharge head  2  is provided with the second bubbling chamber  56   b  configured to be truncated cone, and then, the wall face of the first bubbling chamber  56   a  is inclined so as to straighten the flow of ink with the gradual reduction of the volume thereof in the direction from the element base plate  11  toward the discharge port  53   a . In the vicinity of the discharge port  53   a , the flying liquid droplet flies vertically to the element base plate  11  when the liquid droplet flies. Also, with the provision of the extrusion  58  for controlling the flow of ink in the bubbling chamber  56 , it becomes possible to stabilize the volume of ink droplet to be discharged, thus enhancing the discharge efficiency of ink droplets. 
     (Third Embodiment) 
     With reference to the accompanying drawings, the brief description will be made of the liquid discharge head  3  in accordance with a third embodiment. Here, the height of the first bubbling chamber of the liquid discharge head  2  described above is made smaller still, and the height of the second bubbling chamber thereof is made larger. In this respect, for the liquid discharge head  3 , the same reference marks are applied to the same members of the liquid discharge heads  1  and  2  described earlier, and the description thereof will be omitted. As in the first embodiment, the bubbling chamber  66  of the liquid discharge head  3  of the third embodiment is provided with the first bubbling chamber  66   a  in which bubble is generated by the heater  20 , and the second bubbling chamber  66   b  arranged on the midway from the first bubbling chamber  66   a  to the discharge port portion  63 . The structure is arranged so that the sidewalls of the second bubbling chamber  66   b  are inclined to the plane orthogonal to the main surface of the element base plate  11 , and contracted in the direction toward the discharge port portion  63  at an inclination of 10 to 45°. Further, in the first bubbling chamber  66   a , the wall faces, which are provided for partitioning individually each of the bubbling chambers  66   a  arranged in the plural number, are contracted at an inclination of 0 to 10° to the plane orthogonal to the main surface of the element base plate  11 , and in the discharge port portion  63 , these are contracted in the direction toward the discharge port  63   a  at an inclination of 0 to 5° to the plane orthogonal to the main surface of the element base plate  11 . 
     On the circumferential portion on the upper face of the first bubbling chamber  66   a  in parallel with the main surface of the element base plate  11 , which is communicated with the second bubbling chamber  66   b , the extrusion  33  is formed continuously to surround the opening thereof in the direction toward the main surface of the element base plate  11 . 
     As shown in FIG.  15  and  FIG. 16 , the orifice base plate  62  provided with the liquid discharge head  3  is formed by resin material in a thickness of approximately 30 μm. As described earlier in conjunction with  FIG. 1 , the orifice base plate  62  is provided with plural discharge ports  63  for discharging ink droplets; plural nozzles  64  in which ink flows; and the supply chamber  65  for supplying ink to each of the nozzles  64 . 
     The discharge port  63   a  is formed in a position facing the heater  20  on the element base plate  11 , which is a circular hole having the diameter of approximately 15 μm. In this respect, the discharge port  63   a  may be configured almost in the form of a star having spokes as required in terms of the discharge characteristics. 
     The bottom end of the first bubbling chamber  66   a , which faces the discharge port  63   a , is configured to be almost rectangular. Also, the first bubbling chamber  66   a  is formed so as to make the shortest distance OH between the discharge port  63   a , and the main surface of the heater  20  in parallel with the mine surface of the element base plate  11  to be 30 μm or less. The height from the surface of the element base plate  11  on the upper face of the first bubbling chamber  66   a  is formed to be 8 μm, for example, and the height of the second bubbling chamber  66   b , which is provided on the first bubbling chamber  66   a , is formed to be 18 μm. The second bubbling chamber  66   b  is configured to be square-truncated cone, and the length of one side of the first bubbling chamber  66   a  side is 28 μm. For the corners, an R of 2 μm is formed, respectively. Then, the sidewalls of the second bubbling chamber  66   b  are inclined at an angle of 15° to the plane orthogonal to the main surface of the element base plate  11  so as to be contracted in the direction toward the discharge port portion  63  side. Then, the upper face of the second bubbling chamber  66   b , and the discharge port portion  63  the diameter of which is 15 μm are communicated with a difference in level of approximately 1.7 μm at the minimum. 
     The height of the discharge portion  63  where the orifice base plate  62  is formed is 4 μm. The discharge port  63   a  is circular having the diameter of 15 μm. 
     The height of extrusion  33  is 2 μm. The extrusion is formed in the direction toward the main surface of the element base plate  11  on the circumferential portion on the upper face of the first bubbling chamber  66   a , which is in parallel with the main surface of the element base plate  11 , and the extrusion is in contact with, and surrounds the opening communicated with the second bubbling chamber  66   b.    
     The bubble, which is generated in the first bubbling chamber  66   a , is developed toward the second bubbling chamber  66   b  and the supply path  67 . Then, the flow of the ink, which is filled in the nozzle  64 , is straightened in the discharge port portion  63 , and flies from the discharge port  63   a  arranged for the orifice base plate  62 . 
     The supply path  67  is formed so as to enable one end thereof to be communicated with the bubbling chamber  66 , and the other end to be communicated with the supply chamber  65 . 
     The upper face of the surface bubbling chamber  66   a  in parallel with the main surface, and the upper face of the supply path  67  adjacent to the bubbling chamber  66  in parallel with the main surface are made continuous on one and the same plane, and connected with the upper face of the supply path  67  on the supply chamber  65  side, which is higher than that, and in parallel with the main surface of the element base plate  11 , by means of a difference in level  69  formed by inclination toward the main surface. Then, on the lower end of the portion having a difference in level, the extrusion is arranged. The region between the difference in level  69  and the extrusion  68  to be in contact with the first bubbling chamber  66   a  also constitutes a control portion, which controls, in cooperation with the extrusion  68 , the ink that flows in the bubbling chamber  66  by bubble. Here, as in the cases of the first and second embodiments, it may be possible to continue the upper face from the bubbling chamber  66  to the supply chamber  65 , which is in parallel with the main surface, by one and the same plane without providing any difference in level. 
     The first bubbling chamber  66   a  is formed on the element base plate. With the height thereof being made smaller, it becomes possible to make the sectional area smaller for the ink flow path across the one end portion of the supply path  67  adjacent to the first bubbling chamber  66   a  and the first bubbling chamber  66   a . As a result, this sectional area is made smaller still than that of the nozzle  54  of the liquid discharge head  2  of the second embodiment. 
     On the other hand, with the height of the second bubbling chamber  66   b  being made larger, it becomes easier for the pressure of bubble generated in the first bubbling chamber  66   a  to be propagated to the second bubbling chamber  66   b . Then, the propagation thereof to the supply path  67 , which is communicated with the one end of the first bubbling chamber  66   a , is made difficult. As a result, the movement of ink to the discharge port  63  is made faster and more efficiently. 
     Also, the nozzle  64  is configured to be in a straight form, and the width of flow path thereof, which is in parallel with the main surface of the element base plate  11 , while being orthogonal to the ink flow direction, is made substantially equal across the supply chamber  65  and the bubbling chamber  66 . Also, each of the inner wall faces of the nozzle  64 , which faces the main surface of the element base plate  11 , is formed in parallel with the main surface of the element base plate  11 , respectively, across the supply chamber  65  and the bubbling chamber  66 . 
     Now, the description will be made of the ink discharge operation from the discharge port  63  of the liquid discharge head  3  structured as described above. At first, for the liquid discharge head  3 , the ink, which is supplied from the supply port  36  into the supply chamber  65 , is supplied into each nozzle  64  of the first and second nozzle arrays, respectively. The ink, which is supplied to each nozzle  64 , flows along the supply path  67  to be filled in the bubbling chamber  66 . The ink, which is filled in the bubbling chamber  66 , is given film boiling by the heater  20 , and flies in the direction almost orthogonal to the main surface of the element base plate  11  by means of the developing pressure of bubble thus generated. Thus, it is discharged as ink droplet from the discharge port  63 . 
     When the ink, which is filled in the bubbling chamber  66 , is discharged, part of ink in the bubbling chamber  66  is caused to flow to the supply path  67  side due to the pressure of bubble generated in the first bubbling chamber  66   a . The height of the first bubbling chamber  66   a  of the liquid discharge head  3  is made smaller, the ink flow path of the supply path  67  is made narrower still. Therefore, when part of ink in the first bubbling chamber  66   a  is caused to flow to the supply path  67  side, the fluid resistance of the flow path of supply path  67  is increased against the ink that flows toward the supply chamber  65  side from the first bubbling chamber  66   a  side through the supply path  67 . As a result, it is made possible for the liquid discharge head  3  to suppress more the flow of the ink, which is filled in the bubbling chamber  66 , to the supply path  67  side. Thus, the development of bubble from the first bubbling chamber  66   a  to the second bubbling chamber  66   b  is further promoted to make the flowability of ink easier to be transferred to the discharge port side. In this manner, the volume of ink discharge is secured more reliably. 
     Also, for the liquid discharge head  3 , the pressure of bubble propagated from the first bubbling chamber  66   a  to the second bubbling chamber  66   b  becomes more efficient, and with the inclinations of the wall faces of the first bubbling chamber  66   a  and second bubbling chamber  66   b , it is made possible to suppress the pressure loss of the bubble developed in the first bubbling chamber  66   a  and second bubbling chamber  66   b , which may be incurred when the developing bubble abuts against the inner walls of the bubbling chamber  66 . As a result, bubble is developed in good condition. Thus, for the liquid discharge head  3 , the discharge speed of ink from the discharge port  63  is enhanced. 
     In accordance with the liquid discharge head  3  described above, the movement of ink in the first bubbling chamber  66   a  and second bubbling chamber  66   b  is made faster, and resistance thereto is more reduced. Also, with the length of the discharge port portion being made smaller, the straightening action of ink flow is made more promptly than the liquid discharge heads  1  and  2 , and the discharge efficiency of ink droplets is further enhanced accordingly. 
     (Fourth Embodiment) 
     Lastly, with reference to the accompanying drawings, the description will be made of the liquid discharge head  4  in accordance with a fourth embodiment. In this respect, whereas each nozzle of the first nozzle array  16  and second nozzle array  17  of the aforesaid liquid discharge heads  1  to  3  is formed equally, the shapes and heater areas of the first nozzle array and second nozzle array are different from each other. 
     As shown in  FIGS. 17A and 17B , the element base plate  96  of the liquid discharge head  4  is provided with the first and second heaters  98  and  99  having the areas in parallel with the main surface of the element base plate but different from each other, respectively. 
     Also, for the orifice base plate  97  of the liquid discharge head  4 , the first and second nozzle arrays  101  and  102  are provided, but the opening area and nozzle shape of each of the discharge ports  106  and  107  are formed to be different from each other. Each of the discharge ports  106  of the first nozzle array  101  is formed to be in the circular hole. Each nozzle of the first nozzle array  101  has the same structure as that of the liquid discharge head  2  described above. Therefore, the description thereof will be omitted. However, in order to make the flow of ink in the bubbling chamber better, the second bubbling chamber  109  is formed on the first bubbling chamber. Also, each discharge port  107  of the second nozzle array  102  is configured radially almost in the form of a star. Each nozzle of the second nozzle array  102 , too, is configured to be in the straight form without changing the sectional area of ink flow path across the bubbling chamber and the discharge port. 
     Also, for the element base plate  96 , the supply port  104  is formed to supply ink to the first and second nozzle arrays  101  and  102 . 
     Now, the volume Vd of ink droplet that flies from the discharge port generates the flow of ink in the nozzle. Then, the returning action of meniscus subsequent to the flight of ink droplet is performed by the capillary force generated corresponding to the area of opening of the discharge port. Here, given the opening area of the discharge port as S 0 ; the outer circumference of the opening edge as L 1 ; the surface tension of ink as γ; and the contact angle of ink with the inner wall as θ, the capillary force p is expressed as follows:
 
 p =γ cos θ× L   1   /S   0 .
 
Also, on the assumption that only the volume Vd of ink droplet that has flown generates the meniscus, and it returns after the time t of discharge frequency (refilling time t), the following relations are established:
 
 p=B ×( Vd/t )
 
     In accordance with the liquid discharge head  4 , the ink droplets having different discharge volumes are enabled to fly from a single liquid discharge head  4 , because the first and second nozzle arrays  101  and  102 , the areas of the first and second heaters  98  and  99 , and the opening areas of the discharge ports  106  and  107  are made different from each other. 
     Also, for the liquid discharge head  4 , the material value of ink discharged from the first and second nozzle arrays  101  and  102 , such as the surface tension, viscosity, and pH, is the same, and it becomes possible to make the discharge frequency response capabilities of the first and second nozzle arrays  101  and  102  substantially identical by setting the physical quantity, such as the inertance A and the viscosity resistance B, corresponding to the discharge volume of ink droplet discharged from each of the discharge ports  106  and  107 . 
     In other words, in a case where the discharge volume of each ink droplet to be discharged is defined as 4.0 (pl) and 1.0 (pl), respectively, for the first and second nozzle arrays  101  and  102 , if the refilling time t is made almost the same for each nozzle arrays  101  and  102  of the liquid discharge head  4 , it means that the viscosity resistance B, and the L 1 /S 0 , that is, the ratio between each outer circumferences L 1  of the discharge ports  106  and  107 , and each opening areas S 0  of the discharge ports  106  and  107 , are made almost the same. 
     Now with reference to the accompanying drawings, the description will be made of the method for manufacturing the liquid discharge head  4  structured as described above. 
     The method for manufacturing the liquid discharge head  4  follows the aforesaid methods for manufacturing the liquid discharge heads  1  and  2 , and with the exception of each step of forming nozzle patterns on the upper and lower resin layers  41  and  42  of the element base plate  96 , all other steps are the same. As shown in  FIG. 18A ,  FIG. 18B , and  FIG. 18C , the upper and lower resin layers  41  and  42  are formed, respectively, in the pattern formation steps for the liquid discharge head  4  in the method of manufacture therefor, and then, as shown in FIG.  18 D and  FIG. 18E , each of the desired nozzle patterns are formed per the first and second nozzle arrays  101  and  102 , respectively, that is, each of the nozzle patterns for the first and second nozzle arrays  101  and  102  are formed to be asymmetrical with respect to the supply port  104 , respectively. In other words, with the method for manufacturing the liquid discharge head  4 , it is easy to form the liquid discharge head  4  by changing locally the shapes of nozzle patterns for the upper and lower resin layers  41  and  42 . The steps after this formation process are the same as those described for the first embodiment in conjunction with  FIGS. 19A  to  19 D. Therefore, the description thereof will be omitted. 
     In accordance with the liquid discharge head  4  described above, the structure of each nozzle of the first and second nozzle arrays  101  and  102  is arranged to be different from each other to make it possible for each of the nozzle arrays  101  and  102  to discharge ink droplets each having different discharge volume, respectively. In this manner, ink droplets are enabled to fly stably with ease at the optimal discharge frequency for which the higher speed discharge has been attempted. 
     Also, in accordance with the liquid discharge head  4 , it is made possible to suck ink evenly and rapidly when the recovery operation is executed by recovery mechanism with the adjustment to be made for balancing the fluid resistance by the capillary force, while making the formation of simpler structure of recovery mechanism possible. Thus, the reliability of discharge characteristics of the liquid discharge head  4  can be enhanced to provide a recording apparatus capable of performing recording operation more reliably. 
     In accordance with the liquid discharge head of the present invention as described above, the bubble, which is generated in the first bubbling chamber is developed into the second bubbling chamber, and the discharge volume of ink in the nozzle, which flies as ink droplet through the second bubbling chamber and the discharge port portion, is stabilized, hence making it possible to enhance the discharge efficiency. 
     Also, in accordance with the liquid discharge head of the present invention, the pressure loss that may be incurred when the bubble, which is generated in the first bubbling chamber, abuts against the inner walls of the second bubbling chamber, is suppressed to enable ink to flow rapidly and efficiently in the bubbling chamber, thus making it possible to enhance the discharge efficiency, as well as to attempt the higher refilling speed.