Abstract:
There is provided a printer head in an ink jet printer that includes: a quantification medium pressuring chamber where a quantification medium is introduced; a discharge medium pressuring chamber where a discharge medium is introduced; a quantification medium nozzle communicating with the quantification medium pressuring chamber; a discharge medium nozzle communicating with the discharge medium pressuring chamber, the discharge medium nozzle being disposed to adjoin the quantification medium nozzle; and a first pressure generating element pulling the quantification medium pushed out of the quantification medium nozzle into the discharge medium nozzle to form a mixed solution by contacting the quantification medium in the discharge medium nozzle through a surface where the quantification medium nozzle opens, wherein the first pressure generating element then generates a pressure for discharging the mixed solution from the discharge medium nozzle.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a printer head, an ink jet printer and a method for driving the printer head. 
     2. Description of the Related Art 
     It has recently become widespread to draw up documents on computers that are used as desktop publishers, especially in offices. And lately demands for outputting not only characters and graphics but also colored natural pictures like photographs together with them has become increased. Therefore, it has been required to print high quality natural pictures, and gradation expression with the expression of halftones has consequently becomes important. 
     Furthermore, the so-called on demand type printers have been coming into wide use in recent years because they are suitable for miniaturization and reduction in cost. The on demand type printers perform recording by discharging ink droplets from nozzles only when it is required to print according to control signals that are in compliance with recording signals to make the ink droplets adhere on a material to be recorded, such as a sheet of paper or a film. 
     As aforesaid, although various methods as a method for discharging ink droplets from nozzles have been proposed, a method using a piezoelectric element or a heating element is generally used. The former is a method for discharging ink by applying pressure to it by means of the deformation of the piezoelectric element. The latter is a method for discharging ink by the pressure of bubbles produced by vaporizing the ink in nozzles by the heat generated by the heating element. 
     In addition, various methods have been proposed as a method for mimetically realizing the aforementioned gradation expression with the expression of halftones on the aforementioned on demand type printer that discharges ink droplets. That is, as a first method, there is a method that expresses the halftone gradation by controlling the sizes of the ink droplets to be discharged by varying the voltage value or the pulse width of a pulse voltage to be supplied to the piezoelectric element or the heating element to make diameters of dots to be printed variable. 
     However, the above first method has a defect that expressible gradation steps are not many, in particular, the expression of low density is very difficult, because there is a limit to the minimum diameter of the droplets owing to the fact that, if the voltage or the pulse width supplied to the piezoelectric element or the heating element is decreased too much, the ink is not discharged. Consequently, the first method is not satisfactory for a printout of a natural picture. 
     Besides, as a second method, there is a method that realizes a gradation expression by constituting one pixel with a matrix composed of e.g. 4×4 dots without varying the diameters of the dots, and by performing the picture processing such as the so-called dither method or the error diffusion method of each matrix. 
     However, although seventeen gradation steps of the density can be expressed by the second method if one pixel is composed of the 4×4 matrix, the resolution of a printed picture deteriorates to one fourth if the picture is printed, for example, at the dot density same as that of the first method. Consequently, the printed picture becomes conspicuous in roughness, and thus the second method is also not satisfactory for a printout of a natural picture. 
     Accordingly, for principally resolving the problems of the conventional on demand type printers, the inventors of the present invention have proposed such a printer as was described in, for example, JP-A 201024/93 and JP-A 195682/95, which printer mixes ink and diluent, i.e. a transparent solvent, together at a predetermined mixing ratio just before discharging to be diluent ink, and immediately discharges the diluent ink from nozzles to make it adhere on a material to be recorded for recording. 
     Although, in the following description, the system in which ink is used as a quantification medium and diluent is used as a discharge medium, and in which the ink as the quantification medium is mixed with the diluent as the discharge medium to be the diluent ink, and further in which recording is done by discharging the discharge medium, is called as a carrier jet system among the aforementioned systems, there is no problem in a printer even if the diluent is used as the quantification medium and the ink is used as the discharge medium. 
     A printer in accordance with such a carrier jet system can control the density of the mixed solution to be discharged by varying the mixing ration of the ink and the diluent by varying the amount of the quantification medium that is either the ink or the diluent, and then the printer can separately vary the density of every dot to be printed. Consequently, the printer can print out a natural picture rich in the halftone gradation thereof without producing the deterioration of its resolution. 
     As a two liquids mixing type printer as stated above, there is the so-called external mixing type printer as will be shown in the following, for example. 
     The printer includes a quantification medium pressuring chamber where a quantification medium is introduced and a discharge medium pressuring chamber where a discharge medium is introduced. An opening of a quantification medium nozzle communicating with the quantification medium pressuring chamber and an opening of a discharge medium nozzle communicating with the discharge medium pressuring chamber adjoin to each other. The printer oozes the quantification medium from the quantification medium nozzle through the opening surface of the nozzle to the discharge medium nozzle, and makes the oozed quantification medium contact with the discharge medium plugged in the vicinity of the tip of the discharge medium nozzle to form the mixed solution. And then, the printer discharges the discharge medium from the discharge nozzle to discharge the quantification medium and the discharge medium as the mixed solution. 
     In such a structure, because the qualification nozzle and the discharge nozzle are separately formed, the quantification medium and the discharge medium do not diffuse while they are waiting for being discharged, and mutual affluxes at the time of mixing and discharging can be prevented. 
     When printing is done by the printer head shown in FIG. 21, it is done along the following description. The description is now done by making use of a timing chart for the imposition of driving voltages shown in FIG.  22 . The so-called laminated type piezoelectric elements are used as a first laminated type piezoelectric element  43  and a second laminated type piezoelectric element  44 . There are two types of laminated type piezoelectric elements, one of them utilizes the displacement thereof in the shrinking direction (the so-called d- 31  direction), and the other utilizes the displacement thereof in the elongating direction (the so-called d- 33  direction). The latter is used as both of the first laminated type piezoelectric element  43  and the second laminated type piezoelectric element  44 . 
     As shown in the timing chart of the imposition of the driving voltages of FIG. 22, at first, at a point of time indicated by reference character (a) in FIG. 22, positive voltages, 10 V for the first laminated type piezoelectric element  43  and 15 V for the second laminated type piezoelectric element  44 , are being imposed on them as driving voltages. The horizontal axis of FIG. 22 indicates time, and the vertical axis of FIG. 22 indicates driving voltages for the first laminated type piezoelectric element  43  and the second laminated type piezoelectric element  44 . At this time, a quantification medium  45  and a discharge medium  49  are in their waiting state shown in FIG.  23 (A). 
     Next, at a point of time indicated by reference character (b) in FIG. 22, the driving voltage for the first laminated type piezoelectric element  43  starts to be lowered until a point of time indicated by reference character (d) in FIG. 22 to be 0 V over a period of 50 μs. Then, the first laminated type piezoelectric element  43  is elongated to push the touching part of a diaphragm  42  out. As a result, the volume of a quantification medium pressuring chamber  56  decreases. Consequently, at a point of time indicated by reference character (c) in FIG. 22 that is within an intermediate period between the point of time indicated by reference character (b) in FIG.  22  and the point of time indicated by reference character (d) in FIG. 22, the quantification medium  45  is pushed out of a quantification medium nozzle  53  as mimetically shown in FIG.  23 (B). In the present case, because the quantification medium nozzle  53  is formed so as to gradually approaches to a discharge medium nozzle  54 , the quantification medium  45  is pushed out to the discharge medium nozzle  54 . 
     This state is kept for the period of 50 μs from the point of time indicated by reference character (d) in FIG. 22 to the point of time indicated by reference character (e) in FIG.  22 . As a result, at the point of time indicated by reference character (e) in FIG. 22, as shown in FIG.  23 (C), the quantification medium  45  becomes a state of being coupled to the discharge medium  49  after the quantification medium being contacted to the discharge medium  49 . 
     From the point of time indicated by reference character (e) in FIG. 22, the driving voltage of the first laminated type piezoelectric element  43  is gradually raised to the initial value. Then, since the first laminated type piezoelectric element again shrinks, the volume of the quantification medium pressuring chamber  56  increases so that the quantification medium  45  begins to be pulled into the quantification medium nozzle  53 . 
     As shown in FIG.  24 (A), the meniscus of the ink remaining on the discharge medium nozzle  54  in a state of being swollen thereon after being torn off, as shown in FIG.  24 (B), comes into a waiting state by the capillary attraction of a mixed solution  69  that is produced by the mixture of the meniscus and the diluent in the discharge medium nozzle  54 . 
     For a period from a point of time indicated by reference character (f) in FIG. 22, which point is later than the point of time indicated by reference character (e) in FIG. 22, to a point of time indicated by reference character (g) in FIG. 22, the driving voltage for the second laminated type piezoelectric element  44  is lowered from 15 V to 0 V over a period of 10 μs. Then, the second laminated type piezoelectric element  44  is elongated to push the touching part of the diaphragm  42  out. As a result, the volume of a discharge medium pressuring chamber  58  decreases. Consequently, at the point of time indicated by reference character (f) in FIG. 22, the mixed solution  69  begins to be pushed out of the discharge medium nozzle  54  as mimetically shown in FIG.  24 (C). 
     This state is kept for the period of 50 μs from the point of time indicated by reference character (g) in FIG. 22 to a point of time indicated by reference character (i) in FIG.  22 . As a result, at a point of time indicated by reference character (h) in FIG. 22 that is within an intermediate period between the point of time indicated by reference character (g) in FIG.  22  and the point of time indicated by reference character (i) in FIG. 22, as shown in FIG.  25 (A), the mixed solution  69  becomes a state of being further pushed out of the discharge medium nozzle  54 . 
     On the other hand, since the driving voltage of the first laminated type piezoelectric element  43  continues to rise, the quantification medium  45  is being pulled into the quantification medium nozzle  53  so that the part contacting with the discharge medium  49  is left. 
     The driving voltage of the second laminated type piezoelectric element  44  begins to rise gradually from the point of time indicated by reference character (i) in FIG.  22 . Then, the second laminated type piezoelectric element  44  again starts to shrink so that the volume of the discharge medium pressuring chamber  58  begins to increase. As a result, at a point of time indicated by reference character (j) in FIG. 22 that is a point of time a little later than the point of time indicated by reference character (i) in FIG. 22, as mimetically shown in FIG.  25 (B), a constriction begins to be produced between the mixed solution  69  and the discharge medium  49 . Incidentally, at the point of time, the driving voltage of the first laminated type piezoelectric element  43  returns to the initial value, 10 V, and then is kept in this state. 
     At a point of time indicated by reference character (k) in FIG. 22, which point is later than the point of time indicated by reference character (j) in FIG. 22, as mimetically shown in FIG.  25 (C), the mixed solution  69  is torn off from the discharge medium  49  to be discharged from the discharge medium nozzle  54 , and further the discharge medium  49  is pulled into the discharge medium nozzle  54 . 
     Furthermore, at a point of time indicated by reference character (l) in FIG. 22, which point is later than the point of time indicated by reference character (k) in FIG. 22, the driving voltage of the second laminated type piezoelectric element  44  returns to the initial value, 15 V. Incidentally, the period between the point of time indicated by reference character (i) in FIG.  22  and the point of time indicated by reference character (l) in FIG. 22 is 100 μs. At the point of time indicated by reference character (l) in FIG. 22, as mimetically shown in FIG.  26 (A), the mixed solution  69  in a sphere continues to fly to a not shown material to be recorded, and then the mixed solution  69  adheres on the material to be recorded for performing recording. 
     During the period between the point of time indicated by reference character (j) in FIG.  22  and the point of time indicated by reference character (l) in FIG. 22, the quantification medium  45  is gradually plugged in the quantification medium nozzle  53  by the capillary attraction, and then at the point of time indicated by reference character (l) in FIG. 22, as mimetically shown in FIG.  26 (A), the quantification medium  45  is plugged up to the tip of the quantification nozzle  53 . 
     Furthermore, at a point of time indicated by reference character (m) in FIG. 22 later than the point of time indicated by reference character (l) in FIG. 22, as mimetically shown in FIG.  26 (B), the discharge medium  49  is plugged in the discharge medium nozzle  54  by the capillary attraction similarly to the quantification medium  45 , and at a later point of time indicated by reference character (n) in FIG. 22, as mimetically shown in FIG.  26 (C), the discharge medium  49  returns to the waiting state thereof. 
     It is known that the amount of the projection of the first laminated type piezoelectric element  43  varies linearly to the driving voltage thereof. Besides, since the mixing ratio of the mixed solution is determined in accordance with the amount of the pushed out quantification medium, the reflection density of a dot is also determined under a one-to-one correspondence to the driving voltage. That is, the driving voltage is determined under the one-to-one correspondence to a desired gradation value. We here suppose that the gradation value when the quantification is done under the driving voltage of 10 V is the maximum gradation value to be 255/255, as shown in FIG.  22 . Then, as the gradation value at the time of the quantification for a period of points of time indicated by reference characters (n)-(o)-(p)-(q) in FIG. 22 when the driving voltage takes a waveform of 4 V, which period follows to the period when the driving voltage takes a waveform of 10 V as shown in FIG. 22, one value of x that becomes x/255 is determined. 
     The characteristic of the driving system described above that the mixed solution is discharged after waiting for the quantification medium ink, which has been pushed out on the discharge medium nozzle to be quantified, to be naturally settled in the discharge medium nozzle. 
     That is, the driving system should perform two operations in a period, one of which is the operation of “the quantification of the quantification medium” and the other of which is the operation of “the quantification medium is settled in the discharge medium nozzle while the quantification medium is mixed with the discharge medium”. In particular, in the case where a large quantity of the quantification medium is quantified at the maximum density, it is difficult to increase the driving frequency because it took a long time to settle the quantification medium in the discharge nozzle while the quantification medium is mixed with the discharge medium. 
     Furthermore, if the amount of ink to be quantified is increased more than a predetermined amount, the quantification medium ink overflows the discharge medium nozzle before the quantification medium ink is pulled into the discharge medium nozzle by the capillary attraction. Such overflow may bring about the change of the discharging direction by the fact that the mixed solution to be discharged is drawn by the overflowed ink, and further may result in no discharge at the worst. 
     For example, although the present system pushes out the quantification medium from the waiting state under 10 V driving voltage, if the driving voltage of the waiting state is tried to be increased, the quantification medium and the discharge medium are not mixed more than a predetermined mixing ratio as shown in FIG.  27 . FIG. 27 shows the results of an experiment using the printer head shown in FIG.  21  and the driving voltages of the waveforms shown in FIG.  22 . When the amount of the quantification of the quantification medium is increased in the case where the total consumption amount of the mixed solution is 60 pl per one drop, the operation of the head becomes unstable if the amount exceeds the boundary line shown in FIG.  27 . 
     FIGS.  28 (A)- 28 (C) are drawings mimetically illustrating observations of the states of the quantification medium  45  in the vicinity of the quantification medium nozzle  53  and the discharge medium nozzle  54  by means of a microscope using a stroboscope. 
     FIG.  28 (A) shows a halfway state of the quantification of the quantification medium  45  in the vicinity of the nozzles  53  and  54  in the unstable area. The quantification medium  45  that has already quantified exists on the discharge medium nozzle  54  as if it goes to overflow, as shown in FIG.  28 (A). In the unstable area in FIG. 27, the quantification medium  45  continues to be pushed out for being quantified furthermore. 
     As shown in FIG.  28 (B), the quantification medium  45 , which could not exist on the discharge medium nozzle  54  after being further pushed out, overflows around both the nozzles  53  and  54 . 
     As shown in FIG.  28 (C), the remaining quantification medium  45  shown in FIG.  28 (B) pulls the mixed solution  69  to be discharged to a direction being off from the direction normal to a nozzle plate, resulting in the disturbance of the direction of discharging the mixed solution  69 , not discharging and the like. 
     That is, the maximum quantification amount of the quantification medium  45  is the amount of the quantification medium  45  that can exist on the discharge medium nozzle  54  without overflowing in this driving system. If quantification more than the maximum quantification amount is tried, the results shown in FIGS.  28 (A)- 28 (C) may bring about such results as are shown in FIGS.  28 (A)- 28 (C). 
     Furthermore, such an operation as “accumulating the quantification medium  45  on the discharge medium nozzle  54 ” is strongly influenced by the treatment of the surface of the discharge medium nozzle  54  such as a water repellent treatment. If the effect of the water repellent treatment is strong, the amount of the quantification medium  45  capable of being accumulated or being quantified becomes great in quantity. If the water repellent treatment is not done, the quantification medium  45  becomes easy to overflow because the periphery of the discharge medium nozzle  54  is easy to be wetted, resulting that the amount of the quantification medium  45  capable of being accumulated increases. Furthermore, the force of repelling water is easy to produce differences between each channel because of the wear caused by cleaning operations of the head and the deterioration by aging. Namely, the force of repelling water is easy to be influenced by the variation of the state of the water repellent treatment, and the differences between each nozzle are large at the highest gradation value. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention aims at solving the aforementioned problems to provide a printer head, an ink jet printer and a method for driving a printer head capable of improving the mixing ratio of the quantification medium to the discharge medium, and capable of realizing the desired maximum density by making a high density mixed solution for a short time, and then capable of increasing unnecessary mixtures of colors. 
     According to a first aspect of the present invention, there is provided a printer head in an ink jet printer, comprises: a quantification medium pressuring chamber where a quantification medium is introduced; a discharge medium pressuring chamber where a discharge medium is introduced; a quantification medium nozzle communicating with the quantification medium pressuring chamber; a discharge medium nozzle communicating with the discharge medium pressuring chamber, the discharge medium nozzle being disposed to adjoin the quantification medium nozzle; and a first pressure generating element pulling the quantification medium pushed out of the quantification medium nozzle into the discharge medium nozzle to form a mixed solution by contacting the quantification medium in the discharge medium nozzle through a surface where the quantification medium nozzle opens, wherein the first pressure generating element then generates a pressure for discharging the mixed solution from the discharge medium nozzle. 
     According to the first aspect of the invention, since the quantification medium pushed out of the quantification medium nozzle is once pulled into the discharge medium nozzle forcibly, and then the mixed solution of the quantification medium and the discharge medium is discharged, the mixing ratio of the quantification medium and the discharge medium can be enhanced to enable the quantification of a great deal of quantification medium for a period. Furthermore, it is possible to make the mixed solution by mixing a great deal of quantification medium with the discharge medium for a short time. 
     According to a second aspect of the invention, there is provided an ink jet printer equipped with a printer head, wherein the printer head comprises: a quantification medium pressuring chamber where a quantification medium is introduced; a discharge medium pressuring chamber where a discharge medium is introduced; a quantification medium nozzle communicating with the quantification medium pressuring chamber; a discharge medium nozzle communicating with the discharge medium pressuring chamber; the discharge medium nozzle being disposed to adjoin the quantification medium nozzle; and a first pressure generating element pulling the quantification medium pushed out of the quantification medium nozzle into the discharge medium nozzle to form a mixed solution by contacting said quantification medium in the discharge medium nozzle through a surface where the quantification medium nozzle opens, wherein the first pressure generating element then generates a pressure for discharging the mixed solution from the discharge medium nozzle. 
     According to the second aspect of the invention, there can be obtained advantages similar to those of the first aspect of the invention. 
     According to a third aspect of the invention, there is provided a method for driving a printer head, the method comprises the steps of: moving a quantification medium pushed out of a quantification medium nozzle from the quantification medium nozzle to a discharge medium nozzle through a surface where the quantification medium nozzle opens; forming a mixed solution by pulling the quantification medium into the discharge medium nozzle to contact with the discharge medium in the discharge medium nozzle; and discharging the mixed solution from the discharge medium nozzle. 
     According to the third aspect of the invention, there can be obtained advantages similar to those of the first aspect of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and other objects, features and advantages of the present invention will become more apparent from the following description of the presently preferred exemplary embodiments of the invention taken in conjunction with the accompanying drawings, in which: 
     FIG. 1 is a perspective view showing an ink jet printer provided with a printer head of an embodiment according to the present invention; 
     FIG. 2 is a block diagram showing a printing and controlling system of the ink jet printer of FIG. 1; 
     FIG. 3 is a block diagram showing a driving circuit of the printer head shown in FIG. 1; 
     FIG. 4 is a sectional view showing the printer head shown in FIG. 1; 
     FIG. 5 is a plan view showing the printer head shown in FIG. 1; 
     FIG. 6 is a sectional view along VI—VI line of FIG. 4 showing the vicinity of the quantification medium nozzle in the printer head shown in FIG. 1; 
     FIG. 7 is a sectional view along VII—VII line of FIG. 4 showing the vicinity of the discharge medium nozzle in the printer head shown in FIG. 1; 
     FIG. 8 is a plan view showing the vicinity of the nozzles in the printer head shown in FIG. 1; 
     FIG. 9 is another plan view showing the vicinity of the nozzles in the printer head shown in FIG. 1; 
     FIG. 10 is a diagram showing a driving waveform of the qualification medium and a driving waveform of the discharge medium by the driving circuit of FIG. 3; 
     FIGS.  11 (A)- 11 (C) are mimetic views showing a state of waiting, a state of discharging the quantification medium and a state of coupling of the quantification medium and the discharge medium in the printer head shown in FIG. 1, respectively; 
     FIGS.  12 (A)- 12 (C) are mimetic views showing a state of pulling the discharge medium into the discharge medium nozzle, a state of completing pushing the quantification medium out of the quantification medium nozzle and a state of beginning to pull the quantification medium into the discharge medium nozzle in the printer head shown in FIG. 1, respectively; 
     FIGS.  13 (A)- 13 (C) are mimetic views showing a state of completing to pull the quantification medium and the discharge medium into the discharge medium nozzle, a state of discharging the discharge medium from the discharge medium nozzle and a state of waiting in the printer head shown in FIG. 1, respectively; 
     FIG. 14 is a diagram showing experimental examples of driving waveforms of the piezoelectric elements used in the printer head shown in FIG. 1 as pressure generating elements for a period and the displacement velocities of the piezoelectric elements; 
     FIG. 15 is a diagram showing an example of relationships between the displacement velocities of the piezoelectric elements each on the quantification medium side and on the discharge medium side, in particular, showing the relationships between the A 3  time of the displacement velocity on the quantification medium side and the B 1  time of the displacement velocity on the discharge medium side; 
     FIG. 16 is a diagram showing an example of relationships between the displacement velocities of the piezoelectric elements each on the quantification medium side and on the discharge medium side, in particular, showing the relationships between the A 1  time of the displacement velocity on the quantification medium side and the B 3  time of the displacement velocity on the discharge medium side. 
     FIGS.  17 (A) and  17 (B) are diagrams showing examples of simulation results of the discharge of the mixed solution of the quantified medium and the discharge medium in comparison of the conventional driving method (FIG.  17 (A)) and the driving method of the present invention (FIG.  17 (B)); 
     FIG. 18 is a chart illustrating results of an experiment according to the driving method of an embodiment of the present invention, showing mixing ratios of the quantification medium to the discharge medium according to the driving voltage of the quantification medium; 
     FIG. 19 is a timing chart showing waveforms of driving voltages applied to the piezoelectric elements of the printer head shown in FIG. 1; 
     FIG. 20 is a top view of an example of nozzle portion of a three colors mixing type carrier jet head type printer head; 
     FIG. 21 is a sectional view of a conventional printer head; 
     FIG. 22 is a timing chart showing driving voltages of the printer head of FIG. 21; 
     FIGS.  23 (A)- 23 (C) are mimetic views showing a state of waiting, a state of discharging the quantification medium and a state of coupling of the quantification medium and the discharge medium in the printer head of FIG. 21, respectively; 
     FIGS.  24 (A)- 24 (C) are mimetic views showing a state that a part of the quantification medium is remaining on the discharge medium nozzle after being separated, a state that the part of the quantification medium was mixed with the discharge medium in the discharge medium nozzle, and the state that the mixed solution begins to be pushed out in the printer head of FIG. 21, respectively; 
     FIGS.  25 (A)- 25 (C) are mimetic views showing a state that the mixed solution of the quantification medium and the discharge medium is pushed out, a state that a constriction begins to be produced between the mixed solution and the discharge medium, and a state that the mixed solution is discharged in the printer head of FIG. 21, respectively; 
     FIGS.  26 (A)- 26 (C) are mimetic views showing a state that the mixed solution in a sphere continues to fly, a state that the discharge medium is re-plugged in the discharge medium nozzle to be swollen thereon, and a state that the discharge medium has returned to the waiting state thereof in the printer head of FIG. 21, respectively; 
     FIG. 27 is a chart illustrating results of an experiment using the printer head shown in FIG. 21, showing mixing ratios of the quantification medium to the discharge medium according to the driving voltage of the quantification medium; and 
     FIGS.  28 (A)- 28 (C) are mimetic views showing a phenomenon that occurs in the vicinity of the quantification medium nozzle and the discharge medium nozzle in the unstable area of the printer head of FIG.  21 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hereinafter, preferred embodiments of the present invention will be described in detail on the attached drawings. 
     Now, the drawings are referred while a printer head and an ink jet printer, each is an embodiment of the present invention, will be described in detail. 
     In this specification, the so-called carrier jet type printer that uses ink as the quantification medium and uses diluent as the discharge medium will be described. 
     An ink jet printer  100  is the so-called serial type printer, and, as shown in FIG. 1, the printer  100  is mainly composed of a drum  2  for supporting a sheet of print paper  1  to be printed, and a printer head  3  for printing on the printer paper  1 . 
     The print paper  1  is held by being pressed to the drum  2  by a paper pressing roller  4  disposed parallel to the axial direction of the drum  2 . Besides, a feed screw  5  is disposed parallel to the axial direction of the drum  2  in the vicinity of the outer periphery of the drum  2 . The printer head  3  is held around the feed screw  5 . The printer head  3  is driven to move along the axial direction of the drum  2  indicated by an arrow M in FIG. 1 by the rotation of the feed screw  5 . 
     On the other hand, the drum  2  is driven to rotate in the direction indicated by an arrow m in FIG. 1 by a motor  9  through a pulley  6 , a belt  7  and a pulley  8 . Moreover, the rotations of the feed screw  5  and the motor  9 , and the printer head  3  are driven to be controlled on printing data and control signals by a control section  10  for head-driving, the control of head-feeding and the control of drum-rotating. 
     With the aforementioned structure, when the printer head  3  moves and has completes printing of a line, the drum  2  is rotated by a line for the following print. In case of printing a picture, the printer head  3  moves to only one direction or to back and forth directions. 
     FIG. 2 is a block diagram showing a printing and controlling system of the ink jet printer  100 . The ink jet printer  100  is controlled by the control section  10  shown in FIG.  2 . The control section  10  is composed of a signal process control circuit  22 , a first driver  23 , a second driver  24 , a memory  25 , a correcting circuit  26  and a control drive section  27 . The signal process control circuit  22  is composed of a central processing unit (CPU) or a digital signal processor (DSP). 
     Those first driver  23  and second driver  24  are equipped in accordance with the number of the quantification medium nozzles and the discharge medium nozzles, respectively. The first driver  23  drives a first laminated type piezoelectric element for controlling it, which element to be described later is a first pressure imposing means equipped for pushing the quantification medium out of the quantification medium nozzle. 
     The second driver  24  drives a second laminated type piezoelectric element for controlling it, which element to be described later is a second pressure imposing means equipped for discharging the discharge medium out of the discharge medium nozzle. Incidentally, either of the aforementioned quantification side or the discharge side is ink, and the other is diluent. 
     Each of the first driver  23  and the second driver  24  drives the first and second pressure imposing means respectively corresponding to the first and the second driver  23  and  24  on the control of a serial-parallel conversion circuit and a timing control circuit, both of which will be described later and are equipped in the signal process control circuit  22 . 
     And further, a signal source  21  supplies such as printing data, an operation section signal and an external control signal into the signal process control circuit  22  in the control section  10  to be stored in the signal process control circuit  22  in the order of printing. The stored signals are outputted to the printer head  3  through the first and second drivers  23  and  24  to drive the printer head  3  for controlling it. The order of printing differs in accordance with structures of the printer head  3  and a printing section, and further relates to the order of inputting the printing data, too. The signals to be stored are once re-recorded in a memory  25  such as a line buffer memory or one picture memory as occasion demands, and then are read out from the memory  25 . 
     Incidentally, in the case where there are great numbers of nozzles used in a multi-head, for example, an integrated circuit (IC) is equipped in the printer head  3  to decrease the number of wires to be connected to the printer head  3 . In addition, the correcting circuit  26  is connected to the signal process control circuit  22  for performing γ-correction, color correction in case of a colored picture, correction of differences among respective heads, and the like. Correction data selected in advance are generally memorized in a read only memory (ROM) in the correcting circuit  26  into a map format to be taken out in accordance with external conditions such as a nozzle number, temperature and input signals. 
     The signal process control circuit  22  is generally composed of a CPU or a DSP as stated above to operate in conformity with software. A signal processed by the signal process control circuit  22  is sent to the control drive section  27 . The control drive section  27  executes such operations as driving the motor  9  that drives the drum  2  and the feed screw  5  to rotate, synchronization, cleaning the printer head  3 , supplying a sheet of print paper and ejecting the paper. In addition, it goes without saying that the signals supplied from the signal source  21  include an operation signal or an external signal other than the printing data. 
     Next, an example of a driving circuit of the aforesaid printer head is shown in FIG.  3 . Digital halftone data are supplied to a serial-parallel conversion circuit  31  from another block, and then are sent to the first driver  23  and the second driver  24  from the serial-parallel conversion circuit  31 . The first driver  23  is connected to the first laminated type piezoelectric element  43 , and the second driver  24  is connected to the second laminated type piezoelectric element  44 . The first and second drivers  23  and  24  do not execute their quantification operation and discharge operation, respectively, when the digital halftone data supplied from the serial-parallel conversion circuit  31  is a predetermined threshold value or below. When it becomes a printing timing, a print trigger is issued from another block to be detected by the timing control circuit  32 . Then the timing control circuit  32  outputs a quantification section control signal and a discharge control signal to the first driver  23  and the second driver  24 , respectively. 
     Next, the description will be done about the printer head  3  in the ink jet printer  100 . 
     The printer head  3 , as shown in FIG. 4, is mainly composed of a nozzle plate  41 , the diaphragm  42 , the first laminated type piezoelectric element  43  and the second laminated type piezoelectric element  44 . 
     The nozzle plate  41  is made from a resin. A first concave portion  46  forming a quantification medium liquid chamber where the quantification medium  45 , e.g. ink, is supplied and a second concave portion  47  forming a quantification medium pressing chamber where the aforesaid quantification medium  45  is plugged are formed in the nozzle plate  41  so that the first and second concave portions  46  and  47  are open to a surface  41   a  on the diaphragm  42  side. A first supplying passage  48  connects a side face of the first concave portion  46  and a side face of the second concave portion  47  opposite to the side face of the first concave portion  46  to be formed as a through-hole substantially parallel to the surface  41   a.    
     Furthermore, a third concave portion  50  forming a discharge medium liquid chamber for, e.g. a diluent, and a fourth concave portion  51  forming a discharge medium pressuring chamber where a aforesaid discharge medium  49  is plugged are formed to be open to the surface  41   a  on the diaphragm  42  side. A second supplying passage  52  connects a side face of the third concave portion  50  and a side face of the fourth concave portion  51  opposed to the side face of the third concave portion  50  to be formed as a through-hole substantially parallel to the surface  41   a.    
     Furthermore, in the nozzle plate  41 , the quantification medium nozzle  53  is formed as a through-hole formed in an oblique direction to the thickness direction of the nozzle plate  41  from the bottom face side of the second concave portion  47  to a surface  41   b  on the opposite side of the diaphragm  42 , and similarly the discharge medium nozzle  54  is formed as a through-hole formed in the thickness direction of the nozzle plate  41  from the bottom face side of the fourth concave portion  51  to the surface  41   b  on the opposite side of the diaphragm  42 . 
     By disposing the diaphragm  42  so as to cover the aforesaid each concave portion, a space formed between the first concave portion  46  and the diaphragm  42  is shaped as a quantification medium liquid chamber  55 , and a space formed between the second concave portion  47  and the diaphragm  42  is shaped as a quantification medium pressuring chamber  56 , and then, as also shown in FIG. 5, the quantification medium liquid chamber  55 , the first supplying passage  48 , the quantification medium pressuring chamber  56  and the quantification medium nozzle  53  are formed as a continuous space. 
     A space formed between the third concave portion  51  and the diaphragm  42  as a discharge medium liquid chamber  57 , and a space formed between the fourth concave portion  51  and the diaphragm  42  is shaped as a discharge medium pressuring chamber  58 , and then, as also shown in FIG. 5, the discharge medium liquid chamber  57 , the second supplying passage  52 , the discharge medium pressuring chamber  58  and the discharge medium nozzle  54  are formed as a continuous space. 
     FIG. 5 is a plan view showing a state that the first piezoelectric element  43  is disposed on the quantification side. FIG. 5 also shows plan view when the nozzle plate  41  is observed from the surface  41   a  side on the discharge side. 
     Incidentally, as shown in FIG. 4, an annular concave portion  59  is formed on the top surface of the diaphragm  42  at a position corresponding to the outer periphery portion of the quantification medium pressuring chamber  56 , and also an annular concave portion  60  is formed on the top surface of the diaphragm  42  at a position corresponding to the outer periphery portion of the discharge medium pressuring chamber  58 . Consequently, when the diaphragm  42  is overlooked from the upper side, as shown on the quantification side of FIG. 5, a projecting portion  61  is formed at a position corresponding to the quantification medium pressuring chamber  56  and the first laminated type piezoelectric element  43  is disposed on the projecting portion  61 . This situation is similar in the discharge side. That is, as shown in FIG. 4, a projecting portion  62  is formed inside the surrounding concave portion  60 , and the second laminated type piezoelectric element  44  is disposed on the projecting portion  62 . 
     In the printer head  3 , the quantification medium nozzle  53  is formed in the oblique direction to the thickness direction of the nozzle plate  41  as described above, and the discharge medium nozzle  54  is formed in the thickness direction of the nozzle plate  41 . Consequently, the printer head  3  is constructed so that the nearer a position in the thickness direction of the nozzle plate  41  becomes to the surface  41   b  where the nozzles  53  and  54  open, the nearer the quantification medium nozzle  53  approaches to the discharge medium nozzle  54 . 
     On the surface  41   b  where the nozzles  53  and  54  are open, the openings of the nozzles  53  and  54  adjoin. Incidentally, an angle formed by the central lines of the quantification medium nozzle  53  and the discharge medium nozzle  54  is set as for example 30°. 
     Incidentally, as also shown in FIG. 6, which is a sectional view of the quantification medium nozzle  53  sectioned along the VI—VI line in FIG. 4, the quantification medium nozzle  53  is comprised of a first tapered nozzle portion  63  where both inside walls thereof are formed to have a taper so that the width between both the walls becomes narrower as a position in the thickness direction of the nozzle plate  41  approaches to the surface  41   b  from the bottom face of the quantification medium pressuring chamber  56 , and a first nozzle portion  64  formed continuously to the tip of the first tapered nozzle portion  63  as a practical nozzle. 
     Furthermore, as also shown in FIG. 7, which is a sectional view of the discharge medium nozzle  54  sectioned along the VII—VII line in FIG. 4, the discharge medium nozzle  54  is comprised of a second tapered nozzle portion  65  where both inside walls thereof are formed to have a taper so that the width between both the walls becomes narrower as a position in the thickness direction of the nozzle plate  41  approaches to the surface  41   b  from the bottom face of the discharge medium pressuring chamber  58 , and a second nozzle portion  66  formed continuously to the tip of the second tapered nozzle portion  65  as a practical nozzle. 
     By forming the first tapered nozzle portion  63  and the second tapered nozzle portion  65  like this, the flow path resistances of the quantification medium nozzle  53  and the discharge medium nozzle  54  decrease. Consequently, the smooth flow of the liquid can be realized, and in particular, the effect of preventing air bubbles from remaining in the nozzles when ink and diluent is first plugged therein. 
     In FIG. 4, the quantification medium  45 , e.g. ink, is plugged in the quantification medium nozzle  53  from a quantification medium tank, not shown, through the quantification medium liquid chamber  55 , the first supplying passage  48  and the quantification medium pressuring chamber  56 . 
     On the other hand, the discharge medium  49 , i.e. diluent, is plugged in the discharge medium nozzle  54  from a discharge medium tank, not shown, through the discharge medium liquid chamber  57 , the second supplying passage  52  and the discharge medium pressuring chamber  58 . 
     Water repellent finishing is formed on the surface  41   b  of the nozzle plate  41  where the nozzles  53  and  54  of the printer head  3  open for preventing the ink and the diluent around the nozzles  53  and  54  from wetting to enhance the stability of discharging the liquid droplets and the accuracy of the discharging direction. 
     In the printer head  3 , in particular, the shape of the opening of the quantification medium nozzle  53  is formed as a shape including a notch on the side of the discharge medium nozzle  54 . 
     In other words, the shape of the opening of the quantification medium nozzle  53  is formed so that the minimum distance between the center of an inscribed circle contacting the opening of the quantification medium nozzle  53  and the edge of the opening of the discharge medium nozzle  54  is larger than the minimum distance between the center of a circumscribed circle contacting the opening of the quantification medium nozzle  53  and the edge of the opening of the discharge medium nozzle  54 . 
     Now, as shown in FIG. 8, it is supposed that the shape of the opening of the second nozzle portion  66  of the discharge medium nozzle  54  is a circle, and that the shape of the opening of the first nozzle portion  64  of the discharge medium nozzle  53  is a partially eclipsed shape. In such a shape, the minimum distance d 2  between the center O 2  of an inscribed circle  68  shown by a broken line in FIG. 8, which circle  68  contacts with an opening of the first nozzle  53 , and the opening of the discharge medium nozzle  54  is larger than the minimum distance d 1  between the center O 1  of a circumscribed circle  67  shown by an alternate dot and dashed line in FIG. 8, which circle  67  contacts with an opening of the first nozzle portion  64 , i.e. the opening of the quantification medium nozzle  53 , and the opening of the discharge medium nozzle  54 . 
     As shown in FIG. 9, since the shape of the opening of the first nozzle portion  64  of the quantification medium nozzle  53  is assumed to be a partially eclipsed shape, in such a shape, an edge O 4  of an opening nearest to the center O 3  of the shape of the opening of the first nozzle portion  64 , i.e. the opening of the quantification medium nozzle  53 , is on the side of the second nozzle  66 , i.e. the opening of the discharge medium nozzle  54 . 
     In FIGS. 8 and 9, only one couple of the couples of the quantification medium nozzle  53  and the discharge medium nozzle  54  is shown, however, a plurality of the couples, e.g. 32 couples, are equipped in the present invention. Those quantification medium nozzles  53  and the discharge medium nozzles  54  are disposed so that a quantification medium nozzle  53  of one couple adjoins another quantification medium nozzle  53  of another couple, and a discharge medium nozzle  54  of one couple adjoins another discharge medium nozzle of another couple. 
     FIGS.  11 (A)- 13 (C) show mimetically an example of a method for driving a quantification medium and the discharge medium by the printer head  3  in the ink jet printer of the present embodiment. 
     FIG.  11 (A) shows a waiting state, in which the surfaces of the quantification medium  45  and the discharge medium  49  form a little bit concave meniscus by a negative static pressure owing to an ink supplying system, not shown. 
     In the state shown in FIG.  11 (B), the quantification medium  45  begins to be pushed out of the quantification medium nozzle  53 . 
     The pushed out quantification medium  45  shown in FIG.  11 (C) overflows on the discharge medium nozzle  54  owing to the obliquity of the quantification medium nozzle  53  to the discharge medium nozzle  54  and the effect of the crescent shape of the quantification medium nozzle  53 , i.e. a force impelling the quantification medium to be a sphere due to the surface tension. The overflowed quantification medium  45  contacts with the discharge medium  49  to be combined with the discharge medium  49  owing to the surface tension. 
     FIG.  12 (A) shows a state that the discharge medium  49  is drawn into the discharge medium nozzle  54 . The quantification medium  45  existing on the discharge medium nozzle  49  and the successively pushed out quantification medium  45  are also forced to be drawn into the discharge medium nozzle  54  together with the discharge medium  49 . 
     In the state shown in FIG.  12 (B), the pushing out of the quantification medium  45  is completed. 
     In the state shown in FIG.  12 (C), the quantification medium  45  begins to be pulled into the discharge medium nozzle  54 . By the pulling of the quantification medium  45  into the discharge medium nozzle  54 , the discharge medium  49  and the quantification medium  45  is separated and the meniscus of the quantification  45  recedes into the quantification medium nozzle  53 . The meniscus of the discharge medium  49  also continues being pulled into the discharge medium nozzle  54 . 
     FIG.  13 (A) shows a state that the pulls of the quantification medium  45  and the discharge medium  49  into the discharge medium nozzle  54  are completed. 
     FIG.  13 (B) shows a state that the discharge medium  49  is discharged. The mixed solution  69 , which is a mixture of the quantification medium  45  and the discharge medium  49  that were mixed together on the tip of the discharge medium nozzle  54 , is discharged from the discharge medium nozzle  54 . 
     In a state shown in FIG.  13 (C), the vibration of the meniscus after being discharged decreases to return to the state of waiting. 
     Driving waveforms of the piezoelectric elements (PZT) for performing the aforesaid driving are shown in FIG.  10 . FIG.  10  and FIGS.  11 (A)- 13 (C) will be referred while the states of driving the quantification medium  45  and the discharge medium  49  will be described. 
     (1) A positive voltage, e.g. 20 V in the present embodiment, is previously imposed on the first piezoelectric element  43  on the quantification side in a waiting state (see FIG.  11 (A)), and the first piezoelectric element  43  is in a state of being shrunken in the displacement direction, i.e. in the direction perpendicular to the diaphragm  42 . Namely, the volume of the quantification medium pressuring chamber  56  is in a state of being swollen. On the second piezoelectric element  41  there is no voltage imposed, and the second piezoelectric element is in its initial state. 
     (2) The voltage imposed on the first piezoelectric element  43  begins to decrease. The internal pressure of the quantification medium pressuring chamber  56  begins to increase to start the pressuring of the quantification medium  45  (see FIG.  11 (B)). 
     (3) The quantification medium  45  is pushed out on the discharge medium nozzle  53  to contact with the discharge medium  49 , and then they are combined together by the surface tension (see FIG.  11 (C)). 
     (4) The voltage of the second piezoelectric element  44  on the discharge side is gradually being increased. The second piezoelectric element  44  on the discharge side begins to shrink, and the discharge medium pressuring chamber  58  begins to swell. The internal pressure of the discharge medium pressuring chamber  58  decreases, and then the discharge medium  49  and the quantified quantification medium  45  is pulled into the discharge medium nozzle  54  (see FIG.  12 (A)). 
     (5) The lowering of the voltage imposed on the first piezoelectric element  43  on the quantification side is completed (see FIG.  12 (B)). 
     (6) By imposing again on the first piezoelectric element  43  on the quantification side, the piezoelectric element is made to be shrunken and the volume of the quantification medium pressuring chamber  56  is made to be swollen. The internal pressure of the quantification medium pressuring chamber  56  is lowered, and then the quantification medium  45  is pulled into the quantification medium nozzle  53 . The quantification medium  45  and the discharge medium  49  is separated (see FIG.  12 (C)). 
     (7) The rising of the voltages imposed on the second piezoelectric element  44  on the discharge side and the first piezoelectric element  43  on the quantification side is completed. The pulling of the discharge medium  49  and the quantification medium  45  into the nozzles  53  and  54  is completed (see FIG.  13 (A)). 
     (8) By lowering the voltage imposed on the second piezoelectric element  44  on the discharge side, the second piezoelectric element  44  is made to be elongated, and the volume of the discharge medium pressuring chamber  58  is made to be shrunken. The internal pressure of the discharge medium pressuring chamber  58  rises to discharge the mixed solution  69  (see FIG.  13 (B)). 
     (9) The voltages imposed on both the first and second piezoelectric elements  43  and  44  return to the initial values, respectively. The vibration of the meniscus decreases to return to the initial state (see FIG.  13 (C)). 
     By driving the first and second piezoelectric elements  43  and  44  as mentioned above, the quantification medium  45  pushed out on the discharge medium nozzle  54  does not overflow around the discharge medium nozzle  54  to be pulled into the discharge medium nozzle  54 , and then the more amount of the quantification medium  45  can be quantified. 
     In other words, the mixing ratio of the quantification medium  45  included in the discharged liquid droplets can be increased. Although the upper limit of the conventional mixing ratio of ink is about 40-50% for obtaining the stable discharging (see FIG.  27 ), as shown in FIG. 18, the mixing ratio of about 80% can be obtained as the maximum percentage according to the driving method of the present invention. 
     In the case where ink is used as the quantification medium  45  and the diluent is used as the discharge medium  49 , recording in higher density can be realized. Or, the density of coloring material of ink can be set as a lower density for obtaining the same density. This fact makes it very advantageous to design the ink in respect of bodying owing to the deposition or precipitation of a dye or a pigment, or dehydration. 
     Although a dye having a high resistance to light, e.g. a dye of cyan of the phtalocyanine group, has a tendency to make the printing density low, such a dye can be used according to the present invention because present invention can set the mixing ration to be high. Even if such a dye is used, practical printing densities can be obtained by the present invention. 
     Furthermore, since the quantification medium  45  is forcibly pulled into the discharge medium nozzle  54 , the quantified quantification medium  45  can be discharge without waiting being pulled into the discharge medium nozzle  54  by the surface tension as in the prior art. Consequently, the period of discharging can be shortened by the waiting time, and then the time required for printing can be shortened. 
     Now, for positively producing the phenomenon that the quantification medium  45  flows into the discharge medium nozzle  54  when the mixed solution is produced by combining the quantification medium  45  and the discharge medium  49  as shown in FIG.  11 (C), the operation on the discharge medium  49  side during points of time indicated the reference numerals ( 3 )-( 7 ) in FIG. 10 is preferred to be executed while the operation on the quantification medium  45  side during points of time indicated by reference numerals ( 2 )-( 7 ) in FIG. 10 is executed. 
     FIG. 14 shows experimental examples of driving waveforms of the piezoelectric elements used in the printer head shown in FIG. 1 as pressure generating elements for a period and the displacement velocities of the piezoelectric elements. As shown in FIG. 14, for the first piezoelectric element  43 , period A 3  designates a pushing out time, period A 2  designates a waiting time, and period A 3  designates a suction time. For the second piezoelectric element  44 , period B 1  designates a suction time, period B 2  designates a waiting time, and period B 3  designates a discharge time. 
     FIG. 15 shows a fact that relationships between the displacement velocities of the first piezoelectric element  43  and the second piezoelectric element  44 , in particular, the relationships between A 3  period, i.e. during points of time indicated by reference numerals ( 2 )-( 6 ), and B 1  period, i.e. during points of time indicated by reference numeral ( 3 )-( 5 ), can be examined on the following five kinds of patterns a-e. 
     a: (3)→(2)→(5)→(6)((3)&lt;(2), (2)≦(5)&lt;(6)) 
     b: (2)→(3)→(5)→(6)((3)≧(2), (5)≦(6)) 
     c: (2)→(3)→(6)→(5)((2)≦(3)≦(6), (5)&gt;(6)) 
     d: (3)→(2)→(6)→(5) 
     e: (3)→(2)→(6)→(5)((3)&lt;(2), (5)≧(6)) 
     Incidentally, it is supposed that the relationship, (3)&lt;(5), is always satisfied owing to the structure of the waveforms. 
     By driving the piezoelectric elements  43  and  44  at the timing in conformity with the waveforms shown in FIG. 15, the quantification medium  45  flows into the discharge medium nozzle  54  for periods of time indicated by reference numerals ( 2 )-( 5 ) in case of a in FIG. 15, periods of time indicated by reference numerals ( 3 )-( 5 ) in case of b in FIG. 15, periods of time indicated by reference numerals ( 3 )-( 6 ) in case of c in FIG. 15, periods of time indicated by reference numerals ( 2 )-( 6 ) in case of d in FIG. 15, and periods of time indicated by reference numerals ( 2 )-( 6 ) in case of e in FIG.  15 . 
     In addition, for stabilizing the direction of the discharged mixed solution  69 , the operation for separating the connection between the quantification medium  45  and the discharge medium  49  on the surface  41   b  of the nozzle plate  41 , as shown in FIG.  12 (C), is preferred to be executed positively, namely an operation for separating the connection is required to be executed such as an operation for periods of time indicated by reference numerals ( 8 )-( 9 ) in FIG. 16, which will be described later, on the quantification medium  45  side and an operation for periods of time indicated by reference numerals ( 9 )-(l 2 ) in FIG. 16 on the discharge medium  49  side. 
     FIG. 16 shows a fact that relationships between the displacement velocities of the first piezoelectric element  43  and the second piezoelectric element  44 , in particular, the relationships between A 1  period, i.e. during points of time indicated by reference numerals ( 8 )-( 11 ), and B 3  period, i.e. during points of time indicated by reference numeral ( 9 )-(l 2 ), can be examined on the following four kinds of patterns a′-d′. 
     a′: (8)→(9)→(12)→(11)((8)≦(9), (12)&lt;(11)) 
     b′: (8)→(9)→(11)→(12)((9)&lt;(11), (12)≧(11)) 
     c′: (8)→(11)→(9)→(12)((9)≧(11)) 
     d′: (9)→(12) 
     The quantification medium  45  is pulled into the quantification medium  53  from the surface  41   b  of the nozzle plate  41  into the quantification medium nozzle  53 , and the first piezoelectric element  43  and the second piezoelectric element  44  are operated so that bubbles are not mixed into the quantification medium nozzle  53 . 
     The operation of discharging the discharge medium  49  is executed while the quantification medium  45  is pulled into the quantification medium nozzle  53  in case of a′ in FIG. 16 because periods of time indicated by reference numerals ( 9 ) and ( 12 ) are within the periods of time indicated by reference numerals ( 8 )-( 11 ). 
     In case of b′ and c′ in FIG. 16, the operation of discharging the discharge medium  49  starts at a point of time for the operation of pulling the quantification medium  45  into the quantification medium nozzle  53  during a period of time indicated by reference numerals ( 8 )-( 11 ) and ends at a point of time after the operation of pulling the quantification medium  45  ended (( 11 )-( 12 )). 
     In case of d′ in FIG. 16, the operation of discharging the discharge medium  49  is performed after the mixed solution  69  and the quantification medium  45  is separated by pulling the quantification medium  45  into the quantification medium nozzle  53  for periods of time indicated by reference numerals ( 8 )-( 11 ). 
     The operations performed in conformity with the timing chart of each pattern of a′, b′, c′ and d′ in FIG. 16 may be done so that the mixed solution  69  is discharged in the direction of the discharge medium nozzle  54 , i.e. the normal direction to the surface  41   b  of the nozzle plate  41 , in a state that the meniscus is completely separated from the quantification medium  45 . 
     FIGS.  17 (A) and  17 (B) shows simulation results of the discharge of the mixed solution  49  in comparison of the conventional driving method and the driving method of the present invention. 
     FIG.  17 (A) is a diagram showing the simulation results of the discharge of the mixed solution  49  in accordance with the conventional driving method. By setting the time when the quantification begins to be 0, the quantified ink overflows onto the opposite side of the discharge medium nozzle  54  to the quantification medium nozzle  53  at the time of 40 μs. The overflowed ink remains after discharging at the time of 100 μs. It is also known that liquid droplets are drawn to the remaining ink to curve the direction of discharging of the liquid droplets to the direction of the remaining ink. 
     FIG.  17 (B) is a diagram showing the simulation results of the discharge of the mixed solution  49  in accordance with the driving method of the present invention. The overflow of ink is prevented by pulling the quantified ink into the discharge medium nozzle  54  for a period of 15 μs-75 μs together with diluent, i.e. discharge medium  49 . Furthermore, the diluent and the ink are completely separated by pulling the ink for a period 70 μs-75 μs after quantification. As the result, there remains no mixed ink, and the mixing ration of the ink can be set to be high. Furthermore, the discharging direction of the liquid droplets is enhanced to go straight on. Incidentally, in the present simulation, the amount of pushing of the ink is supposed to be 30 pl, and the amount of discharging is supposed to be 60 pl. 
     FIG. 19 shows waveforms of driving voltages according to a driving method of the present invention. The waveforms correspond to the cases of c in FIG.  15  and a′ in FIG.  16 . 
     Executing an experiment according to the driving method of an embodiment of the present invention results in the data as shown in FIG.  18 . The results indicate that the mixing ratio of ink can be heighten up to about 80% with keeping the stable discharge, in comparison with conventional data shown in FIG.  27 . 
     The ink as the quantification medium  45  and the diluent as the discharge medium  49  in the printer of the embodiment may have the following composition and properties. 
     
       
         
               
             
               
               
               
               
             
               
             
               
               
               
               
             
           
               
                   
               
             
             
               
                 &lt;COMPOSITION&gt; 
               
             
          
           
               
                   
                 C. I. acid blue 9 
                 8 
                 weight % 
               
               
                   
                 N-methyl-2-pyrrolidone 
                 10 
                 weight % 
               
               
                   
                 ethylene glycol mono-methyl ether 
                 10 
                 weight % 
               
               
                   
                 surface active agent 
                 0.01 
                 weight % 
               
               
                   
                 water 
                 81.99 
                 weight % 
               
             
          
           
               
                 &lt;PROPERTIES&gt; 
               
             
          
           
               
                   
                 viscosity 
                 2 
                 cp 
               
               
                   
                 surface tension 
                 30 
                 dyne/cm at 20° C. 
               
               
                   
                   
               
             
          
         
       
     
     On the other hand, the diluent may have the following composition and properties. 
     
       
         
               
             
               
               
               
               
             
               
             
               
               
               
               
             
           
               
                   
               
             
             
               
                 &lt;COMPOSITION&gt; 
               
             
          
           
               
                   
                 isopropyl alcohol 
                 7 
                 weight % 
               
               
                   
                 diethylene glycol 
                 23 
                 weight % 
               
               
                   
                 water 
                 70 
                 weight % 
               
             
          
           
               
                 &lt;PROPERTIES&gt; 
               
             
          
           
               
                   
                 viscosity 
                 2.2 
                 cp 
               
               
                   
                 surface tension 
                 40 
                 dyne/cm at 20° C. 
               
               
                   
                   
               
             
          
         
       
     
     Although it was described that the embodiment uses the cyano-colored dye, it need scarcely be said that other colors may be used. Ordinary paper, paper for ink jet printers on the market may be used as the material to be printed thereon. 
     &lt;EMBODIMENT OF THREE COLORS MIXED HEAD&gt; 
     The driving method according to the present invention is effectively applicable to a multi-color mixing type carrier jet head equipped with quantification medium nozzles  101 ,  102 ,  103  having a crescent shape including a partially eclipsed part, which nozzles are disposed in order around the discharge medium nozzle  104  for three colors of cyan blue, magenta and yellow, respectively, or for four colors including black together with the aforesaid three colors, as shown in FIG. 20, which carrier jet head begins discharging mixed solution for printing after mixing three or four colors in a discharge medium nozzle  104 . 
     In such a structure as that of the aforementioned printer head, the distance between the adjacent quantification media  100  is short, and thereby unnecessary color mixing easily happens owing to the overflow of the quantification media and the discharge medium in the vicinity of the outlets of the nozzles  101 - 104 . However, according to the driving method of the present invention, because the smooth flow of the quantification media to the vicinity of the discharge medium nozzle  101  can be formed, the overflow of quantification media does not occur. Consequently, picture printing without color mixing between quantification media is enabled. 
     And then, the quantification medium to be mixed with the discharge medium is pushed out of the quantification medium nozzle corresponding to it. On the other hand, the quantification media that are not mixed with the discharge medium are pulled into the quantification medium nozzles corresponding to them, respectively. And then, the piezoelectric element as a pressure generating element discharge the discharge medium to be mixed from the discharge medium nozzle  104 . Consequently, unnecessary color mixing can be prevented. 
     In an ink jet printer according to the present invention, a laminated type piezoelectric element is used as the pressure generating means, other pressure generating means such as the so-called veneer piezoelectric element, a heating element and a magnetostrictive element may be used. It is also capable that different kinds of pressure generating means are used on the quantification side and the discharge side, respectively. 
     Incidentally, in the ink jet printer according to the present invention, aforementioned examples can be used as a combination of them. Various variations are of course applicable without departing from the sprit of the present invention. 
     As description was made about a serial type printer as an embodiment of the invention, it goes without saying that the present invention is applicable to a line type printer or a drum type printer. 
     The following advantages can be obtained by using the driving method of an embodiment of the invention. 
     ENHANCEMENT OF THE AMOUNT OF QUANTIFICATION 
     As shown in FIG. 18, the mixing ratio of the quantification medium in a stable area is enhanced. In comparison with a slow flow of the quantification medium into the discharge medium nozzle owing to the capillary force as in the prior art, it is capable of generating a rapid flow of the quantification medium into the discharge medium nozzle actively. Consequently, a large quantity of quantification medium can be quantified for one period in comparison with the prior art. 
     IMPROVEMENT OF FREQUENCY CHARACTERISTICS 
     As mentioned above, by producing a rapid flow of the quantification medium, reproduction of high density becomes possible during a short period, according to the present invention. That is, it becomes possible to increase the driving frequency of a head. 
     CAPABILITY OF USING INK IN MORE STABLE STATE 
     Coloring ability tends to be enhanced when the density of a dye included in ink is high. On the other hand, the dye is easy to be saturated and to be deposited in the ink when the density is high. Because ink can be used in a state that the density of the dye included in the ink is lowered than that of the prior art when a great deal of the ink can be quantified at the time of realizing the maximum density thereof, it becomes possible to use the ink in a stable area. 
     WIDENING OF RANGE OF APPLICABLE DYES 
     Even if a dye is unstable and easy to be saturated, the desired maximum density can be expressed by using ink in a stable low density of the dye and quantifying a great deal of the ink. 
     DECREASE IN COLOR MIXING IN MULTI COLORS MIXING TYPE CARRIER JET HEAD 
     Performing a quantification operation with flow decreases the overflow of the quantification medium around a nozzle. Consequently, the contact of each medium between adjoining quantification nozzles decreases to decrease unnecessary color mixing in turn. 
     DECREASE DIFFERENCES BETWEEN NOZZLES 
     In prior art, the quantification medium is once accumulated on the discharge medium nozzle, and then the accumulated quantification medium is pulled into the discharge medium nozzle by a capillary force for discharging the mixed liquid. That is, the operation of “accumulation” is required in a cycle. However, according the present invention, the “accumulation” operation becomes unnecessary. The “accumulation” operation is strongly influenced by surface processing such as a repellent treatment around the discharge medium nozzle. When the effect of the repellent treatment is strong, the amount of the quantification medium capable of being accumulated, i.e. capable of being quantified, becomes much, and when the repellent treatment is not done, the quantification medium becomes easy to overflow and then the amount of the quantification medium capable of being accumulated becomes small. Furthermore, the repellent treatment is easy to produce differences between respective nozzles owing to the wear produced by the cleaning operation of a head and deterioration by aging. 
     Hence, the driving method according to the present invention without the “accumulation” operation can decrease the influences of the differences caused by the repellent treatment, and thereby can decrease the variation of the discharge direction due to the overflow and the cases where the mixed liquid is not discharged. 
     According to the conventional method for driving a carrier jet head, ink pushed out of the quantification medium nozzle is mounted on the discharge medium nozzle, and then the quantification medium is pulled into the nozzle by the capillary force to be discharged. If ink more than a certain amount is tried to be quantified, the ink that cannot mount on the discharge medium nozzle overflows. As a result, phenomena such as disturbances of the direction of discharging and no discharging occur. 
     However, according to the present invention, even if the amount of the ink to be quantified is large, the ink does not overflow around the nozzle. 
     Although the invention has been described in its preferred form with a certain degree of particularity, obviously many changes and variations are possible therein. It is therefore to be understood that the present invention may be practiced otherwise than as specifically described herein without departing from the scope and the sprit thereof.