Abstract:
The present invention relates to an ink jet printer for display device fabrication, and more particularly, to an apparatus and a method of driving an ink jet printer for manufacturing a display device. According to a first embodiment of the present invention, an apparatus of driving an ink jet printer for manufacturing a display device includes a timing control unit outputting a timing control signal by receiving a prescribed signal (IN) inputted from outside, a head drive unit receiving the timing control signal outputted from the timing control unit and a prescribed drive voltage (Vh), the head drive unit outputting a drive pulse of a predetermined voltage level, and an array resistor outputting a head drive voltage to a plurality of heads by receiving the drive pulse outputted from the head drive unit, wherein the head drive voltage outputted from the array resistor maintains a predefined voltage value. Therefore, the sustainability and reliance of the head can be enhanced by preventing the ink blocking or missing channel in a manner of equalizing the frequency of the drive pulse applied in printing the ink to that of the printing pulse applied in the standby mode and consecutively applying the drive and priming pulses of the same frequency to equalize the ink circulation condition.

Description:
[0001]     This Nonprovisional application claims priority under 35 U.S.C. §119(a) on Patent Application No. 10-2003-0077610 filed in Korea on Nov. 4, 2003, Patent Application No. 10-2003-0078389 filed in Korea on Nov. 6, 2003, and Patent Application No. 10-2003-0089831 filed in Korea on Dec. 10, 2003, the entire contents of which are hereby incorporated by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to an ink jet printer for display device fabrication, and more particularly, to an apparatus and a method of driving an ink jet printer for manufacturing a, display device.  
         [0004]     2. Description of the Background Art  
         [0005]     Recently, in accordance with the developments and wide spread of information processing systems, importance of a display device as a visual information transfer means rises. Specifically, a cathode ray tube (CRT) has a big size, a high operational voltage, and such a technical difficulty as display distortion and the like, thereby failing to meet the recent tendency toward wide size and flatness of screen. Hence, many efforts are made to develop various flat display devices having a matrix structure each.  
         [0006]     A plasma display panel (hereinafter abbreviated PDP) as a flat display device displays pictorial images including characters and graphics in a manner of exciting phosphor to emit light by ultraviolet rays generated from discharge of inert gas such as He+Xe and Ne+Xe. The PDP facilitates to enable a wide-screen and has such a feature as high display quality and fast response speed. And, the PDP enables its thin and slim-size implementations, thereby coming into the spotlight to be used for a wall-hanging display device.  
         [0007]     In fabricating the PDP, printing or other photography processes are generally used in coating phosphor or electrodes. Yet, these processes are expensive as well as put limitation on resolution.  
         [0008]     In order to overcome such limitation, to reduce costs, and to enhance high precision, some manufacturers intend to use ink jet printing. A device for driving an ink jet printer for display device fabrication according to a related art, as shown in  FIG. 1 , is explained as follows.  
         [0009]      FIG. 1  is a configurational block diagram of a device for driving an ink jet printer for display device fabrication according to a related art. Referring to  FIG. 1 , a device for driving an ink jet printer for display device fabrication according to a related art consists of a DC/DC converter  40  outputting a prescribed drive voltage V h , a timing controller  10  outputting a timing control signal by receiving a prescribed signal IN inputted from outside, a head driver  20  outputting a drive pulse by receiving the timing control signal outputted from the timing controller  10  and the prescribed drive voltage V h , and an array resistor  30  receiving the drive pulse outputted from the head driver  20  to output a signal (head drive voltage) having a voltage at a prescribed level to a head.  
         [0010]     An operation of the above-configured device for driving the ink jet printer for display device fabrication according to a related art is explained as follows.  
         [0011]      FIG. 2  is a diagram for explaining an operation mode and standby mode for the device for driving the ink jet printer for display device fabrication according to the related art.  
         [0012]     Referring to  FIG. 2 , once the prescribed signal IN for driving the head is inputted from outside, the timing controller  10  receives the signal IN to output the timing control signal having a prescribed frequency.  
         [0013]     The head driver  20  receives the timing control signal outputted from the timing controller  10  and the prescribed drive voltage V h  outputted from the DC/DC converter  40  and then outputs the drive pulse having the level of the drive voltage V h . In doing so, the frequency of the drive pulse is equal to that of the timing control signal. For instance, if the drive voltage V h  is 40V and if the frequency of the timing control signal is 3 KHz, the head driver  20 , as shown in (a) of  FIG. 2 , outputs the drive pulse of 2 KHz at 40V.  
         [0014]     Thus, the drive pulse outputted from the head driver  20  is inputted to the array resistor  30 . The drive pulse is then converted according to a resistance of the array resistor  30  and a condenser value of the head connected to the array resistor  30  to be inputted to each head. In doing so, a frequency and voltage of the head drive voltage applied to the head are also equal to those of the drive pulse, respectively.  
         [0015]     Once the head drive voltage is applied to the head, ink is jetted from a nozzle, which is a sort of hole for jetting the ink, constructing the head to print a pattern of phosphor, electrode, or the like.  
         [0016]     On the other hand, if the ink jet printer fails to operate or is in standby mode, i.e., if the external input signal IN fails to be inputted, any kind of voltage, as shown in (b) of  FIG. 2 , is not applied to the head since there exists no drive pulse signal outputted from the head driver  20 .  
         [0017]     When the head drive voltage fails to be applied to the head, the ink fails to circulate to precipitate so that the nozzle may be blocked or a state of the nozzle can be changed. In case that the nozzle is blocked in the course of jetting the ink, a missing channel may be brought about.  
         [0018]     In order to solve the above-mentioned problems, the related art method of driving the ink jet printer intends to prevent the blocked nozzle and the missing channel in a manner of applying a priming pulse having a frequency different from that of the drive pulse in the standby mode, i.e., a pulse enabling to circulate the ink instead of jetting the ink. Yet, in the related art method, since the frequency of the drive pulse on printing is different from the frequency of the priming pulse after the printing, the condition for circulating the ink is varied to affect the ink jet. Hence, the ink blocking or missing channel may take place.  
         [0019]     Moreover, the DC/DC converter  40  of the related art device for driving the ink jet printer for display device fabrication keeps outputting the prescribed drive voltage V h  regardless of a presence or non-presence of the connection to the head. Hence, if the head is not connected, a bad influence may be put on the system.  
         [0020]     Meanwhile, even if the same drive voltage is applied to the head driver  20 , there exists a difference of voltage substantially applied to the head due to the resistance difference according to the characteristics or use of each head.  
         [0021]     Thus, once the difference of the voltage applied to each head takes place, the voltage difference varies a jetting speed of the ink jetted from the head to differentiate an ink jet amount according to each head. Hence, brightness reduction of the panel and the difference in uniformity take place after pattern printing, which is shown in  FIG. 3 .  
         [0022]      FIG. 3  is a diagram of a pattern according to a signal applied to each head of the related art device for driving the ink jet printer for display device fabrication.  
         [0023]     Referring to  FIG. 3 , in applying the same drive voltage V h  to the head driver, if the voltages applied to head- 1 , head- 2 , and head- 3  are 40V, 45V, and 35V, respectively due to the resistance difference between the respective heads, a pattern by the head- 2  is thickest and a pattern by the head- 3  is thin. Hence, the uniformity difference occurs.  
         [0024]     Meanwhile, as mentioned in the above explanation, even if the same drive voltage is applied to the head driver  20 , the ink amount jetted from the nozzle may vary due to the different features of a plurality of piezos configuring the respective heads, respectively instead of the difference between the voltages substantially applied to the heads, respectively.  
         [0025]      FIG. 4  is a diagram of a waveform applied to a piezo configuring each head of the related art device for driving the ink jet printer for display device fabrication. Referring to  FIG. 4 , in case that there are thirty-two piezos configuring a head, slopes of drive waveforms or voltages applied to the channels (piezos) differ from each other, whereby an amount of ink jetted from a nozzle varies.  
         [0026]     In case that the ink jet amount varies, the missing channel occurs to degrade the pattern uniformity.  
       SUMMARY OF THE INVENTION  
       [0027]     Accordingly, an object of the present invention is to solve at least the problems and disadvantages of the background art.  
         [0028]     An object of the present invention is to provide an apparatus for driving an ink jet printer for manufacturing a display device, by which pattern uniformity can be enhanced by controlling an output of a head drive voltage according to a presence or non-presence of head connection and by controlling a head drive voltage level according to a resistance value of a connected head.  
         [0029]     Another object of the present invention is to provide an apparatus for driving an ink jet printer for manufacturing a display device, by which pattern uniformity can be enhanced by preventing a missing channel in a manner of compensating a difference of voltage applied to a corresponding piezo configuring a head.  
         [0030]     Another object of the present invention is to provide an apparatus for driving an ink jet printer for manufacturing a display device and method thereof, by which sustainability and reliance of a head can be enhanced by preventing an ink blocking or a missing channel in a manner of adjusting a frequency of a pulse applied in an operation or standby mode of the ink jet printer for the display device fabrication.  
         [0031]     According to a first embodiment of the present invention, an apparatus of driving an ink jet printer for manufacturing a display device includes a timing control unit outputting a timing control signal by receiving a prescribed signal (IN) inputted from outside, a head drive unit receiving the timing control signal outputted from the timing control unit and a prescribed drive voltage (Vh), the head drive unit outputting a drive pulse of a predetermined voltage level, and an array resistor outputting a head drive voltage to a plurality of heads by receiving the drive pulse outputted from the head drive unit, wherein the head drive voltage outputted from the array resistor maintains a predefined voltage value.  
         [0032]     According to a second embodiment of the present invention, an apparatus of driving an ink jet printer for manufacturing a display device includes a head drive unit driving at least one head by receiving a prescribed drive voltage to output a drive pulse via an array resistor, a time delay unit receiving a prescribed trigger signal for head driving and outputting a timing control signal delayed by a prescribed time, and a push/pull drive unit outputting a priming pulse via the array resistor to the head by the timing control signal outputted from the time delay unit, wherein the priming pulse having a same frequency of the head drive pulse circulates ink instead of jetting the ink.  
         [0033]     According to a second embodiment of the present invention, a method of driving an ink jet printer for manufacturing a display device includes the steps of applying a drive pulse having a prescribed frequency and a drive voltage for printing ink to a head and applying a priming pulse having the prescribed frequency of the drive pulse and a prescribed priming voltage to the head after completion of applying the drive pulse.  
         [0034]     In an apparatus and a method of driving an ink jet printer for manufacturing a display device according to the present invention, the uniformity can be enhanced by compensating the voltage difference between the heads in a manner of controlling the output of the head drive voltage according to a presence or non-presence of head connection and controlling the head drive voltage level according to the resistance difference of the connected head. And, the pattern uniformity can be enhanced by preventing the missing channel occurrence in a manner of applying the same drive waveform to the piezos regardless of the features of the respective piezos. Moreover, the sustainability and reliance of the head can be enhanced by preventing the ink blocking or missing channel in a manner of equalizing the frequency of the drive pulse applied in printing the ink to that of the printing pulse applied in the standby mode and consecutively applying the drive and priming pulses of the same frequency to equalize the ink circulation condition. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0035]     The invention will be described in detail with reference to the following drawings in which like numerals refer to like elements.  
         [0036]      FIG. 1  is a configurational block diagram of a device for driving an ink jet printer for display device fabrication according to a related art.  
         [0037]      FIG. 2  is a diagram for explaining an operation mode and standby mode for a device for driving an ink jet printer for display device fabrication according to a related art.  
         [0038]      FIG. 3  is a diagram of a pattern according to a signal applied to each head of the related art device for driving the ink jet printer for display device fabrication.  
         [0039]      FIG. 4  is a diagram of a waveform applied to a piezo configuring each head of the related art device for driving the ink jet printer for display device fabrication.  
         [0040]      FIG. 5  is a block diagram of an apparatus for driving an ink jet printer for manufacturing a display device according to a first embodiment of the present invention.  
         [0041]      FIG. 6  is a diagram of a pattern according to a signal applied to each head of an apparatus for driving an ink jet printer for manufacturing a display device according to a first embodiment of the present invention.  
         [0042]      FIG. 7  is a block diagram of another apparatus for driving an ink jet printer for manufacturing a display device according to a first embodiment of the present invention.  
         [0043]      FIG. 8  is a detailed diagram of a drive pulse applying unit shown in  FIG. 7 .  
         [0044]      FIG. 9  is a diagram of a drive waveform applied to each channel of an apparatus for driving an ink jet printer for manufacturing a display device according to a first embodiment of the present invention.  
         [0045]      FIG. 10  is a block diagram of an apparatus for driving an ink jet printer for manufacturing a display device according to a second embodiment of the present invention.  
         [0046]      FIG. 11  is a detailed block diagram of a push/pull drive unit shown in  FIG. 10 .  
         [0047]      FIG. 12  is a diagram for explaining a method of driving an ink jet printer for manufacturing a display device according to a second embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0048]     Preferred embodiments of the present invention will be described in a more detailed manner with reference to the drawings.  
         [0000]     &lt;First Embodiment&gt; 
         [0049]     According to a first embodiment of the present invention, an apparatus of driving an ink jet printer for manufacturing a display device includes a timing control unit outputting a timing control signal by receiving a prescribed signal (IN) inputted from outside, a head drive unit receiving the timing control signal outputted from the timing control unit and a prescribed drive voltage (Vh), the head drive unit outputting a drive pulse of a predetermined voltage level, and an array resistor outputting a head drive voltage to a plurality of heads by receiving the drive pulse outputted from the head drive unit, wherein the head drive voltage outputted from the array resistor maintains a predefined voltage value.  
         [0050]     The prescribed drive voltage (Vh) is supplied from a DC/DC converting unit and an output voltage control unit so that the head drive voltage outputted from the array resistor can be maintained at the predefined voltage value by the head drive unit.  
         [0051]     The DC/DC converting unit outputs the prescribed drive voltage to the head drive unit by receiving a switching control signal and a voltage level control signal. The output voltage control unit outputs a switching-on/off control signal according to a presence or non-presence of a connected state of the head to the DC/DC converting unit by receiving the prescribed drive voltage outputted from the DC/DC converting unit. And, the output voltage control unit outputs the voltage level control signal to the DC/DC converting unit to enable the head drive unit to output the head drive voltage in case of the presence of the connected state of the head.  
         [0052]     The output voltage control unit includes a head detecting unit turning on/off a connection to the head by detecting the presence or non-presence of the connected state of the head, first and second resistors distributing the drive voltage (Vh) outputted from the DC/DC converting unit, a switching control unit outputting the switching-on/off control signal to the DC/DC converting unit by receiving a voltage caught on the second resistor and a predefined second reference voltage (Vref 2 ), and a voltage level control unit outputting the prescribed voltage level control signal to the DC/DC converting unit by receiving the voltage caught on the second resistor and a predefined first reference voltage (Vref 1 ) to enable the head drive unit to output the predefined head drive voltage.  
         [0053]     In case that the connection to the head is turned on, a resistor of the connected head and the second resistor are connected parallel.  
         [0054]     The head drive voltage outputted from the array resistor is generated from the head drive unit to be applied to each of a plurality of piezos included in the head.  
         [0055]     The head drive unit includes a plurality of drive pulse applying units and each of the drive pulse applying units generates a prescribed constant current by detecting a pulse of the drive voltage inputted to a piezo and applies the prescribed drive voltage (V h ) and a drive pulse having the prescribed constant current to the piezo via a resistor by the received timing control signal.  
         [0056]     The drive pulse applying unit includes a voltage detecting unit outputting a prescribed voltage by detecting the pulse of the head drive voltage applied to the piezo, a piezo current control unit comparing the prescribed voltage outputted from the voltage detecting unit to a predefined reference voltage (Vref) and outputting the constant current corresponding to a difference resulting from the comparison and the drive voltage (V h ) inputted from outside, and a piezo drive unit receiving the drive voltage (V h ) and the prescribed constant current outputted from the piezo current control unit and applying the drive pulse having the drive voltage (V h ) and the prescribed constant current to the piezo via the resistor by the timing control signal inputted from outside.  
         [0057]     The piezo current control unit includes a constant current control unit outputting a prescribed constant current control signal by comparing the prescribed voltage outputted from the voltage detecting unit to the predefined reference voltage (Vref) and a constant current unit outputting the prescribed constant current generated from the prescribed drive voltage (V h ) inputted from outside and the constant current control signal inputted from the constant current control unit to the piezo drive unit.  
         [0058]     And, the piezo drive unit includes a plurality of switching means for outputting the drive voltage V h ) and the prescribed constant current outputted from the constant current unit via the resistor to the piezo by being controlled by the timing control signal inputted from outside.  
         [0059]     Hereinafter, a first embodiment of the present invention will be described with reference to the drawings.  
         [0060]      FIG. 5  is a block diagram of an apparatus for driving an ink jet printer for manufacturing a display device according to a first embodiment of the present invention.  
         [0061]     Referring to  FIG. 5 , an apparatus for driving an ink jet printer for manufacturing a display device according to a first embodiment of the present invention includes a DC/DC converting unit  500  outputting a prescribed drive voltage V h  by receiving a switching control signal and a prescribed voltage level control signal, a timing control unit  100  outputting a timing control signal by receiving a prescribed signal IN inputted from outside, a head drive unit  200  receiving the timing control signal outputted from the timing control unit  100  and the prescribed drive voltage V h  outputted from the DC/DC converting unit  600  to output a drive pulse at a level of the received voltage, an array resistor  300  receiving the drive pulse outputted from the head drive unit  200  to output a signal (head drive voltage) having a voltage at a prescribed level to a head, and an output voltage control unit  700  controlling to turn on/off the output voltage V h  of the DC/DC converting unit  600  according to a presence or non-presence of a connection to a head and controlling an output voltage level of the DC/DC converting unit  600  to enable to output a predefined head drive voltage (e.g., 40V) according to a resistance of a resistor R h  of a connected head.  
         [0062]     The output voltage control unit  700  includes a head detecting unit  730  turning on/off the connection to the head by detecting the presence or non-presence of the connection to the head, first and second resistors R 1  and R 2  distributing the voltage V h  outputted from the DC/DC converting unit  600 , a switching control unit  720  outputting a switching-on/off control signal to the DC/DC converting unit  600  by receiving a voltage at the second resistor R 2  and a second reference voltage V ref2 , and a voltage level control unit outputting a prescribed voltage level control signal to the DC/DC converting unit  600  by receiving the voltage at the second resistor R 2  and a first reference voltage V ref1  to enable the head drive unit  200  to output the predefined head drive voltage.  
         [0063]     In this case, the voltage at the second resistor R 2  varies according to the presence or non-presence of the connection to the head. Once the head is connected, the head resistor R h  and the second resistor R 2  are connected parallel. Hence, the voltage at the second resistor R 2  in case of the presence of the connection to the head is much smaller than that in case of the non-presence of the connection to the head. And, the switching control unit  720  and the voltage level control unit  710  control the DC/DC converting unit  600  using the voltage at the second resistor R 2 .  
         [0064]     The switching control unit  720  can be configured using a differential amplifier and the voltage level control unit  710  can be configured using an error amplifier.  
         [0065]     Preferably, the head detecting unit  730  includes a switching means (not shown in the drawing) for enabling a connection to the second resistor R 2  by detecting the presence or non-presence of the connection to the head. Preferably, the DC/DC converting unit  600  includes a switching means (not shown in the drawing) for deciding an output of the prescribed voltage V h  by being turned on/off according to the switching control signal outputted from the switching control unit  720 .  
         [0066]     An operation of an apparatus for driving an ink jet printer for manufacturing a display device according to the first embodiment of the present invention is explained as follows.  
         [0067]     First of all, once a prescribed signal IN for driving a printer is inputted from outside, the timing control unit  100  receives the external input signal and then outputs the timing control signal for driving a head.  
         [0068]     The head drive unit  200  receives the timing control signal outputted from the timing control unit  100  and the prescribed drive voltage V h  outputted from the DC/DC converting unit  600  and then outputs the drive pulse having the level of the received voltage Vh.  
         [0069]     The drive pulse outputted from the head drive unit  200  is inputted to the array resistor  300  so that the head drive voltage having the prescribed converted voltage is inputted to the head.  
         [0070]     From now on, the following assumptions are made to explain the present invention. In case that the head is connected, it is assumed that the voltage caught on the second resistor R 2  is Von. In case that the head is not connected, it is assumed that the voltage caught on the second resistor R 2  is Voff. In this case, the voltage Von is variable since the value of the head resistor R h  varies according to the use and characteristic of the head.  
         [0071]     First of all, in case that the head exists, the head detecting unit  730  detects that the head is connected via the resistance of the head resistor R h  and then connects the second resistor R 2  to the head in parallel. Namely, the second resistor R 2  and the head resistor R h  are connected parallel to each other.  
         [0072]     The switching control unit  720  receives the second reference voltage V ref2  and the voltage Von caught on the second resistor R 2  according to the parallel connection between the second resistor R 2  and the head resistor R h , i.e., the voltage Von resulted from the voltage V h  that is outputted from the DC/DC converting unit  600  to be applied between the second resistor R 2  and head resistor R h  connected parallel to each other, and then outputs the switching-on control signal to the switching means provided to the DC/DC converting unit  600 .  
         [0073]     The voltage level control unit  710  receives the first reference voltage V ref1  and the voltage V h  caught on the second resistor R 2  and then the prescribed voltage level control signal corresponding to a difference between the two voltages to the DC/DC converting unit  600 .  
         [0074]     The DC/DC converting unit  600  receives the switching-on control signal outputted from the switching control unit  720  and the voltage level control signal outputted from the voltage level control unit  710  and then outputs the prescribed voltage V h  corresponding to the voltage level control signal to the head drive unit  200 .  
         [0075]     Meanwhile, explained in the following are one case of the head drive voltage higher than the predefined head drive voltage (e.g., 40V) and the other case of the head drive voltage lower than the predefined head drive voltage (e.g., 40V).  
         [0076]     For instance, assuming that the predefined head drive voltage is 40V, the cases of the head- 2  (in case of the head drive voltage higher than the predefined head drive voltage) and the head- 3  (in case of the head drive voltage lower than the predefined head drive voltage) shown in  FIG. 3  are explained as follows.  
         [0077]     In case of the head- 2 , since the head drive voltage is 45V that is higher than the predefined head drive voltage 40V, a voltage drop of 5V is necessary. Namely, the voltage level control unit  710  receives the first reference voltage and the voltage driven by the parallel connection between the resistor of the head- 2  and the second resistor R 2  and then outputs the voltage level control signal for the voltage drop of 5V to the DC/DC converting unit  600 . The DC/DC converting unit  600  receives the voltage level control signal for dropping the voltage by 5V and then outputs the corresponding prescribed voltage V h , whereby the head drive voltage applied to the head- 2  is lowered. By repetition of such a process, the impression of the head drive voltage applied to the head- 2  can be achieved by the predefined head drive voltage of 40V.  
         [0078]     On the other hand, in case of the head- 3 , since the head drive voltage is 35V that is lower than the predefined head drive voltage 40V, a voltage rise of 5V is necessary. Namely, the voltage level control unit  710  receives the first reference voltage and the voltage driven by the parallel connection between the resistor of the head- 3  and the second resistor R 2  and then outputs the voltage level control signal for the voltage rise of 5V to the DC/DC converting unit  600 . The DC/DC converting unit  600  receives the voltage level control signal for raising the voltage by 5V and then outputs the corresponding prescribed voltage V h , whereby the head drive voltage applied to the head- 3  is raised. By repetition of such a process, the impression of the head drive voltage applied to the head- 3  can be achieved by the predefined head drive voltage of 40V.  
         [0079]     Thus, by raising or lowering to compensate the head drive voltage applied to the head- 1 , head- 2 , or head- 3  to fit the predefined head drive voltage, the compensated head drive voltage coincides with the predefined head drive voltage of 40V to cancel out the voltage difference between the heads. Hence, the patterns by the respective heads become uniform.  
         [0080]     Meanwhile, if the head is not connected, the voltage Voff caught on the second resistor R 2  is raised. The switching control unit  720  receives the voltage Voff and the second reference voltage to output the switching-off control signal to the DC/DC converting unit  600 .  
         [0081]     The DC/DC converting unit  600  receives the switching-off control signal to turn of the prescribed voltage V h  applied to the head drive unit  200 . Namely, as the voltage is not applied to the head drive unit  200  unlike the related art derive device, the present invention enables to remove the bad influence put on the system.  
         [0082]     Even if the prescribed voltage level control signal is outputted by the first reference voltage and the voltage Voff from the voltage level control unit  710  to the DC/DC converting unit  600 , any influence is not put on the system since the switching means provided to the DC/DC converting unit  600  is turned off.  
         [0083]     Besides, in the above-described apparatus of driving an ink jet printer for manufacturing a display device according to the first embodiment of the present invention, the head resistor R h  may have the resistance value of the head itself or an average resistance of a plurality of piezos configuring a head that will be explained in another apparatus for driving an ink jet printer for manufacturing a display device according to the first embodiment of the present invention. Moreover, the predefined first and second reference voltages can be determined by a manufacturer of the corresponding display device.  
         [0084]     Therefore, the apparatus of driving an ink jet printer for manufacturing a display device according to the first embodiment of the present invention enhances the uniformity of the pattern by equalizing the head drive voltage applied to the head even if the resistance differs according to the use and characteristic of the head.  
         [0085]      FIG. 7  is a block diagram of another apparatus for driving an ink jet printer for manufacturing a display device according to a first embodiment of the present invention.  
         [0086]     Referring to  FIG. 7 , another apparatus for driving an ink jet printer for manufacturing a display device according to a first embodiment of the present invention includes a timing control unit  100  receiving an external signal IN, e.g., trigger signal, for driving a head and outputting a prescribed timing control signal and a head drive unit  200  provided with a plurality of drive pulse applying units  210 . And, each of the drive pulse applying units  210  generates a prescribed constant current by detecting a voltage of a drive waveform inputted to a piezo and applies a drive voltage V h  inputted from outside and a drive pulse having the prescribed constant current to the piezo via resistor  310  by the timing control signal outputted from the timing control unit  100 .  
         [0087]     The drive pulse applying unit  210  includes a voltage detecting unit  212  outputting a prescribed voltage by detecting the voltage of the drive waveform applied to the piezo, a piezo current control unit  211  comparing the prescribed voltage outputted from the voltage detecting unit  212  to a predefined reference voltage V ref  and outputting the constant current corresponding to a difference resulting from the comparison and the drive voltage V h  inputted from outside, and a piezo drive unit  213  receiving the drive voltage V h  and prescribed constant current outputted from the piezo current control unit  211  and applying the drive pulse having the drive voltage V h  and the prescribed constant current to the piezo via the resistor  310  by the timing control signal outputted from the timing control unit  100 .  
         [0088]     In this case, the voltage detecting unit  212  integrates the drive waveform applied to the piezo, e.g., piezo- 1 , to convert to a constant DC voltage and then detects an inputted voltage using the converted voltage.  
         [0089]      FIG. 8  is a detailed diagram of the drive pulse applying unit  210  shown in  FIG. 7 . Referring to  FIG. 8 , the piezo current control unit  211  includes a constant current control unit  211   c  outputting a prescribed constant current control signal by comparing the prescribed voltage outputted from the voltage detecting unit  212  to the predetermined reference voltage V ref  and a constant current unit  211   b  outputting the prescribed constant current by the drive voltage V h  inputted via current restricting resistor  211   a  and the constant current control signal inputted from the constant current control unit  211   c . And, the piezo drive unit  213  includes a plurality of switching means SW 1  and SW 2  for outputting the drive voltage V h  and prescribed constant current outputted from the constant current unit  211   b  via the resistor  310  to the piezo.  
         [0090]     An operation of another apparatus for driving an ink jet printer for manufacturing a display device according to the first embodiment of the present invention is explained with reference to  FIG. 8  as follows.  
         [0091]     First of all, once the trigger signal IN for jetting ink is inputted from outside, the timing control unit  100  outputs the prescribed timing control signal. And, the switching means SW 1  and SW 2  provided to the piezo drive unit  213  are turned on/off by the timing control signal so that the drive pulse having the drive voltage V h  and prescribed constant current inputted from the constant current unit  211   b  to the piezo (piezo- 1 ) via the resistor  310 .  
         [0092]     The voltage detecting unit  212  outputs the prescribed voltage by detecting the DC voltage resulting from integrating to convert the drive waveform inputted to the piezo. And, the constant current control unit  211   c  outputs the prescribed constant current control signal by comparing the prescribed voltage outputted from the voltage detecting unit  212  to the predefined reference voltage V ref .  
         [0093]     The constant current unit  211   b  outputs the prescribed constant current generated by the drive voltage V h  inputted via the current restricting resistor  211   a  and the constant current control signal outputted from the constant current control unit  211   c . And, the switching means SW 1  and SW 2  provided to the piezo drive unit  213  are turned on/off by the timing control signal outputted from the timing control unit  100  to apply the drive pulse having the drive voltage V h  and prescribed constant current inputted from the constant current unit  211   b  to the piezo via the resistor  310 . By repeating such an operational process, the drive waveform having the same voltage and slope is applied to each of the piezos, whereby the drive waveform having the same voltage (e.g., V h ) and slope can be applied to each channel.  
         [0094]     The slope of the drive waveform applied to the piezo depends on a size of the constant current outputted from the constant current unit  21   b.  For instance, if a voltage size of the drive waveform detected by the voltage detecting unit  212  is small, i.e., if the voltage size of the drive waveform applied to the piezo is small, the constant current outputted from the constant current unit  211   b  is increased to raise the voltage of the drive waveform applied to the piezo.  
         [0095]     Therefore, in the apparatus of driving an ink jet printer for manufacturing a display device according to the first embodiment of the present invention, the voltage of the waveform applied to each of the piezos is detected and the size of the constant current is controlled to enable to apply the waveform having the same voltage and slope to each of the piezos via the detected voltage. Namely, in case of the piezo smaller than the voltage of the predefined drive waveform, the size of the applied constant current is increased. And, in case of the piezo greater than the voltage of the predefined drive waveform, the size of the applied constant current is decreased. Hence, the waveform having the same voltage and slope is applied to each of the piezos.  
         [0096]     Moreover, although not shown in the drawing, in the apparatus of driving an ink jet printer for manufacturing a display device according to the first embodiment of the present invention, a variable resistor is inserted in each channel and the inserted variable resistor is independently controlled. Therefore, it is able to apply the same drive waveform to each of the piezos.  
         [0000]     &lt;Second Embodiment&gt; 
         [0097]     According to a second embodiment of the present invention, an apparatus for driving an ink jet printer for manufacturing a display device includes a head drive unit driving at least one head by receiving a prescribed drive voltage to output a drive pulse via an array resistor, a time delay unit receiving a prescribed trigger signal for head driving and outputting a timing control signal delayed by a prescribed time, and a push/pull drive unit outputting a priming pulse via the array resistor to the head by the timing control signal outputted from the time delay unit, wherein the priming pulse having a same frequency of the head drive pulse circulates ink instead of jetting the ink.  
         [0098]     The push/pull drive unit includes a buffer and inverter outputting switching-on/off signals by the timing control signal outputted from the time delay unit, respectively, a first switch controlled by the switching-on/off signal outputted from the buffer and outputting a priming voltage to the array resistor by the switching-on signal, and a second switch controlled by the switching-on/off signal outputted from the inverter and outputting a ground voltage (GND) to the array resistor by the switching-on signal.  
         [0099]     According to a second embodiment of the present invention, a method of driving an ink jet printer for manufacturing a display device includes the steps of applying a drive pulse having a prescribed frequency and a drive voltage for printing ink to a head and applying a priming pulse having the prescribed frequency of the drive pulse and a prescribed priming voltage to the head after completion of applying the drive pulse.  
         [0100]     And, a width of the priming pulse is smaller than that of the drive pulse.  
         [0101]     Hereinafter, a second embodiment of the present invention will be described with reference to the drawings.  
         [0102]      FIG. 10  is a block diagram of an apparatus for driving an ink jet printer for manufacturing a display device according to a second embodiment of the present invention.  
         [0103]     Referring to  FIG. 10 , an apparatus for driving an ink jet printer for manufacturing a display device according to a second embodiment of the present invention includes a timing control unit  100  receiving an external signal IN, e.g., trigger signal, for head driving and outputting a timing control signal having a prescribed frequency, a head drive unit  200  receiving the timing control signal outputted from the timing control unit  100  and a prescribed drive voltage V h , e.g., 40V, from outside and outputting a drive pulse via array resistor  300 , a time delay unit  400  receiving the external signal IN and outputting a prescribed time delayed timing signal having the same frequency of the timing control signal outputted from the timing control unit  100 , and a push/pull drive unit  500  receiving the delayed timing control signal outputted from the time delay unit  400  and a prescribed priming voltage, V p , e.g., 20V, from outside and outputting a priming pulse via the array resistor  300  to a head.  
         [0104]     In this case, a width of the priming pulse applied to the array resistor  300  from the push/pull drive unit  500  can be equal to or smaller than that of the drive pulse applied to the array resistor  300  from the head drive unit  200 .  
         [0105]      FIG. 11  is a detailed block diagram of the push/pull drive unit  500  shown in  FIG. 10 .  
         [0106]     Referring to  FIG. 11 , the push/pull drive unit  500  includes a buffer  510  and inverter  520  outputting switching-on/off signals by the timing control signal outputted from the time delay unit  400 , respectively, a first switch SW 1  controlled by the switching-on/off signal outputted from the buffer  510  and outputting a priming voltage to the array resistor  300  by the switching-on signal, and a second switch SW 2  controlled by the switching-on/off signal outputted from the inverter  520  and outputting a ground voltage GND to the array resistor  300  by the switching-on signal.  
         [0107]     An operation of a method of driving an ink jet printer for manufacturing a display device according to the second embodiment of the present invention is explained as follows.  
         [0108]     First of all, once the trigger signal IN for jetting ink is inputted from outside, the timing control unit  100  outputs the prescribed timing control signal having the prescribed frequency, e.g., 3 KHz. The head drive unit  200  receives the timing control signal outputted from the timing control unit  100  and the prescribed drive voltage inputted from outside, e.g., the prescribed drive voltage V h  outputted from the DC/DC converting unit, and then outputs the drive pulse, as shown in  FIG. 12 , having the prescribed drive voltage V h .  
         [0109]     The drive pulse outputted from the head drive unit  200  is passed through the array resistor  300  to be converted to a prescribed signal by a resistance of the array resistor  300  and a condenser value existing in the head. And, the head is then driven by the converted signal to jet the ink.  
         [0110]     In doing so, after the drive pulse having the drive voltage Vh has been applied to the head, the ink is not injected. Instead, the priming pulse, which has the same frequency of the drive pulse but is delayed by the prescribed time, is applied thereto to circulate the ink instead of jetting the ink under the same condition.  
         [0111]     A process of applying the priming pulse is explained in detail as follows.  
         [0112]     First of all, First of all, once the trigger signal IN for jetting ink is inputted from outside, the time delay unit  400  outputs the timing control signal, which has the same frequency, e.g., 3 KHz, of the timing control signal outputted from the timing control unit  100  but is delayed by a prescribed time. In this case, the prescribed delayed time can be determined by a printer manufacturer to depend on circumstances.  
         [0113]     The buffer  510  and inverter  520  having received the timing control signal outputted from the time delay unit  400  output the switching-on or switching-off signal. The first and second switches SW 1  and SW 2  receive the switching-on or switching-off signal outputted from the buffer  510  and inverter  520  to output the priming voltage V p  and the ground voltage GND, respectively. For instance, if the buffer  510  and the inverter  520  output the switching-on signal and the off-off signal during a prescribed time (e.g., 5 μsec), respectively, the first switch SW 1  is turned on but the second switch SW 2  is turned off. Hence, the priming voltage V p  is outputted to the array resistor  300 . On the other hand, if the buffer  510  and the inverter  520  output the switching-off signal and the switching-on signal during a prescribed time (e.g., 5 μsec), respectively, the first switch SW 1  is turned off but the second switch SW 2  is turned on. Hence, the ground voltage GND is outputted to the array resistor  300 .  
         [0114]     Through the above-explained process, the priming pulse, which is delayed by the prescribed time to be later than the drive pulse, is outputted to the array resistor  300 . And, the outputted priming pulse is passed through the array resistor  300  to be converted to the prescribed signal by the resistance of the array resistor  300  and the condenser value existing in the head.  
         [0115]      FIG. 12  is a diagram of the drive and priming pulses outputted to the array resistor  300  and the head via the above-explained process. Referring to  FIG. 12 , the frequency of the drive pulse is equal to that of the priming pulse. Yet, the pulse width and voltage of the drive pulse are different from those of the priming pulse. If the priming pulse having the same frequency of the drive pulse is applied to the head, the ink fails to be jetted but keeps circulating. Hence, it is able to prevent the nozzle from being blocked or the missing channel from occurring.  
         [0116]     Accordingly, in the apparatus of driving an ink jet printer for manufacturing a display device and method thereof according to the second embodiment of the present invention, the frequency of the drive pulse outputted from the head drive unit is equal to that of the priming pulse outputted from the push/pull drive unit. Yet, the drive pulse differs from the priming pulse in voltage. And, the voltages and frequencies of the drive and priming pulses are variable according to circumstances.  
         [0117]     Moreover, in the apparatus of driving an ink jet printer for manufacturing a display device and method thereof according to the second embodiment of the present invention, the push/pull drive unit applying the priming pulse to the array resistor includes the switches, thereby simplifying its configuration and barely needing any power consumption.  
         [0118]     The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.