Patent Publication Number: US-7910174-B2

Title: Apparatus and method of fabricating flat panel display device

Description:
RELATED APPLICATIONS 
     The present patent document is a divisional patent application of U.S. application Ser. No. 11/005,705, filed Dec. 7, 2004, now U.S. Pat. No. 7,488,388, which claims the benefit of Korean Patent Application No. P2003-90293 filed in Korea on Dec. 11, 2003, which is hereby incorporated by reference. 
    
    
     BACKGROUND 
     The present application relates to an apparatus and a method of fabricating a flat panel display device, to an apparatus and a method of fabricating a flat panel display device capable of detecting a broken line of a sealant in real time and of automatically repairing the detected broken line of the sealant. 
     DESCRIPTION OF THE RELATED ART 
     Recently, various types of flat panel display (FPD) devices have been developed that are smaller and lighter than cathode ray tube display devices. Such devices include a liquid crystal display (LCD) device, a field emission display (FED) device, a plasma display panel (PDP) and an electro-luminescence (EL) display device. 
     The FPD includes a flat panel in which cells are arranged in a matrix between two glasses, a printed circuit board module for driving the flat panel, and a case for protecting the flat panel and the printed circuit board module and integrating them. Since the LCD device is not a self-luminous device, the LCD device requires a separate light source such as a back light unit. Herein, the printed circuit board module receives red, green and blue image data, and a synchronizing signal from an exterior and then processes them to supply an image data, a scanning signal and a timing control signal to the flat panel. Such a printed circuit board module corresponds to a driving circuit making to normally display a computer image, a television image and the other available image on the flat panel. 
     A description of a LCD device will serves as an example of a FPD. The LCD device controls light transmittance of liquid crystal cells in accordance with video signals, thereby displaying pictures corresponding to the video signals on a liquid crystal display panel where liquid crystal cells are arranged in a matrix. To this end, the LCD device includes an active region where the liquid crystal cells are arranged in an active matrix, and a driving circuit for driving the liquid crystal cells of the active region. 
     Referring to  FIGS. 1 and 2 , a related art LCD device has a structure, in which an upper plate and a lower plate are faced to combine each other. The related art LCD device includes a picture display section  4  where liquid crystal cells are located, and a sealant  2  for combining the upper plate and the lower plate. 
     The picture display section  4  includes: the upper plate having a black matrix  20 , a color filter  16  and a common electrode  14 ; and a lower plate facing to and combined with the upper plate and having a thin film transistor and a pixel electrode  22 . Spacers  24  are formed between the upper plate and the lower plate. Also, a liquid crystal material  18  is injected into an inner space provided by the spacers  24  between the upper plate and the lower plate. 
     On the upper plate, the black matrix  20  is formed in a matrix on an upper substrate  11 . The black matrix  20  serves to partition a surface of the upper substrate  11  into a plurality of cell regions at which the color filters  16  will be formed, and to prevent the interference of light between adjacent cells. Color filters  16  of the primary three colors, i.e., red, green and blue are sequentially formed on the upper substrate  11  where the black matrix  20  is formed. In this case, a material absorbing white light and transmitting only particular light with a specific wavelength, i.e., red, green or blue, is applied on an entire surface of the upper substrate  11  having the black matrix  20 . Thereafter, the material is patterned, to thereby form each of the three color filters  16  of the primary three colors. A common electrode  14 , a transparent conductive material having a ground electric potential supplied thereto, is formed on the upper substrate  11  where the black matrix  20  and the color filters  16  are formed. A polyamide is applied so as to cover the common electrode  14 , to thereby form an upper alignment film  12 . 
     The sealant  2  is formed at an outer line of the picture display section  4  in the upper plate to combine the upper plate and the lower plate. 
     In the lower plate, the TFT that switches the driving of the liquid crystal cell includes a gate electrode  25  extended from a gate line (not shown), a source electrode  28  extended from a data line (not shown), and a drain electrode  30  connected to a pixel electrode  22  through a contact hole  23 . Further, the TFT includes a gate insulating film  6  to separately insulate the gate electrode  25 , the source electrode  28  and the drain electrode  30 ; semiconductor layers  26  and  27  to form a conductive channel between the source electrode  28  and the drain electrode  30  by a gate voltage supplied to the gate electrode  25 . Such a TFT selectively supplies a data signal from the data line to the pixel electrode  22  in response to a gate signal from the gate line. 
     The pixel electrode  22  is located at a cell area defined by the crossing of the data line and the gate line and is formed of a transparent conductive material with high light transmittance. The pixel electrode  22  is formed on a passivation film  8  applied to the entire surface of a lower substrate  1 , and electrically connected to the drain electrode through the contact hole  23  formed in the passivation film  8 . 
     After applying a lower alignment film  10  to an upper portion of the lower substrate  1  where the pixel electrode  22  is formed, a rubbing process is performed. Thereafter, the spacers  4  for maintaining a gap between the upper plate and the lower plate are sprayed to complete the lower plate. 
     Lastly, the upper plate and the lower plate separately made as described above are put into a desired position to combine them together by use of the sealant  2 . Thereafter, the liquid crystal material is injected and is sealed, to thereby complete the LCD device. 
     As set forth above, the sealant  2 , for combining the upper plate and the lower plate in the related art LCD device, formed on the upper plate, is formed by a sealing apparatus as shown in  FIG. 3 . 
     The sealing apparatus includes: a driver  60  facing the upper substrate  11  and executing horizontal movement and vertical movement; a guide line  70  for guiding the horizontal movement of the driver  60 ; a dispenser  72 , installed at a lower end of the driver  60 , for applying the sealant on the upper substrate  11 ; a supplier  62  connected to the dispenser  72  to supply the sealant; and a controller  64  for controlling the horizontal movement and the vertical movement of the driver  60 . 
     The upper substrate  11  is reached by a loading device (not shown) on a stage  50 . As described above, the black matrix  20 , the color filter, and the common electrode of the picture display section  4  are formed on the upper substrate  11 . 
     The driver  60  executes the horizontal movement along the guide line  70 , in response to a control signal generated from the controller  64 , or executes the vertical movement to correspond to the upper substrate  11 . 
     The dispenser  72  applies the sealant  2  supplied from the supplier  62  to the upper substrate  11 . To this end, a jet nozzle  74  is installed at one side of the dispenser  72  in order to supply the sealant  2  supplied from the dispenser  72  to the outer line of the picture display section  4  in a defined thickness and a defined width. 
     According to the related art sealing apparatus, when the upper substrate  11  is loaded on the stage  50 , the driver  60  is lowered so as to have a designated gap between the jet nozzle  74  and the upper substrate  11  under a control of the controller  64 . And then, the driver  60  executes the horizontal movement along the guide line  70 . At this time, when the dispenser  72  is lowered so as to have the designated gap spaced from the upper substrate  11 , the dispenser  72  supplies the sealant  2  from the supplier  62  to the net nozzle  74  in a designated pressure. Accordingly, as the driver  60  executes the horizontal movement, the jet nozzle  74  applies the sealant  2  supplied from the dispenser  72  in the designate pressure to the outer line of the picture display section  4  in the upper substrate  11  so as to have the designated thickness and the designated width. 
     However, in the related art sealing apparatus, when sealant  2  is applied, a broken line  80  occurs in the sealant  2  as shown in  FIG. 3 , due to the gap between the jet nozzle  74  and the upper substrate  11 , a horizontal movement speed of the driver, the pressure exerted on the sealant  2  supplied from the dispenser  72  to the jet nozzle  74 , and/or sudden clogging of the jet nozzle  74 . Since the broken line  80  of the sealant  2  is inspected with the naked eye of a worker, the broken line  80  cannot be accurately detected. Meanwhile, if the broken line  80  of the sealant  2  is detected through the visible eyes of the worker, then the sealant  2  is applied again to the entire upper substrate  11 . Thus, the related art sealing apparatus has a problem that a production yield is deteriorated because working hours of a sealing process become increased. 
     BRIEF SUMMARY 
     An apparatus and a method of fabricating a flat panel display device capable of detecting a broken line of a sealant in real time and of automatically repairing the detected broken line of the sealant is provided. 
     By way of introduction only, an apparatus of fabricating a display device according to an embodiment includes: a substrate; a stage on which the substrate is loaded; a dispenser from which a sealant is applied to the substrate; a light detector that emits light toward the substrate and detects an amount of light reflected toward the detector in real-time; and a controller that detects a position on the substrate that is to be covered with sealant but does not have the sealant, in accordance with a signal supplied from the light detector, and controls the dispenser so as to apply the sealant to the substrate at the position. 
     In another embodiment, a method of fabricating a display device includes applying a sealant at a picture display section formed on a substrate; detecting a broken line in the sealant applied to the substrate in real-time; and applying the sealant to a portion of the broken line missing sealant. 
     In another embodiment, an apparatus comprises a stage of sufficient size to receive a substrate of a display device; a dispenser from which a sealant is dispensed toward the stage; a source that emits energy at an oblique angle toward the stage; a detector that detects the energy from the source that has been reflected toward the detector; and a controller that controls the dispenser such that the dispenser traces a path while dispensing, detects a missing position along the path that does not contain the sealant in accordance with a signal supplied from the light detector, and controls the dispenser such that the dispenser moves back to the missing position and applies the sealant to the missing position. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The following detailed description of the embodiments reference the accompanying drawings, in which: 
         FIG. 1  is a plan view illustrating a related art liquid crystal display device; 
         FIG. 2  is a sectional view illustrating the liquid crystal display device taken along line A-A′ in  FIG. 1 ; 
         FIG. 3  is a block diagram showing a related art sealing apparatus; 
         FIG. 4  is a front view illustrating an apparatus of fabricating a flat panel display device according to an embodiment of the present invention; 
         FIG. 5  is a side view illustrating an apparatus of fabricating the flat panel display device according to the embodiment of the present invention; 
         FIG. 6  is an enlarged view of an area Y shown in  FIG. 5 ; 
         FIG. 7A  is a configuration representing a real-time detection of a broken line in a sealant applied on a substrate by an apparatus and a method of fabricating the flat panel display device according to the embodiment of the present invention; and 
         FIG. 7B  is a configuration representing that the sealant is applied again to a broken line detected upon applying a first sealant as shown in  FIG. 7A . 
     
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS AND THE PRESENTLY PREFERRED EMBODIMENTS 
     Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawing. 
     Hereinafter, the preferred embodiments of the present invention will be described in detail with reference to  FIGS. 4 to 7B . 
     Referring to  FIG. 4 , a sealing apparatus of a flat panel display device according to an embodiment of the present invention includes: a stage  150  on which a substrate  111  having a picture display section is mounted; a driver  160  facing the substrate  111  and executing horizontal movement and vertical movement; a guide line  170  for guiding the horizontal movement of the driver  160 ; a supplier  162  for supplying a sealant  102  being applied to an outer line of the picture display section in the substrate  111 ; a dispenser  172 , installed at a lower end of the driver  160 , for applying the sealant supplied from the supplier  162  to the outer line of the picture display section in the substrate  111 , through a jet nozzle  174 ; a light sensor  190  installed at a lower end of the dispenser  172  with the jet nozzle  174  therebetween; a broken line detector  168  for detecting an electrical signal from the light sensor  190 ; and a controller  164  for controlling the horizontal movement and the vertical movement of the driver  160  and controlling the driver  160  in accordance with a detected signal from the broken line detector  168 . 
     The picture display section of the flat panel display device such as a liquid crystal display device, a field emission display device, a plasma display panel, an electro-luminescence display device and the like, is formed on the substrate  111 . Such a flat panel display device includes a flat panel in which cells are arranged in a matrix between two glass substrates combined by the sealant  102 , a printed circuit board module for driving the flat panel, and a case for protecting the flat panel and the printed circuit board module and integrating them. Accordingly, the substrate  111  may be either the upper substrate or the lower substrate. 
     The substrate  111  is loaded by a loading device (not shown) on the stage  150 . 
     The driver  160  executes the horizontal movement along the guide line  170 , in response to a control signal generated from the controller  164 , or executes the vertical movement to correspond to the substrate  111 . 
     The dispenser  172  applies the sealant  102  supplied from the supplier  162  to the jet nozzle  174  at a designated pressure. The jet nozzle  174  applies the sealant  102  supplied from the dispenser  172  at a designated pressure to the outer line of the picture display section by a designated thickness and a designated width. At this time, the jet nozzle  174  is spaced by a designated gap from the substrate  111  by the vertical movement of the driver  160 . 
     The light sensor  190 , as shown in  FIG. 5 , includes: a light-emitter  192  installed at one side in a lower end of the dispenser  172  and separated by a designated distance from the jet nozzle  174 ; and a light-receiver  194  installed at an opposite side to the one side in a lower end of the dispenser  172  and separated by a designated distance from the jet nozzle  174 . 
     The light-emitter  192 , as shown in  FIG. 5 , irradiates light  196  from a light source (not shown) in a designated slant. In other words, the light-emitter  192  irradiates the light  196  from the light source toward the sealant  102  applied to the substrate  111  through the jet nozzle  174 . 
     The light emitter  192  transmits the sealant and is reflected from the substrate  111 . The light-receiver  194  receives the reflected light  198  to convert the received light  198  into an electrical signal. 
     The broken line detector  168  receives the electrical signal from the light-receiver  194  of the light sensor  190  and detects the amount of the reflected light  198  from the substrate  111  that is incident on the light-receiver  194 . Accordingly, the broken line detector  168  detects a broken line  180  of the sealant  102  applied to the substrate  111  using the electrical signal from the light-receiver  194 . 
     In other words, the amount of the light  196  emitted from the light-emitter  192 , transmitted through the sealant  102  normally applied through the jet nozzle  174  and then impinges on the light-receiver  194  is different from the amount of the light  198  emitted from the light-emitter  192 , reflected from the substrate  111  exposed by the broken line  180  and then impinges on the light-receiver  194 . As a result, the broken line detector  168  determines a location in which the electrical signal supplied from the light sensor  190  is increased upon applying the sealant  102  (i.e., a location having an increased amount of the light  196  transmitting through the sealant) as a broken line  180  in the sealant  102 . And then, the broken line detector  168  generates a position information signal PIS corresponding to the broken line  180  to supply it to the controller  164 . 
     The controller  164  controls the driver  160  to descend so as to have a designated gap spaced between the jet nozzle  174  and the upper substrate  111  when the substrate  111  is loaded on the stage  150 . Also, the controller  164  controls the driver  160  to execute the horizontal movement along the guide line  170  at a designated speed. When the sealant  102  is completely applied on the substrate, the controller  164  controls the driver  160  so as to partially repair the broken line  180  in the sealant  102  in accordance with the position information signal PIS informing the existence the broken line  180  in the sealant  102  supplied from the broken line detector  168  when the sealant  102  have been applied. The broken line detector  160  may be incorporated in the controller  164  as a monolithic circuit. 
     According to the apparatus and the method of fabricating the flat panel display panel of the embodiment of the present invention, when the substrate  111  is loaded on the stage  150  as shown in  FIG. 7A , the driver  160  is lowered so as to have a designated gap spaced between the jet nozzle  174  and the substrate  111  under a control of the controller  164 . And then, the driver  160  executes the horizontal movement along the guide line  170 . At this time, when the dispenser  172  descends so as to be spaced from the substrate  111  by the designated gap, the dispenser  172  supplies the sealant  102  from the supplier  162  to the jet nozzle  174  at a designated pressure. Accordingly, as the driver  160  executes the horizontal movement, the jet nozzle  174  applies the sealant  102  supplied from the dispenser  172  at the designated pressure to the outer line of the picture display section  104  in the substrate  111  in order for the sealant  102  to have the designated thickness and the designated width. At this time, the controller  164  controls the driver  160  to make a path  200  of the jet nozzle  174  to be transferred along the outer line of the picture display section  104  from a left upper corner SP of the substrate  111 . 
     When the sealant  102  is applied, the light sensor  190  emits light toward the sealant  102  applied to the substrate  111  and detects the amount of light transmitted from the sealant  102  to supply the electrical signal representing the detected amount of light to the broken line detector  168 . Accordingly, the broken line detector  168  detects the broken line in the sealant  102  on a basis of the electrical signal supplied from the light sensor  190  in real-time, and generates the position information signals PISs, e.g., for broken lines  180   a ,  180   b  and  180   c  of the sealant  102  in real-time to supply them to the controller  164 . At this time, the broken lines  180   a ,  180   b  and  180   c  in the sealant  102  generated upon applying the sealant  102  occurs due to the gap between the jet nozzle  174  and the substrate  111 , a horizontal movement speed of the driver  160 , the pressure exerted on the sealant  102  supplied from the dispenser  172  to the jet nozzle  174 , and sudden clogging of the jet nozzle  174 . 
     Meanwhile, when applying of a first sealant  102  is completed, the controller  164  controls the driver  160  in accordance with the position information signals PISs, supplied from the broken line detector  168  in real-time, for the broken lines  180   a ,  180   b  and  180   c  in the sealant  102 . Accordingly, under the control of the controller  164 , the driver  160  repositions the jet nozzle  174  to a location on the substrate  111  corresponding to the position information signals PISs for the broken lines  180   a ,  180   b  and  180   c  in the sealant  102  along transfer paths  202 ,  204  and  206  so that sealants  210   a ,  210   b  and  210   c  are additionally applied in the broken lines  180   a ,  180   b  and  180   c  in the sealant  102 , respectively. As a result, the broken lines  180   a ,  180   b  and  180   c  in the sealant  102  are repaired. 
     On the other hand, if no position information signals PISs supplied from the broken line detector  168  for the broken lines  180   a ,  180   b  and  180   c  in the sealant  102  generated upon applying the sealant  102 , the controller  164  controls the driver  160  so as to apply the sealant  102  to another substrate without initiating a repairing process of the sealant to the first substrate. 
     As described above, according to the apparatus and the method of fabricating the flat panel display device of the present invention, light is emitted toward the sealant applied to the substrate upon applying the sealant, and the amount of light transmitted through the sealant is detected in real-time to produce the position information signals for the broken lines in the sealant applied to the substrate. Thereafter, the broken lines in the sealant corresponding to the produced position information signals for the broken lines in the sealant are partially repaired after applying the sealant. As a result, it is possible to save working hours required for applying the sealant. Accordingly, the broken lines are detected through the light sensor in real-time to eliminate later inspection of the broken line in the sealant. As a result, it is possible to reduce fabrication time of the flat panel display device and thus to improve production yield. 
     Although the present invention has been explained by the embodiments shown in the drawings described above, it should be understood to the ordinary skilled person in the art that the invention is not limited to the embodiments, but rather that various changes or modifications thereof are possible without departing from the spirit of the invention. Accordingly, the scope of the invention shall be determined only by the appended claims and their equivalents.