Patent Publication Number: US-2005139283-A1

Title: Apparatus and method for dropping liquid crystal

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to an apparatus and a method for filling liquid crystal into a liquid crystal display (LCD) cell, and especially to an apparatus and a method for dropping liquid crystal using one-drop-filling (ODF) technology.  
      2. Description of Prior Art  
      An LCD cell generally comprises two panels, a peripheral sealant, and a multiplicity of liquid crystal molecules retained between the panels and sealant. The sealant is printed on one of the panels, and is subsequently adhered to the other panel. The panels and the sealant cooperatively form a space therebetween, with the liquid crystal molecules being filled in the space.  
      There are generally two methods used for filling the liquid crystal molecules into the space. The first method is to fill the liquid crystal molecules through filling ports. This method comprises the following steps: firstly, printing a sealant on a first panel, wherein the sealant is rectangular and has one or more gaps that function as filling ports; secondly, combining a second panel with the first panel and curing the sealant, whereby a space is enclosed by the sealant and the two panels; thirdly, immersing the filling ports in a liquid crystal in a vacuum chamber; and fourthly, introducing gas into the vacuum chamber to make the liquid crystal molecules fill up the space.  
      The second method is the so-called one-drop-filling (ODF) method. This method comprises the following steps: firstly, printing a sealant on a first panel, wherein the sealant is rectangular and continuous, and a space is enclosed by the sealant and the first panel; secondly, releasing liquid crystal molecules into the space drop by drop using a dispenser; and thirdly, combining a second panel with the first panel and curing the sealant.  
      Referring to  FIG. 5 , this shows a liquid crystal dropping apparatus as disclosed in U.S. Pat. No. 5,511,591. The apparatus comprises a vacuum chamber  8 , a vacuum pump  9 , an X-Y moving table  26 , and a liquid crystal dispenser  10 . The vacuum pump  9  is used to evacuate the inside of the vacuum chamber  8  to a pressure of about 0.1 torr. The table  26  is installed in the vacuum chamber  8 , and can move in X and Y directions. The liquid crystal dispenser  10  is installed above the table  26 , and comprises a capillary  63  used to release liquid crystal drop by drop.  
      Also referring to  FIGS. 6A  to  6 C, an ODF method for dropping liquid crystal using the above-described liquid crystal dropping apparatus comprises the following steps: firstly, setting a lower panel  23  on the table  26 , a periphery of the lower panel  23  having adhering paste  24  applied thereon; secondly, dropping a desired amount of liquid crystal L down onto the surface of lower panel  23  inside the loop of applied adhering paste  24 ; and thirdly, placing an upper panel  25  on the lower panel  23 , and curing the adhering paste  24  with light from lamps  28 , thereby laminating the upper panel  25  onto the lower panel  23 .  
      Because the desired amount of liquid crystal L can be easily controlled by the dispenser  10 , the ODF method is more convenient than the method of filling liquid crystal molecules through filling ports. In addition, the ODF method has a shorter filling time, and wastes less liquid crystal material.  
      In many modern manufacturing facilities, the lower panel  23  is not simply a single glass substrate. Referring to  FIG. 7 , for example, a glass substrate  200  may require processing. The glass substrate  200  has a regular size corresponding to an industry standard. The glass substrate  200  is divided into four panels  201 ,  202 ,  203 ,  204  of equal size. The above-described liquid crystal dropping apparatus is convenient to use on the glass substrate  200 , and the overall dropping time can be reduced. This is especially the case where the liquid crystal dropping apparatus comprises a plurality of dispensers  10 .  
      Referring to  FIG. 8 , in another example, a glass substrate  300  is divided into two large panels  301 ,  303  and two small panels  302 ,  304 . The small panels  302 ,  304  are defined in addition to the large panels  301 ,  303 , in order to make full use of the glass substrate  300 . In this case, the above-described liquid crystal dropping apparatus has some drawbacks. The desired amount of liquid crystal corresponding to one kind of panel is controlled by the dispenser  10  before dropping. Therefore when the size of the panel is changed, the corresponding manipulator must adjust the dispenser  10  again. Even in the case where the liquid crystal dropping apparatus comprises a plurality of dispensers  10 , the liquid crystal dropping apparatus cannot drop liquid crystal onto different panels of a glass substrate simultaneously.  
      Thus, a new liquid crystal dropping apparatus and method which overcome the above-mentioned disadvantages are desired.  
     SUMMARY OF THE INVENTION  
      An object of the present invention is to provide a liquid crystal dropping apparatus that can drop liquid crystal onto different panels of a glass substrate simultaneously.  
      Another object of the present invention is to provide a liquid crystal dropping method that can drop liquid crystal onto different panels of a glass substrate simultaneously.  
      In order to achieve the first object set out above, a liquid crystal dropping apparatus comprises a vacuum chamber and two liquid crystal dispensers. The liquid crystal dispensers are installed in the vacuum chamber, and are used to release different desired amounts of liquid crystal simultaneously.  
      In order to achieve the second object set out above, an exemplary liquid crystal dropping method comprises the steps of: providing two liquid crystal dispensers; providing a first substrate divided into two panels, and positioning the first substrate so that each panel is below a corresponding liquid crystal dispenser; and releasing different amounts of liquid crystal onto said panels via said liquid crystal dispensers simultaneously.  
      Other objects, advantages, and novel features of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings, in which: 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a cutaway side view of a liquid crystal dropping apparatus according to the present invention, showing a lower glass substrate inside the apparatus;  
       FIG. 2  is a flow chart of an exemplary liquid crystal dropping method according to the present invention;  
       FIG. 3  is an enlarged view of part of  FIG. 1 , showing dropping of liquid crystal onto the lower glass substrate;  
       FIG. 4  is a similar to  FIG. 3 , but showing an upper glass substrate laminated onto the lower glass substrate, and curing of a sealant between the substrates by lamps;  
       FIG. 5  is a cutaway view of a conventional liquid crystal dropping apparatus;  
       FIGS. 6A  to  6 C are schematic, side cross-sectional views showing successive stages in a liquid crystal dropping method using the liquid crystal dropping apparatus of  FIG. 5 ;  
       FIG. 7  is an enlarged, top plan view of a glass substrate divided into four panels of equal size; and  
       FIG. 8  is an enlarged, top plan view of a glass substrate divided into four panels of different sizes. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      Reference will now be made to the drawings to describe the present invention in detail.  
      Referring to  FIG. 1 , a liquid crystal dropping apparatus  100  in accordance with the present invention comprises a vacuum chamber  80 , a first liquid crystal dispenser  42 , a first holding device  41 , a second liquid crystal dispenser  52 , a second holding device  51 , and a table  43 .  
      The vacuum chamber  80  comprises an opening  81 , a cover  82 , and a vacuum pump  90 . The opening  81  is used to transfer a lower glass substrate  40  having a first lower panel  44  and a second lower panel  54  into the vacuum chamber  80 , and transfer the lower glass substrate  40  out of the vacuum chamber  80  after the liquid crystal is dropped. The first lower panel  44  is larger than the second lower panel  54 . The vacuum pump  90  is used to evacuate the inside of the vacuum chamber  80  to a vacuum state after the cover  82  seals the opening  81 .  
      The first liquid crystal dispenser  42 , first holding device  41 , second liquid crystal dispenser  52 , second holding device  51  and table  43  are installed in the vacuum chamber  80 . The first holding device  41  is an X-Y moving mechanism, and is used to hold the first liquid crystal dispenser  42 . The second holding device  51  is an X-Y moving mechanism, and is used to hold the second liquid crystal dispenser  52 .  
      The table  43  is an X-Y moving table, and is installed below the liquid crystal dispensers  42  and  52 . When the glass substrate  40  is set on the table  43 , the first lower panel  44  of the glass substrate  40  is under the first dispenser  42 , and the second lower panel  54  of the glass substrate  40  is under the second dispenser  52 .  
      The first liquid crystal dispenser  42  comprises a first controller (not shown). The first controller can control the first liquid crystal dispenser  42  regarding the amount of liquid crystal released and the duration of release of liquid crystal. The amount of released liquid crystal corresponds to the size of the first lower panel  44 . The second liquid crystal dispenser  52  comprises a second controller (not shown). The second controller can control the second liquid crystal dispenser  52  regarding the amount of liquid crystal released and the duration of release of liquid crystal. The amount of released liquid crystal corresponds to the size of the second lower panel  54 .  
      Because the liquid crystal dropping apparatus  100  has two dispensers  42  and  52 , two different amounts of liquid crystal can be controlled and dropped by the two dispensers  42  and  52  simultaneously. Thus, even though the glass substrate  40  has the two different panels  44 ,  54  needing liquid crystal dropped thereon, the liquid crystal dropping apparatus  100  can still drop the needed liquid crystal onto the panels  44 ,  54  simultaneously.  
       FIG. 2  is a flow chart of the exemplary liquid crystal dropping method according to the present invention, which is performed using the liquid crystal dropping apparatus  100 . Details of the method will be described as follows, with reference to  FIG. 3  and  FIG. 4  also.  
      In step  101 , the first liquid crystal dispenser  42  and the second liquid crystal dispenser  52  are provided. As described above, the first liquid crystal dispenser  42  and the second liquid crystal dispenser  52  are controlled by different controllers, and the release amounts and times of the dispensers  42  and  52  are different.  
      In step  103 , the lower glass substrate  40  having the first lower panel  44  and the second lower panel  54  is provided. Referring to  FIG. 1  and  FIG. 3 , the lower glass substrate  40  is set on the table  43 . The first lower panel  44  corresponds to the first dispenser  42 , and the second lower panel  54  corresponds to the second dispenser  52 . The first lower panel  44  is larger than the second lower panel  54 . Adhering sealants  45  and  55  are applied along margins of the first lower panel  44  and the second lower panel  54 , respectively. The sealants  45  and  55  are made of an ultraviolet curable sealing material, and can be cured by ultraviolet radiation.  
      In step  105 , different amounts of liquid crystal are released by the dispensers  42 ,  52  simultaneously. Referring to  FIG. 3 , a first amount of liquid crystal  46  is released onto the first lower panel  44  by the first liquid crystal dispenser  42 , and a second amount of liquid crystal  56  is released onto the second lower panel  54  by the second liquid crystal dispenser  52 . The first amount of liquid crystal  46  is greater than the second amount of liquid crystal  56 .  
      Finally, referring to  FIG. 4 , an upper glass substrate  48  is laminated onto the lower glass substrate  44 , with the sealants  45  and  55  being cured by ultraviolet radiation from lamps  47 .  
      When the liquid crystal is dropped, the first holding device  41  and the second holding device  42  can each move in X and Y directions, so that the liquid crystal is evenly distributed on the panels  44  and  54 . Alternatively, the holding devices  41  and  51  can be fixed, with only the table  43  moving in X and Y directions.  
      In summary, because different amounts of liquid crystal corresponding to the sizes of the panels  44 ,  54  can be controlled and dropped by the two dispensers  42  and  52 , the method of present invention provides simultaneous liquid crystal dropping onto a glass substrate having different panels. Thus the processing time of liquid crystal dropping is reduced. The method speeds up the manufacturing of an LCD cell.  
      It is to be understood, however, that even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.