Patent Document

1. FIELD OF THE INVENTION  
       [0001]     The present invention relates to liquid crystal display panels and methods for their manufacture.  
       2. GENERAL BACKGROUND  
       [0002]     An LCD device has the advantages of portability, low power consumption, and low radiation, and has been widely used in various portable information products such as notebooks, personal digital assistants (PDAs), video cameras and the like. Furthermore, the LCD device is considered by many to have the potential to completely replace CRT (cathode ray tube) monitors and televisions.  
         [0003]     The liquid crystal display panel is an important element of the liquid crystal display, and includes two opposite substrates and a liquid crystal layer between the substrates. There are several ways of filling liquid crystal material; for example, the vacuum filling method and the one-drop-fill (ODF) method. In assembly of the panel using the vacuum filling method, the substrates are aligned with each other and joined such that they are separated by a gap on the order of a few microns. The structure is placed in a vacuum chamber for removal of air. The structure is then placed in a dish of liquid crystal material, which is forced into the evacuated panel space by backfilling of the vacuum chamber with nitrogen gas. However, the vacuum filling method is exceedingly slow, and wastes liquid crystal material. Thus the faster ODF method was developed. A version of the ODF method is disclosed in U.S. Pat. No. 5,263,888, issued on Nov. 23, 1993. Using the ODF method can save much time, and generally requires less liquid crystal material.  
         [0004]      FIG. 9  shows a bottom plan view relating to a second substrate  150  of a conventional liquid crystal display panel  1 , and  FIG. 10  shows a schematic, side cross-sectional view of the liquid crystal display panel  1 . Referring to  FIGS. 9 and 10 , the liquid crystal display panel  1  includes a first substrate  100 , the second substrate  150 , and a liquid crystal layer  103  comprising a plurality of liquid crystal molecules. The liquid crystal layer  103  is sandwiched between the first and second substrates  100 ,  150 .  
         [0005]     The first substrate  100  includes a plurality of data lines (not shown) and gate lines (not shown). The data lines are perpendicular to the gate lines. A plurality of TFTs (Thin Film Transistors) is formed at crossings of the data and gate lines. An alignment film  101  is formed on an inner side of the first substrate  100 .  
         [0006]     The second substrate  150  defines a central display area  1502  and a peripheral area  1501 . A sealant  110  in the form of a continuous line is located at the peripheral area  1501 . The sealant  110  is made of a light hardening material; in particular, the sealant  110  is hardened by UV radiation. The first substrate  100  and the second substrate  150  are attached together by the sealant  110 . The liquid crystal layer  103  is separated from air by the sealant  110 . A black matrix  130  in the form of a continuous thick line is located on an inner side of the second substrate  150 , straddling a region where the display area  1502  adjoins the peripheral area  1501  in order to avoid light shielding phenomena. An alignment film  151  is deposited on the inner side of the second substrate  150 , and covers the black matrix  130 .  
         [0007]     The liquid crystal display panel  1  is manufactured by the ODF process. The process includes the steps of: providing the first substrate  100  and the second substrate  150 ; forming the sealant  110  and the black matrix  130  on the second substrate  150 ; dropping liquid crystal material on the display area  1502  of the second substrate  150 , the liquid crystal material comprising a mixture of liquid crystal molecules and spacers; attaching the first substrate  100  and the second substrate  150  together in a vacuum chamber; and curing the sealant  110  by applying UV (ultraviolet) light. When the sealant  110  has hardened, formation of the liquid crystal display panel  1  is completed.  
         [0008]     However, the display area  1502  adjoins the sealant  110  of the liquid crystal display panel  1 . In the process of manufacturing the liquid crystal display panel  1  using the ODF method, thermal setting epoxy cannot be used. Instead, UV-curable epoxy or another kind of epoxy which cures near room temperature must be used. As will be understood, the uncured sealant  110  must necessarily come in contact with the liquid crystal molecules because the sealant  110  forms the peripheral boundary wall for the liquid crystal material. There is mounting evidence that uncured sealant  110  tends to react with the liquid crystal molecules, and degrade the performance of the liquid crystal molecules as liquid crystal material. This deleterious effect is especially likely in those regions of the display panel where there is incomplete curing of the UV epoxy. Incomplete curing occurs where UV light is unable to reach all portions of the UV epoxy, due to shadows cast by the thin film circuitry that extends out to peripheral areas of the substrates  100 ,  150 .  
         [0009]     What is needed, therefore, is a liquid crystal display panel which overcomes the above-described deficiencies.  
         [0010]     What is also needed is a method for manufacturing a liquid crystal display panel which overcomes the above-described deficiencies.  
       SUMMARY  
       [0011]     One embodiment provides a liquid crystal display panel including a first substrate and a second substrate opposite to each other, the second substrate defining a display area and a peripheral area; a liquid crystal layer containing a plurality of liquid crystal molecules disposed between the first and second substrates; a sealant associated with the peripheral area for supporting and adhering the first and second substrates together; and an isolating member isolating the sealant from the liquid crystal layer.  
         [0012]     In another embodiment, a method for manufacturing the liquid crystal display panel includes the following steps: providing a first substrate and a second substrate, the second substrate defining a display area and a peripheral area; forming a sealant associated with the peripheral area of the second substrate; forming an isolating member associated with the peripheral area of the second substrate, the isolating member being associated with the sealant; dropping liquid crystal material on the first substrate; attaching and integrating the first substrate and the second substrate together in a vacuum chamber; and hardening the sealant using ultraviolet light.  
         [0013]     Compared with a conventional liquid crystal display panel, the first above-described embodiment has the following advantage. The liquid crystal display panel of a preferred embodiment includes the isolating member disposed between the liquid crystal layer and the sealant. This prevents the liquid crystal molecules from reacting with the uncured sealant, and improves the performance of the liquid crystal display.  
         [0014]     Other advantages and novel features will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings, in which: 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]      FIG. 1  is a schematic, bottom plan view of one substrate and associated components of a liquid crystal display panel in accordance with a first preferred embodiment of the present invention;  
         [0016]      FIG. 2  is a schematic, cross-sectional view of the liquid crystal display panel in accordance with the first preferred embodiment;  
         [0017]      FIGS. 3 and 4  are schematic, cross-sectional views of sequential stages in a method for manufacturing the liquid crystal display panel of the first preferred embodiment;  
         [0018]      FIG. 5  is a schematic, bottom plan view of one substrate and associated components of a liquid crystal display panel in accordance with a second preferred embodiment of the present invention;  
         [0019]      FIG. 6  is a schematic, cross-sectional view of the liquid crystal display panel in accordance with the second preferred embodiment;  
         [0020]      FIGS. 7 and 8  are schematic, cross-sectional views of sequential stages in a method for manufacturing the liquid crystal display panel of the second preferred embodiment;  
         [0021]      FIG. 9  is a schematic, bottom plan view of one substrate and associated components of a conventional liquid crystal display panel; and  
         [0022]      FIG. 10  is a schematic, cross-sectional view of the conventional liquid crystal display panel referred to in the above paragraph. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0023]      FIG. 1  shows a bottom plan view relating to a second substrate  350  of a liquid crystal display panel  3  in accordance with a first preferred embodiment of the present invention.  FIG. 2  shows a cross-sectional view of the liquid crystal display panel  3 . Referring to  FIGS. 1 and 2 , the liquid crystal display panel  3  includes a first substrate  300 , the second substrate  350  and a liquid crystal layer (not shown in full) comprising a plurality of liquid crystal molecules  303 . The liquid crystal layer is sandwiched between the first and second substrates  300 ,  350 .  
         [0024]     An alignment film  301  is formed on an inner side of the first substrate  300 . The first substrate  300  includes a plurality of data lines (not shown) and gate lines (not shown). The data lines are perpendicular to the gate lines. A plurality of TFTs (Thin Film Transistors) is formed at crossings of the data and gate lines. A plurality of pixel electrodes (not shown) is deposited on the first substrate  300 , the pixel electrodes being connected with drain electrodes of the TFTs.  
         [0025]     An alignment film  351  is formed on an inner side of the second substrate  350 . The second substrate  350  includes a color filter (not shown) and a common electrode (not shown). The common electrode and the pixel electrode can form an electric field to drive the liquid crystal molecules  303 , so that a display of the liquid crystal display panel  3  is obtained.  
         [0026]     The second substrate  350  defines a central display area  3502  and a peripheral area  3501 . A sealant  310  in the form of a continuous line is located at the peripheral area  3501 . The sealant  310  is made of a light hardening material; in particular, the sealant  310  is hardened by UV radiation. The first substrate  300  and the second substrate  350  are attached together by the sealant  310 . A blocker  360  in the form of a continuous line is located around a periphery of the display area  3502 . The liquid crystal molecules  303  and the sealant  310  are separated by the blocker  360 , in order to avoid reaction between the liquid crystal molecules  303  and the uncured sealant  310 . The blocker  360  is made of elastic material, such as Polymethyl Methacrylate (PMMA), Natural Rubber (NR), Styrene Butadiene Rubber (SBR), Isobutylene-Isoprene Rubber (IIR), Nitrile-Butadiene Rubber (NBR), or Ethylene-Propylene-Diene Monomer (EPDM). The blocker  360  and the sealant  310  are spaced apart by a substantially uniform gap. A black matrix  330  in the form of a continuous thick line is located on the inside of the second substrate  350 , straddling a region where the display area  3502  adjoins the peripheral area  3501  in order to avoid light shielding phenomena. The black matrix  330  is made from chromium (Cr) and is opaque. The black matrix  330  covers the blocker  360  and is spaced a horizontal distance from the sealant  310 , so that light can pass through the second substrate  350  and harden the sealant  310 .  
         [0027]      FIGS. 3 and 4  are schematic, cross-sectional views of sequential stages in a method for manufacturing the liquid crystal display panel  3 .  
         [0028]     Referring to  FIG. 3 , the first substrate  300  and the second substrate  350  are provided. The second substrate  350  includes the peripheral area  3501  and the display area  3502 . The black matrix  330  is formed on a region straddling the peripheral area  3501  and the display area  3502 . The alignment film  351  is formed on the second substrate  350 , and covers the black matrix  330 . The alignment film  301  is formed on the first substrate  300 . A plurality of spacers (not shown) is deposited on the alignment film  301 .  
         [0029]     Referring to  FIG. 4 , liquid crystal molecules  303  are dropped on the alignment film  301 . The sealant  310  is formed on the alignment film  351  in the peripheral area  3501 . The sealant  310  and the black matrix  330  are spaced apart by a horizontal gap, so that light can pass through the second substrate  350  and harden the sealant  310 . The blocker  360  is formed on the alignment film  351 . The blocker  360  is deposited between the sealant  310  and the display area  3502 , so that it can separated the sealant  310  and the liquid crystal molecules  303 .  
         [0030]     Referring to  FIG. 2 , the second substrate  350  is turned over and positioned on the first substrate  300 . Assembly of the first substrate  300  and the second substrate  350  is performed in a vacuum chamber (not shown). After that, the combined substrates  300 ,  350  are taken out from the vacuum chamber. The substrates  300 ,  350  are securely held together by reason of atmospheric pressure exerting on the combination. Then the sealant  310  is hardened by U radiation, so that the substrates  300 ,  350  are firmly attached together. The liquid crystal display panel  3  is thus formed.  
         [0031]      FIG. 5  shows a bottom plan view relating to a second substrate  450  of a liquid crystal display panel  4  in accordance with a second preferred embodiment of the present invention.  FIG. 6  shows a cross-sectional view of the liquid crystal display panel  4 . Referring to  FIGS. 5 and 6 , the liquid crystal display panel  4  includes a first substrate  400  and the second substrate  450 . The second substrate  450  defines a central display area  4502  and a peripheral area  4501 . A sealant  410  and a blocker  460  are formed on the peripheral area  4501 , and are spaced apart by a substantially uniform gap. A black matrix  430  is formed on a region straddling the display area  4502  and the peripheral area  4501 . An optical spacer  470  in the form of continuous line is formed on the peripheral area  4501 . The optical spacer  470  is spaced apart from an outside extremity of the black matrix  430  by a horizontal gap. The optical spacer  470  helps the liquid crystal display panel  4  have a uniform thickness.  
         [0032]      FIGS. 7 and 8  are schematic, cross-sectional views of sequential stages in a method for manufacturing the liquid crystal display panel  4 .  
         [0033]     Referring to  FIG. 7 , the first substrate  400  and the second substrate  450  are provided. The second substrate  450  includes the peripheral area  4501  and the display area  4502 . The black matrix  430  is formed on the region straddling the peripheral area  4501  and the display area  4502 . The alignment film  451  is formed on the second substrate  450 , and covers the black matrix  430 . The alignment film  401  is formed on the first substrate  400 .  
         [0034]     Referring to  FIG. 8 , liquid crystal molecules  403  are dropped onto the alignment film  401 . The sealant  410  is formed on the alignment film  451  in the peripheral area  4501 . The sealant  410  and the black matrix  430  are spaced apart by a horizontal gap, so that light can pass through the second substrate  450  and harden the sealant  410 . The blocker  460  is formed on the alignment film  451 . The blocker  460  is deposited between the sealant  410  and the display area  4502 , so that it can separate the sealant  410  and the liquid crystal molecules  403 . The optical spacer  470  is formed on the alignment film  451  in a position corresponding to beyond the outside extremity of the black matrix  430 .  
         [0035]     Referring to  FIG. 6 , the second substrate  450  is turned over and positioned on the first substrate  400 . Assembly of the first substrate  400  and the second substrate  450  is performed in a vacuum chamber (not shown). After that, the combined substrates  400 ,  450  are taken out from the vacuum chamber. The substrates  400 ,  450  are securely held together by reason of atmospheric pressure exerting on the combination. Then the sealant  410  is hardened by UV radiation, so that the substrates  400 ,  450  are firmly attached together. The liquid crystal display panel  4  is thus formed.  
         [0036]     Many modifications and variations are possible within the ambit of the invention herein. For example, the blocker and the sealant may be connected together. The blocker, the sealant and the optical spacer may be formed on the first substrate instead of the second substrate. The black matrix may be made from chromium oxide (CrOx).  
         [0037]     It is believed that the present embodiments and their advantages will be understood from the foregoing description, and it will be apparent that various changes may be made thereto without departing from the spirit and scope of the invention or sacrificing all of its material advantages, the examples hereinbefore described merely being preferred or exemplary embodiments of the invention.

Technology Category: 3