Abstract:
A one drop fill (ODF) liquid crystal display panel has a CF substrate, a TFT substrate, and a liquid crystal layer positioned between the CF substrate and the TFT substrate. The TFT substrate further has a pixel array region positioned in the center part of the TFT substrate, a sealant region position in the periphery region of the TFT substrate, a light-shielding pattern positioned on the sealant region, and a sealant pattern positioned corresponding to the sealant region between the CF substrate and the TFT substrate for assembling the two substrates.

Description:
BACKGROUND OF INVENTION 
   1. Field of the Invention 
   The present invention relates to an LCD panel, and more particularly, to a one drop fill (ODF) LCD panel having a light-shielding pattern capable of preventing light leakage through a peripheral region of the LCD panel. 
   2. Description of the Prior Art 
   LCD displays have been widely applied to a variety of information products, such as notebook computers and PDAs, since they have advantages of tiny size, low power consumption, and low radiation emission. 
   Normally, an LCD panel includes a color filter substrate (CF substrate), a thin film transistor substrate (TFT substrate), and a liquid crystal layer positioned between the CF substrate and the TFT substrate. The TFT substrate further includes a plurality of pixel array regions arranged in arrays on the surface, each pixel array region including a TFT and a pixel electrode for controlling spinning angles of liquid crystal molecules such that each pixel can generate different colors and gray scales. 
   In general, LCD panels can be divided into two types according to methods of filling liquid crystal molecules: vacuum fill LCD and one drop fill (ODF) LCD. In a vacuum fill LCD, the CF substrate and the TFT substrate are combined together with a sealant, and only a hole is kept. Then, liquid crystal molecules are slowly injected into the space between the CF substrate and the TFT substrate by capillarity action. However, this requires a lot of time (ex: several days for assembling a large size LCD) and a great amount of liquid crystal molecules. Therefore, the vacuum fill method is usually applied to fill only small panels with liquid crystal molecules. In an ODF LCD, first, a sealant layer is pasted onto the bordering part of the TFT substrate. Then, liquid crystal molecules are dropped on the central part of a pixel region, and the CF substrate and the TFT substrate are affixed. Finally, an ultraviolet beam is utilized to irradiate the sealant for hardening the sealant such that the CF substrate and the TFT substrate are tightly combined together. In comparison with vacuum fill method, ODF method is more effective (it takes only a few hours to fill a large size LCD), and needs fewer liquid crystal molecules. Hence, at present, the ODF method is normally applied to fill large LCD panels with liquid crystal molecules. 
   Please refer to  FIG. 1 .  FIG. 1  is a schematic diagram of a conventional ODF LCD panel  10  before substrates are combined together. As shown in  FIG. 1 , the ODF LCD panel  10  comprises a CF substrate  12 , and a TFT substrate  14  positioned in parallel with the CF substrate  12 . The ODF LCD panel  10  includes a pixel array region  16  and a sealant region  18 . The pixel array region  16  further comprises a plurality of color filters  20  positioned on the surface of the CF substrate  12  corresponding to the TFT substrate  14 , a plurality of black matrices  22  positioned between any two neighboring color filters  20 , and at least a liquid crystal drop  24  dropped onto the surface of the TFT substrate  14 . 
   Please refer to  FIG. 2 .  FIG. 2  is a schematic diagram of the conventional ODF LCD panel  10  after the CF substrate  12  and the TFT substrate  14  are combined. As shown in  FIG. 2 , the CF substrate  12  and the TFT substrate  14  are connected by a sealant  30  such that the liquid crystal drop  24  is equally spread in the pixel array region  16  between the CF substrate  12  and the TFT substrate  14 . However, since the sealant is a photocuring material, it has to be irradiated by an ultraviolet beam to become completely strengthened so that the CF substrate  12  and the TFT substrate  14  are perfectly affixed and combined together. In addition, if the sealant  30  is not totally hardened, the sealant will react with the liquid crystal molecules so that the efficiency of the liquid crystal molecules will be deteriorated. 
   Please refer to  FIG. 3 .  FIG. 3  is a top view of the conventional ODF LCD panel  10 . As shown in  FIG. 3 , the pixel array region  16  of the ODF LCD panel  10  comprises a plurality of pixels arranged in arrays, and each pixel includes a thin film transistor (TFT)  34  for controlling switching of each pixel  32 . Each pixel  34  includes a gate  36  electrically connected to a scan line  42 , a drain electrically connected to a data line  44 , and a source  40  electrically connected to a pixel electrode  33 . On the other hand, the sealant  18  comprises a plurality of metal conducting wires  26 A and  26 B. The metal conducting wires  26 A and  26 B are respectively connected to each scan line  42  and each data line  44  at one end, and are respectively connected to gate driving ICs (not shown) and source driving ICs (not shown) at the other end. In this case, voltage signals of each IC (not shown) can be delivered to the gate  36  and the source  40  of each TFT  34 . 
   As above mentioned, after the ODF LCD panel  10  is combined together, the sealant  30  needs to be irradiated by an ultraviolet beam for completely hardening the sealant  30 , so that the CF substrate  12  and the TFT substrate  14  become tightly fixed together. Besides, in this case liquid crystal molecules will not react with the sealant  30  so that the function of liquid crystal is not influenced. However, when the ultraviolet beam irradiates the sealant  30  from the front side of the CF substrate  12 , the light source provided by the back light module (not shown) will pass through the gap between the metal conducting wires  26 A and  26 B in the sealant region  18  so that light leakage occurs in the peripheral region of the ODF LCD panel  10 . 
   To avoid this problem, the ultraviolet beam is then irradiated form the back side of the TFT substrate  14  for hardening the sealant  30 , and a black matrix layer (not shown) is installed on the surface of the CF substrate  12  corresponding to the sealant region  18  for preventing from light leakage in conventional technologies. As shown in  FIG. 3 , however, since the metal conducting wires  26 A and  26 B are not transparent, the sealant  30  cannot be completely hardened. In this case, display quality is deteriorated. 
   Therefore, ensuring the sealant of ODF LCD panel is completely irradiated by the ultraviolet beam to avoid light leakage at the bordering part of ODF LCD panel is a key topic for study in designing ODF LCD panels. 
   SUMMARY OF INVENTION 
   It is therefore a primary objective of the present invention to provide an ODF LCD panel capable of solving the light leakage and incomplete hardening problems of conventional ODF LCD panels. 
   According to the present invention, an ODF LCD panel is disclosed. The ODF LCD panel comprises a thin film transistor (TFT) substrate and a color filter (CF) substrate parallel to each other. The TFT substrate includes a pixel array region in the central part, a sealant region in the bordering part, a light-shielding pattern positioned on the surface of the sealant region, a sealant pattern corresponding to the sealant region between the CF substrate and the TFT substrate, and a liquid crystal layer positioned between the CF substrate and the TFT substrate. 
   It is an advantage of the present invention that the light-shielding pattern is capable of preventing from light leakage in the peripheral region of the ODF LCD panel. 
   These and other objects of the present invention will be apparent to those of ordinary skill in the art after having read the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings. 

   
     BRIEF DESCRIPTION OF DRAWINGS 
       FIG. 1  is a schematic diagram of a conventional ODF LCD panel before substrates are combined together. 
       FIG. 2  is a schematic diagram of the conventional ODF LCD panel shown in  FIG. 1  after the CF substrate and the TFT substrate are combined. 
       FIG. 3  is a top view of the conventional ODF LCD panel. 
       FIG. 4  is a schematic diagram of an ODF LCD panel of the present invention before substrates are combined together. 
       FIG. 5  is a schematic diagram of the ODF LCD panel shown in  FIG. 4  after the CF substrate and the TFT substrate are combined. 
       FIG. 6  is a top view of the ODF LCD panel of the present invention. 
       FIG. 7  is a cross section diagram of the ODF LCD panel along a section line  7 — 7  of  FIG. 6 . 
       FIG. 8  is a cross section diagram of the ODF LCD panel along a section line  8 — 8  of  FIG. 6 . 
       FIG. 9  is a schematic diagram of the ODF LCD panel of another embodiment according to the present invention. 
       FIG. 10  is a schematic diagram of the ODF LCD panel of another embodiment according to the present invention. 
   

   DETAILED DESCRIPTION 
   Please refer to  FIG. 4 .  FIG. 4  is a schematic diagram of an ODF LCD panel  50  of the present invention before substrates are combined together. As shown in  FIG. 4 , the ODF LCD panel  50  comprises a CF substrate  52  and a TFT substrate  54  positioned parallel with the CF substrate  52 . In addition, the ODF LCD panel  50  is divided into a pixel array region  56  and a sealant region  58 . The pixel array region  56  includes a plurality of color filters  60  positioned on the surface of the CF substrate  52  corresponding to the TFT substrate  54 , a plurality of black matrices  62  positioned between neighboring color filters  60 , and at least a liquid crystal drop  64  dropped on the surface of the TFT substrate  54 . The sealant region  58  includes a first metal pattern  66  positioned on the surface of the TFT substrate  54 , an insulating layer  68  positioned on the first metal pattern  66 , a second metal pattern  70  positioned on the insulating layer  68 , and a sealant  72  pasted on the surface of the second metal pattern  70  for adhering the CF substrate  52  and the TFT substrate  54 . It is worth noting that liquid crystal drop  64  can also be dropped on the surface of the CF substrate  52 . 
   Please refer to  FIG. 5 .  FIG. 5  is a schematic diagram of the ODF LCD panel  50  shown in  FIG. 4  after the CF substrate  52  and the TFT substrate  54  are combined. As shown in  FIG. 5 , the CF substrate  52  is placed on the TFT substrate  54 . The CF substrate  52  squeezes the liquid crystal drop  64  due to atmospheric pressure such that the liquid crystal drop  64  is equally spread in the pixel region  56  and the CF substrate  52  and the TFT substrate  54  are combined together. In addition, since the sealant  72  is a photocuring material, it has to be irradiated by an ultraviolet beam for being completely hardened so that the CF substrate  52  and the TFT substrate  54  become adhered and fixed together. 
   It is worth noting that the sealant  72  is disposed in the sealant region  58  of the TFT substrate  54  in this embodiment. However, the sealant  72  can be also disposed on the surface of the CF substrate  52  corresponding to the sealant region  58  for achieving the same effect. 
   For more details of the metal pattern design in the sealant region  58 , please refer to  FIG. 6  and  FIG. 7 .  FIG. 6  is a top view of the ODF LCD panel  50  of the present invention.  FIG. 7  is a cross section diagram of the ODF LCD panel  50  along a section line  7 – 7 ″ of  FIG. 6 . As shown in  FIG. 6 , the pixel array region  56  includes a plurality of pixels  74  arranged in arrays. Each pixel  74  includes a thin film transistor (TFT)  76  as a switch. Each TFT  76  includes a gate  78  electrically connected to a scan line  66 A, a drain  80  electrically connected to a data line  70 A, and a source  82  electrically connected to a pixel electrode  83 . In addition, the sealant region  58  further comprises a plurality of scan lines  66 A for connecting the gate  78  of the TFT  76 , and a plurality of data lines  70 A for transferring voltage signals to the pixel electrode  83  of each pixel  74 . 
   It is worth noting that the first metal pattern  66 , the scan lines  66 A, and the gate  78  of each TFT  76  are coplanar and formed simultaneously in the same deposition and photo-etching processes. In addition, the second metal pattern  70  and the data lines  70 A are coplanar and formed in the same deposition and photo-etching processes. Thus, the present invention can be implemented in any standard LCD manufacturing process without adding any steps. In addition, since the primary objective of the present invention is to solve the light leakage and the incomplete sealant hardening problems of the conventional ODF LCD panel, a light-shielding pattern larger than the sealant pattern is therefore formed in the sealant region  58  during the processes of forming the scan lines  66 A and the data lines  70 A. 
   As shown in  FIG. 6  and  FIG. 7 , the sealant region  58  includes a first metal pattern  66 B. The first metal pattern  66 B is connected to the scan lines  66 A at one end, and connected to a gate driving IC (not shown) in the other end so that the voltage signal provided by the gate driving IC (not shown) is delivered to each scan line  66 A. However, the first metal pattern  66 B is not capable of shielding light, thus a second metal pattern  70  is formed on the insulating layer  68  for preventing from light leakage through the first metal pattern  66 B. In this case, when assembling the ODF LCD panel  50 , the sealant  72  is irradiated by the ultraviolet beam from the front side of the CF substrate  52  so that the sealant  72  is completely hardened. Thus, the light leakage problem will not happen in the peripheral region since no light can pass through the sealant region  58 . 
   Please refer to  FIG. 8 .  FIG. 8  is a cross section diagram of the ODF LCD panel  50  shown in  FIG. 6  along a section line  8 - 8 . As shown in  FIG. 6  and  FIG. 8 , the sealant region  58  includes a second metal pattern  70 B. The second metal pattern  70 B is connected to the data lines  70 A, and connected to a source driving IC (not shown) so that the voltage signal provided by the source driving IC (not shown) is delivered to each data line  70 A. However, the second metal pattern  70 B is not capable of shielding light, thus a first metal pattern  66  is formed under the second metal pattern  70 B in advance for preventing from light leakage through the second metal pattern  70 B. Following that, an insulating layer  68  is formed between the first metal pattern  66  and the second metal pattern  70 B. In this case, when assembling the ODF LCD panel  50 , the sealant  72  is irradiated by the ultraviolet beam from the front side of the CF substrate  52  so that the sealant  72  is completely hardened. Thus, the light leakage problem will not happen in the peripheral region since no light can pass through the sealant region  58 . 
   Please refer to  FIG. 9 .  FIG. 9  is a schematic diagram of the ODF LCD panel  50  according to another embodiment of the present invention. As shown in  FIG. 9 , the allocation of the first metal pattern  66 , the insulating layer  68 , and the second metal pattern  70  are similar to those shown in  FIG. 8 . The key difference is that at least a second insulating layer  69  is formed under the second metal pattern  70  for preventing a coupling effect between the first metal pattern  66  and the second metal pattern  70 . 
   Please refer to  FIG. 10 .  FIG. 10  is a schematic diagram of the ODF LCD panel  50  according to another embodiment of the present invention. As shown in  FIG. 10 , the first metal pattern  66 B and the second metal pattern  70  are arranged alternately. In this embodiment, the second metal pattern  70  only needs to be formed over the gap of the first metal pattern  66 B, while the light-shielding effect is perfectly achieved. 
   In comparison with the prior art, the ODF LCD panel of the present invention comprises a first metal pattern and a second metal pattern in the sealant region. When the first metal pattern serves as metal conducting wires, the second metal pattern functions as a light-shielding pattern. On the other hand, when the second metal pattern serves as metal conducting wires, the first metal pattern functions as a light-shielding pattern. Therefore, the light provided by the light source of the back light module is not allowed to pass through the sealant region such that light leakage will not occur in the peripheral region of panel. In addition, since a black matrix layer is not installed in the CF substrate corresponding to the sealant region, the sealant can be completely hardened by the ultraviolet beam irradiating from the front side of the CF substrate. It is also worth noting that if the metal conducting wires are not required in a certain side of the sealant region according to different circuit design, only a single metal layer wider than the sealant region is enough to prevent from light leakage. Moreover, the single metal layer can either be formed in the process of forming the scan line or the data line. 
   Those skilled in the art will readily appreciate that numerous modifications and alterations of the device may be made without departing from the scope of the present invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.