Abstract:
A method of fabricating an LCD device is discussed. The method according to an embodiment includes combining a first substrate having thin film transistors with a second substrate having black matrices and color filters using a sealant. Also, the method includes: forming an absorbent layer which is positioned to overlap with an edge of the sealant and burned by a laser; curing the sealant partially covered with the absorbent layer by irradiating UV light; burning the absorbent layer using a laser beam; and cutting the sealant through the burnt absorbent layer and the second substrate opposite to the absorbent layer using a scriber.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority under 35 U.S.C. 119 to Korean Patent Application No. 10-2011-0034466, filed on Apr. 13, 2011, which is hereby incorporated by reference in its entirety. 
     BACKGROUND 
     1. Field of the Disclosure 
     This disclosure relates to a liquid crystal display (LCD) device, and more particularly to an LCD device fabricating method capable of enhancing the reliability of the LCD device and realizing a narrow bezel panel by reducing the size of a bezel. 
     2. Description of the Related Art 
     In general, the LCD device applies data signals, corresponding to image information, to liquid crystal cells arranged in an active matrix shape and controls the transmittance of the liquid crystal cells so that the desired image is displayed. To this end, the LCD device includes an LCD panel configured to display images and a drive circuitry configured to apply driving signals to the LCD panel. 
     The LCD panel includes first and second glass substrates combined with each other with a fixed space therebetween and a liquid crystal layer with an anisotropic dielectric constant interposed between the first and second glass substrates. Such an LCD panel displays a desired image by controlling the quantity of transmitting light through the adjustment of an electrical field which is applied to the liquid crystal layer with the anisotropic dielectric constant. 
     The first glass substrate (a thin film transistor array substrate) includes a plurality of gate lines, a plurality of data lines, a plurality of pixel electrodes, and a plurality of thin film transistors. The gate lines are arranged in a direction on the first glass substrate in such a manner as to be separate by a fixed interval from one another. The data lines are arranged in another direction perpendicular to the arranged direction of the gate lines in such a manner as to be separate by a fixed interval from one another. The pixel electrodes are formed in pixel regions which are defined by the gate and data lines crossing each other, respectively. The thin film transistors are switched by signals on the respective gate lines and transfer signals on the respective data lines to the respective pixel electrodes. 
     The second glass substrate (a color filter substrate) includes a black matrix layer, red, green and blue color filter layers, and a common electrode. The black matrix layer is used to shield light in the rest portion of the second glass substrate without the pixel regions. The red, green and blue color filter layers are used to realize a variety of colors. The common electrode is used for realizing an image. 
     The first and second glass substrates are combined with each other by a sealant in such a manner as to have a fixed space provided by spacers therebetween. Then, the liquid crystal layer is formed between the first and second substrates. 
     As such, the LCD device sequentially applies a turning-on signal to the gate lines, and supplies data signals to the data lines whenever the turning-on signal is applied, thereby displaying a desired image on the LCD panel. 
     The LCD panel is prepared by combining first and second glass substrates spaced from each other with a fixed distance using a sealant and forming the liquid crystal layer between the two substrates. The first glass substrate has a margin area. As such, the first glass substrate has a wider area than that of the second glass substrate. A gate pad portion connected to the gate lines and a data pad portion connected to the data lines are formed in the margin area of the first glass substrate that is not overlapping with the second glass substrate. 
     In order to maintain a cell gap between the combined first and second glass substrates, the sealant is hardened using ultraviolet (UV) light. Then, the combined glass substrates are cut and processed in units of LCD panel. 
     Meanwhile, in order to minimize a bezel area, a scribe-on-seal method is proposed which irradiates a laser beam on the sealant and cuts the combined substrates. In other words, the scribe-on-seal method performs a burning process by focusing a laser beam on the sealant before the cutting process. 
     However, the range of wavelengths being absorbed by the sealant is limited. As such, it is necessary to provide a high-energy laser beam to the burning process. 
     More specifically, the sealant is formed from transparent acrylic and epoxy based materials, and hardened into a light gray solid through the irradiation of UV light. If the burning process using a laser beam is performed for the hardened sealant with the light gray color, the laser beam must have a high energy (or a high power). This results from the fact that the wavelength range being absorbed into the light gray sealant is limited. 
     If the burning process using the high energy laser beam is performed before the process of cutting the second glass substrate, the circumference of a cutting plane can be damaged due to heat being generated by the high energy laser beam. Also, the sealant can also be damaged. Due to this, reliability of the LCD device can deteriorate. 
     BRIEF SUMMARY 
     Accordingly, the present embodiment is directed to a fabricating method of the LCD device that substantially obviates one or more of problems due to the limitations and disadvantages of the related art. 
     An object of the present embodiments is to provide a fabricating method of the LCD device that is adapted to implement a narrow bezel panel and enhance reliability of the LCD device by forming a resin or pigment pattern on a part of a sealant, combining lower and upper substrates, and performing a burning process for the resin or pigment pattern on the sealant using a laser beam before a scribing process. 
     Additional features and advantages of the embodiments will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the embodiments. The advantages of the embodiments will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings. 
     An LCD device fabrication method according to one general aspect of the present disclosure includes combining a first substrate having thin film transistors with a second substrate having black matrices and color filters using a sealant. Also, the LCD device fabrication method includes: forming an absorbent layer which is positioned to overlap with an edge of the sealant and burned by a laser; curing the sealant partially covered with the absorbent layer by irradiating UV light; burning the absorbent layer using a laser beam; and cutting the sealant through the burnt absorbent layer and the second substrate opposite to the absorbent layer using a scriber. 
     Other systems, methods, features and advantages will be, or will become, apparent to one with skill in the art upon examination of the following figures and detailed description. It is intended that all such additional systems, methods, features and advantages be included within this description, be within the scope of the invention, and be protected by the following claims. Nothing in this section should be taken as a limitation on those claims. Further aspects and advantages are discussed below in conjunction with the embodiments. It is to be understood that both the foregoing general description and the following detailed description of the present disclosure are exemplary and explanatory and are intended to provide further explanation of the disclosure as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are included to provide a further understanding of the embodiments and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the disclosure. In the drawings: 
         FIG. 1  is a cross-sectional view of an LCD device according to an embodiment of the present disclosure; 
         FIG. 2  is a view illustrating a method of fabricating the LCD device of  FIG. 1 ; 
         FIG. 3  is a cross-sectional view showing the combined state of the first and second substrates which are shown in  FIG. 2 ; and 
         FIGS. 4A through 4C  are cross-sectional views illustrating processes which are performed after combining the first and second substrates as shown in  FIG. 3 . 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to the embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings. These embodiments introduced hereinafter are provided as examples in order to convey their spirits to the ordinary skilled person in the art. Therefore, these embodiments might be embodied in a different shape, so are not limited to these embodiments described here. In the drawings, the size, thickness and so on of a device can be exaggerated for convenience of explanation. Wherever possible, the same reference numbers will be used throughout this disclosure including the drawings to refer to the same or like parts. 
       FIG. 1  is a cross-sectional view of an LCD device according to an embodiment of the present disclosure. 
     As shown in  FIG. 1 , the LCD device according to an embodiment of the present disclosure includes first and second substrates  100  and  200 . The first and second substrates  100  and  200  can be defined into an active area AA and a non-display area NA. 
     The active area AA is used for displaying an image. A thin film transistor TFT and a pixel electrode  130  are formed within the active area AA of the first substrate  100  and used for displaying an image on the first substrate  100 . 
     The non-display area NA is prepared regardless of the image display. Pads  230  are formed in the non-display area NA of the first substrate  100 . The pads  230  are connected to an external drive circuit and used to transfer image signals to elements within the active area AA. Such pads  230  can be divided to configure a pad portion  210  and a ground portion  220 . The pad portion  210  can include a gate part and a data part. The ground portion  220  performs a grounding function. 
     The second substrate  200  can include a black matrix  190 , color filters  180  and a common electrode which are sequentially formed in the active area AA. The black matrix  190  is formed at a position opposite to the thin film transistor TFT. Also, the black matrix  190  is formed on edges of the LCD device (i.e., the second substrate  200 ) in order to prevent light leakage in the other area except the active area AA. 
     A sealant  160  is formed in the non-display area NA between the first and second substrate. A liquid crystal layer  150  is formed in the active area AA between the first and second substrates  100  and  200 . 
     A gate electrode  102  is formed on the first substrate  100  and from a conductive material such as a metal. A gate insulation film  110  including silicon nitride SiN x  or silicon oxide SiO 2  is formed to cover the gate electrode  102 . 
     An active layer  104  is formed on the gate insulation film  110  opposite to the gate electrode  102 . The active layer  104  is formed from amorphous silicon. Also, an ohmic contact layer  106  is formed on the active layer  104 . The ohmic contact layer  106  can be formed from amorphous silicon doped with an impurity. 
     Source and drain electrodes  108   a  and  108   b  are formed on the ohmic contact layer  106 . The source and drain electrodes  108   a  and  108   b  are formed from a conductive material such as a metal. Such source and drain electrodes  108   a  and  108   b  together with the gate electrode  102  are used to form the thin film transistor TFT. 
     Although it is not shown in the drawings, the gate electrode  102  is connected to a gate line, and the source electrode  108   a  is connected to a data line. The gate line and the data line cross each other and define a pixel region. 
     Also, a protective layer  120  is formed to cover the source and drain electrodes  108   a  and  108   b . The protective layer  120  can be formed from silicon nitride, silicon oxide or an organic insulation material. The protective layer  120  includes a contact hole exposing the drain electrode  108   b.    
     A pixel electrode  130  is formed within the pixel region on the protective layer  120 . The pixel electrode  130  can be formed from a transparent conductive material. Such a pixel electrode  130  is connected to the drain electrode  108   b  through the contact hole. 
     The second substrate  200  is disposed over the first substrate  100  and spaced from a fixed distance. The second substrate  200  can be formed from a transparent insulation material. The black matrix  190  is formed on the inner surface of the second substrate  200  opposite to the thin film transistor TFT. 
     The color filters  180  are formed on the second substrate  200  provided with the black matrix  190 . The color filters  190  include red, green and blue color filters alternately arranged with one another. Each of the red, green and blue color filters is disposed in one pixel region defined by the black matrix  190 . 
     The common electrode  170  is formed on the color filters  180  and the black matrix  180 . The common electrode  170  can be formed from a transparent conductive material. 
     A liquid crystal layer  150  is formed between the first and second substrates  100  and  200 . Also, the sealant  160  is formed between the first and second substrates  100  and  200 . The sealant  160  prepares a gap to be used for the injection of a liquid crystal material to prevent leakage of the injected liquid crystal material. 
     Although it is not shown in the drawings, an absorbent layer able to absorb a wide wavelength range of laser light can be formed on a part of the sealant  160  within the non-display area NA. The absorbent layer can be formed from either a resin-based material that is the same as the black matrix  190 , or a pigment that is the same as the color filter  180 . So, the absorbent layer is formed from the same material as the black matrices  190  when the black matrices  190  are formed from the resin-based material. And the absorbent layer is formed from the same material as the color filters  180  when the color filters  180  are formed from the pigment. 
     Such first and second substrates  100  and  200  are combined with each other by the sealant  160  and cut into the size of a desired product model through a cutting process using a scriber. Then, a part of the sealant  160  is exposed to the exterior of the second substrate  200 . 
     More specifically, the absorbent layer overlapping with a part of the sealant  160  is burnt during a burning process using a laser beam, and then a part of the second substrate  200  is removed together with the burnt absorbent layer through a cutting process. In accordance therewith, a part of the sealant  160  can be exposed. 
     In this way, the method of the present disclosure allows the absorbent layer overlapping with a part of the sealant  160  to be burnt during a burning process using a laser beam, and then the second substrate  200  and the burnt absorbent layer to be cut through a cutting process. Therefore, the effect of the laser beam being directly applied to the sealant  160  can be minimized. 
     Subsequently, a method of fabricating the above-mentioned LCD device will be described. 
       FIG. 2  is a view illustrating a method of fabricating the LCD device of  FIG. 1 .  FIG. 3  is a cross-sectional view showing the combined state of the first and second substrates which are shown in  FIG. 2 . 
     As shown in  FIGS. 2 and 3 , first and second substrates  100  and  200  are prepared. Each of the first and second substrates  100  and  200  is formed from a glass plate with a fixed thickness. Such first and second substrates  100  and  200  are formed in a size large enough to make four liquid crystal panels. 
     A display circuit portion  155  is formed in each of four active areas AA of the first substrate  100 . The display circuit portion  155  includes thin film transistors, pixel electrodes and so on. The thin film transistor is formed using a multi-crystalline silicon film as an active layer. Also, pads  230  are in non-display areas NA of the first substrate  100 . 
     Thereafter, sealants  160  are formed in frame shapes each surrounding the active areas AA through a coating process. The sealant  160  can be formed from an adhesive material such as a thermosetting material, a photo (UV) curing material or others. For example, the sealant  160  can be formed by coating a transparent acrylic-based or epoxy-based material using a dispenser. The sealant is formed between the first and second substrates  100  and  200  and opposite to the pads  230 . 
     Meanwhile, a black matrix  190 , color filters  180  and a common electrode  170  are formed in each of the active areas AA of the second substrate  200 . The common electrode  170  is formed from a transparent conductive material. 
     Afterward, a fixed quantity of liquid crystal material is loaded on each of the areas surrounding the sealants  160 . Then, the first and second substrates  100  and  200  are aligned so that the active areas AA of the first substrate  100  face the common electrodes  170  of the second substrate  200 . 
     Subsequently, the first and second substrates  100  and  200  are pressed with a fixed pressure in their facing direction and bound to each other by the sealants  160 . The bound first and second substrates  100  and  200  are combined with each other by curing the sealants  160 . 
     To this end, an absorbent layer  190   a  is formed to overlap with outer edges of the sealants  160 . The absorbent layer  190   a  is formed from the same material as the black matrix  190  which is formed in each of the active areas AA of the second substrate  200 . Such an absorbent layer  190   a  can be formed to overlap with the outer edges of the sealants  160  by being patterned together with the black matrices  190 . 
     When the sealants  160  are cured using heat or UV light for the combination of the first and second substrates  100  and  200 , the absorbent layer  190   a  shields the outer edges of the sealants  160  from UV light. As such, the outer edge of each sealant  160  overlapping with the absorbent layer  190   a  is lightly cured compared to the rest of each sealant  160  not overlapping with the absorbent layer  190   a.    
     After the combination of the first and second substrates  100  and  200 , a process of burning the absorbent layer  190   a  is performed by irradiating a laser beam on the absorbent layer  190   a  overlapped with the outer edges of the sealants  160 , as shown in  FIG. 4A . At this time, the laser beam is irradiated to focus on the absorbent layer  190   a  in order to prevent a direct irradiation of the laser beam for the sealants  160 . As such, leakage of the sealants  160  can be minimized. The laser used the burning process comprises one of a gas type laser, liquid type laser, solid-state type laser, and plasma x-ray laser. The gas laser comprises He-Ne laser, CO2 laser, and Excimer laser. The liquid type laser comprises Dye laser and the solid-state laser comprises Ruby laser, Nd:YAG laser, Nd:YLF laser, Nd:glass laser, and Ti:sapphire laser. 
     The absorbent layer  190   a  is formed from a black resin-based material with a wide absorptive range of laser wavelengths. As such, the absorbent layer  190   a  can easily absorb the laser beam even though a low energy laser beam is irradiated. In accordance therewith, the absorbent layer  190   a  can be easily burnt by a low energy laser beam. 
     Alternatively, the absorbent layer  190   a  can be formed from the same as one of the red, green and blue pigments, which are used to form the color filters  180  on the second substrate  200 , instead of the same material as the black matrix  190 . The red, green and blue pigments can easily absorb the low energy laser beam because they have a wider absorptive range of laser wavelengths compared to the sealant  160 . 
     Thereafter, a first cutting process using a scriber  240  is perfoimed for the second substrate  200  with the absorbent layer  190   a  which is burnt by the laser beam, as shown in  FIG. 4B . The first cutting process using the scriber  240  allows the burnt absorbent layer  190   a  and a part of the second substrate  200  with the burnt absorbent layer  190   a  to be removed. 
     Subsequently, the residual of the absorbent layer  190   a  remaining at the outer edge of each sealant  160  is removed through a brushing process. Therefore, the outer edges of the sealants  160  are externally exposed. 
     As described above, since the absorbent layer  190   a  formed to face the outer edges of the sealants  160  has a wide absorptive range of laser wavelengths compared to the sealant  160 , the absorbent layer  190   a  can easily absorb a low energy laser beam and is easy to burn when the low energy laser beam is irradiated. 
     The LCD device fabrication method of the present embodiment allows the burning process to be performed in a state that the absorbent layer  190   a  easily absorbing the low energy laser beam overlaps with a part of the sealant  160 . As such, the LCD device fabrication method can minimize leakage of the sealants  160  unlike that of the related art which must use a high energy laser beam able to burn the sealants  160 . 
     The absorbent layer  190   a  functions as a shielding portion which prevents the effect of the laser beam directly applied to the sealants  160 . In other words, the laser beam is not irradiated directly to the sealants  160 . Therefore, leakage of the sealants  160  can be minimized. 
     The minimized leakage of the sealants  160  allows the deterioration of the adhesive strength of the sealant  160  to be minimized. Also, an applying quantity of energy can be minimized, and furthermore a process margin can be secured. 
     After the brushing process, the first and second substrates  100  and  200  can be simultaneously cut through a second cutting process using a scriber. At this time, the simultaneous cutting of the first and second substrates  100  and  200  can be easily performed because the externally exposed outer edge of the sealant  160  is in a lightly cured state compared to the rest of the sealant  160 . This results from the fact that only the externally exposed outer edge of the sealant  160  had been shielded by the absorbent layer  190   a  at the irradiation of UV light. 
     The ordinary skilled person in the art should understand that various changes or modifications of the present disclosure are possible without departing from the technical spirit or the essential features of the present disclosure. As such, it should be understood by the ordinary skilled person in the art that the above-mentioned embodiments are provided as examples of the present disclosure, but the present disclosure is not limited these embodiments. Accordingly, the scope of the present disclosure shall be determined only by the appended claims and their equivalents. Moreover, it should be considered that alternative uses derived from the meaning, scope and their equivalent concepts defined in the claims are included in the scope of the present disclosure.