Abstract:
A liquid crystal display panel is disclosed. The liquid crystal display panel includes: a first substrate with a conductive layer formed on one surface thereof; a color filter layer including a plurality of color filters formed on the conductive layer; a conductive light shielding layer formed between the plurality of color filters; a second substrate with a pixel array formed on one surface thereof; and a liquid crystal layer filled between the conductive light shielding layer and the pixel array, wherein the conductive layer is electrically short-circuited with the pixel array. Since a voltage is applied to the conductive layer formed on the front surface of the first substrate, liquid crystal molecules of the liquid crystal layer between the conductive layer and the pixel array can be prevented from being vertically aligned, thus improving liquid crystal efficiency.

Description:
CLAIM OF PRIORITY 
     This application claims priority to and the benefit of Korean Patent Application No. 10-2010-0001979 filed in the Korean Intellectual Property Office on Jan. 8, 2010, the entire contents of which are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a liquid crystal display panel and manufacturing method thereof, and more particularly, to a liquid crystal display panel that is capable of preventing a vertical field due to static electricity with a simple configuration by positioning ITO within a color filter and applying an internal voltage and a threshold voltage, and a manufacturing method thereof. 
     2. Description of the Related Art 
     In general, a liquid crystal display (LCD) displays an image corresponding to a video signal on a liquid crystal display panel, on which liquid crystal cells are arranged in a matrix form, by adjusting light transmittance of the liquid crystal cells according to the video signal. To this end, the LCD includes the liquid crystal display panel including liquid crystal cells arranged in an active matrix form, and driving circuits for driving the liquid crystal display panel. 
     The LCD is classified into a twisted nematic (TN) mode LCD using a vertical field, and an in-plane switch (IPS) mode LCD using a horizontal field (or an in-plane field) depending on the direction of the electric field for driving liquid crystal molecules. 
     The TN mode LCD, in which liquid crystal molecules of a liquid crystal display panel are driven by a vertical field formed between pixel electrodes and a common electrode disposed to face each other on an upper substrate, advantageously has a large aperture ratio but disadvantageously has a small viewing angle. 
     The IPS mode LCD, in which liquid crystal molecules of a liquid crystal display panel are driven by a horizontal field between pixel electrodes and a common electrode disposed in parallel to each other on a lower substrate, advantageously has a large viewing angle but disadvantageously has a small aperture ratio. 
     Meanwhile, in the TN mode LCD, the liquid crystal molecules of the liquid crystal display panel are driven by a vertical field between a color filter array substrate and a thin film transistor (TFT) array substrate, allowing for the formation of an equal potential loop between the color filter array substrate and the TFT array substrate, so even a small amount of static electricity that is generated can be easily discharged compared with the IPS mode LCD. 
     In comparison, in the IPS mode LCD, because the liquid crystal molecules of the liquid crystal display panel are driven by a horizontal field, the color filter array substrate is electrically isolated, making it difficult to discharge static electricity. In an effort to solve the problem of the generation of static electricity, in the IPS mode LCD, a transparent metal layer is formed on a rear surface of the color filter array substrate of the liquid crystal panel to externally discharge static electricity. 
     However, in the related art LCD, because the transparent metal layer is formed at the outer side of the liquid crystal display panel, a problem arises in that an etching process for making the liquid crystal display panel thinner cannot be performed. 
     Namely, in general, after the formation of the liquid crystal display panel, the upper and lower substrates are partially etched through a wet etching process to reduce the thickness of the liquid crystal display panel. In this case, however, when forming the transparent metal layer at the outer side of the liquid crystal display panel, the process of making the liquid crystal display panel thinner, which includes a dipping process with an etching solution, cannot be performed. 
     The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art. 
     SUMMARY OF THE INVENTION 
     The present invention has been made in an effort to provide a liquid crystal display panel having an advantage of basically removing a vertical field due to static electricity. 
     The present invention has been also made in an effort to provide a liquid crystal display panel having an advantage of simplifying a manufacturing process to thus improve productivity and reduce cost. 
     An exemplary embodiment of the present invention provides a liquid crystal display panel including: a first substrate with a conductive layer formed on one surface thereof; a color filter layer including a plurality of color filters formed on the conductive layer; a conductive light shielding layer formed between the plurality of color filters; a second substrate with a pixel array formed on one surface thereof; and a liquid crystal layer filled between the conductive light shielding layer and the pixel array, wherein the conductive layer is electrically short-circuited with the pixel array. 
     The pixel array may include a thin film transistor (TFT), a pixel electrode, and a common electrode. 
     The liquid crystal display panel may further include an overcoat layer formed at a lower portion of the color filter layer. 
     A certain voltage may be applied to the conductive layer, and the difference between the voltage applied to the conductive layer and a voltage applied to the pixel array may be smaller than a threshold voltage that does not allow liquid crystal molecules of the liquid crystal layer to be vertically aligned. The conductive light shielding layer may contain a chromium (Cr) component. 
     The conductive layer may or may not have a pattern. 
     Voltage application wiring may be formed on the second substrate in order to apply a voltage to the conductive layer of the first substrate, and the voltage application wiring may be formed to be electrically short-circuited with wiring of is the pixel array. 
     A conductive connection part may be formed between the first and second substrates in order to electrically connect the voltage application wiring and the conductive layer. 
     The conductive connection part may include a sealing portion. 
     Another embodiment of the present invention provides a method for forming a liquid crystal display panel, including: providing a first substrate with a conductive layer formed on a front surface thereof; providing a second substrate with voltage application wiring formed thereon to apply a voltage to the conductive layer of the first substrate; attaching the first and second substrates; electrically connecting the conductive layer of the first substrate and the voltage application wiring of the second substrate; forming a liquid crystal layer between the first and second substrates; and applying a voltage to the conductive layer of the first substrate. 
     The providing of the first substrate may include forming a conductive layer on a front surface of the first substrate, forming a metal black matrix at an upper portion of the conductive layer, and forming a color filter layer on the metal black matrix. 
     The electrically connecting of the conductive layer of the first substrate and the voltage application wiring of the second substrate may include forming a conductive connection part between the first and second substrates. 
     The providing of the second substrate may include forming a pixel array on the second substrate. 
     The pixel array may be formed to be electrically short-circuited with the conductive layer. 
     The difference between a voltage applied to the conductive layer and a voltage applied to the pixel array may be smaller than a threshold voltage that does not allow liquid crystal molecules of the liquid crystal layer to be vertically aligned. 
     According to an exemplary embodiment of the present invention, because the conductive layer is formed on the front surface of the first substrate to remove static electricity, static electricity of the liquid crystal display panel can be prevented with a simple structure. 
     According to an exemplary embodiment of the present invention, because a certain voltage is applied to the conductive layer formed on the front surface of the first substrate, liquid crystal molecules of the liquid crystal layer between the conductive layer and the pixel array can be prevented from being vertically aligned, thus improving liquid crystal efficiency. 
     In the method of forming a liquid crystal display panel according to an exemplary embodiment of the present invention, because such a process of forming a conductive layer on a rear surface of the first substrate and grounding it from the exterior as in the related art is omitted, the manufacturing process of the liquid crystal display panel can be simplified and the productivity can be improved to lead to a reduction in production cost. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional view of a liquid crystal display panel according to an exemplary embodiment of the present invention. 
         FIG. 2  is a top plan view showing a wiring structure on a second substrate of the liquid crystal display panel according to an exemplary embodiment of the present invention. 
         FIG. 3  is a cross-sectional view showing the difference of voltages formed between ITO and a pixel array in the liquid crystal display panel according to an exemplary embodiment of the present invention. 
         FIG. 4  is a flowchart illustrating the process of manufacturing a liquid crystal display panel according to an exemplary embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     The present invention will be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. In describing the present invention, a configuration required for understanding the technical ideas of the present invention will be mainly described, and a description of a configuration departing from the ideas of the present invention will be omitted. However, a skilled person in the art to which the present invention pertains will understand the technical scope of the ideas of the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. The drawings and description are to be regarded as illustrative in nature and not restrictive. Like reference numerals designate like elements throughout the specification. 
       FIG. 1  is a cross-sectional view of a liquid crystal display panel according to an exemplary embodiment of the present invention, and  FIG. 2  is a top plan view showing a wiring structure on a second substrate of the liquid crystal display panel according to an exemplary embodiment of the present invention.  FIG. 3  illustrates a state in which liquid crystal molecules of a liquid crystal layer are horizontally or vertically aligned according to a voltage supplied to a pixel array of the second substrate and a conductive layer of a first substrate. 
     With reference to  FIGS. 1 and 2 , a liquid crystal display panel  100  is according to an exemplary embodiment of the present invention includes a first substrate  102 , a conductive layer  104 , a color filter layer  106 , a conductive light shielding layer  116 , a liquid crystal layer  110 , a conductive connection part  120 , and a second substrate  114 . 
     The conductive layer  104  is formed on one surface of the first substrate  102 . In this case, according to the present exemplary embodiment, the one surface of the first substrate  102  where the conductive layer  104  is formed faces the second substrate  114 , which will be defined as a front surface of the first substrate  102  in the present exemplary embodiment. 
     The conductive layer  104  does not have a pattern. 
     When the conductive layer  104  is formed on one surface of the first substrate  102 , it may be made of a transparent conductive metal such as indium tin oxide (ITO) or indium zinc oxide (IZO) having good light transmittance, or may be made of a transparent conductive resin. Here, the transparent conductive resin may be made of a mixture of ITO powder and an acryl, an epoxy, or the like. According to an exemplary embodiment of the present invention, the conductive layer  104  is formed at the interior of the liquid crystal display panel to discharge static electricity. 
     The conductive light shielding layer (or black matrix)  116  serves to absorb external light as well as prevent light leakage to thus increase the contrast. According to an exemplary embodiment of the present invention, the conductive light shielding layer  116  is formed to include a metal material, and in this case, the metal material may include chromium (Cr). 
     In the liquid crystal display panel according to the present exemplary embodiment, because the conductive layer  104  is connected by voltage application wiring  118  and the conductive connection part  120  formed on the second substrate  114  in order to discharge electrical charges from the conductive layer  104  disposed on the front surface of the first substrate  102 , preferably, the light shielding layer  116  positioned between the conductive layer  104  and the conductive connection part  120  is formed to have conductivity. 
     Conductive light shielding layers  116  are formed at certain intervals on an upper portion of the conductive layer of the first substrate such that they overlap with a pixel array area, gate lines, and data lines of the second substrate  114 . Also, the light shielding layers  116  demarcate red, green, and blue color filter layers  106 R,  106 G, and  106 B formed on the light shielding layers  116 . 
     The red, green, and blue color filter layers  106 R,  106 G, and  106 B are formed to be alternately arranged between the conductive light shielding layers  116 . Such color filter layers  106  may be made of a photosensitive organic material. 
     Meanwhile, in order to improve smoothness by removing a step generated due to the presence of the color filter layers  106 , an overcoat layer  108  may be selectively formed. 
     A pixel array  112  including pixel electrodes and a transparent common electrode is formed on one surface of the second substrate  114 . 
     Although not shown, each pixel area is defined by gate lines and data lines formed to cross each other in the pixel array  112 . 
     A switching element is disposed at each crossing point of the gate lines and data lines. The pixel electrodes and transparent common electrode of the pixel array are separately disposed such that they overlap by a certain area with an insulating layer interposed therebetween, and are formed within a pixel area to adjust light transmittance by applying a voltage to the liquid crystal layer (LC)  110 . 
     In an exemplary embodiment of the present invention, it is configured such that a reference voltage V 2  is applied to the pixel array  112  from a certain voltage source. In this case, the reference voltage may be approximately 5V. 
     The conductive connection part  120  is formed between the first substrate  102  and the second substrate  114 . 
     In more detail, at the first substrate  102  side, the conductive connection part  120  is electrically connected with the conductive layer  104  via the conductive light shielding layer  116 , and at the second substrate  114  side, the conductive connection part  120  is electrically connected with the voltage application wiring  118  that supplies a voltage to the conductive layer  104  formed on the second substrate  114 . 
     Meanwhile, according to an exemplary embodiment of the present invention, the conductive connection part  120  may be made of a sealing material. 
     Thus, in the liquid crystal display panel  100  according to the present exemplary embodiment, when static electricity is generated from the rear surface, namely, the upper surface, of the first substrate  102 , positive (+) charges are arranged on the upper surface of the first substrate  102  and negative (−) charges are arranged on the conductive layer  104  positioned on the front surface of the first substrate  1 , and then the negative (−) charges formed on the conductive layer  104  are externally discharged from the lower portion of the first substrate  102  through the conductive connection part  120 . Accordingly, generation of static electricity from the surface of the liquid crystal display panel can be prevented. 
     As a result, in the liquid crystal display panel  100  according to the present exemplary embodiment, static electricity formed on the first substrate  102  can be eliminated without having to additionally form the conductive layer  104  on the rear surface of the first substrate  102  for external grounding. 
     Meanwhile, with reference to  FIG. 2 , according to an exemplary embodiment of the present invention, the voltage application wiring  118  that supplies a voltage to the conductive layer  104  positioned on the front surface of the first substrate  1  is formed on the second substrate  114  such that it is electrically short-circuited with driving wiring  119  of the pixel array  112  on the second substrate  114 . 
     Also, it is configured such that a voltage V 1  from a certain voltage source  130  is supplied to the conductive layer  104  of the first substrate  102 , which is electrically short-circuited with the driving wiring  119  of the pixel array  112 . 
     Thus, in the liquid crystal display panel  100  according to an exemplary embodiment of the present invention, the voltage V 1  is supplied to the conductive layer  104  formed on the first substrate  102 , and the voltage V 2  is supplied to the pixel array  112  of the second substrate  114 . 
     Accordingly, with reference to  FIG. 3 , there is a voltage difference of V 2 -V 1  formed between the conductive layer  104  and the pixel array  112  of the second substrate  114 . For example, when the voltage V 1  applied to the conductive layer  104  is 1.5V and the voltage V 2  applied to the pixel array  112  is 5V, a voltage difference in a vertical field formed at the liquid crystal layer  110  is 3.5V. If the voltage difference in the vertical field is large enough to vertically align liquid crystal molecules  111  of the liquid crystal layer  110 , the liquid crystal molecules  111  of the liquid crystal layer  110  would be vertically aligned to liquid crystal molecules  111 ′ indicated by a dotted line in  FIG. 3 . If the liquid crystal molecules  111  are aligned in the vertical direction in that way, transmittance is reduced to degrade the efficiency of the liquid crystal layer  110 . 
     Thus, in the present exemplary embodiment, preferably, the voltage difference V 2 -V 1  generated between the conductive layer  104  and the pixel array  112  is large enough to form a vertical field in the vertical direction at the liquid crystal layer  110  when viewed in  FIG. 3 , but within a range that does not allow the liquid crystal molecules to be aligned vertically. Thus, because the voltage difference between the conductive layer  104  and the pixel array  112  is within such a suitable range, the liquid crystal efficiency of the liquid crystal display panel  100  can be improved. 
     In more detail, Table 1 below shows the results of experimentation made by the applicant of the present invention. As noted in Table 1, compared with the related art liquid crystal display panel including a conductive layer (ITO) formed on a rear surface of a first substrate, when a conductive layer was formed on the front surface of the first substrate but only grounding was made, the liquid crystal efficiency was 57.32% in the case of L64 (when luminance is white), which is lower than the liquid crystal efficiency of 60.88% when the conductive layer is formed on the rear surface. Comparatively, in the exemplary embodiment of the present invention, when the conductive layer was formed on the front surface and 1.5V was applied, the liquid crystal efficiency was 60.44%, which is similar to the case where the conductive layer is formed on the rear surface. 
     
       
         
               
               
               
               
             
               
               
               
               
             
           
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                   
                 Front ITO 
                   
               
               
                   
                 Normal 
                 structure 
                 Front ITO 
               
               
                   
                 (rear surface ITO) 
                 (GND) 
                 (1.5 V) 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                 Liquid crystal efficiency (LO) 
                    0% 
                    0% 
                    0% 
               
               
                 Liquid crystal efficiency L32 
                 18.78% 
                  18.6% 
                 18.84% 
               
               
                 Liquid crystal efficiency L64 
                 60.88% 
                 57.32% 
                 60.44% 
               
               
                   
               
             
          
         
       
     
     That is, in the liquid crystal display panel  100  according to an exemplary embodiment of the present invention, a certain voltage is applied to the conductive layer  104  such that the liquid crystal efficiency is not degraded when the liquid crystal molecules  111  of the liquid crystal layer  110  are vertically aligned due to the voltage difference between the conductive layer  104  formed on the front surface of the first substrate  102  and the pixel array  112  formed on the second substrate  114 , and in this case, the voltage difference between the conductive layer  104  and the pixel array  112  does not exceed the threshold voltage, namely, a minimum voltage required for the vertical field applied to the liquid crystal layer  110  to vertically align the liquid crystal molecules  111 , thereby preventing degradation of the liquid crystal efficiency of the liquid crystal display panel  100 . 
     A method for forming the liquid crystal display panel  100  configured as described above will now be described. 
       FIG. 4  is a flowchart illustrating the process of manufacturing a liquid crystal display panel according to an exemplary embodiment of the present invention. 
     With reference to  FIG. 4 , first, the first substrate is provided (S 301 ), and the conductive layer is formed with a transparent metal material on the front surface of the first substrate through a deposition process such as sputtering or the like (S 302 ). 
     The transparent metal material may include indium tin oxide (ITO), tin oxide (TO), indium zinc oxide (IZO), indium tin zinc oxide (ITZO), and the like. 
     Next, the conductive light shielding layer including a metal material such as chromium (Cr) is formed on the conductive layer (S 303 ). In this case, the conductive to light shielding layer may be formed by depositing a chromium oxide (CrOx) film on the first substrate and then performing photoresist and etching processes thereon. 
     Then, a red resin is deposited on the first substrate with the conductive light shielding layer formed thereon, on which a photolithography process using a mask, an etching process, and a baking process for hardening are performed to pattern the red resin to form a red color filter (R). Thereafter, a green color filter and a blue color filter are formed on the upper substrate  102  with the red color filter (R) formed thereon, in the same manner, to form RGB color filter layers (S 304 ). 
     An overcoat material is then deposited on the entire surface of the first substrate with the RGB color filters formed thereon to form the overcoat layer. 
     The second substrate is provided through a process separately performed from the process of providing the first substrate (S 305 ). At this time, a thin film pattern including a thin film transistor (TFT), a gate line, a data line, a common electrode, a pixel electrode, and the like, is formed at a portion (i.e., a display area) of the second substrate. 
     Meanwhile, in the process of forming the thin film pattern of the second substrate, a wiring pattern for applying a voltage to the conductive layer of the first substrate is formed (S 306 ). In this case, the wiring pattern is electrically short-circuited with the wiring of the pixel array to which a driving voltage is applied. 
     Thereafter, the first and second substrates are attached (S 307 ). The process of attaching the first and second substrates includes a process of forming a sealing layer along the circumference of the first and second substrates in order to allow the liquid crystal layer to be formed between the first and second substrates. 
     In this case, in the process of attaching the first and second substrates, the conductive layer of the first substrate and the voltage application wiring of the second substrate are electrically connected (S 308 ). To this end, the conductive connection part is formed between the first and second substrates. 
     Subsequently, liquid crystal is injected between the first and second substrates to form the liquid crystal layer (S 309 ). 
     After the formation of the liquid crystal layer is completed, a certain voltage V 1  that is different from the voltage V 2  applied to the pixel array is applied to the conductive layer (S 310 ). In this case, a driving source for driving the liquid crystal display panel may be used as a voltage source for applying the voltage to the conductive layer. 
     In this case, as described above, as for the voltage applied to the conductive layer from the voltage source, a voltage difference between the voltage applied to the conductive layer and the voltage applied to the pixel array is adjusted to be smaller than the threshold voltage that does not allow the liquid crystal molecules of the liquid crystal layer to be vertically aligned. 
     The configuration of the liquid crystal display panel according to the present exemplary embodiment can be applied to a fringe-field switching (FFS) mode and a plane to line switching (PLS) mode as well as to the in-plane switching (IPS) mode. 
     While this invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. 
     &lt;Description of Symbols&gt; 
     
       
         
               
               
               
               
             
           
               
                   
               
             
             
               
                 100 
                 liquid crystal display panel 
                 102 
                 first substrate 
               
               
                 104 
                 conductive layer 
                 106 
                 color filter 
               
               
                 108 
                 overcoat layer 
                 110 
                 liquid crystal layer 
               
               
                 111 
                 liquid crystal molecules 
                 112 
                 pixel array 
               
               
                 114 
                 second substrate 
                 116 
                 black matrix 
               
               
                 118 
                 ITO voltage application wiring 
                 119 
                 pixel array wiring 
               
               
                 120 
                 conductive connection part 
                 130 
                 ITO voltage source