Abstract:
A mother glass panel for manufacturing a plurality of liquid crystal displays (LCD) includes a first substrate; a second substrate attached to the first substrate, wherein column spacers are disposed between the first and second substrates to form cell gaps; and a liquid crystal layer interposed between the first substrate and the second substrate, wherein, the mother glass panel defines a plurality of liquid crystal display regions and at least two of the liquid crystal display regions have different cell gaps.

Description:
[0001]     This application claims the benefit of Korean Application No. 046140/2005 filed in Korea on May 31, 2005, which is hereby incorporated by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a liquid crystal display device (LCD), and more particularly, to an LCD capable of securing a wide viewing angle by forming a plurality of liquid crystal cells having different liquid crystal cell sizes and different cell gaps over one mother glass.  
         [0004]     2. Description of the Related Art  
         [0005]     Traditionally, a cathode ray tube (CRT) has been used as an information display device because of advantageous characteristics such as better image quality on a screen and lower price. However, due to the poor portability of the CRT because of its size and weight, liquid crystal display devices (LCDs) have been actively developed in recent years. The LCD devices meet the demand of lightweight and miniaturized size. Furthermore, the LCD devices include more powerful performances, for example, micronization and low power consumption or the like, to overcome the disadvantages of the CRT. Thus, the LCD devices gained popularly as the mainstream information processing apparatuses of today.  
         [0006]     The LCD includes a thin film transistor (TFT) and a pixel electrode formed on a substrate (i.e., TFT substrate), and a color filter substrate where a red, a green, and a blue color filters are formed. The TFT acts as a switching device. The LCD further includes a liquid crystal film interposed between the TFT substrate and the color filter substrate, thereafter two substrates are attached to each other. A plurality of liquid crystal cells having the same cell region are formed over a mother glass. In addition, a multi mode on glass (MMG) model LCD has been developed, in which the liquid crystal cells having different sizes are formed on the single mother glass.  
         [0007]      FIG. 1  is a schematic view illustrating a related art MMG model LCD. As shown in  FIG. 1 , liquid crystal cells having cell regions I and II with different sizes are formed on a mother glass  10 . The two substrates, the TFT substrate and the color filter substrate, are attached to each other in these regions. A first cell region I includes a large-sized liquid crystal cell having a size of 20 inches or more, whereas a second cell II includes a smaller-sized liquid crystal cell having a size of 15 inches or less. Since the liquid crystal cells having the cell regions I and II are formed simultaneously over one mother glass  10  in the MMG model, the liquid crystal panels of various sizes may be manufactured through one process. In  FIG. 1 , each capital letter H in the liquid crystal cells denotes the cell gap and it is understood that all of the liquid crystal cells have the same cell gap H regardless of the cell size according to the related art MMG model LCD.  
         [0008]      FIG. 2A  is a schematic view illustrating a location where a column spacer is formed in a pixel region according to the related art MMG model LCD.  FIG. 2B  is a cross-sectional view taken along line III-III′ of  FIG. 2A . As shown in  FIG. 2A , a gate line  21  is arranged in a horizontal direction crossing a data line  23  to define the pixel region, and a pixel electrode  29  is arranged in the pixel region. In addition, a TFT (i.e., a switching device) is formed at an intersection of the gate line  21  and the data line  23 .  
         [0009]     A column spacer  25  is formed over the gate line  21  to maintain a predetermined cell gap, or alternatively positioned over the gate line  21  to maintain the predetermined cell gap when attaching the color filter substrate to the TFT substrate. The column spacer  25  may be formed by patterning, on the TFT substrate or the color filter substrate. The region where the column spacer  25  is formed or positioned over the gate line  21  is a blocking region.  
         [0010]     As shown in  FIG. 2B , the gate line  21 , a gate insulating layer  12  and a passivation layer  9  are formed over a first insulating substrate  11   b  in sequence. A reference numeral  29  denotes a pixel electrode. Over the column spacer  25 , a color filter substrate including a black matrix  4 , a color filter layer  5  and a common electrode  6  is formed over a second insulating substrate  11   a . The column spacer  25  is placed over the gate line  21  (i.e., the blocking region of the TFT substrate) and under the black matrix  4  (i.e., the blocking region of the color filter substrate) to maintain the cell gap between the two insulating substrates  11   a  and  11   b.    
         [0011]      FIG. 3  is a cross-sectional view illustrating the cell gap of two liquid crystal cells in the related art MMG model LCD. Referring to  FIG. 3 , when the column spacer  25  is formed in a predetermined shape as illustrated in  FIGS. 2A and 2B , the height of cell gap in the first cell region I and II are equal. Accordingly, when the liquid crystal cells having different sizes from one another are formed as in the related art MMG model, the liquid crystal panels with various sizes may be manufactured through single process.  
         [0012]     However, as illustrated in  FIG. 3 , since the cell gaps of the all liquid crystal cells are identically formed regardless of resolution or size of each cell, it is difficult to manufacture the LCD having various viewing angles. For example, after cutting the liquid crystal cells from the related art MMG model mother glass, a wide view polarizer must be attached to secure a wide viewing angle. Thus, the wide view polarizer plays a major role in securing the wide viewing angle that corresponds to a retardation value And of the liquid crystal cell.  
         [0013]     However, if all the liquid crystal cells having different resolution and sizes are formed such that they have the same cell gap regardless of the cell size or the like, all the retardation values become equal to one another. As a result, all the liquid crystal cells have the same viewing angle regardless of their size or the like. Therefore, various-sized liquid crystal cells cannot be formed using one glass substrate to secure an optimized viewing angle in each liquid crystal cell.  
       SUMMARY OF THE INVENTION  
       [0014]     Accordingly, the present invention is directed to a liquid crystal display (LCD) and a method for manufacturing the same that substantially obviate one or more problems due to limitations and disadvantages of the related art.  
         [0015]     An object of the present invention is to provide an MMG model LCD capable of forming liquid crystal cells having various viewing angles by forming different cell gaps in appropriate liquid crystal cells, where the liquid crystal cells have the different sizes from one another.  
         [0016]     Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.  
         [0017]     To achieve these objects and other advantages and in accordance with the purpose of the invention, as embodied and broadly described, a liquid crystal display device and method for manufacturing the same includes a mother glass panel for manufacturing a plurality of liquid crystal displays (LCD) includes a first substrate; a second substrate attached to the first substrate, wherein column spacers are disposed between the first and second substrates to form cell gaps; and a liquid crystal layer interposed between the first substrate and the second substrate, wherein, the mother glass panel defines a plurality of liquid crystal display regions and at least two of the liquid crystal display regions have different cell gaps.  
         [0018]     In another aspect, a method for manufacturing a plurality of liquid crystal display includes forming gate lines, data lines and thin film transistors on a first insulating substrate, wherein the thin film transistors are formed at intersections of the gate lines and the data lines; forming pixel electrodes in pixel regions, wherein the pixel regions are defined by intersections of the gate and data lines; disposing column spacers on the first or a second insulating substrates to form cell gaps; attaching the first insulating substrate and the second insulating substrate; and cutting the attached substrates to form the plurality of liquid crystal displays, wherein at least two of the liquid crystal displays have different cell gaps.  
         [0019]     In another aspect, a mother glass panel for manufacturing a plurality of liquid crystal displays (LCD) includes a first insulating substrate; data lines, gate lines, thin film transistors and pixel electrodes on a second insulating substrate; at least one first hole defined through portions of the gate lines; at least one second hole defined through portions of a passivation layer, a gate insulating layer and portions of the gate lines; column spacers disposed on the first or second insulating substrates, wherein at least one column spacer is disposed within the first hole forming a first cell gap, at least another column spacer is disposed within the second hole forming a second cell gap, and at least another column spacer is disposed over the data line forming a third cell gap; and a liquid crystal layer interposed between the first and second insulating substrates.  
         [0020]     In another aspect, a method for manufacturing an LCD includes forming a gate line and a gate electrode on an insulating substrate; forming a hole through the gate line and a column spacer in the hole to form a cell gap; forming a gate insulating layer and an active layer on the insulating substrate where the gate electrode is formed, the active layer including a channel layer and an ohmic contact layer; forming source and drain electrodes and a data line on the insulating substrate where the active layer is formed; forming a passivation layer on the insulating substrate where the source and drain electrodes are formed, wherein a contact hole is formed through the passivation layer on the drain electrode; forming a pixel electrode by forming a transparent metal on the insulating layer where the passivation layer is formed and within the contact hole; attaching the insulating substrate to a second substrate; and interposing a liquid crystal layer between the insulating substrate and the second substrate.  
         [0021]     In another aspect, a method for manufacturing an LCD includes forming a gate line and a gate electrode on an insulating substrate; forming a gate insulating layer and an active layer on the insulating substrate where the gate electrode is formed, the active layer including a channel layer and an ohmic contact layer; forming source and drain electrodes and a data line on the insulating substrate where the active layer is formed; forming a column spacer over the data line to form a cell gap; forming a passivation layer on the insulating substrate where the source and drain electrodes are formed, wherein a contact hole is formed through the passivation layer on the drain electrode; attaching the insulating substrate to a second substrate; and interposing a liquid crystal layer between the insulating substrate and the second substrate.  
         [0022]     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0023]     The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiments of the invention and together with the description serve to explain the principle of the invention. In the drawings:  
         [0024]      FIG. 1 a  schematic view illustrating a related art MMG model LCD;  
         [0025]      FIG. 2A  is a schematic view illustrating a location where a column spacer is formed in a unit pixel region according to the related art;  
         [0026]      FIG. 2B  is a cross-sectional view taken along line III-III′ of  FIG. 2A ;  
         [0027]      FIG. 3  is a cross-sectional view illustrating a cell gap of two liquid crystal cells in a related art MMG model LCD;  
         [0028]      FIG. 4  is a schematic view illustrating a location where a column spacer is formed in a unit pixel region according to a first exemplary embodiment of the present invention;  
         [0029]      FIG. 5A  is a cross-sectional view taken along line IV-IV′ of  FIG. 4 ;  
         [0030]      FIG. 5B  is a cross-sectional view taken along line V-V′ of  FIG. 4 ;  
         [0031]      FIG. 6  is a cross-sectional view taken along line IV-IV′ of  FIG. 4  according to a second exemplary embodiment of the present invention;  
         [0032]      FIG. 7  is a cross-sectional view illustrating different cell gaps of liquid crystal cells in the MMG model LCD according to the second exemplary embodiment of the present invention;  
         [0033]      FIGS. 8A  to  8 E are cross-sectional views illustrating a first exemplary fabricating method of the MMG model LCD taken along lines VI-VI′ and IV-IV′ of  FIG. 4 ; and  
         [0034]      FIG. 9  is a cross-sectional view illustrating a second exemplary fabricating method of the MMG model LCD according to the second exemplary embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0035]     Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings.  
         [0036]      FIG. 4  is a schematic view illustrating a unit pixel region in a first exemplary MMG model liquid crystal cells according to the present invention. The MMG model liquid crystal cells are formed over a single glass substrate. In  FIG. 4 , a location where a column spacer is formed is indicated. In the unit pixel region, a gate line  121  is arranged in a horizontal direction to cross a data line  123 , and a pixel electrode  129  is arranged in the unit pixel region. In addition, a TFT (i.e., switching device) is formed at an intersection of the gate line  121  and the data line  123 . A column spacer  125  is formed over the gate line  121  and/or the data line  123  to maintain the cell gap. The column spacer  125  is formed by patterning, on a TFT substrate or a color filter substrate.  
         [0037]     In the first exemplary embodiment of the present invention, the column spacer  125  is positioned over the data line  123  or the gate line  121 . Thus, the liquid crystal cells can be manufactured having various cell gaps. As shown in  FIG. 4 , the column spacer  125  may be formed or positioned within a hole  126 . The hole  126  is defined through the gate line  121 . Alternatively, the column spacer  125  may be formed or positioned over the gate line  121 . In addition, the column spacer  125  may be formed or positioned over the data line  123 . Accordingly, if the column spacer  125  having the same height or thickness is formed or positioned over the gate line  121  or the data line  123 , thereafter the two substrates, the TFT substrate and the color filter substrate, are attached to each other, it is possible to form the liquid crystal cells having various cell gaps. As described above, the column spacer  125  is formed at different locations or the column spacer  125  is positioned differently when attaching the substrates to each other, thereby achieving the various cell gaps.  
         [0038]      FIGS. 5A and 5B  details the liquid crystal cells having different sizes and different cell gaps.  FIG. 5A  is a cross-sectional view taken along line IV-IV′ of  FIG. 4 , and  FIG. 5B  is a cross-sectional view taken along line V-V′ of  FIG. 4 . Referring to  FIGS. 5A and 5B , a TFT substrate  130   b  and a color filter substrate  130   a  are attached to each other forming a mother glass panel, wherein a column spacer  125  is positioned therebetween. The TFT substrate  130   b  includes a gate line  121 , a gate insulating layer  124  and a passivation layer  127  over a first insulating substrate  122   a . The color filter substrate  130   a  includes a black matrix  131 , a color filer layer  133  and a common electrode  135  formed over a second insulating substrate  122   b . The column spacer  125  is formed or positioned within the hole  126  to keep the first cell gap H 1  between the color filter substrate  130   a  and the TFT substrate  130   b.    
         [0039]     Whereas, in  FIG. 5B , the column spacer  125  is formed or positioned over the data line  123 , thereafter the TFT substrate  130   b  and the color filter substrate  130   a  are attached to each other. Since the column spacer  125  is formed or positioned over the data line  123 , the second cell gap H 2  becomes greater than the first cell gap H 1  of  FIG. 5A . In addition, though it is not shown in the drawings, when the column spacer  125  is formed or positioned over the gate line  121 , the cell gap formed by such placement may be different from the first cell gap H 1  and the second cell gap H 2 . Accordingly, the liquid crystal cells can be formed having various cell gaps by controlling the regions/locations where the column spacer  125  is formed/positioned over the TFT substrate  130   b  or over the color filter substrate  130   a  without modifying the height of the column spacer  125 .  
         [0040]      FIG. 6  is a cross-sectional view taken along line IV-IV′ of  FIG. 4  according to a second exemplary embodiment of the present invention. Referring to  FIG. 6 , when the column spacer  125  is formed or positioned over the first insulating substrate  122   a  within the hole  126 , a portion of the first insulating substrate  122   a  is exposed within the hole  126 . As shown in  FIG. 6 , the hole  126  is defined by etching a portion of the multiple layers including the gale line  121 , the gate insulating layer  124  and the passivation layer  127 . In addition, the hole  126  and a contact hole  150  are defined through the same etching process (refer to  FIGS. 8D, 8E  and  9  for the contact hole  150 ).  
         [0041]     The black matrix  131 , the color filter layer  133  and the common electrode  135  are formed over the second insulating substrate  122   b  in sequence, thereby forming the color filter substrate  130   a . Then, the column spacer  125  is formed over the color filter substrate  130   a  within the black matrix region  131 . The black matrix region  131  corresponds to the region where the hole  126  is defined when the two substrates are faced each other. After the column spacer  125  is formed over the color filter substrate  130   a , the TFT substrate  130   b  and the color filter substrate  130   a  are attached to form the mother glass panel. While attaching the two substrates, the column spacer  125  is positioned within the hole  126  of the TFT substrate  130   b . Therefore, a third cell gap H 3  shorter than the first cell gap H 1  if formed.  
         [0042]     As described above, although the column spacer  125  is formed equal in height or thickness to that of the related art, various cell gaps can be formed by controlling the locations where the column spacer  125  if formed, as illustrated in  FIGS. 5A, 5B  and  6 . While it is illustrated that the column spacer  125  is formed over the color filter substrate  130   a , it is possible to implement various cell gaps regardless of where on the color filter substrate, the column spacer  125  is formed.  
         [0043]      FIG. 7  is a cross-sectional view illustrating a cell gap in each liquid crystal cell according to the MMG model LCD (i.e., a mother glass panel) of the present invention. The liquid crystal cell region I includes liquid crystal cells having different cell gaps H 1  and H 2 , and the liquid crystal cell region II includes liquid crystal cells having different call gaps H 1 , H 2  and H 3 . The cell gaps, H 1  and H 2 , are formed in a similar manner as illustrated in  FIGS. 5A and 5B . Likewise, the cell gap H 3  is formed in a similar manner as illustrated in  FIG. 6 . As described above, the column spacer may be positioned at desired locations shown in  FIG. 5A, 5B  or  6  so that various cell gaps may be formed. Thus, when forming a plurality of liquid crystal cells having different sizes over a single mother glass, the cell gap of each liquid crystal cell can be adjusted by controlling the region where the column spacer is positioned.  
         [0044]      FIGS. 8A  to  8 E are cross-sectional views illustrating a first exemplary fabricating method of a MMG model LCD according to the first embodiment of the present invention. The cross-sectional views are taken along lines VI-VI′ and IV-IV′ of  FIG. 4 .  
         [0045]     As illustrated in  FIG. 8A , after depositing a metal layer on the first insulating substrate  122   a , the metal layer is etched by photolithography to form a gate electrode  121   a  in a TFT region VI-VI′ and a gate line  121  in a region IV-IV′. Simultaneously, the hole  126  where the column spacer will be formed or positioned is defined by etching the metal layer in the region IV-IV′.  
         [0046]     As shown in  FIG. 8B , a gate insulating layer  124  is deposited over the first insulating substrate  122   a  where the gate electrode  121   a  and the gate line  121  are formed. Subsequently, an amorphous silicon layer and a doped amorphous silicon layer are deposited over the first insulating substrate  122   a  in sequence. Then, the resultant is etched by photolithography to form an channel layer  128  and an ohmic contact layer  140  in the VI-VI′ region. In the IV-IV′ region, however, both the amorphous silicon layer and the doped amorphous silicon layer are removed to expose the gate insulating layer  124  over the gate line  121 .  
         [0047]     As shown in  FIG. 8C , after the active layer (the channel layer  128  and the ohmic contact layer  140 ) is formed, a metal layer is deposited over the first insulating substrate  122   a . Then, the metal layer is etched to form a source electrode  141   a , a drain electrode  141   b , and the data line  123  in the VI-VI′ region. The data line  123  is formed extending from the source electrode  141   a . In the IV-IV′ region, however, the metal layer is entirely etched so that the gate insulating layer  124  is exposed. Next, as shown in  FIG. 8D , after forming the source and the drain electrodes  141   a  and  141   b , a passivation layer  127  is deposited over the first insulating substrate  122   a . Thereafter, a contact hole  150  is defined through the passivation layer  127  to expose a portion of the drain electrode  141   b . The passivation layer  127  deposited over the gate insulating layer  124  in the IV-IV′ region remains. Then, as shown in  FIG. 8E , after completing the contact hole  150  formation process, the transparent metal layer is deposited over the first insulating substrate  122   a  and etched to form a pixel electrode  129  in the VI-VI′ region.  
         [0048]     When attaching the TFT substrate (formed through the above described fabricating processes) to the color filter substrate, the cell gap between the color filter substrate and the TFT substrate may be controlled by the hole  126  upon formation of the column spacer  125  within the hole  126 . More precisely, the cell gap may be reduced to the thickness of the gate line  121  when the hole  126  is used. Accordingly, when the color filter substrate is attached to the TFT substrate having the column spacer positioned within the hole  126  as shown in  FIG. 8E , the cell gap becomes the first cell gap of H 1 .  
         [0049]      FIG. 9  is a cross-sectional view illustrating a second exemplary fabricating method of MMG model LCD according to the second embodiment of the present invention. As illustrated in  FIG. 9 , the hole  126  in the IV-IV′ region is defined by etching a portion of the gate line  121 , the gate insulating layer  124 , and the passivation layer  127  completely. Simultaneously, the contact hole  150  is defined in the VI-VI′ region. The hole  126  exposes the first insulating substrate  122   a . Accordingly, unlike the TFT substrate as shown in  FIG. 8E , since the column spacer will be placed over the first insulating substrate  122   a , the cell gap is reduced even more in spite of employing the same sized column spacer  125 . The cell gap formed by attaching the TFT substrate of  FIG. 9  and the color filter substrate becomes the third cell gap H 3 .  
         [0050]     In addition, when the column spacer  125  is positioned or formed over the data line  123 , the cell gap of H 2  as illustrated in  FIG. 5B  may be achieved using both the first and second exemplary MMG model TFT substrates of the present invention. As a result, the hole  126  can be formed in the various locations where the column spacer will be formed or positioned, without changing the height of the column spacer  125 , thus securing the various viewing angles.  
         [0051]     Therefore, the MMG model LCD according to the exemplary embodiments of the present invention, the liquid crystal cells are fabricated having various cell gaps and sizes. Accordingly, various viewing angles corresponding to the wide view polarizer can be obtained. Specifically, as shown in  FIGS. 5A and 8A  to  8 E, the column spacer may be formed or positioned within the hole  126  to obtain the first cell gap H 1 . Furthermore, as shown in  FIGS. 6 and 9 , the column spacer may be placed over the data line  123  or within the hole  126  to obtain the second or the third cell gap H 2  or H 3 . Thus, the exemplary embodiments of the present invention provide advantages that the liquid crystal cells having various sizes may be fabricated through single process, various cell gaps may be formed and each of the liquid crystal cells may be formed having different viewing angles.  
         [0052]     It will be apparent to those skilled in the art that various modifications and variations can be made in the liquid crystal display device and method for manufacturing the same of the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.