Abstract:
The disclosed invention is with regard to a liquid crystal display panel including a substrate having a plurality of layers formed thereon, and having a first surface region and a second surface region on a surface of an uppermost layer of the plurality of layers, wherein the first and second surface regions having different surface characteristics in reaction to a particular liquid, and a spacer formed on the second surface region.

Description:
[0001]    This application claims the benefit of Korean Patent Application No. P2003-39640 filed in Korea on Jun. 19, 2003, 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 panel, and more particularly to a liquid crystal display panel that has spacers at desirable locations.  
           [0004]    2. Description of the Related Art  
           [0005]    Generally, a liquid crystal display (LCD) controls the light transmittance of liquid crystal cells using an electric field to thereby display a picture on a liquid crystal display panel. To this end, the LCD includes a liquid crystal display panel having liquid crystal cells arranged in an active matrix form, and driving circuits for driving the liquid crystal panel. The liquid crystal display panel is provided with pixel electrodes and a reference electrode, i.e. common electrode, to supply the electric field to each one of the liquid crystal cells. Usually, while each one of the liquid crystal cells on a lower substrate have an individual pixel electrode, the common electrode is formed as an integrated electrode for all of the liquid crystal cells across the entire surface of an upper substrate. Each pixel electrode is connected with a thin film transistor (TFT) that is used for a switching element. The pixel electrode together with the common electrode drives the liquid crystal cell in response to data signals supplied via the TFT.  
           [0006]    [0006]FIG. 1 illustrates a simplified structure of a related art liquid crystal display panel. As shown in FIG. 1, a typical liquid crystal display panel includes coupled upper and lower array substrates  10  and  20 , and liquid crystal material  8  between the upper and the lower array substrates  10  and  20 . The liquid crystal material  8  rotates in response to an electric field supplied to thereby regulate the transmittance of incident light coming through the lower array substrate  20 .  
           [0007]    The upper array substrate  10  includes a color filter  4  and a common electrode  6  formed on the rear surface of the upper substrate  1 . The color filter  4 , where red (R), green (G), and blue (B) colored filter layers arranged in the form of stripe make it possible to display colors by selectively passing the light through these colored filters. A black matrix  2  is placed between the adjacent colored filters  4 , and prevents the degradation of the contrast ratio by absorbing the light from the adjacent cells.  
           [0008]    The lower array substrate  20  includes: a data line  18  and gate line  12  that are crossed and are insulated by a gate insulating layer formed on the entire surface of the lower substrate  21 ; a TFT  16  placed adjacent the crossing of the data and gate lines  18  and  12 ; and a pixel electrode  14  contacting the TFT  16 . In response to gate signals from the gate line  12 , the TFT  16  selectively supplies the pixel electrode  14  with data signals from the data line  18 . The TFT  16  is composed of: a gate electrode connected to the gate line  12 ; a source electrode connected to the data line  18 ; and a drain electrode connected to the pixel electrode  14 .  
           [0009]    The pixel electrode  14  is made from transparent conductive material having high light transmittance, and is placed within the cell region defined by the data line  18  and gate line  12 . Data signals supplied to the pixel electrode  14  via the drain electrode generate electric potential difference between the pixel and common electrodes  14  and  6 . Under the influence of this electric potential difference, the liquid crystals residing between the upper and lower substrates  1  and  21  rotate due to the dielectric anisotropy thereof. Hence, the light supplied from a light source under the lower substrate  21  passes through the liquid crystals toward the upper substrate  1 .  
           [0010]    The cell gap between these upper and lower array substrates  10  and  20  is maintained by spacers, which are made through a manufacturing process illustrated in FIGS. 2 a  to  2   d . As shown in FIG. 2 a , mixed material of solvent, binder, monomer, and photo-initiator is printed onto a substrate  11 . The mixed material is dried so as to evaporate the solvent such that a spacer material  26   a  is formed. The substrate  11  is either a lower substrate having TFTs and pixel electrodes installed thereon or an upper substrate having color filters installed thereon.  
           [0011]    A photoresist  32  is coated on the substrate  11  having the spacer material  26   a  formed thereon. Then, a photomask MS is aligned, as shown in FIG. 2 b . The photomask MS includes a mask substrate  34 . A shielding layer  36  is formed on the mask substrate  34  so as to overlap with a shielding part S 1 . The transparent mask substrate  34  of the photomask MS is exposed at the exposure part S 2 . By carrying out the exposure process to selectively irradiate ultraviolet rays onto the photorest  32  using the photomask MS and the development process to develop the exposed photoresist, a photoresist pattern  38  is formed, as shown in FIG. 2 c . The spacer material  26   a  is patterned through an etching process using the photoresist pattern  38  as a mask, and consequently, a pattern spacer  26  having designated height is formed, as shown in FIG. 2 d.    
           [0012]    The pattern spacer  26  of the related art LCD occupies only about 2% of the area of the substrate  11 . More than 95% of the spacer material  26   a  that was been printed on the entire surface of the substrate  11  to form the pattern spacer  26  is removed during the subsequent processes of exposure, development, and etching. Thus, a lot of spacer material is wasted, which increases the costs of material and fabrication. Further, the additional mask process for forming the pattern spacer  26  including sub-processes, such as printing, exposure, development, and etching, leads to the problem of making the fabricating process even more complex.  
           [0013]    In order to solve these problems, a fabricating method for the spacer using an ink-jet device has been suggested as shown in FIGS. 3 a  to  3   c . First, as shown in FIG. 3 a , an ink-jet device  40  is aligned so as to overlap with the location where the spacer is to be formed on the substrate  11 . Here, the substrate  11  is either a lower substrate  21  having TFTs  16  and pixel electrodes  14  installed thereon or an upper substrate  1  having color filters  4  installed thereon. Then, the spacer material  26   a  is jetted onto the substrate  11  from the ink-jet device  40 . In other words, when an external voltage is supplied to a piezoelectric element of the ink-jet head, physical pressure is generated. This physical pressure causes the conduit  44  connecting the tank  42  containing the spacer material  26   a  with the nozzle  46  to contract and relax repeatedly, and thereby the spacer material  26   a  is jetted to the substrate  11  through the nozzle  46 , as shown in FIG. 3B.  
           [0014]    The spacer  26  formed by the spacer material jetted through the nozzle  46  of ink-jet device thereafter undergoes an exposure to the ultraviolet ray radiated from a light source  48  or a firing process as shown in FIG. 3 c , and then cures to have a width W and height H.  
           [0015]    During the formation of the spacer using the related art ink-jet device, the spacer material  26   a  of low viscosity experiences the gravity while being jetted to the substrate  11 . Due to the effect of gravity, upon arriving at the substrate  11  the spacer material  26   a  spreads out too widely and results in an undesirably small ratio of height H to width W. This leads to the problem of the spacer  26  being formed to overlap with the black matrix  2  so as to encroach into areas that are not overlapped with the black matrix  2 , such as the display area, and appears as a stain on the display area.  
         SUMMARY OF THE INVENTION  
         [0016]    Accordingly, the present invention is directed to a liquid crystal display panel that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.  
           [0017]    An object of the present invention is to provide a liquid crystal display panel and a fabricating method and an apparatus thereof that reduce the amount of material used in forming spacers at desired locations.  
           [0018]    Another object of the present invention is to provide a liquid crystal display panel and a fabricating method and an apparatus thereof that reduce the number of masks used in forming spacers at desired locations.  
           [0019]    Another object of the present invention is to provide a liquid crystal display panel and a fabricating method and an apparatus thereof that consistently forms spacers of an adequate size at desired locations.  
           [0020]    Additional features and advantages of the invention 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 invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.  
           [0021]    To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, there is provided a liquid crystal display panel including a substrate having a plurality of layers formed thereon, and having a first surface region and a second surface region on a surface of an uppermost layer of the plurality of layers, wherein the first and second surface regions having different surface characteristics in reaction to a particular liquid, and a spacer formed on the second surface region.  
           [0022]    In another aspect, a method of fabricating a liquid crystal display panel includes: forming a plurality of layers on a substrate; forming a first surface region by applying a first surface process to a surface of an uppermost layer of the plurality of layers formed on the substrate; forming a second surface region having different surface characteristic in reaction to a particular liquid than the first surface region by applying a second surface process to a portion of the surface of the uppermost layer of the plurality of layers formed on the substrate; and forming a spacer using an ink-jet method.  
           [0023]    In yet another aspect, an apparatus for fabricating a liquid crystal display panel includes: a first surface processing part for forming a first surface region by applying a first surface process to an uppermost layer of a plurality of layers formed on a substrate; and a spacer jetting part for forming a second surface region within the first surface region by applying a second surface process to a designated portion of the first surface region and for jetting spacer material onto the second surface region, wherein the second surface process makes the second surface region different from the first surface region in that the second surface region has different surface characteristics in reaction to a particular liquid than the first surface region.  
           [0024]    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  
       [0025]    These objects and other advantages of the invention will be apparent from the following detailed description of the embodiments of the present invention with reference to the accompanying drawings.  
         [0026]    [0026]FIG. 1 is a perspective view showing the schematic structure of a related art liquid crystal display panel.  
         [0027]    [0027]FIGS. 2 a  to  2   d  are sectional views representing a fabricating process for a pattern spacer of FIG. 1.  
         [0028]    [0028]FIGS. 3 a  to  3   c  depict the process for manufacturing the spacer using a related art ink-jet device.  
         [0029]    [0029]FIG. 4 is a cross sectional view illustrating the upper substrate of a liquid crystal display panel according to an embodiment of the present invention.  
         [0030]    [0030]FIG. 5 is a cross sectional view illustrating the upper substrate of a liquid crystal display panel according to another embodiment of the present invention.  
         [0031]    [0031]FIGS. 6 a  to  6   d  are plane views representing steps of a manufacturing process for an upper plate of the liquid crystal display panel of FIGS. 4 and 5.  
         [0032]    [0032]FIG. 7 is a sectional view showing a manufacturing apparatus for the liquid crystal display panel, which is an integration of the ink-jet jetting part and the laser irradiating part. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0033]    Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings  
         [0034]    [0034]FIG. 4 is a cross sectional view illustrating a liquid crystal display of vertical electric field mode panel according to an embodiment of the present invention. As shown in FIG. 4, the liquid crystal display panel of vertical electric field mode includes a black matrix  52 , a color filter  60 , a planarization layer  54 , a common electrode  58 , and a spacer  56 , which are sequentially formed on an upper substrate  51 .  
         [0035]    The black matrix  52  partitions the upper substrate  51  into a plurality of cell regions in which the color filters  60  are to be formed, and plays a role of preventing the interference of light between adjacent cells. This black matrix  52  is formed so as to overlap areas of a lower array substrate (not shown) that does not include the pixel electrode, such as the areas having TFTs, gate lines, and data lines;  
         [0036]    The color filter  60  is formed in the cell region defined by the black matrix  52 . The color filter  60  is formed using separate red R, green G, and blue B filters to realize red, green, and blue colors. A planarization layer  54  is made of organic insulating material and planarizes the upper substrate  51  having the color filter  60  installed thereon. A flat common electrode  58  is formed on the planarization layer  54 . A reference voltage for driving the liquid crystal is applied to the common electrode  58 . The common electrode  58  is made from transparent conductive material, such as ITO, In 2 O 3  compound, ZnO compound, In 2 O 3 —ZnO, and PEDOT.  
         [0037]    A uniform electric field is applied to the liquid crystal through the common electrode  58  planarized by the planarization layer  54 . The liquid crystal is driven by the vertical electric field formed between the common electrode  58  and the pixel electrode installed on the lower substrate. The surface  62  of the common electrode  58  is divided into a hydrophilic region  80  and a hydrophobic region  82 . The hydrophilic region  80  is formed so as to overlap with the black matrix  52 , and the hydrophobic region  82  is formed on the rest of the common electrode  58 , such as the region of the common electrode  58  that do not overlap the black matrix  52 . Here, the hydrophilic region  80  can be a polygonal shape or a circular, and the length of diameter or diagonal thereof is in the range of about 10˜70 microns (μm).  
         [0038]    The spacer  56  maintains the cell gap between the upper substrate  51  and the lower substrate. The spacer  56  is formed on the upper substrate  51  using an ink-jet method so as to overlap with at least one of a gate line, a data line, and a TFT. This spacer  56  is formed on the hydrophilic region  80  of the common electrode  58  or the planarization layer  54 , and the shape thereof can be either a circle or an oval.  
         [0039]    [0039]FIG. 5 is a cross sectional view illustrating the upper array substrate of a liquid crystal display panel of the horizontal electric field mode according to the second embodiment of the present invention. As shown in FIG. 5, the liquid crystal display panel adopting the horizontal electric field according to the present invention has constituent parts identical to that using the vertical electric field of FIG. 4, except the common electrode for driving the liquid crystal using the horizontal electric field is installed on the lower substrate. Hence, in the liquid crystal display panel of the horizontal electric field according to embodiments of the present invention, the spacer  56  is formed on the uppermost layer, the planarization layer  54 .  
         [0040]    The surface  62  of the planarization layer  54  is divided into a hydrophilic region  80 , which overlaps the black matrix  52 , and a hydrophobic region  82 , which does not overlap the black matrix  52 . The hydrophilic region  80  can be either a polygonal shape or a circular shape, and the length of diameter or diagonal thereof is in the range of about 10˜70 microns (μm). A spacer  56 , made of a hydrophilic material, is formed on the hydrophilic region  80  of the planarization layer  54 , and maintains the cell gap between the upper substrate  51  and the lower substrate.  
         [0041]    [0041]FIGS. 6 a  to  6   d  are perspective views representing the manufacturing process for an upper plate of the liquid crystal display panel according to the first and the second embodiments of the present invention. As shown in FIG. 6 a , a first surface process is applied to the uppermost layer  72  of several layers formed on the upper substrate  51 . The uppermost layer  72  is the common electrode in the case of the liquid crystal display panel of the vertical electric field type, as shown in FIG. 4. Alternatively, the uppermost layer  72  is the planarization layer in the case of the crystal display panel of the horizontal electric field mode, as shown in FIG. 5.  
         [0042]    More specifically, after the upper substrate  51  is placed in a vacuum chamber, a hydrophobic mixed gas  74  flows into the vacuum chamber through a gas supplying part  70 . Here, a gas of fluorine compound such as CF 4  or SF 6  is used for the hydrophobic mixed gas. Afterwards, the fluorine compound gas is dissolved into plasma, and then the dissolved fluorine is deposited on the uppermost layer  72 , the common electrode or the planarization layer. Thus, the entire surface of the uppermost layer  72  becomes the hydrophobic region, which completes the first surface process to the uppermost layer  72 . The first surface process may be carried out using a normal atmospheric pressure method rather than in a vacuum chamber.  
         [0043]    As shown in FIG. 6 b , a second surface process is applied to a designated portion of the uppermost layer  72  which has already been subjected to the first surface process. More specifically, a mask  78  and a laser source  76  are aligned above the first surface processed uppermost layer  72 . Here, the mask  78  has a transmission part  78   a  that overlaps with the black matrix (not shown) formed on the upper substrate  51 , and a shielding part  78   b  that covers the other regions, which are not overlapped by the black matrix.  
         [0044]    A laser beam of relatively short wavelength is generated from the laser source  76  that passes through the transmission part  78   a  of the mask  78 . The wavelength of the laser beam is in the range of about 10˜390 nanometers. The exposed portion of the first surface processed uppermost layer  72  becomes a hydrophilic region  80 . In other words, the hydrophobic portion of the surface of the uppermost layer  72  that overlaps with the black matrix is exposed to the laser beam, and becomes the hydrophilic region  80 , which completes the second surface process.  
         [0045]    As shown in FIG. 6 c , an ink-jet jetting part  86  is aligned above the second surface processed uppermost layer  72 . The ink-jet jetting part  86  jets hydrophilic spacer material  84  onto the uppermost layer  72 . In this case, the hydrophilic spacer material  84  has higher affinity with the hydrophilic region  80  than with the hydrophobic region  82  of the surface of the uppermost layer  72 , which causes the hydrophilic spacer material  84  to stay within the hydrophilic region  80 . Also, the surface tension between the hydrophobic region  82  and hydrophilic spacer material  84  causes some of the hydrophilic spacer material  84  that may have jetted onto the hydrophobic region  82  to move toward the hydrophilic region  80 . Afterwards, the spacer material within the hydrophilic region  80  is hardened by an ultraviolet ray or a heater, then the spacer  90  with designated height is formed as shown in FIG. 6 d.    
         [0046]    On the other hand, the inkjet jetting part  86  and the laser source  76  respectively shown in FIGS. 6 b  and  6   c  may be incorporated in a single unit, such as the spacer maker  96  shown in FIG. 7. Namely, the spacer maker  96  includes an ink-jet jetting nozzle  92  and a laser irradiation nozzle  94 . The laser irradiation nozzle  94  irradiates a laser beam  98  of short wavelength onto the hydrophobic region of the uppermost layer  72  so as to change the irradiated region into a hydrophilic region  80 . Meanwhile, the ink-jet jetting nozzle  92  jets the spacer material  84  onto the hydrophilic region so as to form a spacer. The spacer maker  96  aligned above the substrate  51  is then moved to form the next spacer  90  on the hydrophobic region  80 .  
         [0047]    The laser source  76  in FIG. 6 b , the ink-jet jetting part  86  in FIG. 6 c  can be combined like the inkjet jetting nozzle  92  in FIG. 7 and laser irradiation nozzle  94  in FIG. 7 to have corresponding nozzles in a single unit, to thereby further shorten the process time. On the other hand, the liquid crystal display panel, the fabricating method thereof, and the fabricating apparatus thereof according to the present invention can be used to make the region that overlaps with the black matrix be hydrophobic and other region be hydrophilic, and form a spacer at the hydrophobic region by jetting hydrophobic spacer material to the hydrophobic region.  
         [0048]    As mentioned above in detail, the liquid crystal display panel, the fabricating method thereof, and the fabricating apparatus thereof according to the present invention forms spacers using an ink-jet device. This reduces the number of mask processes and simplify the manufacturing process. Also, a liquid crystal display panel and a fabricating method thereof according to the present invention jet spacer material onto the substrate that is divided into hydrophilic and a hydrophobic regions. This leads to forming spacers of designated height on the hydrophilic regions, which overlap the black matrix. Thus, the spacers of a desired height can be formed at desired regions. Additionally, the integration of a ink-jet jetting part and a laser source can further shorten the manufacturing time.  
         [0049]    Although the present invention has been explained by the embodiments shown in the drawings described above, it should be understood to the ordinary skilled person in the art that the invention is not limited to the embodiments, but rather that various changes or modifications thereof are possible without departing from the spirit of the invention. Accordingly, the scope of the invention shall be determined only by the appended claims and their equivalents.