Abstract:
A liquid crystal display device includes an array substrate having reflective and transmissive regions in a pixel region, wherein the array substrate includes a reflective electrode corresponding to the reflective region and a pixel electrode on a first substrate. A color filter substrate defines the reflective region and the transmissive region in the pixel region. The color filter substrate includes a color filter with first and second portions that correspond to the respective transmissive and reflective regions on a second substrate. The thickness of the second portion is less than a thickness of the first portion. The combined thickness of the scatter and the thickness of the second portion is greater than the thickness of the first portion; and a liquid crystal layer between the array and color filter substrates.

Description:
[0001]    This application claims the benefit of Korean Patent Application No. 2005-0135941, filed on Dec. 30, 2005, which is hereby incorporated by reference for all purposes as if fully set forth herein. 
       BACKGROUND 
       [0002]    1. Technical Field 
         [0003]    The present invention relates to a liquid crystal display device, and more particularly, relates to a liquid crystal display device and a method of fabricating the same. 
         [0004]    2. Discussion of the Related Art 
         [0005]    Many types of flat panel displays have been developed to serve as substitutes for cathode-ray tubes (CRTs), such as liquid crystal display (LCD) devices, plasma display panels (PDPs), field emission displays, and electro-luminescence displays (ELDs). LCD devices have many advantages over CRTs, including higher resolution, thinner profile, more compact size, and lower power usage during operation. 
         [0006]    LCD devices generally include two substrates that are spaced apart and face each other and a liquid crystal layer interposed between the two substrates. The two substrates also include electrodes that face each other such that a voltage applied between the electrodes induces an electric field across the liquid crystal layer. Alignment of the liquid crystal molecules in the liquid crystal layer changes in relation to the intensity of the induced electric field which alters the light transmissivity of the LCD device. Thus, the LCD device displays images by varying the intensity of the induced electric field within respective pixel regions that are provided with the LCD device. 
         [0007]    LCD devices may be categorized into transmissive type, reflective type, and transflective type. Transmissive type LCDs require a backlight and consumes a relatively large amount of power during operation. Reflective type LCDs are operated with the aid of external light, and the brightness of the display is proportional to the amount of external light available. Transflective type LCDs are selectively operated in either transmissive or reflective modes. Transflective type LCD devices improve upon the disadvantages of the transmissive type and reflective type LCD devices. 
         [0008]    Referring to  FIG. 1 , in an array substrate  1 , a gate electrode  6 , and a gate line (not shown) are formed on a first substrate  2 . A gate insulating layer  10  is formed on the gate electrode  6 . A semiconductor layer that is formed from an active layer  13  and an ohmic contact layer  16  is provided on the gate insulating layer  10  over the gate electrode  6 . Source and drain electrodes  23 ,  26  are formed on the ohmic contact layer  16 . Each of the gate electrode  6 , the semiconductor layer, and the source and drain electrodes  23 ,  26  combine to form a thin film transistor Tr. A data line  20  is provided on the gate insulating layer  10 . The data line  20  crosses the gate line to define a pixel region P. A first passivation layer  30  is formed on the data line  20  and the source and drain electrodes  23 ,  26 . A reflective electrode  40  is formed on the first passivation layer  30  in a reflective region RA. A second passivation layer  45  is formed on the reflective electrode  40 . A pixel electrode  50  is formed on the second passivation layer  45  in the pixel region P. The pixel electrode  50  contacts the drain electrode  26  through a drain contact hole  55 . 
         [0009]    In a color filter substrate  70 , a black matrix  75  is formed on a second substrate  71 . Red (R), green (G) and blue (B) color filters  80   a ,  80   b , and  80   c  are formed in the corresponding pixel regions P. An overcoat layer  85  is formed on the color filters  80   a ,  80   b  and  80   c . A common electrode  90  is formed on the overcoat layer  85 . 
         [0010]    A liquid crystal layer  60  is provided between the array substrate  1  and the color filter substrate  70 . When voltages are applied to both the pixel and common electrodes  50 ,  90 , an electric field is induced within the liquid layer  60 , and the liquid crystal molecules therein are reoriented in proportion to the electric field. Although not shown in the drawings, an alignment layer is formed on each of the transparent and common electrodes  50 ,  90 . Additionally, first and second retardation films  97 ,  95  may be formed on outer surfaces of the first and second substrates  2  and  71 . 
         [0011]    As best shown in  FIG. 1 , a cell gap d 1  (i.e. the thickness of the liquid crystal layer  60 ) of the reflective region RA is substantially the same as a cell gap d 2  of the transmissive region TA. In a reflective mode, an external light passes through the liquid crystal layer  60 , then reflects on the reflective electrode  40 , and then passes through the liquid crystal layer  60  again. Light in the reflective mode substantially travels as far through liquid crystal layer  60  as in the transmissive mode. Accordingly, there is a phase difference of light between the reflective and the transmissive modes. 
         [0012]    To minimize or eliminate the phase difference, the transflective type LCD device of  FIG. 2  provided. In the transflective type LCD device, a cell gap d 4  (i.e. the thickness of the liquid crystal layer  60 ) within the transmissive region TA is substantially twice the cell gap d 3  within the reflective region RA. Accordingly, the phase difference of  FIG. 1  is substantially prevented because light travels through the same thickness of liquid crystal in both modes. 
         [0013]    However, the transflective type LCD devices of  FIGS. 1 and 2  have some problems. Light in the reflective mode passes through the color filter twice, and light in the transmissive mode passes through the color filter only once. Accordingly, color property differences between the reflective mode and the transmissive mode may occur. Also, the brightness in the reflective mode may be less than in the transmissive mode. Further, the reflectivity is reduced because the reflective electrode is flat. 
         [0014]    Referring to  FIG. 3 , a through hole TH is formed in the color filters  80   a ,  80   b  and  80   c  in the reflective region RA. Light passing through the through hole TH in the reflective mode has substantially the same properties as light passing through the device in the transmissive mode, and brightness in the reflective mode is increased. Further, a first passivation layer  30  formed from two sub layers  30   a ,  30   b  has an uneven surface, which provides the reflective electrode  40  with a similar uneven surface. The uneven surface of the reflective electrode  40  increases the overall reflectivity. However, at least two mask processes are required to form the uneven surface. The additional mast process increase the fabrication time and product cost of an LCD device. Also, the processes of forming the uneven surface, makes it difficult to form a dual cell gap structure within the LDC panel. 
       SUMMARY 
       [0015]    A first representative embodiment of a liquid crystal display device includes an array substrate formed with reflective and transmissive regions in a pixel region, wherein the array substrate includes a reflective electrode corresponding to the reflective region and a pixel electrode on a first substrate. A color filter substrate with the reflective region and the transmissive region is provided in the pixel region that includes a color filter with first and second portions that correspond to the transmissive and reflective regions on a second substrate, respectively. The thickness of the second portion is less than a thickness of the first portion. A scatter layer is provided on the second portion. The combined thickness of the scatter layer and of the second portion is greater than the thickness of the first portion. A liquid crystal layer is provided between the array and color filter substrates. 
         [0016]    Another representative embodiment of a liquid crystal display device includes an array substrate with reflective and transmissive regions formed in a pixel region. The array substrate includes a reflective electrode corresponding to the reflective region and a pixel electrode formed on a first substrate and a color filter substrate with the reflective and transmissive regions formed in the pixel region. The color filter substrate includes a color filter with a through hole in the reflective region on a second substrate and a scatter layer that includes a first portion filling the through hole. The thickness of the first portion is greater than the color filter. A liquid crystal layer is provided between the array and color filter substrates. 
         [0017]    Another representative embodiment provides a method of fabricating a liquid crystal display device. The method includes the steps of fabricating an array substrate with reflective and transmissive regions in a pixel region and fabricating the array substrate to include a reflective electrode corresponding to the reflective region and a pixel electrode on a first substrate. A color filter substrate is provided with the reflective and transmissive regions in the pixel region. The method of forming the color filter includes the steps of forming the color filter substrate with first and second portions that correspond to the transmissive and reflective regions on a second substrate, respectively and interposing a liquid crystal layer between the array and color filter substrates, and forming a scatter layer on the second portion. The thickness of the second portion is less than a thickness of the first portion and the combined thickness of the scatter portion and the second portion is greater than the thickness of the first portion. 
         [0018]    Another representative embodiment is a method of fabricating a liquid crystal display device that includes the steps of fabricating an array substrate having reflective and transmissive regions in a pixel region, including the steps of forming a reflective electrode corresponding to the reflective region and a pixel electrode on a first substrate and fabricating a color filter substrate having the reflective region and the transmissive region in the pixel region. The step of fabricating the color filter substrate includes the steps of forming a color filter with a through hole in the reflective region on a second substrate and forming a scatter layer with a first portion filling the through hole interposing a liquid crystal layer between the array and color filter substrates. The thickness of the first portion is greater than a thickness of the color filter. 
         [0019]    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 
         [0020]    The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention. 
           [0021]    In the drawings: 
           [0022]      FIGS. 1 to 3  are cross-sectional views illustrating examples of transflective type LCD devices according to the related art. 
           [0023]      FIG. 4  is a cross-sectional view illustrating a transflective type LCD device according to a first exemplary embodiment. 
           [0024]      FIG. 5  is a cross-sectional view illustrating a transflective type LCD device according to a second exemplary embodiment. 
           [0025]      FIG. 6  is a cross-sectional view illustrating a transflective type LCD device according to a third exemplary embodiment. 
           [0026]      FIG. 7  is a cross-sectional view illustrating a transflective type LCD device according to a fourth exemplary embodiment. 
           [0027]      FIGS. 8A to 8E  are cross-sectional views illustrating a method of fabricating the color filter substrate according to the embodiment of  FIG. 4 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0028]    Reference will now be made in detail to the embodiments of the present invention, examples of which are illustrated in the accompanying drawings. 
         [0029]    Referring to  FIG. 4 , a transflective type LCD device  101  is provided that includes an array substrate, a color filter substrate and a liquid crystal layer  190  provided therebetween. In the array substrate, a gate electrode  115  and a gate line (not shown) are formed on a first substrate  110 . A gate insulating layer  120  is formed on the first substrate  110  having the gate electrode  115 . A semiconductor layer  125  is formed on the gate insulating layer  120  over the gate electrode  115 . The semiconductor layer  125  includes an active layer  125   a  formed from intrinsic amorphous silicon and an ohmic contact layer  125   b  formed from impurity-doped amorphous silicon. Source and drain electrodes  133 ,  136  are formed on the ohmic contact layer  125   b . A data line (not shown) is formed on the gate insulating layer  120 , which is made of the same material as the source and drain electrodes  133 ,  136 . The data line crosses the gate line to define a pixel region P. The gate electrode  115 , the semiconductor layer  125  and the source and drain electrodes  133 ,  136  form a thin film transistor Tr. 
         [0030]    A first passivation layer  140  is formed on the first substrate  110  having the source and drain electrodes  133 ,  136 . The first passivation layer  140  may be formed from an organic insulating material such as benzocyclobutene (BCB) and acrylic resin. A top surface of the first passivation layer  140  is normally substantially flat. A reflective electrode  146  is formed on the first passivation layer  140  in a reflective region RA. The reflective electrode  146  has a transmissive hole corresponding to a transmissive region TA. A top surface of the reflective electrode  146  is substantially flat. The reflective electrode  146  be formed from a highly reflective material such as aluminum (Al). A second passivation layer  149  is formed on the first substrate  110  having the reflective electrode  146 . 
         [0031]    A drain contact hole  145  is formed through the first passivation layer  140 , the reflective electrode  146 , and the second passivation layer  149  to expose the drain electrode  136 . A pixel electrode  152  is formed on the second passivation layer  140  in the pixel region P and contacts the drain electrode  136  through the drain contact hole  145 . The pixel electrode  152  may also contact the reflective electrode  146  through the drain contact hole  145 . The pixel electrode  152  may be formed from a transparent conductive material such as indium-tin-oxide (ITO), indium-zinc-oxide (IZO), or indium-tin-zinc-oxide (ITZO). A height of the array substrate within the reflective region RA is substantially the same as a height of the array substrate within the transmissive region TA. A black matrix  175  is formed on a second substrate  170  in the color filter substrate. The black matrix  175  may correspond to the thin film transistor T, and the gate and data lines. 
         [0032]    A color filter  178  is formed in the corresponding pixel region P. The color filter  178  includes red (R), green (G) and blue (B) color filters. The color filter  178  has a first portion  178   a  that corresponds to the transmissive region TA and a second portion  178   b  that corresponds to the reflective region RA. The thickness t 11  of the first portion  178   a  is greater than the thickness t 12  of the second portion  178   b . For example, the thickness t 11  of the first portion  178   a  is substantially twice the thickness t 12  of the second portion  178   b . While light in a reflective mode passes through the color filter  178  twice, and light in a transmissive mode passes through the color filter  178  once, because the first portion  178   a  has twice the thickness of the second portion  178   b , the color in the reflective mode can be substantially the same as that in the transmissive mode. 
         [0033]    A scatter layer  182  is provided on the second portion  178   b  that may be formed from a transparent organic insulating material such as a photoresist and a photo acrylic. The scatter layer  182  includes a plurality of beads  183  that scatters light. The beads  183  may be arranged within the scatter layer  182  so that the beads  183  can function as an uneven pattern as shown in  FIG. 3 . The thickness t 13  of the scatter layer  182  is such that a cell gap d 11  (i.e. the thickness of the liquid crystal layer  190 ) of the transmissive region TA is substantially twice a cell gap d 12  of the reflective region RA. In some embodiments, the thickness t 13  of the scatter layer  182  may be one and half times greater the thickness t 11  of the first portion  178   a . A common electrode  185  is formed on the second substrate  170  from a transparent conductive material such as indium-tin-oxide (ITO), indium-zinc-oxide (IZO), or indium-tin-zinc-oxide (ITZO). 
         [0034]    As described above, the reflective region of the color filter has a smaller thickness than the transmissive region. Accordingly, the transflective type LCD device can have substantially the same color properties (brightness, shade, etc.) in the reflective mode and the transmissive mode. Further, the scatter layer  182  has beads  183  and is formed on the color filter layer in the reflective region to provide the high reflectivity and the dual cell gap structure. 
         [0035]      FIG. 5  is a cross-sectional view illustrating a transflective type LCD device according to a second exemplary embodiment of the present invention. The LCD device is similar to that of the first exemplary embodiment except for the color filter and the scatter layer. Accordingly, explanations of parts similar to parts of the first exemplary embodiment are not repeated here for the sake of brevity. 
         [0036]    The color filter in a transmissive region TA has approximately the same thickness t 21  as the color filter in a reflective region RA. A through hole TH is formed in the color filter in the reflective region RA, which allows color properties to be substantially the same in the reflective and transmissive modes. A scatter layer  282  fills the through hole TH and is arranged with a thickness t 22  such that the cell gap d 21  (i.e. the thickness of the liquid crystal layer  290 ) in the transmissive region TA is substantially twice the cell gap d 22  in the reflective region RA that corresponds to the through hole TH. The thickness t 22  of the scatter layer  282  may be twice the thickness t 21  of the color filter, which accordingly achieves the dual cell gap structure. 
         [0037]      FIG. 6  is a cross-sectional view illustrating a transflective type LCD device according to a third exemplary embodiment of the present invention. The LCD device of  FIG. 6  is similar to that of the second exemplary embodiment except for the structure of the scatter layer. Accordingly, an explanation of parts similar to parts of the second exemplary embodiment is not repeated here for the sake of brevity. 
         [0038]    Similar to the second exemplary embodiment, a color filter in a transmissive region TA substantially has the same thickness t 31  as the color filter in a reflective region RA and a through hole TH is formed in the color filter in the reflective region RA. By forming the through hole TH, the color properties may be substantially the same in the reflective and transmissive modes. 
         [0039]    A scatter layer  382  includes first and second portions  382   a  and  382   b . The first portion  382   a  fills the through hole TH, as is similar to the scatter layer discussed with respect to the second exemplary embodiment. The second portion  382   b  is formed on the color filter in the reflective region RA. The second portion  382   b  has a thickness t 32  and the first portion  382   a  has a thickness (t 31 +t 32 ) such that a cell gap d 31  within the transmissive region TA is substantially twice a cell gap d 32  within the reflective region RA. Further, the thickness t 32  of the second portion  382   b  may the same as the thickness t 31  of the color filter, which allows for the dual cell gap structure. 
         [0040]      FIG. 7  is a cross-sectional view illustrating a transflective type LCD device according to a fourth exemplary embodiment of the present invention. The LCD device depicted in  FIG. 7  is similar to that of the first exemplary embodiment except for the structure of the array substrate and the common electrode. Accordingly, explanations of parts similar to parts of the first exemplary embodiment are not repeated here for the sake of brevity. 
         [0041]    The LCD device of the first exemplary embodiment is operated with the electric field that is induced vertically by the pixel electrode of the array substrate and the common electrode of the color filter substrate. The LCD device  401  of the current exemplary embodiment is operated with an in-plane electric field that is induced horizontally by a pixel electrode  452  and reflective and common electrodes  417  and  418  of an array substrate. 
         [0042]    Referring to  FIG. 7 , in the array substrate, the reflective electrode  417  is formed on a first substrate  410  in a reflective region RA. The reflective electrode  417  may be made of the same material as a gate electrode  415 . A common electrode  418  is formed on the first substrate  410  corresponding to a transmissive hole of the reflective electrode  417 . The common electrode  418  contacts the reflective electrode  417 . The common electrode  418  may be formed from a transparent conductive material such as indium-tin-oxide (ITO), indium-zinc-oxide (IZO), or indium-tin-zinc-oxide (ITZO). A gate insulating layer  420  is on the first substrate  410  and has the gate electrode  415 , the reflective electrode  417 , and the common electrode  418 . 
         [0043]    A passivation layer  440  is formed on the first substrate  410  having the source and drain electrodes  433 ,  436 . The passivation layer  440  has a drain contact hole  445  exposing the drain electrode  436 . A plurality of pixel electrodes  452  are formed on the passivation layer  440  in the pixel region P. The pixel electrodes  452  induce an in-plane electric field with the location of the reflective and common electrodes  417 ,  418  below the pixel electrode  452 . The LCD device of the fourth exemplary embodiment is referred to as a FFS (fringe field switching) mode LCD device. Alternately, an IPS (in-plane switching) mode LCD device may be provided. In the IPS mode LCD device, a plurality of pixel electrodes and a plurality of common electrodes are alternately arranged to induce an in-plane electric field. 
         [0044]    The structure to induce the in-plane electric field may be substituted in the second and third exemplary embodiments discussed above. 
         [0045]      FIGS. 8A to 8E  are cross-sectional views of a method for fabricating the color filter substrate according to the first exemplary embodiment of the present invention shown in  FIG. 4 . 
         [0046]    As shown in  FIG. 8A , a black matrix  175  is formed on a substrate  170  with a mask process. The black matrix  175  may be formed from chromium (Cr), chromium oxide (CrOx), or black resin. 
         [0047]    As shown in  FIG. 8B , a red (R) resist layer  177  is formed on the substrate  170  having the black matrix  175 . A mask  196  is located over the red (R) resist layer  177 . The mask  196  has a transmitting portion T, a semi-transmitting portion HTA, and a blocking portion B. The transmitting portion T has a relatively high transmittance to allow for transmission of light, the blocking portion B has a relatively low transmittance to block a significant amount of light, and the semi-transmitting portion HTA has a light transmittance between the transmitting portion T and the blocking portion B. The semi-transmitting portion HTA may have a multi-coating layer  197 . 
         [0048]    The blocking portion B corresponds to a transmissive region TA and the semi-transmitting portion HTA corresponds to a reflective region RA. The transmitting portion T may be between the blocking portions B and the semi-transmitting portions HTA. 
         [0049]    A light exposure is performed for the red (R) resist layer  177 . For example, the red (R) resist layer  177  may be a positive type. When the red (R) resist layer  177  is a negative type, positions of the blocking portion B and the transmitting portion T are altered. After the light exposure, the red (R) resist layer  177  is developed. 
         [0050]    Turning now to  FIG. 8C , after exposing and developing the red (R) resist layer  177 , a red (R) color filter  178  is formed in a pixel region P. A first portion  178   a  of the red (R) color filter  178  that corresponds to the transmissive region TA has a thickness t 11  and a second portion  178   b  of the red (R) color filter  178  that corresponds to the reflective region RA has a thickness t 12 . The blue and green color filters may be formed in the same manner as discussed above. 
         [0051]    The color filters of the second and third exemplary embodiments may be formed using a mask where the transmitting portions and the blocking portions are alternately arranged in the reflective region RA instead of the semi-transmitting portion HTA of  FIG. 8B . In other words, the transmitting portion corresponds to the through hole (TH of  FIGS. 5 and 6 ), and the blocking portion is between the transmitting portion in the reflective region RA. 
         [0052]    Referring to  FIG. 8D , an organic insulating material having a plurality of beads is deposited on the substrate  170  having the red (R), green, and blue (B) color filters and is patterned with a mask process to form a scatter layer  182  in the reflective region RA. Accordingly, the color filter substrate that corresponds to the reflective region RA is thicker than the color filter substrate that corresponds to the transmissive region TA. The cell gap of the transmissive region is substantially twice a cell gap of the reflective region due to the thickness relationship between the color filter and the scatter layer. 
         [0053]    Referring to  FIG. 8E , a common electrode  185  is formed on the substrate  170  having the scatter layer  182 . In the fourth exemplary embodiment, the common electrode is not formed in the color filter substrate, and an over coat layer may be formed on the substrate having the scatter layer. 
         [0054]    Through the above processes, the color filter substrate according to the first exemplary embodiment of the present invention is fabricated. The transflective LCD device is fabricated by attaching the color filter substrate and the array substrate and interposing the liquid crystal layer between the two substrates. 
         [0055]    As explained in the exemplary embodiments, the reflective region of the color filter has a smaller thickness than the transmissive region of the color filter, or the reflective region of the color filter is provided with a through hole. Accordingly, the transflective type LCD device may have substantially the same color properties in both the reflective and transmissive modes. Further, a scatter layer with beads may be formed in the reflective region. Accordingly, the high reflectivity and the dual cell gap structure can be achieved with a relatively simple processes and at a low cost. 
         [0056]    It will be apparent to those skilled in the art that various modifications and variations can be made in 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.