Abstract:
A transflective liquid crystal display panel includes a first substrate, a second substrate arranged opposite to the first substrate, and a plurality of pixels positioned between the first substrate and the second substrate. Each of the pixels having at least one reflecting region and at least one transmitting region includes a color filter layer formed on the substrate and located in both of the reflecting region and the transmitting region, at least one first reflective layer formed between the color filter layer and the substrate and located in the reflecting region, at least one switch element located in the reflecting region, and at least one second reflective layer located in the reflecting region.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a transflective liquid crystal display panel, and more particularly, to a transflective liquid crystal display panel having integrated switch elements and a color filter layer on a substrate. 
     2. Description of the Prior Art 
     Liquid crystal displays are commonly utilized in various electronic products including personal computers, digital cameras, cell phones, PDAs, and projectors. As the market demand for display panels continues to increase, transflective liquid crystal displays having dual operating modes have become widely popular. Typically, a transflective liquid crystal display includes two operating modes: a reflective mode and a transmitting mode. In most circumstances, when the reflective mode is operating, light from the external environment is being used, whereas when the transmitting mode is operating, light generated from a backlight module is being used. 
     Typically, a transflective liquid crystal display panel is made up of a color filter substrate and an array substrate having corresponding electrodes thereon, and a liquid crystal layer disposed between the color filter substrate and the array substrate. The surface of the array substrate includes a plurality of thin film transistors as switch elements. Each of the thin film transistors includes a gate electrode connected to a scan line, a source electrode connected to a data line, and a drain electrode connected to a pixel electrode. The pixel electrodes are specifically composed of reflective electrodes and transparent electrodes, in which the reflective electrodes are utilized to form a reflective region of the display panel and the transparent electrodes are utilized to form a transmitting region of the display panel. The color filter substrate includes a black matrix layer, a color filter layer for displaying colors, and a transparent common electrode disposed on top surfaces of the black matrix layer and the color filter layer. 
     As the resolution of the liquid crystal display panel increases, the accuracy for the alignment between the color filter substrate and the array substrate also increases accordingly. If a shift occurs between the two substrates, a color representing a pixel region of the display panel is likely to be influenced by the color of the adjacent pixel region and result in a color-mixing phenomenon, which may further bring a light leakage phenomenon. 
     A technique commonly utilized for solving the above problem involves directly forming a color filter layer with colors such as red, blue, and green on the pixel region of an array substrate. However, those skilled in the art would know, if the color filter layer disposed on the array substrate produces any defects, the process for removing the color filter layer from the array substrate would become difficult as the solvents utilized already affect the devices located on the surface of the array substrate. Therefore, the method cannot rework the color filter layer on the array substrate, and the result not only wastes a large quantity of array substrates but also increases the overall fabrication cost. 
     SUMMARY OF THE INVENTION 
     It is an objective of the present invention to provide a transflective liquid crystal display panel for preventing the aforementioned color-mixing phenomenon. 
     It is another aspect of the present invention to provide a transflective liquid crystal display panel for increasing yield and reducing overall cost of the fabrication process. 
     It is another aspect of the present invention to provide a transflective liquid crystal display panel with improved reflective ability. 
     A transflective liquid crystal display panel is disclosed. The transflective liquid crystal display panel includes: a first substrate; a second substrate, disposed opposite to the first substrate; a liquid crystal layer, disposed between the first substrate and the second substrate; and a plurality of pixels arranged in a manner of a matrix between the first substrate and the second substrate, in which each of the pixels comprises a reflecting region and a transmitting region. Each of the pixels includes a color filter layer disposed on the first substrate and located in both the reflecting region and the transmitting region; a first reflective layer disposed between the color filter layer and the first substrate and located in the reflecting region; at least one switch element disposed in the reflecting region; and a second reflective layer disposed in the reflecting region. 
     Preferably, the fabrication of the color filter layer is completed before the fabrication for the thin film transistors. By performing the fabrication according to this order, the color filter can be reworked directly without affecting other devices. Additionally, by integrating both the color filter layer and the thin film transistor on a substrate, problem problems such as misalignment between two substrates can be reduced significantly. Moreover, a reflective layer can be disposed on the color filter layer of the reflective region for reflecting ambient lights without going through the color filter layer, thereby increasing the intensity of reflected lights and the reflectivity of the display panel. 
     These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a top-view of a pixel of a transflective liquid crystal display panel according to the first embodiment of the present invention. 
         FIG. 2  illustrates a cross-section along the line A-A′ shown in  FIG. 1 . 
         FIG. 3  illustrates a pixel  300  of a transflective liquid crystal display panel according to the second embodiment of the present invention. 
         FIG. 4  illustrates a cross-section of a pixel of a transflective liquid crystal display panel according to the third embodiment of the present invention. 
         FIG. 5  illustrates a cross-section of a pixel of a transflective liquid crystal display panel according to the fifth embodiment of the present invention. 
         FIG. 6  illustrates a cross-section of a pixel of a transflective liquid crystal display panel according to the sixth embodiment of the present invention. 
         FIG. 7  illustrates a cross-section of a pixel of a transflective liquid crystal display panel according to the seventh embodiment of the present invention. 
         FIG. 8  illustrates a cross-section of a pixel of a transflective liquid crystal display panel according to the eight embodiment of the present invention. 
         FIG. 9  illustrates a cross-section of a pixel of a transflective liquid crystal display panel according to the ninth embodiment of the present invention. 
         FIG. 10  illustrates a cross-section of a pixel of a transflective liquid crystal display panel according to the tenth embodiment of the present invention. 
         FIG. 11  illustrates a cross-section of a pixel of a transflective liquid crystal display panel according to the eleventh embodiment of the present invention. 
         FIG. 12  illustrates a cross-section of a pixel of a transflective liquid crystal display panel according to the twelfth embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     First Embodiment 
     Referring to  FIG. 1  and  FIG. 2 ,  FIG. 1  illustrates a top-view of a pixel  100  of a transflective liquid crystal display panel according to the first embodiment of the present invention.  FIG. 2  illustrates a cross-section along the line A-A′ shown in  FIG. 1 . The pixel  100  includes a bottom substrate  102  (such as first substrate), a top substrate  103  (such as second substrate), and a liquid crystal layer  104 . The top substrate  103  includes a transparent substrate  105  and a common electrode  106 , in which the top substrate  103  can be a vertical alignment liquid crystal display panel or a multi-domain vertical alignment liquid crystal display (MVA-LCD) panel. Instead of being disposed on the transparent substrate  105 , the common electrode  106  can also be disposed on the bottom substrate  102  to form an in-plane switching liquid crystal display (IPS-LCD). The bottom substrate  102  includes a transparent substrate  108  and a color filter layer  112  disposed on the transparent substrate  108 . A first reflective layer  110  is disposed on a portion of the transparent substrate  108  and between the color filter layer  112  and the transparent substrate  108  to form a reflecting region  1 R. The reflecting region  1 R serves to reflect white lights particularly from the ambience, for example, white light, or other color light. Typically, ambient lights are transformed into lights with colors after passing through the color filter layer  112 . The remaining portion of the bottom substrate  102  forms a transmitting region  1 T, in which lights from a backlight module (not shown) will penetrate the color filter layer  112  in the transmitting region to generate lights with colors. 
     The bottom substrate  102  also includes a first planarizing layer  114  disposed on the color filter layer  112 , a switch element  116  and a capacitor  132  disposed on the first planarizing layer  114  with respect to the reflecting region  1 R. The switch element  116 , preferably, is a thin film transistor, in which the switch element  116  includes a gate electrode  118  electrically connected to a scan line SL, a gate insulating layer  120 , a semiconductor layer  122 , a source electrode  124  electrically connected to a data line DL, a drain electrode  126  electrically connected to a pixel electrode  130 , and a passivation layer  128 . As shown in  FIG. 1 , the capacitor (Cs)  132  includes a bottom electrode  134  and a top electrode  136 , in which the top electrode  136  can be an extension portion extending from the drain electrode  126 , but not limited thereto. The structure of the thin film transistor can be a top gate structure or a bottom gate structure, and the thin film transistor can be an N-type transistor, a P-type transistor, or combinations thereof. The material of the semiconductor layer  122  comprises single crystal silicon, amorphous silicon, polysilicon, microcrystalline silicon, or a combination thereof. The gate insulating layer  120 , the first planarizing layer  114 , and the passivation layer  128  can be composed of substantially identical or substantially different materials. Preferably, materials utilized for fabricating the gate insulating layer  120 , the first planarizing layer  114 , and the passivation layer  128  are selected from organic materials, inorganic materials, or a combination of both. Specifically, the organic materials include organosilicon, photoresist, polyethylene oxide, polymethyl methacrylate, polyesters, polyethylene compounds, or likes, or combinations thereof, and the inorganic materials include silicon nitride, silicon oxide, silicon oxynitride, silicon carbide, or others, or a combination thereof. According to the preferred embodiment of the present invention, the thin film transistor is a bottom gate thin film transistor and the semiconductor layer  122  is composed of polysilicon as an exemplification. 
     As shown in  FIG. 2 , by first forming the color filter layer  112  on the transparent substrate  108 , reworks can be done directly on the color filter layer  112  if impurities or defects were found in the color filter layer  112 . After the color filter layer  112  is inspected, the switch element  116  and the capacitor  132  are disposed on the inspected color filter layer  112 , thus increasing the yield of the products. Additionally, by disposing, the switch element  116 , the capacitor  132 , the pixel electrode  130 , and the color filter layer  112  on the transparent substrate  108 , problems such as misalignment between two substrates commonly found in the conventional art is also prevented. 
     Since the capacitor  132  is disposed on the color filter layer  112  and the top electrode  136  is composed of metal, a portion of light is reflected by the top electrode  136  without passing through the color filter layer  112 , thus the reflectivity of light at this region is increased. An additional second reflective layer can be formed on the color filter layer  112 , such as in the present embodiment, the top electrode  136  of the capacitor  132  is used as a second reflective layer. However, if the top electrode  136  of the capacitor  132  is composed of transparent material, the bottom electrode  134  can be used as the second reflective layer. 
     Second Embodiment 
       FIG. 3  illustrates a pixel  300  of a transflective liquid crystal display panel according to the second embodiment of the present invention. The second embodiment is structurally similar to the first embodiment described above. However, in this embodiment, the first reflective layer  310  is not only disposed below the interval between the scan line SL and the pixel electrode  130 , but also below the interval between the data line DL and the pixel electrode  130  for reflecting ambient light. Additionally, the first reflective layer  310  can also be disposed either below the interval between the scan line and the pixel electrode  130  or below the interval between the data line and the pixel electrode  130 . In other words, the first reflective layer  310  is disposed below at least one of the interval between the scan line SL and the pixel electrode  130 , and the interval between the data line DL and the pixel electrode  130 . 
     In this embodiment, a first reflective layer  310  is disposed below the interval between the scan line SL and the pixel electrode  130  and the interval between the data line DL and the pixel electrode  130  as an exemplification, thus the reflective area and the intensity of the reflected light are increased accordingly. 
     Third Embodiment 
       FIG. 4  illustrates a cross-section of a pixel  400  of a transflective liquid crystal display panel according to the third embodiment of the present invention. The third embodiment is structurally similar to the first embodiment. However, in this embodiment, the first reflective layer  410  includes a rough and uneven surface, such as a waved surface, such that the waved surface increases the reflectance of ambient lights and enhances the uniformity of light distribution. Preferably, the fabrication of the waved surface of the first reflective layer  410  can be achieved by first forming an insulating layer  402  between the transparent substrate  108  and the color filter layer  112 . Thereafter, a series of exposure, development, and etching processes is performed to form a waved surface on a portion of the insulating layer  402  surface, and the first reflective layer  410  is disposed on the waved surface of the insulating layer  402 . Alternatively, a series of exposure, development, and etching processes can be performed to form a waved surface on a portion of first reflective layer  410  by not using any additional layer. 
     Fourth Embodiment 
     In contrast to the first embodiment, the fourth embodiment includes a protection layer (not shown) disposed on the first planarizing layer  114 , and the switch element  116  and the capacitor  132  are disposed on the passivation layer thereafter. The material of the protection layer comprises an inorganic material, such as silicon oxide, silicon nitride, silicon oxynitride, or silicon carbide. By using inorganic material to fabricate the protection layer, the stability of the layer is increased and impurities or particles passing from the planarizing layer or the color filter layer that may influence the switch element  116  and the capacitor  132  are blocked, thereby increasing the performance of the transflective liquid crystal display panel. Since the gate electrode  118  and the bottom electrode  134  are also similarly composed of inorganic material like the protection layer, phenomenon such as peeling taken place between the gate electrode  118  and the planarizing layer or between the bottom electrode  134  and the planarizing layer can also be prevented. Additionally, the material of the protection layer can comprise an organic material having strong stability, such as epoxy compounds, acrylic compounds, copolymers, or a combination thereof/with inorganic materials. 
     Fifth Embodiment 
       FIG. 5  illustrates a cross-section of a pixel  500  of a transflective liquid crystal display panel according to the fifth embodiment of the present invention. The fifth embodiment is structurally similar to the first embodiment. However, in this embodiment, a light-blocking layer  502  is disposed between the transparent substrate  105  and the common electrode  106 . The light-blocking layer  502  is at least disposed and substantially corresponds to the switch element  116  formed on the bottom substrate  102  to prevent ambient light from generating photo current after penetrating the switch element  116  from the top substrate  103 . Preferably, the material of the light-blocking layer  502  comprises inorganic material, organic material, or a combination thereof. The inorganic material includes metals such as chromium, gold, aluminum, molybdenum, neodymium, titanium, tantalum, tungsten, metal alloys, metal compounds such as nitrides or oxides, or material containing silicon, or others, or combinations thereof. 
     Sixth Embodiment 
       FIG. 6  illustrates a cross-section of a pixel  600  of a transflective liquid crystal display panel according to the sixth embodiment of the present invention. The sixth embodiment is structurally similar to the first embodiment. However, in this embodiment, a diffusing layer  602  is disposed between the transparent substrate  105  and the common electrode  106 . The diffusing layer  602  is disposed with respect to the reflective region  1 R, such that reflected light from the ambient environment would scatter after passing through the diffusing layer  602 , thus resulting in a much more even distribution. The transmitting region  1 T still allows lights illuminating from the backlight module (not shown) to go through the color filter layer  112  for generating lights of colors. The diffusing layer  602  can be a transparent layer with/without scattering particles, such as a layer composed of epoxy, organic materials, acrylics, copolymers, or similar materials, or combinations thereof. 
     Seventh Embodiment 
       FIG. 7  illustrates a cross-section of a pixel  700  of a transflective liquid crystal display panel according to the seventh embodiment of the present invention. The seventh embodiment is structurally similar to the first embodiment. However, in this embodiment, a second planarizing layer  702  is disposed on the passivation layer  128 , and the pixel electrode  130  is disposed on the second planarizing layer  702  and electrically connected to the drain electrode  126 . 
     Preferably, the second planarizing layer  702  includes a depth of about 2 μm to about 3 μm or more than about 3 μm, such that even if the pixel electrode  130  overlaps at least one of the switch element  116 , the scan line SL, and the data line DL, the pixel electrode  130  is not influenced by the parasitic capacitance generated by the overlapping region. By having this design, the area of the pixel electrode  130  can be enlarged, thereby increasing the aperture ratio and brightness of the display panel. The second planarizing layer  702  can be composed of substantially the same material or substantially different material as the first planarizing layer  114 . 
     Eighth Embodiment 
       FIG. 8  illustrates a cross-section of a pixel  800  of a transflective liquid crystal display panel according to the eight embodiment of the present invention. The eighth embodiment is structurally similar to the seventh embodiment. However, in this embodiment, a reflective electrode  802  is disposed on the second planarizing layer  702 , in which the reflective electrode  802  also includes a rough and uneven surface, such as a waved surface to enhance the scatter of ambient light. The reflective electrode  802  is electrically connected to the drain electrode  126 , and the remaining portion of the panel not covered by the reflective electrode  802  and/or the first reflective layer  110  is used to form a transmitting region. In the transmitting region, light is generated from a backlight module (not shown) and resulting into colors after passing through the color filter layer  112 . In this embodiment, both the top electrode  136  of the capacitor  132  and the reflective electrode  802  can be used as a second reflective layer. Preferably, the fabrication of the waved surface of the reflective electrode  802  can be achieved by first performing a series of exposure, development, and etching processes on a portion of the second planarizing layer  702  to form a waved surface, and then forming the reflective electrode  802  on the waved surface of the second planarizing layer  702 . Alternatively, a series of exposure, development, and etching processes can be performed to form a waved surface on a portion of the reflective electrode  802  by not using any additional layer. In addition, the first reflective layer  110  can be formed with/without a waved surface, as shown in  FIG. 4 . 
     Ninth Embodiment 
       FIG. 9  illustrates a cross-section of a pixel  900  of a transflective liquid crystal display panel according to the ninth embodiment of the present invention. The ninth embodiment is structurally similar to the seventh embodiment. However, in this embodiment, a protection layer  910  is disposed on the first planarizing layer  114 , and the switch element  116  and the capacitor  132  are disposed on the protection layer  910  thereafter. 
     It should be noted that in addition to the protection layer  910 , structures described in the previous embodiments can also be incorporated in the present embodiment. For instance, as shown in  FIG. 3 , the first reflective layer  310  disposed below at least one of the interval between the scan line and the pixel electrode  130  and below the interval between the data line and the pixel electrode  130  can be incorporated for reflecting ambient lights. Additionally, as shown in  FIG. 5 , the light-blocking layer  502  disposed between the transparent substrate  105  and the common electrode  106  can be incorporated, in which the light-blocking layer  502  is at least disposed substantially corresponding to the switch element  116  of the bottom substrate. The diffusing layer  602 , disposed substantially corresponding to the reflective region  1 R, and between the transparent substrate  105  and the common electrode  106 , as shown in  FIG. 6 , can also be incorporated for enhancing the uniformity of light distribution after ambient lights are scattered via the diffusing layer  602 . Moreover, the structures shown in  FIG. 7  and  FIG. 8  can also be incorporated. As shown in  FIG. 7 , a second planarizing layer  702  is disposed on the passivation layer  128 , and the pixel electrode  130  is disposed on the second planarizing layer  702  and electrically connected to the drain electrode  126 . As shown in  FIG. 8 , a reflective electrode  802  is disposed on the second planarizing layer  702  and electrically connected to the drain electrode  126 , in which the reflective electrode  802  includes a rough and uneven surface, such as a waved surface for facilitating the scatter of reflected lights. 
     Tenth Embodiment 
       FIG. 10  illustrates a cross-section of a pixel  1000  of a transflective liquid crystal display panel according to the tenth embodiment of the present invention. Preferably, the present embodiment includes a combination of various structures taken from the previous embodiments. For instance, structures from  FIG. 4  and  FIG. 8  are combined in this embodiment, in which the first reflective layer  410  includes a rough and uneven surface, such as a waved surface for enhancing the scatter and uniformity of the reflected ambient lights. A reflective electrode  802  is disposed on the second planarizing layer  702  and electrically connected to the drain electrode  126 , in which the reflective electrode  802  includes a rough and uneven surface, such as a waved surface for facilitating the scatter of reflected ambient lights. The remaining portion of the substrate not covered by the reflective electrode  802  and/or the first reflective layer  410  serves as a transmitting region to allow lights projecting from a backlight module (not shown) to the color filter layer  112  to produce lights having colors. Preferably, the convex portion of the first reflective layer  410  is formed partially or completely corresponding to the convex portion of the reflective electrode  802  and/or concave portion of the reflective electrode  802 . Hence, by using the waved surface of the first reflective layer  410  and the reflective electrode, the reflectivity of the panel with respect to the ambient lights is increased significantly. 
     Additionally, the reflectivity of the display panel can be further enhanced by disposing the diffusing layer  602  shown in  FIG. 6  between the transparent substrate  105  and the common electrode  106 . As the reflectivity of the ambient light increases, the light-blocking layer  502  shown in  FIG. 5  can be further applied in this embodiment to prevent light leakage. The light-blocking layer  502  is preferably disposed substantially corresponding to the switch element of the bottom substrate. 
     Eleventh Embodiment 
       FIG. 11  illustrates a cross-section of a pixel  1100  of a transflective liquid crystal display panel according to the eleventh embodiment of the present invention. The eleventh embodiment is structurally similar to the previous embodiments. However, in this embodiment, the switch element, such as the thin film transistor of the pixel  1100  and the capacitor  132  are disposed under the color filter layer  112 . Nevertheless, at least one of the first reflective layer  410  having a rough and uneven surface, such as a waved surface, the light-blocking layer  502 , the diffusing layer  602 , the reflective electrode  802  having a waved surface, and the passivation layer  910  described from the first embodiment to the tenth embodiment can be incorporated into the present embodiment, which are all within the scope of the present invention. Additionally, a protection layer (not shown), such as an alignment film, a planarizing layer, a buffering layer, or a combined layer thereof can be selectively disposed on the color filter layer  112 . 
     Twelfth Embodiment 
       FIG. 12  illustrates a cross-section of a pixel  1200  of a transflective liquid crystal display panel according to the twelfth embodiment of the present invention. The twelfth embodiment is structurally similar to the previous embodiments. However, this embodiment specifically forms a diffusing layer  912  between the first reflective layer  110  and the color filter layer  112 . The position of the diffusing layer  912  preferably allows the ambient light passing the first reflective layer  110  to produce a much more even distribution, in which the diffusing layer  912  can be composed of a transparent layer with/without scattering particles therein. For instance, the diffusing layer  912  can be comprised of epoxy compounds, an organic material, acrylic compounds, copolymers, or others, or combinations thereof/with inorganic materials. Additionally, preferred, at least one of the first reflective layer  410 , the light-blocking layer  502 , the reflective electrode  802  having a rough and uneven surface, such as a waved surface, and the protection layer  910  disclosed in the above-mentioned embodiments can be further utilized in the present embodiment, which are all within the scope of the present invention. 
     It should be noted that the surface of the color filter layer  112  disposed on the bottom substrate  108  is substantially flat, but not limited thereto. Hence, the surface of the color filter layer  112  can be formed according to the profile of the layer disposed under it, such as having a substantially stepped profile or a stairway profile. For instance, as shown in the twelfth embodiment, after the first reflective layer  110  is formed on the bottom substrate  108  and the diffusing layer  912  is formed on the first reflective layer, a substantially stepped profile would appear between the surface of the diffusing layer  912  and the surface of the bottom substrate  108 . In other words, an uneven profile would appear between the surface of the color filter layer  112  disposed on the diffusing layer  912  and the surface of the color filter layer  112  disposed on the bottom substrate, such as the substantially stepped profile shown in the figure. Moreover, the above-mentioned embodiments of the present invention describing the light of colors include a single color or a multi-color, in which the color can be red, green, blue, white, yellow, violet, cyan, magenta, black, pink, brown, dark green, colorless, or other colors shown in the color gamut of the color coordinates, such as Commission Internationale de L&#39;Eclairage (CIE), color combination indexes, or other indexes. 
     Preferably, the fabrication of the color filter layer is completed before the fabrication for the thin film transistors and by disposing the thin film transistors on the color filter layer, the color filter can be reworked directly without affecting other devices such as the switch element and the capacitor. Additionally, by integrating both the color filter layer and the thin film transistor on a substrate, problems such as misalignment between two substrates can be reduced. Moreover, a reflective layer can be disposed on the color filter of the reflective region for reflecting ambient lights without going through the color filter layer, thereby increasing the intensity of reflected lights and the reflectivity of the display panel. 
     Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.