Abstract:
A transflective liquid crystal display device includes a liquid crystal panel having a pixel electrode, wherein the pixel electrode includes a first reflective region and a first transmissive region, a patterned reflective panel adjacent to the liquid crystal panel, the patterned reflective panel having a second reflective region and a second transmissive region, and a back light unit adjacent to the patterned reflective panel, wherein the patterned reflective panel is movable along a direction parallel to the liquid crystal panel.

Description:
This application is a divisional of U.S. Pat. App. No. 10/268,658 filed Oct. 11, 2002,now U.S. Pat. No. 6,750,932. This application also claims the benefit of Korean Patent Application No. 2001-63140, filed in Korea on Oct. 12, 2001, which is hereby incorporated by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a liquid crystal display (LCD) device and more particularly, to a transflective liquid crystal display (LCD) device that is used both in a transmissive mode and in a reflective mode. 
     2. Discussion of the Related Art 
     In general, a liquid crystal display (LCD) device includes two substrates spaced apart and facing each other, and a liquid crystal material layer interposed between the two substrates. Each of the first and second substrates includes an electrode, whereby the electrodes of each of the first and second substrates face each other. When a voltage is applied to each of the electrodes, an electric field is induced between the electrodes. Accordingly, an alignment of the liquid crystal molecules of the liquid crystal material layer is changed by the varying intensity or direction of the induced electric field. Thus, the LCD device displays an image by varying transmittance of light through the liquid crystal material layer according to the arrangement of the liquid crystal molecules. However, since the liquid crystal display (LCD) device is not luminescent, an additional light source is required to display images. 
     The liquid crystal display device may be categorized into two different types depending upon the type of light source used; a transmissive type and a reflective type. In the transmissive type, a back light is positioned behind a liquid crystal panel, wherein light incident from the back light enters into the liquid crystal panel. Accordingly, an amount of light transmitted through the liquid crystal material layer is controlled by the alignment of the liquid crystal molecules. Thus, the substrates and the electrodes must be formed of transparent conductive materials. Since the transmissive liquid crystal display (LCD) device uses the back light as a light source, it can display bright images in dark surroundings. In addition, the light intensity of the back light must be increased since the amount of transmitted light is relatively small. Consequently, the transmissive liquid crystal display (LCD) device requires a relatively high power consumption due to the low light intensity of the back light. 
     In the reflective type LCD device, ambient sunlight or artificial light is used as a light source of the LCD device. The ambient light incident from the surroundings is reflected by a reflective plate of the LCD device according to the arrangement of the liquid crystal molecules. Since there is no back light, the reflective type LCD device has considerably lower power consumption than the transmissive type LCD device. However, the reflective type LCD device may not be suitable for use in places with low ambient light since an artificial light source would be required. 
       FIG. 1  is a cross-sectional view of a transflective LCD device according to the related art. In  FIG. 1 , transmissive electrodes  12  are formed along an inner surface of a first substrate  11  that includes a thin film transistor (not shown) electrically connected to each of the transmissive electrodes  12 . Reflective electrodes  13  are formed on the transmissive electrodes  12 , and each has a transmissive hole  13   a  exposing a portion of the transmissive electrode  12 . A first polarizer  14  is arranged along an outer surface of the first substrate  11 , thereby linearly polarizing incident light. 
     A second substrate  21  is spaced apart from and faces the first substrate  11 , and a color filter layer  22  is formed on an inner surface of the second substrate  21 . The color filter layer  22  is composed of three sub-color filters of red (R), green (G), and blue (B). Each of the sub-color filters correspond to each of the transmissive electrodes  12 . A common electrode  23  is formed on the color filter layer  22 , and is made of a conductive transparent material. A diffusing film  24  and a second polarizer  25  are subsequently arranged along an outer surface of the second substrate  21 , wherein a transmission axis of the second polarizer  25  is perpendicular to a transmission axis of the first polarizer  14 . A liquid crystal material layer  30  is disposed between the reflective electrodes  13  and the common electrode  23 . 
     In  FIG. 1 , a back light unit  40  is disposed beneath the first polarizer  14 , and is used as a light source during a transmissive mode of the transflective LCD device. The back light unit  40  includes a light guide panel  42 , a lamp  41 , a collimating sheet  43 , and a diffusing sheet  44 . The light guide panel  42  includes scattering patterns formed along a lower surface, thereby changing linear light of the lamp  41  into plane light. 
     In a transmissive mode, a first light “L1”generated from the back light unit  40  penetrates into the first polarizer  14  and through the first substrate  11 . In addition, the first light “L1” passes through the portion of the transmissive electrode  12  that corresponds to the transmissive hole  13   a  and through the liquid crystal material layer  30 . Then, the first light “L1” is transmitted through the common electrode  23 , the color filter layer  22 , the second substrate  21 , the diffusing film  24 , and the second polarizer  25 . 
     In a reflective mode, a second light “L2”incident from ambient surroundings, such as sunlight or artificial light, passes through the second polarizer  25 , the diffusing film  24 , the second substrate  21 , the color filter  22 , the common electrode  23 , and the liquid crystal material layer  30 . Then, the second light “L2”is reflected by the reflective electrode  13  and is transmitted back through the liquid crystal material layer  30 , the common electrode  23 , the color filter  22 , the second substrate  21 , the diffusing film  24 , and the second polarizer  25 . 
     By comparison, the transflective LCD device has lower reflectance than the reflective LCD device because of the transmissive hole  13   a  formed in the reflective electrode  13 . Specifically, in the reflective mode, light incident toward the transmissive hole  13   a  is transmitted to the back light unit  40  and is not reflected. In addition, the transflective LCD device has lower brightness than the transmissive LCD device in the transmissive mode since light incident toward the reflective electrode  13  from the back light unit  40  is reflected toward the back light unit  40 . 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention is directed to a transflective liquid crystal display (LCD) device that substantially obviates one or more of problems due to limitations and disadvantages of the related art. 
     An object of the present invention is to provide a transflective liquid crystal display (LCD) device that improves brightness both in a transmissive mode and in a reflective mode. 
     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. 
     To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, a transflective liquid crystal display device includes a liquid crystal panel having a pixel electrode, wherein the pixel electrode includes a first reflective region and a first transmissive region, a patterned reflective panel adjacent to the liquid crystal panel, the patterned reflective panel having a second reflective region and a second transmissive region, and a back light unit adjacent to the patterned reflective panel, wherein the patterned reflective panel is movable along a direction parallel to the liquid crystal panel. 
     In another aspect, a transflective liquid crystal display device includes first and second substrates spaced apart and facing each other, a thin film transistor on an inner surface of the first substrate, a first passivation layer on the thin film transistor and having a first transmissive hole, a transmissive electrode on the first passivation layer and electrically connected to the thin film transistor, a second passivation layer on the transmissive electrode, a reflector on the second passivation layer and having a second transmissive hole aligned with the first transmissive hole, the second transmissive hole defining a first transmissive region and a first reflective region, a color filter layer on an inner surface of the second substrate, a common electrode on the color filter layer, a liquid crystal material layer between the reflector and the common electrode, a first polarizer on an outer surface of the first substrate, a patterned reflective panel over the first polarizer, the patterned reflective panel having a second transmissive region and a second reflective region, a back light unit over the patterned reflective panel, a diffusing film on an outer surface of the second substrate, and a second polarizer on the diffusing film, wherein the patterned reflective panel is movable along a direction parallel to the first and second substrates. 
     In another aspect, a method of fabricating a transflective liquid crystal display device includes forming a pixel electrode on a liquid crystal panel, wherein the pixel electrode includes a first reflective region and a first transmissive region, forming a patterned reflective panel adjacent to the liquid crystal panel, the patterned reflective panel having a second reflective region and a second transmissive region, and arranging a back light unit adjacent to the patterned reflective panel, wherein the patterned reflective panel is movable along a direction parallel to the liquid crystal panel. 
     In another aspect, a method for changing an operational mode of a transflective liquid crystal display device includes moving a patterned reflective panel along a direction parallel to an adjacent liquid crystal panel, wherein the liquid crystal panel includes a pixel electrode having a first reflective region and a first transmissive region, and the patterned reflective panel includes a second reflective region and a second transmissive region. 
     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 
       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. In the drawings: 
         FIG. 1  is a cross-sectional view of a transflective LCD device according to the related art; 
         FIG. 2  is a cross-sectional view of an exemplary transflective LCD device according to the present invention; 
         FIG. 3  is a plan view of an exemplary patterned reflective panel according to the present invention; 
         FIG. 4  is a cross-sectional view of an exemplary transflective LCD device in a transmissive mode according to the present invention; 
         FIG. 5  is a cross-sectional view of an exemplary transflective LCD device in a reflective mode according to the present invention; 
         FIG. 6  is a plan view of an exemplary array substrate for a transflective LCD device according to the present invention; and 
         FIG. 7  is a cross-sectional view of the exemplary array substrate along VII—VII of  FIG. 6  according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Reference will now be made in detail to the preferred embodiment of the present invention, examples of which are illustrated in the accompanying drawings. 
       FIG. 2  is a cross-sectional view of an exemplary transflective LCD device according to the present invention. In  FIG. 2 , a transflective LCD device may have a first substrate  111  and a second substrate  121 , wherein the first and second substrates  111  and  121  are spaced apart and face each other. Transmissive electrodes  112  may be formed along an inner surface of the first substrate  111 , which may include a thin film transistor (not shown) electrically connected to each of the transmissive electrodes  112 . The transmissive electrodes  112  may be made of a conductive transparent material having a relatively high transmittance. Reflective electrodes  113  may be formed on each of the transmissive electrodes  112 , wherein each of the reflective electrodes  113  may include a transmissive hole  113   a  exposing a portion of the transmissive electrode  112 . The reflective electrode  113  may be made of an conductive opaque material having a relatively high reflectance and a relatively low resistivity. Although the reflective electrodes  113  may be connected to the transmissive electrodes  112 , an insulating layer (not shown) may be positioned between the reflective electrodes  113  and the underlying transmissive electrodes  112 . In addition, the transmissive electrodes  112  may be formed over the reflective electrodes  113 . 
     A first polarizer  114  may be arranged along an outer surface of the first substrate  111 , thereby linearly polarizing any incident light. A patterned reflective panel  150  may be arranged between the first polarizer  114  and a light source  140 . The patterned reflective panel  150  may include a reflective portion  151  formed of a blocking layer and a transmissive portion  152  formed of a transparent substrate. Accordingly, the reflective portion  151  and the transmissive portion  152  may be larger than the transmissive hole  113   a . The patterned reflective panel  150  may be able to move horizontally along right and left directions or along front and rear directions. The movement of the patterned reflective panel  150  may be performed in a manual mode or may be performed in an automatic mode. In either mode, the movement of the patterned reflective panel  150  may be positioned to provide a desired image intensity. Accordingly, light may be reflected both at upper surfaces and lower surfaces of the reflective portions  151  of the patterned reflective panel  150 . 
     A color filter layer  122  may be formed along an inner surface of the second substrate  121 , and may include three sub-color filters of red (R), green (G), and blue (B). Each of the sub-color filters  122  may correspond to each of the transmissive electrodes  112 . In addition, a common electrode  123  may be formed on the color filter layer  122 , and may be made of the same conductive transparent material as the transmissive electrodes  112 . Alternatively, the common electrode  123  and the transmissive electrodes  112  may be made of different conductive transparent materials. 
     A diffusing film  124  and a second polarizer  125  may be arranged along an outer surface of the second substrate  121  and may function as an analyzer, wherein a transmission axis of the second polarizer  125  may have an angle of about 90 degrees with a transmission axis of the first polarizer  114 . 
     A liquid crystal material layer  130  may be disposed between the reflective electrode  113  and the common electrode  123 . In addition, alignment layers may be formed on the reflective electrodes  113  and the common electrode  123 . Accordingly, molecules of the liquid crystal material layer  130  may be arranged horizontally with respect to the first and second substrates  111  and  121  according to the alignment layers. 
     The back light unit  140  may be used as a light source in a transmissive mode in the transflective LCD device. The back light unit  140  may include a light guide panel  142 , a lamp  141  located at a side portion of the light guide panel  142 , a collimating sheet  143 , and a diffusing sheet  144  positioned over the light guide  142 . The light guide panel  142  may include scattering patterns (not shown) formed along the lower surface, thereby changing linear light emitted from the lamp  141  into plane light. The scattering patterns (not shown) may be formed by an etching or printing method, for example. Alternatively, the lower surface of the light guide panel may include multiple regions of variable thickness instead of, or in addition to the scattering patterns. A reflector (not shown) may be arranged beneath the light guide panel  142  to prevent light leakage. 
       FIG. 3  is a plan view of an exemplary patterned reflective panel according to the present invention. In  FIG. 3 , the patterned reflective panel  150  may include the reflective portions  151  and the transmissive portions  152 . The patterned reflective panel  150  may be made of a transparent substrate, whereby a blocking layer is positioned upon the transparent substrate to have a plurality of openings. For example, the blocking layer may correspond to the reflective portions  151  and the openings may correspond to the transmissive portions  152 . Although the transmissive portions  152  are shown having a square shape, other geometries may be implemented. For example, rectangular, circular, and hexagonal geometries may be used to form the transmissive portions  152  of the patterned reflective panel  150 . 
       FIG. 4  is a cross-sectional view of an exemplary transflective LCD device in a transmissive mode according to the present invention. In  FIG. 4 , the transmissive portion  152  of the patterned reflective panel  150  coincides with the transmissive hole  113   a . Accordingly, light emitted from the back light unit  140  may pass through the transmissive portion  152  of the patterned reflective panel  150  and may be linearly polarized by the first polarizer  114 . Then, the linearly polarized light may pass through the first substrate  111  and the portion of the transmissive electrode  122  that corresponds to the transmissive hole  113   a , and may enter into the liquid crystal material layer  130 . Accordingly, transmission of the light may be controlled according to an arrangement of liquid crystal molecules. Finally, a first transmitted light “T1”may be transmitted through the common electrode  123 , the color filter layer  122 , the second substrate  121 , the diffusing film  124 , and the second polarizer  125 . 
     Light emitted from the back light unit  140  and incident upon the reflective portion  151  of the patterned reflective panel  150  may be reflected at the reflective portion  151  of the patterned reflective panel  150 , and may return back to the back light unit  140 . Subsequently, a portion of the light may be reflected to the back light unit  140  and pass through the transmissive portion  152  of the patterned reflective panel  150 . Thus, a second transmitted light “T2” may be transmitted through a same path as the first transmitted light “T1.” 
     Conversely, ambient light such as sunlight or artificial light may sequentially pass through the second polarizer  125 , the diffusing film  124 , the second substrate  121 , the color filter layer  122 , the common electrode  123 , and the liquid crystal material layer  130 . Accordingly, the light may be reflected by the reflective electrode  113  and retransmitted back through the liquid crystal material layer  130 , the common electrode  123 , the color filter layer  122 , the second substrate  121 , the diffusing film  124 , and the second polarizer  125 , and emerge as a reflected light “R.”. Thus, since a total amount of transmitted light increases due to the patterned reflective panel  150  and the additional reflected light “R,” the transflective LCD device may have a relatively higher brightness in the transmissive mode. 
       FIG. 5  is a cross-sectional view of an exemplary transflective LCD device in a reflective mode according to the present invention. In  FIG. 5 , the reflective portion  151  of the patterned reflective panel  150  corresponds to the transmissive hole  113 . Accordingly, ambient light such as sunlight or artificial light may pass through the second polarizer  125 , thereby linearly polarizing the ambient light. The linearly polarized light may pass through the diffusing film  124 , the second substrate  121 , the color filter layer  122 , and the common electrode  123 , and into the liquid crystal material layer  130 . Thus, the alignment of the liquid crystal molecules may control the transmission of the linearly polarized light. Next, the light may be reflected by the reflective electrode  113  and again pass through the liquid crystal material layer  130 . Subsequently, the light may be retransmitted through the common electrode  123 , the color filter layer  122 , the second substrate  121 , the diffusing film  124 , and the second polarizer  125 , and emerge as a first reflected light “R1.” 
     Conversely, a portion of ambient light may pass through the second polarizer  125 , the diffusing film  124 , the second substrate  121 , the color filter layer  122 , the common electrode  123 , and the liquid crystal material layer  130 . Then, the light may pass through the transmissive hole  113   a , the transmissive electrode  112 , the first substrate  111 , and the first polarizer  114 , and may be reflected by the reflective portion  151  of the patterned reflective panel  150 . Accordingly, the light may be retransmitted through the first polarizer  114 , the first substrate  111 , the transmissive electrode, the transmissive hole  113   a , the liquid crystal material layer  130 , the common electrode  123 , the color filter layer  122 , the second substrate  121 , the diffusing film  124 , and the second polarizer  125  to emerge as a second reflected light “R2.” Thus, in the reflective mode of the transflective LCD device, a loss of light is prevented due to the reflective portion  151  of the patterned reflective panel  150 , and the brightness of the transflective LCD device increases. 
       FIG. 6  is a plan view of an exemplary array substrate for a transflective LCD device according to the present invention, and  FIG. 7  is a cross-sectional view of the exemplary array substrate along VII—VII of  FIG. 6  according to the present invention. In  FIGS. 6 and 7 , a gate electrode  222  may be formed on a transparent substrate  210 , and may be connected to a gate line  221  that extends along a horizontal direction. The transparent substrate  210  may be made of an insulating material such as glass, and the gate electrode  222  and the gate line  221  may be formed of a conducting material such as a metal. A gate insulator  230  may cover the gate electrode  222  and the gate line  221 , and may be made of silicon nitride (SiNx) or silicon oxide (SiO 2 ), for example. 
     An active layer  241  and an ohmic contact layer  251  may be subsequently formed on the gate insulator  230 , wherein the active layer  241  may be made of amorphous silicon, for example, and the ohmic contact layer  251  may be made of doped amorphous silicon, for example. Next, source and drain electrodes  262  and  263  may be formed on the ohmic contact layer  251 , wherein the source electrode  262  may be connected to a data line  261  that extends along a vertical direction perpendicular to the horizontal direction. The data line  261  may cross the gate line  221 , thereby defining a pixel region. The ohmic contact layer  251  may lower a contact resistance between the active layer  241  and the source and drain electrodes  262  and  263 . 
     A first passivation layer  270  may cover the data line  261  and the source and drain electrodes  262  and  263 , and may include a first contact hole  271  and a first transmissive hole  272 . The first passivation layer  270  may be made of a benzocyclobutene (BCB) or a photosensitive acrylic resin, for example. The first contact hole  271  may expose a portion of the drain electrode  263  and the first transmissive hole  272  may expose a portion of the transparent substrate  210  through the gate insulator  230 . Alternatively, the gate insulator  230  may be not etched such that the first transmissive hole  272  may be formed only through the first passivation layer  270 . The first transmissive hole  272  may result in increasing a thickness of a liquid crystal material layer (not shown) in a transmissive region. Accordingly, a thickness of the liquid crystal material layer in a reflective region may be relatively thinner, thereby optimizing an optical characteristic of a transmissive mode with an optical characteristic of a reflective mode, simultaneously. 
     A transmissive electrode  280  may be formed on the first passivation layer  270 , and positioned in the pixel region. The transmissive electrode  280  may be connected to the drain electrode  263  through the first contact hole  271 . The transmissive electrode  280  may be made of a conductive transparent material such as indium-tin-oxide (ITO) and indium-zinc-oxide (IZO), for example. 
     A second passivation layer  290  may be formed on the transmissive electrode  280 , and may include a second contact hole  291  that exposes a portion of the transparent electrode  270  that corresponds to the first contact hole  271 . The second passivation layer  290  may be made of silicon nitride (SiNx) and silicon oxide (SiO 2 ), for example. 
     A reflective electrode  300  may be formed on the second passivation layer  290 , and may be connected to the transmissive electrode  280  through the second contact hole  291 , thereby functioning as a reflector. Alternatively, the reflective electrode  300  may be formed beneath the transmissive electrode  280  and may not be connected to the transmissive electrode  280 . The reflector  300  may include a second transmissive hole  302  that exposes a portion of the transmissive electrode  280  that corresponds to the first transmissive hole  272 . 
     It will be apparent to those skilled in the art that various modifications and variations can be made in the fabrication and application 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.