Abstract:
According to an embodiment of the present invention, there is disclosed a transflective electrochromic liquid crystal display device, comprising a first electrode layer, a second electrode layer and an electrochromic layer and a liquid crystal layer, wherein the electrochromic layer is located between the first electrode layer and the second electrode layer. The present invention can achieve a good display effect in each of a reflective mode and a transmissive mode; and production costs are low, and resolution and aperture ratio can be increased.

Description:
TECHNICAL FIELD 
     An embodiment of the present invention relates to a transflective electrochromic liquid crystal display device. 
     BACKGROUND 
     Display modes for liquid crystals can roughly be divided into a vertical electric field mode and a horizontal electric field mode. As for the horizontal electric field mode, there are an In-Plane-Switching (IPS) mode, a Fringe Field Switching (FFS) mode, and etc. 
     The structure of an existing vertical electric field mode liquid crystal display device is shown in  FIG. 1 , and from bottom to top, the structure comprises: a backlight source  60 , a first polarizer  71 , a first substrate (TFT array substrate)  70 , a first electrode layer  72 , a first alignment layer  73 , a liquid crystal layer  90 , a second alignment layer  83 , a second electrode layer  82 , a second substrate (i.e., color filter substrate)  80 , a second polarizer  81 . In addition, it further comprises a plurality of spacers  100  located between the first substrate and the second substrate. 
     A transflective liquid crystal display device is to divide each of an existing sub-pixel area into two parts (see  FIG. 2 ,  FIG. 3 ): a transmissive area and a reflective area. Based on whether the thickness of a liquid crystal cell in the transmissive area is the same as that in the reflective area or not, the transflective liquid crystal display device may be divided into two kinds.  FIG. 2  illustrates a display mode that the thicknesses of a liquid crystal cell both in the reflective area and in the transmissive area are uniform (both are λ/2).  FIG. 3  illustrates a display mode that the thickness of a liquid crystal cell in the reflective area (λ/4) is half of the thickness of the liquid crystal cell in the transmissive area (λ/2). Each of  FIG. 2  and  FIG. 3  only illustrate a cross section of one pixel. Herein, λ refers to wavelength. The transflective liquid crystal display device of  FIG. 2  comprises: an upper polarizer  101 , an upper glass substrate  102 , liquid crystals  103 , an upper λ/4 plate  104 , a lower glass substrate  105 , a lower λ/4 plate  106 , and a lower polarizer  107 ; and the transflective liquid crystal display device of  FIG. 3  comprises: an upper polarizer  201 , an upper λ/2 plate  202 , an upper glass substrate  203 , liquid crystals  204 , a lower glass substrate  205 , a lower λ/2 plate  206 , and a lower polarizer  207 . 
     This structure of the transilective liquid crystal display device suffers from the drawbacks: in the transmissive mode, aperture ratio is decreased, and meanwhile display properties are lowered; in the reflective mode, what is realized by a liquid crystal layer is to modulate environmental light which enters the liquid crystal cell after passing through the upper polarizer and a color filter substrate, and therefore available contrast is limited, and image resolution is insufficient. Further, it is difficult to realize that a good display effect is obtained in each of the two modes, and the fabrication process is complicated. 
     SUMMARY 
     The technical problems aimed to be solved by the present invention comprise how to obtain a good display effect in both a reflective mode and a transmissive mode; how to reduce the production costs without decreasing resolution and aperture ratio. 
     For solving the above technical problems, an embodiment of the invention provides a transflective electrochromic liquid crystal display device, comprising a first electrode layer, a second electrode layer and an electrochromic layer, wherein the electrochromic layer is located between the first electrode layer and the second electrode layer, and the first and second electrode layers are adapted to apply an electric field to the electrochromic layer so as to change a color of the electrochromic layer. 
     For example, the second electrode layer, the electrochromic layer and the first electrode layer are located on three different film layers. 
     For example, the second electrode layer, the electrochromic layer and the first electrode layer are located on a same film layer. 
     For example, the display device further comprises a liquid crystal layer, and the second electrode layer, the electrochromic layer and the first electrode layer are located on a same side of the liquid crystal layer. 
     For example, the display device further comprises a first substrate, and the second electrode layer is located between the first substrate and the electrochromic layer. 
     For example, the electrochromic layer comprises at least one pixel region, and the pixel region comprises three horizontally or vertically arranged sub-regions appearing in cyan, carmine and yellow, respectively, in which each of the sub-regions corresponds to a sub-pixel. 
     For example, the display device further comprises a second substrate, and the second substrate is located on an opposite side of the first electrode layer with respect to the liquid crystal layer. 
     For example, the first substrate is a thin film transistor array substrate. 
     For example, the second substrate is a white glass substrate. 
     For example, the display device further comprises a first polarizer, wherein the first polarizer is formed on one side of the first electrode layer, and located between the first electrode layer and the liquid crystal layer. 
     For example, the display device further comprises a second polarizer, and the second polarizer is formed on another side of the second substrate with respect to the liquid crystal layer. 
     For example, the display device further comprises a first polarizer, wherein the first polarizer is located on another side of the first substrate with respect to the liquid crystal layer. 
     For example, the thin film transistor array substrate is of a vertical electric field driving type or a horizontal electric field driving type. 
     For example, the display device further comprises a backlight source, which is located on another side of the first substrate with respect to the liquid crystal layer. 
     An embodiment of the present invention adopts a display device structure in which the array substrate and the color filter substrate are inverted, and a good display effect can be achieved in each of a reflective mode and a transmissive mode. In the reflective mode, an environmental light is directly reflected by an electrochromic layer for display; and in the transmissive mode, an equivalent display effect can be obtained as compared to an existing transmissive liquid crystal display device. 
     In the structure of an embodiment of the present invention, the electrochromic layer is used to replace a color filter, the electrochromic layer is disposed between two electrode layers or disposed on a same film layer as the first electrode layer and the second electrode layer, so that the whole sub-pixel region can act as not only a transmissive area, but also a reflective arca, and resolution and aperture ratio are not decreased. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In order to clearly illustrate the technical solution of the embodiments of the invention, the drawings of the embodiments will be briefly described in the following; it is obvious that the described drawings below are only related to some embodiments of the invention and thus are not limitative of the invention. 
         FIG. 1  is a structural schematic view showing an existing vertical electric field mode liquid crystal display device; 
         FIG. 2  is a structural schematic view of a display device showing the thickness of a liquid crystal cell in a reflective area and the thickness of the liquid crystal cell in a transmissive area are uniform; 
         FIG. 3  is a structural schematic view of a display device showing a display mode that the thickness of a liquid crystal cell in the reflective area is half of the thickness of the liquid crystal cell in the transmissive area; 
         FIG. 4  is a structural schematic view showing a liquid crystal display device of embodiment 1 of the present invention; 
         FIG. 5  is a structural schematic view showing a liquid crystal display device of embodiment 2 of the present invention; and 
         FIG. 6  is a structural schematic view showing a liquid crystal display device obtained by a fabrication method according to embodiment 1 of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Thereinafter, specific embodiments of the present invention will be further described in detail in connection with the accompanied drawings and embodiments. The following embodiments are used to explain the present invention, but not to limit the scope of the present invention. 
     In embodiments of the present invention, an electrochromic material is used. Electrochromic refers to a phenomenon that a stable, reversible color change can occur for optical properties (such as, reflectivity, transmissivity, absorption rate, etc.) of a material under an externally applied electric field. 
     Electrochromic materials can be divided into inorganic electrochromic materials and organic electrochromic materials, and each of them can be formed to be a film. Inorganic electrochromic materials mainly include transition metal oxides or hydrates, such as, WO3 (blue), V2O5 (yellow), NiOx (deep bronze), and etc. Organic electrochromic material, based on structure, mainly include various organic heterocyclic compounds, such as dipyridyl salts, conductive polymers, metal organic polymers and metal phthalocyanines. Organic electrochromic materials can achieve different colors by selecting different substituent groups. For example, with three substances such as biphenyl dicarboxylic acid diethyl ester, diacetybenzene, dimethyl terephthalate and etc. As the electrochromic material, a device gives rise to change according to three primary colors of yellow, cyan and pinkish red, or change according to three colors of red, green, and blue by changing substitute groups on viologen. 
     First Embodiment 
     At first, a substrate configuration according to a first embodiment of the present invention is described with reference to  FIG. 4 . 
     A liquid crystal display device  100  of the first embodiment adopts an inverted structure, i.e., a manner that an array substrate is on an upper side (display surface) with an opposed substrate being on a lower side. The transflective color liquid crystal display device  100  includes a first substrate  10 , a second substrate  20 , a first electrode layer  13 , a second electrode layer  11 , an electrochromic layer  12 , a liquid crystal layer  30 , a first alignment layer  15 , a second alignment layer  22 , a first polarizer  14 , a second polarizer  21 , a spacer or frame  40  and a backlight source  50 . 
     The second substrate  20  is, for example, a white glass substrate, close to the side on which the backlight is provided, and used as an opposed substrate. 
     The first substrate  10  is parallel to the second substrate  20  and opposite to it, and for example, is a thin film transistor (TFT) array substrate, on which a TFT switch circuit structure for controlling each pixel of the liquid crystal display device is formed. The TFT array substrate comprises a plurality of gate lines and data lines, and these gate lines and data lines intersect each other so as to define a plurality of sub-pixel regions arranged in a matrix. Each of the sub-pixel regions comprises a thin film transistor as a switch element, a gate electrode of the thin film transistor is connected to a corresponding gate line, and a drain electrode thereof is, for example, connected to a corresponding data line. 
     The second electrode layer  11 , the first electrode layer  13  and the first substrate  10  each are located on a same side of the liquid crystal layer  30 , and the second electrode layer  11  contacts with the first substrate  10 . The first electrode layer  13  and the second electrode layer  11  are, for example, transparent electrodes. 
     The electrochromic layer  12  functions as a color filter layer (CF), and is disposed between the second electrode layer  11  and the first electrode layer  13  to form a sandwich stack structure. The electrochromic layer  12 , the second electrode layer  11  and the first electrode layer  13  are located on three different film layers. The second electrode layer  11  and the first electrode layer  13  are adapted to apply an electric field to the electrochromic layer  12 , so as to control a color shown by the electrochromic layer  12 . 
     The liquid crystal layer  30  is located between the first alignment layer  15  and the second alignment layer  22 , and the first alignment layer  15  and the second alignment layer can be rubbed to form an alignment structure for liquid crystals. 
     One pixel can be divided, for example, into three sub-pixels, the electrochromic layer  12  comprises at least one pixel region, and the pixel region comprises, for example, three horizontally or vertically arranged sub-pixel regions appearing in cyan, carmine and yellow, respectively (If more abundant colors are desired, a primary element such as orange or the like can be added, and the number of the added primary element is determined according to the required design effect). Each of the sub-pixel regions corresponds to one sub-pixel, and for example, there may be three sub-pixel regions appearing in cyan, carmine and yellow, respectively (e.g., with reference to primary colors of an ink jetting printer). The individual sub-pixels have a horizontal or vertical arrangement structure. 
     The color of the sub-pixel regions is not limited to the combination of cyan, carmine and yellow, and can also be, for example, the combination of red, green and blue. 
     The display principle of the embodiment is introduced as follows. In a reflective mode, three kinds of light of cyan, carmine and yellow reflected by different electrochromic layers are mixed into a variety of colors for color display, luminance control of which is realized by means of changing reflectivity and transmissivity of the electrochromic layers by adjusting the applied electric fields. In a transmissive mode, light emitted from the backlight source  50  is transmitted through different electrochromica layers after modulated by the liquid crystal layer  30 , so as to attain kinds of light in three colors of cyan, carmine and yellow, and these kinds of light are mixed into a variety of colors for color display. 
     In the above embodiment, the first polarizer  14  is located within the liquid crystal cell with respect to the first substrate  10 , and this setting may not change intensity of the reflected light. In another embodiment, the first polarizer can be located outside the liquid crystal cell with respect to the first substrate  10 , for example, attached to an outer side of the first substrate  10 , and this setting is easy to achieve in process. 
     A manufacture procedure of a liquid crystal display device of the embodiment comprises a fabrication process of an array substrate, a fabrication process of an opposed substrate, a cell-assembling process, and etc. Regarding the manufacture procedure, the following description is made with reference to  FIG. 6 .  FIG. 6  is a schematic view only showing one pixel region, but as would be understandable by those skilled in the art, other pixel regions can be fabricated in the same steps. 
     Firstly, an array substrate is fabricated. 
     1. A glass substrate  301 , for example, is prepared as a base substrate. The glass substrate is cleaned by a process, such as, water cleaning, acid cleaning, ultrasound wave cleaning, air knife, etc., to meet subsequent production requirements. 
     2. A metal thin film is firstly deposited on the glass substrate  301 , and is patterned by a photolithography process to obtain a metal electrode wiring  3021 ; and then, a transparent conductive material (such as, indium tin oxide (ITO), indium zinc oxide (IZO), tin oxide, etc.) is deposited on the glass substrate  301  to obtain a transparent conductive film, and the transparent conductive film is patterned by a photolithography process to form a first electrode layer  3022 . Next, an insulating layer is obtained by using a chemical vapor deposition (CVD) method so as to cover the metal electrode wiring  3021  and the first electrode layer  3022 . 
     3. By using a screen printing technology, a printing technology or the like, three electrochromic materials of, such as, cyan, carmine, or yellow are produced on the first electrode layer  3022 , so as to obtain an electrochromic layer. Next, an insulating layer is formed on the electrochromic layer by using a chemical vapor deposition method. 
     4. A metal thin film is deposited and is patterned by using a photolithography process, so as to obtain a metal electrode wiring  3041  as a data line; and then, a transparent conductive material (such as, ITO, IZO, tin oxide, or the like.) is deposited to accordingly obtain a transparent conductive film, and the transparent conductive film is patterned by using a photolithography process, so as to form a second electrode layer  3042 . The second electrode layer  3042  functions as a pixel electrode, and for example, can comprise a slit or be formed to be a comb-like electrode. 
     5. A thin film transistor  305  is manufactured as a switch element of a pixel region. The thin film transistor comprises a gate insulating film, an active layer, a source electrode, a drain electrode. For example, the drain electrode of the thin film transistor  305  is connected to the metal electrode wiring  3041 , and the source electrode is connected to the second electrode layer  3042 . 
     6. A metal thin film is deposited, and patterned by using a photolithography process, so as to obtain a metal electrode wiring  306  and a gate electrode of the thin film transistor. The metal wiring  306  as a gate line is connected to the gate electrode of the thin film transistor. 
     7. A transparent conductive material is deposited to obtain a transparent conductive film, and the transparent conductive film is patterned by using a photolithography process so as to obtain a common electrode  307 . The common electrode  307 , for example, can also comprise a slit or be formed to be a comb-like electrode, and acts to form a driving electric field for liquid crystals in cooperation with the second electrode layer (pixel electrode)  3042  after it is energized. 
     8. On a top surface of the above structure, a polarizer (not shown in  FIG. 6 ) is formed. Up to here, the array substrate is obtained. 
     9. A test is performed on the array substrate. 
     Next, the opposed substrate is prepared. 
     10. The opposed substrate  311 , such as, a white glass substrate, is prepared. 
     Next, the cell-assembling process is performed. 
     11. Alignment layers  308 ,  310  are coated on the surfaces of the array substrate and the opposed substrate  311 , respectively, and a rubbing alignment process is performed on the alignment layers. 
     12. Sealant (not shown) is coated on a surface of one of the array substrate and the opposed substrate, liquid crystals  309  are drop onto another, and then the two are disposed opposite to each other to form a liquid crystal cell. Subsequently, an ultraviolet solidification and/or thermal solidification are performed so as to obtain a liquid crystal panel. 
     13. The resultant liquid crystal cell is cut so as to obtain a single liquid crystal panel. 
     14. A polarizer is attached on the outside of the opposed substrate, and a driving circuit and a backlight source are added. 
     In the embodiment, the polarizer on the array substrate is formed within the liquid crystal cell with respect to the base substrate  301 . In another embodiment, the polarizer on the array substrate may be formed outside the base substrate  301 , so that the polarizer may be attached on the array substrate, for example, after cutting as the foregoing step  14 . 
     The present embodiment can be applied, for example, to an FFS mode that liquid crystal molecules are rotated in a plain in a horizontal electric field driving mode. The thin film transistor  305  controls the electrochromic layer and the liquid crystal layer simultaneously. 
     However, in the embodiment, the circuit structure for driving the liquid crystal molecules is not limited to the case where the array substrate comprises a combination of the above second electrode layer  3042  and the common electrode  307 . If necessary, in the embodiment, for example, the pixel electrode and the common electrode can also be formed on the same plane to attain an In-plane Switch (IPS) mode of a horizontal electric field driving type; alternatively, the pixel electrode is formed on the array substrate, and the common electrode is formed on the opposed substrate, so as to obtain, such as, a Twisted Nematic (TN) mode of a vertical electric field driving type. In addition, the electrochromic layer and the liquid crystal layer can be driven by using different switch circuits. The scope of the present invention is not limited by the driving manner of liquid crystals. 
     Second Embodiment 
     The structure and manufacture process of a second embodiment are substantially the same as those of the first embodiment. A liquid crystal display device  200  of the second embodiment comprises: a first substrate  10 ; a second electrode layer  11 ; an electrochromic layer  12 ; a first electrode layer  13 ; a first polarizer  14 ; a first alignment layer  15 ; a second substrate  20 ; a second polarizer  21 ; a second alignment layer  22 ; a liquid crystal layer  30 ; a spacer or sealant  40 ; and a background source  50 . The first and second embodiments differ in that the structure of the second embodiment is adjusted as follows. 
     As shown in  FIG. 5 , the electrochromic layer  12 , the first electrode  13  and the second electrode  11  are transformed, from a top-and-bottom structure, to be located on a same film layer and are disposed adjacent to each other, and the electrochromic layer  12  is located between the first electrode  13  and the second electrode  11 . The second electrode layer  11  and the first electrode layer  13  are adapted to apply an electric field to the electrochromic layer  12 , so as to control a color shown by the electrochromic layer  12 . The heights of the second electrode layer  11  and the first electrode layer  13  can be changed if necessary, so as to achieve a proper effect. 
     Likewise, in the above embodiment, the first polarizer  14  is located within a liquid crystal cell with respect to the first substrate  10 , and this setting may not change intensity of the reflected light. In another embodiment, the first substrate  10  can be located outside the liquid crystal cell with respect to the first substrate  10 , for example, attached to an outer side of the first substrate  10 , and this setting is easy to achieve in process. 
     The manufacture method of the present embodiment is similar to that of the first embodiment, but differs in that, the electrochromic layer  12 , the first electrode  13  and the second electrode  11  are provided on the same film layer and are disposed adjacent to each other. 
     The present embodiment can be applied to a liquid crystal in-plane switch (IPS) mode of a horizontal electric field driving type. Likewise, in the embodiment, the driving manner of liquid crystals can also be replaced with an FFS mode of the horizontal electric field type, a TN mode of a vertical electric field driving type, etc. 
     The display principle of the present embodiment is similar to that of the first embodiment. In a reflective mode, kinds of light of primary colors, such as light of cyan, carmine and yellow, are reflected by different electrochromic layers, and are mixed into a variety of colors for color display, the luminance control of which is realized by means of changing reflectivity and transmissivity of the electrochromic layers by adjusting the applied electric fields. In a transmissive mode, light from a backlight is transmitted through different electrochromic layers after modulated, so as to attain kinds of light in three colors of cyan, carmine and yellow, and these kinds of light are mixed into a variety of colors for color display. 
     The above embodiments are merely used to illustrate the present invention, but not to limit the present invention. Various modifications and variations can be made by those skilled in the related technical field without departing from the spirit and scope of the present invention. Therefore, all of equivalent technical solutions also come within the scope of the present invention, and the protection scope of the present invention should be defined by claims.