Patent Publication Number: US-2013241816-A1

Title: Electrophoretic display apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the priority benefit of Taiwan application serial no. 101109090, filed on Mar. 16, 2012. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention generally relates to a display apparatus, and more particularly, to an electrophoretic display apparatus. 
     2. Description of Related Art 
     In recent years, since various display techniques continue to flourish, after ceaselessly researching and developing, many display products such as electrophoretic display, liquid crystal display (LCD), plasma display, organic light-emitting diode display (OLED display) have been gradually commercialized and applied in display apparatuses with various sizes and areas. With the growing popularity of portable electronic products, flexible displays such as electronic paper (e-paper), e-books (e-book), and so on have been gradually attractive by the customers on the market. 
     In general speaking, the e-paper and the e-book are based on electrophoretic display technique for the display purpose. Taking the e-book with black and white displayed colors as an example, the display medium thereof mainly includes a black electrophoretic liquid and white charged particles dispersed in the black electrophoretic liquid. After applying voltages on the medium, the white charged particles are driven to migrate so that each pixel respectively displays black color, white color or gray color with a gray level. 
     In the prior art, the electrophoretic display mostly utilizes light reflection of an external light source to achieve display purpose, while through driving the white charged particles dispersed in the electrophoretic liquid by applied voltages, each pixel can display with a required gray level. For expanding the application of the electrophoretic display, a color filter film is fabricated on the display medium and the color filter film is fixed on the display medium through an adhesive layer. At the time, after the external incident light passes through the color filter film, the external light is reflected by the white charged particles in the display medium and then penetrates the color filter film for displaying. That is to say, in the light transmission path, the light penetrates the color filter film twice, so that the efficiency of light transmission is degraded a lot and the colorful saturation and luminance performance of the electrophoretic display is affected. 
     SUMMARY OF THE INVENTION 
     Accordingly, the invention is directed to an electrophoretic display apparatus able to have better display luminance and colorful saturation in addition to having energy-saving effect. 
     The embodiment of the invention provides an electrophoretic display apparatus, which includes a substrate and an electrophoretic display film. The substrate has a plurality of pixel units, in which each of the pixel units has a transparent region and a reflective region and each of the pixel units includes a pixel electrode and a reflective layer. The pixel electrode is located in the transparent region and the reflective region. The reflective layer is disposed on the pixel electrode and located in the reflective region. The electrophoretic display film is disposed on the substrate and includes a common electrode and a plurality of microcapsules disposed between the common electrode and the pixel units, in which each of the microcapsules includes a plurality of black electrophoretic particles, and an arrangement of the black electrophoretic particles is controlled by a driving voltage applied between the pixel electrode of each the pixel unit and the common electrode of the electrophoretic display film. 
     In an embodiment of the present invention, the above-mentioned electrophoretic display apparatus further includes a binder disposed between the common electrode and the substrate, in which the microcapsules are distributed in the binder. 
     In an embodiment of the present invention, the above-mentioned each of the microcapsules further includes an electrophoretic liquid and the black electrophoretic particles are distributed in the electrophoretic liquid. 
     In an embodiment of the present invention, the above-mentioned each of the microcapsules further includes a microcup structure and an electrophoretic liquid, the black electrophoretic particles are distributed in the electrophoretic liquid and the electrophoretic liquid and the black electrophoretic particles are enclosed in the microcup structure. 
     In an embodiment of the present invention, the above-mentioned electrophoretic display apparatus further includes a color filter film disposed on the common electrode of the electrophoretic display film. 
     In an embodiment of the present invention, the above-mentioned electrophoretic display apparatus further includes a transparent optical adhesive layer disposed between the binder of the electrophoretic display film and the substrate. 
     In an embodiment of the present invention, the above-mentioned electrophoretic display apparatus further includes a color filter film disposed between the binder of the electrophoretic display film and the substrate. 
     In an embodiment of the present invention, the above-mentioned electrophoretic display apparatus further includes a transparent optical adhesive layer disposed between the color filter film and the binder of the electrophoretic display film. 
     In an embodiment of the present invention, when a high-frequency AC voltage is applied between each the pixel electrode and the common electrode, the black electrophoretic particles are in a vertical arrangement so that a light penetrates the transparent regions to enter the electrophoretic display film for displaying. 
     In an embodiment of the present invention, when a low-frequency AC voltage or a DC voltage is applied between each the pixel electrode and the common electrode, the black electrophoretic particles are dispersedly arranged in the transparent region and the reflective region of each the pixel unit so that a light is unable to penetrate the electrophoretic display film. 
     In an embodiment of the present invention, a material of the pixel electrode includes indium oxide (IO), tin oxide (TO), indium tin oxide (ITO) or indium zinc oxide (IZO). 
     In an embodiment of the present invention, a material of the reflective layer includes metal or alloy. 
     In an embodiment of the present invention, a material of the reflective layer includes titanium dioxide. 
     Based on the description above, the pixel unit of the embodiment of the invention has a transparent region and a reflective region, in which the pixel electrode is disposed in the transparent region and the reflective region and the reflective layer is disposed on the pixel electrode and located in the reflective region. In this way, the arrangement of the black electrophoretic particles can be controlled by applying a driving voltage between the pixel electrode and the common electrode, so that a light (for example, a backlight source) can directly penetrate the pixel electrode located at the transparent region for displaying; or the light (for example, an external light) can penetrate the electrophoretic display film first and then is reflected by the reflective layer for displaying. In addition, since the light directly penetrating the transparent region has better optical performance of colorful saturation and display luminance, it can reinforce the optical performance of the light after the reflection and the electrophoretic display apparatus of the embodiment of the invention has better display luminance and colorful saturation. 
     Other objectives, features and advantages of the present invention will be further understood from the further technological features disclosed by the embodiments of the present invention wherein there are shown and described preferred embodiments of this invention, simply by way of illustration of modes best suited to carry out the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic cross-sectional diagram of an electrophoretic display apparatus according to an embodiment of the invention. 
         FIG. 2  is a schematic cross-sectional diagram of another electrophoretic display apparatus according to an embodiment of the invention. 
         FIG. 3  is a schematic cross-sectional diagram of yet another electrophoretic display apparatus according to an embodiment of the invention. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
       FIG. 1  is a schematic cross-sectional diagram of an electrophoretic display apparatus according to an embodiment of the invention. Referring to  FIG. 1 , an electrophoretic display apparatus  100   a  includes a substrate  110  and an electrophoretic display film  120 . 
     In more details, the substrate  110  has a plurality of pixel units  112  (only three ones are shown in  FIG. 1 ), in which each of the pixel units  112  has a transparent region  113   a  and a reflective region  113   b.  Each of the pixel units  112  includes a pixel electrode  114  and a reflective layer  116 , in which the pixel electrode  114  is located in the transparent region  113   a  and the reflective region  113   b,  and the reflective layer  116  is disposed on the pixel electrode  114  and located in the reflective region  113   b.  That is to say the reflective region  113   b  is just the position where the reflective layer  116  is located at. The part of the pixel electrode  114  uncovered by the reflective layer  116  is the position of the transparent region  113   a.    
     It should be noted that the substrate  110  of the embodiment is, for example, an active array substrate and each of the pixel units  112  further includes an active device (not shown), in which the active device is electrically connected to the pixel electrode  114  and located under the reflective layer  116 . The material of the pixel electrode  114  is, for example, indium oxide (IO), tin oxide (TO), indium tin oxide (ITO) or indium zinc oxide (IZO), which the invention is not limited to. The material of the reflective layer  116  can be metal, for example, aluminium or alloy such as aluminium alloy. The material of the reflective layer  116  can certainly be a material with high reflectivity, for example, titanium dioxide. The above-mentioned materials of the reflective layer  116  are examples only, which the invention is not limited to. In fact, as long as a material has reflection function, the material can be used for the reflective layer  116  and belongs to the technical scheme adopted by the invention without departing from the claimed scope of the invention. 
     The electrophoretic display film  120  is disposed on the substrate  110  and includes a common electrode  122  and a plurality of microcapsules  126 . In more details, the microcapsules  126  are disposed between the common electrode  122  and the pixel units  112 . Each of the microcapsules  126  includes an electrophoretic liquid  126   a  and a plurality of black electrophoretic particles  126   b,  in which the black electrophoretic particles  126   b  are distributed in the electrophoretic liquid  126   a  and the black electrophoretic particles  126   b  are, for example, opaque black charged particles. The electrophoretic display film  120  further includes a binder  124  disposed between the common electrode  122  and the substrate  110  and the microcapsules  126  are distributed in the binder  124 . 
     In addition, the electrophoretic display apparatus  100   a  of the embodiment further includes a color filter film  130   a  and a transparent optical adhesive layer  140   a.  The color filter film  130   a  is disposed on the common electrode  122  of the electrophoretic display film  120 , and the color filter film  130   a  includes a plurality of red filter units  132   a  (only one is shown in  FIG. 1 ), a plurality of green filter units  134   a  (only one is shown in  FIG. 1 ) and a plurality of blue filter units  136   a  (only one is shown in  FIG. 1 ). The color filter film  130   a  is configured for the electrophoretic display apparatus  100   a  to display colorful image so as to expand the application scope thereof. The transparent optical adhesive layer  140   a  is disposed between the binder  124  of the electrophoretic display film  120  and the substrate  110 , in which the electrophoretic display film  120  is fixed onto the substrate  110  through the transparent optical adhesive layer  140   a.    
     In particular in the embodiment, the arrangement of the black electrophoretic particles  126   b  is controlled by a driving voltage applied between the pixel electrode  114  of each of the pixel units  112  and the common electrode  122  of the electrophoretic display film  120 . In more details, when a high-frequency AC voltage is applied between each the pixel electrode  114  and the common electrode  122 , the black electrophoretic particles  126   b  are in a vertical arrangement (referring to the arrangement of the black electrophoretic particles  126   b  under the red filter unit  132   a  in  FIG. 1 ) so that a light L 1  can penetrate the transparent regions  113   a  to enter the electrophoretic display film  120  for displaying. Meanwhile, another light L 2  penetrates the electrophoretic display film  120  and then is reflected by the reflective layer  116  of the substrate  110  for displaying. At the time, the pixel unit  112  is in bright optical state. 
     When a low-frequency AC voltage or a DC voltage is applied between each the pixel electrode  114  and the common electrode  122 , the black electrophoretic particles  126   b  are dispersedly arranged in the transparent region  113   a  and the reflective region  113   b  of each the pixel unit  112  so that a light is unable to penetrate the electrophoretic display film (referring to the arrangement of the black electrophoretic particles  126   b  under the green filter unit  134   a  or under the blue filter unit  136   a  in  FIG. 1 ) so that a light L 3  and another light L 4  are unable to penetrate the electrophoretic display film  120  for displaying. At the time, the pixel unit  112  is in dark optical state. It should be noted that the above-mentioned lights L 1  and L 3  are the lights come from a backlight source (not shown), while L 2  and L 4  are outside ambient lights. 
     Since the light L 1  directly penetrating the transparent region  113   a  has better optical performance of colorful saturation and display luminance, it can reinforce the optical performance of the light L 2  after the reflection. Hence in comparison with the prior art where the electrophoretic display apparatus produces displaying by the reflection of light only, the electrophoretic display apparatus  100   a  of the embodiment has better display luminance and colorful saturation. In short, the electrophoretic display apparatus  100   a  of the embodiment achieves the goal of controlling the distribution of the black electrophoretic particles  126   b  through a transflective design and the driving voltage so as to improve the poor optical performance of the conventional electrophoretic display where the displaying is produced by the reflection of light only and the colorful saturation and the luminance are insufficient. In addition, when the intensity of the outside ambient light (for example, the light L 2  or L 4 ) is high enough, the backlight source (for example, the light L 1  or L 3 ) can be shut off to save energy. 
       FIG. 2  is a schematic cross-sectional diagram of another electrophoretic display apparatus according to an embodiment of the invention. It should be noted the component notations and partial details of the structures hereinafter provided in the embodiments can be the same as or similar to the previous embodiment, wherein the same notations represent the same or similar components while the repeated same details are omitted, which can refer to the previous embodiment. 
     Referring to  FIG. 2 , the electrophoretic display apparatus  100   b  of the embodiment is similar to the electrophoretic display apparatus  100   a  of the above-mentioned embodiment except that each microcapsule  126 ′ of the electrophoretic display film  120 ′ includes an electrophoretic liquid  126   a,  a plurality of black electrophoretic particles  126   b  and a microcup structure  128 , in which the microcup structure  128  is joined between the transparent optical adhesive layer  140   a  and the common electrode  122  so as to enclose the electrophoretic liquid  126   a  and the black electrophoretic particles  126   b  into the microcup structure  128 . 
       FIG. 3  is a schematic cross-sectional diagram of yet another electrophoretic display apparatus according to an embodiment of the invention. It should be noted the component notations and partial details of the structures hereinafter provided in the embodiments can be the same as or similar to the previous embodiment, wherein the same notations represent the same or similar components while the repeated same details are omitted, which can refer to the previous embodiment. 
     Referring to  FIG. 3 , the electrophoretic display apparatus  100   c  of the embodiment is similar to the electrophoretic display apparatus  100   a  of the above-mentioned embodiment except that the disposing positions of the color filter film  130   b  and the transparent optical adhesive layer  140   b  are different from the disposing positions of the color filter film  130   a  and the transparent optical adhesive layer  140   a.  In more details, the color filter film  130   b  is disposed between the binder  124  of the electrophoretic display film  120  and the substrate  110  and covers the reflective layer  116  and the pixel electrode  114 . The transparent optical adhesive layer  140   b  is disposed between the color filter film  130   b  and the binder  124  of the electrophoretic display film  120  so as to fix the electrophoretic display film  120  onto the color filter film  130   b.    
     In summary, the pixel unit of the embodiment of the invention has a transparent region and a reflective region, in which the pixel electrode is disposed in the transparent region and the reflective region and the reflective layer is disposed on the pixel electrode and located in the reflective region. In this way, the arrangement of the black electrophoretic particles can be controlled by applying a driving voltage between the pixel electrode and the common electrode, so that a light (for example, a backlight source) can directly penetrate the pixel electrode located at the transparent region for displaying; or the light (for example, an external light) can penetrate the electrophoretic display film first and then is reflected by the reflective layer for displaying. In addition, since the light directly penetrating the transparent region has better optical performance of colorful saturation and display luminance, it can reinforce the optical performance of the light after the reflection and the electrophoretic display apparatus of the embodiment of the invention has better display luminance and colorful saturation. 
     It will be apparent to those skilled in the art that the descriptions above are several preferred embodiments of the invention only, which does not limit the implementing range of the invention. Various modifications and variations can be made to the structure of the invention without departing from the scope or spirit of the invention. The claim scope of the invention is defined by the claims hereinafter.