Patent Publication Number: US-2010108232-A1

Title: Method for fabricating electrowetting displays

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 61/111,614, filed Nov. 5, 2008, which is incorporated by reference herein in its entirety for any purpose. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a method for fabricating a display, and more particularly to a method for fabricating an electrowetting display. 
     2. Description of the Related Art 
     The first electrowetting display was developed by Robert A. Hayes and B. J. Feenstra in 2003. Its color transformation is achieved by applying various voltages to control the contact angle between oily medium and hydrophobic insulation layer. The display possesses a reflection index over 35% and a contrast index over 15, similar to paper (reflection index of 60% and contrast index of 15). Additionally, its operation voltage is less than 20V and response time is merely 12 ms (on-state) and 13 ms (of-state), respectively, with superior property. The electrowetting display is composed of a conductive liquid (water), a color oily medium, a hydrophobic insulation layer and transparent electrodes, having a simple fabrication. Compared to liquid crystal displays or electrophoresis displays, the electrowetting display possesses a potential for application in flexible display fabrication due to without an alignment process and microencapsulation. 
     However, due to simultaneous use of liquid mediums such as color oily medium and water medium, the electrowetting display should be assembled in water to seal such liquids thereinside. 
     BRIEF SUMMARY OF THE INVENTION 
     One embodiment of the invention provides a method for fabricating an electrowetting display comprising forming a plurality of hydrophilic ribs on a first substrate, forming a retaining wall surrounding the hydrophilic ribs, filling a non-polar solution within the hydrophilic ribs, forming a polar solution over the non-polar solution and the hydrophilic ribs within the retaining wall, providing a second substrate and assembling the first substrate and the second substrate. 
     A detailed description is given in the following embodiments with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawing, wherein: 
         FIGS. 1A-1C  show cross-sectional views of a method for fabricating an electrowetting display according to an embodiment of the invention. 
         FIGS. 2A-2C  show cross-sectional views of a method for fabricating an electrowetting display according to an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The following description is of the mode of carrying out the invention. This description is made for the purpose of illustrating the general principles of the invention and should not be taken in a limiting sense. The scope of the invention is determined by reference to the appended claims. 
     According to an embodiment of the invention, a method for fabricating an electrowetting display is shown in  FIGS. 1A-1C . 
     Referring to  FIG. 1A , a first substrate  10  is provided. The first substrate  10  may comprise glass, polymer materials or metal. A first electrode  12  is then formed on the first substrate  10 . Next, a dielectric layer  14  is formed on the first electrode  12 . The dielectric layer  14  may comprise silicon oxide, silicon nitride, tantalum oxide, lead zirconate titanate (PZT), barium strontium titanate (BST), barium titanate (BTO) or polyvinylidene difluoride (PVDF). A hydrophobic layer  16  is then formed on the dielectric layer  14 . The hydrophobic layer  16  may comprise fluoro-containing or chloro-containing hydrophobic polymer materials or octadecyltrichlorosilane (OTS). Next, a plurality of hydrophilic ribs  18  are formed on the hydrophobic layer  16 . The hydrophilic ribs  18  may comprise photoresist, thermosetting resin or photosetting resin. The hydrophilic ribs  18  are isolated from one another and each of them corresponds to a sub-pixel area. A retaining wall  20  is then formed to surround the hydrophilic ribs  18 . The retaining wall  20  may comprise photoresist, thermosetting resin or photosetting resin. The retaining wall  20  may have at least one breach (not shown) of about 0.1 mm-5 mm. The retaining wall  20  may have a thickness of about 10 μm-100 μm. Next, a non-polar solution  22  is filled within the hydrophilic ribs  18  by, for example, inkjet printing, dip coating, slide coating, slot coating or blade coating. The non-polar solution  22  may comprise dye or pigment. A polar solution  24  is then formed over the non-polar solution  22  and the hydrophilic ribs  18  within the retaining wall  20  by, for example, inkjet printing, dip coating, slide coating, slot coating or blade coating. The polar solution  24  may comprise water, sodium chloride aqueous solution or potassium chloride aqueous solution. Next, a second substrate  26  is provided. The second substrate  26  may comprise glass, polymer materials or metal. A second electrode  28  is then formed on the second substrate  26 . Next, a frame seal  30  is coated on the second electrode  28 . The frame seal  30  may have at least one breach (not shown) of about 0.1 mm-5 mm. Optionally, the frame seal  30  is coated on the hydrophobic layer  16  over the first substrate  10 , as shown in  FIG. 1B . The first substrate  10  and the second substrate  26  are then assembled. After assembling, the frame seal  30  is cured. An electrowetting display  40  is then prepared, as shown in  FIG. 1C . In  FIG. 1C , the frame seal  30  is adjacent to the retaining wall  20 . Optionally, the frame seal  30  is on the retaining wall  20  (not shown). 
     According to an embodiment of the invention, a method for fabricating an electrowetting display is shown in  FIGS. 2A-2C . 
     Referring to  FIG. 2A , a first substrate  100  is provided. The first substrate  100  may comprise glass, polymer materials or metal. A first electrode  120  is then formed on the first substrate  100 . Next, a dielectric layer  140  is formed on the first electrode  120 . The dielectric layer  140  may comprise silicon oxide, silicon nitride, tantalum oxide, lead zirconate titanate (PZT), barium strontium titanate (BST), barium titanate (BTO) or polyvinylidene difluoride (PVDF). A hydrophobic layer  160  is then formed on the dielectric layer  140 . The hydrophobic layer  160  may comprise fluoro-containing or chloro-containing hydrophobic polymer materials or octadecyltrichlorosilane (OTS). Next, a plurality of hydrophilic ribs  180  are formed on the hydrophobic layer  160 . The hydrophilic ribs  180  may comprise photoresist, thermosetting resin or photosetting resin. The hydrophilic ribs  180  are isolated from one another and each of them corresponds to a sub-pixel area. A retaining wall  200  is then formed to surround the hydrophilic ribs  180 . The retaining wall  200  may comprise photoresist, thermosetting resin or photosetting resin. The retaining wall  200  may have at least one breach (not shown) of about 0.1 mm-5 mm. The retaining wall  200  may have a thickness of about 10 μm-100 μm. Next, a non-polar solution  220  is filled within the hydrophilic ribs  180  by, for example, inkjet printing, dip coating, slide coating, slot coating or blade coating. The non-polar solution  220  may comprise dye or pigment. A polar solution  240  is then formed over the non-polar solution  220  and the hydrophilic ribs  180  within the retaining wall  200  by, for example, inkjet printing, dip coating, slide coating, slot coating or blade coating. The polar solution  240  may comprise water, sodium chloride aqueous solution or potassium chloride aqueous solution. Next, a second substrate  260  is provided. The second substrate  260  may comprise glass, polymer materials or metal. A second electrode  280  is then formed on the second substrate  260 . Next, a second retaining wall  320  is formed on the second electrode  280 . The second retaining wall  320  may comprise photoresist, thermosetting resin or photosetting resin. The second retaining wall  320  may have at least one breach (not shown) of about 0.1 mm-5 mm. The second retaining wall  320  may have a thickness of about 10 μm-100 μm. A second polar solution  340  is then formed within the second retaining wall  320  by, for example, inkjet printing, dip coating, slide coating, slot coating or blade coating. The second polar solution  340  may comprise water, sodium chloride aqueous solution or potassium chloride aqueous solution. Optionally, the second polar solution  340  is formed within the second retaining wall  320  after the surface of the second substrate  260  is treated. Next, a frame seal  300  is coated on the second electrode  280 . The frame seal  300  may have at least one breach (not shown) of about 0.1 mm-5 mm. Optionally, the frame seal  300  is coated on the hydrophobic layer  160  over the first substrate  100 , as shown in  FIG. 2B . The first substrate  100  and the second substrate  260  are then assembled. After assembling, the frame seal  300  is cured. An electrowetting display  400  is then prepared, as shown in  FIG. 2C . In  FIG. 2C , the frame seal  300  is adjacent to the second retaining wall  320 . 
     When an electrowetting display is prepared using the method provided by an embodiment of the invention, assembly in water is not required, thus an accurate alignment and large-area production are processed. 
     While the invention has been described by way of examples and in terms of embodiment, it is to be understood that the invention is not limited thereto. To the contrary, it is intended to cover various modifications and similar arrangements (as would be apparent to those skilled in the art). Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.