Patent Publication Number: US-2011068492-A1

Title: 3d curved display devices, fabrication methods thereof and plastic display panels

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This Application claims priority of Taiwan Patent Application No. 98131891, filed on Sep. 22, 2009, the entirety of which is incorporated by reference herein. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a display device and more particularly to a 3D curved display device and a fabrication method thereof. 
     2. Description of the Related Art 
     Recently, flexible display devices have been used for curved display effect to enhance viewing pleasure of users, along with other conventional display devices. Most conventional curved display devices are two-dimensional (2D) curved displays. For example, a display panel may be formed from glass substrate processed to form a curved display with a small curvature or a display panel may be formed from plastic substrates to enhance display curvature. 
     US Publication No. 2008/0151089A1 discloses a semi-sphere type image sensor, which is fabricated by forming several element segments in a substrate, wherein the element segments are arranged together. While the semi-sphere type image sensor may be applied in display devices, smooth curves for viewing cannot be achieved due to the intersecting areas. Also, display quality is poor. 
     Meanwhile, International Patent No. WO 2006/035786A1 discloses a tensible array element. A plurality of sensors is fabricated on nodes of a meshed flexible substrate, such that a tensible character is provided and the sensors at the nodes and the signal lines of the array element are not deformed when stressed. However, the meshed flexible substrate needs a large empty area. Thus, the tensible array element is not suitable for display devise requiring a large area for pixel electrodes. 
     The above mentioned devices for fabricating curved elements can not achieve display devices with 3D curved effect. Therefore, a 3D curved display device and fabrication methods thereof are desired to achieve a stereo-image display effect and increased display device applications. 
     BRIEF SUMMARY OF THE INVENTION 
     The invention provides a method for forming a 3D curved display device. First, a first substrate is provided and then a first electrode layer is formed on the first substrate. A plurality of spacers is formed on the first electrode layer. A display medium layer is formed over the first substrate, covering the spacers and the first electrode layer. Then, a second electrode layer is formed on the display medium layer. A first mold and a pressure source are provided to sandwich the first substrate to the second electrode layer. Then, a molding process is performed to compress the first substrate, the first electrode layer, the spacers, the display medium layer and the second electrode layer to form a 3D curved display device, wherein the first substrate, the first electrode layer and the second electrode layer are made of plastic or elastic materials, and the display medium layer has a first thickness before the molding process. The first thickness is greater than a height of the spacers. 
     The invention further provides another method for forming a 3D curved display device. First, a first mold is provided and a first electrode layer is formed on the first mold. Then, a first substrate is provided and a second electrode layer is formed on the first substrate. A plurality of spacers is formed on the second electrode layer. A display medium layer is formed on the spacers and the second electrode layer. A pressure source is disposed over the first substrate. Then, a molding process is performed to compress the first substrate, the second electrode layer, the spacers, the display medium layer and the first electrode layer to form a 3D curved display device, wherein the first substrate, the first electrode layer and the second electrode layer are made of plastic or elastic materials, and the display medium layer has a first thickness before the molding process. The first thickness is greater than a height of the spacers. 
     The invention further provides a 3D curved display device. The 3D curved display device comprises a first substrate. A first electrode layer is disposed on the first substrate. A display medium layer is disposed over the first electrode layer. A plurality of spacers is disposed in the display medium layer. In addition, a second electrode layer is disposed on the display medium layer. In the 3D curved display device, the first substrate, the first electrode layer and the second electrode layer are made of plastic or elastic materials, and the display medium layer has a thickness equal to a height of the spacers. 
     The invention further provides a plastic display panel. The plastic display panel comprises a first substrate. A first electrode layer is disposed on the first substrate. A plurality of spacers is disposed on the first electrode layer. A display medium layer is disposed over the spacers and the first electrode layer. A second electrode layer is disposed on the display medium layer. A second substrate disposed on the second electrode layer. A protection layer or a releasing layer is optionally disposed on the second electrode layer before the second substrate is disposed. In the plastic display panel, the first substrate, the first electrode layer and the second electrode layer are made of plastic or elastic materials, and the display medium layer has a thickness equal to a height of the spacers. 
     A detailed description is given in the following embodiments with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein: 
         FIGS. 1A-1D  show schematic cross sections of a method for fabricating a 3D curved display device according to an embodiment of the invention; 
         FIGS. 2A-2E  show schematic cross sections of a method for fabricating a 3D curved display device according to another embodiment of the invention; 
         FIGS. 3A-3D  show schematic cross sections of a method for fabricating a 3D curved display device according to further another embodiment of the invention; and 
         FIGS. 4A-4C  show schematic cross sections of a method for fabricating a 3D curved display device according to further another embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The following description is of the contemplated mode of carrying out the invention. The description is provided for illustrating the general principles of the invention and is not meant to be limiting. The scope of the invention is best determined by reference to the appended claims. 
     An embodiment of the invention utilizes plastic or elastic materials as substrates and electrode layers of displays. In addition, a plastic display medium layer is disposed between an upper substrate and a lower substrate and also between an upper electrode layer and a lower electrode layer. The display medium layer includes a plurality of display medium microcapsules and a polymer filled between the display medium microcapsules, wherein the polymer may be curable resin. The above mentioned materials are compressed at a suitable temperature and a suitable pressure in a molding process and then treated by a curing process to form a 3D curved display device. 
     The 3D curved display device of an embodiment of the invention can display 3D images in 3 directions, i.e. x, y and z directions. A curved stereo-shape of the 3D curved display device matchs a surface stereo-shape of a mold used for the molding process, such that the 3D curved display device can have any 3D curved shape, such as a concave shape, a convex shape or a complex curved surface composed of concave and convex shapes. The 3D curved display device can be for example a face mold of a doll which can change images, a utensil surface which can change patterns and colors or can be applied to medical treatment for displaying stereo-structures of the human body, for example a head or an organ in the cranium. 
     Referring to  FIGS. 1A-1D , cross sections of a method for fabricating a 3D curved display device according to an embodiment of the invention are shown. As shown in  FIG. 1A , first a plastic display panel  100  is provided. The plastic display panel  100  includes an upper substrate  10  and an upper electrode layer  12  is formed on the upper substrate  10 . A lower substrate  20  is disposed opposite to the upper substrate  10  and a lower electrode layer  18  is formed on the lower substrate  20 . A plurality of spacers and a display medium layer  16  are formed between the upper electrode layer  12  and the lower electrode layer  18 . The display medium layer  16  has a thickness H 1  greater than a height D of the spacers. In an embodiment, the difference E between the thickness H 1  and the height D is about 0.3 to 0.5 times the height D, i.e. the thickness H 1  is about 1.3 to 1.5 times the height D. 
     The upper substrate  10  and the lower substrate  20  may be plastic or elastic materials, for example poly(ethylene terephthalate) (PET), poly(ether sulfone) (PES), poly(ethylene 2,6-naphthalate) (PEN), poly carbonate (PC), polyimide (PI), poly(phenylene sulfone) (PPSU), natural rubber, silicone, or polyurethane (PU), or the derivatives based on the above mentioned materials or combinations of the above mentioned materials. 
     In an embodiment, the upper substrate  10  and/or the lower substrate  20  may be a transparent substrate. 
     The upper electrode layer  12  and the lower electrode layer  18  may be plastic or elastic materials, for example poly(3,4-ethylene dioxythiophene) (PEDOT), polyaniline (PANI), mixtures of polymer with nano-carbon tubes (CNTs) or mixtures of polymer with metal fibers. Compared with the material of the general transparent electrode layer, i.e. indium tin oxide (ITO), the materials of the upper electrode layer  12  and the lower electrode layer  18  can permit greater deformation. Moreover, the upper electrode layer  12  and the lower electrode layer  18  can be patterned electrode layers. 
     The spacers  14  may be ball spacers or photo spacers, which can be formed by a spraying or a photolithography process. The display medium layer  16  may include a plurality of microcapsules, having a display medium with a variable optical status in the microcapsule, and a plastic polymer material filling between the microcapsules. The plastic polymer material may be a curiable resin, which can be cured by a heat curing process or a UV light curing process. The display medium layer  16  may be an electro-phoretic display (EPD) medium layer, a cholesteric liquid crystal display (ChLCD) medium layer, an electrowetting display (EWD) medium layer or a quick-response liquid power display (QR-LPD) medium layer. 
     Driving methods for display pixels of the 3D curved display devices may comprise an electrical driving method, including a direct driving (or segmented driving) method, a passive matrix driving method and an active matrix driving method, or a photo driving method or a thermal driving method. In an embodiment, a thin film transistor (TFT) array (not shown) is further formed on the lower substrate  20 . The TFT array is electrically connected to the lower electrode layer  18  of the lower substrate  20  to form an active-matrix (AM) typed display. 
     Then, referring to  FIG. 1B , a pressure source is provided over the upper substrate  10 . In an embodiment, the pressure source can be provided from a mold  40  over the upper substrate  10 . Meanwhile, a mold  30  is provided under the lower substrate  20 . Through a molding process  50  to control a temperature, a tension and a pressure suitable for the plastic display panel  100 , the plastic display panel  100  is compressed onto the mold  30 , as shown in  FIG. 1C . After the molding process, the display medium layer  16  has a thickness H 2  substantially equal to the height D of the spacers  14 . Then, the display medium layer  16  is cured for shaping by a heat curing process or a UV light curing process. 
     In an embodiment, a sealant  22  may be dispersed between the upper substrate  10  and the lower substrate  20  to surround a peripheral area of the 3D curved display device, such that the display medium layer  16  is sealed by the sealant  22 . Then, as shown in  FIG. 1D , the molds  40  and  30  are removed to form the 3D curved display device  200 . The 3D curved display device  200  has a curved shape substantially the same as that with the surface stereo-shapes of the molds  40  and  30 . In addition, the surface stereo-shapes of the molds  40  and  30  and the curved shape of the 3D curved display device  200  can be a concave shape, a convex shape or a complex curved surface composed of concave and convex shapes. 
     Instead of the mold  40 , the pressure source over the upper substrate  10  can also be provided alternatively by applying air pressure onto the upper substrate  10 . The air pressure is about 0 to 10 atm. Moreover, a plurality of openings (not shown) passing through the mold  30  may be formed and then a vacuum-pumping process may be performed through the openings of the mold  30  to provide the pressure source. 
     In an embodiment, the plastic display panel  100  may further comprise a pair of alignment layers (not shown) individually disposed on an upper side and a lower side of the display medium layer  16  for sandwiching the display medium layer  16 . Further, in an embodiment, before performing the molding process  50 , a pair of polarizers (not shown) may be disposed on an upper side and a lower side of the plastic display panel  100  for sandwiching the plastic display panel  100 . In an embodiment, before performing the molding process  50 , a light reflective layer or a light absorbing layer (not shown) may be formed between the upper electrode layer  12  and the upper substrate  10  or between the lower electrode layer  18  and the lower substrate  20 , depending on the display types of the 3D curved display device. The material of the light reflective layer or the light absorbing layer may be aluminum, aluminum oxide, titania, carbon black or other color pigment. Moreover, in an embodiment, after forming the 3D curved display device  200 , a backlight (not shown) may be disposed on a side of the 3D curved display device  200 . 
     Referring to  FIGS. 2A-2E , cross sections of a method for fabricating a 3D curved display device according to another embodiment of the invention are shown. As shown in  FIG. 2A , first, a lower substrate  20  is provided and a lower electrode layer  18  is formed on the lower substrate  20 . The materials of the lower substrate  20  and the lower electrode layer  18  can be selected from the above mentioned plastic or elastic materials. 
     Then, referring to  FIG. 2B , a mold  70  and a mold  30  are provided and individually disposed over and under the lower substrate  20  for compressing the lower substrate  20  and the lower electrode layer  18  onto the mold  30  by a molding process. In an embodiment, the materials of the lower substrate  20  and the lower electrode layer  18  may be elastic materials. Moreover, during the molding process, a plurality of openings  32  of the mold  30  can be utilized to perform a vacuum-pumping process  60  or an adhesive may be used for fixing the lower substrate  20  and the lower electrode layer  18  onto the mold  30 . 
     Next, referring to  FIG. 2C , an upper substrate  10  is provided and an upper electrode layer  12  is formed on the upper substrate  10 . Then, a plurality of spacers  14  and a display medium layer  16  are formed on the upper electrode layer  12 . The display medium layer  16  has a thickness greater than a height of the spacers  14 . The thickness of the display medium layer  16  is about 1.3 to 1.5 times the height of the spacers  14 . In an embodiment, the materials of the upper substrate  10  and the upper electrode layer  12  can be selected from the above mentioned plastic or elastic materials. 
     A pressure source is provided over the upper substrate  10 . Through a molding process  50  to control a temperature, a tension and a pressure suitable for the plastic display panel  100 , the upper substrate  10 , upper electrode layer  12 , the spacers  14  and the display medium layer  16  are compressed with the lower electrode layer  18  on the mold  30  and the lower substrate  20  together. The pressure source can be provided from the mold  40  or from applying an air pressure over the upper substrate  10 . 
     Then, referring to  FIG. 2D , a 3D curved display device is formed between the mold  40  and the mold  30 . The display medium layer  16  has a thickness substantially equal to the height of the spacers  14 . After the molding process  50 , the display medium layer  16  is cured for shaping by a heat curing process or a UV light curing process. In an embodiment, a sealant  22  may be formed at a peripheral area of the 3D curved display device to seal the display medium layer  16 . Then, as shown in  FIG. 2E , the molds  40  and  30  are removed to form the 3D curved display device  200 . Moreover, the 3D curved display device  200  may further comprise a pair of alignment layers, a pair of polarizers, a light reflective layer or a light absorbing layer and/or a backlight disposed in the same way as the above mentioned embodiments. 
     Referring to  FIGS. 3A-3D , cross sections of a method for fabricating a 3D curved display device according to further another embodiment of the invention are shown. As shown in  FIG. 3A , a mold  30  is provided and then a lower electrode layer  18  is formed on the mold  30 . The lower electrode layer  18  may be a patterned electrode layer formed by a printing process or a laser patterning process. In an embodiment, the material of the lower electrode layer  18  can be selected from good conductive materials such as silver paste, aluminum, copper, indium tin oxide (ITO), poly(3,4-ethylene dioxythiophene) (PEDOT), polyaniline (PANI), polymers mixed with nano-carbon tubes (CNTs) or polymers mixed with metal fibers. 
     Next, referring to  FIG. 3B , an upper substrate  10  is provided and an upper electrode layer  12  is formed on the upper substrate  10 . Then, a plurality of spacers  14  and a display medium layer  16  are formed on the upper electrode layer  12 . The display medium layer  16  has a thickness greater than a height of the spacers  14 . The thickness of the display medium layer  16  is about 1.3 to 1.5 times the height of the spacers  14 . In an embodiment, the materials of the upper substrate  10  and the upper electrode layer  12  can be selected from the above mentioned plastic materials. 
     A pressure source is provided over the upper substrate  10 . Through a molding process  50  to control a temperature, a tension and a pressure suitable for the plastic display panel  100 , the upper substrate  10 , upper electrode layer  12 , the spacers  14  and the display medium layer  16  are compressed with the lower electrode layer  18  on the mold  30 . The pressure source can be provided from the mold  40  or applying an air pressure over the upper substrate  10 , or performing a vacuum-pumping process on the lower electrode layer  18  through a plurality of openings of the mold  30 . 
     Then, referring to  FIG. 3C , after the molding process  50 , a 3D curved display device is formed. The display medium layer  16  has a thickness substantially equal to the height of the spacers  14 . After the molding process  50 , the display medium layer  16  is cured for shaping by a heat curing process or a UV light curing process. In an embodiment, a sealant  22  may be formed at a peripheral area of the 3D curved display device to seal the display medium layer  16 . 
     Next, referring to  FIG. 3D , the mold  40  is removed to form a 3D curved display device  300 . In this embodiment, the mold  30  is a portion of the 3D curved display device  300 . Moreover, the 3D curved display device  300  may further comprise a pair of alignment layers, a pair of polarizers, a light reflective layer or a light absorbing layer and/or a backlight, wherein the upper polarizer is disposed over the upper substrate and the lower polarizer is disposed between the lower electrode layer  18  and the mold  30 . The other elements of the 3D curved display device  300  are disposed in the same way as the above mentioned embodiments. 
     Referring to  FIGS. 4A-4C , cross sections of a method for fabricating a 3D curved display device according to further another embodiment of the invention are shown. As shown in  FIG. 4A , first, a lower substrate  20  is provided and a lower electrode layer  18  is formed on the lower substrate  20 . Then, a plurality of spacers  14  and a display medium layer  16  are formed on the lower electrode layer  18 . An upper electrode layer  12  is then formed on the display medium layer  16 . In a preferred embodiment, a protective layer  24  is further formed on the upper electrode layer  12  to protect the upper electrode layer  12  and the display medium layer  16 . In this embodiment, the materials of the lower substrate  20 , the lower electrode layer  18  and the upper electrode layer  12  can be selected from the above mentioned plastic or elastic materials 
     Next, referring to  FIG. 4B , a pressure source and a mold  30  are provided to sandwich the upper electrode layer  12  and the lower substrate  20 . Through a molding process, the protective layer  24 , the upper electrode layer  12 , the spacers  14 , the display medium layer  16 , the lower electrode layer  18  and the lower substrate  20  are compressed together. The pressure source can be provided from a mold  40  or applying an air pressure over the upper electrode layer  12 , or performing a vacuum-pumping process on the lower substrate  20  through a plurality of openings of the mold  30 . Then, as shown in  FIG. 4C , the molds  40  and  30  are removed to form a 3D curved display device  400 . 
     In another embodiment, the lower substrate  20  as shown in  FIG. 4A  may face the mold  40  and the upper electrode layer  12  may face the mold  30  for performing the molding process to form a 3D curved display device. In this embodiment, no protective layer is required to form over the upper electrode layer  12 . The lower substrate  20  is used as a protective layer of the 3D curved display device. Moreover, the 3D curved display device  400  may further comprise a pair of alignment layers, a pair of polarizers, a light reflective layer or a light absorbing layer and/or a backlight disposed in the same way as the above mentioned embodiments. 
     In the above mentioned embodiments, the mold  30  may or may not be removed, depending on actual application conditions. In addition, in the above mentioned embodiments, the descriptions of the upper and lower locations of the upper and the lower substrates are used to simplify and clearly describe the embodiments of the invention. Thus, the locations of the upper and the lower electrode layers and the locations of the upper and the lower substrates are not limited. In other embodiments, the display medium layers with different colors can be stacked into a multi-layered display medium layer to achieve colorful displays, wherein the adjacent display medium layers can share the upper and the lower substrates or the upper and the lower electrode layers. In these embodiments, the relative locations of the substrates and the electrode layers can be interchanged. 
     According to the embodiments of the invention, 3D curved display devices and fabrication methods thereof are provided. Moreover, plastic display panels are also provided, which can be applied to molds with various shapes for forming 3D curved display devices with various shapes. 
     While the invention has been described by way of example and in terms of preferred 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 aims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.