Patent Publication Number: US-2018039150-A1

Title: Electrophoretic display device

Description:
RELATED APPLICATIONS 
     This application claims priority to Chinese Application Serial Number 201610635713.4, Aug. 5, 2016, which is herein incorporated by reference. 
     BACKGROUND 
     Field of Invention 
     The present invention relates to an electrophoretic display device. 
     Description of Related Art 
     In a market with a wide variety of consumer electronic products, electrophoretic display devices have been extensively utilized as display screens in electronic products, such as an electronic book. The electrophoretic display device has a display medium layer that mainly consists of an electrophoresis buffer and white and black charged particles that are doped in the electrophoresis buffer. Under a voltage application to the display medium layer, the white and black charged particles are driven to move, so that each pixel of the display medium layer displays black, white or a gray level. The electrophoretic display device utilizes incident light (e.g., sunlight or indoor ambient light) that irradiates the display medium layer to realize displaying the pixels. Therefore, the electrophoretic display device needs no backlight, which reduces power consumption. 
     In general, a color electrophoretic display has a color filter layer therein. When incident light is reflected by the display medium layer, the reflected light may pass through the color filter to display a color image. However, if an electrophoretic display device having a large size is in an environment with a high temperature (e.g., 70° C.) and a low relative humidity (e.g., 23%), a protection sheet and optical clear adhesive (OCA) that adheres the protection sheet to the color filter layer would induce a tensile stress to cause warpage, and thus the color filter layer is bent by the tensile stress. As such, color resists at the edge of the color filter layer may be normally displaced 45 μm to 50 μm; users may therefore find a visible color shift at the edge of the color electrophoretic display device though naked eyes. 
     SUMMARY 
     An aspect of the present invention is to provide an electrophoretic display device. 
     According to an embodiment of the present invention, an electrophoretic display device includes an electrophoretic display module, a color filter layer, a first adhesive layer, a first protection layer, a second adhesive layer, and a second protection layer. The electrophoretic display module has a first surface and a second surface that is opposite to the first surface. The color filter layer is located on the first surface of the electrophoretic display module. The first adhesive layer is located on the color filter layer. The first adhesive layer is located between the first protection layer and the color filter layer. The second adhesive layer is located on the second surface of the electrophoretic display module. The second adhesive layer is located between the second protection layer and the electrophoretic display module. 
     In one embodiment of the present invention, the first and second protection layers are made of the same material, and the first and second adhesive layers are also made of the same material. 
     In one embodiment of the present invention, the electrophoretic display device further includes a first barrier layer. The first barrier layer is located between the first protection layer and the first adhesive layer. 
     In one embodiment of the present invention, the electrophoretic display device further includes a second barrier layer. The second barrier layer is located between the second protection layer and the second adhesive layer. 
     In one embodiment of the present invention, the first and second barrier layers are made of the same material. 
     In one embodiment of the present invention, the electrophoretic display device further includes a first ultraviolet (UV) cut layer. The first UV cut layer is located between the first protection layer and the first adhesive layer. 
     In one embodiment of the present invention, the electrophoretic display device further includes a second UV cut layer. The second UV cut layer is located between the second protection layer and the second adhesive layer. 
     In one embodiment of the present invention, the first and second UV cut layers made of the same material. 
     In one embodiment of the present invention, the electrophoretic display module includes a front substrate, an array substrate, and a display medium layer. The display medium layer is located between the array substrate and the front substrate. 
     In one embodiment of the present invention, the front substrate has the first surface that faces away from the display medium layer. 
     In one embodiment of the present invention, the color filter layer, the first adhesive layer, and the first protection layer are stacked on the first surface of the front substrate in sequence. 
     In one embodiment of the present invention, the array substrate has the second surface that faces away from the display medium layer. 
     In one embodiment of the present invention, the second adhesive layer and the second protection layer are stacked on the second surface of the array substrate in sequence. 
     In one embodiment of the present invention, the color filter layer comprises a red color resist, a green color resist, and a blue color resist. 
     In one embodiment of the present invention, the electrophoretic display device has a display area. The length of the diagonal line of the display area is in a range from 30 inches to 45 inches. 
     In the aforementioned embodiment of the present invention, since the electrophoretic display device has the first adhesive layer and the first protection layer that are located on the first surface of the electrophoretic display module, and further has the second adhesive layer and the second protection layer that are located on the second surface of the electrophoretic display module. As a result of such a design, when the electrophoretic display device is in an environment with a high temperature and a low relative humidity, although the first protection layer and the first adhesive layer may form a tensile stress, the second protection layer and the second adhesive layer may also form another tensile stress. The directions of the two tensile stresses are opposite, and the intensity of the two tensile stresses is the same. Hence, the two tensile stresses may cancel each other out to prevent the color filter layer from being bent. As a result, the displacement of color resists at the edge of the color filter layer is not prone to occur, thereby preventing users from finding a visible color shift at the edge of the electrophoretic display device though naked eyes. 
     It is to be understood that both the foregoing general description and the following detailed description are by examples, and are intended to provide further explanation of the invention as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention can be more fully understood by reading the following detailed description of the embodiments, with reference made to the accompanying drawings as follows: 
         FIG. 1  is a top view of an electrophoretic display device according to one embodiment of the present invention; 
         FIG. 2  is a cross-sectional view of the electrophoretic display device taken along line  2 - 2  shown in  FIG. 1 ; 
         FIG. 3  is a cross-sectional view of an electrophoretic display device according to one embodiment of the present invention; 
         FIG. 4  is a cross-sectional view of an electrophoretic display device according to one embodiment of the present invention; and 
         FIG. 5  is a cross-sectional view of an electrophoretic display device according to one embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to the present embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts. 
       FIG. 1  is a top view of an electrophoretic display device  100  according to one embodiment of the present invention.  FIG. 2  is a cross-sectional view of the electrophoretic display device  100  taken along line  2 - 2  shown in  FIG. 1 . As shown in  FIG. 1  and  FIG. 2 , the electrophoretic display device  100  is a color display device, and has a display area  102 . In this embodiment, the length L of the diagonal line of the display area  102  may be greater than 30 inches, such as in a range from 30 inches to 45 inches, but the present invention is not limited in this regard. The electrophoretic display device  100  includes an electrophoretic display module  110 , a color filter layer  120 , a first adhesive layer  130 , a first protection layer  140 , a second adhesive layer  150 , and a second protection layer  160 . 
     The electrophoretic display module  110  has a first surface  111  and a second surface  113  that is opposite to the first surface  111 . The color filter layer  120  is located on the first surface  111  of the electrophoretic display module  110 . The first adhesive layer  130  is located on the color filter layer  120 . The first protection layer  140  is located on the first adhesive layer  130 , such that the first adhesive layer  130  is located between the first protection layer  140  and the color filter layer  120 . The second adhesive layer  150  is located on the second surface  113  of the electrophoretic display module  110 . The second protection layer  160  is located on the second adhesive layer  150 , such that the second adhesive layer  150  is located between the second protection layer  160  and the electrophoretic display module  110 . As a result of such a design, the first and second protection layers  140 ,  160  are configured in a mirror arrangement relative to the electrophoretic display module  110 , and the first and second adhesive layers  130 ,  150  are also configured in a mirror arrangement relative to the electrophoretic display module  110 . In this description, “mirror arrangement” is referred to as “symmetrical arrangement”. 
     In other words, the electrophoretic display device  100  has the first adhesive layer  130  and the first protection layer  140  that are located on the first surface  111  of the electrophoretic display module  110 , and further has the second adhesive layer  150  and the second protection layer  160  that are located on the second surface  113  of the electrophoretic display module  110 . When the electrophoretic display device  100  is in an environment with a high temperature (e.g., 70° C.) and a low relative humidity (e.g., 23%), although the first protection layer  140  and the first adhesive layer  130  may form a tensile stress F 1 , the second protection layer  160  and the second adhesive layer  150  may also form another tensile stress F 2 . The directions of the two tensile stresses F 1 , F 2  are opposite, and the intensity of the tensile stress F 1  and the intensity of the tensile stress F 2  are the same. Hence, the two tensile stresses F 1 , F 2  may cancel each other out to prevent the color filter layer  120  from being bent. As a result, the displacement of color resists at the edge of the color filter layer  120  may be reduced to less than 20 μm, thereby preventing users from finding a visible color shift at the edge of the electrophoretic display device  100  though naked eyes. 
     In this embodiment, the first and second protection layers  140 ,  160  may be made of the same material, and the first and second adhesive layers  130 ,  150  may be also made of the same material. Therefore, in the same environment condition, the tensile stress F 1  formed by the stacked first adhesive layer  130  and first protection layer  140  may be canceled out by the tensile stress F 2  that is formed by the stacked second adhesive layer  150  and second protection layer  160 . The first and second protection layers  140 ,  160  may be made of polyethylene terephthalate (PET), and the first and second adhesive layers  130 ,  150  may be made of optical clear adhesive (OCA), but the present invention is not limited in this regard. 
     The electrophoretic display module  110  includes a front substrate  112 , an array substrate  114 , and a display medium layer  116 . The display medium layer  116  is located between the array substrate  114  and the front substrate  112 . The display medium layer  116  has microcapsules  117 , and each of the microcapsules  117  has black particles  118  and white particles  119  therein. The front substrate  112  has the first surface  111  that faces away from the display medium layer  116 . The color filter layer  120 , the first adhesive layer  130 , and the first protection layer  140  are stacked on the first surface  111  of the front substrate  112  in sequence. The array substrate  114  has the second surface  113  that faces away from the display medium layer  116 . The second adhesive layer  150  and the second protection layer  160  are stacked on the second surface  113  of the array substrate  114  in sequence. 
     The color filter layer  120  may include a red color resist  122 , a green color resist  124 , and a blue color resist  126 . However, in another embodiment, the color filter layer  120  may further include a yellow color resist. After incident light enters the electrophoretic display device  100  from the first protection layer  140 , the incident light may pass through the color resist of the color filter layer  120 , and then the incident light is reflected by the display medium layer  116  that has the microcapsules  117 . Thereafter, the light reflected by the medium layer  116  may pass through the color resist of the color filter layer  120  again to display a color image in the display area  102 . In this embodiment, the positions of the red color resist  122 , the green color resist  124 , and the blue color resist  126  may respectively correspond to the positions of the pixel regions  115  of the array substrate  114 . In other words, the red color resist  122 , the green color resist  124 , and the blue color resist  126  may be respectively aligned with the pixel regions  115  of the array substrate  114 . As a result of such a configuration, it is helpful for the electrophoretic display device  100  to control images. 
     It is to be noted that the connection relationships and materials of the aforementioned elements will not be repeated in the following description. In the following description, other types of electrophoretic display devices will be described. 
       FIG. 3  is a cross-sectional view of an electrophoretic display device  100   a  according to one embodiment of the present invention. The electrophoretic display device  100   a  includes the electrophoretic display module  110 , the color filter layer  120 , the first adhesive layer  130 , the first protection layer  140 , the second adhesive layer  150 , and the second protection layer  160 . The difference between this embodiment and the embodiment shown in  FIG. 2  is that the electrophoretic display device  100   a  further includes a first barrier layer  170   a  and a second barrier layer  170   b.  The first barrier layer  170   a  is located between the first protection layer  140  and the first adhesive layer  130 . The second barrier layer  170   b  is located between the second protection layer  160  and the second adhesive layer  150 , such that the first and second barrier layers  170   a,    170   b  are configured in a mirror arrangement relative to the electrophoretic display module  110 . 
     The first barrier layer  170   a  may prevent moisture from entering the color filter layer  120  and the electrophoretic display module  110 , thereby extending the lifespan of the electrophoretic display device  100   a.  In addition, when the electrophoretic display device  100   a  is in an environment with a high temperature (e.g., 70° C.) and a low relative humidity (e.g., 23%), although the first protection layer  140 , the first barrier layer  170   a,  and the first adhesive layer  130  may form a tensile stress F 1 , the second protection layer  160 , the second barrier layer  170   b,  and the second adhesive layer  150  may also form another tensile stress F 2 . The directions of the two tensile stresses F 1 , F 2  are opposite, and the intensity of the tensile stress F 1  and the intensity of the tensile stress F 2  are the same. Hence, the two tensile stresses F 1 , F 2  may cancel each other out to prevent the color filter layer  120  from being bent. 
     In this embodiment, the first and second barrier layers  170   a,    170   b  may be made of the same material, such that the tensile stress of the first barrier layer  170   a  may be canceled out by the tensile stress of the second barrier layer  170   b.    
       FIG. 4  is a cross-sectional view of an electrophoretic display device  100   b  according to one embodiment of the present invention. The electrophoretic display device  100   b  includes the electrophoretic display module  110 , the color filter layer  120 , the first adhesive layer  130 , the first protection layer  140 , the second adhesive layer  150 , and the second protection layer  160 . The difference between this embodiment and the embodiment shown in  FIG. 2  is that the electrophoretic display device  100   b  further includes a first ultraviolet (UV) cut layer  180   a  and a second UV cut layer  180   b.  The first UV cut layer  180   a  is located between the first protection layer  140  and the first adhesive layer  130 . The second UV cut layer  180   b  is located between the second protection layer  160  and the second adhesive layer  150 , such that the first and second UV cut layers  180   a,    180   b  are configured in a mirror arrangement relative to the electrophoretic display module  110 . 
     The first UV cut layer  180   a  may prevent UV light from entering the color filter layer  120  and the electrophoretic display module  110 , thereby extending the lifespan of the electrophoretic display device  100   b.  In addition, when the electrophoretic display device  100   b  is in an environment with a high temperature (e.g., 70° C.) and a low relative humidity (e.g., 23%), although the first protection layer  140 , the first UV cut layer  180   a,  and the first adhesive layer  130  may form a tensile stress F 1 , the second protection layer  160 , the second UV cut layer  180   b,  and the second adhesive layer  150  may also form another tensile stress F 2 . The directions of the two tensile stresses F 1 , F 2  are opposite, and the intensity of the tensile stress F 1  and the intensity of the tensile stress F 2  are the same. Hence, the two tensile stresses F 1 , F 2  may cancel each other out to prevent the color filter layer  120  from being bent. 
     In this embodiment, the first and second UV cut layers  180   a,    180   b  may be made of the same material, such that the tensile stress of the first UV cut layer  180   a  may be canceled out by the tensile stress of the second UV cut layer  180   b.    
       FIG. 5  is a cross-sectional view of an electrophoretic display device  100   c  according to one embodiment of the present invention. The electrophoretic display device  100   c  includes the electrophoretic display module  110 , the color filter layer  120 , the first adhesive layer  130 , the first protection layer  140 , the second adhesive layer  150 , the second protection layer  160 , the first barrier layer  170   a,  and second barrier layer  170   b.  The difference between this embodiment and the embodiment shown in  FIG. 3  is that the electrophoretic display device  100   c  further includes the first UV cut layer  180   a  and the second UV cut layer  180   b.  The first UV cut layer  180   a  is located between the first barrier layer  170   a  and the first adhesive layer  130 . The second UV cut layer  180   b  is located between the second barrier layer  170   b  and the second adhesive layer  150 , such that the first and second barrier layers  170   a,    170   b  are configured in a mirror arrangement relative to the electrophoretic display module  110 , and the first and second UV cut layer  180   a,    180   b  are also configured in a mirror arrangement relative to the electrophoretic display module  110 . 
     When the electrophoretic display device  100   c  is in an environment with a high temperature (e.g., 70° C.) and a low relative humidity (e.g., 23%), although the first protection layer  140 , the first barrier layer  170   a,  the first UV cut layer  180   a,  and the first adhesive layer  130  may form a tensile stress F 1 , the second protection layer  160 , the second barrier layer  170   b,  the second UV cut layer  180   b,  and the second adhesive layer  150  may also form another tensile stress F 2 . The directions of the two tensile stresses F 1 , F 2  are opposite, and the intensity of the tensile stress F 1  and the intensity of the tensile stress F 2  are the same. Hence, the two tensile stresses F 1 , F 2  may cancel each other out to prevent the color filter layer  120  from being bent. 
     Although the present invention has been described in considerable detail with reference to certain embodiments thereof, other embodiments are possible. Therefore, the spirit and scope of the appended claims should not be limited to the description of the embodiments contained herein. 
     It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention covers modifications and variations of this invention provided they fall within the scope of the following claims.