Abstract:
A flexible LCD device is provided, including a flexible substrate having a first side and a second side, wherein the first side is perpendicular to the second side. A first electrode is disposed over the flexible substrate, extending along a first direction, wherein the first direction is not perpendicular to the first side and the second side of the flexible substrate. A first liquid crystal layer is disposed over the first electrode. A colored layer is disposed over the first liquid crystal layer. A second electrode is disposed over the colored layer, extending along a second direction, wherein the second direction is different from the first direction and is not perpendicular to the first side and the second side of the flexible substrate and the second direction is interlaced with the first direction.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This Application claims priority of Taiwan Patent Application No. 98115981, filed on May 14, 2009, the entirety of which is incorporated by reference herein. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to flexible display devices, and in particular, to flexible liquid crystal display (flexible LCD) devices. 
         [0004]    2. Description of the Related Art 
         [0005]    Cathode ray tube (CRT) devices have been largely replaced by liquid crystal display (LCD) devices for displaying systems. 
         [0006]    However, due to weight and thickness of LCD devices made with glass substrates, application thereof in portable electronic devices has been hindered. 
         [0007]    Therefore, flexible liquid crystal display (flexible LCD) devices have been developed for application in portable electronic devices. Flexible LCD devices made with flexible material such as plastic are lighter and thinner than those made with glass substrates. Some electronic devices using flexible LCD devices are electronic books (E-books), electronic papers (E-papers), and electronic billboards. 
         [0008]    In U.S. Pat. No. 6,639,637, Stephenson discloses a passive matrix type liquid crystal display (LCD) device utilizing a flexible plastic substrate. Perpendicular patterned conductive layers for driving liquid crystals are perpendicularly disposed on corresponding sides of the flexible plastic substrate. Nevertheless, display quality diminishes when there is insufficient driving voltage applied to the patterned conductive layer. Specifically, because the passive matrix type LCD device has a high aspect ration (e.g. an aspect ratio greater than 2:1), a length of the patterned conductive layer extending along the longer side of the passive matrix type LCD device maybe too long, thus a driving voltage applied thereto may be dropped and being inefficient with progress thereof along length of the patterned conductive layer extending along the longer side of the passive matrix type LCD device. In addition, since the patterned conductive layers are perpendicularly disposed on corresponding sides of the flexible plastic substrate, the patterned conductive layers may crack or break when bent if the passive matrix type LCD device is bent. 
         [0009]    Thus, an electrode structure for passive matrix type LCD devices which minimizes insufficient driving voltage and cracking or breaking of patterned conductive layers therein is desired. 
       BRIEF SUMMARY OF THE INVENTION 
       [0010]    Accordingly, flexible liquid crystal display (flexible LCD) devices with improved electrode structures are provided to overcome the above mentioned problems. 
         [0011]    An exemplary flexible LCD device comprises a flexible substrate having a first side and a second side, wherein the first side is perpendicular to the second side. A first electrode is disposed over the flexible substrate, extending along a first direction, wherein the first direction is not perpendicular to the first side and the second side of the flexible substrate. A first liquid crystal layer is disposed over the first electrode. A colored layer is disposed over the first liquid crystal layer. A second electrode is disposed over the colored layer, extending along a second direction, wherein the second direction is different from the first direction and is not perpendicular to the first side and the second side of the flexible substrate, and the second direction is interlaced with the first direction. 
         [0012]    Another exemplary flexible LCD device comprises a flexible substrate having a first side and a second side, wherein the first side is perpendicular to the second side. A first electrode is disposed over the flexible substrate, extending along a first direction, wherein the first direction is not perpendicular to the first side and the second side of the flexible substrate. A first liquid crystal layer is disposed over the first electrode and the flexible substrate. A second electrode is disposed over the first liquid crystal layer, extending along a second direction, wherein the second direction is different from the first direction and is not perpendicular to the first side and the second side of the flexible substrate, and the second direction is interlaced with the first direction. A first insulating layer is disposed over the second electrode, covering the first liquid crystal layer. A third electrode is disposed over the first insulating layer, extending along the first direction, wherein the third electrode substantially aligns with the first electrode. A second liquid crystal layer is disposed over the third electrode and the first insulating layer. A light absorbing layer is disposed over the second liquid crystal layer. A fourth electrode is disposed over the light absorbing layer, extending along the second direction, wherein the fourth electrode substantially aligns with the second electrode. 
         [0013]    Yet another exemplary flexible LCD device comprises a flexible substrate having a first side and a second side, where the first side is perpendicular the second side. A first electrode is disposed over the flexible substrate, extending along a first direction, wherein the first direction is not perpendicular to the first side and the second side of the flexible substrate. A first liquid crystal layer is disposed over the first electrode and the flexible substrate. A second electrode is disposed over the first liquid crystal layer, extending along a second direction, wherein the second direction is not perpendicular to the first side and the second side of the flexible substrate, and the second direction is interlaced with the first direction. A first insulating layer is disposed over the second electrode, covering the first liquid crystal layer. A third electrode is disposed over the first insulating layer, extending along the first direction, wherein the third electrode aligns with the first electrode. A second liquid crystal layer is disposed over the third electrode and the first insulating layer. A fourth electrode is disposed over the second liquid crystal layer, extending along the second direction, wherein the fourth electrode substantially aligns with the second electrode. A second insulating layer is disposed over the fourth electrode, covering the second liquid crystal layer. A fifth electrode is disposed over the second insulating layer, extending along the first direction, wherein the fifth electrode substantially aligns with the third electrode and the first electrode. A third liquid crystal layer is disposed over the fifth electrode and the second insulating layer. A light absorbing layer is disposed over the third liquid crystal layer. A sixth electrode is disposed over the light absorbing layer, extending along the second direction, wherein the sixth electrode substantially aligns with the fourth electrode and the second electrode. 
         [0014]    A detailed description is given in the following embodiments with reference to the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    The invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein: 
           [0016]      FIG. 1  is a plan view of a flexible liquid crystal display device according to an embodiment of the invention; 
           [0017]      FIG. 2  is a stereo diagram of the flexible liquid crystal display device taken along line A-A in  FIG. 1 ; 
           [0018]      FIG. 3  is a stereogram of a flexible liquid crystal display device according to another embodiment of the invention; and 
           [0019]      FIG. 4  is a stereogram of a flexible liquid crystal display device according to yet another embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0020]    The following description is of the best-contemplated 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 best determined by reference to the appended claims. 
         [0021]      FIGS. 1-4  are schematic diagrams showing various exemplary embodiments of flexible LCD devices. 
         [0022]    In  FIG. 1 , a plan view of an exemplary flexible LCD device  100  is illustrated. The flexible LCD device  100  is a passive matrix type LCD device and only a portion of a pixel region in the flexible LCD device  100  is illustrated, for simplicity. 
         [0023]    As shown in  FIG. 1 , the pixel region of the flexible LCD device is formed with a substantially rectangular configuration and has a long side  110  parallel to an x direction as shown in  FIG. 1  and a short side parallel to a y direction as shown in  FIG. 1 . The long side  110  and the short side  115  are formed with an aspect ratio greater than 2:1 therebetween, preferably greater than 10:1. Thus, application in electronic devices such as large-sized electronic billboards may be considered. In addition, the flexible LCD device  110  also includes a plurality of electrodes  120  and  130 . As shown in  FIG. 1 , the electrodes  120  and the electrodes  130  are formed and arranged in different layers. The electrodes  130  are disposed in an upper layer (not shown, illustrated in solid lines) and the electrodes  120  are disposed in a lower layer (not shown, illustrated in dotted lines). Herein, the electrodes  130  and the electrodes  120  are not perpendicular to the long side  110  and the short side  115  of the flexible LCD device  110  and may have an included angle θ therebetween. Herein, the included angle θ is an acute angle of about 10-80 degrees, preferably of about 45 degrees. If the included angle θ is at 45 degrees, the electrodes  130  and the electrodes  120  will be perpendicular to each other. As shown in  FIG. 1 , if the included angle θ is not at an acute angle of 45 degree, the electrodes  130  and the electrodes  120  will not be perpendicular to each other and the included angle will not be 90 degrees (not shown). 
         [0024]    In  FIG. 2 , a stereo diagram of the flexible liquid crystal display device taken along line A-A in  FIG. 1  is illustrated, partially illustrating a pixel region in the flexible LCD device  100 . 
         [0025]    As shown in  FIG. 2 , the flexible LCD device  100  includes a flexible substrate  150  and the electrodes  120  are disposed over the flexible substrate  150 . The electrodes  120  are not perpendicular to the short side  115  and the long side  110  of the flexible substrate  150 , and has an acute angle (i.e. the included angle θ in  FIG. 1 ) included therebetween. The flexible substrate  150  can be made of flexible materials such as polymer plastics and is formed with a thickness of about 50-300 μm. A liquid crystal layer  155  is disposed over the electrodes  120 , having a thickness of about 2-20 μm. The liquid crystal layer  155  is also disposed over the flexible substrate  150  between the electrodes  120 . The liquid crystal layer  155  may comprise materials such as twisted nematic liquid crystals, cholesteric liquid crystals, ferroelectric liquid crystals or mesoporous liquid crystals. A colored layer  160  with a thickness of about 0.1- 5 μm is disposed over the liquid crystal layer  155  and may comprise materials such as pigments or dyes of a predetermined color. A plurality of electrodes  130  is disposed over the colored layer  160 . 
         [0026]    In this embodiment, one of the electrodes  120  or the electrodes  130  are transparent electrodes which comprise transparent conductive materials such as tin oxide or indium tin oxide (ITO), and the other one of the electrodes  120  and the electrodes  130  are opaque electrodes which comprise metal materials such as Al, Sn, Ag, Pt or W. The electrodes  120  and  130  are formed with a thickness of about 1-30 μm. In the embodiment illustrated in  FIG. 2 , the flexible liquid crystal display device  100  is a monochrome liquid crystal display device which displays images of a predetermined color depending on the color of the colored layer  160   
         [0027]    Compared with the patterned conductive layers in prior art flexible LCD devices, the electrodes  120  and the electrodes  130  of the flexible liquid crystal display device  100  in this embodiment are formed with closer electrode lengths. Thus, pressure drop of a driving voltage applied to the electrodes may not be happened sufficient driving voltage can be provided thereto; even if the aspect ratio of the long side  110  and the short side  115  of the flexible liquid crystal display device  100  is greater than 10:1. Moreover, since the electrodes  120  and the electrodes  130  are not perpendicular to the long side  110  and short side  115  of the flexible liquid crystal display device  100 , the electrodes do not crack or break when the flexible liquid crystal display device  100  is bent. 
         [0028]    In addition to monochrome LCD device applications, the flexible LCD device  100  can also be applied to multi-colored LCD devices or full-colored LCD devices. 
         [0029]    As shown in  FIG. 3 , a stereo diagram showing another exemplary flexible liquid crystal display device  100  is illustrated, wherein a structure similar with that illustrated in  FIG. 1  is illustrated and the same titles represent the same components. The main differences between the flexible liquid crystal display devices  100  illustrated in  FIGS. 2 and 3  are as follows. 
         [0030]    As shown in  FIG. 3 , the electrodes  120  are disposed over an insulating layer  165  but not disposed over the flexible substrate  150  as shown in  FIG. 2 . A plurality of electrodes  170  and  175  are disposed between the flexible substrate  150  and the insulating layer  165 , wherein the electrodes  170  are disposed over the flexible substrate  150  and a liquid crystal layer  180  is formed over the electrodes  170 . The liquid crystal layer  180  also covers the flexible substrate  150  exposed by the electrodes  170 . In addition, the electrodes  175  are disposed over the liquid crystal layer  180 . In this embodiment, the electrodes  170  substantially align with the electrodes  120  and the electrodes  175  substantially align with the electrodes  130 . Therefore, electrodes  120  substantially cover electrodes  170  and the electrodes  130  substantially cover the electrodes  175 , thereby having a plan view substantially the same with that shown in  FIG. 1 . The insulating layer  165  covers the liquid crystal layer  180  under the electrodes  175  and has a thickness of about 1-20 μm. 
         [0031]    In this embodiment, similar with the electrodes  120  and the electrodes  130 , the long sides  110  and short sides  115  of the flexible LCD device  100  and the electrodes  170  and the electrodes  175  have an included angle of about 10-80 degrees. The liquid crystal layer  180  is the same as the liquid crystal layer  155  and may comprise materials such as twisted nematic liquid crystals, cholesteric liquid crystals, ferroelectric liquid crystals or mesoporous liquid crystals. The liquid crystal layer  155  and  180  can be formed with a different color such as red, blue, green, cyan, magenta, or yellow. In addition, a light absorbing layer  160 ′ rather than the colored layer  160  as shown in  FIG. 2  is provided between the electrodes  130  and the liquid crystal layer  155  to thereby filter incident light (not shown) of predetermined wavelength. 
         [0032]    As shown in  FIG. 3 , one of the electrodes  130  and the electrodes  170  is a transparent electrode and the other one is an opaque electrode. In addition, the electrodes  120  and the electrodes  175  are both transparent electrodes. Materials and thicknesses of the electrodes  170 ,  175 , and the liquid crystal  180  are the same with that described in the previous embodiment and are not discussed here again, for simplicity. 
         [0033]    In the embodiment shown in  FIG. 3 , the flexible LCD device  100  is a multi-color LCD device for displaying an multiple colored image rather than full color image and may have the same advantages over prior art as those described in the previous embodiment. 
         [0034]    As shown in  FIG. 4 , a stereo diagram showing yet another exemplary flexible liquid crystal display device  100  is illustrated, wherein a structure similar with that illustrated in  FIG. 3  is illustrated and the same titles represent the same components The main differences therebetween are discussed as follows . 
         [0035]    As shown in  FIG. 4 , the electrodes  170  are disposed over an insulating layer  185  but not the flexible substrate  150  as shown in  FIG. 3 . A plurality of electrodes  190  and  195  are disposed between the flexible substrate  150  and the insulating layer  185 , wherein the electrodes  190  are disposed over the flexible substrate  150  and a liquid crystal layer  200  is formed over the electrodes  170 . The liquid crystal layer  200  also covers the flexible substrate  150  exposed by the electrodes  190 . In addition, the electrodes  195  are disposed over the electrodes  100 . In this embodiment, the electrodes  190  substantially align with the electrodes  120  and the electrodes  195  substantially align with electrodes  130 . Therefore, electrodes  120  substantially cover electrodes  170  and the electrodes  130  substantially cover the electrodes  175 , thereby having a plan view substantially the same with that shown in  FIG. 1 . The insulating layer  185  covers the liquid crystal layer  195  under the electrodes  195  and has a thickness of about 1-20 μm. 
         [0036]    In this embodiment, similar with the electrodes  120 ,  130 ,  170 , and  175 , the long side  110  and short side  115  of the flexible LCD device  100  and the electrodes  190  and the electrodes  195  have an included angle of about 10-80 degrees. The liquid crystal layer  2000  is the same with the liquid crystal layer  155  and  180  and may comprise material such as twisted nematic liquid crystals, cholesteric liquid crystals, ferroelectric liquid crystals or mesoporous liquid crystals. The liquid crystal layer  155 ,  180 , and  200  can be formed with a different color such as red, blue, green, cyan, magenta, or yellow. In addition, a light absorbing layer  160 ′ is provided between the electrodes  130  and the liquid crystal layer  155  rather than the colored layer  160  illustrated in  FIG. 2  to thereby filter incident light (not shown) of predetermined wavelength. 
         [0037]    As shown in  FIG. 4 , one of the electrodes  130  and the electrodes  190  is a transparent electrode and the other one is an opaque electrode. In addition, the electrodes  120 ,  175 ,  170 , and  190  are all transparent electrodes. Materials and thicknesses of the electrodes  190 ,  195 , and the liquid crystal  200  are the same with that previous described and are not discussed here again, for simplicity. 
         [0038]    In the embodiment shown in  FIG. 4 , the flexible LCD device  100  is a full-color LCD device for displaying an image of full color and may have advantages which are the same as that described for the previous embodiments. 
         [0039]    While the invention has been described by way of example and in terms of the preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. 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.