Patent Publication Number: US-2012026586-A1

Title: Display device and phase retardation film

Description:
BACKGROUND 
     1. Technical Field 
     The disclosure generally relates to a display device and a phase retardation film, and more particularly, to a display device for displaying stereoscopic images and a phase retardation film. 
     2. Description of Related Art 
     Along with the development of technologies, besides having small sizes and light weights, display devices are desired to display stereoscopic images. Generally speaking, to display a stereoscopic image, two different images are respectively presented to the left and right eye of a viewer so that a stereoscopic image is constructed inside the viewer&#39;s brain. For example, the left-eye image is presented in a vertical linear polarization state, and the right-eye image is presented in a horizontal linear polarization state. The viewer can respectively receive the left-eye image and the right-eye image through his/her left and right eyes by wearing a polarized glass in the perpendicular direction and a polarized glass in the horizontal direction respectively on his/her left and right eyes, so that a stereoscopic image can be constructed within the viewer&#39;s brain. 
       FIG. 1  is a partial view of a typical stereoscopic display device. Referring to  FIG. 1 , the display device  100  has an array of sub-pixel regions  110 . There is a first phase retardation area  120  before a part of the sub-pixel regions  110  such that the left-eye image displayed by these sub-pixel regions  110  is presented in a first polarization state. There is a second phase retardation area  130  in front of the rest sub-pixel regions  110  such that the right-eye image displayed by these sub-pixel regions  110  is presented in a second polarization state. The left-eye glass worn by the viewer allows light in the first polarization state to pass through, and the right-eye glass worn by the viewer allows light in the second polarization state to pass through. Thus, the left-eye image and the right-eye image can successfully enter the viewer&#39;s left and right eyes and construct a stereoscopic image in the viewer&#39;s brain. 
     However, when the viewer looks at the display device  100  from a side viewing angle, the left-eye image displayed by the sub-pixel regions  110 A may pass through the second phase retardation area  130  and enter the viewer&#39;s right eye in the second polarization state, or the right-eye image displayed by the sub-pixel regions  110 B may pass through the first phase retardation area  120  and enter the viewer&#39;s left eye in the first polarization state. Namely, image distortion may be produced at the intersection C between the first phase retardation area  120  and the second phase retardation area  130 . Typically, a light shielding area is disposed between the first phase retardation area  120  and the second phase retardation area  130  in order to resolve the image distortion problem at side viewing angles. However, this may sacrifice the aperture ratio and accordingly cause the display brightness to be insufficient. 
     SUMMARY OF THE DISCLOSURE 
     According to an embodiment of the disclosure, a display device including a display module and a phase retardation layer is provided. The display module has a plurality of sub-pixel regions. The sub-pixel regions are arranged into an array along a first direction and a second direction, and the first direction is perpendicular to the second direction. The phase retardation layer is disposed at the display module. The phase retardation layer has a plurality of stripe-shaped first regions and a plurality of stripe-shaped second regions. The first regions and the second regions are parallel to each other and are alternatively arranged. A long axis of one of the first regions forms an acute angle with the first direction. The first regions and the second regions allow lights in different polarization states to pass through. 
     According to an embodiment of the disclosure, the phase retardation film presents a rectangular shape and has a plurality of stripe-shaped first regions and a plurality of stripe-shaped second regions. The first regions and the second regions are parallel to each other and are alternatively arranged. A long axis of one of the first regions forms an acute angle with one side of the rectangle. The first regions and the second regions allow lights in different polarization states to pass through. 
     These and other exemplary embodiments, features, aspects, and advantages of the disclosure will be described and become more apparent from the detailed description of exemplary embodiments when read in conjunction with accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings are included to provide a further understanding of the disclosure, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the disclosure and, together with the description, serve to explain the principles of the disclosure. 
         FIG. 1  is a partial view of a typical stereoscopic display device. 
         FIG. 2  is a partial view of a display device according to an embodiment of the disclosure. 
         FIG. 3  illustrates the relative position between the display device in  FIG. 2  and a user. 
         FIG. 4  is a partial view of an active device array substrate of the display device in  FIG. 2 . 
         FIG. 5  illustrates how the display device in  FIG. 2  displays a stereoscopic image. 
         FIGS. 6A-6C  are flowcharts illustrating the fabrication of a phase retardation film according to an embodiment of the disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to the present preferred embodiments of the disclosure, 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. 2  is a partial view of a display device according to an embodiment of the disclosure, and  FIG. 3  illustrates the relative position between the display device in  FIG. 2  and a user. Referring to  FIG. 2  and  FIG. 3 , the display device  1000  in the present embodiment includes a display module  1100  and a phase retardation layer  1200 . The display module  1100  has a plurality of sub-pixel regions  1110 . The sub-pixel regions  1110  are arranged into an array along a first direction D 10  and a second direction D 20 , and the first direction D 10  is perpendicular to the second direction D 20 . The phase retardation layer  1200  is disposed at the display module  1100 . To be specific, the phase retardation layer  1200  is located between the display module  1100  and a user  50  so that before an image displayed by the display module  1100  enters the eyes of the user  50 , the image is modulated by the phase retardation layer  1200  to correctly pass through a left-eye glass or a right-eye glass of a pair of glasses  60  worn by the user  50  and then enters the left eye or right eye of the user  50  to construct a stereoscopic image. 
     The phase retardation layer  1200  has a plurality of stripe-shaped first regions  1210  and a plurality of stripe-shaped second regions  1220 . The first regions  1210  and the second regions  1220  are parallel to each other and are alternatively arranged. Namely, two second regions  1220  are respectively located at two sides of a first region  1210 , and two first regions  1210  are respectively located at two sides of a second region  1220 . A long axis D 30  of one of the first regions  1210  forms an acute angle θ with the first direction D 10 , and the first regions  1210  and the second regions  1220  allow lights in different polarization states to pass through. 
     In the present embodiment, each sub-pixel region  1110  is assumed to be a square. However, each sub-pixel region  1110  may also present a rectangular shape or any other suitable shape. Additionally, in the present embodiment, four sub-pixel regions  1110  constitute a complete pixel region. The sub-pixel regions  1110  can be categorized into red sub-pixel regions  1110 R, green sub-pixel regions  1110 G, blue sub-pixel regions  1110 B, and white sub-pixel regions  1110 W. The display brightness of the display device  1000  can be improved by increasing the number of white sub-pixel regions  1110 W. As shown in  FIG. 2 , in the present embodiment, most of the first regions  1210  and the second regions  1220  of the phase retardation layer  1200  present a stripe shape, but the first regions  1210  or second regions  1220  located at the corners present a triangular shape. In addition, the acute angle θ formed by the long axis D 30  of a stripe-shaped first region  1210  and the first direction D 10  is between 10° and 45°. 
     The design in the present embodiment offers the largest aperture ratio when the acute angle θ is tan −1 (1/2). However, the disclosure is not limited thereto. In the present embodiment, the phase retardation difference between the first regions  1210  and the second regions  1220  is π/2. Namely, after lights in the same linear polarization state pass through the first regions  1210  and the second regions  1220 , the linear polarization directions thereof form an angle of π/2. In the present embodiment, it is assumed that the lights passing through the first regions  1210  and the second regions  1220  are in linear polarization states. However, in other embodiments, the lights passing through the first regions  1210  and the second regions  1220  may also be in circular polarization states. It is within the scope of the disclosure as long as the lights passing through the first regions  1210  and the second regions  1220  are in different polarization states therefore respectively pass through the left-eye glass and the right-eye glass of the glasses  60  worn by the user  50 . 
     In the present embodiment, no black matrix is disposed between the first regions  1210  and the second regions  1220  of the phase retardation layer  1200  so that the aperture ratio of the display device  1000  won&#39;t be affected. In addition, in the present embodiment, the phase retardation layer  1200  is an individual film attached to the surface of the display module  1100 . However, in other embodiments, the phase retardation layer  1200  may also be directly fabricated on the surface of or inside the display module  1100 . 
     In the present embodiment, each sub-pixel region  1110  has overlap regions with the first regions  1210  and the second regions  1220 , and a smaller one of the overlap regions between each sub-pixel region  1110  and the first regions  1210  and the second regions  1220  is a triangular region  1112 , and the triangular region  1112  is opaque. Referring to  FIG. 2 , with such a design, the green sub-pixel regions  1110 G and the white sub-pixel regions  1110 W of the first regions  1210  are all corresponding to the first regions  1210  in the horizontal direction. Thus, image distortion at side viewing angles is avoided. Referring to  FIG. 2 , the white sub-pixel regions  1110 W of the first regions  1210  and the green sub-pixel regions  1110 G of the second regions  1220  belong to different phase retardation areas. However, because the opaque triangular region  1112  is disposed at the overlapped areas between the white sub-pixel regions  1110 W and the second regions  1220 , the situation of sub-pixel regions of a same color crossing over two different phase retardation areas (i.e., the first regions  1210  and the second regions  1220 ), and accordingly image distortion at side viewing angles, is avoided. 
       FIG. 4  is a partial view of an active device array substrate of the display device in  FIG. 2 . Referring to  FIG. 3  and  FIG. 4 , in the present embodiment, the display module  1100  is a liquid crystal display (LCD) module. However, in other embodiments, the display module may also be an organic electro-luminescence device (OELD) panel, a plasma display panel, an electrophoresis display module, or any other display module as long as it has a plurality of sub-pixel regions arranged into an array. In the present embodiment, the display module  1100  has an active device array substrate  1130 . The active device array substrate  1130  has a plurality of active devices  1132 , a plurality of data lines  1134 , a plurality of scan lines  1136 , a plurality of pixel electrodes  1138 , and a plurality of common lines  1140 . Each active device  1132  is driven by a corresponding data line  1134  and a corresponding scan line  1136 , and each active device  1132  is electrically connected to a pixel electrode  1138 . Each common line  1140  has a triangular-shaped block  1142  at each triangular region  1112  in  FIG. 2 , and each block  1142  and the pixel electrode  1138  above the block  1142  constitute a pixel storage capacitor  1144 . In other words, a pixel storage capacitor  1144  as shown in  FIG. 4  can be disposed at each triangular region  1112  in  FIG. 2 . The pixel storage capacitors  1144  are essential devices to certain active device array substrate  1130 , and the blocks  1142  of the common lines  1140  constituting the pixel storage capacitors  1144  are made of an opaque metal material. Thus, in the present embodiment, besides resolving the problem of image distortion at side viewing angles in the display module  1100  by adopting the design of the triangular region  1112 , the maximum aperture ratio is also achieved, so as to improve the display brightness, by providing regions for disposing the pixel storage capacitors  1144 . 
     In the embodiment described above, the triangular region  1112  is made opaque by disposing the pixel storage capacitors  1144 . However, the triangular region  1112  may also be made opaque by covering a typical black matrix layer or through other techniques. 
       FIG. 5  illustrates how the display device in  FIG. 2  displays a stereoscopic image. Referring to  FIG. 5 , each sub-pixel region  1110  is marked with symbol R or L to indicate whether the sub-pixel region  1110  displays the right-eye image or the left-eye image. As shown in  FIG. 5 , the sub-pixel regions  1110  corresponding to the first regions  1210  of the phase retardation layer  1200  display the left-eye image, while the sub-pixel regions  1110  corresponding to the second regions  1220  display the right-eye image. Because the left-eye image displayed by the sub-pixel regions  1110  passes through the left-eye glass  62  of the glasses  60  worn by the user and the right-eye image displayed by the sub-pixel regions  1110  cannot pass through the left-eye glass  62  of the glasses  60  worn by the user, the user cannot see the bottom left image in  FIG. 5  through his left eye. Similarly, the user can see the bottom right image (which passes through the right-eye glass  64 ) in  FIG. 5  through his right eye. The images presented to both eyes of the user constitute a stereoscopic image in the user&#39;s brain. 
     Additionally, image signals provided by an image source (for example a computer) are usually transmitted in a format adapted to red, green, and blue colors. When the image signals are displayed as a stereoscopic image by the display device  1000 , the image signals are first converted into red, green, blue, and white signals through calculations, sorted according to whether they belong to the left-eye image or the right-eye image, and then sequentially sent to the sub-pixel regions  1110  to achieve the image distribution pattern as shown in  FIG. 5 , so as to display the stereoscopic image. When the display device  1000  displays a 2D image, the image signals transmitted in the format adapted to red, green, and blue colors are simply converted into red, green, blue, and white signals through calculations and sent to the corresponding sub-pixel regions  1110 , and the user can take off the glasses  60  and directly look at the display device  1000  to see the 2D image. 
     In the display device  1000  of the present embodiment, four sub-pixel regions  1110 R,  1110 G,  1110 B, and  1110 W which have a width of four sub-pixel regions  1110  in the horizontal direction and a width of three sub-pixel regions  1110  in the vertical direction constitute a complete pixel region. Thus, the display resolution won&#39;t be reduced too much when the display device  1000  displays stereoscopic images. Taking a 65″ display device having 1920×1080 pixel regions as an example, if the user is 4.12 meters away from the display device, the horizontal viewing angle width of a complete pixel region captured by the user is 0.01°, and the vertical viewing angle width thereof is 0.008°. Both the horizontal viewing angle width and the vertical viewing angle width are smaller than the minimum viewing angle width 0.016° between two objects recognizable to human eyes. Thereby, the design in the present embodiment can present stereoscopic images having optimal resolution to the user. 
       FIGS. 6A-6C  are flowcharts illustrating the fabrication of a phase retardation film according to an embodiment of the disclosure. Referring to  FIG. 6A , first, a plurality of stripe-shaped first regions  220  and a plurality of stripe-shaped second regions  230  are formed on a carrier substrate  210  by using a phase retardation material. The carrier substrate  210 , the first regions  220 , and the second regions  230  can be mass produced through batch manufacturing to reduce the fabrication cost. The first regions  220  and the second regions  230  are parallel to each other and are alternatively arranged. 
     Then, referring to  FIG. 6B , the carrier substrate  210  is cut along a frame F 10 . The frame F 10  presents a rectangular shape, and a long axis D 40  of one of the first regions  220  forms an acute angle with one side of the frame F 10 . Next, referring to  FIG. 6C , a phase retardation film  200  is completed. The phase retardation film  200  presents a rectangular shape and has a plurality of stripe-shaped first regions  220  and a plurality of stripe-shaped second regions  230 . The first regions  220  and the second regions  230  are parallel to each other and are alternatively arranged. A long axis D 40  of one of the first regions  220  forms an acute angle with the side E 10  of the rectangle. The first regions  220  and the second regions  230  of the phase retardation film  200  are similar to the first regions  220  and the second regions  230  in  FIG. 2 , and the acute angle formed by the long axis D 40  and the side E 10  of the rectangle is also similar to the acute angle θ in  FIG. 2  (for example, tan −1 (1/2)), therefore will not be described herein. 
     In summary, embodiments of the disclosure provide a display device and a phase retardation film, and the arrangement direction of sub-pixel regions and the long axis of a phase retardation area form an acute angle. Such a design resolves the problem of stereoscopic image distortion at side viewing angles and offers optimal stereoscopic image display brightness. In addition, light-shielding triangular pixel storage capacitors may be adopted to further increase the aperture ratio of the display device. 
     It is to be understood, however, that even though numerous characteristics and advantages of the present embodiments have been set out in the foregoing description, together with details of the structures and functions of the embodiments, the disclosure is illustrative only; and that changes may be made in detail, especially in matters of shape, size and arrangement of parts within the principles of the disclosure to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.