Patent Publication Number: US-2012038853-A1

Title: Display device, display apparatus for displaying 3d image and method for changing polarization direction of light emitted from liquid crystal display device

Description:
This application claims the benefit of Taiwan application Serial No. 099127000, filed Aug. 12, 2010, the subject matter of which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates in general to a display device and a method for changing the polarization direction of a light emitted from the display device, and more particularly to a display apparatus for displaying a 3D image and a method for changing the polarization direction of a light emitted from the display device. 
     2. Description of the Related Art 
     The three-dimensional (3D) display technology mainly projects the image lights of a left eye frame and a right eye frame for forming a 3D image onto the viewer&#39;s left eye and right eye respectively, so that a 3D image can be constructed in the viewer&#39;s brain. According to a commonly used method, the viewer wears a specific pair of glasses, such as color filter glasses, polarizing glasses, shutter glasses, which achieves the 3D image effect by making the viewer&#39;s left eye and right eye receive different image light respectively. 
       FIG. 1  shows a conventional display apparatus for displaying a 3D image.  FIG. 2  shows an explosion diagram of a conventional the liquid crystal display device shown in  FIG. 1 .  FIG. 3  shows an explosion diagram of a viewing window of conventional shutter glasses shown in  FIG. 1 . Referring to  FIG. 1  and  FIG. 2 , the display apparatus for displaying a 3D image comprises a liquid crystal display device  1  and a pair of shutter glasses  11 . The liquid crystal display device  1  comprises a display panel  2  and a light source  3 . The display panel  2  comprises a pair of separate substrates  4  and  5 , and a liquid crystal layer  6  including liquid crystal molecules interposed between the inner sides of the substrates  4  and  5 , wherein the titled direction of the liquid crystal molecules in the liquid crystal layer  6  can be changed via controlling the electrical field between the substrates  4  and  5 . Two polarizers  7  and  8  are respectively adhered onto the outer sides of the two substrates  4  and  5 , and the optical axes of the two polarizers  7  and  8  are vertically arranged. The optical axis of the polarizer  7  close to the light source  3  filters the light source according to the polarization of the incident light and generates a linear polarized light which enters the display panel  2  and then is changed the polarization along with the liquid crystal layer  6 . The transmissibility of the linear polarized light with respect to the polarizer  8  determines brightness level so as to achieve the display effect in the viewer&#39;s eyes. In other words, if the polarization direction of the incident light through the liquid crystal layer  6  is identical to the optical axis direction of the polarizer  8 , then the incident light will be almost 100% transmitted. If the polarization direction of the incident light through the liquid crystal layer  6  is perpendicular to the optical axis direction of the polarizer  8 , then the incident light will be 100% absorbed by the polarizer  8 . If the angle between the polarization direction of the incident light through the liquid crystal layer  6  and the optical axis direction of the polarizer  8  is between 0 degree and 90 degrees, then the incident light will be partly absorbed by the polarizer  8  and partly transmitted. The liquid crystal display device  1  has different types, such as twisted nematic (TN) type and vertical alignment (VA) type, according to the choice of the liquid crystal layer  6 . The two types, TN type and VA type, have different methods for driving the liquid crystal display device  1 , and the optical properties vary accordingly. To provide a broader range of view angle for the viewer, when the liquid crystal display device  1  is realized by a TN type liquid crystal display device, the optical axis direction of the polarizer  8  is mostly 45 degrees or 135 degrees, and when the liquid crystal display device  1  is realized by a VA type liquid crystal display device, the optical axis direction of the polarizer  8  is mostly 0 degree or 90 degrees. 
     Referring to  FIG. 1  and  FIG. 3 . For a viewer to feel a 3D image, the liquid crystal display device  1  will alternately display image light on the display panel  2  for the left eye and the right eye respectively. The pair of shutter glasses  11  comprises a left eye (L) viewing window  19  and a right eye (R) viewing window  19 , wherein each of the viewing windows  19  comprises a liquid crystal panel  12 , and each liquid crystal panel  12  also comprises a pair of separate substrates  14  and  15 , and a liquid crystal layer  16  whose titled direction can be changed via controlling the electrical field between the substrates  14  and  15 . Two polarizers  17  and  18  are respectively adhered onto the outer sides of the two substrates  14  and  15 . Moreover, the optical axes of the two polarizers  17  and  18  are vertically arranged. By changing the alignment of the liquid crystal layer  16  of the liquid crystal panel  12  to control the image light emitted from the liquid crystal display device  1  can transmit the polarizer  17 . The viewer will view a 3D image by way of the following arrangements. According to the state of the left eye image and the right eye image which displayed on the liquid crystal display device  1 , the left eye image can be passed through the left eye (L) viewing window  19  at one time with the right eye (R) viewing window  19  is opaque, so that the viewer&#39;s left eye can receive the left eye image only but not the right eye image. At the next time, the right eye image can be passed through the right eye (R) viewing window  19  at another time, and the left eye (L) viewing window  19  is opaque so that the viewer&#39;s right eye can receive the right eye image only but not the left eye image. 
     In the liquid crystal display device  1 , various liquid crystal types go with various optical axis directions of the polarizer  8 . The optical axis direction of the polarizer  18  of the shutter glasses  11  must be identical to that of the polarizer  8 , otherwise, brightness loss will be occurred. 
     For a viewer, it is inconvenient to prepare various shutter glasses to go with various types of liquid crystal display device. Furthermore, the shutter glasses are expensive and will discourage consumers&#39; willingness in purchase. 
     SUMMARY OF THE INVENTION 
     Embodiments of the present disclosure is directed to a display device, a display apparatus for displaying a 3D image and a method for changing the polarization direction of a light emitted from a liquid crystal display device for enabling the viewer to watch the display frame displayed on different types of liquid crystal display devices with one set of viewing device only and at the same time maintaining the same level of brightness. 
     According to a first aspect of the present invention, a display device is provided. The display device comprises a liquid crystal display device and an optical film. The liquid crystal display device comprises a display panel and a polarizer. The polarizer is disposed on the display panel. The optical film is disposed on the polarizer and for changing a polarization direction of a light emitted from the polarizer. 
     According to a second aspect of the present invention, a display apparatus for displaying a 3D image is provided. The display apparatus for displaying a 3D image comprises a liquid crystal display device, a half wave plate and a viewing device. The liquid crystal display device comprises a display panel and a first polarizer. The first polarizer is disposed on the display panel. The half wave plate is disposed on the first polarizer and for changing a polarization direction of a light emitted from the first polarizer. The viewing device comprises two viewing windows, and a surface of each of the viewing windows has a second polarizer. 
     According to a third aspect of the present invention, a method for changing a polarization direction of a light emitted from a liquid crystal display device is provided. The liquid crystal display device comprises a display panel and a polarizer. The polarizer is disposed on the display panel. The method comprises: disposing an optical film on the polarizer. The optical film is used for changing the polarization direction of a light emitted from the polarizer. 
     The above and other aspects of the invention will become better understood with regard to the following detailed description of the preferred but non-limiting embodiment(s). The following description is made with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a conventional display apparatus for displaying a 3D image; 
         FIG. 2  shows an explosion diagram of a conventional the liquid crystal display device; 
         FIG. 3  shows an explosion diagram of a viewing window of conventional shutter glasses; 
         FIG. 4  shows a display apparatus for displaying a 3D image according to an embodiment of the invention; 
         FIG. 5  shows display apparatus for displaying a 3D image of a first example; 
         FIG. 6  shows display apparatus for displaying a 3D image of a second example; 
         FIG. 7  shows display apparatus for displaying a 3D image of a third example; 
         FIG. 8  shows display apparatus for displaying a 3D image of a fourth example; 
         FIG. 9  shows display apparatus for displaying a 3D image of a fifth example; 
         FIG. 10  shows display apparatus for displaying a 3D image of a sixth example; 
         FIG. 11  shows display apparatus for displaying a 3D image of a seventh example; 
         FIG. 12  shows display apparatus for displaying a 3D image of a eighth example; and 
         FIG. 13  shows a cross-sectional view of a display device according to an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 4  shows a display apparatus for displaying a 3D image according to an embodiment of the invention. The display apparatus for displaying a 3D image comprises a display device  30  and a viewing device  41 . The display device  30  comprises a liquid crystal display device  31  and an optical film  50 . As similar disclosed in the prior art, the liquid crystal display device  31  may comprise, for example, a light source  33 , a display panel  32  and polarizers  37  and  38 . As similar disclosed in the prior art, left eye (L) and right eye (R) viewing windows  49  of the viewing device  41  may comprise, for example, a liquid crystal panel  42  and polarizers  47  and  48 . The optical axis direction (that is, the polarization direction that is light transmissible) of the polarizer  48  of the left eye (L) viewing window  49  is identical to that of the right eye (R) viewing window  49 . The viewing device  41  may comprise a pair of shutter glasses for example. 
     The optical film  50  is used for changing the linear polarization direction of the light emitted from the polarizer  38 . The optical film  50  may comprise a retardation film, such as a half wave plate. In a preferred embodiment, the optical film  50  is realized by a single-layered half wave plate such as polycarbonate (Manufacturer: Teijin Chemicals Ltd; Product Name: GR-270). The optical film  50  can also be realized by a multi-layered half wave plate. Since the light source  33  used in the liquid crystal display device  31  emits a visible light whose wave band ranges from 380 nm to 780 nm, the optical film  50  can be realized by a broadband half wave plate, such as cyclic olefin polymer (COP) (Manufacturer: Nitto Denko; Product Name: NZF-270). The optical film  50  can produce the same change in the polarization direction with respect to a wide range of wave band. Therefore, color offset occurring as the lights of some wave bands are changed to different polarization directions can be avoided. 
     In one embodiment, the optical film  50  is a half wave plate, which changes the linear polarization direction of the light penetrating the half wave plate to another linear polarization direction. Referring to  FIG. 4 , for changing the polarization direction of the light emitted from the polarizer  38  to an polarization direction corresponding to the optical axis of the polarizer  48  for avoiding the deterioration in the image brightness viewed by the viewer, the optical axis of the optical film  50  and the optical axis of the polarizer  38  are arranged to have an optical angle therebetween. The optical angle is preferably a half of an angle that the optical axis of the polarizer  38  and the optical axis of the polarizer  48  have therebetween. Thus, the angle that the optical axis of the optical film  50  and the optical axis of the polarizer  38  have therebetween is substantially identical to the angle that the optical axis of the optical film  50  and the optical axis of the polarizer  48  have therebetween. 
     Since the polarization direction of the light emitted from the polarizer  38  of the liquid crystal display device  31  can be changed to the optical axis corresponding to the optical axis of the polarizer  48  by the optical film  50 , a user does not need to use a predetermined combination of the liquid crystal display device  31  and the viewing device  41 . The optical film  50  adapted to the properties of the viewing device  41  owned by a user can be adhered onto the liquid crystal display device  31  to achieve excellent display effect. 
       FIGS. 5 to 12  respectively show a display apparatus for displaying a 3D image of other examples. In  FIGS. 5 to 12 , the polarizers  38 A,  38 B,  38 C,  38 D,  38 E,  38 F,  38 G, and  38 H are similar to the polarizer  38  shown in  FIG. 4 . The optical films  50 A,  50 B,  50 C,  50 D,  50 E,  50 F,  50 G, and  50 H are similar to the optical film  50  shown in  FIG. 4 . The polarizer  48 A,  48 B,  48 C,  48 D,  48 E,  48 F,  48 G, and  48 H are similar to the polarizer  48  shown in  FIG. 4 . For simplicity purpose, other elements are not illustrated in the diagrams. 
     Referring to  FIG. 5 , in the first example, the liquid crystal display device of the display apparatus for displaying a 3D image is realized by a TN type liquid crystal display device. The viewing device is realized by a pair of VA type shutter glasses for receiving the image light emitted from the VA type liquid crystal display device. The optical axis of the polarizer  38 A disposed on the display panel of the TN type liquid crystal display device is 45 degrees and the optical axis of the polarizer  48 A used in the VA type shutter glasses equals 0 degree which differs with the optical axis of the polarizer  38 A on the display panel of the TN type liquid crystal display device by 45 degrees, so in this case the applicable optical film  50 A is realized by a half wave plate whose optical axis is 22.5 degrees and forms a contained angle of 22.5 ((45−0)/2) degrees with the optical axis of the polarizer  38 A. Thus, after the light  61 A emitted from the polarizer  38 A at a polarization direction of 45 degrees passes through the optical film  50 A, the light  61 A is converted into a light  65 A having a polarization direction at 0 degree and corresponds to the optical axis of the polarizer  48 A. 
     Likewise, in the second example, referring to  FIG. 6 , the liquid crystal display device is realized by a TN type liquid crystal display device. The viewing device is realized by a pair of VA type shutter glasses for receiving the image light emitted from the VA type liquid crystal display device. The optical axis of the polarizer  38 B disposed on the display panel of the TN type liquid crystal display device is 45 degrees and the optical axis of the polarizer  48 B used in the VA type shutter glasses equals 90 degrees, so in this case the applicable optical film  50 B is realized by a half wave plate whose optical axis is 67.5 degrees and differs with the optical axis of the polarizer  38 B by 22.5 (67.5−45 or (90−45)/2) degrees. Thus, after the light  61 B emitted from the polarizer  38 B at a polarization direction of 45 degrees passes through the optical film  50 B, the light  61 B is converted into a light  65 B having a polarization direction at 90 degrees and corresponds to the optical axis of the polarizer  48 B. 
     In the third example, referring to  FIG. 7 , the liquid crystal display device is realized by a TN type liquid crystal display device. The viewing device is realized by a pair of VA type shutter glasses for receiving the image light emitted from the VA type liquid crystal display device. The optical axis of the polarizer  38 C disposed on the display panel of the TN type liquid crystal display device is 135 degrees, and the optical axis of the polarizer  48 C used in the VA type shutter glasses equals 0 degree, so in this case the applicable optical film  50 C is realized by a half wave plate whose optical axis is 67.5 degrees. Thus, after the light  61 C emitted from the polarizer  38 C at a polarization direction of 135 degrees passes through the optical film  50 C, the light  61 C is converted into a light  65 C having a polarization direction at 0 degree and corresponds to the optical axis of the polarizer  48 C. 
     In the fourth example, referring to  FIG. 8 , the liquid crystal display device is realized by a TN type liquid crystal display device. The viewing device is realized by a pair of VA type shutter glasses for receiving the image light emitted from the VA type liquid crystal display device. The optical axis of the polarizer  38 D disposed on the display panel of the TN type liquid crystal display device is 135 degrees, and the optical axis of the polarizer  48 D used in the VA type shutter glasses equals 90 degrees, so in this case the applicable optical film  50 D is realized by a half wave plate whose optical axis is 112.5 degrees. Thus, after the light  61 D emitted from the polarizer  38 D at a polarization direction of 135 degrees passes through the optical film  50 D, the light  61 D is converted into a light  65 D having a polarization direction at 90 degrees and corresponds to the optical axis of the polarizer  48 D. 
     In the fifth example, referring to  FIG. 9 , the liquid crystal display device is realized by a VA type liquid crystal display device. The viewing device is realized by a pair of TN type shutter glasses for receiving the image light emitted from the TN type liquid crystal display device. The optical axis of the polarizer  38 E disposed on the display panel of the VA type liquid crystal display device is 0 degree, and the optical axis of the polarizer  48 E used in the TN type shutter glasses equals 45 degrees, so in this case the applicable optical film  50 E is realized by a half wave plate whose optical axis is 22.5 degrees. Thus, after the light  61 E emitted from the polarizer  38 E at a polarization direction of 0 degree passes through the optical film  50 E, the light  61 E is converted into a light  65 E having a polarization direction at 45 degrees and corresponds to the optical axis of the polarizer  48 E. 
     In the sixth example, referring to  FIG. 10 , the liquid crystal display device is realized by a VA type liquid crystal display device. The viewing device is realized by a pair of TN type shutter glasses for receiving the image light emitted from the TN type liquid crystal display device. The optical axis of the polarizer  38 F disposed on the display panel of the VA type liquid crystal display device is 0 degree, and the optical axis of the polarizer  48 F used in the TN type shutter glasses equals 135 degrees, so in this case the currently applicable optical film  50 F is realized by a half wave plate whose optical axis is 67.5 degrees. Thus, after the light  61 F emitted from the polarizer  38 F at a polarization direction of 0 degree passes through the optical film  50 F, the light  61 F is converted into a light  65 F having a polarization direction at 135 degrees and correspond to the optical axis of the polarizer  48 F. 
     In the seventh example, referring to  FIG. 11 , the liquid crystal display device is realized by a VA type liquid crystal display device. The viewing device is realized by a pair of TN type shutter glasses for receiving the image light emitted from the TN type liquid crystal display device. The optical axis of the polarizer  38 G disposed on the display panel of the VA type liquid crystal display device is 90 degrees, and the optical axis of the polarizer  48 G used in the TN type shutter glasses equals 45 degrees, so in this case the applicable optical film  50 G is realized by a half wave plate whose optical axis is 67.5 degrees. Thus, after the light  61 G emitted from the polarizer  38 G at a polarization direction of 90 degrees passes through the optical film  50 G, the light  61 G is converted into a light  65 G having a polarization direction at 45 degrees and corresponding to the optical axis of the polarizer  48 G. 
     In the eighth example, referring to  FIG. 12 , the liquid crystal display device is realized by a VA type liquid crystal display device. The viewing device is realized by a pair of TN type shutter glasses for receiving the image light emitted from the TN type liquid crystal display device. The optical axis of the polarizer  38 H disposed on the display panel of the VA type liquid crystal display device is 90 degrees, and the optical axis of the polarizer  48 H used in the TN type shutter glasses equals 135 degrees, so in this case the applicable optical film  50 H is realized by a half wave plate whose optical axis is 112.5 degrees. Thus, after the light  61 H emitted from the polarizer  38 H at a polarization direction of 90 degrees passes through the optical film  50 H, the light  61 H is converted into a light  65 HG having a polarization direction at 135 degrees and corresponds to the optical axis of the polarizer  48 H. 
     Nonetheless, the invention is not limited to the disposition and method described in the above embodiments, and can be adjusted to fit actual needs for changing the polarization direction of a light emitted from a liquid crystal display device to the direction corresponding to the polarization direction transmissible to the light of the viewing window of the viewing device. 
       FIG. 13  shows a cross-sectional view of a display device according to an embodiment of the invention. Referring to  FIG. 13 , the optical film  73  can be adhered onto a liquid crystal display device  71  by an adhesive layer  72 . The adhesive layer  72  may comprise pressure sensitive adhesion (PSA). The optical film  73  may comprise a retardation film, such as a half wave plate. In a preferred embodiment, the optical film  73  is a single-layered half wave plate. The optical film  73  can also be realized by a multi-layered half wave plate or a broadband half wave plate. A base  74 , which can be disposed on the optical film  73 , may comprise triacetyl cellulose (TAC) which possesses great hardness for providing protection. The surface treatment layer  75 , which can be disposed on the base  74 , may comprise a foggy anti-glare (AG) film for reducing glare or a gloss (HC) film for enhancing contrast and making the frame more colorful. 
     According to the embodiments of the invention, the polarization direction of the image light is adjusted by the optical film disposed on the polarizer of the liquid crystal display device. Thus, the user can adjust the light properties emitted from the liquid crystal display device according to the owned viewing device, and does not need to prepare specific viewing devices for different types of liquid crystal display devices, hence saving extra costs. The optical film can be adhered onto the liquid crystal display device by the adhesive layer, and thus is easy for use. Compared with the conventional method of  FIG. 1 , the display apparatus for displaying a 3D image of the invention has the advantages of convenience and cost saving. 
     While the invention has been described by way of example and in terms of the preferred embodiment(s), it is to be understood that the invention is not limited thereto. On the contrary, it is intended to cover various modifications and similar arrangements and procedures, and the scope of the appended claims therefore should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements and procedures.