Abstract:
A flat panel display with high brightness. The flat panel display comprises a panel and a light module. The panel has a plurality of pixels. The transmittivity of each pixel or the ratio of the transmissive area of each pixel to the area of the pixel exhibits a first distribution function. The light module supplies light to illuminate the panel. The intensity of the light exhibits a second distribution function. In the flat panel display, the distribution of the brightness of the panel is improved by controlling of the transmittivity of each pixel or the area ratio of the transmissive area, to attain a better visual quality.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a flat panel display, and in particular to a flat panel display with high brightness.  
         [0003]     2. Description of the Related Art  
         [0004]     As shown in  FIG. 1 , a conventional transflective flat panel display  100  comprises a panel  102  and a light module  104 .  106  and  108  represent top views of the pixels located in the central region  114  and the peripheral region  116  of the panel  102 , respectively.  FIG. 2  shows magnified view of the pixels  106  and  108  in  FIG. 1 . The interlaced-line area  110  is a reflective area, and the blank area  112  is a transmissive area. The reflective area  110  occupies about 30% of the entire pixel area, the transmissive area about 60%, and the remaining area (which may be shielded and not shown in the drawings), about 10%. In the display  100 , all the pixels  106  and  108  on the panel  102  have the same structure, that is, every reflective area  110  occupies the same amount of area, and every transmissive area  112  occupies the same amount of area. Therefore, the brightness of the reflected light at every position on the display  100  is identical, as shown by the curve  118  in  FIG. 4 .  
         [0005]      FIG. 3  shows the brightness supplied by the light module  104  to the panel  102 . The brightness supplied to the central region  114  is assumed 100%. The brightness supplied to the peripheral region  116  is assumed 80%. Since the brightness supplied by the light module  104  decreases from the central region to the peripheral region, the brightness of the transmitted light on the display  100  also decreases from the central region to the peripheral region, as shown by the curve  120  in  FIG. 4 . The brightness of the transmitted light in the central region  114  is about 60%. The brightness of the transmitted light in the peripheral region  116  is about 48%. Generally, the human eye cannot perceive any difference between the highest and lowest brightness on the display when the ratio of the difference to the highest brightness is less than 20%. Thus, a user will not perceive the brightness difference between the central region  114  and the peripheral region  116  when viewing the display. Additionally, the display quality is better when the brightness of the central region is higher than that of the peripheral region.  
         [0006]     However, the reflective area of each pixel on a conventional flat panel display  100  is identical, thus the brightness of reflected light is identical. If the brightness of the central region of a display can be enhanced to exceed that of the peripheral region, the viewers will be able to perceive a greatly enhanced brightness on the display, therefore, the display quality will be improved. Hence, a flat panel display with the described characteristics is called for.  
       SUMMARY OF THE INVENTION  
       [0007]     Accordingly, an object of the invention is to provide a flat panel display.  
         [0008]     According to one embodiment of the present invention, the flat panel display with high brightness comprises a panel having a plurality of pixels and a light module supplying light to illuminate the panel. Each of the pixels comprises at least one reflective area and at least one transmissive area. The ratio of the transmissive area of each pixel on the panel to the area of the pixel varies according to the distance from the pixel to the central position of the panel and exhibits a first distribution function. The intensity of light exhibits a second distribution function. The light module further comprises a light source for supplying light and a light guide plate for guiding the light to the panel.  
         [0009]     According to another embodiment of the present invention, the flat panel display with high brightness comprises a panel having a plurality of pixels and a light module supplying a light to illuminate the panel. Each of the pixels has indices reflectivity and transmittivity. The transmittivity of each pixel on the panel varies according to the distance from the pixel to the central position of the panel and exhibits a first distribution function. The intensity of light shows a second distribution function. Furthermore, the light module comprises a light source for supplying light and a light guide plate for guiding the light to the panel.  
         [0010]     In the present invention, the reflected light brightness of the panel is improved by altering the area ratio or transmittivity of the transmissive areas of the plurality of pixels on the panel to exhibit a first distribution function, preferably a function complementary to a Gaussian function. The transmitted light brightness, however, decreases when the reflected light increases. Therefore, the light supplied by the light module is adjusted to avoid the reduction of the transmitted brightness of the panel, without increasing the power of the light module. The intensity of the light supplied is adjusted to exhibit a second distribution function to illuminate on the panel in accordance with the distribution of the transmittivity on the panel. Preferably, the second distribution function is a Gaussian function.  
         [0011]     A detailed description is given in the following embodiments with reference to the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]     The present invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein:  
         [0013]      FIG. 1  is a schematic view showing a conventional transflective liquid crystal display;  
         [0014]      FIG. 2  is a magnified view of the pixel shown in  FIG. 1 ;  
         [0015]      FIG. 3  is a graph showing brightness levels provided by the light module shown in  FIG. 1  corresponding to different positions thereof;  
         [0016]      FIG. 4  is a graph showing reflected and transmitted light brightness of the display shown in  FIG. 1  corresponding to different positions thereof;  
         [0017]      FIG. 5  is a schematic view showing a flat panel display of an embodiment according to the present invention;  
         [0018]      FIG. 6  shows a curve obtained by plotting the area ratio of the transmissive area or the transmittivity versus the position of the panel according to the present invention;  
         [0019]      FIG. 7  is a schematic view of the reflected light brightness resulting from reflection of external light in an embodiment of the present invention;  
         [0020]      FIG. 8  is a graph showing light intensity supplied by the light module corresponding to different positions thereof;  
         [0021]      FIG. 9  is a graph showing the reflected and transmitted light brightness corresponding to different positions thereof in an embodiment according to the present invention;  
         [0022]      FIGS. 10A  to  10 D show the illustrative variations of the transmissive areas of pixels;  
         [0023]      FIG. 11  is a schematic view of the semi-transmissive metal layer;  
         [0024]      FIG. 12A  shows an illustrative example of light module  206 ;  
         [0025]      FIG. 12B  shows another illustrative example of light module  206 ;  
         [0026]      FIG. 13A  is a schematic view of a display using a backlight plate;  
         [0027]      FIG. 13B  is a schematic view of a display using a frontlight plate;  
         [0028]      FIG. 14  is a 3-dimensional schematic view of the curve shown in  FIG. 6 ;  
         [0029]      FIG. 15  is a 3-dimensional schematic view of the curve  222  shown in  FIG. 8 . 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0030]      FIG. 5  shows a flat panel display  200  of an embodiment according to the present invention, which comprises a panel  202  and a light module  206 . There are a number of pixels  208  and  210  on the panel  202 . The light module  206  supplies light to the panel  202 . Pixels  208  and  210  are in the central region  216  and the peripheral region  218  of the panel  202 , respectively, as shown in a top view in  FIG. 1 . Areas  212  and  214  with interlaced lines in the pixels  208  and  210  represent reflective areas, and areas  213  and  215  represent transmissive areas. In this embodiment, as shown in  FIG. 5 , the reflective area  212  of the pixel  208  in the central region  216  is larger than the reflective area  214  in the peripheral region  218 . In view of integration, the area ratio of the transmissive areas of the plurality of pixels on the panel  202  has a distribution function. In this embodiment, the distribution function is a continuous function complementary to a Gaussian function, as shown in  FIG. 6 . The function is A−exp[−α(x 2 +y 2 )], wherein parameter A is equal to or greater than 0.3 and equal to or less than 5, parameter α is equal to or greater than 10 −8  and equal to or less than 10 −4 , and x and y represent the pixel position of panel, respectively.  FIG. 14  is a 3-dimensional schematic view for the curve shown in  FIG. 6 .  
         [0031]     Please refer to  FIGS. 5 and 6 . For the flat panel display  200  of the embodiment, the area ratio of the transmissive areas of all pixels on the panel  202  has a continuous distribution function complementary to a Gaussian function, as shown in  FIG. 6 . The transmissive area closer to the central region of the pixel  216  has small area. The reflective area  212  of the pixel  208  in the central region  216  occupies 35% of the total area of the entire pixel, and the transmissive area  213  occupies. 55%; while the reflective area  214  of the pixel  210  in the peripheral region  218  occupies 29.8% of the total area of the entire pixel, and the transmissive area  215  occupies 60.3%. In this embodiment, the area of the reflective area  212  in the display  200  gradually decreases from the periphery to the center, thus the reflected light brightness resulting from reflection of the external light  234  is also higher in the center than in the periphery, as shown in  FIG. 7 .  
         [0032]     The area occupied by the transmissive area  213  of the pixel  208  in the central region  216  of the panel  202  is less than that of the transmissive area  215  of the pixel  210  in the peripheral region  218 , as shown in  FIG. 5 . Therefore, to prevent the brightness of the central region  216  of the display  200  from being lower than the brightness of the peripheral region  218 , the intensity of the light supplied to the panel  202  by the light module is adjusted to form a distribution function according to various pixel positions. The distribution is, for example, a Gaussian function, as shown by the curve  222  in  FIG. 8 , corresponding to the change of the ratio of the transmissive areas of the pixels. The function for the curve  222  is Bexp[β(x 2 +y 2 )], wherein parameter B is backlight intensity, parameter β is equal to or greater than 10 −7  and equal to or less than 10 −3 , and x and y represent the position of pixel, respectively.  FIG. 15  is a 3-dimensional schematic view for the curve  222 . In this embodiment, the light supplied by the light module  206  is gathered to the center of the panel  202 , such that the brightness of the central region  216  of the display  200  is not lower than that in the peripheral region  218 , as shown by the curve  232  in  FIG. 9 .  
         [0033]      FIG. 8  is a graph showing the relation between the light intensity supplied by the light module  206  in the display  200  according to the present invention and the panel position. The curve  220  represents the light intensity supplied by the light module of a conventional display at various positions, and the curve  222  represents the light intensity supplied by the light module  206  used in the present invention, in which the curve  222  is a Gaussian curve. The ratio of the difference, U, between the highest and the lowest brightness of the light module according to the present invention to the highest brightness is within the range of 30% to 70%. In  FIG. 8 , three areas  224 ,  226 , and  228  are positioned between the curves  220  and  222 . The area  224  must be equal to the sum of the areas  226  and  228 , so that the power consumed by the light module  206  does not exceed that of a conventional light module.  
         [0034]     According to the above description, the relationship of the intensity of the reflected and transmitted light of the flat panel display  200  according to the present invention and the position thereof can be obtained, as shown in  FIG. 9 . The curve  230  represents the brightness of the reflected light at various positions and the curve  232  represents the brightness of the transmitted light at various positions. The curve  230  can be obtained by multiplying the display  200  illuminated by external light by the area ratio of the reflective area of each position on the display  200 . The curve  232  can be obtained by multiplying the display  200  illuminated by the light module by the area ratio of the transmissive area of each position on the display  200 .  
         [0035]     In the present invention, the transmissive area of the pixel on the panel  200  may have various shapes. Four illustrative examples are shown in  FIGS. 10A  to  10 D, wherein areas  2362 ,  2382 ,  2402 , and  2422  with interlaced lines of pixels  236 ,  238 ,  240 , and  242  are reflective areas. The transmissive area  2364  of the pixel  236  is circular. The transmissive area  2384  of the pixel  238  is elliptical. The transmissive area  2404  of the pixel  240  comprises two rectangles. The transmissive area  2424  of the pixel  242  comprises a number of small circles.  
         [0036]     Furthermore, the pixels on the panel  202  may be a semi-transmissive metal layer  244 , as shown in  FIG. 11 , which has indices of transmittivity and reflectivity. When a light  245  is incident on the semi-transmissive metal layer  244 , part of the light  245  is transmitted through the semi-transmissive metal layer  244 , and the remainder of the light  245  is reflected by the semi-transmissive metal layer  244 . Likewise, by controlling the reflectivity or transmittivity of every semi-transmissive metal layer  244  on the panel  202  and allowing it to exhibit a distribution function, for example, a Gaussian function, improved brightness is achieved. In other embodiments, a multilayered film having indices transmittivity and reflectivity may be used to replace the semi-transmissive metal layer  244 .  
         [0037]     The structure of light module  206  may vary.  FIG. 12A  shows an exemplary light module, which comprises a light guide plate  246  with an inclined plane structure, a prism  248 , and a light source  250 . The light guide plate  246  and the light source  250  are separated. The prism  248  gathers and directs the light supplied by the source  250  to the light guide plate  246 . The light guide plate  246 , then, guides the light to the display.  FIG. 12B  shows another exemplary light module, which comprises a light guide plate  252  with a plane structure and a light source  250 . The light guide plate  252  and the light source  250  are combined. Similarly, the light guide plate  252  guides the light supplied by the light source  250  to the display.  FIGS. 13A and 13B  show the positional relationship of the light guide plate and the panel. In  FIG. 13A , the light guide plate  254  functions as a light module and is disposed behind the panel  256 . In  FIG. 13B , the light guide plate  254  functions as a frontlight plate and is disposed in front of the panel  256 .  
         [0038]     The liquid crystal injected into the display according to the present invention may be twisted nematic, super twisted nematic, vertical aligned, or mixed-mode twisted nematic and the display may be TFT-LCD, TFD-LCD, LTPS-LCD, electrophoresis display, or other flat panel display.  
         [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.