Patent Publication Number: US-2004046730-A1

Title: LCD (liquid crystal display) with a back light source characterized by light source local penetration

Description:
BACKGROUND OF THE INVENTION  
       [0001] The advent of the information era sees a ceaseless surge of human beings&#39; demand for the latest information. In the near future, human beings will enjoy acquiring, or even compete for, the information that is accessible to them in a speedy, voluminous manner. With plenty of advanced equipment, a great amount of information is efficiently transferred among the people anytime. An LCD is indispensable to information transmission nowadays.  
       [0002] Every notebook computer or cellular phone is equipped with a LCD for displaying the information sent or received. Frequently, LCDs may be used outdoors but be blamed for their poor performance. This does not occur without any reason. In general, the light source available to a LCD is the back light panel module on the bottom of the LCD. However, the brilliance of the light sent out by the back light panel module is much lower than that of daylight. As a result, whenever a LCD is used outdoors in the daytime, the screen display has worse contrast and thus it is not shown clearly. Increasing the illumination of the back light panel module invariably, will not only waste electricity and shorten the life of the other working components, but also make little improvement in the brilliance.  
       [0003] To solve the problem, manufacturers nowadays resort to two known methods. Firstly, the back light panel module of a LCD is replaced by a front light source found in the anterior part of the LCD. As shown in FIG. 1, the remedial structure is composed of a reflection-style LCD  1  and its front light source  2 . The front light source  2  has a light-guide plate  21 . It also has a cooled-cathode fluorescent tube  22  beside the light-guide plate  21 . The illumination surface of the light-guide plate  21  is designed in such a way that it has a continuous reflective oblique surface A-B. To reduce irregular reflection and diffused reflection, the side of the light-guide plate  21  opposite the LCD  1  is plated, or covered, with an AR-coating  23 . While a small part of the rays of light emitted by the cooled-cathode fluorescent tube  22  enter the LCD  1  directly and then reflect off the LCD  1 , most of them reflect off the reflective oblique surface A-B, enter the LCD  1 , and then reflect off the LCD  
       [0004] 1. Nevertheless, the remedial structure has not yet undergone mass production, because of the following shortcomings.  
       [0005] 1. The light-guide plate  21  of the front light source  2  is positioned above the LCD  1 . The manufacturing process has to be highly sophisticated, so that users are unable to see the rough surface of the light-guide plate  21  with the naked eye and the images displayed on the screens are of high quality. However, such a manufacturing process is rather expensive and difficult.  
       [0006] 2. The reflective oblique surface A-B found on the light-guide plate  21  of the front light source  2  reflects light in a general way. Much of the light is refracted when it passes through the reflective oblique surface A-B. Hence, the refracted light  1  is useless and overwhelming, whereas the amount of the useful light  11  available to the LCD  1  is limited.  
       [0007] 3. The light-guide plate  21  is plated, or covered, with an AR-coating  23  so as to reduce irregular reflection and diff-used reflection. For this reason, the manufacturing process is rather expensive and difficult.  
       [0008]FIG. 2 depicts another known method. Aback light source  4  is installed behind a LCD  3 . The bottom of the LCD is covered with a lens-film  31  characterized by part reflection and part transmission. The back light source  4  has a light-guide plate  41 . It also has a cooled-cathode fluorescent tube  42  beside the light-guide plate  41 . Manufacturers adopt a kind of semi-reflective, semi-transmissive lens-film  31  which reflects 80% of incident daylight and allows 20% of the remainder to pass through it and enter the LCD  3 . In other words, 80% of incident daylight  12  reflects off the lens-film  31 , whereas merely 20% of the self-made light  13  sent out by the light-guide plate  41  passes through the lens-film  31  and enters the LCD  3 . For example, suppose the LCD  3  is exposed to 10000 cd/cm2 of daylight  12 , the lens-film  31  will reflect 8000 cd/cm2 of daylight  12  which will then be available to the LCD  3 . By the same token, suppose 2000 cd/cm2 of the self-made light  13  is sent out by the light-guide plate  41 , only 400 cd/cm2 of it will pass through the lens-film  31  and then be available to the LCD  3 . Hence, in this example, a mere total of 8400 cd/cm2 of light is available to the LCD  3 , though the LCD  3  is exposed to 10000 cd/cm2 of daylight  12 . The difference between the two figures accounts for the poor contrast of any image shown on a LCD screen under daylight. More badly, the stronger daylight  12  is, the worse is the contrast.  
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0009]FIG. 1 illustrates how a known LCD works;  
     [0010]FIG. 3 illustrates how another known LCD works;  
     [0011]FIG. 3 depicts the structure of a preferred embodiment of the creation; and  
     [0012]FIG. 4 illustrates how the preferred embodiment works.  
    
    
     SUMMARY OF THE INVENTION  
     [0013] The primary object of the creation is to provide a LCD with a back light source characterized by light source local penetration. There is a reflective layer on the bottom of the LCD. The reflective layer contains some light channels. A micro lens-film is placed between the LCD and the back light source. The micro lens-film contains some light collection sections in such a way that individual light collection sections are opposite individual light channels of the reflective layer. The creation has two merits. Firstly, when the front of the LCD is exposed to strong daylight, the reflective layer reflects incident daylight to an extent so great that incident daylight is available to the LCD. Secondly, the light emitted by the light-guide plate is condensed by the light collection sections of the micro lens-film before passing through the light channels, and eventually be available to the LCD. As a result, not only is the LCD illuminated better, but the images it shows also have better contrast under daylight. Hence, the images displayed on the LCD screens are greatly improved.  
     [0014] The foregoing object and summary provide only a brief introduction to the present invention. To fully appreciate these and other objects of the present invention as well as the invention itself, all of which will become apparent to those skilled in the art, the following detailed description of the invention and the claims should be read in conjunction with the accompanying drawings. Throughout the specification and drawings identical reference numerals refer to identical or similar parts.  
     [0015] Many other advantages and features of the present invention will become manifest to those versed in the art upon making reference to the detailed description and the accompanying sheets of drawings in which a preferred structural embodiment incorporating the principles of the present invention is shown by way of illustrative example.  
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
     [0016] The following descriptions are of exemplary embodiments only, and are not intended to limit the scope, applicability or configuration of the invention in any way. Rather, the following description provides a convenient illustration for implementing exemplary embodiments of the invention. Various changes to the described embodiments may be made in the function and arrangement of the elements described without departing from the scope of the invention as set forth in the appended claims.  
     [0017] Please refer to FIG. 3 first. As regards the creation, there is a high-quality reflective layer  51  on the bottom of the LCD  5 . The reflective layer  51  contains a plurality of light channels  52 . The LCD  5  and the reflective layer  51  are joined together by a glass shade  53  and become one single structure. There are various solutions as to the material and formation of the reflective layer  51 , though this is beyond the scope of the discussion on the creation and thus this is not to be mentioned again in the following paragraphs. A micro lens-film  6  is also installed on the bottom of the LCD  5 . The micro lens-film  6  contains some light collection sections  61 , which act as condensers, in such a way that individual light collection sections  61  are opposite individual light channels  52  of the reflective layer  51 . Aback light source  7  is installed behind the micro lens-film  6 . The back light source  7  works together with a light-guide plate  71 . There is a cooled-cathode fluorescent tube  72  beside the light-guide plate  71 . There are a diffusing film  8  and a condenser  9  between the micro lens-film  6  and the back light source  7 . They are not discussed below as they do not belong to the following claims.  
     [0018] Please refer to FIG. 4, which depicts the most important points of the present invention. Whenever daylight L 4  enters the LCD  5 , most of it reflects off the reflective layer  51  and returns to LCD  5 . While passing through the light collection sections  61  of the micro lens-film  6 , the self-made light, which is sent out by the light-guide plate  71 , is turned into energy-enriched, self-made light L 5 . Then, the energy-enriched, self-made light L 5  passes through the light channels  52  of the reflective layer  51  before it eventually becomes available to the LCD  5 . In other words, the illumination of the LCD  5  is a combination of the incident self-made light L 5 , which is sent out by the light-guide plate  71 , be condensed and passes through the light channels  52  before it becomes available to the LCD  5 , and the incident daylight LA. Given the design, the illumination required by the LCD  5  is augmented, and under daylight LA the contrast of LCD screens display is improved.  
     [0019] It will be understood that each of the elements described above, or two or more together may also find a useful application in other types of methods differing from the type described above.  
     [0020] While certain novel features of this invention have been shown and described and are pointed out in the annexed claim, it is not intended to be limited to the details above, since it will be understood that various omissions, modifications, substitutions and changes in the forms and details of the device illustrated and in its operation can be made by those skilled in the art without departing in any way from the spirit of the present invention.