Abstract:
A direct type backlight has a plate and a plurality of light emitting diode (LED) rows. The LED rows are disposed on the plate, and every two adjacent LED rows have a row gap positioned therebetween. The one of these gaps, which is nearest to the center of the direct type backlight, is a minimum gap.

Description:
RELATED APPLICATIONS 
   The present application is based on, and claims priority from, Taiwan Application Serial Number 94121465, filed Jun. 27, 2005, the disclosure of which is hereby incorporated by reference herein in its entirety. 
   BACKGROUND 
   1. Field of Invention 
   The present invention relates to a direct type backlight. More particularly, the present invention relates to a distribution of light emitting diodes (LEDs) for the backlight. 
   2. Description of Related Art 
   The principle for operating a backlight module is to direct the light emitted from a backlight as a planar light source via a light guide plate, thereby assuring the uniformity of lightness. A backlight commonly used in the backlight module can be such as a cold cathode fluorescent lamp (CCFL) and light emitting diodes (LEDs), etc. Although the CCFL is the main trend currently, yet the demands for using the LEDs have been increasing daily. In comparison with the CCFL, the LEDs have the advantages of small size, long operation life, low driving voltage, low power consumption and excellent shock resistance, etc. 
     FIG. 1  is a schematic diagram showing a conventional direct type backlight using light emitting diodes, and the direct type backlight includes a plate  102  and several LED rows  104  disposed on the plate  102 . Each of the LED rows  104  comprises several light emitting diodes  114 , and row gaps a 1 , a 2 , a 3  and a 4  between two of the LED rows  104  are all the same, i.e. a 1 =a 2 =a 3 =a 4 . 
   The aforementioned light emitting diodes are evenly spaced on the plate according to a conventional distribution, i.e. the row gaps between any two adjacent LED rows  104  are all the same. However, this conventional distribution with equal gaps makes the central lightness of LED fail to achieve optimum application. Since user&#39;s visual sensation is mainly dependent on the central position of a panel, the lightness distribution obtained by this conventional distribution cannot optimize the user&#39;s visual sensation. 
   SUMMARY 
   Hence, the present invention is to provide a direct type backlight for achieving better lightness distribution by using a better LED distribution. 
   In accordance with a preferred embodiment, the direct type backlight comprises a plate and a plurality of LED rows. The LED rows are disposed on the plate, and there is a row gap between every two adjacent LED rows. Meanwhile, one of the row gaps nearest to a center of the direct type backlight is minimum in size. 
   In accordance with another preferred embodiment, the direct type backlight comprises a plate and a plurality of LED rows. The LED rows are disposed on the plate, and there is a row gap between every two adjacent LED rows. Meanwhile, one of the row gaps nearest to a center of the direct type backlight is smaller than the other row gaps. 
   In accordance with still another preferred embodiment, the direct type backlight comprises a plate and a plurality of LED rows. The LED rows are disposed on the plate, and there is a row gap between every two adjacent LED rows. Meanwhile, the row gaps are increased sequentially from a center of the direct type backlight to the margins thereof. 
   It is to be understood that both the foregoing general description and the following detailed description are examples, and are intended to provide further explanation of the invention as claimed. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other features, aspects, and advantages of the present invention will become better understood with regard to the following description, appended claims, and accompanying drawings where: 
       FIG. 1  is a schematic diagram showing a conventional direct type backlight using light emitting diodes; 
       FIGS. 2A and 2B  are schematic diagrams showing preferred embodiments of the present invention; 
       FIGS. 3A and 3B  are schematic diagrams showing other preferred embodiments of the present invention; 
       FIGS. 4A and 4B  are schematic diagrams showing still other preferred embodiments of the present invention; 
       FIGS. 5A ,  5 B and  5 C are schematic diagrams showing further other preferred embodiments of the present invention; and 
       FIG. 6  is a schematic diagram showing a LED row according to a preferred embodiment of the present invention. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Reference will now be made in detail to the preferred embodiments of the present invention, 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. 
   The present invention changes the conventional distribution of LEDs in the backlight so as to enable a central position of the backlight to have the maximum relative lightness, thus making the central lightness of the LEDs achieve optimum application and also optimizing user&#39;s visual sensation. 
     FIGS. 2A and 2B  are schematic diagrams showing preferred embodiments of the present invention for explaining the case in which row gaps between every two adjacent LED rows are increased sequentially from a center of a direct type backlight to the margins thereof. 
   Such as shown in  FIG. 2A , a direct type backlight  200   a  comprises a plate  202  and several LED rows  204 . The LED rows  204  are disposed on the plate  202 , and a row gap between every two adjacent LED rows  204  is a 1 , a 2 , a 3  or a 4 , and the row gaps are increased sequentially from a center of the direct type backlight  200   a  to the margins thereof, i.e. a 1 &lt;a 2 &lt;a 3 &lt;a 4 . 
   Such as shown in  FIG. 2B , a direct type backlight  200   b  comprises a plate  202  and several LED rows  204 . The LED rows  204  are disposed on the plate  202 , and a row gap between every two adjacent LED rows  204  is a 1 , a 2  or a 3 , and the row gaps are increased sequentially from a center of the direct type backlight  200   a  to the margins thereof, i.e. a 1 &lt;a 2 &lt;a 3 . 
   Moreover, each of the LED rows  204  comprises several LEDs  214 , and gaps between every two adjacent LEDs  214  are equal in size. There are an even number of LED rows  204  shown in  FIG. 2A , and thus the center of the direct type backlight  200   a  has only one narrowest row gap a 1 . There are an odd number of LED rows  204  shown in  FIG. 2B , and thus the position nearest to the center of the direct type backlight  200   b  may have two narrowest row gaps a 1 . 
     FIGS. 3A and 3B  are schematic diagrams showing other preferred embodiments of the present invention for indicating that the central position of the direct type backlight has the narrowest row gap(s), and at least two row gaps at non-central positions thereof are equal in size. 
   Such as shown in  FIG. 3A , a direct type backlight  300   a  comprises a plate  302  and several LED rows  304 . The LED rows  304  are disposed on the plate  302 , and a row gap between every two adjacent LED rows  304  is a 1 , a 2 , a 3  or a 4 . The row gap a 1  at a center of the direct type backlight  300   a  is minimum in size, and the row gaps a 3  and a 4  at non-central positions thereof are equal in size, i.e. a 1 &lt;a 2 &lt;a 3 =a 4 . 
   Such as shown in  FIG. 3B , a direct type backlight  300   b  comprises a plate  302  and several LED rows  304 . The LED rows  304  are disposed on the plate  302 , and a row gap between every two adjacent LED rows  304  is a 1 , a 2  or a 3 . The row gaps a 1  nearest to a center of the direct type backlight  300   b  are minimum in size, and the row gaps a 2  and a 3  at non-central positions thereof are equal in size, i.e. a 1 &lt;a 2 =a 3 . 
   Moreover, each of the LED rows  304  comprises several LEDs  314 , and gaps between every two adjacent LEDs  314  are equal in size. There are an even number of LED rows  304  shown in  FIG. 3A , and thus a center of the direct type backlight  300   a  has only one narrowest row gap a 1 . There are an odd number of LED rows  304  shown in  FIG. 3B , and thus the position nearest to the center of the direct type backlight  300   b  may have two narrowest row gaps a 1 . 
     FIGS. 4A and 4B  are schematic diagrams showing still other preferred embodiments of the present invention for indicating that the central position of the direct type backlight has the narrowest row gap(s), and the other row gaps at non-central positions thereof are not increased sequentially from the center of the direct type backlight to the margins thereof. 
   Such as shown in  FIG. 4A , a direct type backlight  400   a  comprises a plate  402  and several LED rows  404 . The LED rows  404  are disposed on the plate  402 , and a row gap between every two adjacent LED rows  404  is a 1 , a 2 , a 3  or a 4 . The row gap a 1  at a center of the direct type backlight  300   a  is minimum in size, and the other row gaps a 2 , a 3  and a 4  at non-central positions the direct type backlight  400   a  are increased sequentially from the margins thereof to the center thereof, i.e. a 1 &lt;a 2 ; a 1 &lt;a 3 ; a 1 &lt;a 4 ; and a 2 &gt;a 3 &gt;a 4 . 
   Such as shown in  FIG. 4B , a direct type backlight  400   b  comprises a plate  402  and several LED rows  404 . The LED rows  404  are disposed on the plate  402 , and a row gap between every two adjacent LED rows  404  is a 1 , a 2  or a 3 . The row gaps a 1  nearest to a center of the direct type backlight  400   b  is minimum in size, and the other row gaps a 2  and a 3  at non-central positions the direct type backlight  400   b  are increased sequentially from the margins thereof to the center thereof, i.e. a 1 &lt;a 2 ; a 1 &lt;a 3 ; and a 2 &gt;a 3 &gt;a 4 . 
   Moreover, each of the LED rows  404  comprises several LEDs  414 , and gaps between every two adjacent LEDs  414  are equal in size. There are an even number of LED rows  404  shown in  FIG. 4A , and thus a center of the direct type backlight  400   a  has only one narrowest row gap a 1 . There are an odd number of LED rows  404  shown in  FIG. 4B , and thus the position nearest to the center of the direct type backlight  400   b  may have two narrowest row gaps a 1 . 
   It can be known from the above preferred embodiments that: as long as the row gap at the center of the direct type backlight is smallest, various size relationships of the row gaps at other positions all are applicable within the inventive spirit of the present invention, and thus should be included in the scope of protection claimed in the present invention. Concretely speaking, as long a certain row gap located on a non-central position that is not nearest to the center of the direct type backlight is larger than the row gap nearest to the center thereof, another row gap located on the non-central position also can be equal to the smallest row gap in accordance with the design requirements. 
   In the above embodiments, the LEDs for each of the LED rows are spaced from each other at an equal distance. The following description is stated for further explaining various enablement changes of the gap between every two adjacent LEDs in one LED row. 
     FIGS. 5A ,  5 B and  5 C are schematic diagrams showing further other preferred embodiments of the present invention, corresponding to the embodiments shown in  FIG. 2A ,  FIG. 3A  and  FIG. 4A  respectively, wherein the gaps between the LEDs in one LED row are not the same in size. In a direct type backlight  500   a  shown in  FIG. 5A , the size relationship of row gaps for LED rows  504  is a 1 &lt;a 2 &lt;a 3 &lt;a 4 . In a direct type backlight  500   b  shown in  FIG. 5B , the size relationship of row gaps for LED rows  504  is a 1 &lt;a 2 &lt;a 3 =a 4 . In a direct type backlight  500   c  shown in  FIG. 5C , the size relationship of row gaps for LED rows  504  is a 1 &lt;a 2 ; a 1 &lt;a 3 ; a 1 &lt;a 4 ; and a 2 &gt;a 3 &gt;a 4 . 
   Each of the aforementioned LED rows  504  comprises several LEDs  514 , and the gaps between the LEDs  514  are preferably increased in sequence from a center of a direct type backlight to the margins thereof, thereby enhancing the relative lightness at the central position of the backlight. Nonetheless, those who are skilled in the art should be able to learn that the gaps between the LEDs  514  can be adjusted in accordance with the actual needs, and are not limited to the gaps sequentially increasing from the center of the backlight to the margins thereof as described in the present embodiment. 
     FIG. 6  is a schematic diagram showing a LED row according to a preferred embodiment of the present invention. The LED row used in the above preferred embodiments can be a LED light bar  604  on which several LEDs  614  are disposed. The LED light bar  604  has an advantage of briefly assembling, which can increase the manufacturing speed of backlight, thus promoting manufacturing efficiency. 
   To sum up, the LED distributions shown in the preferred embodiments can make a backlight achieve better lightness distribution, thus not only enabling the central lightness of LED to achieve optimum application, but also optimizing the user&#39;s visual sensation. 
   It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention cover modifications and variations of this invention provided they fall within the scope of the following claims and their equivalents.