Abstract:
An exemplary double-layer lamp ( 210 ) includes an inner cold cathode fluorescent lamp (CCFL) ( 211 ), an outer glass tube ( 212 ) accommodating the inner CCFL therein, and a reflecting member ( 214 ) disposed between the inner CCFL and the outer glass tube. An exemplary backlight module ( 200 ) applies the above double-layer lamp. The backlight module has a smaller volume.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a double-layer lamp, and a backlight module having the double-layer lamp. 
       GENERAL BACKGROUND 
       [0002]    Liquid crystal devices (LCDs) are commonly used as displays for compact electronic apparatuses. This is because LCDs not only provide good quality images using little power, but are also conveniently thin. Because liquid crystal in an LCD does not emit any light itself, the liquid crystal requires a light source to clearly and sharply display texts and images. Therefore, LCDs typically require a backlight module. 
         [0003]    Referring to  FIG. 9 , a typical backlight module  100  includes a light source  112 , a reflecting shell  114 , and a light guide plate (LGP)  120  with a light incident surface  121 . The light source  112  is disposed in a space cooperatively formed by the reflecting shell  114  and the LGP  120 . The light source  112  is adjacent to the light incident surface  121  of the LGP  120 . The light source  112  is generally a cold cathode fluorescent lamp (CCFL) emitting light uniformly in all directions. The reflecting shell  114  is used to reflect and concentrate light, so that the light propagates along predetermined directions toward the light incident surface  121  of the LGP  120 . 
         [0004]    Referring to  FIG. 10 , this is an enlarged, cross-sectional view of the light source  112 . The light source  112  is a double-layer lamp, which includes an inner cold cathode fluorescent lamp (CCFL)  1121  and an outer glass tube  1122 . The outer glass tube  1122  accommodates the inner CCFL  1121 . Thus, the outer glass tube  1122  can protect the inner CCFL  1121  from being broken. The outer glass tube  1122  can also isolate the inner CCFL  1121  from ambient air, so that a temperature of the inner CCFL  1121  is stably maintained. 
         [0005]    However, the reflecting shell  114  adds to the cost of the backlight module  100 , and also adds to the overall volume occupied by the backlight module  100 . 
         [0006]    What is needed, therefore, is a double-layer lamp that can overcome the above-described deficiencies. What is also needed is a backlight module employing the double-layer lamp. 
       SUMMARY 
       [0007]    In one preferred embodiment, a double-layer lamp includes an inner cold cathode fluorescent lamp (CCFL), an outer glass tube, accommodating the inner CCFL therein, and a reflecting member disposed between the inner CCFL and the outer glass tube. 
         [0008]    Other novel features and advantages will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is an exploded, isometric view of a backlight module according to a first embodiment of the present invention, the backlight module including a light source. 
           [0010]      FIG. 2  is an enlarged, cross-sectional view of part of the backlight module of  FIG. 1  after the backlight module has been assembled, showing a cross-section of the light source. 
           [0011]      FIG. 3  is an enlarged view of the light source shown in  FIG. 2 . 
           [0012]      FIG. 4  is similar to  FIG. 3 , but showing a corresponding view in the case of a light source of a backlight module according to a second embodiment of the present invention. 
           [0013]      FIG. 5  is similar to  FIG. 3 , but showing a corresponding view in the case of a light source of a backlight module according to a third embodiment of the present invention. 
           [0014]      FIG. 6  is similar to  FIG. 3 , but showing a corresponding view in the case of a light source of a backlight module according to a fourth embodiment of the present invention. 
           [0015]      FIG. 7  is similar to  FIG. 3 , but showing a corresponding view in the case a light source of a backlight module according to a fifth embodiment of the present invention. 
           [0016]      FIG. 8  is similar to  FIG. 3 , but showing a corresponding view in the case of a light source of a backlight module according to a sixth embodiment of the present invention. 
           [0017]      FIG. 9  is a schematic, side cross-sectional view of part of a conventional backlight module, the backlight module including a light source. 
           [0018]      FIG. 10  is an enlarged view of the light source shown in  FIG. 9 . 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0019]    Reference will now be made to the drawing figures to describe the various embodiments of the present invention in detail. 
         [0020]    Referring to  FIG. 1 , this shows a backlight module  200  according to a first embodiment of the present invention. The backlight module  200  includes an optical film assembly  230 , a light guide plate (LGP)  220 , a reflecting plate  240 , and a light source  210 . The optical film assembly  230  includes a first brightness enhancing film  231 , a second brightness enhancing film  232 , and a diffusing film  233 , disposed in that order from top to bottom. 
         [0021]    Referring also to  FIG. 2 , the LGP  220  includes a light emitting surface  222 , a bottom surface  223  opposite to the light emitting surface  222 , and a light incident surface  221  adjacent the light emitting surface  222 . The optical film assembly  230  is disposed on the light emitting surface  222 . The reflecting plate  240  is disposed on the bottom surface  223 . The light source  210  is disposed adjacent the light incident surface  221 . The light source  210  is parallel to both the light incident surface  221  and the light emitting surface  222 . The light source  210  is a linear lamp. 
         [0022]    Referring also to  FIG. 3 , the light source  210  is a double-layer lamp. The light source  210  includes an outer glass tube  212 , an inner CCFL  211 , and a reflecting element  214 . The inner CCFL  211  is received in the outer glass tube  212 . In particular, two opposite ends of the inner CCFL  211  can be fixed at two opposite ends of the outer glass tube  212  using a pair of holding elements (not visible). The reflecting element  214  is disposed on part of an inner surface (not labeled) of the outer glass tube  212 , in a position farthest from the light incident surface  221 . In the illustrated embodiment, the reflecting element  214  is disposed on half of the inner surface of the outer glass tube  212 . That is, a transverse cross-section of the reflecting element  214  is a semicircle. The reflecting element  214  can be a piece of reflecting material attached to the inner surface of the outer glass tube  212 . For example, the piece of reflecting material can be an aluminum sheet, which is adhered to the inner surface of the outer glass tube  212 . In another example, the reflecting element  214  can be a reflecting layer made from silver, which is coated on the inner surface of the outer glass tube  212 . 
         [0023]    In operation of the backlight module  200 , part of light emitted by the inner CCFL  211  transmits directly out of the light source  210  through the outer glass tube  212  before entering the light incident surface  221  of the LGP  220 . Another part of the light emitted by the inner CCFL  211  is reflected by the reflecting element  214 , and then transmits out of the light source  210  through the outer glass tube  212  before entering the light incident surface  221 . The overall effect is that the light emitted by the inner CCFL  211  transmits to the LGP  220  uniformly and in a relatively concentrated beam. Unlike in conventional art, the backlight module  200  employing the double-layer lamp as the light source  210  does not need a reflecting shell. This can reduce the cost of the backlight module  200 , and minimize an overall volume occupied by the backlight module  200 . 
         [0024]    Referring to  FIG. 4 , a light source  310  of a backlight module according to a second embodiment of the present invention is similar to the light source  210  of the first embodiment. However, a reflecting element  314  of the light source  310  is disposed on part of an outer surface (not labeled) of an inner CCFL  311 , in a position farthest from a corresponding light incident surface of an LGP. In the illustrated embodiment, the reflecting element  314  is disposed on half of the outer surface of the inner CCFL  311 . In operation of the backlight module, part of light emitted by the inner CCFL  311  transmits directly out of the light source  310  through an outer glass tube  312  before entering the light incident surface. Another part of the light emitted by the inner CCFL  311  is reflected by the reflecting element  314 , and then transmits out of the light source  310  through the outer glass tube  312  before entering the light incident surface. The overall effect is that the light emitted by the inner CCFL  311  transmits to the LGP uniformly and in a relatively concentrated beam. 
         [0025]    Referring to  FIG. 5 , a light source  410  of a backlight module according to a third embodiment of the present invention is similar to the light source  210  of the first embodiment. However, the light source  410  includes two reflecting elements  414 ,  416 . The reflecting element  414  is disposed on part of an inner surface (not labeled) of an outer glass tube  412 . The reflecting element  416  is disposed on part of an outer surface (not labeled) of an inner CCFL  411 . In operation of the backlight module, part of light emitted by the inner CCFL  411  transmits directly out of the light source  410  through the outer glass tube  412  before entering a corresponding light incident surface of an LGP. Another part of the light emitted by the inner CCFL  411  is reflected by the reflecting element  416 , and most of such light then transmits out of the light source  410  through the outer glass tube  412  before entering the light incident surface. Any of such light that does not transmit thus is reflected by the reflecting element  414 , and then transmits out of the light source  410  through the outer glass tube  412  before entering the light incident surface. The overall effect is that the light emitted by the inner CCFL  411  transmits to the LGP  220  uniformly and in a relatively concentrated beam. 
         [0026]    Referring to  FIG. 6 , a light source  510  of a backlight module according to a fourth embodiment of the present invention is similar to the light source  210  of the first embodiment. However, a reflecting element  514  of the light source  510  is disposed at a middle region of a space between an outer glass tube  512  and an inner CCFL  511 . In the illustrated embodiment, the reflecting element  514  is generally C-shaped. That is, the reflecting element  514  covers more than half of the inner CCFL  511 . Two opposite ends of the reflecting element  514  can be fixed at two opposite ends of the outer glass tube  512  using a pair of holding elements (not visible). The space is a vacuum. 
         [0027]    Referring to  FIG. 7 , a light source  610  of a backlight module according to a fifth embodiment of the present invention is similar to the light source  210  of the first embodiment. However, a reflecting element  614  of the light source  610  is generally C-shaped. That is, a transverse cross-section of the reflecting element  614  is an arc that is greater than a semicircle. 
         [0028]    Referring to  FIG. 8 , a light source  710  of a backlight module according to a sixth embodiment of the present invention is similar to the light source  610  of the fifth embodiment. However, a reflecting element  714  of the light source  710  is generally C-shaped, with opposite ends of the reflecting element  714  being discontinuous. That is, a transverse cross-section of the reflecting element  714  is an arc that is greater than a semicircle. The reflecting element  714  can be considered to include a central semicircular portion, and portions at opposite sides of the semicircular portion respectively. The portions at opposite sides of the semicircular portion are discontinuous. 
         [0029]    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 changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.