Abstract:
An inverter cover shield device includes a receiving portion for receiving an inverter; a wire guiding portion for guiding at least one internal wire extending from the inverter, the wire guiding portion including a contact portion and a non contact portion, the contact portion supporting the at least one internal wire, and the contact portion being positioned between the non-contact portion and the receiving portion.

Description:
[0001]     The present invention claims the benefit of Korean Patent Application No. 2004-0029771 filed in Korea on Apr. 29, 2004, which is hereby incorporated by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to liquid crystal display module, more particularly, to an inverter cover shield for liquid crystal display module.  
         [0004]     2. Description of the Related Art  
         [0005]     In general, flat panel displays are increasingly being used for portable devices because they are thin, lightweight, consume low power. Among the various types of flat panel display devices, liquid crystal display (LCD) devices are widely used for laptop computers and desktop monitors because of their superior resolution, and color display quality.  
         [0006]     An LCD device uses the optical anisotropy and polarization properties of liquid crystal molecules to produce an image. Liquid crystal molecules have a definite orientation that results from their peculiar characteristics. The specific orientation can be modified by applying an electric field across the liquid crystal molecules. Due to optical anisotropy, the transmissivity of the LCD device to an incident depends upon the orientation of the liquid crystal molecules.  
         [0007]     The LCD device has an upper substrate and a lower substrate with electrodes that are spaced apart and face each other. A liquid crystal material is interposed between the upper and the lower substrates. When an electric field is applied to the liquid crystal material due to a voltage across the electrodes corresponding to the upper and lower substrates, respectively, an alignment direction of the liquid crystal molecules is changed in accordance with the applied voltage. By controlling the applied voltage, the LCD device provides various transmittances to rays of light, thereby displaying an image.  
         [0008]     The LCD device, however, does not emit the light by itself. The LCD device requires a light source. Usually, a backlight device is positioned behind the LCD panel. Backlight devices are classified into direct backlight type (or direct type) units and edge light type (or edge type) units, depending on the position of a lamp with regard to the LCD panel. With the direct type backlight, incident rays irradiating from the lamp are directly incident on the LCD panel. With the edge type backlight unit, rays from the lamp are incident on the LCD panel via a light guide or a reflector.  
         [0009]     Nowadays, the direct type backlight is more common than the edge type backlight. However, since the direct type backlight assembly includes a plurality of lamps behind the LCD panel, the LCD module gets thicker. Therefore, a major issue is to design thinner LCD modules.  
         [0010]      FIG. 1  is a cross sectional view of a peripheral portion of a related art LCD module. As shown in  FIG. 1 , the LCD module includes an LCD panel  100  for displaying images and a backlight assembly that emits artificial light toward the LCD panel  100 . A top case  290  surrounds the LCD panel  100  and the backlight assembly and fastens the LCD panel  100  to the backlight assembly.  
         [0011]     The backlight assembly mainly consists of lamps  210 , a reflector  220 , a diffusion sheet  240 , a mold frame  280 , a lamp supporter  281  and a panel guide  285 . The mold frame  280  accommodates and buttresses portions of the backlight assembly. The lamp supporter  281  is located in an inner portion of the mold frame  280  and supports both edges of each lamp  210 . The lamps  210  are disposed in parallel with each other underneath the LCD panel  100 . The reflector  220  is disposed underneath the lamps  210  and reflects light emitted by the lamps toward the LCD panel  100  to prevent the light loss. The diffusion sheet  240  is located over the lamps  210 , and disperses and diffuses the emitted and reflected light. The panel guide  285  is disposed over the diffusion sheet  240  and accommodates the prism sheet  250  and the LCD panel  100 .  
         [0012]     The LCD module further includes a bottom cover  230  underneath the mold frame  280 . The bottom cover  230  protects and shields the lamps  210 . An inverter  260  is disposed underneath the bottom cover  230  to supply electric power to the lamps  210  through internal wires  265 . A cover shield  270  surrounds the inverter  260  at the bottom of the bottom cover  230  and protects the inverter  260  from external impact. The cover shield  270  and the bottom cover  230  isolate the inverter  260  by embracing and covering the inverter on all sides. The cover shield  270  is made of a metallic material to absorb electromagnetic waves.  
         [0013]     As shown in  FIG. 1 , the cover shield  270  consists of an inner side  271 , a bottom side  272  and an outer side  273 . The bottom side  272  corresponds to the bottom side of the inverter  260 . The inner side  271  is disposed below the bottom cover  230 . The outer side  273  corresponds to an outer portion of the bottom cover  230  and bends upward to cover the sidewalls of the bottom cover  230  and mold frame  280 . Furthermore, the outer side  273  of the cover shield  270  is in contact with the internal wire  265   s  extending from the inverter  260  to the lamps  210 .  
         [0014]     The cover shield  270  may cause a parasitic capacitance in the internal wires  265  because the outer side  273  of the cover shield  270  contacts the internal wires  265 . Current may be drawn of the internal wires  265  through the contact with the cover shield  270 , thereby generating a current leakage in the internal wires  265 . Accordingly, the lamps  210  may not receive enough current. The impedance caused by both the cover shield  270  and the internal wires  265  may be calculated by the following equation:
 
 Xc= 1/(2 πfC )
 
 where “f” represents a frequency of the alternating current that is flowing through the internal wires  265 , and “C” represents the parasitic capacitance generated between the outer side  273  and the internal wires  265 . In the above equation, the impedance(Xc) will decrease if the frequency (f) increases or if the parasitic capacitance (C) increases with the contact area between the outer side  273  and the internal wires  265 . Therefore, the current leakage will increase when the impedance decreases. 
 
         [0015]     When current leakage increases, the inrush current in lamps  210  will be reduced and the luminance of the light emitted by the lamps  210  will be reduced. To prevent these disadvantages, the related art frequently employs insulating papers or other related appliances between the cover shield  270  and the internal wires  265 . However, such insulating papers or related appliances require additional fabrication, thus increasing production cost.  
       SUMMARY OF THE INVENTION  
       [0016]     Accordingly, the present invention is directed to an inverter cover shield module for a liquid crystal display module that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.  
         [0017]     An object of the present invention is to provide an inverter cover shield device for maintaining stable images on a liquid crystal display panel.  
         [0018]     Another object of the present invention is to provide an inverter cover shield device for achieving a minimum luminance variation on a liquid crystal display panel.  
         [0019]     Another object of the present invention is to provide an inverter cover shield device that reduces a parasitic capacitance with internal wires of a liquid crystal display module.  
         [0020]     Another object of the present invention is to provide an inverter cover shield device that reduces a current leakage from internal wires of a liquid crystal display module.  
         [0021]     Additional features and advantages of the invention will be set forth in the description that follows, and in part will be apparent from that description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as shown in the appended drawings.  
         [0022]     To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, an inverter cover shield device includes a receiving portion for receiving an inverter; a wire guiding portion for guiding at least one internal wire extending from the inverter, the wire guiding portion including a contact portion and a non contact portion, the contact portion supporting the at least one internal wire, and the contact portion being positioned between the non-contact portion and the receiving portion.  
         [0023]     In another aspect, an inverter assembly includes an inverter and an inverter cover shield device. The inverter includes at least one internal wire extending from the inverter. The inverter cover shield device includes a receiving portion for receiving the inverter; a wire guiding portion for guiding the at least one internal wire, the wire guiding portion including a contact portion and a non-contact portion, the contact portion supporting the at least one internal wire, and the contact portion being positioned between the non-contact portion and the receiving portion.  
         [0024]     In another aspect, a backlight assembly device for a liquid crystal display module includes at least one lamp for emitting light, at least one reflector for reflecting the light emitted from the lamp, a diffusion sheet between the reflector and the at least one lamp, a bottom cover underneath the reflector, an inverter for applying electric power to the at least one lamp through at least one internal wire, and an inverter cover shield. The inverter cover shield includes a receiving portion for receiving the inverter; a wire guiding portion for guiding the at least one internal wire extending from the inverter, the wire guiding portion including a contact portion and a non-contact portion, the contact portion supporting the at least one internal wire, and the contact portion being positioned between the non-contact portion and the receiving portion.  
         [0025]     It is to be understood that both the foregoing general description and the following detailed description are exemplary and are intended to provide further explanation of the invention as claimed. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0026]     The accompanying drawings, which are included to provide a further understand of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention.  
         [0027]      FIG. 1  is a cross sectional view of a peripheral portion of a related art LCD module.  
         [0028]      FIG. 2  is a perspective view of a liquid crystal display (LCD) module according to an embodiment of the present invention.  
         [0029]      FIG. 3  is a cross sectional view taken along line IV-IV of  FIG. 2  and showing an exemplary peripheral portion of the LCD module according to an embodiment of the present invention.  
         [0030]      FIG. 4  is a bottom view of an exemplary liquid crystal display module according to an embodiment of the present invention.  
         [0031]      FIG. 5  is a top view of an exemplary cover shield according to an embodiment of the present invention.  
         [0032]      FIG. 6  shows an exemplary contact area between a cover shield and an internal wire according to an embodiment of the present invention.  
         [0033]      FIG. 7A  shows an exemplary cover shield according to another embodiment of the present invention.  
         [0034]      FIG. 7B  shows an exemplary cover shield according to yet another embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0035]     Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings.  
         [0036]      FIG. 2  is a perspective view of a liquid crystal display (LCD) module according to an embodiment of the present invention. Refering to  FIG. 2 , the LCD module includes an LCD panel  300  (shown in  FIG. 3 ) and a backlight assembly. The LCD panel  300  displays images.  
         [0037]      FIG. 3  is a cross sectional view taken along line IV-IV of  FIG. 2  and showing an exemplary peripheral portion of the LCD module according to an embodiment of the present invention. Referring to  FIG. 3 , the LCD panel  300  also includes an upper substrate  310  and a lower substrate  320 . A liquid crystal layer (not shown) is provided between the upper and lower substrates  310  and  320 .  
         [0038]     The backlight assembly emits artificial light toward the LCD panel  300 . The backlight assembly includes a plurality of lamps  410 , a reflector  420 , a diffusion sheet  440 , a prism sheet  450 , a mold frame  480 , a plurality of lamp supporter  481  and a panel guide  485 . A top case  490  surrounds the LCD panel  300  and the backlight assembly. The top case  490  fastens the LCD panel  300  to the backlight assembly.  
         [0039]     The mold frame  480  accommodates and buttresses portions of the backlight assembly. The lamp supporters  481  are located in an inner peripheral portion of, and at both ends of the mold frame  480 . One of the plurality of lamps  410  is supported at its ends by two of the lamp supporters  481 . The lamps  410  are disposed underneath the LCD panel  300  and are electrically connected to one another in parallel.  
         [0040]     The reflector  420  reflects artificial light emitted from the lamps  410  toward the LCD panel  300 . As such, the reflector  420  prevents loss of light. The reflector  420  is disposed underneath the lamp  410  on an inner surface of the mold frame  480 .  
         [0041]     The diffusion sheet  440  disperses and diffuses light emitted by the lamps  410  and light reflected by the reflector  420 . The diffusion sheet  440  is located over the lamp  410 . The panel guide  485  is disposed over the diffusion sheet  440  and accommodates the prism sheet  450  and the LCD panel  300 .  
         [0042]      FIG. 4  is a bottom view of an exemplary liquid crystal display module according to an embodiment of the present invention. Referrring to  FIG. 4 , the LCD module further includes a bottom cover  430 , a plurality of inverters  460 , and a plurality of internal wires  465 . The bottom cover  430  is located underneath the mold frame  480 . The bottom cover  430  protects and shields the lamps  410 .  
         [0043]     The inverters  460  are disposed underneath the bottom cover  430 . The inverters  460  may be disposed at both sides of a bottom surface of the bottom cover  430 . In an embodiment of the present invention, one of the inverters applies a high voltage to the lamps  410  (shown in  FIG. 3 ) through the internal wires  465 . The other inverter applies a low voltage to the lamps  410  (shown in  FIG. 3 ).  
         [0044]     Referering back to  FIG. 3 , a cover shield  470  surrounds the inverters  460  at the bottom of the bottom cover  430 . The cover shield  470  protects the inverters  460  from external impact. The cover shield  470  and the bottom cover  430  isolate the inverters  460  by embracing and covering all sides of the inverter  460 . Therefore, the inverter  460  can be protected from the external impact and shock. The cover shield  470  may be made of a metallic material to absorb electromagnetic waves. The bottom cover  430  may also include a metallic material.  
         [0045]     The inverters  460  supply electric power to the lamps  410  through the internal wires  465 . The internal wires  465  extend from the inverters  460  along a bottom surface of the bottom cover  430 . Then, the internal wires  465  bend upward along the mold frame  480  to contact the electrodes  415  of the lamps  410 . One of the lamps  410  may be a cold cathode fluorescence lamp (CCFL), which includes electrodes  415  at both ends thereof. When electric power is applied from the inverter  460  to the electrodes  415  through the internal wireS  465 , the lamp  410  generates and emits artificial light.  
         [0046]     As shown in  FIG. 3 , the cover shield  470  includes an inner side  471 , a bottom side  472  and an outer side  473  to cover and protect the inverters  460 . The bottom side  472  corresponds to the bottom of one of the inverters  460 . The inner side  471  is disposed at the bottom of the bottom cover  430  and is connected to the bottom side  472 . The outer side  473  is disposed opposite to the inner side  471  and corresponds to an outer portion of the bottom cover  430 . In an embodiment of the present invention, the outer side  473  partially contacts the internal wires  465 , thereby guiding the internal wires  465 .  
         [0047]     As illustrated in an enlarged view of a portion CS in  FIG. 3 , the outer side  473  includes first portions  473   a  and second portions  473   b . The first portions  473   a  do not contact internal wires  465 . The second portion  473   b  is indented from the first portions  473   a  to contact the internal wires  465 . The first portions  473   a  can be referred to as non-contact portions, and the second portion  473   b  can be referred to as an indentation portion.  FIG. 3  shows only one indentation portion  473   b . However, a plurality of indentation portions may be provided.  
         [0048]     The outer side  473  bends upward to cover the sidewalls of the bottom cover  430  and the mold frame  480 . The outer side  473  is formed closer to the bottom cover  430  than the bottom side  472 . Accordingly, a distance of the first portions  473   a  to the bottom cover  430  is shorter than a distance of the bottom side  472  to the bottom cover  430 .  
         [0049]      FIG. 5  is a top view of an exemplary cover shield according to an embodiment of the present invention. As shown in  FIG. 5 , the indentation portion  473   b  is formed in the middle of the outer side  473  of the cover shield  470 . The dotted lines shown in  FIG. 5  represent folding lines where the cover shield  470  is bent. The inverter  460  (shown in  FIG. 3 ) is located within, preferably in the middle of, the bottom side  472  and is surrounded by the cover shield  470 . The internal wires  465  (shown in  FIG. 4 ) extend from the inverters  460 .  
         [0050]     As described above, only the indentation portion  473   b  contacts the internal wires  465 . Thus, the contact area between the cover shield  470  and the internal wires  465  is substantially reduced in an embodiment of the present invention in comparison to the related art. The non-contact portions  473   a  of the outer side  473  do not touch the internal wires  465 . As a result, a parasitic capacitance that may be generated between the cover shield  470  and the internal wires  465  decreases in accordance with the reduction in the contact area. Moreover, current leakage may also be reduced in comparison to the related art.  
         [0051]     Table 1 shows the lamp currents flowing through the lamps  410 . The lamp currents are measured relative to a distance between the cover shield  470  and the internal wire  465 . The experiments are performed twelve times under the same condition.  
                                                                                             TABLE 1                                       Distance Length (mm)                            Without           0   0.8   1.5   Cover Shield                        Current   Experiment 1   5.60   5.73   5.78   5.82       (mA)   Experiment 2   5.70   5.79   5.81   5.85           Experiment 3   5.69   5.74   5.78   5.81           Experiment 4   5.81   5.84   5.87   5.90           Experiment 5   5.84   5.86   5.89   5.93           Experiment 6   5.79   5.81   5.82   5.87           Experiment 7   5.81   5.82   5.83   5.87           Experiment 8   5.70   5.79   5.82   5.88           Experiment 9   5.74   5.80   5.81   5.83           Experiment 10   5.60   5.81   5.86   5.90           Experiment 11   5.73   5.82   5.85   5.90           Experiment 12   5.73   5.81   5.83   5.87            Average (mA)   5.73   5.80   5.83   5.87       Percent (%)   97.6   98.8   99.3   100                  
 
         [0052]     As indicated in TABLE 1, the larger the distance between the cover shield  470  and the internal wires  465 , the lower the current leakage. When the distance between the cover shield  470  and the internal wires  465  is 0.8 mm, the flow of current through the lamps  410  has about 98.8% efficiency compared to when the cover shield is not used.  
         [0053]     To display stable images on the LCD panel, the luminance of the light emitted from the lamps  410  should have a variation of less than 5%. To satisfy the 5% variation, the lamp current preferably varies by less then 0.1 mA. If the lamps  410  have a luminance of 100% without the cover shield  470 , the distance of the cover shield  470  to the internal wires  465  may be greater than 0.5 mm to maintain the luminance variation within 5%. Since the bottom cover  430  includes also a metallic material, the bottom cover  430  can be separated from the internal wires  465  to prevent the occurrence of the parasitic capacitance and the current leakage.  
         [0054]      FIG. 6  shows an exemplary contact area between a cover shield and an internal wire according to an embodiment of the present invention. Referring to  FIG. 6 , the non-contact portions  473   a  of the outer side  473  are separated from the internal wires  465  by a distance B. The bottom cover  430  is separated from the non-contact portion  473   a  by a distance A. If the distance B is equal or greater than a half the distance A (B&lt;(A/2)), the bottom cover  430  causes an increase of the current leakage. Thus, the non-contact portions  473   a  and the bottom cover  430  have to be designed to keep distance B less than half of distance A (B&lt;(A/2)). Especially, the distance B of the non-contact portions  473   a  to the internal wires  465  satisfies the following inequality: 0.5 (mm) &lt;B &lt;A/2. A distance B in this range can efficiently prevent the current leakage.  
         [0055]     The contact portions  473   a  of the bottom cover  430  can be of any shape. For example, the contact portions  473   a  of the bottom cover  430  can have one of a rectangular shape, a triangular shape, a curved shape, and a semicircular shape. Using any of each of these shapes, the current leakage can be made sufficiently small for a proper functionality of the inverter.  
         [0056]      FIG. 7A  shows an exemplary cover shield according to another embodiment of the present invention.  FIG. 7B  shows an exemplary cover shield according to yet another embodiment of the present invention. Referring to  FIG. 7A , the indentation portion  473   b  of the outer side  473  may have a triangular shape. Referring to  FIG. 7B , the indentation portion  473   b  of the outer side  473  may have a semicircular shape. Accordingly, the indentation portion  473   b  can have a contact line or a contact point with one of the internal wires  465 . Thus, the contact area is reduced to a minimum. Accordingly, the parasitic capacitance and the current leakage are reduced.  
         [0057]     According to an embodiment of the present invention, the cover shield  430  can be used in a direct type LCD (direct backlight assembly) or as well in an indirect type LCD (indirect backlight assembly).  
         [0058]     According to an embodiment of the present invention, a cover shield is provided with indentation portions in the outer side to decrease a contact area with the internal wires of the backlight assembly. Moreover, the cover shield includes non-contact portions that are separated from the internal wires, thereby reducing parasitic capacitance and current leakage. Thus, the originally supplied lamp inrush current is maintained, and the luminance variation in the lamps is minimized. The backlight assembly of the present invention can emit a stable light and raise the efficiency of the inverter. No insulating papers or other related appliances are required in the LCD module of the present invention. Thus, the production cost can be reduced.  
         [0059]     It will be apparent to those skilled in the art that various modifications and variations cab be made in the inverter cover shield for liquid crystal display module of the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.