Abstract:
Disclosed is a liquid crystal display (LCD) device in which low power LEDs with a dual lens structure re configured for application in a backlight device to increase the optical efficiency at low power, thus enhancing the brightness, such LCD device including: a lower cover; PCBs (Printed Circuit Boards) disposed on the lower cover for receiving power from the exterior; a main body mounted on the PCBs; R, G and B LED (Light Emitting Diode) devices disposed on the main body for emitting light; a first lens having a first curvature and mounted on the main body and housing the R, G and B LED devices; a second lens covering the outside of the first lens and having an inner curved surface with a second curvature having a varying radius of curvature, and an outer curved surface with a third curvature, wherein the second curvature of the inner curved surface is gradually increased from an edge portion toward a central portion; and a liquid crystal panel spaced apart from the second lens by a certain interval and to which light is provided.

Description:
The present disclosure relates to subject matter contained in priority Korean Application No. 10-2007-0045191, filed on May 9, 2007, which is herein expressly incorporated by reference in its entirety. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a light emitting diode (LED) package having a dual lens structure and a liquid crystal display (LCD) device implementing the same, and particularly, to an LCD device in which an array of low power LEDs having a compound dual lens structure are configured for advantageous application in a backlight module of low power so as to increase the optical efficiency and enhance the brightness. 
     2. Discussion of the Related Art 
     In general, a direct-type backlight used for a large size liquid crystal display model is configured to reflect light emitted from cold cathode fluorescent lamps on a reflecting plate to provide illumination to a liquid crystal panel disposed at a front surface thereof. Here, a diffusing sheet is additionally disposed in a light reflection path such that light can be locally emitted with a uniform luminance onto the LCD panel. However, such type of backlight becomes thicker, which causes the LCD device to become more complicated and bulky in its configuration and to become larger in its size. 
     Recently, as a surface light source which emits light only when current passes therethrough, a light emitting diode (LED) having characteristics such as a rapid response speed, low power consumption, a semi-permanent lifespan and the like, is utilized to thusly implement a thinner backlight and simultaneously enhance the brightness thereof. Above all, as compared with the existing cold cathode fluorescent lamps, the LED can present more natural colors and images with higher quality. Also, the LED can solve the problem of after-image for moving images and can be recognized as an environment-friendly product not using mercury. As a result, it can be employed as a core component of a next generation LCD so as to replace the cold cathode fluorescent lamp. 
     Hereinafter, a direct-type LED backlight of an LCD device according to the related art will be briefly described with reference to the accompanying drawings. 
       FIG. 1  is a cross-sectional view of an LCD device having a direct-type LED backlight device, and  FIG. 2  is a plan view showing a plurality of PCBs (Printed Circuit Boards) fixedly arranged onto a lower cover of the LCD device in  FIG. 1 . 
     In the LCD device as shown in  FIG. 1 , a backlight unit is provided on a lower cover  30  disposed at a lower side of a main support frame  50  formed of molded resin or stainless steel (SUS STEEL) to have a square shape, and a liquid crystal panel  10  is stacked above the main support frame  50 . An upper cover  60  encloses the edges of a front surface of the liquid crystal panel  10  and is assembled with the main support frame  50  and the lower cover  30 . 
     The liquid crystal panel  10  includes a thin film transistor array on a substrate and a color filter substrate bonded together, and liquid crystal interposed therebetween. 
     As shown in  FIGS. 1 and 2 , the backlight unit for applying light onto the liquid crystal panel  10  includes an LED array  36  configured such that red, green and blue color (R, G and B) LED packages each of which includes a cluster of R, G and B LED chips for emitting light are linearly arranged along respective ones of a plurality of PCBs (Printed Circuit Boards)  34  disposed on the lower cover  30 . A reflecting plate  32  is disposed on the entire lower surface at a region, in which the PCBs  34  are driven, for reflecting light. A diffusing plate  42  is disposed above the LED arrays  36  for diffusing light emitted from the LED arrays  36 , and a prism sheet  44  is used in order to increase the luminous intensity of the light by refracting the light diffused by the diffusing plate  42 . And a protection sheet  46  is disposed for protecting the prism sheet  44 . 
     As such, the light emitted from the R, G and B LED chips composing each cluster is mixed together so as to generate white light. The white light is emitted to the outside of each cluster. Such emitted light is usually converged on a central portion of each cluster according to the emission characteristics related to the LED chip fabrication and the like. 
     However, such an arrangement in the related art backlight unit results in dimness and non-uniformity in the overall brightness of the backlight unit, and consequently a great number of such LEDs must be employed in order to obtain sufficient illumination, increasing the cost, power consumption and heat. 
     SUMMARY OF THE INVENTION 
     Therefore, in order to solve the above-mentioned problems of the related art, it is an object of the present invention is to provide an LED (Light Emitting Diode) package with a dual lens structure so as for light emitted from the LED package to be efficiently diffused more widely, and to provide a backlight unit for an LCD (Liquid Crystal Display) device implementing such LED package as a backlight device. 
     To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, there is provided an LCD device including: a lower cover; PCBs (Printed Circuit Boards) to which external power is applied; a main body mounted on the PCBs; R, G and B LED devices disposed on the main body for emitting light; a first lens formed on the main body with a first curvature for housing the R, G and B LED devices; a second lens covering the outside of the first lens and having an inner curved surface having a varying radius of curvature, wherein the inner curved surface has a second curvature which is gradually increased from an edge portion thereof to a central portion thereof and its outer curved surface has a third curvature; and a liquid crystal panel disposed to be spaced apart from the second lens by a certain interval for receiving light applied thereto. 
     In one embodiment of the present invention, there is provided an LED package including: a main body having a recess in a central area thereof; R, G and B LED devices disposed on the main body for emitting light; a first lens disposed on the main body with a first curvature and housing the R, G and B LED devices; and a second lens covering the outside of the first lens and having an inner curved surface having a varying radius of curvature, wherein the inner curved surface has a second curvature which is gradually increased from its edge portion toward its central portion and its outer curved surface has a third curvature different from the second curvature of the inner curved surface. 
     The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are included to provide a further understanding 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. 
       In the drawings: 
         FIG. 1  is a cross-sectional view showing an LCD device having a direct-type LED backlight according to the related art; 
         FIG. 2  is a plan view showing a plurality of PCBs fixedly arranged onto a lower cover of the LCD device in  FIG. 1 ; 
         FIG. 3  is a cross-sectional view showing an LCD device having a direct-type LED backlight in accordance with a first embodiment of the present invention; 
         FIG. 4  is an enlarged perspective view of an LED package in the backlight of the LCD device of  FIG. 3 ; 
         FIG. 5  is a ray diagram view showing a state where light is emitted within the LED package of  FIG. 4 ; 
         FIG. 6  is a ray diagram view showing a state where light is refracted at an outer curved surface of a ray diagram first lens and at an inner curved surface of a second lens shown in  FIG. 5 ; 
         FIGS. 7A and 7B  are views, respectively, showing steps of process of fabricating a PCB having an LED package disposed thereon in accordance with one embodiment of the present invention; 
         FIGS. 8A ,  8 B and  8 C are views, respectively, showing steps of a process of fabricating a PCB having an LCD package disposed thereon in accordance with another embodiment of the present invention; and 
         FIG. 9  is a cross-sectional view showing an LED package in accordance with a second embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Description will now be given in detail of an LED package having a dual lens structure and an LCD device having a backlight unit implementing the same according to the present invention, with reference to the accompanying drawings. 
       FIG. 3  is a cross-sectional view showing the configuration of an LCD device adopting a direct type LED backlight unit according to the present invention. 
     As shown in  FIG. 3 , a direct type LED backlight device for applying light toward a liquid crystal panel  110  is coupled onto a lower cover  130 , and one or more first reflecting sheets or plates  131  are disposed on the lower cover  130  below or at least in between arrayed rows of LEDs composing the backlighting source. 
     In general, the reflecting sheet is formed of a white polyester film or a film having a metal (Ag, Al, etc.) coated thereon. Here, the optical reflectivity of visible rays on the reflecting sheet is about 90˜97%. As the coated film becomes thicker, the reflectivity is increased. 
     On the lower cover  130  having the first reflecting plate  131  bonded thereto are uniformly arranged a plurality of metallized or metallic substrates  132 , such as poly-based PCBs (Printed Circuit Boards) which are formed of, e.g., polyethylene or aluminum. 
     A second reflecting sheet  138  is disposed on the metallic substrates  132 . 
     A plurality of LED chips  210  for each respectively emitting red, green and blue (R, G and B) light when an external voltage is supplied thereto are disposed on the metallic substrates  132 . Here, triplets consisting of R, G and B LEDs each implements one cluster. Such a cluster is composed of a grouping of the R, G and B LEDs. Accordingly, the light emitted from each of the R, G and B LEDs is mixed together so as to compose white light. In other words, each RGB cluster serves as one light emitter which emits white light by the color combination (mixture) of the R, G and B light within the cluster. 
     Each RGB cluster is arranged within a dual lens (i.e., comprising lenses  231  and  233 ) to configure an LED package  134 . As such, white light is emitted via the dual lens (i.e.,  231  and  233 ) and diffused so as to be widely emitted, thereby exiting out of the dual lens (i.e.,  231  and  233 ). 
     Here, in the present invention, on each of the metallic substrates  132  are disposed a plurality of LED packages  134  each having the R, G and B LEDs configured as one cluster. The number of LED packages each having the R, G and B LEDs configured as one cluster depends on the size of the liquid crystal panel to which the backlight will be mounted. 
     On each of the plurality of metallic substrates  132  on which the LED packages are disposed are stacked a diffusing plate  141  and a diffusing sheet  142  each spaced apart from the metallic substrates  132  with a certain interval so as to diffuse the light emitted from the RGB clusters of the LED packages  143 , thereby generating more uniform light. Also, a prism sheet  144  for improving the directed brightness of the light transmitted through the diffusing plate  141  and the diffusing sheet  142  and a protection sheet  146  for protecting the prism sheet  144  are sequentially laminated. Here, the optical sheets such as the diffusing plate  141 , the diffusing sheet  142 , the prism sheet  144  and the protection sheet  146  may be optionally added or omitted in order to obtain desired optical characteristics. 
     The backlight device having such a configuration is coupled by a main support  150  coupled thereto at its upper side. The main support  150  maintains an overall balance of the LCD device so as to protect the LCD device from an external force or the like. The main support  150  is formed of molded resin or stainless steel so as to have a rectilinear frame. The upper surface of the main support  150  may be formed to have a stepped periphery in order to facilitate joining the liquid crystal panel  110  thereon. 
     On the main support  150  is laminated the liquid crystal panel  110  for representing data information by selectively passing the light emitted from the backlight. The liquid crystal panel  110  includes a pair of opposed transparent substrates with thin film transistors as switching devices arranged at each unit pixel or sub-pixel of a pixel matrix, a color filter, and liquid crystal interposed between the two substrates. 
     An upper cover houses the four edges of the liquid crystal panel  110 , and is coupled both to the main support  150  and to the lower cover  130 . 
     As described above, a backlight implementing the LED packages in accordance with the present invention with the dual lens structure in which the clusters each of the plurality of LEDs are configured emit light to illuminate the liquid crystal panel  110 , such that images can be displayed by the liquid crystal panel  110 . Such a RGB LED cluster will now be described in detail with reference to  FIGS. 4 and 5 . 
       FIG. 4  is an enlarged perspective view of an LED package in the backlight of  FIG. 3 ,  FIG. 5  is a view showing a state where light is emitted within the LED package of  FIG. 4 , and  FIG. 6  is a view showing a state where light is refracted at an outer curved surface of a first lens and at an inner curved surface of a second lens shown in  FIG. 5 . 
     As shown in  FIGS. 4 and 5 , the LED package  134  according to the present invention includes a main body  200  having a recess in its central area, R, G and B LED chips  210  mounted in the recess of the main body  200  to respectively emit R, G and B light, pair of conducting terminals or leads  221  and  222  respectively connected to each of the R, G and B LED chips  210  to supply power to the LED chips  210 , a first lens  231  having a first curvature and housing the LED chips  210 , and a second lens  233  disposed at the outside of the first lens  231  so as to house the first lens  231  and being a concavo-convexo or negative meniscus type lens having a thickness which is thicker at its central portion than at its edge portion. 
     The main body  200  is formed molding with the recess in its central area such that the plurality of LED chips  210  can be mounted therein. The main body  200  is molded by using a translucent resin or a resin with high reflectivity. 
     The main body  200  is provided with the external conducting terminals or leads  221  for electrically connecting the LED chips  210  therein to the outside. Here, in case where the R, G and B LED chips  210  are mounted at the main body  200 , the external conducting terminals  221  may be implemented as three pairs of external conducting terminals  221 , each respective pair being connected to the anode and cathode of corresponding LED chip  210 . Also, the external conducting terminals  221  may connect the recess in the main body  200  to the outside via the inside of the main body  200 , as shown in  FIG. 4 . In the alternative, the external conducting terminals  221  may be formed at an upper surface of the main body  200  to connect the recess in the main body  200  to the outside. 
     Each of the R, G and B LED chips  210  is mounted in the recess of the main body  200  and accordingly the R, G and B light emitted therefrom is mixed together so as to generate white light. Here, the R, G and B LED chips  210  may be arranged in a triangular formation as shown in the drawing. Alternatively, they may be arranged in a row, i.e., linearly or in any other spatial relationship to one another. 
     The main body  200  is provided in its recess with conducting wires, i.e., lead bonding wires, namely, internal conducting terminals  222  for electrically connecting the LED chips  210  to the external conducting terminals  221 , respectively. Accordingly, an external voltage may be applied to each of the LED chips via the externally supplied conducting terminals  221  and the internal conducting terminals  222 . 
     Also, the first lens  231  having the first curvature is provided over the LED chips  210  disposed in the recess of the main body  200 . Here, a gel-type elastic resin made of silicone is filled in the first lens  231 . The LED chips  210  are accordingly sealed, i.e., encapsulated such that no voids, namely, no hollow section exists between the LED chips  210  and the first lens  231 . 
     Here, the gel-type elastic resin is hardened after being injected. Such hardened elastic resin can have good elasticity such that it can protect the LED chips  210  more stably from thermal stress, vibration, external impact and the like. In addition, the hardened elastic resin exhibits minimal change from single wavelength light, such as yellowing, while having high refractivity, thus exhibiting excellent optical characteristics. 
     Moreover, the first lens  231  may be designed, for example, in a spherical shape so as to decrease light which is emitted from the R, G and B LED chips  210  toward a side surface and then totally reflected in the first lens  231 . Such design is employed for two purposes. For one purpose, the amount of light totally reflected in the first lens  231  is adjusted to control the mixing of the light emitted from the R, G and B LED chips  210 , thereby creating white light. As for the other purpose, since the power consumption of the R, G and B LED chips  210  may differ depending on their types or the characteristics of the LED chips  210  may be a bit different depending on their manufacturer, a design considering such conditions is required. 
     In addition to the silicone for the first lens  231 , a small amount of diffusing material, i.e., optical dispersant, may be additionally added to the silicone, such that the diffusing material can convert the optical path, thus increasing the optical mixing. Furthermore, a haze processing may be performed for the surface of the first lens  231  containing the silicone and the diffusing material, to maximize the optical mixing. 
     Still referring to  FIGS. 4 and 5 , the second lens  233  having an oval concave inner curved surface and a hemispherical convex outer curved surface is formed peripherally of and above the first lens  231 . The second lens  233  is accordingly thin at its central portion and thicker toward its edge. 
     As such, as the second lens  233  is formed and attached to be spaced apart from the first lens  231  with a certain interval such that an empty space, i.e., a hollow section, exist between the second lens  233  and the first lens  231 . Here, the first lens  231  and the second lens  233  have a differing interval therebetween. That is, the interval between the first and second lenses  231  and  233  at their central portions is greater than that at their edges. 
     The second lens  233  may be formed of any one of polycarbonate, polyethylene, EMC (Epoxy Molding Compound), silicone, epoxy resin or the like, or formed by combining two or more of such compounds by an injection molding. 
     In the present invention, the second lens  233  is preferably configured such that a second curvature, i.e., radius of curvature of its inner concave curved surface decreases from its central portion toward its edge, and a third curvature of its convex outer curved surface is smaller than the first convex curvature of the first lens  231 . 
     Here, upon sweeping declinedly along the curved surface at a uniform angular rate from a certain point (optical point) at the central portion of the inner curved surface, the radius of curvature of the inner curved surface of the second lens  233  changes according to the angular declination, i.e., according to the arcuate length of the curved surface. At this moment, the radius of curvature is much shorter than the radius of curvature of the circle drawn upon sweeping inclinedly at a uniform angular rate along the curved surface from the edge portion of the second lens  233 . In other words, the second curvature of the second lens  233  is greater at the central portion of its inner curved surface than at the edge portion of the inner curved surface. 
     Therefore, in the present invention, the second curvature of the inner curved surface of the second lens  233  is gradually decreased from the central portion toward the edge, which means that since the oval shape of the inner curved surface of the second lens  233  is implemented by arcs of circles having the above mentioned radii of curvature, the radius of curvature is the shortest at the convex part of the central portion while the radius of curvature is the greatest at the edge, and the radius of curvature is gradually increased in the intermediate area from the central portion toward the edge. 
     With such principle, the outer curvature surface of the second lens  233  has a greater radius of curvature than has the outer curved surface of the first lens  231 . Accordingly, the third curvature of the outer curved surface of the second lens  233  is smaller than the first curvature of the first lens  231 . 
     The structures of the first lens  231  and the second lens  233  will now be described in more detail with reference to  FIG. 5 . 
     Assuming that the central points (i.e., optical axes) of the first and second lenses  231  and  233  are perpendicular to the emitting faces of LED chips  210  on the main body  210 , an area within a particular inclination angle range of about 30° from the upper planar surface of the main body  210  in a direction inclining toward the central points of the first and second lenses  231  and  233  is represented as Region A, an area within an inclination angle range of 30°˜60° is represented as Region B, and an area within an inclination angle of 60°˜90° is represented as Region C. 
     Here, in Region A, the interval between the first lens  231  and the second lens  233  is uniform within the overall area corresponding to Region A, while the interval is the narrowest as compared with the intervals therebetween in Region B and Region C. On the other hand, the second lens  233  is the thickest in Region A. 
     In Region B, the interval between the first lens  231  and the second lens  233  is uniform in the overall area corresponding to Region B, while the interval is greater than that in Region A but narrower than that in Region C. On the other hand, the thickness of the second lens  233  in Region B is thinner than that in Region A and thicker than that in Region C. 
     In Region C, the interval between the first lens  231  and the second lens  233  is uniform in the overall area corresponding to Region C, while the interval is the greatest as compared with the intervals in Region A and Region B. On the other hand, the second lens  233  is the thinnest in Region C. 
     Although the description above was given for the three regions divided for the sake of convenience, the interval between the first lens  231  and the second lens  233  is gradually increased linearly or non-linearly approximately from their edge portions toward their central portions. On the other hand, the thickness of the second lens  233  is gradually decreased linearly or non-linearly from its edge portion toward its central portion. 
     Here, the distance corresponding to the sum of the hollow section between the first lens  231  and the second lens  233  and the thickness of the second lens  233  is uniform in all of Regions A, B and C, which means that the distance from the outer curved surface of the first lens  231  to the outer curved surface of the second lens  233  is identical in all the regions. 
     The operation of the backlight device implementing the dual lens multicolor LED package according to the present invention will now be described based upon the difference in light refractivity (i.e., index of refraction “n”) in each Region of the first lens  231  and the second lens  233  with reference to  FIGS. 5 and 6 . 
     As shown in  FIG. 5 , light is emitted from the R, G and B LED chips  210  with its optical path being changed by the diffusing material mixed in with the silicone in the first lens  231 , thus to be mixed together. 
     Such mixed light is transmitted through the first lens  231  and the second lens  233  so as to be refracted commonly three times areas along its entire path. The first refraction occurs when light having been emitted from the LED chips  210  is incident on the hollow section via the first lens  231 , the second refraction occurs when the light is incident on the inner curved surface of the second lens  233  via the hollow section, and the third refraction occurs when the light transmitted through the second lens  233  exits into the air from the outer curved surface of the second lens  233 . 
     Generally, the light path depends on the refractivity. The present invention is implemented such that the refractivity n 1  of the first lens  231 , the air refractivity n 2  in the hollow section, a refractivity n 3  of the second lens  233  and the exterior air refractivity n 4  outside of the second lens  233  are all the same in Regions A, B and C. Accordingly, the light path in Regions A, B and C are determined according to the curvature and thickness of the second lens  233 , namely, the refractivity of the second lens  233 . 
     As shown in  FIGS. 5 and 6 , a first emitted light ray L 1  emitted in Region A from the LED chip  210  is incident on the hollow section from the outer curved surface of the first lens  231  so as to be refracted by a particular angle due to the difference between the refractivity n 1  of the first lens  231  and the refractivity n 2  of the air in the hollow section. The refracted first emitted light ray L 1  is then incident on the inner curved surface of the second lens  233  via the short hollow section. 
     Here, because the incident first emitted light ray L 1  is incident directly on (i.e., normal to the inner surface of) the second lens  233  there is no change in the light path at the inner curved surface of the second lens  233 . Accordingly, the first emitted light ray L 1  exits out of the second lens  233 , hardly changing its path. 
     Description will be given in more detail with reference to the following Equation 1.
 
 n 2×sin(θ1)= n 3×sin(θ1′)  [Equation 1]
 
     where n 2  denotes the refractive index of the air in the hollow section, θ 1  denotes the incident angle of the light on the inner curved surface of the second lens  233 , n 3  denotes the refractive index of the second lens  233 , and θ 1 ′ denotes the emission angle. 
     Here, since the refractive index n 2  of the air in the hollow section is lower than the refractive index n 3  of the second lens  233 , the emission angle θ 1 ′ is always smaller than the incident angle θ 1 . 
     As shown in  FIG. 6 , if a tangent line and a normal line perpendicular to the tangent line are drawn at a certain point on the inner curved surface of the second lens  233  at which the first emitted light ray L 1  is incident in Region A, the incident angle θ 1  formed between the first emitted light ray L 1  and the normal line is considerably small, and accordingly, the emission angle θ 1 ′ is much smaller. 
     Also, the first emitted light ray L 1  refracted by the inner curved surface of the second lens  233  is then incident on the outer curved surface of the second lens  233 . As a result, the first emitted light ray L 1  exits to the side surface with a bit wider radiation width (as compared with the related art) according to the difference between the refractivity of the outer curved surface and the surrounding air refractivity. 
     In relation to this, the following Equation 2 applies.
 
 n 3×sin(θ1′)= n 4×sin(θ1″)  [Equation 2]
 
     where n 3  denotes the refractive index of the second lens, θ 1 ′ denotes the incident angle at the outer curved surface of the second lens  233 , n 4  denotes the refractive index of air surrounding the second lens, and θ 1 ″ denotes the emission angle. 
     Here, since the refractivity n 3  of the second lens  233  is higher than the refractivity of the outside air, the emission angle θ 1 ″ should always be greater than the incident angle θ 1 ′. 
     However, although not shown in detail in  FIG. 6 , if a tangent line and a normal line perpendicular to the tangent line are drawn at a certain point on the outer curved surface of the second lens  233  at which the first emitted light ray L 1  is actually incident in Region A, the incident angle θ 1 ′ formed between the first emitted light ray L 1  and the normal line is not so great, and accordingly, the emission angle θ 1 ″ is not increased so much, either. 
     Thus, the incident angle θ 1 ′ of the first emitted light ray L 1  on the outer curved surface of the second lens  233  in Area A is determined by the incident angle θ 1  of the first emitted light ray L 1  on the inner curved surface of the second lens  233 . Also, as the incident angle θ 1  of the first emitted light ray L 1  on the inner curved surface of the second lens  233  is smaller, the incident angle θ 1 ′ of the first emitted light ray L 1  on the outer curved surface of the second lens  233  also becomes smaller. 
     As a result, most of actual refraction occurring in Region A is induced by the refractivity difference between the outer curved surface of the second lens  233  and the outer air. 
     Regarding Region B, if it is considered that a second light ray L 2  emitted from the LED chip  210  is incident perpendicularly on a tangent line formed by the outer curved surface of the first lens  231   a  and a certain point on which the second emitted light ray L 2  is incident at the outer curved surface of the first lens  231 , the second emitted light ray L 2  in Region B is incident on the hollow section from the outer curved surface of the first lens  231  and accordingly the refraction occurs in Region B to the same degree as in Region A. 
     The refracted second emitted light ray L 2  is incident on the inner curved surface of the second lens  233  from the hollow section by the relatively great hollow section as compared with that in Region A and the curvature of the second lens  233 , such that the light path of the second emitted light ray L 2  is changed greatly as compared with the first emitted light ray L 1  in Region A. This will be understood from the aforesaid Equation 1. 
     Thus, light exits through the side surface due to the refractivity difference between the outer curved surface of the second lens  233  and the surrounding air, as can be understood from the aforesaid description. 
     Therefore, the second emitted light ray L 2  in Region B is incident on the inner curved surface of the second lens  233  from the hollow section such that the path of the second light ray L 2  is changed more than that of the first light ray L 1  in Region A. This is because the radius of curvature of the inner curved surface of the second lens  233  in Region B is not shorter than the radius of curvature of the inner curved surface of the second lens  233  in Region A. In other words, the second curvature of the inner curved surface of the second lens  233  in Region B is greater than the second curvature of the inner curved surface of the second lens  23  in Region A. 
     Regarding in Region C, if it is considered that a third emitted light ray L 3  from the LED chip  210  is incident perpendicularly on a tangent line formed at the outer curved surface of the first lens  231  and a certain point at which the third emitted light ray L 3  is incident at the outer curved surface of the first lens  231 , the third emitted light ray L 3  in Region C is incident on the hollow section from the outer curved surface of the first lens  231  so as to be refracted to the same degree as in Regions A and B. 
     The refracted third emitted light ray L 3  is incident on the inner curved surface of the second lens  233  from the hollow section such that its path is changed more than those of the first emitted light ray L 1  in Region A and the second emitted light ray L 2  in Region B, which results from that the third emitted light ray L 3  in Region C depends on the relatively long hollow section and the second curvature of the second lens  233  as compared with Region A and Region B. This will be apparent from the aforesaid Equation 1. 
     The third emitted light ray L 3  then exits through the side surface due to the refractivity difference between the outer curved surface of the second lens  233  and the surrounding air, as can be understood from the aforesaid description. 
     Thus, the third emitted light ray L 3  in Region C in which the inner curved surface of the second lens  233  has a radius of curvature smaller than those in Region A and Region B, namely, as the second curvature becomes greater. Accordingly, the light path is changed much more at the inner curved surface, which results in a reduction of the light intensity at the central portion of the second lens  233 . 
     Consequently, the light emitted from the R, G and B LED chips  210  into Region B and Region C is diffused even into Area A via the first and second lenses  231  and  233 . Ultimately, the light passing through the second lens  233  can have the characteristic of being emitted over an angle of approximately 30° to 90° with respect to the planar surface of the main body  200  (i.e., from the horizontal). 
     A method of fabricating the LED package having such structure will be described with reference to  FIGS. 7A and 7B . 
     First, as shown in  FIG. 7A , the R, G and B LED chips  210  are mounted in the recess of the main body  200 . A gel-type elastic resin is injected into the recess to be hardened, thereby forming the first lens  231 . 
     The second lens  233  which is separately fabricated by an injection molding is fixed onto the main body  200 . Here, the main body  200  and the second lens  233  are fixed to each other by coupling means such as a hole and a hook or by an adhesive member. 
     Such thusly formed LED package is fixed onto a metallic substrate  250  made of aluminum or onto a poly-based PCB, as shown in  FIG. 7B , so as to be supplied a voltage from the exterior, for thus emitting light. 
     Also, an LED package according to the present invention may be fabricated by processes as shown in  FIGS. 8A to 8C . 
     First, R, G and B LED chips  310  are mounted in a recess of a main body  300  having a square shape as shown in  FIG. 8A . A gel-type elastic resin is injected into the recess to be hardened, thereby forming a first lens  331 . 
     As shown in  FIG. 8B , the main body  300  having the first lens  331  thereon is coupled onto a metallic substrate  350  or a poly-based PCB. 
     Afterwards, as shown in  FIG. 8C , a second lens  333  separately fabricated by an injection molding is fixed onto the metallic substrate  350 . Here, the second lens  333  and the metallic substrate  350  are coupled to each other by separate coupling means such as a hole in the metallic substrate  350  and a hook on the second lens  333 . 
     With this configuration, the LED chips  310  can emit light when an external voltage is applied to the metallic substrate  350 . 
       FIG. 9  is a cross-sectional view showing an LED package of an LCD device in accordance with a second embodiment of the present invention. 
     As compared with  FIGS. 4 and 5 , the LED package according to the second embodiment of the present invention includes a main body  400  implementing a periphery with a recess in its central portion, R, G and B LED chips  410  mounted in the recess in the main body  400 , respective conducting terminals  421  and  422  connected to the R, G and B LED chips  410  to apply voltages thereto, a first lens  431  formed on the LED chips  410  and having a first curvature which is gradually increased from its edge portion toward its central portion, and a second lens  433  formed at the edge and the central portion of the first lens  431  wherein its inner curved surface has a second curvature which is gradually increased from the edge portion toward the central portion and its outer curved surface has a third curvature which is gradually decreased from the edge portion toward the central portion. 
     Here, when the first lens  431  having the first curvature which is gradually increased from the edge portion toward the central portion is the same as that of the second lens  433 , which is formed at the edge and the central portion of the first lens  431  and has the inner curved surface with the second curvature which is gradually increased from the edge portion toward the central portion, the first lens  431  contacts the second lens  433 . 
     Here, the first lens  431 , which is formed of a gel-type elastic resin to be spherical and the second lens  433  formed by an injection molding to be spherical are respectively formed of a material which can vary both the second curvature and their refractivities at the portion where the first lens  431  and the second lens  433  come in contact with each other. Accordingly, the same effect as aforementioned can be expected. 
     Other details can be understood from the aforementioned description. 
     Now, although not shown in any additional drawing, an LED package of a backlight for an LCD device which is a variation of the first embodiment of the present invention will be described. 
     As compared with  FIGS. 4 and 5 , the LED package of the backlight for the LCD device according to the present invention includes a main body implementing a periphery with a recess in its central area, R, G and B LED chips mounted in the recess in the main body, conducting terminals connected to the R, G and B LED chips to apply voltages thereto, a first lens formed on the LED chips and having a first curvature, and a second lens formed at the edge and the central portion of the first lens, wherein its inner curved surface has a second curvature which is gradually increased from the edge portion toward the central portion and its outer curved surface has a third curvature which is gradually decreased from the edge portion toward the central portion. 
     That is, the third curvature of the outer curved surface of the second lens formed above the first lens is formed to be opposite to the second curvature of the inner curved surface of the second lens. 
     Other details can be understood from the aforementioned description. 
     Also, although an LED backlight for an LCD device which is implemented by modifying the first embodiment of the present invention is not shown in any separate drawing, it can be implemented in any of the following cases. 
     For example, when a poly-based PCB is arranged on a lower cover, at least one LED device may be separately disposed on the PCB, instead of the type of LED package having the LED chips therein. Here, a first lens formed on the LED device may be separately formed by an injection molding, instead of being formed of a gel-type elastic resin such as silicone. 
     Here, the first lens may be formed to have a certain uniform thickness such that a curvature of its inner curved surface is greater than the curvature of its outer curved surface. In the alternative, the first lens may be formed to have an outer curved surface with a certain curvature and an inner curved surface with a curvature which is gradually decreased from the central portion toward the edge portion such that the first lens is thicker from its central portion toward its edge portion. 
     Consequently, the inner curved surface and the outer curved surface of the first lens may be formed in hemispherical shapes, or the outer curved surface of the first lens may be hemispherical while the inner curved surface thereof may be oval. 
     After forming such thusly configured first lens on the LED device fixed onto the PCB, the second lens may be configured in the same manner as the first lens. 
     Accordingly, the outer curved surface of the second lens may also be hemispherical while its inner curved surface may be oval. 
     In one example, in accordance with the present invention, on the PCB having at least one LED device fixed thereonto is configured the first lens having the outer curved surface with the particular first curvature and the inner curved surface with the curvature which is gradually decreased from the central portion toward the edge. Afterwards, over the first lens is configured the second lens having an outer curved surface with the curvature which is smaller than the first curvature of the outer curved surface of the first lens and having an inner curved surface with a curvature which is gradually decreased from its central portion toward its edge. 
     Any appropriate combination of the aforesaid methods can implement the LED package and the backlight for an LCD device. The scope of the present invention is therefore intended to be embraced by the appended claims. 
     As described above, the LED package for a backlight for an LCD device according to the present invention can support light which is emitted more widely from the LED package which serves as a light source, so as to enable the enhancement of the overall color mixing and uniformity of the brightness.