Patent Publication Number: US-11029562-B2

Title: Backlight unit and liquid crystal display device including the same

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     The present application claims priority from and the benefit under 35 U.S.C § 119(a) of Korean Patent Application No. 10-2017-0144067 filed on Oct. 31, 2017, which is hereby incorporated by reference in its entirety. 
     BACKGROUND 
     Technical Field 
     The present disclosure relates to a backlight unit and a liquid crystal display device including the same. 
     Description of the Related Art 
     With rapid development of information technologies, display devices for displaying a large amount of information have been promptly developed. Recently, flat panel display devices having a thin profile, light weight and low power consumption, such as liquid crystal display devices or electroluminescent display devices, have been suggested and widely applied. 
     Among the flat panel display devices, liquid crystal display devices have been widely used due to their small sizes, light weights, thin thicknesses, and low power consumption. A liquid crystal display device includes a liquid crystal panel displaying an image and a backlight unit disposed under the liquid crystal panel to providing light to the liquid crystal panel. 
     Backlight units are classified into an edge-type and a direct-type according to a method of arranging a light source. 
     In an edge-type backlight unit, a light source is disposed on a side surface of a light guide plate disposed below a light crystal panel, and light emitted from the light source is converted into surface light through the light guide plate and provided to the liquid crystal panel. However, in the edge-type backlight unit, since the light source is on the side, there is a restriction in implementing a local dimming method in which the backlight unit is divided into a plurality of regions and driven for each region. 
     Meanwhile, in a direct-type backlight unit, a plurality of light sources are disposed under a liquid crystal display panel, and light emitted from the light sources is directly provided to an entire surface of the liquid crystal panel. In the direct-type backlight unit, uniformity and brightness of light provided to the liquid crystal panel can be improved, and the local dimming method can be implemented, so that a contrast ratio can be improved and power consumption can be reduced. 
     However, in the direct-type backlight unit, since the light sources are disposed under the liquid crystal display panel and light is directly provided to the liquid crystal panel, a mura such as a hot spot may occur over the light sources, and image quality may be decreased. 
     BRIEF SUMMARY 
     Accordingly, the present disclosure is directed to a backlight unit and a liquid crystal display device including the same that substantially obviate one or more of the problems due to limitations and disadvantages of the related art. 
     An object of the present disclosure is to provide a backlight unit and a liquid crystal display device including the same that prevent the mura such as the hot spot and the decrease of the image quality. 
     Another object of the present disclosure is to provide a backlight unit and a liquid crystal display device including the same that reduce the thickness of the backlight unit and realize a thin profile. 
     Additional features and advantages of the present disclosure will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the present disclosure. The objectives and other advantages of the present disclosure will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings. 
     To achieve these and other advantages and in accordance with the purpose of the present disclosure, as embodied and broadly described herein, there is provided a backlight unit includes a circuit board; a plurality of LED packages mounted on the circuit board; an encapsulation member over the circuit board and covering the plurality of LED packages; and a multi-pattern sheet over the encapsulation member and including a glass complex body containing a phosphor and a plurality of diffusion patterns on an upper surface of the glass complex body, wherein the plurality of diffusion patterns include at least one first pattern corresponding to each LED package and at least one second pattern corresponding to a portion between adjacent LED packages. 
     In another aspect, a backlight unit includes a circuit board; a plurality of LED packages mounted on the circuit board; an encapsulation member over the circuit board and covering the plurality of LED packages; and a multi-pattern sheet over the encapsulation member and including a glass complex body containing a phosphor, a plurality of diffusion patterns on an upper surface of the glass complex body, and a plurality of reflective patterns on a lower surface of the glass complex body, wherein the plurality of diffusion patterns include at least one first pattern corresponding to each LED package and at least one second pattern corresponding to a portion between adjacent LED packages, and wherein each LED package, each reflective pattern and the at least one first pattern overlap each other in a vertical direction transverse to an upper surface of the LED packages. 
     In another aspect, a liquid crystal display device comprises a liquid crystal panel and a backlight unit under the liquid crystal panel and including a circuit board; a plurality of LED packages mounted on the circuit board; an encapsulation member over the circuit board and covering the plurality of LED packages; and a multi-pattern sheet over the encapsulation member and including a glass complex body containing a phosphor and a plurality of diffusion patterns on an upper surface of the glass complex body, wherein the plurality of diffusion patterns include at least one first pattern corresponding to each LED package and at least one second pattern corresponding to a portion between adjacent LED packages. 
     It is to be understood that both the foregoing general description and the following detailed description are by example and explanatory and are intended to provide further explanation of the present disclosure as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       The accompanying drawings, which are included to provide a further understanding of the present disclosure and which are incorporated in and constitute a part of this specification, illustrate an embodiment of the present disclosure and together with the description serve to explain the principles of the present disclosure. In the drawings: 
         FIG. 1  is a schematic exploded perspective view of a liquid crystal display device according to a first embodiment of the present disclosure; 
         FIG. 2  is a schematic cross-sectional view of a backlight unit according to the first embodiment of the present disclosure; 
         FIGS. 3A to 3C  are schematic cross-sectional views of LED packages according to an embodiment of the present disclosure; 
         FIG. 4  is a schematic cross-sectional view of a backlight unit according to a second embodiment of the present disclosure; 
         FIG. 5  is a cross-sectional view schematically showing a path of light in a backlight unit according to the second embodiment of the present disclosure; 
         FIG. 6A  is a schematic cross-sectional view of a reflective pattern according to an embodiment of the present disclosure, and  FIGS. 6B and 6C  are schematic plan views of the reflective pattern according to the embodiment of the present disclosure; 
         FIG. 7  is a schematic cross-sectional view of a multi-pattern sheet including a depressed diffusion pattern according to the second embodiment of the present disclosure; 
         FIGS. 8A to 8D  are views schematically showing shapes of the diffusion pattern according to the second embodiment of the present disclosure; 
         FIG. 9  is a view showing light distribution of a liquid crystal display device according to the first embodiment of the present disclosure; 
         FIG. 10  is a view showing light distribution of a liquid crystal display device according to the second embodiment of the present disclosure; and 
         FIG. 11  is a schematic cross-sectional view of a backlight unit according to a third embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to exemplary embodiments of the disclosure, examples of which are illustrated in the accompanying drawings. 
       FIG. 1  is a schematic exploded perspective view of a liquid crystal display device according to a first embodiment of the present disclosure, and  FIG. 2  is a schematic cross-sectional view of a backlight unit according to the first embodiment of the present disclosure. 
     In  FIG. 1  and  FIG. 2 , the liquid crystal display device  10  according to the first embodiment of the present disclosure includes a backlight unit  200 , a liquid crystal panel  300 , a panel driving circuit  310 , and a bottom cover (or lower cover)  100 . 
     The bottom cover  100  is disposed below the backlight unit  200  and supports the backlight unit  200 . Here, the bottom cover  100  may be considered as a component included in the backlight unit  200 . 
     The bottom cover  100  can be formed in a box shape with an open upper portion so as to receive the backlight unit  200  therein, but the present disclosure is not limited thereto. For example, the bottom cover  100  may be formed in a plate shape. 
     Meanwhile, although not shown in the figures, the liquid crystal display device  10  may further include a guide panel surrounding and supporting sides of the backlight unit  200  and the liquid crystal panel  300  and a top cover covering edges of a top surface of the liquid crystal panel  300 . 
     The backlight unit  200  according to the first embodiment of the present disclosure is a direct-type backlight unit in which a plurality of light sources, for example, light emitting diodes (LEDs) are spaced apart from each other with a predetermined distance therebetween and are disposed directly under and face the liquid crystal panel  300 . 
     The backlight unit  200  can include a circuit board  210 , a plurality of LED packages  220 , an encapsulation member  230 , a reflective pattern sheet  240 , a diffusion plate  250 , a fluorescent sheet  260 , and an optical sheet  270 . 
     The circuit board  210  is disposed on a top surface of the bottom cover  100 . The circuit board  210  can be attached to the bottom cover  100  through ah adhesive member  120  such as a double-sided adhesive. 
     The plurality of LED packages  220  are mounted on a top surface of the circuit board  210 . The top surface of the circuit board  210  can have a reflection property, for example, by forming a reflection layer on the top surface of the circuit board  210 . In this case, light traveling toward the circuit board  210  can be reflected by the circuit board  210  and travel toward the liquid crystal panel  300 . 
     The LED package  220  mounted on the circuit board  210  emits light by a driving signal supplied from a backlight driving portion (not shown). 
     The LED package  220  can have various structures. For example, the LED package  220  can have a lateral chip structure, a flip chip structure, a vertical chip structure, a chip scale package (CSP) structure, or the like. In addition, the LED package  220  can further include a reflector over an LED chip, but the present disclosure is not limited thereto. The LED package  220  will be described in detail with reference to  FIGS. 3A to 3C . 
     In  FIG. 3A , the LED package  220  of the present disclosure can have a flip chip structure. For example, the LED package  220  can have a blue flip chip structure emitting blue light, but the present disclosure is not limited thereto. In this case, the LED package  220  can have a beam angle of about 110 degrees to about 120 degrees. 
     In  FIG. 3B , the LED package  220  of the present disclosure can have a flip chip structure including a reflection member  222 . That is, the LED package  220  of the present disclosure can include an LED chip  221  and the reflection member  222  over the LED chip  221 . In this case, the reflection member  222  can be formed of a reflective material Ag or TiO 2 , but the present disclosure is not limited thereto. Alternatively, the reflection member  222  can have a structure in which two layers having different refractive indexes are alternately stacked. The LED package  220  including the reflection member  222  can have a larger beam angle than that of the LED package  220  of  FIG. 3A , and the LED package  220  including the reflection member  222  can have a beam angle of about 110 degrees to about 160 degrees. 
     In  FIG. 3C , the LED package  220  of the present disclosure can have a CSP structure. Such a LED package  220  can include an LED chip  221  and a mold  224  surrounding the LED chip  221  and can further include a reflection member  226  over the mold  224 . 
     Here, the mold  224  can be formed of a clear resin and can have a refractive index of 1.5 or more. For example, the mold  224  can have a refractive index of about 1.5 to about 1.7, but the present disclosure is not limited thereto. In addition, an overall width of the mold  224  can be about two times to about two and a half times a width of the LED chip  221 . 
     In the LED package  220  having the CSP structure, its size can be minimized, and thus a thickness of the backlight unit  200  can be reduced. Further, the LED package  220  having the CSP structure can have excellent processability and can increase light efficiency as compared with the LED package  220  of  FIG. 3B  having the flip chip structure. 
     In the case that the LED package  220  having the CSP structure is applied, the encapsulation member  230  can be omitted. 
     Meanwhile, as shown in  FIGS. 3B and 3C , when the LED package  220  includes the reflection member  222  and  226 , the reflective pattern sheet  240  can be omitted. 
     Next, the encapsulation member (or encapsulation mold)  230  can be formed over the plurality of LED packages  220  to cover an entire surface of the circuit board  210  on which the plurality of LED packages  220  are mounted. The encapsulation member  230  can be applied to the circuit board  210  to a thickness greater than that of the LED package  220  and cover all the LED packages  220  mounted on the circuit board  210 . The encapsulation member  230  can stably fix the LED packages  220  on the circuit board  210  and protect the LED packages  220  from the outside. 
     Here, the encapsulation member  230  can have a refractive index of about 1.5 to 1.7, but the present disclosure is not limited thereto. 
     The encapsulation member  230  can be formed of a resin-based material including silicone, UV resin, polycarbonate (PC) and polymethyl methacrylate (PMMA), for example, and the present disclosure is not limited thereto. 
     Then, the diffusion plate  250  is disposed over the encapsulation member  230 . The diffusion plate  250  can diffuse light emitted from the plurality of LED packages  220  and provide uniform surface light to the liquid crystal panel  300 . 
     Meanwhile, the reflective pattern sheet  240  having a film shape can be provided between the encapsulation member  230  and the diffusion plate  250 . The reflective pattern sheet  240  can include a base substrate  241  and a plurality of first reflective patterns  242  that are formed on a lower surface of the base substrate  241  and are disposed to correspond to the LED packages  220 , respectively. 
     Here, the reflective pattern  242  reflects a part of light, which is emitted upwardly from the corresponding LED package  220  located thereunder, and distributes the part of the light in a side direction. A remaining part of the light is transmitted by the reflective pattern  242  and travels upwardly. Accordingly, most of the light is prevented from traveling in a vertical upward direction and from being incident on the liquid crystal panel  300 . Therefore, it is possible to prevent a hot spot caused by light incidence in the vertical upward direction, and the deterioration of the image quality due to the hot spot can be improved. 
     The fluorescent sheet  260  can be disposed on the diffusion plate  250 . The fluorescent sheet  260  can include at least one phosphor (or fluorescent substance) absorbing a part of first color light generated in the LED package  220  and generating light of at least one color different from the first color. 
     In the case of using the fluorescent sheet  260 , the first color light generated in the LED package  220  and the light of the color generated by the fluorescent sheet  260  are mixed to finally produce white light, and the white light can be provided to the liquid crystal panel  300 . 
     For example, when the LED package  220  generates blue light as the first color light, the fluorescent sheet  260  can absorb a part of the blue light and generate yellow light as a second color light. 
     Alternatively, when the LED package  220  generates white light, the fluorescent sheet  260  can be omitted. 
     The optical sheet  270  including at least one sheet can be disposed on the fluorescent sheet  260 . The at least one sheet can be a light-concentrating sheet, for example. In the first embodiment of the present disclosure, the optical sheet  270  includes three sheets, but the present disclosure is not limited thereto. 
     The liquid crystal panel  300  is disposed over the backlight unit  200 . The liquid crystal panel  300  controls light transmittance of a liquid crystal layer and displays an image. The liquid crystal panel  300  can include a first substrate (or a lower substrate)  301 , a second substrate (or an upper substrate)  302  facing and attached to the first substrate  301 , and a liquid crystal layer (not shown) interposed between the first and second substrates  301  and  302 . On the other hand, although not shown in the figures, a first polarizer and a second polarizer can be attached to outer surfaces of the first substrate  301  and the second substrate  302 , respectively. 
     In the liquid crystal panel  300 , the liquid crystal layer can be operated for each pixel by an electric field, which is generated by a data voltage and a common voltage applied to each pixel, and thus a color image can be displayed according the light transmittance of the liquid crystal layer. 
     The panel driving portion  310  can be connected to a pad portion provided on the first substrate  301  and drive each pixel of the liquid crystal panel  300 . For example, the panel driving portion  310  can include a plurality of circuit films  311  connected to the pad portion of the liquid crystal panel  300 , a data IC  313  mounted on each circuit film  311 , a display printed circuit board  312  connected to the circuit films  311 , and a timing control circuit  314  mounted on the display printed circuit board  312 . 
     The timing control circuit  314  can sort and process digital image data input from an external driving system (not shown) to generate pixel data for respective pixels of the liquid crystal panel  300 , in response to timing synchronization signals supplied from the external driving system, and supply the pixel data to the data IC  313 . In addition, the timing control circuit  314  can generate a data control signal and a gate control signal based on the timing synchronization signals to control driving timing of each of the data IC  313  and a gate IC (not shown). 
     Further, the timing control circuit  314  can control an emission operation of the backlight unit  200  according to a local dimming method and individually control brightness of the liquid crystal panel  300  for each region. 
     As described above, in the embodiment of the present disclosure, since the backlight unit  200  is a direct-type backlight unit, the local dimming method in which the liquid crystal panel  300  is driven for each region can be realized. Thus, a contrast ratio can be improved, and power consumption can be reduced. 
     Further, since the reflective pattern sheet  240 , which includes the reflective patterns  241  corresponding to the respective LED packages  220 , is provided, light output in the vertical upward direction can be reduced, and the hot spot can be prevented, thereby improving the image quality. 
     In addition, the light can be reflected by the reflective pattern sheet  240  and travel in the side direction, and thus an optical gap of the direct-type backlight unit  200  can be reduced. Accordingly, a thickness of the backlight unit  200  can be decreased, and the liquid crystal display device  10  in a thin profile can be implemented. Moreover, a halo phenomenon in which light is output beyond a local dimming region can be prevented due to a decrease of the optical gap. 
     Second Embodiment 
       FIG. 4  is a schematic cross-sectional view of a backlight unit according to a second embodiment of the present disclosure. 
     Hereinafter, for convenience of explanation, the same reference numerals are given to the similar or same parts as those of the first embodiment, and a description thereof will be omitted or simplified. 
     In  FIG. 4 , the backlight unit  200  according to the second embodiment includes a multi-pattern sheet  290 , which is a single multi-functional sheet having functions of the reflective pattern sheet  240  of  FIG. 2 , the diffusion plate  250  of  FIG. 2  and the fluorescent sheet  260  of  FIG. 2  of the backlight unit  200  of the first embodiment. 
     The multi-pattern sheet  290  can include a glass complex body  291  as a base substrate, a plurality of reflective patterns  292  formed on a lower surface of the glass complex body  291 , which is a surface facing the LED packages  220 , and a plurality of diffusion patterns  293  on an upper surface of the glass complex body  291 , which is an opposite surface facing the optical sheet  270 . Here, the glass complex body  291  can include at least one phosphor (or fluorescent substance) therein. The phosphor can absorb a part of first color light generated in the LED package  220  and generate light of at least one color different from the first color. 
     Referring to  FIG. 5 , which shows a path of light in a multi-pattern sheet of the present disclosure, the reflective pattern  292  substantially the same as the reflective pattern  242  of the first embodiment reflects a part of light, which is emitted upwardly from the LED package  220  located thereunder, and distributes the part of the light in a side direction. A remaining part of the light is transmitted by the reflective pattern  292  and travels upwardly. 
     In addition, the diffusion pattern  293  diffuses incident light substantially the same as the diffusion plate  250  of the first embodiment. 
     In the second embodiment, since the single multi-pattern sheet  290  includes the reflective pattern  292  and the diffusion pattern  293  and performs the functions of the reflective pattern sheet  240  and the diffusion plate  250  of the first embodiment, uniform surface light is generated and output upwardly. 
     Further, the glass complex body  291  of the multi-pattern sheet  290  includes at least one phosphor therein and performs the function of the fluorescent sheet  260  of the first embodiment. Therefore, the first color light generated in the LED package  220  and the light of the color generated by the phosphor can be mixed, and white light can be output upwardly. 
     Accordingly, in the second embodiment of the present disclosure, a thickness of the backlight unit  200  can be further reduced as compared to the first embodiment by implementing the single multi-pattern sheet  290 . 
     Hereinafter, the multi-pattern sheet  290  and the backlight unit  200  including the same according to the second embodiment of the present disclosure will be described in detail. 
     The glass complex body  291 , which is the base substrate of the multi-pattern sheet  290 , is formed of glass containing a phosphor. The glass complex body  291  can be formed by vitrifying a glass powder and a phosphor powder. Alternatively, the glass complex body  291  can be formed by sintering a glass frit containing a phosphor. 
     A thickness of the glass complex body  291  may be about 120 μm to about 250 μm for a desired color implementation, but the present disclosure is not limited thereto. 
     The plurality of reflective patterns  292  formed on the lower surface of the glass complex body  291  are spaced apart from each other by a predetermined distance and are arranged to correspond to the plurality of LED packages  220  mounted on the circuit board  210  and spaced apart from each other, respectively. At this time, a width of the reflective pattern  292  can be equal to or greater than a width of the LED package  220 . 
     When the width of the reflective pattern  292  is d, it is preferable that d satisfies the relationship of the following equation (1).
 
 d= 2{( b−c )tan(θ/2)}  equation (1)
 
     Here, b is a height (i.e., thickness) of the encapsulation member  230 , c is the height (i.e., thickness) of the LED package  220 , and θ is a beam angle of light emitted by the LED package  220 . The beam angle θ is the full beam angle of light emitted by the LED package  220  rather than the half beam angle of light emitted by the LED package  220 . At this time, the maximum thickness of the encapsulation member  230  on the LED package  220  can be four times the thickness of the LED package  220 . That is, the maximum value of (b−c) can be 4c. 
     On the other hand, the beam angle θ of the LED package  220  can be about 110 degrees to about 160 degrees, and the thickness c of the LED package  220  can be about 150 but the present disclosure is not limited thereto. Also, for example, each of the width and length of the LED package  220  can be about 700 μm. 
     For example, the reflective patterns  292  can be formed on a lower surface of the glass complex body  291  by a printing method, but the present disclosure is not limited thereto. The reflective patterns  292  can be formed of a material having a reflective property, for example, metal, titanium oxide (TiO 2 ), a dichroic dye, or the like, but the present disclosure is not limited thereto. 
     The reflective patterns  292  can be formed in a circular shape or a polygonal shape such as a tetragonal shape in plan view. 
     As describe above, the reflective patterns  292  can have different transmittances depending on a position so as to reflect a part of the incident light and transmit a remaining part of the incident light, and this will be described with reference to  FIGS. 6A to 6C . 
       FIG. 6A  is a schematic cross-sectional view of the reflective pattern according to the embodiment of the present disclosure, and  FIGS. 6B and 6C  are schematic plan views of the reflective pattern according to the embodiment of the present disclosure. 
     In  FIG. 6A , the reflective pattern  292  according to the embodiment of the present disclosure includes a first pattern layer  292   a , a second pattern layer  292   b  and a third pattern layer  292   c  sequentially formed on the glass complex body  291 . For example, the first, second and third pattern layers  292   a ,  292   b  and  292   c  can be formed of titanium oxide (TiO 2 ). 
     Here, an area of the second pattern layer  292   b  is smaller than an area of the first pattern layer  292   a , and an area of the third pattern layer  292   c  is smaller than the area of the second pattern layer  292   b . That is, the area of the second pattern layer  292   b  is smaller than the area of the first pattern layer  292   a  and larger than the area of the third pattern layer  292   c . Further, centers of the first, second and third pattern layers  292   a ,  292   b  and  292   c  are located on the same line. 
     Accordingly, a center portion of the reflective pattern  292  in which the first, second and third pattern layers  292   a ,  292   b  and  292   c  are stacked has the lowest light transmittance, an edge portion of the reflective pattern  292  in which only the first pattern layer  292   a  is located has the highest light transmittance, and a portion of the reflective pattern  292  in which the first and second pattern layers  292   a  and  292   b  are stacked has a light transmittance higher than that of the center portion of the reflective pattern  292  and lower than that of the edge portion of the reflective pattern  292 . 
     The reflective pattern  292  can have a circular shape in plan view as shown in  FIG. 6B  or a tetragonal shape in plan view as shown in  FIG. 6C , but the present disclosure is not limited thereto. 
     Alternatively, the reflective pattern  292  can have a transmission portion therein. 
     Meanwhile, the plurality of diffusion patterns  293  formed on the upper surface of the glass complex body  291  can include first patterns  293   a  and second patterns  293   b  alternately arranged. At this time, the first pattern  293   a  and the second pattern  293   b  adjacent to each other can be arranged to be spaced apart from each other or in contact with each other according to required optical characteristics. In this embodiment, the first pattern  293   a  and the second pattern  293   b  adjacent to each other are spaced apart from each other by a predetermined distance, as an example. 
     The diffusion pattern  293  including the first pattern  293   a  and the second pattern  293   b  corresponds to a lens pattern that performs a light diffusion function and can be formed as an embossed pattern or a depressed pattern. In this regard,  FIGS. 4 and 5  illustrate a diffusion pattern  293  including a first pattern  293   a  and a second pattern  293   b  of embossed patterns as an example. Alternatively, in  FIG. 7 , a diffusion pattern  294  including a first pattern  294   a  and a second pattern  294   b  is shown as an example. Here, the depressed diffusion pattern  294  can have a shape recessed into a substrate other than the glass complex body  291 . Alternatively, the depressed diffusion pattern  294  can have a shape recessed into the glass complex body  291 , and in this case, it is possible to realize an effect of reducing the thickness of the multi-pattern sheet  290  as compared with the embossed diffusion pattern  293  protruding out of the glass complex body  291 . 
     Referring again to  FIGS. 4 and 5 , the first pattern  293   a  and the second pattern  293   b  of the diffusion pattern  293  have different shapes. For example, the first pattern  293   a  can have a semicircular cross-sectional shape, and the second pattern  293   b  can have a triangular cross-sectional shape, but the present disclosure is not limited thereto. The shapes of the first pattern  293   a  and the second pattern  293   b  will be described with reference to  FIGS. 8A to 8D . 
       FIGS. 8A to 8D  are views schematically showing shapes of the diffusion pattern  293  according to the second embodiment of the present disclosure.  FIG. 8A  shows the first pattern  293   a  and  FIGS. 8B to 8D  show the second pattern  293   b.    
     As shown in  FIG. 8A , the first pattern  293   a  can be configured a curved surface having no vertex. For example, the first pattern  293   a  can have a hemispherical shape. 
     On the other hand, as shown in  FIGS. 8B to 8D , the second pattern  293   b  can be a horn shape having a vertex. At this time, the second pattern  293   b  can be a conical shape of  FIG. 8B , a polypyramid shape such as a quadrangular pyramid of  FIG. 8C , or a conical shape having a curved side surface of  FIG. 8D . However, the first pattern  293   a  and the second pattern  293   b  of the present disclosure are not limited thereto, and can have other shapes. 
     Here, the first pattern  293   a  can correspond to the reflective pattern  292  in one-to-one correspondence, and the second pattern  293   b  can correspond to a portion between the adjacent reflective patterns  292  in one-to-one correspondence. Accordingly, the first pattern  293   a  can correspond to the LED package  220  in one-to-one correspondence, and the second pattern  293   b  can correspond to a portion between the adjacent LED packages  220  in one-to-one correspondence. 
     By using such a multi-pattern sheet  290 , the second embodiment can obtain substantially the same optical characteristics as those of the first embodiment, and the thickness of the backlight unit  200  can be reduced. 
     This thickness reduction will be described with reference to  FIGS. 9 and 10  and Tables 1 and 2.  FIGS. 9 and 10  are views showing light distribution of the liquid crystal display devices according to the first and second embodiments of the present disclosure. Tables 1 and 2 show thicknesses of elements of the liquid crystal display devices excluding a liquid crystal panel according to the first and second embodiments of the present disclosure. These thicknesses are only an example, and the present disclosure is not limited thereto. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 elements 
                 thickness[mm] 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                   
                 optical sheet(270)(3 sheets) 
                 0.4 
               
               
                   
                   
                 0.155 
               
               
                   
                   
                 0.12 
               
               
                   
                 fluorescent sheet(260) 
                 0.13 
               
               
                   
                 diffusion plate(250) 
                 1.5 
               
               
                   
                 reflective pattern sheet(240) 
                 0.15 
               
               
                   
                 encapsulation member(230) 
                 0.5 
               
               
                   
                 LED package(220) 
                 — 
               
               
                   
                 circuit board(210) 
                 0.37 
               
               
                   
                 adhesive member(120) 
                 0.1 
               
               
                   
                 bottom cover(100) 
                 0.4 
               
               
                   
                 Total 
                 3.825 (100%) 
               
               
                   
                   
               
            
           
         
       
     
     
       
         
           
               
               
             
               
                 TABLE 2 
               
               
                   
               
               
                 elements 
                 thickness[mm] 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
            
               
                 optical sheet(270)(3 sheets) 
                 0.4 
               
               
                   
                 0.155 
               
               
                   
                 0.12 
               
            
           
           
               
               
               
            
               
                 multi pattern sheet(290) 
                 diffusion pattern(293) 
                 0.05 
               
               
                   
                 glass complex object(291) 
                 0.15 
               
               
                   
                 reflective pattern(292) 
                 0.02 
               
            
           
           
               
               
            
               
                 encapsulation member(230) 
                 0.5 
               
               
                 LED package(220) 
                 — 
               
               
                 circuit board(210) 
                 0.37 
               
               
                 adhesive member(120) 
                 0.1 
               
               
                 bottom cover(100) 
                 0.4 
               
               
                 Total 
                 2.265 (59%) 
               
               
                   
               
            
           
         
       
     
     As shown in  FIGS. 9 and 10 , it can be seen that the light distribution of the second embodiment is substantially the same as the light distribution of the first embodiment, and thus, in the second embodiment, optical characteristics and an image of substantially the same level as the first embodiment can be realized. 
     At this time, referring to Table 1, in the first embodiment, the reflective pattern sheet  240  has a thickness of 0.15 mm, the diffusion plate  250  has a thickness of 1.5 mm, and the thickness of the liquid crystal display device having the elements (except for the thickness of the liquid crystal panel) is 3.825 mm. 
     On the other hand, referring to Table 2, in the second embodiment, the multi-pattern sheet  290  has a thickness of 0.22 mm. That is, the diffusion pattern  293 , the glass complex body  291  and the reflective pattern  292  constituting the multi-pattern sheet  290  have thicknesses of 0.05 mm, 0.15 mm, and 0.02 mm, respectively and the thickness of the liquid crystal display device including the elements (except for the thickness of the liquid crystal panel) is 2.265 mm. 
     As described above, in the second embodiment, the thickness of the multi-pattern sheet  290  is 0.22 mm which is considerably reduced as compared with 1.78 mm (0.15 mm+1.5 mm+0.13 mm), which is a sum of the thicknesses of the reflective pattern sheet  240 , the diffusion plate  250 , and the fluorescent sheet  260  of the first embodiment. As a result, a total thickness (2.265 mm) of the second embodiment is only about 59% with respect to a total thickness (3.825 mm) of the first embodiment, and thus the thicknesses of the backlight unit and the liquid crystal display device can be drastically reduced. 
     As described above, according to the second embodiment using the multi-pattern sheet  290 , it is possible to effectively realize the backlight unit and the liquid crystal display device having a ultra thin thickness while securing substantially the same optical characteristics as the first embodiment. 
     Third Embodiment 
       FIG. 11  is a schematic cross-sectional view of a backlight unit according to a third embodiment of the present disclosure. 
     The backlight unit according to the third embodiment of the present disclosure has the same structure as that of the second embodiment except for the diffusion pattern of the multi-pattern sheet. The same reference numerals are given to the same parts as those of the second embodiment, and a description thereof will be omitted or simplified. 
     As shown in  FIG. 11 , the multi-pattern sheet  290  of the backlight unit  200  according to the third embodiment of the present disclosure can include a plurality of reflective patterns  292  formed on the lower surface of the glass complex body  291  and a plurality of diffusion patterns  295  formed on the upper surface of the glass complex body  291 . 
     Here, the plurality of diffusion patterns  295  can include a plurality of first patterns  295   a  and a plurality of second patterns  295   b  alternately arranged. At this time, a plurality of first patterns  295   a  can correspond to one reflective pattern  292 , and a plurality of second patterns  295   b  can correspond to a portion between adjacent reflective patterns  292 . Accordingly, the plurality of first patterns  295   a  can correspond to one LED package  220 , and a plurality of second patterns  295   b  can correspond to a portion between adjacent LED packages  220 . 
     In the figure, two first patterns  295   a  are shown as corresponding to one reflective pattern  292  or one LED package  220 , but the present disclosure is not limited thereto. 
     For example, each of the width and length of the LED package  220  can be 700 μm, and each of the width and length of the first pattern  295   a  and each of the width and length of the second pattern  295   b  can be 50 μm to 100 μm, preferably, 20 μm to 30 μm. 
     Here, the adjacent first patterns  295   a , the adjacent second patterns  295   b , and the first and second patterns  295   a  and  295   b  adjacent to each other can be spaced apart from each other or in contact with each other according to required optical characteristics. 
     The multi-pattern sheet  290  of the backlight unit  200  according to the third embodiment of the present disclosure can provide more uniform surface light as compared with the multi-pattern sheet  290  of the second embodiment. 
     As described above, according to the embodiments of the present disclosure, the reflective pattern is disposed over the LED package, and the diffusion means such as the diffusion plate or diffusion pattern is disposed thereover. Thus, light is prevented from being output upwardly from the LED package, and the optical distance can be decreased. Accordingly, the mura such as the hot spot can be prevented, thereby improving the image quality, and the backlight unit and the liquid crystal display device in a thin profile can be implemented. 
     Further, since the single multi-pattern sheet including the reflective pattern, the diffusion pattern and the phosphor is used, the thicknesses of the backlight unit and the liquid crystal display device can be drastically reduced, and the backlight unit and the liquid crystal display device having a ultra thin thickness can be realized while providing an image of a high quality. 
     It will be apparent to those skilled in the art that various modifications and variations can be made in a device of the present disclosure without departing from the sprit or scope of the embodiment. Thus, it is intended that the present disclosure covers the modifications and variations of this disclosure provided they come within the scope of the appended claims and their equivalents. 
     The various embodiments described above can be combined to provide further embodiments. All of the U.S. patents, U.S. patent application publications, U.S. patent applications, foreign patents, foreign patent applications and non-patent publications referred to in this specification and/or listed in the Application Data Sheet are incorporated herein by reference, in their entirety. Aspects of the embodiments can be modified, if necessary to employ concepts of the various patents, applications and publications to provide yet further embodiments. 
     These and other changes can be made to the embodiments in light of the above-detailed description. In general, in the following claims, the terms used should not be construed to limit the claims to the specific embodiments disclosed in the specification and the claims, but should be construed to include all possible embodiments along with the full scope of equivalents to which such claims are entitled. Accordingly, the claims are not limited by the disclosure.