Abstract:
A light emitting module is provided that has a diffusion lens that both reduces lens radius and renders uniform light luminance by preventing luminance non-uniformities caused by lens radius reduction. The light emitting module includes a circuit board, a light emitting device mounted on the circuit board, and a diffusion lens that controls the light emitted from the light emitting device and is installed on the circuit board so as to be located above the light emitting device.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims priority to Korean Application No. 10-2015-0166512, filed Nov.26, 2015, which is incorporated herein by reference in its entirety. 
       TECHNICAL FIELD 
       [0002]    This disclosure relates to a light emitting module, and more specifically to a diffusion lens that enables uniform luminance of emitted light and to a light emitting module emitting light having the same. 
       BACKGROUND ART 
       [0003]    Typically, in a light emitting module for backlighting or sidelighting a liquid crystal display, a light emitting device is mounted on a circuit board, and the light emitted from the light emitting device is dispersed and emitted at a wide angle via a lens. Using such a lens, a wide area may be uniformly illuminated with a small number of light emitting devices, by evenly dispersing the light emitted by the light emitting devices. 
         [0004]    Recently, there has been a need to reduce the diameters of the lenses of light emitting modules due to the trend toward miniaturization, and flange parts have been formed on the light emitting surface in order to reduce the lens diameter. 
         [0005]    However, in the prior art, luminance non-uniformity (mura) has occurred at the flange part when light diffused by the upwardly-sloping surface or flat surface formed on the back side (lower surface) of the lens is emitted toward the flange part, and as a result there has been a problem of non-uniform luminance. 
         [0006]    Patent Reference 0001: Republic of Korea Unexamined Patent Publication 10-2015-0082394 (published 2015.07.15) 
       SUMMARY 
       [0007]    The technical task of this disclosure is to provide a light emitting module comprising a diffusion lens that both reduces lens radius and renders uniform light luminance by preventing luminance non-uniformities caused by lens radius reduction. 
         [0008]    The diffusion lens according to one embodiment of this disclosure, in order to achieve the task, comprises a light incidence part that forms an inner surface where light emitted from a light emitting device is incident, a light emission part that forms an outer surface where light incident on the light incidence part is emitted, and furnishes a flange part that breaks the curvature of the emission side at the end so that the diameter of the lens is reduced, and an back-side part that forms a lens lower surface that connects the light incidence part and light emission part and furnishes a 1st sloped surface that is formed sloping upward from the light incidence part, and a 2nd sloped surface that is formed sloping downward from the end of the 1st sloped surface; because the light diffused by the 2nd sloped surface of the back-side part offsets light emitted from the flange part, luminance may be rendered uniform so as to prevent non-uniformities at the flange part. 
         [0009]    In addition, the inflection point between the 1st sloped surface and the 2nd sloped surface may be formed at 80±10% of the total lens radius. 
         [0010]    In addition, the 2nd sloped surface may be formed at a downward sloping angle of 10° or less with respect to the horizontal. 
         [0011]    In addition, the flange part may comprise: a 1st inflection point where the curvature of the emission surface is broken at the end of the light emission part; and a 2nd inflection point that is formed at a certain angle away from the 1st inflection point along the emission surface so as to increase the diffusion angle; and the 1st inflection point and the 2nd inflection point may be located on the horizontal of the back-side part formed on the 2nd sloped surface. 
         [0012]    In addition, the slope angle between the 1st inflection point and the 2nd inflection point may be 5° or less relative to the vertical. 
         [0013]    In addition, the light emitting module according to one embodiment of this disclosure may comprise: a circuit board; a light emitting device mounted on the circuit board; and a diffusion lens that controls the light emitted from the light emitting device and is installed on the circuit board so as to be located on top of the light emitting device. 
         [0014]    This disclosure enables the prevention of luminance non-uniformities (mura) on the flange party, by making luminance uniform by offsetting the light emitted by the flange part with the light diffused from the downward-sloping surface of the lens back-side part. 
         [0015]    Accordingly, this disclosure has the effect that it may prevent the occurrence of luminance non-uniformity (mura), which occurs at the inflection point of the flange part when the curvature of the emitting surface is broken in order to reduce lens diameter, by rendering the luminance uniform by offsetting the light by means of the shape of the back-side part. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]      FIG. 1  is a schematic cross-section illustrating the light emitting module according to one embodiment of this disclosure. 
           [0017]      FIG. 2  is a perspective view of a diffusion lens used in a light emitting module according to one embodiment of this disclosure. 
           [0018]      FIG. 3  is a frontal view of a diffusion lens used in a light emitting module according to one embodiment of this disclosure. 
           [0019]      FIG. 4  is a schematic cross-section illustrating a diffusion lens used in a light emitting module according to one embodiment of this disclosure. 
           [0020]      FIG. 5  is an expanded view of Part A of  FIG. 4 . 
           [0021]      FIGS. 6 and 7  are schematic views comparing the light emission from the flange part of the light emitting part at difference slope angles of the downward-sloping surface formed on the back-side part of the diffusion lens. 
           [0022]      FIGS. 8 and 9  are experimental photographs comparing the presence or absence of light non-uniformities (mura) at the flange part of the light emitting part at difference slope angles of the downward-sloping surface formed on the back-side part of the diffusion lens. 
           [0023]      FIG. 10  is a graph comparing the regions of occurrence of light non-uniformities (mura) at the flange part of the light emitting part at difference slope angles of the downward-sloping surface formed on the back-side part of the diffusion lens. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0024]    Hereinbelow, the diffusion lens and light emitting module having the same according to an embodiment of the present disclosure will be described, with reference to the attached drawings. Please note that in describing this disclosure, the detailed explanation is omitted of functions and components which are common knowledge and are judged to unnecessarily obscure the core intent of the disclosure. 
         [0025]    As shown in  FIG. 1 , the light emitting module  10  according to one embodiment of this disclosure may comprise a circuit board  100 , light-emitting device  200  and diffusion lens  300 . 
         [0026]    The circuit board  100  is a printed circuit board (PCB) whereon a circuit pattern is formed. Here, although a single light emitting device  200  is depicted as being mounted on the circuit board  100 , a plurality of light emitting devices  200  may be arranged on the circuit board  100 , and a diffusion lens  300  may be placed above each light emitting device  200 . 
         [0027]    The light emitting device  200  is mounted on the circuit board  100 . The light emitting device  200  is placed inside the below-described light incidence part  310 . The light emitting device  200  may be configured as an LED package consisting of a light emitting diode (LED) chip. Such an LED package is a widely-known technology and therefore understandable, and a detailed description is accordingly omitted. 
         [0028]    The diffusion lens  300  serves to control the light emitted from the light emitting device  200 . 
         [0029]    The diffusion lens  300  is installed on the circuit board  100  in such a way as to be located above the light emitting device  200 . 
         [0030]    The diffusion lens  300  is held in place by a plurality of leg parts  301  being coupled to the circuit board  100 . For example, the respective front ends of the leg parts  301  of the diffusion lens  300  may be adhered to the circuit board  100  by an adhesive, or may be fitted into holes (not shown) formed on the circuit board  100 . In addition, in this embodiment the configuration has been depicted in which the lens leg parts  301  are four (4) in number, but this is not limiting and the leg parts  301  may also be configured as three (3). In addition, the lens leg parts  301  may be formed on the 1st sloped side  331  or 2nd sloped side  332  of the back-side part  330 . 
         [0031]    As shown in  FIGS. 2 through 5 , the diffusion lens  300  used in the light emitting module  10  according to one embodiment of this disclosure may comprise a light-incidence part  310 , light emitting part  320 , and back-side part  330 . 
         [0032]    The light-incidence part  310  forms an inner surface on which light emitted from the light emitting device  200  is incident on the interior of the lens. 
         [0033]    The light-incidence part  310  may have a form in which the width thereof becomes narrower moving upward from the entrance. In addition, the entrance width of the light-incidence part  310  may be greater than the width of the light emitting device  200 . 
         [0034]    The height of the light-incidence part  310  may be regulated according to the orientation angle of the light emitting device  200 , the shape of the lens upper surface, the desired light orientation distribution, etc. 
         [0035]    The light emitting part  320  forms an outer surface of the lens that emits light that is incident on the light incidence part  310 . 
         [0036]    The shape of the emitting surface of the light emitting part  320  is formed with a convex ring shape or with flattened curvature. 
         [0037]    The light emitting part  320  may be furnished with a flange part  321  that reduces the diameter of the lens by breaking the curvature of the emitting surface at the end thereof 
         [0038]    The flange part  321  may comprise a 1st inflection point  321   a  and a 2nd inflection point  32 l b.    
         [0039]    The 1st inflection point  321   a  serves to reduce the diameter of the lens by breaking the curvature of the emitting surface at the end of the light emitting part  320 . 
         [0040]    The 2nd inflection point  321   b  serves to increase the diffusion angle and is formed at a certain angle away from the 1st inflection point  321   a  along the emitting surface. 
         [0041]    The 1st inflection point  321   a  and 2nd inflection point  321   b  are located on the perpendicular of the back-side part  330  whereon the 2nd sloped surface  332  is formed. 
         [0042]    The slope angle β between the 1st inflection point  321   a  and 2nd inflection point  321   b  is formed so as to be 5° or less relative to the perpendicular. For example, the slope angle β formed between the line connecting the 1st inflection point  321   a  and 2nd inflection point  321   b , and the perpendicular at the 2nd inflection point  321   b , is 5° or less. 
         [0043]    The back-side part  330  forms a lower lens surface connecting the light incidence part  310  and the light emission part  320 . 
         [0044]    The back-side shape of the back-side part  330  is formed at a certain angle and curvature so as to regulate the reflected light. By this means, the light incident on the back-side part  330  may be refracted so as to expand the diffusion range. 
         [0045]    The back-side part  330  may be furnished with a 1st sloped surface  331  formed sloping upward from the light-incidence part  310 , and a 2nd sloped surface  332  formed sloping downward from the end of the 1st sloped surface  331 . In addition, the back-side part  330  may either comprise or not comprise a surface  333  that extends flat from the 2nd sloped surface  332  to the outer edge. 
         [0046]    The inflection point R 3  between the 1st sloped surface  331  and 2nd sloped surface  332  is formed at 80±10% of the total lens radius Rl. In other words, in the back-side part  330 , the inflection point R 3  of the 2nd sloped surface  332  is located within the range of 80±10% of the total lens radius Rl. 
         [0047]    The 1st sloped surface  331  starts from the end of the light-incidence part  310 , and is formed at a slope angle a of 10° or less above the horizontal. 
         [0048]    The 2nd sloped surface  332  is formed at a slope angle γ of 10° or less below the horizontal. 
         [0049]    The occurrence of luminance non-uniformity at the flange part  321  may be prevented by offsetting the light emitted from the flange part  321  with light diffused by the 2nd sloped surface  332 , which is the downwardly-sloping surface of the back-side part  330 , so as to render luminance uniform. In other words, luminance non-uniformity occurs at the inflection points  321   a ,  321   b  of the flange part  321  when the curvature of the emitting surface is broken in order to reduce lens diameter, and this is offset with light from the shape of the back-side part  330  so as to render the luminance uniform and prevent the occurrence of luminance non-uniformity. 
         [0050]      FIGS. 6 and 7  are schematic views comparing the light emission from the flange part of the light emitting part at difference slope angles of the downward-sloping surface formed on the back-side part of the diffusion lens. 
         [0051]    As shown in  FIG. 6 , if the slope angle γ of the downward-sloping 2nd sloped surface  332  of the back-side part  330  is formed at 0-10°, then within the range between the 1st inflection point  321   a  and 2nd inflection point  321   b  emitted light is refracted within the lens radius, and beyond the 2nd inflection point  321   b  the emitted light is refracted outside the lens radius. 
         [0052]    In this way, the emitted light refracted inside the lens radius at the flange part  321   b  and the emitted light refracted outside the lens radius offset each other so that the occurrence of mura (luminance non-uniformity) is reduced and luminance is rendered uniform. 
         [0053]    However, as shown in  FIG. 7 , if the slope angle γ of the downward-sloping 2nd sloped surface  332  of the back-side part  330  is greater than 10°, e.g. 11°, then within the range between the 1st inflection point  321   a  and 2nd inflection point  321   b  emitted light is refracted outside the lens radius, and beyond the 2nd inflection point  321   b  the emitted light is also refracted outside the lens radius. 
         [0054]    In this way, all light emitted from the flange part  321  is refracted outside the lens radius, and is not offset, so that the occurrence of mura increases and luminance becomes non-uniform. 
         [0055]      FIGS. 8 and 9  are experimental photographs comparing the presence or absence of light non-uniformities (mura) at the flange part of the light emitting part at difference slope angles of the downward-sloping surface formed on the back-side part of the diffusion lens. 
         [0056]    As shown in  FIG. 8 , if the slope angle γ of the downward sloping 2nd sloped surface  332  of the back-side part  330  is greater than 10°, e.g. 11°, the evaluation value in sections 166-181 is Max=112.35, Min=−68.79, Avg=−1.53, which is other than zero (0) and indicates uniformed luminance. 
         [0057]    However, as shown in  FIG. 9 , in this disclosure, if the slope angle γ of the downward sloping 2nd sloped surface  332  of the back-side part  330  is formed so as to be 0-10°, then in the same sections 166-181 as in  FIG. 8 , the evaluation values are smaller than in  FIG. 8 , specifically Max=9.36, Min=−38.48, Avg=−1.17, which approaches zero (0) and indicates that the luminance is made uniform. 
         [0058]      FIG. 10  is a graph comparing the regions of occurrence of light non-uniformities (mura) at the flange part of the light emitting part at difference slope angles of the downward-sloping surface formed on the back-side part of the diffusion lens. 
         [0059]    As shown in  FIG. 10 , there is a substantial difference in the sections in which luminance non-uniformity (mura) occurs (sections 166-181) at the flange part of the light emitting part, for different slope angles of the 2nd sloped face  332  which is the downward-facing sloped surface of the back-side part  330  (γ=0°,y=2.5°,γ=5°,γ=7.5°,γ=10°,γ=11°). Specifically, in sections 166-181where luminance non-uniformity (mura) occurs, if the slope angle γof the downward-sloping surface  332  of the back-side part  330  is 0-10°, the luminance will be uniform, while if the slope angle γ of the downward-sloping surface  332  of the back-side part  330  is greater than 10°, e.g. 11°, the luminance is non-uniform. 
         [0060]    As shown in Table 1 below, as the mura value approaches zero (0), the light is increasingly uniform, and in the 0-10° distribution of the slope angle γ of the downward-sloping surface  332  of the back-side part  330 , the mura value approaches zero (0) so that luminance is uniform without any change in mura, while if the slope angle γ of the downward-sloping surface  332  of the back-side part  330  exceeds 10°, the mura value abruptly falls, indicating non-uniform luminance. 
         [0000]    
       
         
               
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
             
             
               
                 Sections with MURA 
                 166 
                 167 
                 168 
                 169 
                 170 
                 171 
                 172 
                 173 
                 174 
               
               
                   
               
             
          
           
               
                 MURA 
                 MURA #0 Downward 
                 0.7319 
                 1.4395 
                 1.4341 
                 1.0491 
                 1.3402 
                 1.4424 
                 1.2091 
                 0.949 
                 0.7263 
               
               
                 VALUE 
                 sloping angle (γ = 0°) 
               
               
                   
                 MURA #1 Downward 
                 0.7319 
                 1.4395 
                 1.4341 
                 1.0491 
                 1.3402 
                 1.4424 
                 1.2091 
                 0.949 
                 0.7263 
               
               
                   
                 sloping angle (γ = 2.5°) 
               
               
                   
                 MURA #2 Downward 
                 0.2034 
                 0.9221 
                 0.6347 
                 0.3171 
                 1.1325 
                 1.1114 
                 1.3079 
                 1.1403 
                 1.1415 
               
               
                   
                 sloping angle (γ = 5°) 
               
               
                   
                 MURA #3 Downward 
                 0.9221 
                 0.6347 
                 0.3171 
                 1.1325 
                 1.1114 
                 1.3079 
                 1.1403 
                 1.1415 
                 1.5367 
               
               
                   
                 sloping angle (γ = 7.5°) 
               
               
                   
                 MURA #4 Downward 
                 0.0576 
                 0.8126 
                 0.4034 
                 −0.3488 
                 −0.0842 
                 0.6226 
                 0.6688 
                 0.4031 
                 0.325 
               
               
                   
                 sloping angle (γ = 10°) 
               
               
                   
                 MURA #5 Downward 
                 −2.359 
                 −1.6481 
                 −1.9309 
                 −2.5312 
                 −2.0421 
                 −2.1885 
                 −2.241 
                 −2.367 
                 −2.1597 
               
               
                   
                 sloping angle (γ = 11°) 
               
               
                   
               
             
          
           
               
                   
                 Sections with MURA 
                 175 
                 176 
                 177 
                 178 
                 179 
                 180 
                 181 
               
               
                   
                   
               
             
          
           
               
                   
                 MURA 
                 MURA #0 Downward 
                 1.1913 
                 0.8113 
                 0.4651 
                 0.0607 
                 −0.2247 
                 0.3636 
                 0.152 
               
               
                   
                 VALUE 
                 sloping angle (γ = 0°) 
               
               
                   
                   
                 MURA #1 Downward 
                 1.1913 
                 0.8113 
                 0.4651 
                 0.0607 
                 −0.2247 
                 0.3635 
                 0.152 
               
               
                   
                   
                 sloping angle (γ = 2.5°) 
               
               
                   
                   
                 MURA #2 Downward 
                 1.5367 
                 1.5825 
                 1.1556 
                 0.7146 
                 1.0297 
                 0.8284 
                 0.8118 
               
               
                   
                   
                 sloping angle (γ = 5°) 
               
               
                   
                   
                 MURA #3 Downward 
                 1.5825 
                 1.1556 
                 0.7146 
                 1.0297 
                 0.8284 
                 0.8118 
                 0.6696 
               
               
                   
                   
                 sloping angle (γ = 7.5°) 
               
               
                   
                   
                 MURA #4 Downward 
                 1.3607 
                 1.134 
                 0.9933 
                 0.6576 
                 −0.0416 
                 0.5264 
                 1.0846 
               
               
                   
                   
                 sloping angle (γ = 10°) 
               
               
                   
                   
                 MURA #5 Downward 
                 −2.5458 
                 −2.1677 
                 −2.0987 
                 −2.4604 
                 −1.5212 
                 −1.9756 
                 −1.4458 
               
               
                   
                   
                 sloping angle (γ = 11°) 
               
               
                   
                   
               
             
          
         
       
     
         [0061]    Accordingly, this disclosure may prevent the occurrence of luminance non-uniformity (mura) that occurs at the inflection point of the flange part when the curvature of the emitting surface is broken in order to reduce lens diameter, by rendering the luminance uniform by the light diffused by the setting of the downward-sloping surface slope angle offsetting the light emitted from the flange part. 
         [0062]    Hereinabove, embodiments of this disclosure were described with reference to the attached drawings, but a person of ordinary ability in the art to which this disclosure pertains will be able to understand that this disclosure can be implemented in different specific forms without altering the necessary characteristics or technical idea thereof. Therefore, it must be understood that the above-described embodiments are illustrative and non-limiting in all respects. The scope of this disclosure is set forth in the claims below rather than in the detailed description; all alterations or altered forms derived from the meaning and scope and equivalents of the claims must be considered to be included within the scope of this disclosure.