TECHNICAL FIELD 
       [0001]    The present invention relates to a light flux controlling member that controls the traveling direction of light emitted from a light emitting element. The present invention relates to an illumination device having the light flux controlling member, which can be used instead of an incandescent lamp or a fluorescent lamp. 
       BACKGROUND ART 
       [0002]    Recently, from the viewpoint of energy saving or environmental conservation, illumination devices (such as LED bulbs or LED fluorescent lamps) using a light emitting diode (LED) as a light source have been used instead of incandescent lamps or fluorescent lamps. 
         [0003]    However, a conventional illumination device using an LED as a light source can emit light only in the forward direction but cannot emit light in all directions like an incandescent lamp Or a fluorescent lamp. Accordingly, the conventional illumination device cannot extensively illuminate a room using reflected light from a ceiling or walls. 
         [0004]    In order to make light distribution characteristics of such a conventional illumination device using an LED as a light source close to the light distribution characteristics of an incandescent lamp or a fluorescent lamp, it has been proposed that the traveling direction of light emitted from the LED is controlled by the use of a light flux controlling member (for example, see Patent Documents 1 to 3). 
         [0005]      FIG. 1  is a diagram illustrating the configuration of a light direction converting element (light flux controlling member) described in Patent Document 1.  FIG. 1A  is a plan view of the light direction converting element and  FIG. 1B  is a cross-sectional view taken along line A-A of  FIG. 1A . As shown in the drawing, light direction converting element  101  reflects light from LED  100  by the use of surface B (paraboloid of revolution)  102  and surface E (beveled inclined surface)  103 , further reflects the light reflected by surface B  102  and surface E  103  by the use of surface D  104  (the surface of a board having LED  100  mounted thereon), and emits the light reflected by surface D  104  from surface B  102 . Light direction converting element  101  emits the light reflected by surface B  102  and arriving at surface C  105  to an external oblique rear side (downside). 
         [0006]    By controlling the traveling direction of light from LED  100  by the use of light direction converting element  101 , it is possible to obtain emitted light in the upward direction (forward direction) and the horizontal direction (the direction perpendicular to the forward direction). Therefore, it can be thought that the light distribution characteristics are made to be close to the light distribution characteristics of an incandescent lamp or a fluorescent lamp, by applying the light direction converting element  101  to the conventional illumination device using an LED as a light source. 
       CITATION LIST 
     Patent Literature 
       [0007]    PTL 1 Japanese Patent Application Laid-Open No. 2008-216540 
         [0008]    PTL 2 Japanese Patent Application Laid-Open No. 2007-034307 
         [0009]    PTL 3 Japanese Patent Application Laid-Open No. 2007-048883 
       SUMMARY OF INVENTION 
     Technical Problem 
       [0010]    However, light direction converting element  101  shown in  FIG. 1 , out of light emitted from LED  100 , light satisfying the total reflection condition with respect to B surface  102  is reflected by B surface  102  and light not satisfying the total reflection condition with respect to B surface  102  is transmitted by B surface  102 . Therefore, when light direction converting element  101  shown in  FIG. 1  is used, the light not satisfying the total reflection condition with respect to B surface  102  is color-separated at the time of passing through B surface  102 . As a result, irregularity in color is caused which degrades the quality of illumination. Particularly, when the light-emitting area of LED  100  is too large to consider as a point light source, the ratio of light not satisfying the total reflection condition with respect to B surface  102  increases and the irregularity in color of emitted light is more easily caused. 
         [0011]    Therefore, an object of the invention is to provide a light flux controlling member which can make light distribution characteristics closer to those of an incandescent lamp or a fluorescent lamp and an illumination device having the light flux controlling member. 
       Solution to Problem 
       [0012]    According to an aspect of the invention, there is provided a light flux controlling member including: a cap that is to be disposed over one or two or more light emitting elements disposed on a board with an air layer interposed therebetween and that is configured to intersect an optical axis of the light-emitting element; and a sidewall configured to extend from an outer rim of the cap to the board, wherein: the inner surface of the cap is a concave surface of which the central part is located closer to the light emitting element than the outer circumference is; an inner surface of the cap is covered with a transflective film; the transflective film is configured to reflect a part of light from the light emitting element to the sidewall and transmit the other part of the light from the light emitting element; an outer surface of the cap is configured to emit light incident through the transflective film to the outside; and the sidewall is configured to emit light reflected by the transflective film and arriving at the inner surface of the sidewall and light directly arriving at the inner surface of the sidewall from the light emitting element from the outer surface of the sidewall to the outside. 
         [0013]    According to another aspect of the invention, there is provided a light flux controlling member which is to be disposed over one or two or more light emitting elements disposed on a board with an air layer interposed therebetween, wherein: a transflective film is formed on a surface intersecting partial light of light emitted from the light emitting element; and the transflective film is configured to reflect a part of the partial light and transmit the other part of the partial light. 
         [0014]    According to still another aspect of the invention, there is provided an illumination device including: a board on which one or two or more light emitting elements are disposed; a transflective part that is configured to intersect partial light of light emitted from the light emitting element and that is configured to reflect a part of the partial light and transmit the other part of the partial light; and a transmissive part configured to emit light reflected by the transflective part and light arriving directly from the light emitting element to the outside. 
       Advantageous Effects of Invention 
       [0015]    Since the light flux controlling member according to the invention reflects a part of light from the light emitting element by the use of the transflective film and does not reflect the light from the light emitting element by total reflection, it is possible to prevent irregularity in color from occurring in emitted light and to extensively emit light from the sidewall. 
         [0016]    The illumination device according to the invention can make the light distribution characteristics of illumination light close to the light distribution characteristics of an incandescent lamp or a fluorescent lamp. The illumination device according to the invention can emit illumination light with high quality and without irregularity in color. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0017]      FIG. 1A  is a plan view of a conventional light flux controlling member (light direction converting element) and  FIG. 1B  is a cross-sectional view taken along line A-A of  FIG. 1A ; 
           [0018]      FIG. 2A  is a plan view of an illumination device according to Embodiment 1,  FIG. 2B  is a front view of the illumination device according to Embodiment 1,  FIG. 2C  is a cross-sectional view taken along line B-B of  FIG. 2A , and  FIG. 2D  is a bottom view of the illumination device according to Embodiment 1; 
           [0019]      FIG. 3A  is a plan view of a light flux controlling member of the illumination device according to Embodiment 1,  FIG. 3B  is a front view of the light flux controlling member of the illumination device according to Embodiment 1,  FIG. 3C  is a cross-sectional view taken along line C-C of  FIG. 3A , and  FIG. 3D  is a bottom view of the light flux controlling member of the illumination device according to Embodiment 1; 
           [0020]      FIG. 4A  is a schematic diagram illustrating a light reflecting function of a transflective film of the light flux controlling member and  FIG. 4B  is a schematic diagram illustrating a light transmitting function of the transflective film of the light flux controlling member; 
           [0021]      FIG. 5  is a graph illustrating the light distribution characteristics of the illumination device according to Embodiment 1 when optical reflectance of the transflective film is 55%; 
           [0022]      FIG. 6  is a graph illustrating light distribution characteristics of the illumination device according to Embodiment 1 when optical reflectance of the transflective film is 65%; 
           [0023]      FIG. 7  is a graph illustrating light distribution characteristics of the illumination device according to Embodiment 1 when optical reflectance of the transflective film is 75%; 
           [0024]      FIG. 8  is a graph illustrating light distribution characteristics of the illumination device according to Embodiment 1 when optical reflectance of the transflective film is 85%; 
           [0025]      FIG. 9  is a diagram illustrating a method of measuring the light distribution characteristics of the illumination device; 
           [0026]      FIG. 10  is a cross-sectional view of an illumination device according to Embodiment 2; 
           [0027]      FIG. 11  is a graph illustrating the light distribution characteristics of the illumination device according to Embodiment 2; 
           [0028]      FIG. 12  is a cross-sectional view of an illumination device according to Embodiment 3; 
           [0029]      FIG. 13  is a graph illustrating the light distribution characteristics of the illumination device according to Embodiment 3; 
           [0030]      FIG. 14  is a cross-sectional view of an illumination device according to Embodiment 4; 
           [0031]      FIG. 15  is a graph illustrating the light distribution characteristics of the illumination device according to Embodiment 4; 
           [0032]      FIG. 16  is a cross-sectional view of an illumination device according to Embodiment 5; 
           [0033]      FIG. 17  is a graph illustrating the light distribution characteristics of the illumination device according to Embodiment 5; 
           [0034]      FIG. 18  is a cross-sectional view of an illumination device according to Embodiment 6; 
           [0035]      FIG. 19  is a cross-sectional view of an illumination device according to Embodiment 7; 
           [0036]      FIG. 20  is a cross-sectional view of an illumination device according to Embodiment 8; 
           [0037]      FIG. 21  is a graph illustrating the light distribution characteristics of the illumination device according to Embodiment 8; 
           [0038]      FIG. 22  is a cross-sectional view of an illumination device according to Embodiment 9; 
           [0039]      FIG. 23  is a graph illustrating the light distribution characteristics of the illumination device according to Embodiment 9; 
           [0040]      FIG. 24A  is a cross-sectional view of an illumination device according to Embodiment  10  and  FIG. 24B  is a plan view of a board on which plural light emitting elements are mounted; 
           [0041]      FIG. 25  is a graph illustrating the light distribution characteristics of the illumination device according to Embodiment 10; 
           [0042]      FIG. 26A  is a cross-sectional view of an illumination device according to Embodiment  11  and  FIG. 26B  is a plan view of a board on which plural light emitting elements are mounted; 
           [0043]      FIG. 27A  is a front view of the illumination device according to Embodiment 11,  FIG. 27B  is a plan view of the illumination device according to Embodiment 11,  FIG. 27C  is a bottom view of the illumination device according to Embodiment  11 , and  FIG. 27D  is a cross-sectional view taken along line D-D of  FIG. 27A ; 
           [0044]      FIG. 28  is a graph illustrating the light distribution characteristics of the illumination device according to Embodiment 11; 
           [0045]      FIG. 29  is a cross-sectional view of an illumination device according to Embodiment 12; 
           [0046]      FIG. 30A  is a perspective view illustrating the appearance of an illumination device according to Embodiment 13 and 
           [0047]      FIG. 30B  is a transparent perspective view of the illumination device according to Embodiment 13; 
           [0048]      FIG. 31A  is a cross-sectional view of the illumination device according to Embodiment 13 taken along a second direction and  FIG. 31B  is a plan view of a board on which plural light emitting elements are mounted; 
           [0049]      FIG. 32A  is a bottom view of a light flux controlling member of the illumination device according to Embodiment 13,  FIG. 32B  is a plan view of the light flux controlling member of the illumination device according to Embodiment 13,  FIG. 32C  is a cross-sectional view taken along line F-F of  FIG. 32B , and  FIG. 32D  is a cross-sectional view taken along line G-G of  FIG. 32B ; 
           [0050]      FIG. 33A  is a schematic diagram illustrating a light reflecting function of a transflective film of the light flux controlling member and  FIG. 33B  is a schematic diagram illustrating a light transmitting function of the transflective film of the light flux controlling member; 
           [0051]      FIG. 34  is a graph illustrating the light distribution characteristics of the illumination device according to Embodiment  13  when optical reflectance of the transflective film is 50%; 
           [0052]      FIG. 35  is a graph illustrating the light distribution characteristics of the illumination device according to Embodiment  13  when optical reflectance of the transflective film is 60%; 
           [0053]      FIG. 36  is a graph illustrating the light distribution characteristics of the illumination device according to Embodiment 13 when optical reflectance of the transflective film is 70%; 
           [0054]      FIG. 37  is a graph illustrating the light distribution characteristics of the illumination device according to Embodiment 13 when optical reflectance of the transflective film is 80%; 
           [0055]      FIG. 38  is a diagram illustrating a method of measuring the light distribution characteristics of the illumination device; 
           [0056]      FIG. 39A  is a cross-sectional view of the illumination device according to Embodiment 14 taken along a second direction and  FIG. 39B  is a plan view of a board on which plural light emitting elements are mounted; 
           [0057]      FIG. 40A  is a bottom view of a light flux controlling member of the illumination device according to Embodiment 14,  FIG. 40B  is a plan view of the light flux controlling member of the illumination device according to Embodiment 14,  FIG. 40C  is a cross-sectional view taken along line H-H of  FIG. 40B , and  FIG. 40D  is a cross-sectional view taken along line I-I of  FIG. 40B ; 
           [0058]      FIG. 41  is a graph illustrating the light distribution characteristics of the illumination device according to Embodiment 14 when optical reflectance of the transflective film is 50%; 
           [0059]      FIG. 42  is a graph illustrating the light distribution characteristics of the illumination device according to Embodiment 14 when optical reflectance of the transflective film is 60%; 
           [0060]      FIG. 43  is a graph illustrating the light distribution characteristics of the illumination device according to Embodiment 14 when optical reflectance of the transflective film is 70%; 
           [0061]      FIG. 44  is a graph illustrating the light distribution characteristics of the illumination device according to Embodiment 14 when optical reflectance of the transflective film is 80%; 
           [0062]      FIG. 45A  is a cross-sectional view of the illumination device according to Embodiment 15 taken along a second direction and  FIG. 45B  is a plan view of a board on which plural light emitting elements are mounted; 
           [0063]      FIG. 46A  is a bottom view of a light flux controlling member of the illumination device according to Embodiment 15,  FIG. 46B  is a plan view of the light flux controlling member of the illumination device according to Embodiment 15,  FIG. 46C  is a cross-sectional view taken along line J-J of  FIG. 46B , and  FIG. 46D  is a cross-sectional view taken along line K-K of  FIG. 46B ; 
           [0064]      FIG. 47  is a graph illustrating the light distribution characteristics of the illumination device according to Embodiment 15 when optical reflectance of the transflective film is 50%; 
           [0065]      FIG. 48  is a graph illustrating the light distribution characteristics of the illumination device according to Embodiment 15 when optical reflectance of the transflective film is 60%; 
           [0066]      FIG. 49  is a graph illustrating the light distribution characteristics of the illumination device according to Embodiment 15 when optical reflectance of the transflective film is 70%; 
           [0067]      FIG. 50  is a graph illustrating the light distribution characteristics of the illumination device according to Embodiment 15 when optical reflectance of the transflective film is 80%; 
           [0068]      FIG. 51A  is a cross-sectional view of the illumination device according to Embodiment 16 taken along a second direction and  FIG. 51B  is a plan view of a board on which plural light emitting elements are mounted; 
           [0069]      FIG. 52A  is a bottom view of a light flux controlling member of the illumination device according to Embodiment 16,  FIG. 52B  is a plan view of the light flux controlling member of the illumination device according to Embodiment 16,  FIG. 52C  is a cross-sectional view taken along line L-L of  FIG. 52B , and  FIG. 52D  is a cross-sectional view taken along line M-M of  FIG. 52B ; 
           [0070]      FIG. 53  is a graph illustrating the light distribution characteristics of the illumination device according to Embodiment 16 when optical reflectance of the transflective film is 50%; 
           [0071]      FIG. 54  is a graph illustrating the light distribution characteristics of the illumination device according to Embodiment 16 when optical reflectance of the transflective film is 60%; 
           [0072]      FIG. 55  is a graph illustrating the light distribution characteristics of the illumination device according to Embodiment 16 when optical reflectance of the transflective film is 70%; 
           [0073]      FIG. 56  is a graph illustrating the light distribution characteristics of the illumination device according to Embodiment 16 when optical reflectance of the transflective film is 80%; 
           [0074]      FIG. 57  is a cross-sectional view of an illumination device according to Embodiment 17 taken along a second direction; 
           [0075]      FIG. 58  is a graph illustrating the light distribution characteristics of the illumination device according to Embodiment 17 when optical reflectance of the transflective film is 50%; 
           [0076]      FIG. 59  is a graph illustrating the light distribution characteristics of the illumination device according to Embodiment 17 when optical reflectance of the transflective film is 60%; 
           [0077]      FIG. 60  is a graph illustrating the light distribution characteristics of the illumination device according to Embodiment 17 when optical reflectance of the transflective film is 70%; 
           [0078]      FIG. 61  is a graph illustrating the light distribution characteristics of the illumination device according to Embodiment 17 when optical reflectance of the transflective film is 80%; 
           [0079]      FIG. 62  is a perspective view of an illumination device according to Embodiment 18; 
           [0080]      FIG. 63A  is a cross-sectional view of the illumination device according to Embodiment 18 taken along a second direction and  FIG. 63B  is a plan view of a board on which plural light emitting elements are mounted; 
           [0081]      FIG. 64A  is a plan view of a light flux controlling member of the illumination device according to Embodiment 18,  FIG. 64B  is a cross-sectional view taken along line N-N of  FIG. 64A , and  FIG. 64C  is a bottom view of the light flux controlling member of the illumination device according to Embodiment 18; 
           [0082]      FIG. 65  is a graph illustrating the light distribution characteristics of the illumination device according to Embodiment 18 when optical reflectance of the transflective film is 50%; 
           [0083]      FIG. 66  is a graph illustrating the light distribution characteristics of the illumination device according to Embodiment 18 when optical reflectance of the transflective film is 60%; 
           [0084]      FIG. 67  is a graph illustrating the light distribution characteristics of the illumination device according to 
           [0085]    Embodiment 18 when optical reflectance of the transflective film is 70%; 
           [0086]      FIG. 68  is a graph illustrating the light distribution characteristics of the illumination device according to Embodiment 18 when optical reflectance of the transflective film is 80%; 
           [0087]      FIG. 69A  is a cross-sectional view of the illumination device according to Embodiment 19 taken along a second direction and  FIG. 69B  is a plan view of a board on which plural light emitting elements are mounted; 
           [0088]      FIG. 70A  is a plan view of a light flux controlling member of the illumination device according to Embodiment 19,  FIG. 70B  is a cross-sectional view taken along line O-O of  FIG. 70A , and  FIG. 70C  is a bottom view of the light flux controlling member of the illumination device according to Embodiment 19; 
           [0089]      FIG. 71  is a graph illustrating the light distribution characteristics of the illumination device according to Embodiment 19 when optical reflectance of the transflective film is 50%; 
           [0090]      FIG. 72  is a graph illustrating the light distribution characteristics of the illumination device according to Embodiment 19 when optical reflectance of the transflective film is 60%; 
           [0091]      FIG. 73  is a graph illustrating the light distribution characteristics of the illumination device according to Embodiment 19 when optical reflectance of the transflective film is 70%; and 
           [0092]      FIG. 74  is a graph illustrating the light distribution characteristics of the illumination device according to Embodiment 19 when optical reflectance of the transflective film is 80%. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0093]    Now, embodiments of the invention will be described in detail with reference to the accompanying drawings. In the following description, an illumination device (Embodiments 1 to 12) which can be used instead of an incandescent lamp, an illumination device (Embodiments 13 to 17) which can be used instead of a straight tube fluorescent lamp, and an illumination device (Embodiments 18 and 19) which can be used instead of a circular fluorescent lamp will be described as representative examples of the invention. 
         [0094]    (Embodiment 1) 
         [0095]    Configuration of Illumination Device 
         [0096]      FIG. 2  is a diagram illustrating illumination device  1  according to Embodiment 1 of the invention.  FIG. 2A  is a plan view of illumination device  1 ,  FIG. 2B  is a front view of illumination device  1 ,  FIG. 2C  is a cross-sectional view taken along line B-B of  FIG. 2A , and  FIG. 2D  is a bottom view of illumination device  1 . Illumination device  1  can be used instead of an incandescent lamp. 
         [0097]    As shown in  FIG. 2 , illumination device  1  includes light emitting element  2 , light flux controlling member  3 , and board  4 . Illumination device  1  emits light from light emitting element  2  (for example, an LED or an LED sealed by a sealing member) through light flux controlling member  3 . Light emitting element  2  and light flux controlling member  3  correspond to each other in a one-to-one manner. One end (opening end)  5  of light flux controlling member  3  is fixed to board  4  on which light emitting element  2  is mounted with an adhesive. Central axis L 1  of light flux controlling member  3  is located coaxial with optical axis L of light emitting element  2 . Here, “optical axis L of light emitting element  2 ” means the traveling direction of light at the center of a three-dimensional light flux emitted from light emitting element  2 . 
         [0098]    Configuration of Light Flux Controlling Member 
         [0099]      FIG. 3A  is a plan view of light flux controlling member  3 ,  FIG. 3B  is a front view of light flux controlling member  3 ,  FIG. 3C  is a cross-sectional view taken along line C-C of  FIG. 3A , and  FIG. 3D  is a bottom view of light flux controlling member  3 . 
         [0100]    Light flux controlling member  3  is formed of a transparent resin material such as polymethylmethacrylate (PMMA), polycarbonate (PC), or epoxy resin (EP) or a transparent glass. 
         [0101]    Light flux controlling member  3  is formed to have a circular planar shape. Central axis L 1  of light flux controlling member  3  is matched with the drawing center of a planar shape. Light flux controlling member  3  includes cylindrical sidewall (supporting part: transmissive part)  6  of which one end  5  is fixed to board  4  and cap (light flux controlling member body: transflective part)  8  fixed to the other end  7  of sidewall  6 . 
         [0102]    As shown in  FIG. 3C , inner surface  10  of cap  8  is a concave surface (aspheric surface) in which central part  11  located on central axis L 1  is located closer to one end  5  of sidewall  6  than outer circumference  12  is. Therefore, when light flux controlling member  3  is fixed onto board  4 , central part  11  is located at a position closer to light emitting element  2  than outer circumference  12  is (see  FIG. 2C ). Inner surface  10  of cap  8  has a curved shape in which the inclination becomes slower from central part  11  of cap  8  to outer circumference  12  (to the outside in a radius direction). Inner surface  10  of cap  8  has an aspheric shape in which a point having an inclination angle of 0 appears at a position located between central part  11  and outer circumference  12  and closer to outer circumference  12 . Transflective film  13  formed by stacking TiO 2  and SiO 2  layer on the surface thereof by deposition is formed on inner surface  10  of cap  8 . The entire area of inner surface  10  of the cap is covered with transflective film  13 . Transflective film  13  reflects a part of light from light emitting element  2  toward sidewall  6  and causes the other part of light from light emitting element  2  to enter the inside of cap  8  (see  FIG. 4 ). The thickness of transflective film  13  is adjusted depending on requested optical reflectance. As the thickness of transflective film  13  becomes larger, the optical reflectance becomes higher. 
         [0103]    Outer surface  14  of cap  8  has a double-sided relation with inner surface  10  and is formed so that the thickness along central axis L 1  of cap  8  is constant from central part  11  to outer circumference  12 . Outer surface  14  of cap  8  extensively emit light entering the inside of cap  8  through transflective film  13  to the outside (see  FIG. 4B ). 
         [0104]    Sidewall  6  is disposed along central axis L 1  to surround central axis L 1 . Sidewall  6  is located between the outer rim of cap  8  and board  4 . Sidewall  6  is formed to have a constant inner diameter from one end  5  to the other end  7  and to have a constant thickness. Sidewall  6  extensively emits light, which is reflected by transflective film  13  of cap  8  and arrives thereat out of light emitted from light emitting element  2 , and light, which directly arrives thereat out of light emitted from light emitting element  2 , to the outside (see  FIG. 4A ). 
         [0105]      FIGS. 5 to 8  are graphs illustrating the light distribution characteristics of illumination device  1 .  FIG. 5  is a graph illustrating the light distribution characteristics of illumination device  1  when the optical reflectance of transflective film  13  is 55%.  FIG. 6  is a graph illustrating the light distribution characteristics of illumination device  1  when the optical reflectance of transflective film  13  is 65%.  FIG. 7  is a graph illustrating the light distribution characteristics of illumination device  1  when the optical reflectance of transflective film  13  is 75%.  FIG. 8  is a graph illustrating the light distribution characteristics of illumination device  1  when the optical reflectance of transflective film  13  is 85%. 
         [0106]    The light distribution characteristics are measured in the following order. As shown in  FIG. 9 , illuminometer  16  is disposed at a position (reference position 0°) apart by a predetermined distance along optical axis L from emission center of light emitting element  2 . Illuminometer  16  measures illuminance while rotating by 180° at intervals of 5° in a clockwise direction (in the +θ direction) about emission center  15  of light emitting element  2 , and measures illuminance while rotating by 180° at intervals of 5° in a counterclockwise direction (in the −θ direction). Relative illuminance values (dimensionless values) when the maximum illuminance of the measured illuminance values is set to  1  are smoothly connected to form a curve, whereby the graphs of  FIGS. 5 to 8  are created. 
         [0107]    As shown in  FIGS. 5 to 8 , as the reflectance of transflective film  13  formed on inner surface  10  of cap  8  of light flux controlling member  3  becomes larger, the illuminance in the horizontal direction (in the ±90° direction) and in the backward direction (+90°&lt;θ&lt;+180° and −90°&lt;θ&lt;−180°) becomes higher. In the light distribution characteristics shown in  FIGS. 5 to 7 , the illuminance in the forward direction)(θ=0°) is the largest. On the contrary, in the light distribution characteristics shown in  FIG. 8 , the illuminance in the horizontal direction (in the ±90° direction) is larger than the illuminance in the forward direction) (θ=0°, and is different from the illuminance balance indicated by the light distribution characteristics shown in  FIGS. 5 to 7 . 
         [0108]    In this way, the light distribution characteristics of illumination device  1  differ depending on the reflectance of transflective film  13  formed in inner surface  10  of cap  8  of light flux controlling member  3 . Accordingly, the reflectance of transflective film  13  is selected depending on the usage of illumination device  1 , and transflective film  13  is deposited on inner surface  10  of cap  8  of light flux controlling member  3  so as to achieve the selected reflectance. 
         [0109]    Here, when the reflectance of transflective film  13  of light flux controlling member  3  is 75%, the light distribution characteristics (the light distribution characteristics shown in  FIG. 7 ) of illumination device  1  including light flux controlling member  3  according to Embodiment 1 is closest to the light distribution characteristics of an incandescent lamp. Accordingly, when illumination device  1  having light flux controlling member  3  according to Embodiment 1 is used as indoor lighting instead of an incandescent lamp, it is preferable that the reflectance of transflective film  13  of light flux controlling member  3  be set to 75%. 
         [0110]    Advantages 
         [0111]    Light flux controlling member  3  according to Embodiment 1 reflects a part of light from light emitting element  2  by the use of transflective film  13  formed on inner surface  10  of cap  8 , and emits the other (light not reflected by transflective film  13 ) of light from light emitting element  2  from outer surface  14  of cap  8  by the use of transflective film  13  formed on inner surface  10  of cap  8 . In this way, since light flux controlling member  3  according to Embodiment 1 does not reflect light from light emitting element  2  by total reflection of cap  8 , the light emitted from cap  8  does not cause color separation and thus degradation in quality of illumination due to the irregularity in color is not caused. 
         [0112]    Illumination device  1  according to Embodiment 1 emits light from light emitting element  2 , which is reflected by transflective film  13  formed on inner surface  10  of cap  8  and arrives at inner surface  17  of sidewall  6 , and light, which directly arrives at inner surface  17  of sidewall  6  from light emitting element  2 , from outer surface  18  of sidewall  6 . Illumination device  1  according to Embodiment 1 emits light from light emitting element  2 , which is transmitted by transflective film  13  formed on inner surface  10  of cap  8  and is incident on cap  8 , from outer surface  14  of cap  8 . In this way, since light flux controlling member  3  according to Embodiment 1 can satisfactorily distribute light in the horizontal direction and the backward direction in addition to the forward direction, it is possible to make the light distribution characteristics close to those of an incandescent lamp. 
         [0113]    Illumination device  1  according to Embodiment 1 does not cause the degradation in quality of illumination due to the irregularity in color and thus can be used for indoor illumination instead of an incandescent lamp. Illumination device  1  according to Embodiment 1 can reduce power consumption in comparison with an incandescent lamp and can be used for a longer time than the incandescent lamp. 
         [0114]    Outer surface  18  of sidewall  6  of light flux controlling member  3  and/or outer surface  14  of cap  8  may be formed of a light diffusion surface (a surface subjected to a light diffusion process such as a source roughening process). By employing this configuration, it is possible to extensively diffuse light emitted from sidewall  6  and/or cap  8 . 
         [0115]    Light flux controlling member  3  may be formed of a material having a light diffusion function. By employing this configuration, it is possible to scatter light in the inside of light flux controlling member  3  and to extensively diffuse light emitted from sidewall  6  and cap  8 . 
         [0116]    Transflective film  13  may be formed through a method other than a deposition method. For example, transflective film  13  formed in a film shape in advance may be bonded to inner surface  10  of cap  8 . 
         [0117]    Transflective film  13  may not be a multi-layered film of TiO 2  and SiO 2 . For example, transflective film  13  may be a multi-layered dielectric film such as a multi-layered film of ZnO 2  and SiO 2  or a multi-layered film of Ta 2 O 2  and SiO 2 . Transflective film  13  may be a thin metal film of aluminum (Al) or the like from which a necessary amount of transmitted light is obtained. 
         [0118]    The optical reflectance of transflective film  13  may be adjusted by means other than the adjustment of the thickness of transflective film  13 . For example, by forming a reflective area in patterns such as dot shapes or mesh shapes and adjusting the area ratio of the transmissive area and the reflective area, desired optical reflectance may be obtained. The optical reflectance of the reflective area may be adjusted by the use of the thickness. 
         [0119]    The method of fixing light flux controlling member  3  to board  4  is not limited to the fixation using an adhesive. For example, light flux controlling member  3  and board  4  may be fixed using another member such as a case. Light flux controlling member  3  and board  4  may be fixed using welding or a screw fixing mechanism, or the like. 
         [0120]    A part of inner surface  10  of cap  8  of light flux controlling member  3  may be formed in an inclined plane or a plane. 
         [0121]    (Embodiment 2) 
         [0122]      FIG. 10  is a cross-sectional view of illumination device  1  and light flux controlling member  3  according to Embodiment 2 (corresponding to  FIG. 2C ). The same elements as those of illumination device  1  and light flux controlling member  3  according to Embodiment 1 shown in  FIG. 2  will not be described. 
         [0123]    As shown in  FIG. 10 , light flux controlling member  3  according to Embodiment 2 is different from light flux controlling member  3  according to Embodiment 1, in that sidewall  6  and cap  8  are formed of different members, respectively. Sidewall  6  and cap  8  are formed separately. Thereafter, by inserting cap  8  into a ring-like concave portion  20  formed on the upper end of sidewall  6  and fixing them (for example, by bonding or welding), sidewall  6  and cap  8  are formed as a unified body. 
         [0124]    When light flux controlling member  3  according to Embodiment 2 is fabricated, only cap  8  can be put into a deposition processing chamber and transflective film  13  can be formed on inner surface  10  thereof. Accordingly, light flux controlling member  3  according to Embodiment 2 can be fabricated more efficiently than light flux controlling member  3  according to Embodiment 1. When light flux controlling member  3  according to Embodiment 1 is fabricated, preliminary treatment (masking) has to be performed so as not to form transflective film  13  on inner peripheral surface  17  of sidewall  6 . 
         [0125]    As shown in  FIG. 11 , illumination device  1  according to Embodiment 2 exhibits almost the same light distribution characteristics as the light distribution characteristics (see  FIG. 7 ) of illumination device  1  according to Embodiment 1 and it is thus possible to obtain the same advantages as those of illumination device  1  according to Embodiment 1. The reflectance of transflective film  13  formed on inner surface  10  of cap  8  is adjusted to 75%. 
         [0126]    (Embodiment 3) 
         [0127]      FIG. 12  is a cross-sectional view of illumination device  1  and light flux controlling member  3  according to Embodiment 3 (corresponding to  FIG. 2C ). The same elements as those of illumination device  1  and light flux controlling member  3  according to Embodiment 1 shown in  FIG. 2  will not be described. 
         [0128]    As shown in  FIG. 12 , light flux controlling member  3  according to Embodiment 3 is different from light flux controlling member  3  according to Embodiment 1, in that outer surface  14  of cap  8  is a plane perpendicular to optical axis L. 
         [0129]    As shown in  FIG. 13 , illumination device  1  according to Embodiment 3 exhibits almost the same light distribution characteristics as the light distribution characteristics (see  FIG. 7 ) of illumination device  1  according to Embodiment 1, except that the illuminance of the oblique front side increases, and it is thus possible to obtain the same advantages as those of illumination device  1  according to Embodiment 1. The reflectance of transflective film  13  formed on inner surface  10  of cap  8  is adjusted to 75%. 
         [0130]    (Embodiment 4) 
         [0131]      FIG. 14  is a cross-sectional view of illumination device  1  and light flux controlling member  3  according to Embodiment 4 (corresponding to  FIG. 2C ). The same elements as those of illumination device  1  and light flux controlling member  3  according to Embodiment 1 shown in  FIG. 2  will not be described. 
         [0132]    As shown in  FIG. 14 , light flux controlling member  3  according to Embodiment 4 is different from light flux controlling member  3  according to Embodiment 1, in the shape of sidewall  6 . That is, in light flux controlling member  3  according to Embodiment 4, the shape of sidewall  6  is formed in a reversely-tapered shape so that the inner diameter of lower end  5  of sidewall  6  is smaller than the inner diameter in a connecting part (outer circumference  12  of cap  8 ) of sidewall  6  and cap  8 . 
         [0133]    As shown in  FIG. 15 , illumination device  1  according to Embodiment 4 exhibits almost the same light distribution characteristics as the light distribution characteristics (see  FIG. 7 ) of illumination device  1  according to Embodiment 1, except that the illuminance of the oblique front side decreases, and it is thus possible to obtain the same advantages as those of illumination device  1  according to Embodiment 1. The reflectance of transflective film  13  formed on inner surface  10  of cap  8  is adjusted to 75%. 
         [0134]    Light flux controlling member  3  according to Embodiment 4 may be fabricated by fixing sidewall  6  and cap  8  which are separately formed, similarly to light flux controlling member  3  according to Embodiment 2. 
         [0135]    (Embodiment 5) 
         [0136]      FIG. 16  is a cross-sectional view of illumination device  1  and light flux controlling member  3  according to Embodiment 5 (corresponding to  FIG. 2C ). The same elements as those of illumination device  1  and light flux controlling member  3  according to Embodiment 1 shown in  FIG. 2  will not be described. 
         [0137]    As shown in  FIG. 16 , light flux controlling member  3  according to Embodiment 5 is different from light flux controlling member  3  according to Embodiment 1, in that outer peripheral surface  18  of sidewall  6  and outer surface  14  of the cap are configured to form a continuous semi-spherical surface. Inner peripheral surface  17  of sidewall  6  is configured to form a part of a semi-spherical surface coaxial with outer peripheral surface  18  of sidewall  6 . 
         [0138]    As shown in  FIG. 17 , illumination device  1  according to Embodiment 5 exhibits almost the same light distribution characteristics as the light distribution characteristics (see  FIG. 8 ) of illumination device  1  according to Embodiment 1, except that the illuminance of the front side decreases, and it is thus possible to obtain the same advantages as those of illumination device  1  according to Embodiment 1. The reflectance of transflective film  13  formed on inner surface  10  of cap  8  is adjusted to 75%. 
         [0139]    (Embodiment 6) 
         [0140]      FIG. 18  is a cross-sectional view of illumination device  1  and light flux controlling member  3  according to Embodiment 6 (corresponding to  FIG. 2C ). Illumination device  1  and light flux controlling member  3  according to Embodiment 6 are modified examples of illumination device  1  and light flux controlling member  3  according to Embodiment 5. The same elements as those of illumination device  1  and light flux controlling member  3  according to Embodiment 5 shown in  FIG. 16  will not be described. 
         [0141]    As shown in  FIG. 18 , light flux controlling member  3  according to Embodiment 6 is different from light flux controlling member  3  according to Embodiment 5, in that outer surface  14  of cap  8  is a plane intersecting optical axis L at right angle. In this way, by cutting cap  8  with a virtual plane perpendicular to optical axis L and removing the upper part of cap  8 , it is possible to reduce the height of light flux controlling member  3 . 
         [0142]    Illumination device  1  according to Embodiment 6 can achieve the same advantages as those of illumination device  1  according to Embodiment 5. 
         [0143]    (Embodiment 7) 
         [0144]      FIG. 19  is a cross-sectional view of illumination device  1  and light flux controlling member  3  according to Embodiment 7 (corresponding to  FIG. 2C ). Illumination device  1  and light flux controlling member  3  according to Embodiment 7 are modified examples of illumination device  1  and light flux controlling member  3  according to Embodiment 1. Accordingly, the same elements as those of illumination device  1  and light flux controlling member  3  according to Embodiment 1 shown in  FIG. 2  will not be described. 
         [0145]    As shown in  FIG. 19 , light flux controlling member  3  according to Embodiment 7 is different from light flux controlling member  3  according to Embodiment 1, in the shape of sidewall  6 . That is, in light flux controlling member  3  according to Embodiment 4, sidewall  6  has a tapered shape so that the inner diameter of lower end  5  of sidewall  6  is larger than the inner diameter of the connecting portion (outer circumference  12  of cap  8 ) of sidewall  6  and cap  8 . In this way, by forming sidewall  6  in a tapered shape, it is possible to easily release light flux controlling member  3  from a mold when fabricating light flux controlling member  3  through injection molding. 
         [0146]    Illumination device  1  according to Embodiment 7 can achieve the same advantages as those of illumination device  1  according to Embodiment 1. 
         [0147]    (Embodiment 8) 
         [0148]      FIG. 20  is a cross-sectional view of illumination device  1  and light flux controlling member  3  according to Embodiment 8 (corresponding to  FIG. 2C ). Illumination device  1  and light flux controlling member  3  according to Embodiment 8 are modified examples of illumination device  1  and light flux controlling member  3  according to Embodiment 1. Accordingly, the same elements as those of illumination device  1  and light flux controlling member  3  according to Embodiment 1 shown in  FIG. 2  will not be described. 
         [0149]    As shown in  FIG. 20 , light flux controlling member  3  according to Embodiment 8 is different from light flux controlling member  3  according to Embodiment 1, in that sidewall  6  and cap  8  are formed of different members, respectively. Sidewall  6  and cap  8  are formed separately. Thereafter, by inserting cap  8  into a ring-like concave portion  20  formed on the upper end of sidewall  6  and fixing them (for example, by bonding or welding), sidewall  6  and cap  8  are formed as a unified body. Sidewall  6  is a tubular body having an outer cross-sectional shape obtained, for example, by cutting a ball. The inner diameter of lower end  5  of sidewall  6  is smaller than the inner diameter of the connecting portion (outer circumference  12  of cap  8 ) of sidewall  6  and cap  8 . 
         [0150]    Light flux controlling member  3  has cover  21  of which the outer shape is semi-spherical (which is a shape obtained by cutting a hollow ball to a half). Opening end  22  of cover  21  is fixed (for example, bonded or welded) to the other end (upper end)  7  of sidewall  6 . Inner peripheral surface  23  of opening end  22  of cover  21  is fitted to outer peripheral surface  24  of cap  8 . Outer surface  14  of cap  8  is covered with cover  21  with an air layer interposed therebetween. As a result, light flux controlling member  3  has an outer shape obtained by cutting a part of a ball. 
         [0151]    Cover  21  is formed of a light transmitting material, similarly to sidewall  6  and cap  8 . Cover  21  may be formed of a material into which a light scattering material is mixed so as to enhance light diffusing performance. At least one of the outer surface and the inner surface of cover  21  may be roughened to enhance the light diffusing performance. The light diffusing function may not be given to cover  21 . 
         [0152]    As shown in  FIG. 21 , illumination device  1  according to Embodiment 8 exhibits almost the same light distribution characteristics as the light distribution characteristics (see  FIG. 7 ) of illumination device  1  according to Embodiment 1, except that the illuminance of the front side is low and the illuminance in the horizontal direction is high, and it is thus possible to obtain the same advantages as those of illumination device  1  according to Embodiment 1. The reflectance of transflective film  13  formed on inner surface  10  of cap  8  is adjusted to 75%. Sidewall  6  and cover  21  have the same thickness, except for a portion in which both are fixed to each other and the vicinity thereof. 
         [0153]    (Embodiment 9) 
         [0154]      FIG. 22  is a cross-sectional view of illumination device  1  and light flux controlling member  3  according to Embodiment 9 (corresponding to  FIG. 2C ). Illumination device  1  and light flux controlling member  3  according to Embodiment 9 are modified examples of illumination device  1  and light flux controlling member  3  according to Embodiment 8. Accordingly, the same elements as those of illumination device  1  and light flux controlling member  3  according to Embodiment 8 shown in  FIG. 20  will not be described. 
         [0155]    As shown in  FIG. 22 , light flux controlling member  3  according to Embodiment 9 is different from light flux controlling member  3  according to Embodiment 8, in that the curvature of cover  21  is smaller. In this way, by reducing the curvature of cover  21 , it is possible to reduce the height of light flux controlling member  3 . 
         [0156]    As shown in  FIG. 23 , illumination device  1  according to Embodiment 9 exhibits almost the same light distribution characteristics as the light distribution characteristics (see  FIG. 7 ) of illumination device  1  according to Embodiment 1, except that the illuminance in from the horizontal direction to the forward direction is almost constant, and it is thus possible to obtain the same advantages as those of illumination device  1  according to Embodiment 1. The reflectance of transflective film  13  formed on inner surface  10  of cap  8  is adjusted to 75%. 
         [0157]    (Embodiment 10) 
         [0158]      FIG. 24A  is a cross-sectional view of illumination device  1  and light flux controlling member  3  according to Embodiment 10 (corresponding to  FIG. 2C ).  FIG. 24B  is a plan view of board  4  on which plural light emitting elements  2  are mounted. 
         [0159]    Illumination device  1  and light flux controlling member  3  according to Embodiment 10 are modified examples of illumination device  1  and light flux controlling member  3  according to Embodiment 8. Accordingly, the same elements as those of illumination device  1  and light flux controlling member according to Embodiment 8 shown in  FIG. 20  will not be described. 
         [0160]    As shown in  FIGS. 24A and 24B , illumination device  1  according to Embodiment 10 is different from illumination device  1  according to Embodiment 8, in that plural light emitting elements  2  are mounted on board  4 . Light flux controlling member  3  according to Embodiment 10 is the same as light flux controlling member  3  according to Embodiment 8. 
         [0161]    As shown in  FIG. 24B , plural light emitting elements  2  are arranged at equal intervals (total eight light emitting elements are arranged at intervals of 45°)on the same circle  25  on board  4  of illumination device  1  according to Embodiment 10. Center L of light fluxes of plural light emitting elements  2  is the center of an entire emitted light flux in which three-dimensional emitted light fluxes of light emitting elements  2 . The position of center L of light fluxes of plural light emitting elements  2  corresponds to the position (the central position of a light flux) of optical axis L of single light-emitting element  2  of illumination device  1  according to Embodiment 8. Center L of the light fluxes of plural light emitting elements  2  is matched with central axis L 1  of light flux controlling member  3 . 
         [0162]    As shown in  FIG. 25 , the illuminance in from the horizontal direction to the forward direction is almost constant and the light distribution characteristics of illumination device  1  according to Embodiment 10 is closer to the light distribution characteristics of an incandescent lamp, compared with the light distribution characteristics (see  FIG. 21 ) of illumination device  1  according to Embodiment 8. The reflectance of transflective film  13  formed on inner surface  10  of cap  8  is adjusted to 75%. 
         [0163]    (Embodiment 11) 
         [0164]      FIG. 26A  is a cross-sectional view of illumination device  1  and light flux controlling member  3  according to Embodiment 11 (corresponding to  FIG. 2C ).  FIG. 26B  is a plan view of board on which plural light emitting elements  2  are mounted.  FIG. 27A  is a front view of light flux controlling member  3 ,  FIG. 27B  is a plan view of light flux controlling member  3 ,  FIG. 27C  is a bottom view of light flux controlling member  3 , and  FIG. 27D  is a cross-sectional view taken along line D-D of  FIG. 27B . Illumination device  1  and light flux controlling member  3  according to Embodiment 11 are modified examples of illumination device  1  and light flux controlling member  3  according to Embodiment 10. Accordingly, the same elements as those of illumination device  1  and light flux controlling member  3  according to Embodiment 10 shown in  FIG. 24  will not be described. 
         [0165]    As shown in  FIGS. 26A and 27 , light flux controlling member  3  according to Embodiment 11 includes light flux controlling member body  26  and supporting part  27  extending downward (along central axis L 1 ) from the center of inner surface  10  (inner surface  10  opposed to light emitting element  2 ) of light flux controlling member body  26 . Light flux controlling member  3  according to Embodiment 11 does not have a configuration corresponding to sidewall  6  of light flux controlling member  3  according to Embodiment 1 or Embodiment 10 (see  FIGS. 2 and 24 ). Therefore, in illumination device  1  according to Embodiment 11, a space between the outer peripheral part of light flux controlling member body  26  and the outer peripheral part of board  4  serves as a transmitting part externally emitting light reflected by light flux controlling member body  26  (transflective part) and light directly arriving from light emitting element  2 . 
         [0166]    Supporting part  27  has a cylindrical shape, and end face (bottom end face)  27   a  thereof is fixed to board  4  (for example, by bonding, screwing, or pressing). Supporting part  27  supports light flux controlling member body  26  on board  4  so that central axis L 1  of light flux controlling member  3  is matched with center L of the light fluxes of plural light emitting elements  2 . 
         [0167]    Light flux controlling member body  26  has the same shape as cap  8  of light flux controlling member  3  according to Embodiment 1 (see  FIGS. 2 and 3 ), except that it is formed as a unified body with supporting part  27 . Transflective film  13  is formed on inner surface  10  of light flux controlling member body  26  except for a portion in which supporting part  27  is formed, similarly to cap  8  of light flux controlling member  3  according to Embodiment 1. Outer surface  14  of light flux controlling member body  26  has a double-sided relation with inner surface  10 , and is formed similarly to outer surface  14  of cap  8  of light flux controlling member  3  according to Embodiment 1. 
         [0168]    As shown in  FIG. 26A , illumination device  1  according to Embodiment 11 includes cover  21  of a shape obtained by cutting a part of a hollow sphere. Opening end  22  of cover  21  is fixed to the outer peripheral part of disk-like board  4 . As a result, plural light emitting elements  2  and light flux controlling member  3  are received in space  28  sealed by cover  21  and board  4 . Gap  30  is present between the outer peripheral part of light flux controlling member body  26  and cover  21 . Supporting part  27  is fixed directly to board  4 . 
         [0169]    Illumination device  1  according to Embodiment 11 is smaller in the number of parts than illumination device  1  according to Embodiment 10. Accordingly, illumination device  1  according to Embodiment 11 can be fabricated through a smaller number of assembly steps in comparison with illumination device  1  according to Embodiment 10, thereby enhancing production efficiency. 
         [0170]    As shown in  FIG. 28 , illumination device  1  according to Embodiment 11 exhibits almost the same light distribution characteristics as the light distribution characteristics (see  FIG. 25 ) of illumination device  1  according to Embodiment 10 and it is thus possible to obtain the same advantages as those of illumination device  1  according to Embodiment 1. The reflectance of transflective film  13  formed on inner surface  10  of light flux controlling member body  26  is adjusted to 75%. 
         [0171]    (Embodiment 12) 
         [0172]      FIG. 29  is a cross-sectional view of illumination device  1  and light flux controlling member  3  according to Embodiment 12. Illumination device  1  and light flux controlling member  3  according to Embodiment 12 are modified examples of illumination device  1  and light flux controlling member  3  according to Embodiment 11. Accordingly, the same elements as those of illumination device  1  and light flux controlling member  3  according to Embodiment 11 shown in  FIGS. 26 and 27  will not be described. 
         [0173]    As shown in  FIG. 29 , illumination device  1  according to Embodiment 12 includes plural “light emitting element-light flux controlling member” units  31  including plural light emitting elements  2  and light flux controlling member  3  included in illumination device  1  according to Embodiment 11. Plural “light emitting element-light flux controlling member” units  31  are arranged on single board  32 . Opening end  34  of cover  33  is fixed to the outer rim of board  32 . As a result, plural “light emitting element-light flux controlling member” units  31  are received in space  35  sealed by board  32  and cover  33 . 
         [0174]    The surface of board  32  on which plural light emitting elements  2  are mounted may be coated with a light reflecting member (not shown) having an excellent light reflecting function. A light reflecting member (not shown) having an excellent light reflecting function may be disposed on board  32  on which plural light emitting elements  2  are mounted. 
         [0175]    The cross-section taken along line E-E shown in  FIG. 29  is the same as shown in  FIG. 26A . The planar shape of illumination device  1  according to Embodiment 12 can be set to an optimal shape such as a circular shape, a rectangular shape, and a hexagonal shape, depending on the usages. 
         [0176]    The light distribution characteristics of illumination device  1  according to Embodiment 12 are close to the light distribution characteristics of an incandescent lamp. 
         [0177]    Illumination device  1  according to Embodiment 12 can emit high-quality illumination light without irregularity in color. 
         [0178]    (Embodiment 13 ) 
         [0179]    Configuration of Illumination Device 
         [0180]      FIG. 30A  is a perspective view illustrating the appearance of illumination device  1  according to Embodiment 13 and  FIG. 30B  is a transparent perspective view of illumination device  1 . Illumination device  1  can be used instead of a straight tube fluorescent lamp. 
         [0181]    As shown in  FIGS. 30A and 30B , illumination device  1  includes light emitting elements  2 , light flux control member  3 , and board  4 . In the description of Embodiments 13 to 17, the long-axis direction of board  4  is defined as a first direction and the short-axis direction of board  4  is defined as a second direction. The first direction and the second direction are perpendicular to each other. 
         [0182]      FIG. 31A  is a cross-sectional view (transverse cross-section) in the second direction of illumination device  1 .  FIG. 31B  is a plan view of board  4  on which plural light emitting elements  2  are mounted. 
         [0183]    As shown in  FIGS. 31A and 31B , illumination device  1  emits light from plural light emitting elements  2  (for example, LEDs or LEDs sealed by a sealing member) arranged in a line in the first direction through light flux controlling member  3 . One end  5  of light flux controlling member  3  is fixed to board  4  on which plural light emitting elements  2  are mounted with an adhesive. Central line L 1  (see  FIGS. 31A and 32A ) of light flux controlling member  3  is located in straight line L 2  (see  FIG. 31B ) connecting the centers of light emitting elements  2 . 
         [0184]    Configuration of Light Flux Controlling Member 
         [0185]      FIG. 32A  is a bottom view of light flux controlling member  3  and  FIG. 32B  is a plan view of light flux controlling member  3 .  FIG. 32C  is a cross-sectional view (a cross-sectional view in the second direction; corresponding to  FIG. 31A ) taken along line F-F of  FIG. 32B  and  FIG. 32D  is a cross-sectional view (a cross-sectional view in the first direction) taken along line G-G of  FIG. 32B . 
         [0186]    Light flux controlling member  3  is formed of a transparent resin material such as polymethylmethacrylate (PMMA), polycarbonate (PC), or epoxy resin (EP) or a transparent glass. 
         [0187]    Light flux controlling member  3  is formed to have a rectangular planar shape. Light flux controlling member  3  includes two sidewalls (supporting parts: transmissive parts)  6  of which one end  5  is fixed to board  4  and cap (light flux controlling member body: transflective part)  8  fixed to the other ends  7  of sidewall  6  (see  FIG. 31A ). Inner surface  10  and outer surface  14  of cap  8  does not have curvature in the first direction. That is, inner surface  10  and outer surface  14  of cap  8  do not affect the light distribution characteristics of emitted light of light emitting elements  2  in the first direction. On the other hand, inner surface  10  and outer surface  14  of cap  8  have curvature in the second direction. Therefore, inner surface  10  of cap  8  can change the light distribution characteristics of emitted light of light emitting elements  2  to desired light distribution characteristics in the second direction by controlling the reflecting direction of light from light emitting elements  2 . 
         [0188]    As shown in  FIG. 31A , inner surface  10  of cap  8  is a concave surface in which central part  11  located on central axis L 1  is located closer to one end  5  of sidewall  6  than outer circumference  12  in the second direction is. Therefore, when light flux controlling member  3  is fixed onto board  4 , central part  11  is located at a position closer to light emitting element  2  than outer circumference  12  is. Inner surface  10  of cap  8  has a curved shape in which the inclination becomes slower from central part  11  of cap  8  to outer circumference  12 . Inner surface  10  of cap  8  has an aspheric shape in which a point having an inclination angle of  0  appears at a position located between central part  11  and outer circumference  12  and closer to outer circumference  12 . Transflective film  13  formed by stacking TiO 2  and SiO 2  layer on the surface thereof by deposition is formed on inner surface  10  of cap  8 . The entire area of inner surface  10  of cap  8  is covered with transflective film  13 . Transflective film  13  reflects a part of light from light emitting element  2  toward sidewall  6  and causes the other part of light from light emitting element  2  to enter the inside of cap  8  (see 
         [0189]      FIG. 33 ). The thickness of transflective film  13  is adjusted depending on requested optical reflectance. As the thickness of transflective film  13  becomes larger, the optical reflectance becomes higher. 
         [0190]    Outer surface  14  of cap  8  has a double-sided relation with inner surface  10  and is formed so that the thickness along central axis L 1  of cap  8  is constant from central part  11  to outer circumference  12 . Outer surface  14  of cap  8  extensively emit light entering the inside of cap  8  through transflective film  13  to the outside (see  FIG. 33B ). 
         [0191]    Two sidewalls  6  are disposed to oppose each other so that the gap between one ends  5  is smaller than the gap between the other ends  7 . Sidewalls  6  are located between the outer rim of cap  8  and board  4 . The thickness of sidewalls  6  is constant from one end  5  to the other end  7 . Sidewalls  6  extensively emit light reflected by transflective film  13  of cap  8  and arriving thereat and light directly arriving thereat out of light emitted from light emitting elements  2  out of light emitted from light emitting element  2  to the outside (see  FIG. 33A ). 
         [0192]      FIGS. 34 to 37  are graphs illustrating the light distribution characteristics of illumination device  1 .  FIG. 34  is a graph illustrating the light distribution characteristics of illumination device  1  when the optical reflectance of transflective film  13  is 50%.  FIG. 35  is a graph illustrating the light distribution characteristics of illumination device  1  when the optical reflectance of transflective film  13  is 60%.  FIG. 36  is a graph illustrating the light distribution characteristics of illumination device  1  when the optical reflectance of transflective film  13  is 70%.  FIG. 37  is a graph illustrating the light distribution characteristics of illumination device  1  when the optical reflectance of transflective film  13  is 80%. 
         [0193]    The light distribution characteristics are measured in the following order. As shown in  FIG. 38 , illuminometer  16  is disposed at a position (reference position 0°)apart by a predetermined distance in the perpendicular direction from center  15  (see  FIG. 31B ) of board  4 . Illuminometer  16  measures illuminance while rotating by 180° at intervals of 5° in a clockwise direction (in the +θ direction) about center  15  of board  4 , and measures illuminance while rotating by 180° at intervals of 5° in a counterclockwise direction (in the −θ direction). Relative illuminance values (dimensionless values) when the maximum illuminance value of the measured illuminance values is set to  1  are smoothly connected to form a curve, whereby the graphs of  FIGS. 34 to 37  are created. The light distribution characteristics of illumination device  1  are measured in two directions of the first direction and the second direction. In  FIGS. 34 to 37 , the measurement result in the first direction (the long-axis direction) is indicated by curve A and the measurement result in the second direction (the short-axis direction) is indicated by curve B. 
         [0194]    As indicated by curve B in  FIGS. 34 to 37 , as the reflectance of transflective film  13  formed on inner surface  10  of cap  8  of light flux controlling member  3  becomes larger, the illuminance in the horizontal direction (in the ±90° direction) and in the backward direction (+90°&lt;θ&lt;+180° and) −90°&lt;θ&lt;−180°) becomes higher. In the light distribution characteristics shown in  FIGS. 34 and 35 , the illuminance in the forward direction) (θ=0°) is the largest. On the contrary, in the light distribution characteristics shown in  FIG. 36 and 37 , the illuminance in the horizontal direction (in the ±90° direction) is larger than the illuminance in the forward direction) (θ=0°), and is different from the illuminance balance indicated by the light distribution characteristics shown in  FIGS. 34 and 35 . 
         [0195]    In this way, the light distribution characteristics of illumination device  1  differ depending on the reflectance of transflective film  13  formed in inner surface  10  of cap  8  of light flux controlling member  3 . Accordingly, the reflectance of transflective film  13  is selected depending on the usage of illumination device  1 , and transflective film  13  is deposited on inner surface  10  of cap  8  of light flux controlling member  3  so as to achieve the selected reflectance. 
         [0196]    Here, when the reflectance of transflective film  13  of light flux controlling member  3  is 60%, the light distribution characteristics (the light distribution characteristics shown in  FIG. 35 ) of illumination device  1  including light flux controlling member  3  according to Embodiment 13 is closest to the light distribution characteristics of a fluorescent lamp. Accordingly, when illumination device  1  having light flux controlling member  3  according to Embodiment 13 is used as indoor lighting instead of a fluorescent lamp, it is preferable that the reflectance of transflective film  13  of light flux controlling member  3  be set to 60%. 
         [0197]    Advantages 
         [0198]    Light flux controlling member  3  according to Embodiment 13 reflects a part of light from light emitting element  2  by the use of transflective film  13  formed on inner surface  10  of cap  8 , and emits the other (light not reflected by transflective film  13 ) of light from light emitting element  2  from outer surface  14  of cap  8  by the use of transflective film  13  formed on inner surface  10  of cap  8 . In this way, since light flux controlling member  3  according to Embodiment 13 does not reflect light from light emitting element  2  by total reflection of cap  8 , the light emitted from cap  8  does not cause color separation and thus degradation in quality of illumination due to the irregularity in color is not caused. 
         [0199]    Illumination device  1  according to Embodiment 13 emits light from light emitting element  2 , which is reflected by transflective film  13  formed on inner surface  10  of cap  8  and arrives at inner surface  17  of sidewall  6 , and light, which directly arrives at inner surface  17  of sidewall  6  from light emitting element  2 , from outer surface  18  of sidewall  6 . Illumination device  1  according to Embodiment 13 emits light from light emitting element  2 , which is transmitted by transflective film  13  formed on inner surface  10  of cap  8  and is incident on cap  8 , from outer surface  14  of cap  8 . In this way, since light flux controlling member  3  according to Embodiment 13 can satisfactorily distribute light in the horizontal direction and the backward direction in addition to the forward direction, it is possible to make the light distribution characteristics close to those of a fluorescent lamp. 
         [0200]    Illumination device  1  according to Embodiment 13 does not cause the degradation in quality of illumination due to the irregularity in color and thus can be used for indoor illumination instead of a fluorescent lamp. Illumination device  1  according to Embodiment 13 can reduce power consumption in comparison with a fluorescent lamp and can be used for a longer time than the fluorescent lamp. 
         [0201]    Outer surface  18  of sidewall  6  of light flux controlling member  3  and/or outer surface  14  of cap  8  may be formed of a light diffusion surface (a surface subjected to a light diffusion process such as a surface roughening process). By employing this configuration, it is possible to extensively diffuse light emitted from sidewall  6  and/or cap  8 . 
         [0202]    Light flux controlling member  3  may be formed of a material having a light diffusion function. By employing this configuration, it is possible to scatter light in the inside of light flux controlling member  3  and to extensively diffuse light emitted from sidewall  6  and cap  8 . 
         [0203]    Transflective film  13  may be formed through a method other than a deposition method. For example, transflective film  13  formed in a film shape in advance may be bonded to inner surface  10  of cap  8 . 
         [0204]    Transflective film  13  may not be a multi-layered film of TiO 2  and SiO 2 . For example, transflective film  13  may be a multi-layered dielectric film such as a multi-layered film of ZnO 2  and SiO 2  or a multi-layered film of Ta 2 O 2  and SiO 2 . Transflective film  13  may be a thin metal film of aluminum (Al) or the like from which a necessary amount of transmitted light is obtained. 
         [0205]    The optical reflectance of transflective film  13  may be adjusted by means other than the adjustment of the thickness of transflective film  13 . For example, by forming a reflective area in patterns such as dot shapes or mesh shapes and adjusting the area ratio of the transmissive area and the reflective area, desired optical reflectance may be obtained. The optical reflectance of the reflective area may be adjusted by the use of the thickness. 
         [0206]    The method of fixing light flux controlling member  3  to board  4  is not limited to the fixation using an adhesive. For example, light flux controlling member  3  and board  4  may be fixed using another member such as a case. Light flux controlling member  3  and board  4  may be fixed using welding or a screw fixing mechanism, or the like. 
         [0207]    A part of inner surface  10  of cap  8  of light flux controlling member  3  may be formed in an inclined plane or a plane. 
         [0208]    (Embodiment 14) 
         [0209]      FIG. 39A  is a cross-sectional view (transverse cross-section) of illumination device  1  according to Embodiment 14 taken along the second direction.  FIG. 39B  is a plan view of board  4  on which plural light emitting elements  2  are mounted.  FIG. 40A  is a bottom view of light flux controlling member  3  according to Embodiment 14 and  FIG. 40B  is a plan view of light flux controlling member  3  according to Embodiment 14.  FIG. 40C  is a cross-sectional view (cross-sectional view in the second direction; corresponding to  FIG. 39A ) taken along line H-H of  FIG. 40B  and  FIG. 40D  is a cross-sectional view (cross-sectional view in the first direction) taken along line I-I of  FIG. 40B . The same elements as those of illumination device  1  and light flux controlling member  3  according to Embodiment  13  shown in  FIGS. 30 to 32  will not be described. 
         [0210]    As shown in  FIGS. 39A and 39B , illumination device  1  according to Embodiment 14 emits light from plural light emitting elements  2 , which are arranged in two lines in the first direction, through light flux controlling member  3 . Central line L 1  (see  FIGS. 39A and 40A ) of light flux controlling member  3  is located on straight line L 2  (see  FIG. 39B ) connecting the centers of two light emitting elements  2  arranged in parallel. Light flux controlling member  3  is the same as light flux controlling member  3  according to Embodiment 13. 
         [0211]      FIGS. 41 to 44  are graphs illustrating the light distribution characteristics of illumination device  1  according to Embodiment 14.  FIG. 41  is a graph illustrating the light distribution characteristics of illumination device  1  when the optical reflectance of transflective film  13  is 50%.  FIG. 42  is a graph illustrating the light distribution characteristics of illumination device  1  when the optical reflectance of transflective film  13  is 60%.  FIG. 43  is a graph illustrating the light distribution characteristics of illumination device  1  when the optical reflectance of transflective film  13  is 70%.  FIG. 44  is a graph illustrating the light distribution characteristics of illumination device  1  when the optical reflectance of transflective film  13  is 80%. 
         [0212]    As indicated by curve B in  FIGS. 41 to 44 , illumination device  1  according to Embodiment 14 exhibits almost the same light distribution characteristics as the light distribution characteristics (see  FIGS. 34 to 37 ) of illumination device  1  according to Embodiment 13 and it is thus possible to obtain the same advantages as those of illumination device  1  according to Embodiment 13. 
         [0213]    (Embodiment 15 5 ) 
         [0214]      FIG. 45A  is a cross-sectional view (transverse cross-section) of illumination device  1  according to Embodiment 15 taken along the second direction.  FIG. 45B  is a plan view of board  4  on which plural light emitting elements  2  are mounted.  FIG. 46A  is a bottom view of light flux controlling member  3  of illumination device  1  according to Embodiment 15 and  FIG. 46B  is a plan view of light flux controlling member  3  of illumination device  1  according to Embodiment 15.  FIG. 46C  is a cross-sectional view (cross-sectional view in the second direction; corresponding to  FIG. 45A ) taken along line J-J of  FIG. 46B  and  FIG. 46D  is a cross-sectional view (cross-sectional view in the first direction) taken along line K-K of  FIG. 46B . 
         [0215]    The same elements as those of illumination device  1  and light flux controlling member  3  according to Embodiment 13 shown in  FIGS. 30 to 32  will not be described. 
         [0216]    As shown in  FIGS. 45A and 46 , light flux controlling member  3  includes light flux controlling member body  26  and supporting part  27  extending downward (along central axis L 1 ) from the center of inner surface  10  (inner surface  10  opposed to light emitting element  2 ) of light flux controlling member body  26 . Light flux controlling member  3  according to Embodiment 15 does not have a configuration corresponding to sidewall  6  of light flux controlling member  3  according to Embodiment 13 (see  FIGS. 31A and 45A ). Therefore, in illumination device  1  according to Embodiment 15, a space between the outer peripheral part of light flux controlling member body  26  and the outer peripheral part of board  4  serves as a transmitting part externally emitting light reflected by light flux controlling member body  26  (transflective part) and light directly arriving from light emitting element  2 . 
         [0217]    As shown in  FIGS. 45A and 46 , supporting part  27  of light flux controlling member  3  has a square column shape, and supports light flux controlling member body  26  on board  4 . End face (bottom end face)  27   a  of supporting part  27  of light flux controlling member  3  is fixed to board  4  (for example, by bonding, screwing, or pressing). Central line L 1  (see  FIGS. 45A and 46A ) of light flux controlling member  3  is located on straight line L 2  (see  FIG. 45B ) connecting the centers of two light emitting elements  2  arranged in parallel. 
         [0218]    Light flux controlling member body  26  has the same shape as cap  8  of light flux controlling member  3  according to Embodiment 13 (see  FIGS. 31A and 45A ), except that it is formed as a unified body with supporting part  27  at the center of inner surface  10 . Inner surface  10  and outer surface  14  of light flux controlling member body  26  does not have curvature in the first direction. That is, inner surface  10  and outer surface  14  of light flux controlling member body  26  do not affect the light distribution characteristics of emitted light of light emitting elements  2  in the first direction. On the other hand, inner surface  10  and outer surface  14  of light flux controlling member body  26  have curvature in the second direction. Therefore, inner surface  10  of light flux controlling member body  26  can change the light distribution characteristics of emitted light of light emitting elements  2  to desired light distribution characteristics in the second direction by controlling the reflecting direction of light from light emitting elements  2 . 
         [0219]    Transflective film  13  is formed on inner surface  10  of light flux controlling member body  26  except for a portion in which supporting part  27  is formed, similarly to cap  8  of light flux controlling member  3  according to Embodiment 13. Outer surface  14  of light flux controlling member body  26  has a double-sided relation with inner surface  10 , and is formed similarly to outer surface  14  of cap  8  of light flux controlling member  3  according to Embodiment 13. 
         [0220]    As shown in  FIG. 45A , in illumination device  1  according to Embodiment 15, opening end  22  of cover  21  having a D-shaped cross-section is fixed to the outer peripheral part of board  4 , and plural light emitting elements  2  and light flux controlling member  3  are received in the space between cover  21  and board  4 . 
         [0221]      FIGS. 47 to 50  are graphs illustrating the light distribution characteristics of illumination device  1  according to Embodiment 15.  FIG. 47  is a graph illustrating the light distribution characteristics of illumination device  1  when the optical reflectance of transflective film  13  is 50%.  FIG. 48  is a graph illustrating the light distribution characteristics of illumination device  1  when the optical reflectance of transflective film  13  is 60%.  FIG. 49  is a graph illustrating the light distribution characteristics of illumination device  1  when the optical reflectance of transflective film  13  is 70%.  FIG. 50  is a graph illustrating the light distribution characteristics of illumination device  1  when the optical reflectance of transflective film  13  is 80%. 
         [0222]    As indicated by curve B in  FIGS. 47 to 50 , illumination device  1  according to Embodiment 15 exhibits almost the same light distribution characteristics as the light distribution characteristics (see  FIGS. 34 to 37 ) of illumination device  1  according to Embodiment 13 and it is thus possible to obtain the same advantages as those of illumination device  1  according to 
         [0223]    Embodiment 13. 
         [0224]    (Embodiment 16) 
         [0225]      FIG. 51A  is a cross-sectional view (transverse cross-section) of illumination device  1  according to Embodiment 16 taken along the second direction.  FIG. 51B  is a plan view of board  4  on which plural light emitting elements  2  are mounted.  FIG. 52A  is a bottom view of light flux controlling member  3  according to Embodiment 16 and  FIG. 52B  is a plan view of light flux controlling member  3  according to Embodiment 16.  FIG. 52C  is a cross-sectional view (cross-sectional view in the second direction; corresponding to  FIG. 51A ) taken along line L-L of  FIG. 52B  and  FIG. 52D  is a cross-sectional view (cross-sectional view in the first direction) taken along line M-M of  FIG. 52B . The same elements as those of illumination device  1  and light flux controlling member  3  according to Embodiment 13 shown in  FIGS. 30 to 32  will not be described. 
         [0226]    As shown in  FIGS. 51A and 52 , light flux controlling member  3  has a shape in which light flux controlling member  3  according to Embodiment 13 is divided into two halves by central line L 1  (see  FIG. 31A ). Inner surface  10  and outer surface  14  of cap  8  does not have curvature in the first direction. That is, inner surface  10  and outer surface  14  of cap  8  do not affect the light distribution characteristics of emitted light of light emitting elements  2  in the first direction. On the other hand, inner surface  10  and outer surface  14  of cap  8  have curvature in the second direction. Therefore, inner surface  10  of cap  8  can change the light distribution characteristics of emitted light of light emitting elements  2  to desired light distribution characteristics in the second direction by controlling the reflecting direction of light from light emitting elements  2 . 
         [0227]    Supporting part  27  is disposed between the dividing surface and board  4 . Supporting part  27  of light flux controlling member  3  has a square column shape, and supports cap  8  on board  4 . End face (bottom end face)  27   a  of supporting part  27  of light flux controlling member  3  is fixed to board  4  (for example, by bonding, screwing, or pressing). 
         [0228]      FIGS. 53 to 56  are graphs illustrating the light distribution characteristics of illumination device  1  according to Embodiment 16.  FIG. 53  is a graph illustrating the light distribution characteristics of illumination device  1  when the optical reflectance of transflective film  13  is 50%.  FIG. 54  is a graph illustrating the light distribution characteristics of illumination device  1  when the optical reflectance of transflective film  13  is 60%.  FIG. 55  is a graph illustrating the light distribution characteristics of illumination device  1  when the optical reflectance of transflective film  13  is 70%.  FIG. 56  is a graph illustrating the light distribution characteristics of illumination device  1  when the optical reflectance of transflective film  13  is 80%. 
         [0229]    As indicated by curve B in  FIGS. 53 to 56 , illumination device  1  according to Embodiment 16 can realize deflected light distribution of emitting light backward from only sidewall  6  side. 
         [0230]    (Embodiment 17) 
         [0231]      FIG. 57  is a cross-sectional view (transverse cross-section) of illumination device  1  according to Embodiment 17 taken along the second direction. Illumination device  1  according to Embodiment 17 is the same as illumination device  1  according to Embodiment 16, except that the inner surface of supporting part  27  is formed of mirror surface  28 . The same elements as those of illumination device  1  and light flux controlling member  3  according to Embodiment 16 shown in  FIGS. 51 and 52  will not be described. 
         [0232]    As shown in  FIG. 57 , the inner surface of supporting part  27  of light flux controlling member  3  is formed of mirror surface  28  (see  FIG. 51A ). Therefore, light emitted from light emitting element  2  to supporting part  27  is reflected toward sidewall  6  or cap  8  by mirror surface  28 . 
         [0233]      FIGS. 58 to 61  are graphs illustrating the light distribution characteristics of illumination device  1  according to Embodiment 17.  FIG. 58  is a graph illustrating the light distribution characteristics of illumination device  1  when the optical reflectance of transflective film  13  is 50%.  FIG. 59  is a graph illustrating the light distribution characteristics of illumination device  1  when the optical reflectance of transflective film  13  is 60%.  FIG. 60  is a graph illustrating the light distribution characteristics of illumination device  1  when the optical reflectance of transflective film  13  is 70%.  FIG. 61  is a graph illustrating the light distribution characteristics of illumination device  1  when the optical reflectance of transflective film  13  is 80%. 
         [0234]    As indicated by curve B in  FIGS. 58 to 61 , illumination device  1  according to Embodiment 17 can realize more deflected light distribution in comparison with illumination device  1  according to Embodiment 16. 
         [0235]    (Embodiment 18) 
         [0236]    Configuration of Illumination device 
         [0237]      FIG. 62  is a perspective view of illumination device  1  according to Embodiment 18 of the invention. 
         [0238]    As shown in  FIG. 62 , illumination device  1  includes light emitting elements  2 , light flux control member  3 , and board  4 . In the description of Embodiment 18, the peripheral direction of ring-shaped board  4  is defined as a first direction and the diameter direction of ring-shaped board  4  is defined as a second direction. The first direction and the second direction are perpendicular to each other. 
         [0239]      FIG. 63A  is a cross-sectional view (transverse cross-section) in the second direction of illumination device  1 .  FIG. 63B  is a plan view of board  4  on which plural light emitting elements  2  are mounted. 
         [0240]    Illumination device  1  is used instead of a circular fluorescent lamp. As shown in  FIGS. 63A and 63B , illumination device  1  emits light from plural light emitting elements  2  arranged in a line in the first direction (the peripheral direction) through light flux controlling member  3 . One end  5  of light flux controlling member  3  is fixed to board  4  on which plural light emitting elements  2  are mounted with an adhesive. Central line L 1  (see  FIGS. 63A and 64A ) of light flux controlling member  3  is located in straight line L 2  (see  FIG. 63B ) connecting the centers of light emitting elements  2 . 
         [0241]    Configuration of Light Flux Controlling Member 
         [0242]      FIG. 64A  is a plan view of light flux controlling member  3 ,  FIG. 64B  is a cross-sectional view (a cross-sectional view in the second direction; corresponding to  FIG. 63A ) taken along line N-N of  FIG. 64A , and  FIG. 64C  is a bottom view of light flux controlling member  3 . 
         [0243]    As shown in  FIGS. 64A to 64C , light flux controlling member  3  has a shape obtained by connecting ends in the long-axis direction of light flux controlling member  3  according to Embodiment 13 to each other to form a ring shape. Inner surface  10  and outer surface  14  of cap  8  does not have curvature in the first direction (the peripheral direction). That is, inner surface  10  and outer surface  14  of cap  8  do not affect the light distribution characteristics of emitted light of light emitting elements  2  in the first direction (the peripheral direction). On the other hand, inner surface  10  and outer surface  14  of cap  8  have curvature in the second direction (the diameter direction). Therefore, inner surface  10  of cap  8  can change the light distribution characteristics of emitted light of light emitting elements  2  to desired light distribution characteristics in the second direction (the diameter direction) by controlling the reflecting direction of light from light emitting elements  2 . 
         [0244]      FIGS. 65 to 68  are graphs illustrating the light distribution characteristics of illumination device  1  according to Embodiment 18.  FIG. 65  is a graph illustrating the light distribution characteristics of illumination device  1  when the optical reflectance of transflective film  13  is 50%.  FIG. 66  is a graph illustrating the light distribution characteristics of illumination device  1  when the optical reflectance of transflective film  13  is 60%.  FIG. 67  is a graph illustrating the light distribution characteristics of illumination device  1  when the optical reflectance of transflective film  13  is 70%.  FIG. 68  is a graph illustrating the light distribution characteristics of illumination device  1  when the optical reflectance of transflective film  13  is 80%. 
         [0245]    As shown in  FIGS. 65 to 68 , illumination device  1  according to Embodiment 18 exhibits almost the same light distribution characteristics as the light distribution characteristics (see  FIGS. 34 to 37 ) of illumination device  1  according to Embodiment 13 and it is thus possible to obtain the same advantages as those of illumination device  1  according to Embodiment 13. 
         [0246]    (Embodiment 19) 
         [0247]    Configuration of Illumination Device 
         [0248]      FIG. 69A  is a cross-sectional view (transverse cross-section) of illumination device  1  according to Embodiment  19  taken along the second direction.  FIG. 69B  is a plan view of board  4  on which plural light emitting elements  2  are mounted. 
         [0249]    As shown in  FIGS. 69A and 69B , illumination device  1  includes light emitting elements  2 , light flux control member  3 , and board  4 . In the description of Embodiment 19, the peripheral direction of ring-shaped board  4  is defined as a first direction and the diameter direction of ring-shaped board  4  is defined as a second direction. The first direction and the second direction are perpendicular to each other. 
         [0250]    Illumination device  1  is used instead of a circular fluorescent lamp. As shown in  FIGS. 69A and 69B , illumination device  1  emits light from plural light emitting elements  2  arranged in a line in the first direction (the peripheral direction) through light flux controlling member  3 . One end  5  of light flux controlling member  3  is fixed to board  4  on which plural light emitting elements  2  are mounted with an adhesive. 
         [0251]    Configuration of Light Flux Controlling Member 
         [0252]      FIG. 70A  is a plan view of light flux controlling member  3 ,  FIG. 70B  is a cross-sectional view (a cross-sectional view in the second direction; corresponding to  FIG. 69A ) taken along line O-O of  FIG. 70A , and  FIG. 70C  is a bottom view of light flux controlling member  3 . 
         [0253]    As shown in  FIGS. 70A to 70C , light flux controlling member  3  has a shape obtained by connecting ends in the long-axis direction of light flux controlling member  3  according to Embodiment 17 to each other to form a ring shape. Inner surface  10  and outer surface  14  of cap  8  does not have curvature in the first direction (the peripheral direction). That is, inner surface  10  and outer surface  14  of cap  8  do not affect the light distribution characteristics of emitted light of light emitting elements  2  in the first direction (the peripheral direction). On the other hand, inner surface  10  and outer surface  14  of cap  8  have curvature in the second direction (the diameter direction). Therefore, inner surface  10  of cap  8  can change the light distribution characteristics of emitted light of light emitting elements  2  to desired light distribution characteristics in the second direction (the diameter direction) by controlling the reflecting direction of light from light emitting elements  2 . 
         [0254]      FIGS. 71 to 74  are graphs illustrating the light distribution characteristics of illumination device  1  according to Embodiment 19.  FIG. 71  is a graph illustrating the light distribution characteristics of illumination device  1  when the optical reflectance of transflective film  13  is 50%.  FIG. 72  is a graph illustrating the light distribution characteristics of illumination device  1  when the optical reflectance of transflective film  13  is 60%.  FIG. 73  is a graph illustrating the light distribution characteristics of illumination device  1  when the optical reflectance of transflective film  13  is 70%.  FIG. 74  is a graph illustrating the light distribution characteristics of illumination device  1  when the optical reflectance of transflective film  13  is 80%. 
         [0255]    As shown in  FIGS. 71 to 74 , illumination device  1  according to Embodiment 19 exhibits almost the same light distribution characteristics as the light distribution characteristics (see  FIGS. 34 to 37 ) of illumination device  1  according to Embodiment 13 and it is thus possible to obtain the same advantages as those of illumination device  1  according to Embodiment 13. 
         [0256]    (Modified Example) 
         [0257]    In the above-mentioned embodiments, transflective film  13  is formed on inner surface  10  of light flux controlling member  3 . However, the invention is not limited to the embodiments, but transflective film  13  may be formed on outer surface  14  of light flux controlling member  3 . That is, transflective film  13  of light flux controlling member  3  according to the invention can be formed on the surface (any one of inner surface  10  and outer surface  14 ) intersecting a part of emitted light out of emitted light of light emitting element  2 , whereby it is possible to obtain desired light distribution characteristics. Here, in order to reduce the interface in an optical path of reflected light to suppress optical loss, it is preferable that transflective film  13  be formed on inner surface  10  of light flux controlling member  3 . Transflective film  13  formed on inner surface  10  can be suppressed from damage and stripping due to handling of light flux controlling member  3  or the like. 
         [0258]    The disclosures of Japanese Patent Application No. 2010-155745, filed on Jul. 8, 2010, Japanese Patent Application No. 2011-047704, filed on Mar. 4, 2011, Japanese Patent Application No. 2011-083719, filed on Apr. 5, 2011, and Japanese Patent Application No. 2011-129749, filed on Jun. 10, 2011, including the specification, drawings, and abstract, are incorporated herein by reference in its entirety. 
         [0259]    Industrial Applicability 
         [0260]    The light flux controlling member and the illumination device having the light flux controlling member according to the invention are not limited to the case where they are used instead of an incandescent lamp or a fluorescent lamp, but can be widely used as a part of a chandelier or an indirect illumination device, by determining the reflectance of the transflective film of the light flux controlling member to obtain desired light distribution characteristics. 
         [0261]    Reference Signs List 
         [0262]      1  Illumination device 
         [0263]      2  Light emitting element (for example, LED) 
         [0264]      3  Light flux controlling member 
         [0265]      4  Board 
         [0266]      5  One end 
         [0267]      6  Sidewall (transmissive part) 
         [0268]      7  The other end 
         [0269]      8  cap (transflective part) 
         [0270]      10  Inner surface 
         [0271]      11  Central part 
         [0272]      12  Outer circumference 
         [0273]      13  Transflective film 
         [0274]      14  Outer surface 
         [0275]      17  Inner surface (inner peripheral surface) 
         [0276]      18  Outer surface (outer peripheral surface) 
         [0277]      21  Cover 
         [0278]      22  Opening end 
         [0279]      27  Supporting part 
         [0280]      27   a  End face (bottom end face) 
         [0281]      28  Mirror surface 
         [0282]      100  LED 
         [0283]      101  Light direction converting element 
         [0284]      102 B surface 
         [0285]      103 E surface 
         [0286]      104 D surface 
         [0287]      105 C surface 
         [0288]    L Optical axis (center of light flux) 
         [0289]    L 1  Central axis or central line
Disclosed is a luminous flux control member ( 3) comprising: a lid section ( 8) positioned, via an air layer, over one or two or more light-emitting elements ( 2) positioned on top of a substrate ( 4), and formed so as to intersect with the optical axis of the light-emitting elements ( 2); and side wall sections ( 6) that extend from the outer edge of the lid section ( 8) towards the substrate ( 4) side. The inner surface ( 10) of the lid section ( 8) is a concave surface with the center section thereof positioned closer to the light-emitting elements ( 2) than the outer peripheral section, and is covered by a transparent reflective film ( 13). The transparent reflective film ( 13) reflects some of the light from the light-emitting elements ( 2) towards the side wall sections ( 6) and allows the remaining light from the light-emitting elements ( 2) to pass through.