Abstract:
The peripheral edges of a mounting substrate ( 11 ) are wave-shaped with undulations, the peripheral edges having a relationship such that protrusions ( 11 T) and depressions ( 11 B) constituting undulations on opposing peripheral edges mesh together. The spacing (WT) between the protrusions ( 11 T) on the peripheral edges and the spacing (WB) between the depressions ( 11 B) on the peripheral edges are then constant, especially on the mounting substrate ( 11 ).

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to illumination devices for supplying light to a display panel in television monitors, digital signs, and the like, and also relates to display devices incorporating such an illumination device and a display panel. 
       BACKGROUND ART 
       [0002]    A liquid crystal display device (display device) that incorporates a non-luminous liquid crystal display panel (display panel) typically also incorporates a backlight unit (illumination device) for supplying light to the liquid crystal display panel. The backlight unit can employ one of many different types of light source. For example, the backlight unit disclosed in Patent Document 1 listed below employs an LED (light emitting diode) as a light source. 
         [0003]    As shown in a sectional view in  FIG. 9 , in the backlight unit disclosed in Patent Document 1, a planar light emitting member  181  has an LED  121  housed in it. As shown in a plan view in  FIG. 9B , the planar light emitting member  181  has edges composed of dents  182 A and juts  182 B. Between two planar light emitting members  181  placed next to each other, the dents  182 A and juts  182 B fit into each other, and this makes the planar light emitting members  181  less likely to be displaced along each other. 
       LIST OF CITATIONS 
     Patent Literature 
       [0004]    Patent Document 1: JP-A-2009-176899 
       SUMMARY OF INVENTION 
     Technical Problem 
       [0005]    In the backlight unit  149  disclosed in Patent Document 1, arranging planar light emitting members  181  in close contact with one another results in giving them as a whole a square or rectangular shape. This makes those planar light emitting members  181  difficult to use in backlight units of other shapes. 
         [0006]    The present invention has been made to overcome the inconvenience mentioned above, and aims to provide illumination devices and the like that incorporate a light source mounting member (for example, a mounting board for mounting an LED on it) that is less likely to be displaced and that can be assembled into various shapes. 
       Solution to Problem 
       [0007]    To achieve the above object, according to the present invention, an illumination device includes a light source and a plurality of mounting boards on which the light source is arranged. In this illumination device, the plurality of mounting boards are arranged in close contact with one another, the mounting boards have edges that are wavy as by being undulated (wave-shaped) or serrated (saw-tooth-shaped), abutting ones of the edges have wavy contours composed of protrusions and recessions that are in a meshing relationship, and the protrusions at the edges occur at constant intervals and the recessions at the edges occur at constant intervals. 
         [0008]    With this design, when the mounting boards are arranged in close contact with one another, their edges mesh with each other. This makes the mounting boards less likely to be displaced. In addition, even when the edges of adjoining mounting boards do not completely coincide but are displaced along each other, they make close contact with each other. Thus, arranging a plurality of mounting boards in close contact with one another results in giving them as a whole a shape other than rectangular. The mounting boards are then easy to cope with backlight units of various shapes. 
         [0009]    Preferably, the mounting boards are, at the edges thereof, fitted with connectors each including a positive terminal that electrically conducts to the positive electrode of the light source and a negative terminal that electrically conducts to the negative electrode of the light source, and between the connectors of adjoining ones of the mounting boards, the terminals of each of the same polarities electrically conduct to each other. 
         [0010]    With this design, the mounting boards arranged in close contact with one another achieve electrical conduction via their respective connectors. 
         [0011]    The light source may be, for example, a light emitting element. The light emitting element may include a plurality of light emitting elements that emit red, green, and blue light respectively, or a plurality of light emitting elements that emit white light. 
         [0012]    Preferably, the illumination device further includes a power adjustor which adjusts the amount of electric power supplied to the light source. 
         [0013]    Preferably, the illumination device further includes a diffusive member which diffuses light from the light source, and/or a luminance enhancing member which enhances luminance while transmitting light from the light source. 
         [0014]    The present invention encompasses display devices that include an illumination device as described above in combination with a display panel (for example, a liquid crystal display panel) that receives light from the illumination device. 
       Advantageous Effects of the Invention 
       [0015]    According to the present invention, mounting boards are less likely to be disclosed and in addition can be assembled into various shapes. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0016]    [ FIG. 1 ] is a plan view showing mounting boards in a backlight unit; 
           [0017]    [ FIG. 2 ] is an enlarged plan view of mounting boards; 
           [0018]    [ FIG. 3 ] is a plan view showing mounting boards in a backlight unit; 
           [0019]    [ FIG. 4 ] is an enlarged plan view of mounting boards; 
           [0020]    [ FIG. 5 ] is a plan view of a mounting board; 
           [0021]    [ FIG. 6 ] is a plan view of a mounting board; 
           [0022]    [ FIG. 7 ] is a perspective view showing display devices used in digital signage; 
           [0023]    [ FIG. 8 ] is an exploded perspective view of (an outline of) a liquid crystal display device as a display device; 
           [0024]    [ FIG. 9A ] is a sectional view of a planar light emitting member incorporating an LED as used in a conventional backlight unit; and 
           [0025]    [ FIG. 9B ] is a plan view showing a plurality of planar light emitting members arranged side by side. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0026]    An embodiment of the invention will be described below with reference to the accompanying drawings. For convenience&#39; sake, reference signs and the like are occasionally omitted, in which case other relevant drawings are to be referred to. 
         [0027]      FIG. 7  is a perspective view showing an example of digital signage. As shown in  FIG. 7 , display devices  69  mounted on buildings BG beside roads RD, and display devices  69  placed in front of buildings BG, serve as digital signs. 
         [0028]    In a case where such a display device  69  is, for example, a liquid crystal display device, as shown in a schematic diagram in  FIG. 8 , it includes a liquid crystal display panel (display panel)  59  and a backlight unit (illumination device)  49  which supplies light to the liquid crystal display panel  59 . 
         [0029]    The liquid crystal display panel  59  is composed of an active matrix substrate  51 , which includes switching devices such as TFTs (thin-film transistors), and a counter substrate  52 , which is disposed opposite the active matrix substrate  51 , bonded together with a sealing member (not shown). The gap between the two substrates  51  and  52  is filled with liquid crystal (not shown). 
         [0030]    The active matrix substrate  51  is, on its light entrance side, fitted with a polarizing film  53 , and the counter substrate  52  is, on its light exit side, fitted with a polarizing film  53 . Structured as described above, the liquid crystal display panel  59  displays images by utilizing variation in transmittance resulting from inclination of liquid crystal molecules. 
         [0031]    Next, the backlight unit  49 , which is located immediately behind the liquid crystal display panel  59 , will be described. The backlight unit  49  includes LED modules (light emitting modules) MJ, a diffusive plate  43 , and a luminance enhancing film  44  (a casing in which these are housed is referred to as a backlight chassis  42 ). 
         [0032]    The LED modules MJ include LEDs (light emitting diodes)  21 , which are light emitting elements acting as point light sources, and a mounting board  11 , on which those LEDs  21  are mounted. These will be described in detail later. 
         [0033]    The diffusive plate (diffusive member)  43  is a sheet-form optical member that is laid over the board surface  11 U (the mounting surface  11 U of the mounting board  11 ) on which the LEDs  21  are mounted all over. The diffusive plate  43  receives and diffuses the light emanating from the LED modules MJ. That is, the diffusive plate  43  diffuses the planar light formed by the plurality of LED modules MJ to illuminate the entire area over the liquid crystal display panel  59 . 
         [0034]    The luminance enhancing film (luminance enhancing member)  44  is, for example, an optical member that has a prism-like shape on its surface to alter the radiating properties of light. The luminance enhancing film  44  is located to cover the diffusive plate  43 . Thus, the luminance enhancing film  44  condenses the light emanating from the diffusive plate  43  to increase luminance. 
         [0035]    Structured as described above, the backlight unit  49  passes the planar light (backlight) formed by the LED modules MJ through the plurality of optical members  43  and  44  and supplies it to the liquid crystal display panel  59 . Receiving the backlight from the backlight unit  49 , the non-luminous liquid crystal display panel  59  provides improved display performance. 
         [0036]    Now, the LED modules MJ will be described in detail with reference to  FIGS. 3 and 4 .  FIG. 3  is a plan view that mainly shows the LED modules MJ of the backlight unit  49 , and  FIG. 4  is an enlarged view of part of  FIG. 3 . As shown in these diagrams, the backlight unit  49  has LEDs  21  all over (in  FIG. 1 , for convenience&#39; sake, connectors  35  etc. which will be described later, are omitted). 
         [0037]    The LEDs  21  are mounted on mounting boards  11 . As shown in  FIG. 5 , the mounting boards  11  have edges that are wavy as by being undulated (such as sinusoidal) edges. Each edge of a mounting board  11  is in a meshing relationship with the edge opposite it. That is, between mounting boards  11  having abutting edges, wavy protrusions  11 T in the undulated contour at one edge and recessions  11 B in the undulated contour at the other edge are opposite each other so that the protrusions  11 T and the recessions  11 B can make close contact with each other (the protrusions  11 T and the recessions  11 B have oppositely undulated shapes; that is, the protrusions  11 T, when made to protrude in the opposite direction, describe the recessions  11 B, and vice versa). 
         [0038]    With this design, as shown in  FIG. 3 , a plurality of mounting boards  11  of an identical shape, all with undulated edges, make close contact with each other in a lattice-form (matrix-form) arrangement. An assembly of a plurality of mounting boards  11  so put together in close contact with each other is referred to as a mounting board unit  13  (there is no particular limitation on how the mounting boards  11  are connected together; they may be bonded together with adhesive, or may be fixed together with a fixing member). When at least one mounting board  11  tends to be moved in a plurality of directions that cross each other on the board surface (for example, in the two directions in which the mounting boards  11  are arranged (of those directions, one is referred to as the X direction and the other is referred to as the Y direction)), it is prevented from moving by making contact with another, adjoining mounting board  11 . 
         [0039]    That is, that at least one mounting board  11  is prevented from moving by making contact with the other mounting boards  11  arranged in the direction crossing the direction in which it tends to be moved. Thus, on the overall mounting board  11 , the mounting boards  11  are less likely to be displaced in directions across the board surface (in any direction across it). 
         [0040]    In general, in a design where a plurality of square mounting boards are put together in close contact with one another to form an overall mounting board, when one mounting board tends to move in the two mutually perpendicular directions in which the mounting boards are arranged side by side, not only that one mounting board but also other mounting boards adjoining it move together. 
         [0041]    By contrast, in a design as shown in  FIG. 1  where a plurality of mounting boards  11  with undulated edges are put together to form an overall mounting board  11  as a whole, even when one mounting board  11  tends to move in two mutually perpendicular directions, it is prevented from moving by other mounting boards  11  engaging with that one mounting board  11 . Thus, it does not occur that a plurality of mounting board  11  move together relative to the other mounting boards  11 . That is, in the backlight unit  49  so structured, the mounting boards  11  are arranged stably with no possible displacement relative to each other (thus, the mounting board unit  13  as a whole has increased strength). 
         [0042]    The arrangement of the mounting boards  11 , however, is not limited to a matrix-form arrangement as shown in  FIGS. 3 and 4 . As described above, each mounting board  11  has wavy, specifically undulated, edges, and the protrusions  11 T and recessions  11 B in the wavy contours at abutting edges are in a meshing relationship. Here, special note should be taken of the fact that, as shown in  FIG. 5 , at the edges of the mounting boards  11 , the protrusions  11 T occur at constant intervals WT and the recessions  11 B occur at constant intervals WB (the intervals WT and WB are equal). 
         [0043]    With this design, when a plurality of mounting boards  11  are arranged side by side in two mutually perpendicular directions in a matrix-form arrangement as shown in  FIGS. 3 and 4 , adjoining mounting boards  11  make close contact with one another, and consequently their edges mesh together securely (in other words, one edge of a mounting board  11  necessarily abuts one other mounting board  11 ). The mounting boards  11  can make close contact with one another in different ways, as shown in  FIGS. 1 and 2  ( FIG. 2  being an enlarged view of part of  FIG. 1 ). 
         [0044]    Specifically, in a case where the undulated contour at each edge of each mounting board  11  is composed of three protrusions  11 T and three recessions  11 B as shown in  FIG. 2 , for example, of those three recessions  11 B, two engage with protrusions  11 T of another mounting board  11  and the other engages with a protrusion  11 T of yet another mounting board  11  (that is, one mounting board  11 , at one of its four edges, makes close contact with two other mounting boards  11  at one of their edges each; see the part enclosed by a dash-and-dot line in  FIG. 2 ). 
         [0045]    In a design like this where one edge of a mounting board  11  abuts a plurality of mounting boards  11 , as shown in  FIG. 1 , the mounting boards  11  are not in a matrix-form arrangement. In other words, even when the abutting edges of mounting boards  11  do not completely coincide but are displaced along each other, they make close contact with each other. That is, a plurality of mounting boards  11  make close contact with one another in an arrangement other than rectangular. Thus, the mounting board unit  13  can cope with backlight units  49  of various shapes. 
         [0046]    As shown in  FIG. 5 , each LED  21  has an anode (positive electrode)  31  and a cathode (negative electrode)  32 . The anode  31  and the cathode  32  connect to connectors  35  via conductors  33  ( 33 A,  33 B). Each connector  35  includes three terminals  36  ( 36 B,  36 A,  36 B) arranged side by side. Of these three terminals  36  arranged side by side, the one  36  at the center is a positive terminal  36 A, and those  36  at both ends are negative terminals  36 B (the conductor that electrically connects between the anode  31  and the positive terminal  36 A is identified by the reference sign  33 A, and the conductor that electrically connects between the cathode  32  and the negative terminals  36 B is identified by the reference sign  33 B). 
         [0047]    The connector  35 , which thus includes the positive terminal  36 A electrically conducting to the anode  31  of the LED  21  and the negative terminals  36 B electrically conducting to the cathode  32  of the LED  21 , is attached at each edge of each mounting board  11  having one of different shapes, so that the connectors  35  on adjoining mounting boards  11  electrically conduct to each other. Specifically, in a case where a plurality of mounting boards  11  are arranged in close contact with one another in a lattice-form arrangement as shown in  FIG. 4 , connectors  35  are arranged in such a way that abutting connectors  35  (hence, terminals of each of the same, positive and negative, polarities) abut each other to achieve both physical and electrical connection. 
         [0048]    With this design, when a positive and a negative power terminal  71 A and  71 B of an electric power supply  71  are electrically connected to the positive terminal  36 A and the negative terminals  36 B, respectively, of the connector  35  via conductors  72 , the LEDs  21 , now connected in parallel with one another, can receive electric current. Thus, the overall mounting board  11  has a simpler circuit configuration for current supply. With the design shown in  FIG. 4 , irrespective of which connector  35  the electric power supply  71  is connected to, all the LEDs  21  are supplied with electric current. 
         [0049]    On the other hand, with the design shown in  FIG. 2 , each group of mounting boards  11  among which abutting edges completely coincide requires an electric power supply  71 . 
       [Modifications and Variations] 
       [0050]    The present invention is in no way limited by the embodiment specifically described above, and many modifications and variations are possible without departing from the spirit of the invention. 
         [0051]    For example, although the above description deals with a case where the mounting boards  11  have undulated edges as an example of wavy edges, this is not meant as any limitation. For example, as shown in  FIG. 6 , the mounting boards  11  may have serrated (saw-tooth-shaped) edges as wavy edges. 
         [0052]    Although the above description deals with a case where one mounting board  11  has one LED  21  mounted on it, this is not meant as any limitation. For example, one mounting board  11  has a plurality of LEDs mounted on it. Using mounting boards  11  each having a polarity of LEDs  21  mounted on them makes it possible to vary the density (of distribution) of LEDs  21  in the backlight unit  49  as necessary. 
         [0053]    For example, since people&#39;s visual attention tends to concentrate at the center of a liquid crystal display panel, the luminance there is often raised compared with elsewhere on the liquid crystal display panel. In such cases, using mounting boards  11  each having a plurality of LEDs  21  mounted on them makes it possible to arrange the LEDs  21  more densely near the center of the mounting board unit  13  corresponding to the center of a liquid crystal display panel than elsewhere. 
         [0054]    Although the above description deals with a case where display devices  69  mounted on buildings are taken up as an example of digital signage, this is not meant as any limitation. For example, display devices  69  mounted on walls inside railroad cars also serve digital signage. Needless to say, the backlight unit  49  described above finds applications not only in digital signage but also in liquid crystal display devices for home use. 
         [0055]    There is no particular limitation on the emission color of the LEDs  21 . For example, LEDs  21  emitting red light, LEDs  21  emitting green light, and LEDs  21  emitting blue light may be used in combination in the backlight unit  49  so that the light from them mixes to produce white light, or to produce light of any other color (light of any single or mixed color). That is, the backlight unit  49  may be a full-color illumination device (light source device). Needless to say, all the LEDs  21  may be LEDs  21  that emit white light. 
         [0056]    It is preferable that the LEDs  21  be supplied with electric power adequately, that is, neither excessively nor insufficiently. To that end, the LEDs  21  are connected to, for example, an unillustrated supply electric power adjustment device (power adjustor) incorporated in the backlight unit  49 . 
       INDUSTRIAL APPLICABILITY 
       [0057]    The present invention finds applications in a variety of display devices such as television monitors, digital signs, etc. 
       LIST OF REFERENCE SIGNS 
       [0058]      11  mounting board 
         [0059]      11 T protrusion at an wavy edge of a mounting board 
         [0060]      11 B recession at an wavy edge of a mounting board 
         [0061]      13  mounting board unit 
         [0062]      21  LED (point light source, light emitting element) 
         [0063]      31  anode (positive electrode) 
         [0064]      32  cathode (negative electrode) 
         [0065]      33  conductor 
         [0066]      35  connector 
         [0067]      36  terminal 
         [0068]      36 A positive terminal 
         [0069]      36 B negative terminal 
         [0070]      43  diffusive plate (diffusive member) 
         [0071]      44  luminance enhancing film (luminance enhancing member) 
         [0072]      49  backlight unit 
         [0073]      69  display device 
         [0074]      71  electric power supply 
         [0075]      72  conductor