Abstract:
A planar lighting device comprises: a mounting substrate having a conduction pattern having an extension part formed on a base material, and a cover member is arranged on the conduction pattern, wherein the cover member has an opening that exposes together the two lands of the two adjacent light sources, and wherein the extension parts comprise: a first extension part formed to extend from a first end portion of the lands toward the light guide plate and to extend under the cover member; a second extension part formed to extend from a second end portion, toward the light guide plate and the other land of the pair of the lands and to extend under the cover member; and a third extension part formed to extend from the first end portion, toward an opposite side to the light guide plate and to extend under the cover member.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority from Japanese Patent Application No. 2012-009647 filed on Jan. 20, 2012, the entire subject matter of which is incorporated herein by reference. 
     TECHNICAL FIELD 
     This disclosure relates to a planar lighting device of a side light type in which a light source is arranged at a side of a light guide plate. 
     BACKGROUND 
     In recent years, a backlight that is used for a liquid crystal display device and the like is required to have higher brightness so as to further improve the visibility of a display screen. 
     However, in a pattern shape of current connection wirings formed on a circuit substrate having an LED (Light Emitting Diode) as a light source mounted thereon, a distance between the LEDs to be mounted is limited, so that there is a limit on the number of the LEDs. 
     In the meantime, the known references relating to this disclosure is JP-A-2004-233809 and JP-A-2006-237320, for example. 
       FIG. 5A  is a plan view illustrating a light source unit of a side light-type backlight according to the background art and  FIG. 5B  is an enlarged plan view of an example of a substrate (circuit substrate having an LED mounted thereon) in the light source unit of the side light-type backlight according to the background art. 
     As shown in  FIG. 5A , according to the side light-type backlight of the background art, a plurality of LEDs  101  mounted on a substrate  102  is arranged with contacting a side end face  103   s  of a light guide plate  103 . The plurality of LEDs  101  illuminates the light from the side end face  103   s  of the light guide plate  103  to an inside thereof. 
     The substrate  102  on which the plurality of LEDs  101  is mounted is an FPC (Flexible Printed Circuit) and a face thereof is covered with an insulating coverlay  104 , as shown in  FIG. 5B . A land  102   r , to which a pair of electrodes (not shown) of each LED  101  is respectively connected, is exposed from an opening  104   k  of the coverlay  104 , including a part of a connection wiring (conduction wiring) connected to the land  102   r . In other words, a part of the connection wiring connecting the opposed lands  102   r  of the adjacent LEDs  101  is covered by a part of the coverlay  104 . On the substrate  102 , a plurality of pairs of lands  102   r , each pair of which corresponds to the pair of electrodes of each LED  101 , is arranged at an interval of a pitch pt 1  (refer to  FIG. 5B ). 
     SUMMARY 
     Meanwhile, the backlight, i.e., planar lighting device of the liquid crystal panel that is used for a PDA (Personal Digital Assistance) and the like is required to have the higher brightness. A configuration is considered in which more LEDs  101  are arranged on a light incidence face (side end face  103   s ) that is a side face of the light guide plate  103 . In this case, following two problems are caused. 
     As a first problem, as disclosed in JP-A-2004-233809, when all the LEDs are serially driven, a driving voltage is excessively increased. 
     As a second problem, as disclosed in JP-A-2006-237320, it is difficult to provide the coverlay between the adjacent LEDs due to limits on the coverlay processing and the adhesion position precision of the connection wiring. If there is no coverlay on the connection wiring arranged between the adjacent LEDs, the break may be caused due to insufficient adhesion strength. 
     With respect to the first problem of the above two problems, the configuration of JP-A-2004-233809, i.e., all the LEDs  101  are divided into a plurality of groups and are then driven, so that it is possible to decrease the driving voltage. 
     However, regarding the second problem, when the configuration of JP-A-2004-233809 is adopted, i.e., all the LEDs  101  are divided into a plurality of groups and are then arranged so that the LEDs belonging to the different groups are adjacent to each other, it is not possible to directly adopt the connection wiring disclosed in JP-A-2006-237320. 
     In detail, it is premised in JP-A-2006-237320 that the adjacent LEDs are serially connected each other, and but the LEDs belonging to the adjacent different groups are connected in the configuration of JP-A-2004-233809. That is, according to JP-A-2004-233809, the LEDs belonging to the same group are serially connected each other, so that it is not possible to serially connect the LEDs belonging to the adjacent different groups. 
     In addition to the above second problem, in order to stably secure the lighting characteristics (high brightness and uniform lighting) of the planar lighting device with a high level, it is necessary to fix all the LEDs at predetermined positions with high precision. Accordingly, it is necessarily required to perform the self-alignment with high precision upon the mounting of the LEDs on (the lands of) the FPC. 
     With considering the above, this disclosure provides at least a planar lighting device having high reliability and capable of stably realizing high brightness and uniform lighting. 
     In this disclosure, a planar lighting device of this disclosure comprises: a light guide plate; a plurality of light sources that is arranged in a line shape along a longitudinal direction of a side end face of the light guide plate, and a mounting substrate, on which the light sources are respectively mounted. The mounting substrate has a base material and a conduction pattern formed on the base material, and a cover member is arranged on the conduction pattern, the conduction pattern comprises a plurality of pairs of lands, which is provided in the longitudinal direction to be corresponding to a pair of electrode terminals of each light source and to which the pair of electrode terminals is respectively connected, and extension parts that are respectively connected to the pair of lands, the cover member has an opening that exposes together the two lands, which face each other, of the two pairs of lands, which are respectively corresponding to the two adjacent light sources. The extension parts comprise: a first extension part that is formed to extend from a first end portion of the lands, which faces the land of the adjacent light source, toward the light guide plate and to extend under the cover member; a second extension part that is formed to extend from a second end portion, which is opposite to the first end portion of the corresponding land in the longitudinal direction, toward the light guide plate and the other land of the pair of the lands and to extend under the cover member; and a third extension part that is formed to extend from the first end portion, to which the first extension part is provided, toward an opposite side to the light guide plate and to extend under the cover member. 
     According to the above planar lighting device, the cover member provided on the conduction pattern has an opening that exposes together the two lands, which face each other, of the two pairs of lands, which are respectively corresponding to the two adjacent light sources, and the extension parts comprise: a first extension part that is formed to extend from a first end portion of the lands, which faces the land of the adjacent light source, toward the light guide plate and to extend under the cover member; a second extension part that is formed to extend from a second end portion, which is opposite to the first end portion of the corresponding land in the longitudinal direction, toward the light guide plate and the other land of the pair of the lands and to extend under the cover member; and a third extension part that is formed to extend from the first end portion, to which the first extension part is provided, toward an opposite side to the light guide plate and to extend under the cover member. Therefore, it is possible to suppress the conduction pattern and the light sources from being peeled off from the mounting substrate while performing the self-alignment with high precision when mounting the light source on the mounting substrate. Also, it is possible to mount the light sources on the mounting substrate while narrowing an interval of the light sources as much as possible. Thereby, it is possible to realize the high brightness and uniform lighting of the planar lighting device. 
     In the above-described planar lighting device, the third extension part may be formed to be wider or to have a larger area than the first extension part. According to this planar lighting device, the third extension part is formed to be wider or to have a larger area than the first extension part at the light guide plate-side of the light source. Therefore, it is possible to make the areas of the conduction pattern uniform at the light guide plate-side of the light source and at an opposite side to the light guide plate. 
     In the above-described planar lighting device, the second extension part, which is provided to each light source, may have a wide shape so that a gap having a stripe shape is formed between the second extension part of one of the pair of the lands and the second extension part of the other of the pair of the lands. According to this planar lighting device, the second extension part has a wide shape in which a gap having a stripe shape is formed between the second extension parts. Therefore, it is possible to suppress the second extension part from being peeled off from the mounting substrate. 
     In the above-described planar lighting device, the conduction pattern may comprise a wiring pattern to which at least a part of the extension part is electrically connected, and the wiring pattern may be formed so that the one light source can be driving-controlled independently from the other adjacent light source. According to the above planar lighting device, the light source can be driving-controlled independently from the other adjacent light source. 
     In this disclosure, a planar lighting device comprises: a light guide plate; a plurality of light sources that is arranged in a line shape along a longitudinal direction of a side end face of the light guide plate, and a mounting substrate on which the light sources are respectively mounted. A cover member is arranged on a conduction pattern that is formed on a base material of the mounting substrate, the conduction pattern comprises a plurality of pairs of lands, which is provided with centering around the light source in the longitudinal direction to be corresponding to a pair of electrode terminals of each light source and to which the pair of electrode terminals is respectively connected, and extension parts that are connected to the pair of lands, and the cover member has an opening that exposes the two lands, which face each other, of the two pairs of lands, which are respectively corresponding to the two adjacent light sources. The extension part comprises: an outside extension part is formed to extend from a first end portion of the lands, which faces the land of the adjacent light source, toward the light guide plate and an opposite side to the light guide plate and to extend under the cover member; and an inside extension part that is formed to extend from a second end portion, which is opposite to the first end portion of the corresponding land in the longitudinal direction, toward the light guide plate and to extend under the cover member. 
     According to the above planar lighting device, the cover member that is provided on the conduction pattern has an opening that exposes the two lands, which face each other, of the two pairs of lands, which are respectively corresponding to the two adjacent light sources. The extension part comprises: an outside extension part is formed to extend from a first end portion of the lands, which faces the land of the adjacent light source, toward the light guide plate and an opposite side to the light guide plate and to extend under the cover member; and an inside extension part that is formed to extend from a second end portion, which is opposite to the first end portion of the corresponding land in the longitudinal direction, toward the light guide plate and to extend under the cover member. Therefore, it is possible to suppress the conduction pattern and the light sources from being peeled off from the mounting substrate while performing the self-alignment with high precision when mounting the light source on the mounting substrate. Also, it is possible to mount the light sources on the mounting substrate while narrowing an interval of the light sources as much as possible. Thereby, it is possible to realize the high brightness and uniform lighting of the planar lighting device. 
     In the above-described planar lighting device, a gap may be formed between a pair of the inside extension parts that is provided to each light source. According to this planar lighting device, the gap is formed between a pair of the inside extension parts. Therefore, it is possible to enable the pair of inside extension parts to be wide or to have a large area, respectively, so that it is possible to suppress the inside extension parts from being peeling off from the mounting substrate. 
     In the above-described planar lighting device, wherein an area of the outside extension part, which extends toward the opposite side to the light guide plate, is formed to be wider or to have a larger area than an area extending toward the light guide plate. 
     According to the above planar lighting device, an area of the outside extension part, which extends toward the opposite side to the light guide plate, may be formed to be wider or to have a larger area than an area extending toward the light guide plate. Therefore, it is possible to suppress or reduce the non-uniformity of the areas of the conduction pattern at the light guide plate-side of the light source and an opposite side thereof to the light guide plate. 
     In the above-described planar lighting device, the one light source may be driving-controlled independently from the other adjacent light source. According to this planar lighting device, it is possible to perform the independent driving control between the adjacent light sources. 
     In the above-described planar lighting device, the mounting substrate may be a flexible printed circuit board. According to this lighting device, it is possible to narrow a space of the planar lighting device. 
     In this disclosure, a mounting substrate, on which light sources are respectively mounted along a longitudinal direction of the mounting substrate, comprises: a base material; a conduction pattern that is formed on a base material; and a cover member that is arranged on the conduction pattern. The conduction pattern comprises a plurality of pairs of lands, which is provided with centering around the light source in the longitudinal direction to be corresponding to a pair of electrode terminals of each light source and to which the pair of electrode terminals is respectively connected, and extension parts that are connected to the pair of lands, and the cover member has an opening that exposes both one of the pair of the lands of a first light source and one of the pair of the lands of a second light source, which face each other. The extension part comprises: a first extension part that is formed to extend from one end of the lands in a first direction and a second direction, which is opposite to the first direction, and to extend under the cover member; and a second extension part that is formed to extend from one end of the lands in the first direction and a direction toward the other land of the pair of the lands of the respective light sources and to extend under the cover member. 
     According to this disclosure, it is possible to provide a planar lighting device having high reliability and capable of stably realizing high brightness and uniform lighting. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing and additional features and characteristics of this disclosure will become more apparent from the following detailed descriptions considered with the reference to the accompanying drawings, wherein 
         FIG. 1A  is a plan view illustrating a planar lighting device according to an illustrative embodiment of this disclosure, and  FIG. 1B  is an enlarged view of an A part of  FIG. 1A ; 
         FIG. 2  is an enlarged view illustrating a light guide plate and a state where LEDs are mounted on an FPC according to the illustrative embodiment. 
         FIG. 3A  is a plan view illustrating a front face of the FPC according to the illustrative embodiment, and  FIG. 3B  is a plan view illustrating a back face of the FPC according to the illustrative embodiment; 
         FIG. 4  is an enlarged view illustrating an example of a conduction pattern of a part on which one LED is mounted; and 
         FIG. 5A  is a plan view illustrating a light source unit of a side light-type backlight of the background art, and  FIG. 5B  is an enlarged plan view illustrating an example of a substrate (circuit board on which an LED is mounted) in the light source unit of the side light-type backlight of the background art. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, an illustrative embodiment of this disclosure will be described with reference to the accompanying drawings. 
       FIG. 1A  is a plan view illustrating a planar lighting device according to an illustrative embodiment of this disclosure, and  FIG. 1B  is an enlarged view of an A part of  FIG. 1A . 
       FIG. 2  is an enlarged view illustrating a light guide plate and a state where LEDs are mounted on an FPC according to the illustrative embodiment. 
     A planar lighting device S of an illustrative embodiment is a planar lighting device that is used for a backlight of a liquid crystal panel and the like and illuminates light from the rear. 
     The planar lighting device S is a lighting device called as a side light-type backlight in which LEDs (Light Emitting Diodes) as a light source are arranged on a side of a light guide plate  2 . 
     Specifically, according to the planar lighting device S, a plurality of LEDs  1  ( 1   r ,  1   g ,  1   b ) is mounted on an FPC  3 , is arranged with contacting a side end face  2   s  of a light guide plate  2  and illuminates light toward the light guide plate  2 . In the meantime, the LEDs  1  are all white LEDs and the white LEDs are classified into three groups of the LEDs  1   r , the LEDs  1   g  and the LEDs  1   b . That is, the LEDs  1   r  are LEDs belonging to the first group of the white LEDs, the LEDs  1   g  are LEDs belonging to the second group of the white LEDs and the LEDs  1   b  are LEDs belonging to the third group of the white LEDs. 
     A reflective sheet (not shown) that reflects light, which deviates from a total reflection condition of the light guide plate  2  and leaks rearwards, to the front (the front side in the sheet of  FIG. 1A ) is arranged at the rear (back side in the sheet of  FIG. 1A ) of the light guide plate  2 . In the meantime, a diffusion sheet that diffuses the light, a prism sheet (not shown) for increasing brightness and the like are arranged at the front (the front side in the sheet of  FIG. 1A ) of the light guide plate  2 . 
       FIG. 3A  is a plan view illustrating a front face of the FPC according to the illustrative embodiment, and  FIG. 3B  is a plan view illustrating a back face of the FPC according to the illustrative embodiment. Meanwhile, in  FIG. 3A , electrode terminals dra, drb, dga, dgb, dba, dbb of the LEDs  1  are shown with black so as to clarify a positional relation with conduction patterns r 1 , r 2 , h 1   a , h 1   b , h 2   a , h 2   b , h 3   a , h 3   b  exposed from openings  4   k  of a coverlay  4 , irrespective of the groups to which the LEDs belong. 
       FIG. 4  is an enlarged view illustrating an example (around a pair of lands in a B part of  FIG. 3A ) of a conduction pattern of a part on which one LED is mounted. Meanwhile, in the B part of  FIG. 3A , the LED  1   g  of the second group is arranged. The face and back face of the FPC  3  are formed with wiring patterns p 1 , p 2 , p 3 , p 4 , lands r 1 , r 2  and extension parts h 1   a , h 1   b , h 2   a , h 2   b , h 3   a , h 3   b  (refer to  FIG. 4 ), which are conduction patterns of a conductive foil such as copper, formed by etching and the like. That is, not only the wiring patterns p 1 , p 2 , p 3  but also the lands r 1 , r 2  and the extension parts h 1   a , h 1   b , h 2   a , h 2   b , h 3   a , h 3   b  are conductive conduction patterns. 
     As shown in  FIGS. 3A and 4 , the coverlay  4  is arranged on the lands r 1 , r 2  and the extension parts h 1   a , h 1   b , h 2   a , h 2   b , h 3   a , h 3   b  (which are the conduction patterns of the FPC  3 ) so that the facing lands r 2 , r 1  of the pair of lands r 1 , r 2 , which face each other, of two sets of the adjacent LEDs  1  are integrally exposed from the openings  4   k . In other words, both one land of the pair of lands r 1 , r 2  of one LED  1 ( 1   r ) and one land of the pair of lands r 1 , r 2  of other LED 1  ( 1   g  or  1   b ), which is adjacent to one LED, are integrally exposed from the opening  4   k . Meanwhile, in  FIGS. 3A and 4 , the coverlay  4  (openings  4   k ) is shown with the dashed-two dotted line. 
     That is, the surface (refer to  FIG. 3A ) of the FPC  3  is covered with the coverlay  4  having the openings  4   k . The coverlay  4  is an insulating material having heat resistance and adhesiveness. 
     The pair of electrode terminals dra, drb, the pair of the electrode terminals dga, dgb and the pair of the electrode terminals dba, dbb of the adjacent LEDs  1  ( 1   r ,  1   g ,  1   b ) are soldered, fixed and electrically connected to the respective corresponding lands r 1 , r 2  over areas of the coverlay  4  between the openings  4   k . Thereby, the respective LEDs  1  are mounted on the FPC  3 . 
     For example, in the case of the rightmost LED  1   r  of the first group of the FPC  3  in  FIG. 1A , the electrode terminal dra thereof is soldered to the land r 1  (refer to  FIG. 4 ) through the opening  4   k  of the coverlay  4  and the electrode terminal drb is soldered to the land r 2  (refer to  FIG. 4 ) through the opening  4   k  of the coverlay  4 , as shown in  FIGS. 1B and 3A . 
     Likewise, in the case of the LED  1   g  of the second group of the FPC  3  at the second position from the right in  FIG. 1A , the electrode terminal dga thereof is soldered to the land r 1  through the opening  4   k  of the coverlay  4  and the electrode terminal dgb is soldered to the land r 2  through the opening  4   k  of the coverlay  4 , as shown in  FIGS. 3A and 4 . 
     Likewise, in the case of the LED  1   b  of the third group of the FPC  3  at the third position from the right in  FIG. 1A , the electrode terminal dba thereof is soldered to the land r 1  through the opening  4   k  of the coverlay  4  and the electrode terminal dbb is soldered to the land r 2  through the opening  4   k  of the coverlay  4 , as shown in  FIG. 3A . The other LEDs  1  are also mounted on the FPC  3  in the same manner. 
     Like this, the coverlay  4  (the coverlay  4  between the openings  4   k ) is arranged between the lands r 1 , r 2  of the LED  1 . In order to achieve a narrow pitch of the LEDs  1 , the conduction patterns r 1 , r 2 , h 1   a , h 1   b , h 2   a , h 2   b , h 3   a , h 3   b , p 1  to p 4  are shaped as described below. 
     Here, the backlight has a structure (design) where the LEDs  1  are abutted (contacted) and assembled on the side end face  2   s  of the light guide plate  2 , as shown with a white arrow α 1  of  FIG. 2 . Therefore, the peeling strength of the LED  1  from the FPC  3 , i.e., the fixing strength of the LED  1  to the FPC  3  is very important. 
     In the abutting process, an external force is applied so that the wiring (conduction pattern) of the FPC  3  at the light guide plate  2 -side (at the front) uplifts from (a base material  3   b  of) the FPC  3 , and also an external force is applied so that the wiring (conduction pattern) at an opposite side (at the rear) of the light guide plate  2  is pressed to the FPC  3 . Accordingly, the wiring at the light guide plate  2 -side (at the front) is more apt to be peeled off from the base material  3   b  than the wiring of the opposite side (at the rear) of the light guide plate  2 . 
     &lt;FPC  3 &gt; 
     The FPC  3  of  FIG. 3 , in which both sides thereof are formed with the wiring patterns, is configured to mount the LEDs  1  that are the twelve white LEDs, as shown in  FIG. 1A . As described above, the twelve LEDs  1  are classified into the three groups, i.e., the LEDs  1   r  belonging to the first group, the LEDs  1   g  belonging to the second group and the LEDs  1   b  belonging to the third group, and each group has four LEDs  1  ( 1   r ,  1   g ,  1   b ). That is, the twelve LEDs  1  are configured by the four LEDs  1   r  of the first group, the four LEDs  1   g  of the second group and the four LEDs  1   b  of the third group. 
     The twelve LEDs  1  ( 1   r ,  1   g ,  1   b ) are arranged so that four units are repeated from one end (right end) of the FPC  3  toward the other end (left end), in which one unit is configured by the LED  1   r  of the first group, the LED  1   g  of the second group and the LED  1   b  of the third group. 
     As shown in  FIG. 3 , the LEDs  1  ( 1   r ,  1   g ,  1   b ) belonging to the respective groups are serially connected each other. That is, the LEDs  1   r  of the first group of the twelve LEDs  1  are serially connected each other, the LEDs  1   g  of the second group are serially connected each other and the LEDs  1   b  of the third group are serially connected each other. 
     Specifically, the FPC  3  shown in  FIG. 3  has the base material  3   b  and the conduction patterns (p 1  to p 4 , h 1   a , h 1   b , h 2   a , h 2   b , h 3   a , h 3   b , r 1 , r 2 ) formed on the base material  3   b . The FPC  3  has an LED mounting part  3 A on which the LEDs  1  are mounted, the wiring patterns p 1  to p 4  for connection to the LEDs  1  and a wiring part  3 B in which a connection terminal st (refer to  FIG. 3B ) to be electrically connected to the wiring patterns is provided. 
     The front face and back face of the FPC  3  are formed with the wiring patterns p 1 , p 2 , p 3 , p 4  for supplying current (voltage) to the LEDs  1  ( 1   r ,  1   g ,  1   b ) by the etching and the like, together with the lands r 1 , r 2  to which the respective LEDs  1  are connected and the extension parts h 1   a , h 1   b , h 2   a , h 2   b , h 3   a , h 3   b.    
     The FPC  3  is formed with through-holes th for electrically connecting the wiring patterns p 1  to p 4  on the face shown in  FIG. 3A  and the wiring patterns p 1  to p 4  on the backside shown in  FIG. 3B . 
     The pair of electrode terminals dra, drb of the LED  1   r  belonging to the first group is connected to the wiring pattern p 1 , the pair of electrode terminals dga, dgb of the LED  1   g  belonging to the second group is connected to the wiring pattern p 2 , and the pair of electrode terminals dba, dbb of the LED  1   b  belonging to the third group is connected to the wiring pattern p 3 . In the meantime, the wiring pattern p 4  is a ground line. 
     That is, the respective four LEDs  1   r  of the first group are serially connected through the wiring pattern p 1  and through-holes th formed on the face and back face of the FPC  3 . Also, the respective four LEDs  1   g  of the second group are serially connected through the wiring pattern p 2  and through-holes th formed on the face and back face of the FPC  3 . Likewise, the respective four LEDs  1   b  of the third group are serially connected through the wiring pattern p 3  and through-holes th formed on the face and back face of the FPC  3 . 
     As shown in  FIG. 1 , regarding the LED  1  as one point-like light source and the LED  1  as the other adjacent point-like light source, the LEDs belonging to the different groups are arranged. That is, the LED  1   g  of the second group is arranged in the vicinity of the LED  1   r  of the first group, the LED  1   b  of the third group is arranged in the vicinity of the LED  1   g  of the second group and the LED  1   r  of the first group is arranged in the vicinity of the LED  1   b  of the third group. 
     Like this, the LED  1  of the point-like light source and the LED  1  as the point-like light source belonging to the other adjacent group are adapted so that they can be independently driving-controlled through the wiring patterns p (p 1 , p 2 , p 3 ). That is, the LED  1   r  of the first group, the LED  1   g  of the second group and the LED  1   b  of the third group are connected so that they can be independently driving-controlled through the wiring patterns p 1  to p 4 , respectively. 
     Meanwhile, in this illustrative embodiment, the configuration has been exemplified in which the LEDs  1  ( 1   r ,  1   g ,  1   b ) of the three adjacent sets (three adjacent groups) can be independently driving-controlled. However, a wiring pattern may be also formed so that the two sets (two groups) or four sets (four groups) or more can be independently driving-controlled. 
     &lt;Conduction Patterns&gt; 
     In the below, the features of the conduction patterns (p 1  to p 4 , r 1 , r 2 , h 1   a , h 1   b , h 2   a , h 2   b , h 3   a , h 3   b ) of the FPC  3  of this illustrative embodiment are described with reference to  FIG. 4 . 
     In  FIG. 4 , in order to clarify a positional relation between the electrode terminals dga, dgb of the LED  1   g  of the second group and the conduction patterns r 1 , r 2 , h 1   a , h 1   b , h 2   a , h 2   b , h 3   a , h 3   b , the electrode terminals dga, dgb having an L shape of the LED  1   g  of the second group are blackly shown to overlap over the lands r 1 , r 2 . 
     As described above, the pairs of electrode terminals dra, drb, dga, dgb, dba, dbb of the respective LEDs  1  (refer to  FIG. 1 ) are respectively soldered and fixed to the lands r 1 , r 2  having a rectangular shape shown in  FIG. 4 . 
     The conduction patterns formed on the FPC  3  have following features. 
     First, the first extension part h 1   a  that is a wiring is formed which extends from one corner (end portion), which is an outer side (left side of the land r 1  in  FIG. 4 ) of the one land r 1  (which is shown with the solid line and dashed-two dotted line in  FIG. 4 ) having a rectangular shape, i.e., a side facing the LED  1   b  (refer to  FIG. 1A ) of the third group adjacent at the left side of  FIG. 4  opposite to the other land r 2  in the X direction (longitudinal direction of the FPC  3 ) of  FIG. 4 , and which is a side (in the Y direction (width direction of the FPC  3 )) at which the light guide plate  2  is arranged, toward the light guide plate  2 . 
     The first extension part h 1   a  has a rectangular shape and is connected to the wiring pattern p 4 . In the first extension part h 1   a , a part thereof at the land r 1 -side is exposed from the opening  4   k  (which is shown with the dashed-two dotted line in  FIG. 4 ) of the coverlay  4  and the other part thereof is covered by the coverlay  4 . A leading end of the first extension part h 1   a  is electrically connected to the wiring pattern p 4 . 
     Also, the first extension part h 1   b  that is a wiring is formed which extends from one corner (end portion) of an outer side (right side of the land r 2  in  FIG. 4 ) of the other land r 2  (which is shown with the solid line and dashed-two dotted line in  FIG. 4 ) having a rectangular shape, i.e., a side facing the LED  1   r  (refer to  FIG. 1A ) of the first group adjacent at the right side of  FIG. 4  opposite to the one land r 1  in the X direction (longitudinal direction of the FPC  3 ) of  FIG. 4 , which is a side (in the Y direction (width direction of the FPC  3 )) at which the light guide plate  2  is arranged, toward the light guide plate  2 . 
     The first extension part h 1   b  has a rectangular shape. The first extension part h 1   b  is electrically connected to the second extension part h 2   b  that will be described later, and is electrically connected to the wiring pattern p 2  (refer to  FIG. 3B ) formed on the backside, through the through-hole th 1 . 
     Second, the second extension part h 2   a  that is a wiring is formed which extends from one corner of an inner side (a side facing the other land r 2  in the X direction in  FIG. 4 ) of one land r 1 , at which the light guide plate  2  is arranged, toward the light guide plate  2 . 
     The second extension part h 2   a  has a wide shape so that it extends toward the light guide plate  2  and the other land r 2 . The second extension part h 2   a  has a wide shape extending up to a level at which a gap s 1  having a stripe shape is formed between the second extension part h 2   a  and the pairing second extension part h 2   b  that will be described below. In the second extension part h 2   a , most of parts (areas) except for a part (area) facing the land r 1  are covered by the coverlay  4  and the part (area) facing the land r 1  is exposed from the opening  4   k  (which is shown with the dashed-two dotted line in  FIG. 4 ) of the coverlay  4 . 
     That is, a space, which is inevitably formed between the pair of lands r 1 , r 2  by the structure of the electrode terminals dga, dgb of the LED  1   g  of the second group, is effectively used to form the second extension part h 2   a  of the conduction pattern. In the meantime, the second extension part h 2   a  is directly and electrically connected to the wiring pattern p 4 . 
     Also, the second extension part h 2   b  that is a wiring is formed which extends from one corner of an inner side (a side facing the one land r 1  in the X direction in  FIG. 4 ) of the other land r 2 , at which the light guide plate  2  is arranged, toward the light guide plate  2 . 
     The second extension part h 2   b  has a wide shape so that it extends toward the light guide plate  2  and the other land r 1 . The second extension part h 2   b  has a wide shape extending up to a level at which a gap s 1  having a stripe shape is formed between the second extension part h 2   b  and the pairing second extension part h 2   a.    
     In the second extension part h 2   b , most of parts (areas) except for a part (area) facing the land r 2  are covered by the coverlay  4  and the part (area) facing the land r 2  is exposed from the opening  4   k  of the coverlay  4 . That is, the space, which is inevitably formed between the pair of lands r 1 , r 2  by the structure of the electrode terminals dga, dgb of the LED  1   g  of the second group, is effectively used to form the second extension part h 2   a  of the conduction pattern. 
     As described above, the second extension part h 2   b  is directly and electrically connected to the wiring pattern p 2  (refer to  FIG. 3B ) formed on the backside, through the through-hole th 1 . 
     By the above configuration, one electrode dga of the LED  1   g  of the second group is connected from the first and second extension parts h 1   a , h 2   a  to the wiring pattern p 4  and the other electrode dgb thereof is connected from the first and second extension parts h 1   b , h 2   b  to the wiring pattern p 2  (refer to  FIG. 3B ) on the backside through the through-hole th 1 . In the same manner, the other LEDs  1   g  of the second group are serially connected to the wiring pattern p 2 . 
     Likewise, the LED  1   r  of the first group and the LED  1   b  of the third group are soldered to the pair of corresponding lands r 1 , r 2 , the LED  1   r  of the first group is serially connected to the wiring pattern p 1  and the LED  1   b  of the third group is serially connected to the wiring pattern p 3 . 
     Thereby, the LEDs  1  of the same group in the four units are directly connected independently from the LEDs  1  of the other groups. 
     As described above, the LEDs  1   r  of the first group in the four units are directly connected through the wiring pattern p 1 , independently from the LEDs  1   g  of the second group and the LEDs  1   b  of the third group, as shown in  FIG. 3 . 
     Also, the LEDs  1   g  of the second group in the four units are directly connected through the wiring pattern p 2 , independently from the LEDs  1   r  of the first group and the LEDs  1   b  of the third group, as shown in  FIG. 3 . 
     Likewise, the LEDs  1   b  of the third group in the four units are directly connected through the wiring pattern p 3 , independently from the LEDs  1   r  of the first group and the LEDs  1   g  of the second group, as shown in  FIG. 3 . 
     Third, as shown in  FIG. 4 , the third extension part h 3   a  that is a wiring formed which extends from one corner of an opposite side to the side of the one land r 1  in the Y direction, at which the light guide plate  2  is arranged, to the opposite side to the light guide plate  2  toward the outer side. A leading end of the third extension part h 3   a  extends so that it is covered by the coverlay  4 , and a root part thereof (a side that is connected to the land r 1 ) is exposed from the opening  4   k  of the coverlay  4 . 
     A width of the third extension part h 3   a  is wider than that of the first extension part h 1   a  that is connected to the land r 1 . 
     Likewise, the third extension part h 3   b  that is a wiring is formed which extends from one corner of an opposite side to the side of the other land r 2  in the Y direction, at which the light guide plate  2  is arranged, to the opposite side to the light guide plate  2  toward the outer side. A leading end of the third extension part h 3   b  extends so that it is covered by the coverlay  4 , and a root part thereof (a side that is connected to the land r 2 ) is exposed from the opening  4   k  of the coverlay  4 . 
     A width of the third extension part h 3   b  is wider than that of the first extension part h 1   b  that is connected to the land r 2 . 
     Meanwhile, in  FIG. 4 , the configuration has been exemplified in which the leading ends of the third extension parts h 3   a , h 3   b  are electrically opened. However, the third extension parts may be electrically connected to the other conduction patterns by bypassing the leading ends thereof, like some of the third extension parts h 3   a , h 3   b  shown in  FIG. 3A . 
     Also, in this illustrative embodiment, the configuration has been exemplified in which the third extension parts h 3   a , h 3   b  are wider than the first extension parts h 1   a , h 1   b , respectively. However, the third extension parts h 3   a , h 3   b  may be configured to have areas larger than those of the first extension parts h 1   a , h 1   b , respectively. 
     As described above, the electrode terminals dga, dgb of the LED  1   g  of the second group are respectively soldered and fixed to the lands r 1 , r 2  of the FPC  3 , so that the LED  1   g  of the second group is mounted on the FPC  3 . 
     In the same manner, the electrode terminals dra, drb of the LED  1   r  of the first group and the electrode terminals dba, dbb of the LED  1   b  of the third group are also soldered and fixed to the pairs of corresponding lands r 1 , r 2 . 
     At this time, of the outlines of the pair of lands r 1 , r 2 , the lines i 1 , i 2 , i 3  (which are shown with the solid lines in  FIG. 4 ) of the land r 1  and the lines i 4 , i 5 , i 6  (which are shown with the solid lines in  FIG. 4 ) of the land r 2 , to which the first extension parts h 1   a , h 1   b , the second extension parts h 2   a , h 2   b  and the third extension parts h 3   a , h 3   b  are not connected, may be set as a basis of self-alignment as regards bi-axial directions (X and Y directions) when mounting the LED  1  ( 1   r ,  1   g ,  1   b ). Specifically, the lines i 1 , i 4  perpendicular to the X direction become a basis of the X direction and the lines i 2 , i 3 , i 5 , i 6  perpendicular to the Y direction becomes a basis of the Y direction. 
     According to the conduction patterns having the above configurations, the following effects can be realized. 
     As a first effect, since the leading ends of the first extension parts h 1   a , h 1   b  and the third extension parts h 3   a , h 3   b  and most of the second extension parts h 2   a , h 2   b  having the large width or large area are covered by the coverlay  4 , the peeling strength of the first, second and third extension parts h 1   a , h 1   b , h 2   a , h 2   b , h 3   a , h 3   b , the wiring patterns p 1  to p 4  and the lands r 1 , r 2  of the conduction patterns from the FPC  3  is improved and the peeling strength of the LED  1  from the FPC  3  is thus improved. As a result, it is possible to increase the mounting density of the LEDs  1  up to a level at which the coverlay  4  cannot be arranged between the adjacent LEDs  1 . Actually, as shown in  FIG. 3A , the openings  4   k  of the coverlay  4  are arranged between the adjacent LEDs  1 . 
     As a second effect, the two extension parts, i.e., the first extension parts h 1   a , h 1   b  and the second extension parts h 2   a , h 2   b , which extend forwards from the two corners of the two sides (upper side in  FIG. 4 ) of the lands r 1 , r 2  facing the light guide plate  2  to under the coverlay  4 , are arranged, so that it is possible to effectively suppress the wirings (conduction patterns) from being peeled off from (the front part of the base material  3   b  of) the FPC  3  during the process of abutting the LEDs  1  to the light guide plate  2  (refer to  FIG. 2 ) in an assembling process of the planar lighting device S. That is, the conduction patterns including the lands r 1 , r 2  are formed as shown in  FIG. 4 , so that the peeling strength of the LED  1  (the fixing strength of the LED  1  to the FPC  3 ) is secured and the strength is thus secured. 
     As a third effect, the third extension parts h 3   a , h 3   b  are formed to be wider or to have the larger area than the first extension parts h 1   a , h 1   b , so that it is possible to increase the peeling strength of the wiring (conduction pattern) at the rear side. 
     In back ground, an unbalance is caused because the parts corresponding to the second extension parts h 2   a , h 2   b  do not exist at the opposite side (the lower side in  FIG. 4 ) to the light guide plate  2 . In the above configuration, the unbalance of the fixing strengths between the light guide plate  2 -side and the opposite side to the light guide plate  2  (between the upper and lower sides in  FIG. 4 ) is decreased. Accordingly, it is possible to supplement the deficiency in the peeling strength at the rear of the opposite side (the lower side in  FIG. 4 ) to the light guide plate  2 . It is effective in case that the peeling strength of the conduction pattern at the opposite side to the light guide plate  2  is to be a problem. 
     As a fourth effect, in the outlines of the pair of lands r 1 , r 2  shown in  FIG. 4 , the parts (lines i 1  to i 6 ) (which are shown with the solid lines in  FIG. 4 ) to which the first extension parts h 1   a , h 1   b , the second extension parts h 2   a , h 2   b  and the third extension parts h 3   a , h 3   b  are not connected, may be set as the basis of self-alignment as regards the bi-axial directions (X and Y directions in  FIG. 4 ) when mounting the LED  1  on the FPC  3 . As described above, the lines i 1  and i 4  become a basis of the X direction and the lines i 2 , i 3 , i 5 , i 6  become the basis of the Y direction. Thereby, it is possible to secure the positional precision when mounting the LED  1 . 
     From the first to fourth effects, it is possible to secure the peeling strength of the LED  1  from the FPC  3  and to achieve the narrow-pitch arrangement of the LEDs  1  by designing the shapes of the lands r 1 , r 2  without arranging the coverlay  4  (the opening  4   k  of the coverlay  4  is arranged) between the lands r 1 , r 2  on which the LED  1  is mounted, i.e., between the adjacent LEDs  1 . Therefore, it is possible to form the LED mounting land pattern for narrow LED pitch. 
     Since it is possible to arrange more LEDs  1  in the limited space, it is possible to achieve the planar lighting device S of high brightness. 
     Since the break of the conduction pattern is prevented, it is possible to achieve the planar lighting device S having high reliability. 
     Since it is possible to perform the self-alignment with high precision when mounting the LED, it is possible to achieve the planar lighting device S capable of stably providing the high brightness and uniform lighting. 
     &lt;The Other Illustrative Embodiments&gt; 
     In the above illustrative embodiment, the LED  1  as the point-like light source has been exemplified. However, the light source having a shape other than the point-like light source may be used such as linear light source and planar light source as long as this disclosure can be applied thereto. 
     Also, in the above illustrative embodiment, the configuration has been exemplified in which the gap s 1  having the stripe shape is formed between the second extension parts h 2   a , h 2   b . However, the gap is not limited to the stripe shape. However, it is preferable to form a narrow gap between the second extension parts h 2   a , h 2   b  because it is possible to form the second extension parts h 2   a , h 2   b  having the larger area. 
     In the above illustrative embodiment, the FPC  3  has been exemplified as the substrate on which the light source is mounted. However, a substrate other than the FPC  3  may be adopted as long as this disclosure can be applied thereto. However, the FPC  3  is very suitable for the planar lighting device S having the narrow space. 
     In the above illustrative embodiment, the white LED has been exemplified as the LED  1 . However, an LED having a different color may be adopted as the LED  1 . 
     Also, in the above illustrative embodiment, this disclosure is applied to the planer light emitting device. However, this disclosure is applied to the substrate on which the light source is mounted. 
     Although the illustrative embodiment of this disclosure has been described, the description is only representative. Therefore, a variety of modifications and changes can be made within the scope of this disclosure. That is, this disclosure can be appropriately arbitrarily changed without changing the gist of this disclosure.