JP2018018813A - Planar luminaire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress occurrence of luminance unevenness.SOLUTION: A planar luminaire includes: a plurality of light sources arranged linearly and configured to emit light; and a light guide plate having a lateral surface arranged oppositely to the plurality of light sources, and an extension part extending in a direction separating from both ends of the lateral surface and in a direction separating from the plurality of light sources. On a boundary on the extension part between an emission range of a light source at an end part on the extension part and a region different from the emission range, a light emission region of the light guide plate contacts, or the light emission region is positioned on a reverse side to the extension part with respect to the boundary.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a planar lighting device.

  2. Description of the Related Art Conventionally, there is a planar illumination device that includes a light guide plate that emits light incident on a light incident surface from an LED (Light Emitting Diode) (see, for example, Patent Document 1).

JP 2008-298905 A

  Here, in the above-described planar illumination device, the light guide plate may have a shape in which at least two corners on the side where the plurality of LEDs 11 are arranged are cut out from four corners (four corners) of the rectangle. This is considered from the viewpoint of design properties including the object to be illuminated. For example, when the shape of the notched portion is a curved surface, and the LED is disposed so as to face the curved surface, a gap between the LED and the curved surface is generated, and uneven brightness may occur.

  This invention is made | formed in view of the above, Comprising: It aims at providing the planar illuminating device which can suppress generation | occurrence | production of a brightness nonuniformity.

  In order to solve the above-described problems and achieve the object, a planar illumination device according to one embodiment of the present invention is arranged in a straight line, and a plurality of light sources that emit light and the plurality of light sources are arranged to face each other. And a light guide plate having a extending portion extending in a direction away from both ends of the side surface and in a direction away from the plurality of light sources, and an emission range of the light source at the end portion on the extending portion side The light emitting region of the light guide plate is in contact with the boundary on the extending portion side between the region different from the emission range, or the light emitting region is located on the opposite side of the extending portion from the boundary.

  According to one embodiment of the present invention, occurrence of luminance unevenness can be suppressed.

FIG. 1 is a front view illustrating an example of the appearance of the planar illumination device according to the embodiment. 2 is a cross-sectional view taken along line AA in FIG. FIG. 3 is a top view of a light incident surface and a plurality of LEDs according to the embodiment. FIG. 4 is a diagram for explaining a range of positions in the x-axis direction where the end LEDs according to the embodiment are arranged. FIG. 5 is a diagram for explaining θ _{m according} to the embodiment. FIG. 6 is a top view showing the positional relationship among the light guide plate, the light emitting area, and the end LED in the planar illumination device according to Comparative Example 1. FIG. 7 is a top view showing the positional relationship among the light guide plate, the light emitting area, and the end LED in the planar lighting device according to Comparative Example 2. FIG. 8 is a top view illustrating a positional relationship among the light guide plate, the light emitting area, and the end LED in the planar lighting device according to the first modification of the embodiment. FIG. 9 is a top view illustrating a positional relationship among the light guide plate, the light emitting area, and the end LED in the planar lighting device according to the second modification of the embodiment. FIG. 10 is a diagram for explaining an emission range until the light emitted from the end LED according to the second modification reaches the light guide plate.

  Hereinafter, a planar illumination device according to an embodiment will be described with reference to the drawings. In addition, the relationship of the dimension of each element in a drawing, the ratio of each element, etc. may differ from reality. Even between the drawings, there are cases in which portions having different dimensional relationships and ratios are included.

(Embodiment)
FIG. 1 is a front view illustrating an example of the appearance of the planar illumination device according to the embodiment. As shown in the example of FIG. 1, the shape of the planar illumination device 10 according to the embodiment is substantially rectangular when viewed from above. One end side in the longitudinal direction (y-axis direction) of the planar illumination device 10 is covered with a light shielding sheet 30 including a first light shielding sheet 30a and a second light shielding sheet 30b. Further, the other end side in the longitudinal direction of the planar illumination device 10 is covered with a light shielding sheet 31. The light shielding sheet 30 and the light shielding sheet 31 are integrally formed. The planar illumination device 10 emits light from a light emitting region (also referred to as a light emitting area) 90 that is not covered with the light shielding sheets 30 and 31. That is, the light emitting area 90 is defined by the light shielding sheets 30 and 31. The planar illumination device 10 according to the present embodiment is used as a backlight of a liquid crystal display device. Such a liquid crystal display device is used, for example, in a smartphone.

  Here, in FIG. 1, the light shielding sheet 30 is wider than the light shielding sheet 31. This is because the light shielding sheet 31 covers a light guide plate 12, a diffusion sheet 15, and a prism sheet 16, which will be described later, existing below the light shielding sheet 31, while the light shielding sheet 30 is described later, which exists below the light shielding sheet 30. This is to cover a relatively wide area including the LED 11 and the FPC 13 described later in addition to the light guide plate 12, the diffusion sheet 15, and the prism sheet 16.

  2 is a cross-sectional view taken along line AA in FIG. As shown in FIG. 2, the planar illumination device 10 includes an LED 11, a light guide plate 12, an FPC 13, a diffusion sheet 15, a prism sheet 16, a frame 17, a reflection sheet 18, a fixing member 20, a first connection member 21, and a second connection. It has the member 22, the double-sided tape 23, and the light shielding sheet 30.

  The FPC 13 is a strip-shaped substrate that extends in the short direction of the planar illumination device 10 (the x-axis direction, the long-side direction of the light incident surface 12c described later). The FPC 13 has two main surfaces 13a and 13b. The two main surfaces 13 a and 13 b are strip-shaped surfaces extending in the short direction of the planar illumination device 10. Of the two main surfaces 13a and 13b, one main surface 13a is a mounting surface on which the LED 11 is mounted. For this reason, “main surface 13a” may be referred to as “mounting surface 13a”. On the mounting surface 13a, a surface opposite to the light emitting surface 11a of the LED 11 is placed. The LED 11 is driven by the control of a drive circuit (not shown) via the FPC 13 to emit light.

  The light guide plate 12 is formed in a rectangular shape in a top view using a transparent material (for example, polycarbonate resin). The light guide plate 12 has main surfaces 12a and 12b and side surfaces (end surfaces) 12c. The side surface 12 c is a light incident surface that is a side surface on the side where the LED 11 is disposed, and is a strip-shaped light incident surface that extends in the short direction of the planar illumination device 10. Therefore, in the following description, “side surface 12c” may be referred to as “light incident surface 12c”. The light emitted from the LED 11 is incident on the light incident surface 12c. That is, the light incident surface 12c is incident on the light emitted from the LED 11. One main surface 12a of the two main surfaces 12a and 12b is an emission surface from which light incident from the light incident surface 12c (light emitted from the LED 11) is emitted. Therefore, in the following description, “main surface 12a” may be referred to as “exit surface 12a”. On the main surface 12b side that is the surface opposite to the exit surface 12a of the light guide plate 12, for example, an optical path changing pattern composed of a plurality of dots is formed. By forming the optical path changing pattern, the traveling direction of the light traveling in the light guide plate 12 is changed, and light is emitted from the emission surface 12a. That is, the planar illumination device 10 according to the embodiment is a so-called edge light type illumination device. In addition, as the planar lighting device 10, light is emitted from the light emitting region 90 of the emission surface 12a. That is, the light emitting region 90 emits light incident from the light incident surface 12c.

  The LED 11 is a point light source (point light source). The LED 11 is, for example, a pseudo white LED composed of a blue LED and a yellow phosphor. The LED 11 is a so-called top view type LED that is formed in a substantially rectangular parallelepiped shape as a whole and has a light emitting surface 11a and a surface placed on the mounting surface 13a of the FPC 13 on the opposite side of the light emitting surface 11a. The plurality of LEDs 11 are mounted on the mounting surface 13a at predetermined intervals along the long side direction (x-axis direction) of the mounting surface 13a. Accordingly, the plurality of LEDs 11 are spaced apart from each other along the long side direction (x-axis direction) of the light incident surface 12c with the light emitting surface 11a facing the light incident surface 12c of the light guide plate 12. Will be placed. In addition, although mentioned later, several LED11 is arrange | positioned linearly along the side surface 40 which is a plane mentioned later among the light-incidence surfaces 12c. The LED 11 may be a side view type LED.

  The frame 17 accommodates the LED 11, the light guide plate 12, the FPC 13, the diffusion sheet 15, the prism sheet 16, the reflection sheet 18, the fixing member 20, the first connection member 21, the second connection member 22, and the double-sided tape 23. The frame 17 is, for example, a stainless steel sheet metal frame having high rigidity and light reflectivity. The frame 17 has a side wall 17a and a bottom portion 17b.

  The bottom portion 17 b has a shape that extends along the main surface 12 b of the light guide plate 12. The bottom 17b has a floor surface 17d that is a surface on the light guide plate 12 side. The floor surface 17d has a flat surface 17d_1 and a concave surface 17d_2 of a concave portion 17c described later. The light guide plate 12 and the LEDs 11 are placed on the plane 17d_1. The side wall 17a is integrated with the bottom portion 17b in the direction in which light is emitted from the bottom portion 17b along the long side of the light incident surface 12c of the light guide plate 12 (normal direction of the plane 17d_1 of the floor surface 17d, plus direction of the z axis). The part that stands up. The side wall 17a has a side surface 17e which is an inner surface. Moreover, the bottom part 17b has the recessed part 17c. The concave portion 17c escapes the lower end portion of the FPC 13 formed so as to be recessed in the direction opposite to the direction in which light is emitted along the side surface 17e from the portion on the side surface 17e side of the floor surface 17d (the negative direction of the z axis). It is a member. The width of the concave portion 17c is narrow so that the larger first connecting member 21 is disposed on the flat surface 17d_1 of the floor surface 17d. The recess 17c has a concave surface 17d_2.

  The reflection sheet 18 reflects the light leaked from the main surface 12b opposite to the emission surface 12a and returns it to the light guide plate 12 again. The reflection sheet 18 is disposed between the main surface 12b of the light guide plate 12 and the floor surface 17d while being fixed on the floor surface 17d (specifically, the flat surface 17d_1 of the floor surface 17d) by the double-sided tape 23. .

  The double-sided tape 23 is, for example, a white double-sided tape. One surface of the double-sided tape 23 is affixed to a part of the reflection sheet 18, and the other surface is affixed to the floor surface 17d (specifically, the flat surface 17d_1 of the floor surface 17d). Thereby, the double-sided tape 23 fixes the reflective sheet 18 on the floor surface 17d.

  The fixing member 20 fixes the FPC 13 to the side surface 17e of the frame 17. The fixing member 20 is, for example, a double-sided tape. By fixing one surface of the fixing member 20 to the main surface 12b of the FPC 13 and the other surface to the side surface 17e, the FPC 13 is fixed to the side surface 17e.

  The first connecting member 21 is disposed between the light guide plate 12 and the LED 11 and the floor surface 17d (specifically, the flat surface 17d_1 of the floor surface 17d), and optically or structurally connects the light guide plate 12 and the LED 11. . Explaining with a specific example, the first connecting member 21 connects the light incident surface 12c of the light guide plate 12 and the light emitting surface 11a of the LED 11 in a state where the optical axis of the light guide plate 12 and the optical axis of the LED 11 are aligned. Connect. The 1st connection member 21 is a strip-shaped single-sided tape, and contains the adhesion layer (adhesive) 21a and the base material 21b.

  The base material 21b is, for example, PET, and the adhesive layer 21a is, for example, silicon or acrylic. The adhesive layer 21a adheres to at least part of the main surface 12b of the light guide plate 12 near the LED 11 and also adheres to at least part of the surface of the LED 11 on the floor surface 17d side near the light guide plate 12. Thereby, at least a part of the main surface 12 b of the light guide plate 12 and at least a part of the surface of the LED 11 on the floor surface 17 d side are attached to the first connecting member 21. As a result, the first connecting member 21 connects the light incident surface 12 c of the light guide plate 12 and the light emitting surface 11 a of the LED 11.

  Here, the case where the 1st connection member 21 is a double-sided tape is demonstrated. In this case, since the light guide plate 12 and the LED 11 are fixed to the floor surface 17d, if any force is applied to the planar illumination device 10 from the outside, the light guide plate 12 and the LED 11 can release the force. It is conceivable that it will be damaged. However, since the 1st connection member 21 which concerns on this embodiment is a single-sided tape, since the light-guide plate 12 and LED11 are not fixed with respect to the floor surface 17d, the light-guide plate 12 and LED11 escape the force from the outside. Can do. For this reason, according to the planar illuminating device 10 which concerns on this embodiment, generation | occurrence | production of the damage of the light-guide plate 12 and LED11 can be suppressed.

  The first connecting member 21 has a member that absorbs light or a member that reflects light. For example, when the first connecting member 21 has a member that reflects light, the light emitted from the light emitting surface 11a of the LED 11 is reflected and returned to the light guide plate 12 again, so that the luminance can be improved. .

  The 2nd connection member 22 is arrange | positioned with respect to the light-guide plate 12 and LED11 on the opposite side to the 1st connection member 21, and connects the light-guide plate 12 and LED11 optically or structurally. Explaining with a specific example, the light incident surface 12c of the light guide plate 12 and the light emitting surface 11a of the LED 11 are connected. The 2nd connection member 22 is arrange | positioned between the diffusion sheet 15 mentioned later, the light-guide plate 12, and LED11. The second connecting member 22 is, for example, a double-sided tape. One surface of the second connecting member 22 is affixed to at least a part of the light exit surface 12a of the light guide plate 12 near the LED 11 and is close to the light guide plate 12 on the surface opposite to the surface of the LED 11 on the floor surface 17d side. Affixed to at least a part of Thereby, at least a part of the emission surface 12a of the light guide plate 12 and at least a part of the surface of the LED 11 opposite to the surface on the floor surface 17d side are attached to the second connecting member 22. As a result, the second connecting member 22 connects the light incident surface 12 c of the light guide plate 12 and the light emitting surface 11 a of the LED 11.

  The other surface of the second connecting member 22 is attached to at least a part of the diffusion sheet 15 on the side wall 17a side. Thereby, the 2nd connection member 22 fixes the diffusion sheet 15 to the light-guide plate 12 and LED11. Accordingly, since the second connecting member 22 can suppress the diffusion sheet 15 from floating from the light guide plate 12, it suppresses deterioration of luminance characteristics such as luminance and luminance distribution of light emitted from the light emitting region 90. can do.

  The diffusion sheet 15 is disposed on the emission surface 12a side of the light guide plate 12, and diffuses light emitted from the emission surface 12a. Explaining with a specific example, the diffusion sheet 15 is arranged so as to cover at least a part of the light exit surface 12a and the surface of the LED 11 opposite to the floor surface 17d side, and the light emitted from the light exit surface 12a. To diffuse. As described above, the diffusion sheet 15 is fixed to the light guide plate 12 and the LED 11 by the second connecting member 22.

  The prism sheet 16 is disposed on a surface opposite to the surface facing the emission surface 12a of the diffusion sheet 15, and performs light distribution control of light diffused by the diffusion sheet 15 to perform light distribution control. Is emitted.

  The light shielding sheet 30 is disposed so as to cover a part of the prism sheet 16 on the side wall 17 a side, and shields light emitted from a part of the emission surface 12 a of the light guide plate 12.

  The light shielding sheet 30 includes a first light shielding sheet 30a and a second light shielding sheet 30b. For example, the first light shielding sheet 30a is a single-sided tape that can shield light. One end side of the first light shielding sheet 30 a is attached to the outer surface of the side wall 17 a of the frame 17. Further, the other end side of the first light shielding sheet 30 a is attached to the side wall 17 a side of the prism sheet 16. For example, the 2nd light shielding sheet 30b is a double-sided tape which can block light. Of the two main surfaces of the second light shielding sheet 30b, one main surface is attached to the other end of the first light shielding sheet 30a, and the other main surface uses the planar illumination device 10 as a backlight. Affixed to the liquid crystal display device.

Next, with reference to FIG. 3, an example of arrangement | positioning of several LED11 with respect to the light-incidence surface 12c which concerns on this embodiment is demonstrated. FIG. 3 is a top view of a light incident surface and a plurality of LEDs according to the embodiment. As illustrated in the example of FIG. 3, the light incident surface 12c includes a side surface 40 and extending portions 41a and 41b. That is, the side surface 40 is formed on one side surface of the light guide plate 12, the extending portion 41 a is formed on one end side in the x-axis direction of the side surface 40, and the extending portion 41 b is formed on the other end side in the x-axis direction of the side surface 40. Is done. In the example of FIG. 3, the surface of the light incident surface 12c in the x-axis direction that has an x coordinate in the range of “0” or more and less than “x ₁₁ ” is the extending portion 41a, and the x coordinate is “x ₁₁ ” or more and “ x _l3 "is the plane of the range of a side 40, x-coordinate plane in the range greater following" _{x l4} "than" _{x l3} "is extending portion 41b.

  Further, as shown in FIG. 3, the light guide plate 12 has the light emitting region 90 described above. The light emitting region 90 has a substantially rectangular shape in which at least two corners 90a and 90b on the light incident surface 12c side are rounded. The corner portion 90a is formed at a position corresponding to the extending portion 41a, and the corner portion 90b is formed at a position corresponding to the extending portion 41b.

  The side surface 40 is a plane. That is, the side surface 40 is a planar surface. In the present embodiment, the plurality of LEDs 11 are arranged linearly along the side surface 40 so as to face the side surface 40. That is, the plurality of LEDs 11 are arranged side by side in the x-axis direction. Therefore, in the present embodiment, the x axis is an axis extending in the direction in which the plurality of LEDs 11 are arranged. The x axis is an example of a first axis.

  The extending portion 41a extends from one end of the side surface 40 (one end of the side surface 40 in the x-axis direction) in a direction away from the extending portion 41b (a direction away from the side surface 40) and in a direction away from the plurality of LEDs 11. The extending portion 41b extends from the other end of the side surface 40 (the other end in the x-axis direction of the side surface 40) in a direction away from the extending portion 41a (a direction away from the side surface 40) and in a direction away from the plurality of LEDs 11. As described above, the extending portions 41 a and 41 b extend in a direction away from both ends of the side surface 40 (both ends in the x-axis direction of the side surface 40) and in a direction away from the plurality of LEDs 11. That is, the pair of extending portions 41 a and 41 b expands in a direction away from both ends of the side surface 40.

  Therefore, the light guide plate 12 according to the present embodiment is not a complete rectangular shape in a top view, and at least two corners on the side where the plurality of LEDs 11 are arranged are cut out from four corners (four corners) of the rectangle. It can be said that it is a shape.

  Next, with reference to FIG. 4, the range of the position of the direction of the x-axis where LED11 of an edge part is arrange | positioned among several LED11 arrange | positioned linearly is demonstrated. In the following description, the range of positions where the LED 11 on the extending portion 41a side (the leftmost LED 11 in FIG. 3) is arranged as the LED 11 at the end will be described. However, the LED 11 on the extending portion 41a side described below will be described. Based on the same principle as that for defining the range of positions, the range of positions for the LED 11 on the extending portion 41b side (the rightmost LED 11 in FIG. 3) can be defined.

  FIG. 4 is a diagram for explaining a range of positions in the x-axis direction in which the end LEDs are arranged. As shown in FIG. 4, the light emitting surface 11a and the light incident surface 12c of the LED 11 at the end on the extending portion 41a side (the leftmost LED 11 in FIG. 4 (hereinafter referred to as the end LED 11)) are in contact, and The case where the length in the x-axis direction of the light emitting surface 11a that emits light coincides with the length in the x-axis direction of the end LED 11 will be described.

The position (x coordinate) in the x-axis direction where the side surface 11c on the extending portion 41a side of the end LED 11 is disposed is _defined as x _led . In this case, the position of the light emitting surface 11a of the end LED 11 closest to the extending portion 41a is represented by 10 (x _led , 0), and the range of x _led is represented by the following formula (1).

However, _x11 in the formula (1) is represented by the following formula (2).

However, _{R s} in formula (2) is an arc extending portion 41a forms a radius of a circle including the circumference in the xy plane including the optical axis 11b of the end LED 11. The xy plane is a plane including the x axis and the y axis that intersects (specifically, orthogonal) to the x axis. The y axis is an example of a second axis. In addition, x _rs and y _rs in the expression (2) are the x coordinate and the y coordinate of the coordinates of the center P _rs of the circle including the circular arc formed by the extending portion 41a in the xy plane including the optical axis 11b of the end LED 11 in the circumference. It is. _{That, x rs} indicates the position of the center _{P rs} of the circle in the _{x-axis, y rs} indicates the position of the center _{P rs} of the circle in the y-axis.

That is, the point l1 ( _xl1 , 0) illustrated in FIG. 4 indicates the end of the side surface 40 on the extending portion 41a side.

Moreover, _x12 in Formula (1) is represented by the following formula _| equation (3).

Moreover, _xc1 in Formula (3) is represented by the following formula (4).

However, _{R l} in formula (4) is the radius of the circle containing the circular arc formed by the corner portion 90a of the light emitting area 90 in the xy plane including the optical axis 11b of the end LED11 circumferentially. In addition, x _rl in Expression (4) is an x coordinate of the coordinates of the center P _rl of the circle including the arc formed by the corner portion 90a of the light emitting area 90 in the xy plane including the optical axis 11b of the end LED 11 on the circumference. . That is, x _rl indicates the position of the center P _rl of the circle including the arc formed by the corner portion 90a of the light emitting area 90 on the x axis.

Further, θ _m in the equation (4) is represented by the following equation (5).

However, n in the formula (5) is the refractive index of the light guide plate 12. That is, θ _m assumes a case where the light emitted from the end LED 11 is incident on the side surface 40 in a direction parallel to the side surface 40, and indicates a critical angle.

FIG. 5 is a diagram for explaining θ _{m according} to the embodiment. For example, as shown in FIG. 5, θ _m is incident on the side surface 40 of the light guide plate 12 in the xy plane 50 including the optical axis 11 b of the end LED 11, and the emission range 51 and the emission of light traveling in the light guide plate 12. This is the angle between each of the boundaries 53 and 54 with an area 52 (an area that is not the emission range 51) different from the range 51 and the optical axis 11 b of the end LED 11. Here, the emission range 51 is a range in the light guide plate 12 of light incident on the side surface 40 from the end LED 11. In FIG. 5, of the two boundaries 53 and 54, the boundary 53 is a boundary on the extending portion 41 a side. As described above, the range in which the light incident on the side surface 40 from the end LED 11 travels in the light guide plate 12 is the emission range 51. The emission range 51 is a direct light from the LED 11 in the light guide plate 12. The range in which the reflected light travels is not included in the emission range 51.

また、式（６）におけるｙ_ｒｌは、端部ＬＥＤ１１の光軸１１ｂを含むｘｙ平面における発光エリア９０の角部９０ａが成す円弧を円周に含む円の中心Ｐ_ｒｌの座標のｙ座標である。すなわち、ｙ_ｒｌは、ｙ軸における、発光エリア９０の角部９０ａが成す円弧を円周に含む円の中心Ｐ_ｒｌの位置を示す。 Moreover, y _c1 in the formula (3) is represented by the following formula (6).

In addition, y _rl in Equation (6) is the y coordinate of the coordinates of the center P _rl of the circle including the arc formed by the corner 90a of the light emitting area 90 in the xy plane including the optical axis 11b of the end LED 11 on the circumference. . That is, y _rl indicates the position of the center P _rl of the circle including the circular arc formed by the corner portion 90a of the light emitting area 90 on the y axis.

As can be seen from the equations (3) to (6), the point l2 ( _xl2 , 0) shown in FIG. 4 is a point where the boundary 53 and the side surface 40 intersect when the boundary 53 is in contact with the light emitting region 90. It becomes. Further, as can be seen from the equations (4) and (6) described above, the point C1 (x _c1 , y _c1 ) shown in FIG. 4 is a contact point between the boundary 53 and the light emitting region 90.

From the _above, the range _{of x of led} is represented by the formula (1) described above, i.e., if it is within the _{x l1} or _{x l2} following ranges 70 shown in FIG. 4, the end LED11 is a plane It faces the side surface 40. Further, when x _led is within the range 70, the light emitting region 90 is in contact with the boundary 53 or the light emitting region 90 is located on the opposite side of the extending portion 41a from the boundary 53. The light emitted from the LED 11 will surely reach the corner 90 a of the light emitting region 90.

  Here, the planar illumination device 100 according to the comparative example 1 and the planar illumination device 101 according to the comparative example 2 are described with reference to FIGS. The lighting devices 100 and 101 are compared. FIG. 6 is a top view showing the positional relationship among the light guide plate, the light emitting area, and the end LED in the planar illumination device according to Comparative Example 1. FIG. 7 is a top view showing the positional relationship among the light guide plate, the light emitting area, and the end LED in the planar lighting device according to Comparative Example 2.

  As shown in FIG. 6, in the planar lighting device 100 according to the comparative example 1, the end LED 11 is disposed to face the extending portion 41a. In this case, an air layer gap 100a exists between the end LED 11 and the extending portion 41a, and the gap 100a is relatively large. The light emitted from the end LED 11 spreads in the vertical direction (z-axis direction) and travels. For this reason, when the gap 100a is large, a part of the light emitted from the end LED 11 is not incident on the extending portion 41a, and proceeds to the upper side and the lower side of the extending portion 41a. Therefore, the planar illumination device 100 according to the comparative example 1 does not have good luminous efficiency.

  Further, the light emitting surface 11a of the end LED 11 has a portion where a gap 100a exists between the portion in contact with the extending portion 41a and the extending portion 41a. For this reason, the amount of light incident on the extending portion 41a from a location in contact with the extending portion 41a is different from the amount of light incident on the extending portion 41a from a location where a gap 100a exists between the extending portion 41a. . As described above, since the amount of light incident on the extending portion 41a from the end LED 11 is different for each portion of the light emitting surface 11a, luminance unevenness occurs in the light emitted from the corner portion 90a of the light emitting region 90 facing the end LED 11. There is a case.

  As shown in FIG. 7, in the planar lighting device 101 according to the comparative example 2, the light guide plate 12 includes an extending portion 41 c in which a rectangular corner portion is chamfered. In the planar illumination device 101 according to the comparative example 2, the end LED 11 is disposed to face the extending portion 41c. As described above, when the end LED 11 is disposed in the chamfered extending portion 41c, the distance d between the light emitting surface 11a and the light emitting region 90 of the end LED 11 varies depending on the position on the light emitting surface 11a. For this reason, the susceptibility to light leakage in the light emitting region 90 varies depending on the position on the light emitting surface 11a, and uneven brightness may occur in the light emitted from the corner 90a of the light emitting region 90 facing the end LED 11. is there.

  Further, in order to make the luminance unevenness inconspicuous, it is also conceivable to increase the distance d and relatively reduce the difference in the amount of light incident on the extending portion 41c that is different for each position on the light emitting surface 11a. However, in this case, since the distance d becomes long, the outer shape of the planar lighting device 101 becomes large, and it is difficult to achieve a so-called narrow frame.

  Further, when the end LED 11 is disposed so as to contact the boundary point 41d between the extending portion 41c and the side surface 40 and to contact either the extending portion 41c or the side surface 40, the one not in contact A gap is generated between the surface and the end LED 11. For this reason, luminous efficiency is not good. Further, since the distance between the end LED 11 and the light incident surface 12c of the light guide plate 12 varies depending on the position on the light emitting surface 11a, the luminance unevenness is caused in the light emitted from the corner portion 90a of the light emitting region 90 facing the end LED 11. May occur.

  From the above, it can be seen that the end LED 11 is preferably not disposed in the extending portions 41a and 41c from the viewpoint of improving luminous efficiency and suppressing luminance unevenness.

  Therefore, in the planar lighting device 10 according to the embodiment, the end LED 11 is disposed to face the side surface 40. That is, all the LEDs 11 (a plurality of LEDs 11) are arranged linearly facing only the side surface 40. Thereby, in all the LEDs 11, the distance between the light emitting surface 11a and the side surface 40 is substantially the same at any position on the light emitting surface 11a.

  In the planar lighting device 10 according to the embodiment, the light emitting region 90 extends to the extending portions 41a and 41b side from the end LED 11 (side surface 40) in the direction (x-axis direction) in which the plurality of LEDs 11 are arranged. ing. That is, the light emitting region 90 extends to the extending portions 41 a and 41 b side from the planar side surface 40 in the direction in which the planar side surface 40 extends (x-axis direction). However, even if the light emitting region 90 extends toward the extending portions 41a and 41b, the light from the end LED 11 reliably reaches the extending region.

  Explaining with a specific example, in the planar illumination device 10 according to the embodiment, the light emitting region 90 is in contact with the boundary 53 or the light emitting region 90 is located on the opposite side of the extending portion 41a from the boundary 53. It becomes. For this reason, the light emitted from the end LED 11 reliably reaches the corner 90 a of the light emitting region 90.

  The planar lighting device 10 according to the present embodiment has been described above. From the above, in the planar illumination device 10 according to the embodiment, the light emission efficiency can be improved, and the occurrence of luminance unevenness can be suppressed.

(First Modification of Embodiment)
In the above-described embodiment, the case where the corner portion 90a is rounded and the outer shape of the corner portion 90a is a curve in the xy plane has been described. However, the light guide plate 12 may have a shape in which a rectangular corner is chamfered. Therefore, such an embodiment will be described as a first modification of the embodiment.

  FIG. 8 is a top view illustrating a positional relationship among the light guide plate, the light emitting area, and the end LED in the planar lighting device according to the first modification of the embodiment. As shown in the example of FIG. 8, the planar lighting device 10 a according to the first modified example has a light guide plate 12 having a extending portion 41 e that is a flat surface with a corner portion corresponding to the corner portion 90 a of the light emitting region 90 chamfered. Is provided.

  Moreover, the corner | angular part corresponding to the corner | angular part 90b of the light emission area | region 90 is chamfered similarly to the extending part 41e mentioned above, and the light-guide plate 12 has the extending part 41f which is a plane.

  The extending portion 41 e extends from one end of the side surface 40 (one end of the side surface 40 in the x-axis direction) in a direction away from the extending portion 41 f (a direction away from the side surface 40) and in a direction away from the plurality of LEDs 11. The extending portion 41f extends from the other end of the side surface 40 (the other end of the side surface 40 in the x-axis direction) in a direction away from the extending portion 41e (a direction away from the side surface 40) and in a direction away from the plurality of LEDs 11. That is, the extending portions 41 e and 41 f extend in a direction away from both ends of the side surface 40 (both ends in the x-axis direction of the side surface 40) and in a direction away from the plurality of LEDs 11.

Also in the planar lighting device 10a according to the first modification, as in the planar lighting device 10 according to the above-described embodiment, x _led is a range represented by the above-described formula (1), that is, FIG. In the range 70 from _{x11 to x12} shown in FIG.

X _l2 according to the first modified example is the same as x _l2 according to the embodiment described above. On the other hand, x _{11 according} to the first modification is the x coordinate of the intersection l 1 between the straight line formed by the extending portion 41 e and the side surface 40 in the xy plane including the optical axis 11 b of the end LED 11.

  As described above, the range of the position in the x-axis direction where the LED 11 on the extending portion 41e side is disposed has been described, but the LED 11 on the extending portion 41f side is based on the same principle as that defining the range of the position of the LED 11 on the extending portion 41e side. Also, the range of positions to be arranged can be defined.

If x _{of led} is within _{x l1} or _{x l2} following ranges 70 shown in FIG. 8, the end LED11 will be opposed to the side surface 40 is planar. Further, when x _led is within the range 70, the light emitting region 90 is in contact with the boundary 53, or the light emitting region 90 is positioned on the opposite side of the extending portion 41e from the boundary 53. The light emitted from the end LED 11 on the side of the portion 41 e surely reaches the corner portion 90 a of the light emitting region 90. Similarly, the light emitted from the end LED 11 on the extending portion 41 f side surely reaches the corner portion 90 b of the light emitting region 90.

  The planar lighting device 10a according to the first modification of the embodiment has been described above. From the above, in the planar illumination device 10a according to the first modification, the light emission efficiency can be improved and the occurrence of uneven brightness can be suppressed, similarly to the planar illumination device 10 according to the above-described embodiment. be able to.

(Second Modification of Embodiment)
In the embodiment and the first modification described above, the case where the LED 11 and the light guide plate 12 are in contact with each other has been described. However, the LED 11 and the light guide plate 12 may be separated from each other. Therefore, such an embodiment will be described as a second modification of the embodiment.

FIG. 9 is a top view illustrating a positional relationship among the light guide plate, the light emitting area, and the end LED in the planar lighting device according to the second modification of the embodiment. As shown in the example of FIG. 9, the planar illumination device 10 b according to the second modified example has a planar shape according to the above-described embodiment in that a plurality (all) of LEDs 11 are separated from the side surface 40 by a distance d _1. Different from the lighting device 10. That is, as shown in FIG. 9, the position of the light emitting surface 11a of the end LED 11 closest to the extending portion 41a is represented by l7 (x _led , −d ₁ ).

FIG. 10 is a diagram for explaining an emission range until the light emitted from the end LED according to the second modification reaches the light guide plate. In the second modification, a range in which light having a light intensity equal to or greater than a predetermined value out of the light emitted from the end LED 11 is defined as an emission range 55. For example, as shown in FIG. 10, in the xy plane 50 including the optical axis 11 b of the end LED 11, the light emission range 55 emitted from the end LED 11 is different from the emission range 55 (region that is not the emission range 55). two angle between the optical axis 11b of the border 57, 58 respectively and the end LED11 with 56, a theta _alpha. Thus, theta _alpha, the angle of the angle formed between the optical axis 11b and the boundary 57, 58 each end LED 11. That is, the light with the luminous intensity from the end LED 11 having a predetermined value or more proceeds with a spread of the angle θ _α with respect to the optical axis 11 b until reaching the light guide plate 12. Here, in FIG. 10, of the two boundaries 57 and 58, the boundary 57 is a boundary on the extending portion 41 a side. Incidentally, concrete Shimese the angle theta _alpha as half-width (half value angle), is generally a 60 °.

In the second modification, x _led is not within the range represented by the above-described formula (1), but within the range represented by the following formula (7). This is different from the modified example.

Here, _x15 in the formula (7) is represented by the following formula (8).

Further, in the second modification, θ _m is different from the above-described embodiment and the first modification in that it is expressed by the following expression (9) instead of the above-described expression (5).

When x _led is within the range 81 of x _{11 to} x ₁₅ shown in FIG. 9, the end LED 11 _faces the side surface 40 that is a plane. Further, when x _led is within the range 81, the light emitting region 90 is in contact with the boundary 53 or the light emitting region 90 is located on the opposite side of the extending portion 41e from the boundary 53. The light emitted from the end LED 11 on the side of the portion 41 e surely reaches the corner portion 90 a of the light emitting region 90. Similarly, the light emitted from the end portion LED 11 on the extending portion 41 f side surely reaches the corner portion 90 b (see FIG. 3) of the light emitting region 90.

  The planar lighting device 10b according to the second modification of the embodiment has been described above. From the above, in the planar illumination device 10b according to the second modification, the luminous efficiency is improved in the same manner as the planar illumination device 10 according to the above-described embodiment and the planar illumination device 10a according to the first modification. This can be improved, and the occurrence of uneven brightness can be suppressed.

In the above-described embodiment and various modifications, the case where the light incident prism is not formed on the side surface 40 of the light guide plate 12 has been described. However, the light incident prism may be formed on the side surface 40. In this case, the above-described θ _m is obtained by optical simulation.

  The embodiments and the modifications of the embodiments have been described above, but the present invention is not limited to the embodiments and the modifications. What was comprised combining each component mentioned above suitably is also contained in this invention. Further effects and modifications can be easily derived by those skilled in the art. Therefore, the broader aspect of the present invention is not limited to the above-described embodiment, and various modifications can be made.

10 Planar illumination device 11 LED (light source)
11a Light emission surface 12 Light guide plate 12c Side surface (end surface)
40 Side surface 41a, 41b, 41e, 41f Extension part 53, 57 Boundary 90 Light emitting area 90a, 90b Corner part

Claims (7)

A plurality of light sources arranged in a straight line and emitting light;
A light guide plate having a side surface on which the plurality of light sources are opposed to each other, and an extending portion extending in a direction away from both ends of the side surface and in a direction away from the plurality of light sources,
With
The light emitting region of the light guide plate is in contact with the boundary of the extending portion side between the emission range of the light source at the end on the extending portion side and the region different from the emitting range, or the extending portion is more than the boundary. The light emitting area is located on the opposite side,
Planar lighting device.   2. The planar illumination device according to claim 1, wherein the light emitting region extends to the extending portion side with respect to the light source at the end portion in a direction in which the plurality of light sources are arranged.   The light emitting region is in contact with the boundary between the emission range and the region different from the emission range in the light guide plate of the light incident on the side surface from the light source at the end, or the extending portion is more than the boundary The planar illumination device according to claim 1, wherein the light emitting region is located on a side opposite to the side. A plurality of light sources that emit light;
A light guide plate having an end surface on which light emitted from the plurality of light sources is incident, and a light emitting region that emits light incident from the end surface;
With
The end surface has a planar side surface and a pair of extending portions that expand in a direction away from both ends of the side surface,
The light emitting region extends in the extending portion side of the planar side surface in the direction in which the planar side surface extends,
The plurality of light sources are disposed to face only the planar side surface.
Planar lighting device.   The planar illumination device according to any one of claims 1 to 4, wherein a light incident prism is formed on the side surface. The planar shape according to any one of claims 1 to 5, wherein a position x _led of the light source at the end on a first axis extending in a direction in which the plurality of light sources are arranged is within a range represented by the expression (1). Lighting device.

However, _x11 in Formula (1) is represented by Formula (2).

However, R _s in the formula (2) is a plane including the optical axis of the light source at the end, and the extension in the plane including the first axis and the second axis intersecting the first axis. This is the radius of a circle that includes the arc formed by the part on the circumference. Moreover, _xrs in Formula (2) shows the position of the center of the circle on the first axis. Moreover, _yrs in Formula (2) shows the position of the center of the circle on the second axis.
Moreover, _x12 in Formula (1) is represented by Formula (3).

However, _xc1 in Formula (3) is represented by the following Formula (4).

However, R _l in formula (4) is the radius of the circle containing the circular arc corner portion of the light-emitting region in said plane forms the circumference. In addition, x _rl in Equation (4) indicates the position of the center of a circle that includes the arc formed by the corner of the light emitting region on the first axis. Further, θ _m in the equation (4) is represented by the following equation (5).

However, n in Formula (5) is the refractive index of the said light-guide plate.
Moreover, y _c1 in the formula (3) is represented by the following formula (6).

However, y _rl in Equation (6) indicates the position of the center of a circle that includes the arc formed by the corner of the light emitting region on the second axis. The planar shape according to any one of claims 1 to 5, wherein a position x _led of the light source at the end portion in a first axis extending in a direction in which the plurality of light sources are arranged is within a range represented by Expression (7). Lighting device.

However, _x11 in Expression (7) is expressed by Expression (8).

However, R _s in Expression (8) is a plane including the optical axis of the light source at the end, and the extension in the plane including the first axis and the second axis intersecting the first axis. This is the radius of a circle that includes the arc formed by the part on the circumference. Moreover, _xrs in Formula (8) shows the position of the center of the circle on the first axis. Moreover, _yrs in Formula (8) shows the position of the center of the circle on the second axis.
Moreover, _x15 in Formula (7) is represented by Formula (9).

However, d ₁ in Equation (9) is the distance between the light source and the side surface of the light guide plate of said end portion. In the equation (9), θ _α is an angle formed by the optical axis and the boundary. Moreover, _x12 in Formula (9) is represented by Formula (10).

However, _xc1 in Formula (10) is represented by the following Formula (11).

However, R _l in formula (11) is the radius of the circle containing the circular arc corner portion of the light-emitting region in said plane forms the circumference. In addition, x _rl in Expression (11) indicates the position of the center of a circle that includes an arc formed by the corner of the light emitting region on the first axis. Further, θ _m in the equation (11) is represented by the following equation (12).

However, n in Formula (12) is the refractive index of the said light-guide plate.
Moreover, y _c1 in Formula (10) is represented by the following Formula (13).

However, y _rl in Equation (13) indicates the position of the center of a circle that includes the arc formed by the corner of the light emitting region on the second axis.

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