JP2018097909A - Planar lighting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a planar lighting device that can increase luminance.SOLUTION: A planar lighting device includes a light guide plate and a light source. The light guide plate is formed with a through-hole between an incident end face into which light is introduced and an opposite end face that is an end face on an opposite side to the incident end face. The light source is provided on a side of the incident end face to emit light toward a side of the opposite end face. The light guide plate has a part of which thickness becomes thin as proceeding to the through-hole from the side of the opposite end face.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a planar lighting device.

  2. Description of the Related Art Conventionally, a so-called backlight, for example, a planar illumination device that illuminates a liquid crystal panel in a display device such as an in-vehicle indicator from the back side is known. The planar illumination device illuminates the display device by causing the light guided from the light source into the light guide plate to go from the light incident end surface to the opposite end surface to emit light from the light exit surface of the light guide plate. .

JP 2000-28397A

  However, in the conventional technique, when a through hole for passing through the axis of a pointer such as a speedometer in the display device exists in the light guide plate, the luminance is reduced on the rear side of the through hole, which is a region opposite to the light source. There was a fear.

  This invention is made | formed in view of the above, Comprising: It aims at providing the planar illuminating device which can improve a brightness | luminance.

  In order to solve the above-described problems and achieve the object, a planar illumination device according to one aspect of the present invention includes a light incident end surface into which light is introduced and an opposite end surface that is an end surface opposite to the light incident end surface. And a light source that is provided on the light incident end face side and emits the light toward the opposite end face side. In addition, the light guide plate has a portion whose thickness decreases from the opposite end surface side toward the through hole.

  According to one embodiment of the present invention, luminance can be improved.

FIG. 1 is an exploded perspective view of the planar lighting device according to the embodiment. FIG. 2 is a perspective view of the light guide plate according to the embodiment. FIG. 3 is a top view of the planar illumination device according to the embodiment. FIG. 4A is a cross-sectional view of the planar illumination device according to the embodiment. FIG. 4B is a cross-sectional view (part 1) of the planar lighting device according to the modification of the embodiment. FIG. 4C is a cross-sectional view (part 2) of the planar illumination device according to the modification of the embodiment. FIG. 4D is a cross-sectional view (part 3) of the planar illumination device according to the modification of the embodiment.

  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. In the embodiment described below, an expression such as “symmetric” may be used, but it is not necessary to strictly satisfy these conditions.

  First, a configuration example of the planar illumination device 100 according to the embodiment will be described with reference to FIG. FIG. 1 is an exploded perspective view of a planar illumination device 100 according to the embodiment. FIG. 1 shows a view of the planar illumination device 100 as viewed obliquely from above when the light exit surface 21d side of the light guide plate 21 is the upper side.

  In FIG. 1, for easy understanding, a three-dimensional orthogonal coordinate system in which the surface side on which the light exit surface 21 d of the light guide plate 21 emits light is the Z-axis positive direction is illustrated. Such an orthogonal coordinate system may be shown in other drawings used in the following description.

  The planar illumination device 100 shown in FIG. 1 is a so-called backlight that illuminates, for example, an indicator installed in an automobile from the back side. The application target of the planar lighting device 100 is not limited to the indicator, but may be any display device that can perform illumination display.

  As shown in FIG. 1, the planar illumination device 100 according to the embodiment includes an insertion member 10, a first frame 20, a light guide plate 21, a reflection sheet 22, a second frame 23, and a circuit board 31. I have. In addition, a display unit (not shown) such as a liquid crystal panel is provided on the light exit surface 21 d side, which is the positive Z-axis direction side of the light guide plate 21.

  The insertion member 10 is composed of a light absorbing member such as a black resin material, and is inserted into a through hole 40 formed in the light guide plate 21 or the like. The insertion member 10 can suppress luminance unevenness of the entire emission surface 21d by absorbing light leaking from the through hole 40 in the light guide plate 21.

  The insertion member 10 is not limited to a black resin material, and any material that can absorb light is sufficient. The insertion member 10 is not limited to the light absorbing member, and may be a reflecting member that reflects light.

  The first frame 20 is a frame-like member made of, for example, a resin material such as polycarbonate resin or an elastic material such as rubber. The first frame 20 is accommodated between the second frame 23 so as to cover the side end surfaces of the light guide plate 21, the reflection sheet 22, and the circuit board 31. Thereby, while being able to fix each member, it can prevent that light leaks outside from the side end surface 21c of the light-guide plate 21, or the opposite end surface 21b.

  The light guide plate 21 guides light from the light source 30 to emit light in a planar shape, and is made of a translucent material such as polycarbonate resin or acrylic resin. The light guide plate 21 is introduced into the light guide plate 21, a light incident end surface 21 a into which light from the light source 30 is introduced, an opposite end surface 21 b that is the end surface opposite to the light incident end surface 21 a, two side end surfaces 21 c, and the light guide plate 21. 21d, and a reflecting surface 21e for reflecting the light introduced into the light guide plate 21.

  In the light guide plate 21, the light from the light source 30 is introduced into the light guide plate 21 through the light incident end surface 21a on the X axis negative direction side, and the light is reflected between the emission surface 21d and the reflection surface 21e while being positive in the X axis direction. When traveling toward the opposite end surface 21b on the direction side, a part of the light hits the emission surface 21d and is emitted to the outside to emit light.

  The light guide plate 21 has an uneven reflective element (not shown) over the entire reflection surface 21e. That is, since the light is irregularly reflected by the unevenness of the reflecting element, the light is efficiently reflected to the entire emission surface 21d. For example, in the vicinity of the through-hole 40, such a reflective element has a larger interval of unevenness as it is closer to the light incident end surface 21 a side of the through-hole 40, and becomes closer to the opposite end surface 21 b side of the through-hole 40. ing.

  Thereby, in the vicinity of the through hole 40, the light is less likely to concentrate in the vicinity of the through hole 40 on the light incident end surface 21a side, and the light is likely to be concentrated in the vicinity of the opposite end surface 21b side of the through hole 40. In addition, it is good also as not only the case where the light-guide plate 21 is provided with a reflective element but the reflective sheet 22 is provided with a reflective element.

  The light guide plate 21 has a through hole 40 between the light incident end face 21a and the opposite end face 21b. As described above, the insertion member 10 is inserted into the through-hole 40 from the emission surface 21 d side, which is the positive side of the Z-axis of the light guide plate 21, and the shaft of a pointer such as a speedometer is inserted into the insertion member 10. The As shown in FIG. 1, in addition to the light guide plate 21, through holes are also formed in the reflection sheet 22 and the second frame 23, but these are collectively referred to as through holes 40 in the following.

  The reflection sheet 22 is laminated on the reflection surface 21 e side, which is the Z-axis negative direction side of the light guide plate 21, and reflects the leaked light from the reflection surface 21 e of the light guide plate 21, thereby returning the leaked light to the light guide plate 21. It is a member. The reflection sheet 22 is composed of, for example, a film in which a metal such as silver is vapor-deposited, a metal plate such as an aluminum plate subjected to mirror finishing, or a film having a reflection layer having a multilayer structure of polymer thin films.

  The second frame 23 is, for example, a metal plate such as aluminum, and the reflection sheet 22 and the circuit board 31 are provided on the front surface side that is the Z axis positive direction side. The second frame 23, the reflection sheet 22, and the circuit board 31 are fixed by a fixing member such as a double-sided tape. The four side end surfaces of the second frame 23 are fixed in contact with the first frame 20. The second frame 23 is not limited to a metal plate, but may be a resin material processed into a plate shape, or may be a composite structure of metal and resin.

  The circuit board 31 is, for example, a flexible printed circuit board (FPC), and a plurality of light sources 30 are provided on the main surface side that is the Z axis positive direction side. The circuit board 31 is provided with a circuit for supplying power to the light source 30.

  The light sources 30 are, for example, LEDs (Light Emitting Diodes), and are arranged at equal intervals along the light incident end surface 21 a of the light guide plate 21. The light source 30 emits light from the light incident end face 21a side toward the opposite end face 21b side. Note that the light sources 30 are not necessarily arranged at a uniform interval, and may be arranged at a non-uniform interval.

  Here, a conventional planar illumination device will be described. In the conventional planar lighting device, when the light guide plate has a through hole, the brightness is reduced because light does not easily reach the periphery of the through hole, particularly the back side of the through hole, which is the area opposite to the light source. There was a risk.

  Therefore, in the planar lighting device 100 according to the embodiment, light is easily emitted by reducing the thickness of the light guide plate 21 on the back side of the through hole 40. Specifically, the light guide plate 21 includes a thin portion 50 that is a portion having a small thickness from the opposite end surface 21 b side toward the through hole 40.

  That is, in the planar lighting device 100 according to the embodiment, by thinning the back side of the through hole 40, the number of times of light hitting the emission surface 21d in the thin portion 50 increases, so that light can be efficiently emitted even with a small amount of light. Can do. Therefore, according to the planar lighting device 100 according to the embodiment, the luminance can be improved.

  In addition, in the planar lighting device 100 according to the embodiment, the inclined surface 50a is formed such that the emission surface 21d side is inclined from the opposite end surface 21b side toward the through hole 40 side. This will be described later with reference to FIG.

  Next, the light guide plate 21 according to the embodiment will be described with reference to FIG. FIG. 2 is a perspective view of the light guide plate 21 according to the embodiment. In FIG. 2, the periphery of the through hole 40 in the light guide plate 21 is partially shown.

  As shown in FIG. 2, the light guide plate 21 has a thin portion 50 around the through hole 40. The thin portion 50 is formed, for example, by scraping the light guide plate 21 from the Z axis positive direction side that is the emission surface 21d (see FIG. 1) side.

  The thin portion 50 has inclined surfaces 50a and 50c and a bottom surface 50b. The two inclined surfaces 50a are joined to each other so as to have a valley fold shape. In addition, each inclined surface 50a is combined with an inclined surface 50c corresponding to each inclined surface 50a, and is combined with a common bottom surface 50b. The bottom surface 50b is provided along the peripheral surface of the light guide plate 21 in the through hole 40, and is disposed in a direction facing the reflecting surface 21e (see FIG. 1) on the Z axis negative direction side.

  The slope 50a has a gentler slope than the slope 50c. The slopes of the slope 50a and the slope 50c may be the same, or the slope 50a may be steeper than the slope 50c.

  Next, the top view of the planar illumination device 100 according to the embodiment will be described with reference to FIG. FIG. 3 is a top view of the planar illumination device 100 according to the embodiment. FIG. 3 shows a view of the planar illumination device 100 as viewed from the exit surface 21d side, which is the positive Z-axis direction side. In FIG. 3, the insertion member 10 is not shown in order to make the through hole 40 and the thin portion 50 easier to see.

  As shown in FIG. 3, the thin portion 50 is provided over the entire peripheral surface on the opposite end surface 21 b (see FIG. 1) side, which is the X axis positive direction side, of the peripheral surface of the light guide plate 21 in the through hole 40. Specifically, the thin portion 50 extends from the through hole 40 side to the opposite end surface 21b side which is the X axis positive direction side. Thereby, it can prevent that a brightness | luminance falls in the opposite end surface 21b side vicinity in the through-hole 40. FIG.

  The thin portion 50 is provided over the entire peripheral surface of the light guide plate 21 on the side of the opposite end surface 21b of the through hole 40. However, the present invention is not limited to this, and the light guide plate 21 is provided on the side of the opposite end surface 21b of the through hole 40. The thin part 50 should just be provided in at least one part of a surrounding surface. For example, when it is provided on a part of the peripheral surface on the opposite end face 21b side of the through-hole 40, it is preferable to provide it preferentially at a position where the luminance is significantly reduced based on the result of the luminance simulation.

  3, the inclined surfaces 50a and 50c and the bottom surface 50b of the thin portion 50 are arranged so as to be symmetrical with respect to a line in the X-axis direction passing through the center of the through hole 40. Thereby, the luminance can be improved uniformly on the rear side of the through hole 40. In addition, the thin part 50 is not limited to left-right symmetry, What kind of arrangement | positioning may be sufficient if a brightness | luminance can be improved uniformly.

  The thin portion 50 extends from the through hole 40 to the front of the opposite end surface 21b (see FIG. 1), but may extend from the through hole 40 to the opposite end surface 21b. Thereby, it can prevent that a brightness | luminance falls in the opposite end surface 21b vicinity.

  Further, in the top view shown in FIG. 3, the shape of the thin portion 50 is a pentagon. However, the shape is not limited to this, and the shape of the thin portion 50 such as another polygonal shape or an arc shape can be appropriately changed.

  Next, the cross section of the planar lighting device 100 according to the embodiment will be described with reference to FIGS. 4A to 4D. FIG. 4A is a cross-sectional view of the planar illumination device 100 according to the embodiment. 4B to 4D are cross-sectional views (No. 1 to No. 3) of the planar illumination device 100 according to the modification of the embodiment. 4A shows a cross-sectional view taken along line AA in FIG.

  As shown in FIG. 4A, the light guide plate 21 is formed in a shape in which the emission surface 21 d side is recessed, so that the thin portion 50 is formed. Specifically, the inclined surface 50a and the bottom surface 50b of the thin portion 50 are formed on the emission surface 21d side. Thereby, since it is not necessary to change the arrangement of the reflecting elements (not shown) on the reflecting surface 21e on the Z axis negative direction side of the light guide plate 21, the manufacturing cost can be suppressed.

  The inclined surface 50a is a part of the emission surface 21d and is inclined downward from the opposite end surface 21b (see FIG. 1) side toward the through hole 40 side. That is, the light guide plate 21 is formed with the inclined surface 50a whose thickness decreases from the opposite end surface 21b side toward the through hole 40 side. In other words, the light guide plate 21 on the inclined surface 50a has a tapered shape whose thickness decreases as it goes from the opposite end surface 21b side to the through hole 40 side.

  That is, by gradually reducing the thickness of the light guide plate 21, it is possible to prevent the brightness from changing suddenly at the boundary between the emission surface 21d and the thin portion 50. Therefore, luminance unevenness can be suppressed.

  As shown in FIG. 4A, the bottom surface 50b is provided at a position facing the reflecting surface 21e on the Z-axis negative direction side of the light guide plate 21. Specifically, the bottom surface 50b has an inclination angle of 0 degree. That is, the bottom surface 50b has a smaller inclination angle than the inclined surface 50a. In other words, the light guide plate 21 is gently inclined from the middle of the inclined surface 50 a to the through hole 40.

  Thus, the light refraction direction is different between the bottom surface 50b and the inclined surface 50a. That is, the light emitted from the bottom surface 50b is refracted toward the emission surface 21d side, which is the positive direction of the Z axis, by reducing the inclination of the bottom surface 50b. Thereby, since light can be guided directly above the bottom surface 50b (Z-axis positive direction side), the luminance can be improved on the rear side of the through hole 40.

  In FIG. 4A, the bottom surface 50b has an inclination angle of 0 degree, but the present invention is not limited to this, and it is sufficient that the inclination angle is smaller than that of the inclined surface 50a. In FIG. 4A, the bottom surface 50b and the inclined surface 50a are connected to bend, but the bottom surface 50b and the inclined surface 50a may be connected to be gently curved.

  In addition, the light guide plate 21 has the bottom surface 50b whose inclination is gentler than that of the inclined surface 50a. For example, as shown in FIG. 4B, only the inclined surface 50a may be formed without forming the bottom surface 50b. Good.

  In the modification shown in FIG. 4B, the light guide plate 21 is formed with an inclined surface 50 a that is inclined downward from the opposite end surface 21 b side to the through hole 40 in the thin portion 50. Specifically, the thickness of the light guide plate 21 decreases from the opposite end surface 21b toward the through hole 40, and the thickness of the light guide plate 21 is substantially zero at the position in contact with the insertion member 10 in the through hole 40. .

  Thereby, since the process of forming the bottom face 50b can be omitted, the number of manufacturing steps can be reduced. In FIG. 4B, the light guide plate 21 has a thickness of substantially zero at a position in contact with the insertion member 10. However, when the thickness of the light guide plate 21 is gradually reduced, the position in contact with the insertion member 10 is not zero and is constant. You may have thickness of.

  Moreover, although the case where the exit surface 21d side of the light guide plate 21 is recessed has been described above, for example, as shown in FIG. 4C, the reflective surface 21e side of the light guide plate 21 may be recessed.

  As shown in FIG. 4C, the thin portion 50 of the light guide plate 21 has a shape in which the reflection surface 21e is recessed. Specifically, in the thin portion 50, the inclined surface 50a and the bottom surface 50b are formed on the reflective surface 21e side which is the Z-axis negative direction side.

  That is, by denting the reflective surface 21e side, the thickness of the light guide plate 21 can be reduced without reducing the height position of the emission surface 21d in the thin portion 50. Thereby, since the distance from 21 d of output surfaces to the display part in the Z-axis positive direction side can be kept uniform, luminance unevenness can be further suppressed.

  In FIG. 4C, the thin portion 50 has the inclined surface 50a and the bottom surface 50b formed only on the reflecting surface 21e side, but the inclined surface 50a and the bottom surface 50b may be formed on both the emitting surface 21d and the reflecting surface 21e. .

  Further, the light guide plate 21 is formed so that the thickness is gradually reduced by forming the inclined surface 50a. However, for example, as shown in FIG. 4D, the inclined surface 50a is not formed step by step. The thickness may be reduced.

  Specifically, as illustrated in FIG. 4D, the thin portion 50 of the light guide plate 21 is formed with a plurality of surfaces 50 d having different height positions in the Z-axis direction, which is the stacking direction of the light guide plates 21. As the plurality of surfaces 50d are arranged closer to the through hole 40 from the opposite end surface 21b, the height position becomes lower, that is, the thickness becomes thinner.

  Note that the number of the surfaces 50d is not limited to two, and may be three or more as long as it is plural. Moreover, the height position of the surface 50d shown in FIG. 4D is an example, and it is preferable that the position is changed to an optimum position according to the simulation result of luminance.

  As described above, in the planar lighting device 100 according to the embodiment, the light guide plate 21 penetrates between the light incident end surface 21a into which light is introduced and the opposite end surface 21b that is the end surface opposite to the light incident end surface 21a. A hole 40 is formed. The light source 30 is provided on the light incident end surface 21a side and emits light toward the opposite end surface 21b side. In addition, the light guide plate 21 has a portion (thin portion 50) that is thinner from the opposite end surface 21b side toward the through hole 40. Thereby, the brightness | luminance of the back side of the through-hole 40 can be improved.

  Further, in the planar lighting device 100 according to the embodiment, the light guide plate 21 is formed with an inclined surface 50a in the thin portion 50 having an inclination that becomes thinner from the opposite end surface 21b side toward the through hole 40 side. Thereby, luminance unevenness can be suppressed.

  Moreover, in the planar lighting device 100 according to the embodiment, the light guide plate 21 is gradually inclined from the middle of the inclined surface 50 a to the through hole 40. Thereby, since light can be guided directly above the bottom surface 50b (Z-axis positive direction side), the luminance can be improved on the rear side of the through hole 40.

  In the planar illumination device 100 according to the embodiment, the inclined surface 50a is formed on the emission surface 21d side that emits light. Thereby, since it is not necessary to change the arrangement of the reflecting elements on the reflecting surface 21e on the negative side of the Z-axis of the light guide plate 21, the manufacturing cost can be suppressed.

  Moreover, in the planar lighting device 100 according to the embodiment, the light guide plate 21 is provided with the thin portion 50 over the entire peripheral surface on the opposite end surface 21b side in the peripheral surface of the through hole 40. Thereby, it can prevent that a brightness | luminance falls in the opposite end surface 21b side of the through-hole 40 in the light-guide plate 21. FIG.

  In the above-described embodiment, the light exit surface 21d of the light guide plate 21 is shown in a rectangular shape (see FIG. 1), but may be a partially curved shape. Specifically, the light guide plate 21 may have a shape in which the opposite end surface 21b is curved.

  Further, the present invention is not limited by the above embodiment. What comprised suitably combining each component mentioned above 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.

21 light guide plate 21a light incident end face 21b opposite end face 30 light source 40 through hole 50 thin part 100 planar illumination device

Claims (5)

A light guide plate in which a through hole is formed between a light incident end surface into which light is introduced and an opposite end surface which is an end surface opposite to the light incident end surface;
A light source that is provided on the light incident end face side and emits the light toward the opposite end face side;
With
The light guide plate is
A portion having a thickness that is thinner toward the through hole from the opposite end surface side,
Planar lighting device. The light guide plate is
An inclined surface is formed in the portion that becomes an inclined thickness that decreases from the opposite end surface side toward the through-hole side,
The planar illumination device according to claim 1. The light guide plate is
The inclination becomes gentle from the middle of the inclined surface to the through hole,
The planar illumination device according to claim 2. The inclined surface is
Formed on the exit surface side for emitting the light,
The planar illumination device according to claim 2 or 3. The light guide plate is
Of the peripheral surface in the through hole, the portion is provided over the entire peripheral surface on the opposite end surface side.
The planar illuminating device as described in any one of Claims 1-4.

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