JP6504783B2 - Planar light unit - Google Patents

Description

  The present invention relates to a planar light unit which illuminates a display having a curved side like a dial of a watch from the back.

  A lighting device is known which illuminates from the upper side of the periphery of a display, as opposed to a small, circular display such as a watch dial. For example, the front light (illumination device) shown in FIG. 1 of Patent Document 1 includes an annular light guide, and the light guide emits light from the periphery of the dial toward the center to illuminate the dial. ing. Therefore, FIG. 1 of Patent Document 1 is re-posted on FIG. 7 to describe its structure. FIG. 7 is a perspective view of a front light (illumination device) shown as a conventional example.

  As shown in FIG. 7, the front light 10 is composed of a light guide 9 provided with a light guide 12 and a light source unit 11. An incident surface 12a is formed on the light guide 12, and the light source unit 11 is attached to the incident surface 12a. The inner peripheral side of the light guide 12 is an emission surface 12 b for emitting the light introduced into the light guide 12. The outer peripheral side of the light guide 12 is a reflecting surface 12c, and the reflecting surface 12c includes a reflecting groove 14 having a wedge-shaped cross section, and reflects light toward the emitting surface 12b. As described above, the front light 10 uniformly illuminates the inner circular area of the light guide 12.

  When it is desired to display various information beyond simple displays such as time, a liquid crystal panel may be used for the dial. As well known in information equipment and the like, the liquid crystal panel looks better in backlight (planar light unit) than in front light. On the other hand, EL panels have been used as backlights for liquid crystal panels for timepiece dials, which are required to be small and thin. However, the EL panel requires a high voltage of about 100 V, and the light emission color and the light emission efficiency are not good. Therefore, these problems can be solved by adopting a backlight with an LED as a light source and a thin light guide plate.

  The inventor of the present invention has manufactured a backlight (planar light unit) provided with an LED and a light guide for a timepiece that uses a liquid crystal panel as a dial, based on knowledge of front lights and back lighting devices of information devices. In this backlight, a part of a disk-shaped light guide plate was cut off linearly to form an incident surface, and an LED was attached to the incident surface. A light extraction dot was formed on the opposite side of the exit surface of the light guide plate. At this time, the side surfaces of the light guide plate other than the incident surface are mirror surfaces so that the light propagating in the light guide and reaching the side surface is directed to the central portion of the light guide plate. The mirror surface is a surface that is flattened so as to cause total reflection, and the outer periphery of the light guide plate is surrounded by a white frame.

Patent document 1: JP-A-2004-134223 (FIG. 1)

  However, when the above-described backlight was turned on, an annular bright line was generated on the exit surface of the light guide plate. Furthermore, it was found that this bright line is generated along the curved portion not only in the disk-shaped light guide plate but also in the light guide plate provided with the curved portion around the emission surface.

  Therefore, the present invention has been made in view of the above problems, and when viewed from the light emission surface side of the light guide plate, even if the light guide plate is provided with a curved portion around it, the bright line generated by the curved portion is suppressed. An object of the present invention is to provide a planar light unit that can be used.

A planar light unit according to the present invention includes a light source and a light guide plate, and is a planar light unit that emits light incident from the light source to the incident surface of the light guide plate from the exit surface of the light guide plate orthogonal to the incident surface. In the light guide plate, the light guide plate includes a curved portion which is convex toward the outside when viewed from the exit surface side, the curved portion has a diffusion surface on the side surface, and the light guide plate is It is disk shape, The said entrance plane is formed by cutting out a part of disc, When it sees from the said output surface side, the 1st side which a perpendicular bisector passes through the center of the said disc, The said side A second side and a third side are provided on both sides of the first side, and the second side and the third side are inclined with respect to the first side such that the first side is deeply cut .

  In the planar light unit of the present invention, a curved portion is formed on the periphery when viewed from the exit surface side of the light guide plate. In this curved portion, the side surface orthogonal to the exit surface is a diffusion surface. A part of light (light) incident on the light guide plate from the incident surface of the light guide plate propagates while being totally reflected in the light guide plate, and is diffusely reflected on the side surface of the curved portion. That is, in the conventional light guide plate, bright lines are generated because light rays reflected on the side surface of the curved portion are locally concentrated based on the curved shape, whereas in the light guide plate of the present invention The bright rays are suppressed because the reflected rays are diffused and not concentrated.

There are a plurality of light sources facing the light incident surface, and a plurality of prisms in which ridge lines are continuous in the thickness direction of the light guide plate are formed on the light incident surface facing at least the light source closest to the side surface. The asymmetrical shape, the average value of the angle between the light axis of the light source and the side of the prism on the opposite side to the side surface of the light guide plate in the horizontal cross section is on the side surface side of the light guide plate It may be smaller than the average value of the angle formed by the side of the prism and the optical axis of the light source .

In the horizontal cross section, the prisms may form an equilateral triangle, and the prisms having a right angle or an acute angle at the incident surface and the prisms having an obtuse angle may be alternately arranged .

A planar light unit according to the present invention includes a light source and a light guide plate, and is a planar light unit that emits light incident from the light source to the incident surface of the light guide plate from the exit surface of the light guide plate orthogonal to the incident surface. In the light guide plate, when viewed from the light exit surface side, the light guide plate has a curved portion in the periphery, the side surface of the curved portion is a diffusion surface, and there are a plurality of light sources facing the light incident surface. A plurality of prisms in which ridge lines extend in the thickness direction of the light guide plate is formed on the incident surface facing the light source closest to the side surface, the prisms having an asymmetrical shape in the horizontal section, the light guide plate in the horizontal section The average value of the angle between the side of the prism on the side opposite to the side and the optical axis of the light source is the angle between the side of the prism on the side of the light guide plate and the optical axis of the light source The prisms are smaller than the average value of the above, and in the horizontal cross section, the prisms form an equilateral triangle, and the prisms whose apex angles are at right angles or acute angles at the incident surface and the prisms whose obtuse angles are obtuse are alternately arranged It is characterized by

The light guide plate may have a disk shape, and the incident surface may be formed by cutting a part of the disk .

The diffusion surface may be a prism surface or an uneven surface .

There may be a flat portion between the plurality of prisms .

  As described above, in the planar light unit according to the present invention, the bright line generated when the side surface of the curved portion is a mirror surface is suppressed by using the side surface as the diffusion surface.

BRIEF DESCRIPTION OF THE DRAWINGS The disassembled perspective view of the planar light unit shown as 1st Embodiment of this invention. FIG. 2 is a perspective view of a light guide plate included in the planar light unit shown in FIG. 1. FIG. 3 is a plan view of the light guide plate shown in FIG. 2; The light guide plate which is an enlarged view of a light-guide plate side, (a) is a comparative example, (b) shows in FIG. The top view of a part of planar light unit shown as a 2nd embodiment of the present invention. The top view of a part of planar light unit shown as a 3rd embodiment of the present invention. The perspective view of the front light shown as a prior art example. The top view which shows a part of light guide plate contained in 4th Embodiment of this invention.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached FIGS. In the description of the drawings, the same or corresponding elements are denoted by the same reference numerals and redundant description will be omitted.

First Embodiment
A planar light unit 20 shown as a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is an exploded perspective view of the planar light unit 20. FIG. FIG. 2 is a perspective view of the light guide plate 22 included in the planar light unit 20. As shown in FIG. FIG. 3 is a plan view of the light guide plate 22. As shown in FIG. FIG. 4 is an enlarged view of the side surface of the light guide plate 22, (a) is a comparative example before electric discharge machining, and (b) is the light guide plate 22 of the first embodiment.

  As shown in FIG. 1, in the planar light unit 20, the light guide plate 22, the diffusion sheet 23, and the prism sheets 24 and 25 are stacked on the reflection sheet 21. Three LEDs 26 are attached to the light guide plate 22.

  The reflective sheet 21 shown in FIG. 2 has a thickness of 65 μm, and directs the light leaked from the lower surface of the light guide plate 22 to the light emitting surface 22 e side of the light guide plate 22. The light guide plate 22 has a thickness of 400 μm, is provided with incident surfaces 22a, 22b and 22c on the side surfaces, and has a plurality of dots (not shown) formed on the bottom surface. The light incident from the incident surfaces 22a, 22b, and 22c propagates the inside of the light guide plate 22, changes the traveling direction by the dots formed on the bottom surface, and exits from the exit surface 22e. The diffusion sheet 23 has a thickness of 35 μm and is formed by scattering and fixing diffusion particles on a transparent sheet, and spreads the light emitted from the light guide plate 22. The prism sheets 24 and 25 have a thickness of 65 μm, and microprisms are arranged on the upper surface side to adjust the light emission direction. The prism ridges of the prism sheet 24 are orthogonal to the prism ridges of the prism sheet 25.

  As shown in FIGS. 2 and 3, the light guide plate 22 is formed with incident surfaces 22a, 22b and 22c at positions where a circular flat plate is cut out. The incident surfaces 22a, 22b, 22c are divided into three regions by two projections. The central incident surface 22b is formed such that a perpendicular bisector passes through the center of the disk (light guide plate 22). The two side regions 22a and 22c are inclined with respect to the central incident surface 22b so that the central side is deeply cut. Due to this inclination, regions adjacent to the left and right of the incident surfaces 22a, 22b, 22c are also sufficiently distributed.

  As shown in FIG. 1, LEDs 26 are attached to the regions of the incident surfaces 22 a, 22 b and 22 c one by one. The LED 26 is mounted on an FPC (flexible printed circuit board) not shown, and the exit slope of the LED 26 faces the incident surfaces 22a, 22b, and 22c. A light shielding sheet (not shown) is provided on the side of the light guide plate 22 of the FPC so that light colored and incident on the FPC from the LED 26 does not enter the light guide plate 22 again. The periphery of the light guide plate 22 is surrounded by a white frame not shown.

  In the light guide plate 22, a side surface 22 d of a curved portion indicated by a thick line in FIG. 2 is a diffusion surface. The dots formed on the lower surface of the aforementioned light guide plate 22 have their density or size changed depending on the location so that the emitted light becomes uniform.

Next, the appearance of the side surface 22d of the light guide plate 22 will be described with reference to FIG. As shown to Fig.4 (a), in order to show that it is a light guide plate 22h of a comparative example (a light guide plate of a comparative example, the suffix h was attached. The comparative example is a surface only in the processing state of the side in the curve part of a light guide plate 22h. It differs from the light unit 20. The same applies to the following.), The side surface 22g is a flat surface. This flat surface (side surface 22g) is a mirror surface in a state of being taken out of the mold. The light guide plate 22h of the comparative example shown in FIG. 4 (a) is the one before discharge processing of the light guide plate 22 shown in FIG. 4 (b). On the other hand, in the light guide plate 22 shown in FIG. 4B, the side surface 22d of the curved portion is subjected to electrical discharge machining, and a random uneven shape is formed on the side surface 22d.

  In the planar light unit 20 and the comparative example, light rays incident on the light guide plates 22 and 22a from the incident surfaces 22a, 22b and 22c propagate inside the light guide plates 22 and 22a while repeating total reflection, and a part thereof is a curved portion. Sides 22d, 22g are reached.

  As shown in FIG. 4A, when the side surface 22g of the curved portion of the light guide plate 22a is made flat, light rays incident on the side surface 22g at a critical angle or more are totally reflected. At this time, since the side surface 22g is curved, light rays totally reflected on the side surface 22g are concentrated in a ring shape. The annularly concentrated light beam becomes an annular bright line. In particular, the ring-like bright lines stand out in the region near the incident surfaces 22a and 22c where the incident angle increases with respect to the side surface 22g, and inconspicuous in the region opposite to the center (region facing the incident surface 22b). Light incident on the side surface 22g at a critical angle or less passes through the side surface 22g, is irregularly reflected by a white frame surrounding the outer periphery of the light guide plate 22a, and is incident on the light guide plate 22a again.

  On the other hand, when the side surface 22d of the light guide plate 22 is a diffuse reflection surface (diffusing surface) as shown in FIG. 4B, the directions of light rays reflected by the side surface 22d become random. As a result, the concentration of light rays due to the reflection of the side surface 22d is eliminated, and the annular bright line generated in the light guide plate 22a in FIG. 4A is generated in the light guide plate 22 obtained by electrical discharge machining the side surface 22d in FIG. I will not do. A light beam incident on the side surface 22d at a critical angle or less passes through the side surface 22d, is irregularly reflected by a white frame surrounding the outer periphery of the light guide plate 22, and is incident on the light guide plate 22 again.

Second and third embodiments
In the planar light unit 20 shown as the first embodiment, the side surface 22 d of the light guide plate 22 is a diffusion surface formed by electrical discharge machining. However, in the planar light unit of the present invention, the diffusion surface formed on the side surface of the light guide plate is not limited to the one by electric discharge machining. Therefore, planar light units 30, 40 in which the side surfaces of the curved portion are a prism surface and an uneven surface will be described as second and third embodiments of the present invention with reference to FIGS. 5 and 6 are enlarged plan views of a portion of the curved portion of the planar light units 30 and 40, corresponding to the region B enclosed by the broken line in FIG.

  The planar light unit 30 is the same as the planar light unit 20 shown in FIG. 1 except for the light guide plate 32. As shown in FIG. 5, the side surface of the curved portion of the light guide plate 32 is a prism surface, and the minute prisms 31 are arrayed. The microprisms 31 extend in the thickness direction of the light guide plate 32 and have a triangular cross section. A part of the light reaching the side surface of the curved portion is reflected by the micro prism 31. The reflection surface of the micro prism 31 cancels the concave mirror-like curved shape of the curved portion, so the reflected light is not collected. The remaining part of the light reaching the side passes through the side, is irregularly reflected by the white frame surrounding the outer periphery of the light guide plate 32, and is incident on the light guide plate 32 again. The cross-sectional shape of the micro prism 31 is not limited to a triangle, and may be cylindrical or rectangular. Since this light guide plate 32 is molded with a mold, the manufacturing process is shorter than the light guide plate 22 shown in FIG.

The planar light unit 40 is the same as the planar light unit 20 shown in FIG. 1 except for the light guide plate 42. As shown in FIG. 6, the side surface of the curved portion of the light guide plate 42 is an uneven surface, and the minute dots 41 are arranged. The minute dots 41 are dome-shaped and arranged in the thickness direction of the light guide plate 42. A part of the light reaching the side surface of the curved portion is reflected by the minute dot 41. The reflection surface of the minute dot 41 cancels the concave mirror-like curved shape of the curved portion, so the reflected light is not collected. The remaining part of the light reaching the side passes through the side, is irregularly reflected by the white frame surrounding the outer periphery of the light guide plate 42, and is incident on the light guide plate 42 again. The light guide plate 42 can be manufactured by a mold. In order to make it easy to take out the light guide plate 42 from the mold, the side surface is inclined by about 5 °. In this way, when the light guide plate 42 is taken out of the mold, the micro todds 41 become difficult to catch. Further, as with the light guide plate 32 shown in FIG. 5, the light guide plate 42 can also shorten the manufacturing process.

  In the planar light unit 40 shown in FIG. 6, dome-shaped minute dots 41 are formed on the side surface of the curved portion of the light guide plate 42, and the portion is used as a diffusion surface. The concavo-convex shape formed on the side surface of the light guide plate 42 is not limited to the dome shape, and is a random concavo-convex shape like the side surface 22 d in the curved portion of the light guide plate 22 included in the planar light unit 20 shown in FIG. Also good. In order to manufacture the light guide plate having the random uneven shape with a mold, the inner side surface (portion corresponding to the side surface of the curved portion) of the mold may be roughened by electrical discharge machining.

  In the planar light units 20, 30, and 40 described as the first to third embodiments, the light guide plates 22, 32, and 42 have a disk shape. However, the light guide plate included in the planar light unit of the present invention is not limited to the disk shape. That is, if there is a curved portion that behaves like a concave mirror in part of the side surface of the light guide plate, the bright line generated due to the curved shape of the curved portion can be suppressed by using the side surface of the curved portion as a diffusion surface.

Fourth Embodiment
The light guide plates 22, 32, 42 included in the planar light units 20, 30, 40 shown in the first to third embodiments have the side surfaces 22d etc. as diffusely reflecting surfaces, and the surface opposite to the light emitting surface as described above. By adjusting the density and size of the dot pattern to be formed, uniformity of the emitted light is secured. Furthermore, the uniformity of the emitted light can be improved by adjusting the light distribution of the light entering the light guide plate. A planar light unit 80 having a prism on the incident surface and adjusting the distribution of incident light by this prism will be described as a fourth embodiment with reference to FIG.

  FIG. 8 is a plan view showing a part of the light guide plate 82 included in the planar light unit 80. FIG. 8 (a) is a plan view in the vicinity of the incident surfaces 82a, 82b and 82c, and FIG. 8 (b) is an incident surface 82a. FIG. 8 (c) is an enlarged plan view of a part of the incident surface 82b.

  As shown in FIG. 8A, the light guide plate 82 is provided with incident surfaces 82a, 82b, 82c and side surfaces 82d, 82e. The light guide plate 82 includes the light guide plate 22 shown in FIGS. 2 and 3 except for the prisms 83, 85, 86, 88 {see FIGS. 8 (b) and 8 (c)} formed on the incident surfaces 82a, 82b and 82c. Shape and structure are equal. Further, in FIG. 8A, the side surface is divided into a side surface 82d and a side surface 82e for the convenience of description. LEDs (light sources) (not shown) are disposed so that the light emitting surfaces face the incident surfaces 82a, 82b and 82c. The incident surface 82a is an incident surface facing the LED (light source) closest to the side surface 82d. The incident surface 82c is an incident surface facing the LED (light source) closest to the side surface 82e.

  As shown in FIG. 8B, on the incident surface 82a, a plurality of prisms 83 and 85 in which ridge lines extend in the thickness direction of the light guide plate 82 are formed. The prism 83 is in the form of an equilateral triangle whose apex angle is obtuse in the horizontal cross section. At this time, an angle θ2 formed by the side 83b of the prism 83 on the opposite side of the side face 82d of the light guide plate 82 (see FIG. 8A) and the optical axis L1 of the LED is the prism 83 on the side face 83d of the light guide plate 82 Is smaller than an angle .theta.1 formed by the side 83a of the lens and the optical axis L1 of the LED. The optical axis L1 of the LED is the normal direction of the exit slope of the LED and the normal direction of the incident surface 82a (the same applies to the following). Further, since the prism 83 is a triangular prism, the horizontal cross section has the same shape in plan view (the same applies in the following). Here, the horizontal cross section is a cross section parallel to the exit surface of the light guide plate 82 (the same applies to the following).

As shown in FIG. 8B, the prism 85 is in the form of an equilateral triangle whose vertical angle is perpendicular or acute in the horizontal cross section. The angle θ4 between the side 85b of the prism 85 on the opposite side of the side surface 82d (see FIG. 8A) of the light guide plate 82 and the optical axis L1 of the LED in the horizontal cross section is the prism on the side surface 82d side of the light guide plate 82 It is smaller than an angle θ3 formed by the side 85 a of 85 and the optical axis of the LED. Further, the height h2 of the prism 85 is higher than the height h1 of the prism 83, and there is a flat portion 84 between the prism 85 and the prism 83. The prisms 85 and the prisms 83 are alternately arranged.

  For example, angles θ 1, θ 2, θ 3 and θ 4 are 75 °, 65 °, 50 ° and 40 ° respectively, heights h 1 and h 2 are respectively 0.005 mm and 0.010 mm, the pitch of prisms 83 and the pitch of prisms 85 Each pitch is set to 0.060 mm.

  As shown in FIG. 8C, on the incident surface 82b, a plurality of prisms 86 and 88 in which ridge lines extend in the thickness direction of the light guide plate 82 are formed. The prism 86 is in the form of an isosceles triangle whose obtuse angle is obtuse in the horizontal cross section. At this time, an angle θ6 between the side 86b of the prism 86 and the optical axis L1 of the LED is equal to an angle θ5 between the side 86a of the prism 86 and the optical axis L1 of the LED. Similarly, the prism 88 is in the form of an isosceles triangle whose acute angle is acute in the horizontal cross section. At this time, an angle θ8 formed between the side 88b of the prism 88 and the optical axis L1 of the LED is equal to an angle θ7 formed between the side 88a of the prism 88 and the optical axis L1 of the LED. The height h4 of the prism 88 is higher than the height h3 of the prism 86, and there is a flat portion 87 between the prism 88 and the prism 86. The prisms 88 and the prisms 86 are alternately arranged.

  For example, angles θ5, θ6, θ7 and θ8 are 70 °, 70 °, 45 ° and 45 ° respectively, heights h3 and h4 are respectively 0.005 mm and 0.010 mm, the pitch of the prisms 86, and the pitch of the prisms 88 Each pitch is set to 0.060 mm.

  On the incident surface 82c, a prism array axially symmetrical to the prism array formed on the incident surface 82a is formed with a straight line (not shown) passing through the center of the incident surface 82b and the center of the light guide plate 82 as an axis. In the following, the incident surface 82c has an axial symmetry with the incident surface 82a, and thus the description thereof is omitted.

  First, the light distribution of the light incident on the light guide plate 82 from the incident surface 82b will be described based on FIG. 8C. The light (light beam) emitted from the LED disposed opposite to the incident surface 82b and incident on the side 86b of the prism 86 is refracted to the left in the figure. On the other hand, the light (light ray) emitted from the LED disposed opposite to the incident surface 82b and incident on the side 86a of the prism 86 is refracted to the right in the figure. The same applies to the prism 88, but the angle of refraction is larger than that of the prism 86. As described above, the light distribution of light emitted from the LED disposed opposite to the incident surface 82b and incident on the light guide plate 82 from the incident surface 82b is symmetrically spread in the horizontal direction. Since the flat portion 87 existing between the prism 88 and the prism 86 and the alternate arrangement of the prism 88 and the prism 86 function to overlap the three types of light distribution, the uniformity of the luminance distribution on the emission surface is improved. doing.

  Next, the light distribution of the light entering the light guide plate 82 from the incident surface 82a will be described based on FIG. The light emitted from the LED disposed opposite to the incident surface 82a and incident on the side 83b of the prism 83 is refracted to the left side of the drawing. On the other hand, the light emitted from the LED disposed opposite to the incident surface 82a and refracted to the side 83a of the prism 83 is refracted to the right in the figure. At this time, the difference between the prism 83 and the prism 86 in FIG. 8C is that the light (light) refracted at the side 83b in the prism 83 is largely refracted toward the incident surface 82a than the light (light) refracted at the side 83a. It is to be. As a result, the light (light ray) which turns around in the corner where the incidence surface 82a and the side surface 82d intersect increases.

Similarly, light emitted from the LED disposed opposite to the incident surface 82a and incident on the side 85b of the prism 85 is refracted to the left side of the figure. On the other hand, the light emitted from the LED disposed opposite to the incident surface 82b and incident on the side 85a of the prism 85 is refracted to the right in the figure. At this time, the difference between the prism 85 and the prism 88 of FIG. 8C is that light (light) refracted at the side 85 b in the prism 85 is largely refracted toward the incident surface 82 a than light refracted at the side 85 a It is to be. As a result, the light (light ray) which turns around in the corner where the incidence surface 82a and the side surface 82d intersect increases.

  As a result of the above, the prisms 83 and 85 formed on the incident surface 82a increase the brightness of the corner portion where the incident surface 82a and the side surface 82d intersect. The effect of increasing the brightness similarly occurs in the vicinity of the side surface 82d, and becomes weaker as the distance from the incident surface 82a increases.

  When the light guide plate is rectangular, since the incident surface is orthogonal to the side surface, the LED serving as the light source can be disposed close to the side surface. As a result, if the light guide plate is rectangular, a dark portion is less likely to occur in the portion extending from the corner portion to the side surface. However, if the light guide plate 80 is circular, there is a portion where the distance between the side surfaces 82d and 82e spreads away from the incident surfaces 82a to 82c, so the prisms 86 and 88 shown in FIG. Even if the incident surface 82a is provided on the incident surface 82a, a shortage of light (a dark portion) may occur in the expanded portion of the side surface 82d from the above-mentioned corner portion. Therefore, in the planar light unit 80, the prisms 83 and 85 provided on the incident surface 82a of the light guide plate 82 are made uneven to secure the light distribution applied to the portion where the side surface 82d is spread from the corner portion.

  Since the flat portion 84 existing between the prism 85 and the prism 83 and the alternate arrangement of the prism 85 and the prism 83 function to overlap three types of light distribution, the uniformity of the luminance distribution on the exit surface is improved. doing. In addition, when the incident surface 82a is inclined, when the circular light guide plate is notched and the incident surface is formed, an effect is obtained that the cut-out portion can be made smaller. It can be said that this effect is assisted or reinforced by the prisms 83 and 85. Further, the planar light unit 80 is characterized in that the prisms 83 and 85 are regularly arranged on the incident surface 82a, so that the planar light unit 80 is resistant to misalignment of the LEDs in the arrangement direction of the prisms 83 and 85. The prisms 83 and 85 formed on the incident surface 82a reduce the design load of dots formed on the surface of the light guide plate 82 opposite to the light emitting surface, and contribute to narrowing of the frame.

  In the planar light unit 80, the prisms 83, 85, etc. formed on the incident surfaces 82a, 82c are triangular prisms whose horizontal cross sections become irregular triangles. However, the prism for increasing the light distribution on the curved side of the light guide plate is not limited to such a triangular prism. For example, it may be a quadrangular prism whose horizontal cross section is a trapezoid having different lengths of left and right sides, or a pillar whose horizontal cross section is asymmetrical and is a curved surface. At this time, the prism has an asymmetrical shape in the horizontal cross section, and the average value of the angle formed by the side of the prism opposite to the side surface of the light guide plate in the horizontal cross section and the light axis of the light source is on the side surface side of the light guide plate It may be smaller than the average value of the angle formed by the side of the light source and the optical axis of the light source.

20, 30, 40, 80 ... planar light unit,
21 ... Reflective sheet,
22, 32, 42, 82 ... light guide plate,
22a, 22b, 22c, 82a, 82b, 82c ... incident surface,
22e ... exit surface,
22d, 22g, 82d, 82e ... side surfaces,
23 ... Diffusion sheet,
24, 25 ... prism sheet,
26 ... LED,
31 ... micro prism,
41 ... minute dots,
83, 85, 86, 88 ... prism,
83a, 83b, 85a, 85b, 86a, 86b, 88a, 88b ... sides,
84, 87 ... flat part,
L1 ... optical axis.

Claims (7)

A planar light unit comprising a light source and a light guide plate, and emitting light incident from the light source to the incident surface of the light guide plate from an exit surface of the light guide plate orthogonal to the incident surface,
The light guide plate includes a curved portion which is convex toward the outside when viewed from the emission surface side,
In the curved portion, the side surface is a diffusion surface ,
The light guide plate has a disk shape,
The incident surface is formed by cutting a part of a disc, and when viewed from the exit surface side, a first side through which a perpendicular bisector passes through the center of the disc and both sides of the first side And a second side and a third side which are inclined relative to the first side such that the first side is deeply cut . There are a plurality of light sources facing the light incident surface, and a plurality of prisms in which ridge lines are continuous in the thickness direction of the light guide plate are formed on the light incident surface facing at least the light source closest to the side surface. The asymmetrical shape, the average value of the angle between the light axis of the light source and the side of the prism on the opposite side to the side surface of the light guide plate in the horizontal cross section is on the side surface side of the light guide plate The planar light unit according to claim 1 , wherein the planar light unit is smaller than an average value of angles formed by sides of a prism and the optical axis of the light source. In the horizontal cross section, the prisms are in the shape of a scalene triangle, and the prisms having a right angle or an acute angle at the incident surface and the prisms having an obtuse angle are alternately arranged. The planar light unit according to claim 2 . A planar light unit comprising a light source and a light guide plate, and emitting light incident from the light source to the incident surface of the light guide plate from an exit surface of the light guide plate orthogonal to the incident surface,
The light guide plate is provided with a curved portion in the periphery when viewed from the light emission surface side, and the side surface of the curved portion is a diffusion surface,
There are a plurality of light sources facing the light incident surface, and a plurality of prisms in which ridge lines are continuous in the thickness direction of the light guide plate are formed on the light incident surface facing at least the light source closest to the side surface. The asymmetrical shape, the average value of the angle between the light axis of the light source and the side of the prism on the opposite side to the side surface of the light guide plate in the horizontal cross section is on the side surface side of the light guide plate Smaller than the average value of the angle between the side of the prism and the optical axis of the light source,
In the horizontal cross section, the prisms form an equilateral triangle, and the prisms having a right angle or an acute angle at the incident surface and the prisms having an obtuse angle are alternately arranged. Planar light unit. The planar light unit according to claim 4 , wherein the light guide plate has a disk shape, and the incident surface is formed by cutting a part of the disk. The planar light unit according to claim 4 , wherein the diffusion surface is a prism surface or an uneven surface. The planar light unit according to any one of claims 2 to 6 , wherein there is a flat portion between the plurality of prisms.

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