JP2004038108A - Light guide plate and surface lighting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain bright and uniform exit light by which a light source is not reflected and dark parts are not brought about even in both ends of an incidence end face part around the incidence end face part. <P>SOLUTION: A light guide plate 2 is formed into a rectangular cubic shape like a sheet and has six surrounding faces made into mirror surfaces. Minute optical deflection elements 8 are provided on a surface 6 and a backside 7. The distance between the surface 6 and the backside 7, namely, the thickness, is minimum in an incidence end face part 3 and is maximum in a counter incidence end face part 4 being at a maximum distance from the incidence end face part 3. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention avoids the reflection of strong light from the light source near the incident end face even if the light from the light source has directivity by setting the thickness of the light guide plate so that the position of the incident end face is minimized. The present invention relates to a light guide plate and a flat lighting device capable of avoiding the occurrence of dark portions at both ends near the incident end face of the light guide plate due to a small number of light sources.
[0002]
[Prior art]
In conventional light guide plates and flat lighting devices, in order to maximize the use of light from a light source, the thickness of the light guide plate is reduced as the distance from the incident end face is reduced, and the thickness of the light from the incident end face is reduced. A method utilizing a taper leak of light traveling in the opposite direction is known. Specifically, as shown in FIG. 6, the light guide plate 21 is formed in a wedge shape and guides light from a light source (not shown) to the incident end surface portion 31, the front surface portion 61, the back surface portion 71, and the front surface portion 61 and the back surface. It has side portions 51, 51 that intersect the portion 71 at a substantially right angle. The light guide plate 21 has a thicker one as the incident end face part 31, and becomes thinner toward the anti-incident end face part 41 b in a direction opposite to the incident end face part 31. Then, a light source is arranged to face the incident end face 31 and light is emitted from the front face part 61 and / or the rear face part 71 by utilizing a taper leak of light from the incident end face part 31 toward the anti-incident end face part 41. are doing.
[0003]
Further, in the case of a large planar illumination device, as shown in FIG. 7, the light guide plate 21A is configured such that the thickness of the light guide plate 21A is reduced from the incident end face portions 31a and 31b at both ends toward the center. Is done. In the planar lighting device using the light guide plate 21A, the light sources 91a and 91b are disposed on the incident end surfaces 31a and 31b at both ends of the light guide plate 21A, respectively. Then, light is emitted from the front surface portion 61 and / or the back surface portions 71a and 71b by utilizing a taper leak of light traveling from the incident end surface portions 31a and 31b in a direction opposite to the incident end surface portions 31a and 31b.
[0004]
In addition, when printing a white light scattering agent on the side opposite to the exit surface of the conventional light guide plate, even if the number of printed portions increases as the distance from the incident end surface increases or dots such as irregularities are provided on the light guide plate, The dots increased as the distance from the end surface increased.
[0005]
Further, as a conventional planar lighting device using a point light source such as an LED as a light source, a plurality of LEDs are arranged on a side surface of a light guide plate, and a convex or concave portion such as a prism is formed on an incident end face portion of the light guide plate at a position facing these LEDs. A method is known in which a light beam reaches the corners at both ends of the light guide plate.
[0006]
[Problems to be solved by the invention]
Here, as a conventional light guide plate and a planar illumination device, for example, a trajectory of a light ray on a wedge-shaped light guide plate 21 will be described with reference to FIG. As the light guide plate, a wedge-shaped one shown in FIG. 6 is used.
[0007]
As shown in FIG. 6, the light guide plate 21 is configured such that the thickness becomes thinner as it goes from the incident end face 31 to the anti-incident end face 41 located on the opposite side of the incident end face 31. As described above, since the light guide plate 21 has a wedge shape, the light beam L01 travels toward the surface portion 61 while the incident light L01 illustrated in FIG. 8 proceeds to the counter-incident end surface portion 41 located on the opposite side of the incident end surface portion 31. If the incident angle of the light ray L01 with respect to the front surface part 61 is within 42 °, the light ray L01 is totally reflected by the front surface part 61 and proceeds as a light ray L02 toward the back surface part 71. However, since the light guide plate 21 has a wedge shape that becomes thinner in the direction in which the light beam travels, the incident angle with respect to the back surface portion 71 is smaller than the critical angle, so that the light beam breaks the critical angle and becomes a light beam L03 or a light beam L04. The beam breaks the critical angle from 71 and emits.
In the description shown in FIG. 8, the outgoing light that breaks the critical angle is shown only on the back surface portion 71, but the outgoing light that breaks the critical angle also exists on the front surface portion 61.
[0008]
In this way, as shown in FIGS. 6 and 8, in order to maximize the use of light from the light source, the light guide plate is formed in a so-called wedge shape in which the thickness of the light guide plate decreases as the distance from the incident end surface increases. In the configuration using the taper leak of light traveling from the incident end face to the opposite direction to the incident end face, if the light source has directivity, the critical angle is immediately broken near the incident end face, that is, the taper leak increases. Bright emission is provided. Since the emitted light is a high-luminance and highly directional light, the shape of the semiconductor light-emitting element itself is observed (reflected) from the light-emitting surface in the case of the entire light source, for example, the light source of a semiconductor light-emitting element (LED). There is a problem that will be done.
[0009]
Further, as described above, in the light guide plate in which the thickness of the light guide plate is reduced as the distance from the incident end surface increases, the shape of the semiconductor light emitting element itself is prevented from being observed from the exit surface. The neighborhood is used without actually using it. For this reason, there is a problem that a light guide plate larger than the required area of the flat lighting device must be used.
[0010]
In the case of a conventional large flat lighting device, as shown in FIG. 7, the thickness of the light guide plate 21A is reduced from the incident end face portions 31a and 31b at both ends toward the center, and the incident end face portions 31a and 31b are reduced. In a configuration in which both ends of the light guide plate 21A are formed as the incident end face portions 31a and 31b by using a method utilizing a taper leak of light traveling in the opposite direction to the incident end face portions 31a and 31b, the thickness of the central portion of the light guide plate 21A is reduced. It is the thinnest part, and the problem is that the thinner the whole, the thinner the central part becomes, and the mechanical strength is weak.
[0011]
Furthermore, in order to obtain white light using three color light sources of RGB (red light emission, green light emission, and blue light emission), when the RGB light sources are sequentially arranged to form an array, each light emission color becomes the incident end face. There is a problem that the light is not white in the vicinity of the incident end face, and each of the luminescent colors is emitted from the emission surface in a patch-like manner because the light is hardly mixed in the vicinity of the part.
[0012]
Further, a conventional plain light illuminating device using a point light source such as an LED as a light source arranges a plurality of LEDs on an incident end face of a light guide plate and projects a convex or a prism on an incident end face of the light guide plate at a position facing these LEDs. In the configuration having the concave shape, the light source is a point light source, so that the light beam intensity distribution is circular or elliptical. For this reason, prism processing is performed on the incident end face portion of the light guide plate facing the light source, and the light is dispersed in the left-right direction of the light source and uniformly emitted from the entire light guide plate, but the light of the light source such as the adjacent LED overlaps, There is a problem that brightness unevenness occurs.
[0013]
Further, as shown in FIGS. 9A and 9B, in the conventional planar lighting device using the wedge-shaped light guide plate 21 and the point light source 9 such as one LED at the center of the incident end face portion 31, FIG. As shown in FIG. 9B, since the light source 9 of the semiconductor light emitting element such as an LED has directivity, the light beam travels in a narrow range toward the non-incident end face 41 and from the incident end face 31 toward the non-incident end face 41. The laser beam breaks the critical angle while traveling. Therefore, there is a problem that both ends of the incident end face 31 (between the incident end face 31 and the incident light beam L0) become dark portions.
[0014]
The present invention has been made to solve such a problem, and an object of the present invention is to form a monochromatic light or a red light, a green light, a three primary color light of a blue light or a wavelength conversion comprising a plurality of semiconductor light emitting elements having directivity. A light source composed of a single semiconductor light emitting element having an array shape or directivity that is white light utilizing a material, an incident end face portion for guiding light from the light source, and a front surface portion and / or a back surface portion for emitting the light. Having a side surface portion that intersects the front surface portion and the back surface portion at a substantially right angle, the distance between the front surface portion and the back surface portion is minimized at the incident end surface portion, and the front surface portion and the back surface at the maximum distance from the incident end surface portion. It has a thin plate-like rectangular cubic shape with the maximum distance to the surface, and the six surfaces surrounding these form a mirror surface, and a fine light deflecting element is provided near the incident end surface on the front surface and / or the rear surface. Increase By providing a light guide plate provided as described above and a reflector having a reflective property covering a portion other than the incident end face portion and the emission surface of the light guide plate and having a reflective surface having a concave-convex shape or a prism shape, the light guide plate has Even if the existing light beam travels from the incident end face to the anti-incident end face located on the opposite side of the incident end face, no taper leak occurs.When the light ray is totally reflected at the anti-incident end face and heads again to the incident end face, it is tapered for the first time. Since leakage can occur, high-intensity light from the light source is not emitted in the vicinity of the incident end face, but is emitted after being totally reflected once on the opposite side of the incident end face of the light guide plate. Since the light travels through the light guide plate while repeating total reflection several times, it is possible to eliminate glare and uneven brightness of the light source, and even in the case of a light source in which monochromatic light sources such as RGB are arranged, light can be emitted immediately near the incident end face. In order to emit light after being totally reflected once on the side opposite to the incident end face of the light guide plate, RGB monochromatic light is mixed and travels while repeating total reflection several times in the light guide plate during that time to produce perfect white light. It is possible to control the luminance unevenness and the luminescent color unevenness together with the luminance, and also take a large use exit surface of the light guide plate. It is an object of the present invention to provide a light guide plate and a planar lighting device that can obtain mechanically excellent strength because the thickness becomes minimum and the central portion has the maximum thickness.
[0015]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the light guide plate according to claim 1 of the present invention has a thin rectangular cubic shape, and six surfaces surrounding the light guide plate have a mirror surface, and fine light is provided on a front surface portion and / or a rear surface portion. It is characterized in that the deflecting element is provided and the distance between the front surface portion and the back surface portion is minimized at the incident end face portion, and the distance is maximized at the maximum distance from the incident end face portion.
[0016]
The light guide plate according to claim 1 has a thin rectangular cubic shape, six surfaces surrounding them are mirror surfaces, and a fine light deflecting element is provided on a front surface portion and / or a rear surface portion. The distance between the light source and the light source is minimized at the incident end face, and the distance is maximized at the maximum distance from the incident end face. While the light guide plate is wedge-shaped, there is no ray that breaks the critical angle while traveling to the anti-incident end face located on the opposite side of the light guide plate. There are many rays that break the critical angle and rays that are close to the critical angle when the rays totally reflected by the light again travel in the direction of the incident end face, etc. Control the amount of emitted light No reflection of the light source it is possible to, it is possible to obtain a bright and uniform light emitted no dark portion to both ends of the incident end face of the incident end face neighborhood.
[0017]
The light guide plate according to claim 2 is characterized in that the number or area of the light deflecting elements increases as the light deflecting elements are closer to the incident end face.
[0018]
In the light guide plate according to claim 2, since the number or area of the light deflecting elements increases as the light deflecting element approaches the incident end face, light incident from the incident end face reaches the front surface or the rear surface of the light guide plate. There is also no light reaching the critical angle, and there are many rays that break the critical angle or light near the critical angle, etc. Since it is necessary to increase the amount of light to be emitted closer to the incident end face to emit from the exit face while returning from the part to the incident end face, the number or area of the light deflecting elements increases as the closer to the incident end face. Thus, more uniform outgoing light can be obtained.
[0019]
Furthermore, the flat lighting device according to claim 3 is a light source having directivity, an incident end face portion for guiding light from the light source, a front surface portion and / or a back surface portion for emitting the light, and the front surface portion and the back surface portion. And a thin plate-shaped rectangular cubic shape having side surfaces that intersect at right angles to the surface, and six surfaces surrounding them form a mirror surface, and a fine light deflecting element is provided on the front surface portion and / or the rear surface portion. The light guide plate where the distance between the light guide plate and the back surface is minimized at the incident end face, and the distance is the largest at the maximum distance from the incident end face, and the reflectivity covering portions other than the incident end face and the exit surface of the light guide plate And a reflector having
[0020]
The flat lighting device according to claim 3 includes a light source having directivity, an incident end face portion for guiding light from the light source, a front surface portion and / or a rear surface portion for emitting the light, and a front surface portion and a rear surface portion. It has the shape of a thin rectangular cube having side surfaces that intersect at a substantially right angle. The six surfaces surrounding these form a mirror surface, and a fine light deflecting element is provided on the front surface and / or the rear surface. The light guide plate is such that the distance between the light guide plate and the light guide plate is minimized at the incident end face, and the distance is the largest at the maximum distance from the incident end face. Since the light from the light guide plate is wedge-shaped, there is no light beam that breaks the critical angle while the incident light from the incident end face advances to the anti-incident end face located on the opposite side of the incident end face. Directivity because no taper leak occurs Even with a strong light source, the shape of the light source such as the semiconductor light emitting element itself and the emitted light of light brightness near the incident end face does not have any observation (reflection) or luminance unevenness from the emitting face, and is totally reflected at the anti-incident end face. There are many rays that break the critical angle when the light travels in the direction of the incident end face and rays that are close to the critical angle.When the light reaches the fine optical deflection element with taper leak, the critical angle is broken and the amount of light emitted from the light guide plate is controlled. Brightness uniformity is obtained by eliminating luminance unevenness, and bright and uniform outgoing light is obtained without dark areas at both ends of the incident end face near the incident end face. Therefore, even in the case of a light source in which monochromatic light sources such as RGB are arranged, the light is not emitted immediately near the incident end face, so that the occurrence of luminescent color spots can be avoided, and the incident light is once incident on the light guide plate. Since the light is emitted after being totally reflected on the opposite side of the surface portion, the light travels while repeating the total reflection several times in the light guide plate, so that the RGB monochromatic light is mixed to obtain a complete white light. Use of the light plate A large exit surface can be obtained, and even for large light guide plates and flat lighting devices, the incident end surfaces at both ends near the light source are the minimum and the central part has the maximum thickness, so the mechanical strength increases structurally, Excellent.
[0021]
In the flat lighting device according to claim 4, the light source having directivity is composed of a plurality of semiconductor light emitting elements, and is monochromatic light or red light, green light, three primary colors of blue light, or white light using a wavelength conversion material. In addition, these are characterized in that they are configured as a single unit or an array.
[0022]
The flat lighting device according to claim 4, wherein the light source having directivity is composed of a plurality of semiconductor light emitting elements, and is monochromatic light or red light, green light, three primary colors of blue light or white light using a wavelength conversion material. Is formed as a single unit or in an array, so that high-luminance emission light can be obtained and high-luminance white light can be emitted according to the purpose. Thus, it is possible to obtain outgoing light without observation (reflection) or uneven brightness.
Further, the flat lighting device according to the fifth aspect is characterized in that the reflecting surface of the reflector has an uneven shape or a prism shape.
[0024]
In the flat lighting device according to the fifth aspect, since the reflecting surface of the reflector has a concave-convex shape or a prism-like shape, a light beam or an outgoing surface that travels from the incident end surface to the opposite incident end surface located on the opposite side of the incident end surface is formed. The light emitted to the opposite surface or the leaked light can be returned to the light guide plate more reliably, and the position to return to the light guide plate can be controlled by controlling the uneven shape and prism shape. Further, when the light source is light of three primary colors such as RGB, the light of the three primary colors can be mixed in the light guide plate by reflection by the prism surface.
[0025]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
According to the present invention, the light guide plate has a thin plate-like rectangular cubic shape, and six surfaces surrounding the light guide plate form a mirror surface, and a fine light deflecting element is provided near the incident end surface on the front surface and / or the rear surface. The distance (thickness) between the front surface portion and the back surface portion is minimized at the incident end surface portion, and the distance (thickness) between the front surface portion and the back surface portion at the maximum distance from the incident end surface portion is increased. The light source is composed of a plurality of semiconductor light-emitting elements having directivity, and is monochromatic light or three primary colors of red light, green light and blue light or white light using a wavelength conversion material. It consists of a single semiconductor light emitting element having an array or directivity. A light source in the vicinity of the incident end face of the light guide plate, comprising: a reflector having a reflectivity that covers portions other than the incident end face and the exit face of the light guide plate, and the reflective face having an irregular shape or a prism shape. It is an object of the present invention to provide a light guide plate and a planar lighting device which can control the reflection of light, the occurrence of luminance unevenness, and the occurrence of luminescent color unevenness, and can take a large emission surface of the light guide plate.
[0026]
FIG. 1 is an exploded perspective view showing a schematic configuration of a plain illumination device including a light guide plate according to the present invention, FIG. 2 is a side view of the light guide plate according to the present invention, and FIG. 3 shows a trajectory of light rays in the light guide plate of FIG. FIGS. 4 (a) and 4 (b) show the trajectories of light rays when one light source is arranged at the center of the incident end face in the light guide plate of FIG. 2, and FIG. 5 shows the light guide plate of the present invention. It is a side view which shows another shape.
[0027]
As shown in FIG. 1, the flat lighting device 1 includes a light guide plate 2, a light source 9, and a reflector 10.
[0028]
The light guide plate 2 is formed of a transparent acrylic resin (PMMA) having a refractive index of about 1.4 to 1.7, polycarbonate (PC), or the like. The light guide plate 2 includes an incident end face 3 for guiding light from the light source 9, a counter-incident end face 4 located on the opposite side to the incident end face 3, and both ends of the incident end face 3 and the anti-incident end face 4. , A front surface portion 6 for emitting light, and a back surface portion 7 located on the opposite side to the front surface portion 6. A light deflecting element 8 for totally reflecting or refracting light is provided on the front surface portion 6 and the rear surface portion 7.
[0029]
In the light guide plate 2, the distance (the thickness of the light guide plate 2) between the front surface portion 6 and the back surface portion 7 is minimized (thin) at the incident end surface portion 3, and the maximum distance (incident end surface portion) from the incident end surface portion 3. 3 (a distance from the incident end surface portion 4 located on the opposite side of the incident end surface portion 3) to the maximum (thick).
Therefore, as shown in FIG. 2, the light guide plate 2 has the light source 9 disposed in the vicinity of the thin incident end portion 3 substantially parallel to the incident end surface portion 3, and the incident end surface portion on which the light source 9 is disposed. The thickness of the anti-incident end face portion 4 which is on the opposite side (maximum separation distance) of the light incident end 3 is thick.
[0030]
Further, a light deflecting element 8 is provided on the front surface portion 6 and the back surface portion 7. In the example of FIG. 1, the light deflecting element 8 is provided only on the surface portion 6. Thereby, while the incident light from the incident end face 3 proceeds to the opposite incident end face 4 located on the opposite side of the incident end face 3, even if the light guide plate 2 has a wedge shape, there is no ray that breaks the critical angle. The light is totally reflected by the anti-incident end face 4. The light ray totally reflected by the anti-incident end face part 4 is refracted by the light deflecting element 8 when traveling in the direction of the incident end face part 3 again, and can be emitted from the surface part 6 after breaking the critical angle.
[0031]
As shown in FIG. 3, the light incident on the light guide plate 2 has a refraction angle γ of 0 ≦ | γ | ≦ sin. ^-1 The light travels into the light guide plate 2 within a range satisfying the expression (1 / n). For example, the refractive index of an acrylic resin which is a resin material used for a general light guide plate 2 is about n = 1.49. Therefore, the maximum incident angle is 90 ° for the light from the direction of the front surface 6 to the direction of the back surface 7 and the light from the direction of the back surface 7 to the direction of the front surface 6 of the incident end face 3. For this reason, the refraction angle γ refracted at the incident end face 3 is in the range of γ = 0 to ± 42 °.
However, in the vicinity of the front surface portion 6, only γ = −42 ° only in the direction of the back surface portion 7, and in the vicinity of the back surface portion 7, only γ = + 42 ° only in the direction of the front surface portion 6.
[0032]
Here, the light incident on the light guide plate 2 within the range of the refraction angle γ = 0 to ± 42 ° is sin α = (1/1/2) at the interface between the light guide plate 2 and the air layer (refractive index n = 1). The critical angle can be expressed by the equation of n). For example, since the refractive index of an acrylic resin which is a resin material used for the general light guide plate 2 is about n = 1.49, the critical angle α is about α = 42 °. Therefore, if there is no convex or concave portion for deflecting the light beam on the front surface portion 6 or the rear surface portion 7 of the light guide plate 2 or the critical angle α is not exceeded, all the light in the light guide plate 2 is transmitted through the front surface portion 6 and the rear surface portion 7. The light travels in the direction of the anti-incident end face 4 while undergoing total reflection.
[0033]
However, in the light guide plate 2 of the present invention, the thickness of the light guide plate 2 (the distance between the front surface portion 6 and the back surface portion 7 of the light guide plate 2) is located on the opposite side from the incident end surface portion 3 to the incident end surface portion 3. As the light guide plate 2 has a wedge shape (in general or contrary to the conventional shape) in which the thickness of the light guide plate 2 becomes thinner (minimized) toward the opposite incident end surface portion 4 (maximum distance from the incident end surface portion 3), FIG. As shown, there is no ray that breaks the critical angle even when the light guide plate 2 is wedge-shaped while the incident light Ln1 from the incident end face 3 travels to the anti-incident end face 4 located on the opposite side of the incident end face 3. The light beam Ln2 which has been repeatedly totally reflected on the front surface portion 6 and the back surface portion 7 is totally reflected on the opposite incident end face portion 4.
Then, when the light beam Ln3 advances again in the direction of the incident end face portion 3, the light deflection element 8 performs refraction or the like to break the critical angle and emit the light beam Ln4 from the surface portion 6.
Here, the convex and concave shapes of the light deflecting element 8 have been described, but in each case, the light is refracted by the convex or concave inclined surface and emitted to the outside.
[0034]
Further, although not shown, the light guide plate 2 of the present invention is provided with the light deflecting elements 8 on the front surface portion 6 and the rear surface portion 7 so that the number or the area of the light deflecting elements 8 increases as approaching the incident end surface portion 3. As a result, the light initially incident from the incident end face 3 from the light source 9 does not reach the critical angle α even if it reaches the front face 6 or the back face 7 of the light guide plate 2, and the light that reaches the critical angle α does not exist. While repeating total reflection in the section 7, the light advances to the anti-incident end face 4 on the opposite side of the incident end face 3, and is totally reflected by the anti-incident end face 4. In the process in which the totally reflected light returns to the direction of the incident end face portion 3, there are many light rays that break the critical angle α and light rays that are close to the critical angle α because the thickness of the light guide plate 2 is gradually reduced. For this reason, of the light that has advanced in the direction of the incident end face portion 3 again due to the total reflection, a ray near the critical angle α is refracted by the inclined surface of the light deflection element 8 while returning from the anti-incident end face portion 4 to the incident end face portion 3. Are emitted from the emission surface (surface portion 6).
[0035]
Further, the light is emitted from the emission surface (surface portion 6) while returning from the anti-incident end surface portion 4 to the incident end surface portion 3, and the more the light is, the closer to the incident end surface portion 3 (the more the light returns), the more the light quantity is reduced. Are emitted from the emission surface (surface portion 6). For this reason, it is necessary to increase the amount of light to be emitted closer to the incident end face 3, and the number or area of the light deflecting elements 8 increases as the distance approaches the incident end face 3, whereby uniform emitted light can be obtained.
[0036]
Further, even when the light source 9 is a single light, the light once totally reflected by the anti-incident end face 4 on the opposite side of the incident end face 3 travels to the entire incident end face 3, and the light is deflected in the direction of the incident end face 3. The number or area of the light deflecting elements 8 increases as the elements 8 are closer to the incident end face portion 3. Thereby, even outgoing light can be obtained at both ends of the incident end face portion 3 which are both ends of the light source 9.
[0037]
Further, in the case of the flat lighting device 1 having a large screen size, the light guide plate 2 has a structure in which both ends of the light guide plate 2 are provided with the incident end face portions 3. The distance between them (thickness of the light guide plate 2) is minimized (thin) at the incident end face 3 and the distance (thickness) is maximum (thick) at the center from the incident end face 3 at both ends. .
[0038]
That is, as shown in FIG. 5, the planar lighting device 1 has two light sources 9a and 9b as the light sources 9, and the light guide plate 2 opposed to the two light sources 9a and 9b has the thinnest ends. The part is an incident end face part 3 (3a, 3b). Then, the thickness of the light guide plate 2 becomes thicker toward the center direction from the incident end face portions 3a, 3b, and the distance between the front surface portion 6 and the back surface portion 7 (7a, 7b) toward the center direction at the center is maximum. become.
[0039]
Therefore, the light guide plate 2 is configured such that the thickness of the light guide plate 2 (the distance between the front surface portion 6 and the back surface portion 7a and the back surface portion 7b of the light guide plate 2) is changed from each incident end surface portion 3a and each incident end surface 3b. The light guide plate 2 has such a shape that the thickness of the light guide plate 2 becomes thicker (maximum) toward the opposite side of the end face part 3a and the incident end face part 3b (center from each of the incident end face part 3a and the incident end face part 3b).
As a result, there is no ray that breaks the critical angle up to the center even if the light guide plates 2 are tapered while the incident light from each of the incident end faces 3a and 3b travels to the center. The light rays that have been totally reflected at the front surface portion 6 and the back surface portion 7 are totally reflected within the light guide plate 2 facing each other and at the incident end face portions 3a and 3b facing each other, and are again incident on each other. When the light beam travels in the directions of the incident end face 3a and the incident end face 3b, the light is deflected by the light deflecting element 8 to break the critical angle and emit the light from the surface 6.
[0040]
Further, as shown in FIGS. 4A and 4B, even when only one light source 9 made of a semiconductor light emitting element or the like (LED or the like) is provided at the center of the incident end face 3, the light source 9 emits the semiconductor light. The light beam travels in the direction of the anti-incident end face 4 in a narrow range because of the elements and the like. However, while traveling from the incident end face 3 to the direction of the anti-incident end face 4, there is no light beam that breaks the critical angle. And the light Ln breaks the critical angle while traveling in the direction of the incident end face portion 3 again. Further, the light deflecting element 8 provided on the surface portion 6 allows the light near the critical angle to be deflected by the inclined surface of the light deflecting element 8. Since refraction or the like can be caused to emit a larger number of light beams to the surface portion 6, uniform and bright emitted light can be obtained without dark portions at both ends of the incident end face portion 3. On the other hand, in the conventional configuration as shown in FIGS. 9A and 9B, dark portions are formed at both ends of the incident end face.
[0041]
As described above, the light guide plate 2 of the present invention is configured such that the thickness of the light guide plate 2 is the thinnest at the position of the incident end face portion 3, and the thickness of the light guide plate 2 becomes thicker as the distance from the incident end face portion 3 increases. The light beam first incident on the light guide plate 2 from the light source 9 is totally reflected only by the mirror surface such as the front surface portion 6 and the back surface portion 7, and is totally reflected by the anti-incident end surface portion 4 located on the opposite side of the incident end surface portion 3. After that, the light travels in the direction of the incident end face portion 3 again. At this time, the thickness of the light guide plate 2 is gradually reduced. The light near the critical angle is refracted by the inclined surface of the light deflecting element 8 by the element 8, and more light rays are emitted to the surface portion 6.
[0042]
In addition, when the incident end portions 3 are provided at both ends of the light guide plate 2, the thickness of the light guide plate 2 is thinnest at the position of the incident end portion 3, and the thickness of the light guide plate 2 increases as the distance from the incident end portion 3 increases. And the light guide plate 2 is configured such that the thickness of the light guide plate 2 is the thickest at the center portion at the same distance from both ends of the light guide plate 2. The light guide plate 2 is only totally reflected by the mirror surface such as the rear surface portion 7 and the like, and the thickness of the light guide plate 2 is gradually reduced from a position beyond the center portion. The light deflecting element 8 provided at 6 causes the light near the critical angle to be refracted by the inclined surface of the light deflecting element 8 and emits more light rays to the surface portion 6.
Therefore, in the vicinity of the incident end face 3, the light from the light source 9 does not directly emit (reflect) high-brightness light, but emits light that is bright and spot-free throughout the light guide plate 2. In particular, both ends of the light guide plate 2 In the case where the incident end face portion 3 is provided, the mechanical strength is excellent.
[0043]
The light source 9 is a semiconductor light emitting element, and is composed of an LED, a laser, or the like, and provides each monochromatic light of RGB (red, green, blue) in the vicinity of each of the incident portions 3 or RGB (red light, green light, blue light). An array-shaped unit in which a plurality of semiconductor light-emitting elements (emission) are combined may be provided in each of the incident portions 3.
Further, the light source 9 may be a light source that emits white light using a wavelength conversion material (for example, a light source in which a blue light emitting element is combined with a yellow fluorescent agent or the like).
[0044]
The light source 9 may use a CCFL (cold cathode tube) when the incident end face 3 is large or when the light guide plate 2 itself is large. In this case, the light source 9 has a linear shape, and direct light enters the light guide plate 2 from the incident end face 3 of the light guide plate 2, and a space between the light source 9 and the reflector while other light is reflected by a reflector (not shown). Through the light guide plate 2.
In the case of the linear light source 9, a bright line with high brightness appears near the incident end face 31 in the conventional light guide plate 21, but the use of the light guide plate 2 of the present invention causes the generation of a bright line. Can be prevented.
[0045]
Although not shown, the reflecting body 10 has a reflecting surface having an uneven shape or a prism shape, and a sheet in which a white material such as titanium oxide is mixed in a thermoplastic resin or a sheet of a thermoplastic resin is subjected to metal evaporation such as aluminum. Or a sheet metal having a laminated metal foil. The reflector 10 covers portions other than the incident end face portion 3 and the surface portion 6, and reflects or diffusely reflects light other than the light from the light source 9 emitted to the surface portion 6 by the light guide plate 2. All the light from the light source 9 is emitted from the surface portion 6 by being incident.
Further, by controlling the uneven shape and prism shape of the reflector 10 used for the anti-incident end face portion 4 and the back surface portion 7, the position of returning to the inside of the light guide plate 2 is controlled, and the brightness, light amount distribution, The emission angle and the like can be adjusted.
[0046]
Furthermore, the reflector 10 may have a concave-convex shape or a prism-shaped reflective surface. Thereby, the light source 9 can mix the light of the three primary colors such as RGB in the light guide plate 2 by reflection by the prism surface, and convert the light from the light source 9 into the light emitted from the light guide plate 2 without wasting. Efficiency can be improved.
[0047]
Although not shown here, for example, when the light source 9 has a directivity such as a CCFL (cold cathode tube) indicating a radial direction, a reflector is provided around the light source 9 (CCFL), and the light guide plate 2 is provided with a reflector. It surrounds the incident end face 3 and the light source 9. As a result, the light from the light source 9 is reflected, and the reflected light is made incident again on the incident end face 3 of the light guide plate 2.
The reflector is formed of a sheet-like material or a metal on which a white insulating material or a metal such as aluminum is deposited.
[0048]
Further, although not shown here, as a realistic flat lighting device 1, light rays that break the critical angle from the light guide plate 2 and exit to the surface section 6 or the like have a large incident angle with respect to the surface section 6 and therefore have a large exit angle. Become. This means that the angle formed between the surface portion 6 and the outgoing light becomes small, and the outgoing light becomes as if it were along the light guide plate 2. Therefore, for example, for a liquid crystal display device or the like, light that is substantially perpendicular to the light guide plate 2 is required. Therefore, a prism sheet is used for the light emission surface (surface portion 6) of the light guide plate 2.
At this time, the prism surface (the ridge of the prism) of the prism sheet is arranged toward the light guide plate 2, and the emitted light along the light guide plate 2 is once taken into the prism sheet, and the light is emitted from the surface opposite to the taken-in surface. The light is totally reflected, and finally substantially perpendicular emission light is obtained from the flat lighting device 1.
[0049]
【Example】
FIG. 10A shows the results of measured values using the light guide plate of the present invention and the conventional light guide plate, and FIG. 10B shows how to divide the light guide plate region when measuring the average luminance. FIG.
[0050]
The measurement conditions are such that the thickness of the light guide plate is a wedge shape with a minimum of 0.9 mm to a maximum of 1.3 mm. In the light guide plate of the present invention, a portion having a thickness of 0.9 mm is defined as an incident end face, and a light source is arranged near the incident end face. On the other hand, in the conventional light guide plate, a portion having a thickness of 1.3 mm is used as an incident end face, and a light source is arranged near the incident end face. Further, the same size is used for the present invention and the conventional light guide plate. The light source used was one in which four semiconductor light emitting devices (L7555 manufactured by Nippon Lights Co., Ltd.) were arranged in parallel to the incident end face. The input current of the light source is 18 mA per chip. The prism film and the reflection film used were manufactured by Sumitomo 3M Limited. The luminance meter is Topcon BM-7 (viewing angle 1 °), and the unit of the numerical value is Cd / m ² It is.
[0051]
As is clear from the measurement results shown in FIG. 10A, the average luminance and the central luminance of all the three regions of the light guide plate are higher when the light guide plate of the present invention is used. The result was higher than the case where the conventional light guide plate was used. Further, with respect to luminance unevenness, a result was obtained in which the light guide plate of the present invention was less (substantially half) than the conventional light guide plate.
As shown in FIG. 10B, the average luminance was measured by dividing the light source into three areas A, B, and C from the incident end face where the light source was opposed to the opposite incident end face. .
[0052]
As described above, in the light guide plate and the planar lighting device of the present invention, the thickness of the light guide plate 2 is the smallest at the position of the incident end face portion 3, and the thickness of the light guide plate 2 becomes thicker as the distance from the incident end face portion 3 increases. Configuration. Accordingly, when the light travels from the incident end face 3 toward the anti-incident end face 4 located on the opposite side of the incident end face 3 (this direction is referred to as a forward direction), more total reflection is performed on the mirror surface of each surface of the light guide plate 2. . Then, the totally reflected light beam reaches the anti-incident end face portion 4, performs total reflection on the anti-incident end face portion 4, and then proceeds again to the incident end face portion 3 (this direction is referred to as a reverse direction). When the light travels in the opposite direction, the thickness of the light guide plate 2 becomes gradually thinner, so that the light beam breaks the critical angle α while traveling and exits from the surface portion 6. Moreover, the light deflecting element 8 provided so that the distribution amount increases as it approaches the incident end face 3 of the surface portion 6 causes the light near the critical angle α to be refracted by the inclined surface of the light deflecting element 8, so that a larger number of light Is emitted to the surface portion 6 and uniform and high-intensity emitted light can be obtained.
[0053]
Similarly, when the incident end surfaces 3a and 3b are provided at both ends of the light guide plate 2, the thickness of the light guide plate 2 is the thinnest at the positions of the incident end surfaces 3a and 3b, and the light guide plate is located at the center of the light guide plate 2. 2 has the largest thickness. Thus, in the forward direction from the two incident end portions 3a and 3b toward the center of the light guide plate 2, only the total reflection is performed on the mirror surface of each surface, and the reverse direction from the position beyond the center to the opposite incident end portion. As the light guide plate 2 gradually becomes thinner toward, the light beam breaks the critical angle α while traveling and exits from the surface portion 6. Further, the light near the critical angle α is refracted by the inclined surface of the light deflecting element 8 by the light deflecting element 8 provided so that the distribution amount increases as the distance from the incident end surfaces 3a and 3b of the front surface 6 increases. Is emitted to the surface portion 6 and uniform and high-brightness emitted light can be obtained.
[0054]
Therefore, in the vicinity of the incident end face 3, the light from the light source 9 directly emits high-brightness light, that is, light that is bright and has no spots on the entire light guide plate 2 without emitting so-called reflection. In particular, when the incident end face portions 3a and 3b are provided at both ends of the light guide plate 2, the mechanical strength is excellent, and a substantially large exit surface can be ensured by no reflection. Even when a white light source of three primary colors (RGB) is used as the light source 9, the light does not exit near the incident end face 3, so that the respective color (RGB) rays are mixed while traveling in the opposite direction to the incident end face, and the critical When the angle α is broken, the light can be emitted as complete white light.
[0055]
When only one light source 9 having directivity, such as a semiconductor light emitting element, is provided at the center of the incident end face 3, the luminous flux travels in the narrow direction toward the anti-incident end face 4. For this reason, in the conventional configuration, both end portions of the incident end face portion 3 of the light guide plate 2 become dark portions. On the other hand, in the configuration of the present invention, while traveling from the incident end face 3 toward the anti-incident end face 4, there is no ray that breaks the critical angle α, and the ray Ln is totally reflected by the anti-incident end face 4 and is reflected by the light Ln. Breaks the critical angle while traveling in the direction of the incident end face portion 3 again, and furthermore, the light near the critical angle α is refracted by the inclined surface of the light deflecting element 8 by the light deflecting element 8 provided on the surface portion 6, and more light rays are scattered. Can be emitted to the surface portion 6. As a result, dark portions are not formed at both ends of the incident end face portion 3, and uniform and bright emitted light can be obtained.
[0056]
【The invention's effect】
As described above, the light guide plate according to claim 1 has a thin plate-shaped rectangular cubic shape, and the six surfaces surrounding them have a mirror surface, and a fine light deflecting element is provided on the front surface portion and / or the rear surface portion. At the same time, the distance between the front surface and the back surface is minimized at the incident end face, and the distance is maximized at the maximum distance from the incident end face, so that the light from the light source enters the light guide plate without distortion at the incident end face. There is no ray that breaks the critical angle even if the light guide plate is wedge-shaped while taking in and going to the anti-incident end face part located on the opposite side of the incident end face part, while totally reflecting many rays on each face of the light guide plate There are many rays that break the critical angle or rays close to the critical angle when the ray totally reflected at the anti-incident end face travels toward the incident end face again, and the critical angle is reached when reaching the fine optical deflection element with taper leak. The amount of light emitted from the light guide plate No light reflection of it is possible to control, it is possible to obtain a bright and uniform light emitted no dark portion to both ends of the incident end face of the incident end face neighborhood. Moreover, the area of the light guide plate that can be actually used can be increased accordingly, and even if the light sources are arranged in parallel (array shape), the light from adjacent light sources is not overlapped to prevent the occurrence of luminance unevenness. In addition, when the size is increased, the light guide plate is excellent in mechanical stability and strength because the thickness of the central portion is the largest because both ends are the incident end face portions.
[0057]
Further, in the light guide plate according to claim 2, since the number or area of the light deflecting elements increases as the light deflecting elements are closer to the incident end face, light incident from the incident end face is directed to the front surface and the back surface of the light guide plate. Even when the light reaches the critical angle, there is no light that reaches the critical angle. Since it is necessary to increase the amount of light to be emitted closer to the incident end face in order to exit from the exit face while returning from the incident end face to the incident end face, the number or area of the light deflecting elements increases closer to the incident end face. By doing so, uniform outgoing light can be obtained. Further, even in the case of a single light source, the light once totally reflected by the anti-incident end face on the opposite side of the incident end face advances to the entire incident end face, and the light deflecting element approaches the incident end face as it proceeds in the direction of the incident end face. As the number or area of the light deflecting elements increases, uniform outgoing light can be obtained even at both ends of the incident end face, which is both ends of the light source.
[0058]
Furthermore, the flat lighting device according to claim 3 is a light source having directivity, an incident end face portion for guiding light from the light source, a front surface portion and / or a back surface portion for emitting the light, and the front surface portion and the back surface portion. And a thin plate-shaped rectangular cubic shape having side surfaces that intersect at right angles to the surface, and six surfaces surrounding them form a mirror surface, and a fine light deflecting element is provided on the front surface portion and / or the rear surface portion. The light guide plate where the distance between the light guide plate and the back surface is minimized at the incident end face, and the distance is the largest at the maximum distance from the incident end face, and the reflectivity covering portions other than the incident end face and the exit surface of the light guide plate While the light from the incident end face advances to the anti-incident end face located on the opposite side of the incident end face, a light beam that breaks the critical angle even if the light guide plate has a wedge shape is provided. There is no taper leak Even with a light source with strong directivity, the shape of the light source such as the semiconductor light emitting element itself and the emitted light of the light intensity near the incident end face is free from observation (reflection) and uneven brightness from the exit face, and total reflection is achieved at the anti-incident end face. There are many rays that break the critical angle when the rays advance in the direction of the incident end face and rays that are close to the critical angle, etc., and when the light reaches the fine optical deflecting element with taper leak, it breaks the critical angle and exits from the light guide plate. By controlling the amount of light, uniform brightness can be obtained by eliminating uneven brightness, and bright and uniform emitted light can be obtained without dark portions at both ends of the incident end face near the incident end face. In addition, since a tapered leak can be caused only by the light totally reflected at the anti-incident end face, even in the case of a light source in which monochromatic light sources such as RGB are arranged, the light is not immediately emitted in the vicinity of the incident end face and emission color spots are generated. Since the incident light is totally reflected once on the side opposite to the incident end face of the light guide plate and then emitted, the light travels inside the light guide plate while repeating the total reflection several times. For this reason, complete white light can be obtained by mixing the RGB monochromatic lights. In addition, the light exit surface of the light guide plate can be made large, and even with a large light guide plate or flat lighting device, the incident end face portions at both ends near the light source are the smallest and the central portion has the largest thickness, so it is mechanically excellent. The size of the light guide plate can be adapted to the size of the flat lighting device without requiring a light guide plate larger than necessary, and is mechanically stable even when the weight is reduced (the overall thickness is reduced). (Excellent strength) can be obtained.
[0059]
In the flat lighting device according to claim 4, the light source having directivity is composed of a plurality of semiconductor light emitting elements, and is monochromatic light or red light, green light, three primary colors of blue light, or white light using a wavelength conversion material. In addition, since these are configured as a single unit or an array, it is possible to obtain high-luminance emission light and to emit high-luminance white light according to the purpose. In addition, by forming the light source in an array, the shape of the light source can be observed (reflected) from the emission surface and emission light without luminance unevenness can be obtained, and high-luminance white light can be emitted according to the purpose. Therefore, clear white light or monochromatic light can be obtained.
[0060]
Furthermore, in the flat lighting device according to the fifth aspect, since the reflecting surface of the reflector has a concave-convex shape or a prism-like shape, the light beam or the light traveling from the incident end face to the counter-incident end face located on the opposite side to the incident end face is output. It is possible to control the position where the light beam emitted from the surface opposite to the surface, the leaked light beam, and the like are returned to the inside of the light guide plate more reliably. This makes it possible to adjust the brightness, the light amount distribution, the emission angle, and the like of the final emission light. Furthermore, when the light source is light of three primary colors such as RGB, the light of the three primary colors can be mixed in the light guide plate by reflection by the prism surface, so that the light from the light source is converted to light emitted from the light guide plate without wasting. The efficiency to do is excellent.
[Brief description of the drawings]
FIG. 1 is an exploded perspective view showing a schematic configuration of a plain lighting device including a light guide plate according to the present invention.
FIG. 2 is a side view of the light guide plate according to the present invention.
FIG. 3 is a diagram showing a trajectory of a light beam in the light guide plate of FIG. 2;
FIGS. 4A and 4B are diagrams showing the trajectories of light rays when one light source is arranged at the center of the incident end face in the light guide plate of FIG. 2;
FIG. 5 is a side view showing another shape of the light guide plate according to the present invention.
FIG. 6 is a perspective view of a conventional light guide plate.
FIG. 7 is a side view showing a schematic configuration of a conventional planar lighting device including a light guide plate having another shape.
FIG. 8 is a diagram showing a trajectory of a light beam in the light guide plate of FIG. 6;
9 (a) and 9 (b) are diagrams showing trajectories of light rays when one light source is arranged at the center of the incident end face in the light guide plate of FIG. 6;
FIG. 10 (a) is a diagram showing the results of measurement values using the light guide plate of the present invention and a conventional light guide plate.
(B) A diagram showing how to divide the area of the light guide plate when measuring the average luminance.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Planar illumination device, 2, 21, 21A ... Light guide plate, 6, 61 ... Surface part, 7, 71 ... Back part, 3, 31 ... Incident end face part, 4, 41 ... Anti-incident end face part, 5, 51 ... Side surface part, 8: light deflecting element, 9, 9a, 9b 91a, 91b: light source, 10: reflector, Ln, Ln1, Ln2, Ln3. Ln4, L0, L01, L02, L03, L04 ... light rays.

Claims (5)

A light guide plate having an incident end face portion for guiding light from a light source having directivity, a front surface portion and / or a rear surface portion for emitting the light, and a side surface portion that intersects the front surface portion and the rear surface portion at a substantially right angle. In addition, a thin plate-shaped rectangular cubic shape is formed, and six surfaces surrounding them form a mirror surface, and a fine light deflecting element is provided on the front surface portion and / or the rear surface portion. The light guide plate is characterized in that the distance between the light guide plates becomes minimum at the incident end face, and the distance becomes maximum at the maximum distance from the incident end face. 2. The light guide plate according to claim 1, wherein the number or area of the light deflecting element increases as the light deflecting element approaches the incident end face. 3. A light source having directivity, an incident end surface portion for guiding light from the light source, a front surface portion and / or a rear surface portion for emitting the light, and a side surface portion that intersects the surface portion and the rear surface portion at a substantially right angle. It has a thin plate-shaped rectangular cuboidal shape, and six surfaces surrounding these form a mirror surface, and a fine light deflecting element is provided on the front surface portion and / or the rear surface portion. The distance between the light guide plate is minimized at the incident end face portion, and the distance is maximized at the maximum distance from the incident end face portion, and the reflectivity covering portions other than the incident end face portion and the emission surface of the light guide plate. And a reflector having the following. The light source is composed of a plurality of semiconductor light-emitting elements having directivity, and is monochromatic light or red light, green light, white light using three primary colors of blue light or wavelength conversion material, and these are configured as a single unit or an array. The flat lighting device according to claim 3, wherein: 4. The flat lighting device according to claim 3, wherein the reflector has a concave or convex shape or a prism shape.

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