JP4588729B2 - Flat lighting device - Google Patents

Description

  In the present invention, the thickness of the light guide plate is set so that the position of the incident end face is minimized, and even if the light from the light source has directivity, strong light from the light source is not reflected near the incident end face. In addition, the present invention relates to a flat illumination device capable of avoiding the occurrence of dark portions at both end portions near the incident end surface portion of the light guide plate when there are few light sources.

  As a conventional light guide plate and flat illumination device, for the purpose of maximizing the light from the light source, the thickness of the light guide plate is decreased as the distance from the incident end surface portion increases. A method using 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), an incident end surface portion 31, a front surface portion 61, a back surface portion 71, a front surface portion 61 and a back surface. Side portions 51, 51 intersecting with the portion 71 at substantially right angles. The light guide plate 21 has a thicker side as an incident end surface portion 31, and the thickness decreases toward the counter incident end surface portion 41 b opposite to the incident end surface portion 31. Then, a light source is disposed opposite to the incident end face portion 31, and light is emitted from the front surface portion 61 and / or the back surface portion 71 using a taper leak of light traveling from the incident end face portion 31 toward the counter incident end face portion 41. is doing.

  Further, in the case of a large flat illumination device, as shown in FIG. 7, the light guide plate 21A is configured so that the thickness of the light guide plate 21A decreases from the incident end face portions 31a and 31b at both ends toward the center. Is done. In the flat illumination device using the light guide plate 21A, the light sources 91a and 91b are arranged on the incident end face portions 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 using a taper leak of light traveling from the incident end surface portions 31a and 31b in the opposite direction to the incident end surface portions 31a and 31b.

  In addition, when printing a white light scattering agent on the opposite side of the exit surface of the conventional light guide plate, it is incident even when the printed portion is increased away from the incident end face portion or dots such as irregularities are provided on the light guide plate. The dots were increased as the distance from the end face portion increased.

  Furthermore, as a conventional flat illumination device using a point light source such as an LED as a light source, a plurality of LEDs are arranged on the side surface of the light guide plate, and a convex or concave portion such as a prism is formed on the incident end surface portion of the light guide plate at a position facing these LEDs. There is known a method in which the light beam reaches the corners of both ends of the light guide plate.

  Here, as a conventional light guide plate and flat illumination device, for example, the locus of light rays in a wedge-shaped light guide plate 21 will be described with reference to FIG. As the light guide plate, a wedge-shaped plate shown in FIG. 6 is used.

As shown in FIG. 6, the light guide plate 21 is configured such that the thickness decreases from the incident end surface portion 31 toward the counter incident end surface portion 41 located on the opposite side of the incident end surface portion 31. Thus, since the light guide plate 21 has a wedge shape, the light beam L01 travels to the surface portion 61 while the incident light L01 shown in FIG. 8 travels to the counter-incident end surface portion 41 located on the opposite side of the incident end surface portion 31. And if the incident angle of the light ray L01 with respect to the surface part 61 is within 42 degrees, the light ray L01 will be totally reflected by the surface part 61, and will advance to the back surface part 71 direction as the light ray L02. 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 the light beam L03 or the light beam L04. 71 breaks the critical angle and emits light.
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 similarly exists on the front surface portion 61.

  In this way, as shown in FIGS. 6 and 8, for the purpose of maximizing the light from the light source, the light guide plate is formed into a so-called wedge shape in which the thickness decreases as the distance from the incident end face portion increases. If the light source is directional, the critical angle is immediately broken in the vicinity of the incident end face, i.e., the taper leak increases. Luminance is emitted. In addition, since the emitted light beam has high luminance and strong directivity, 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 the semiconductor light emitting element (LED). There is a problem that will be.

  Further, in the light guide plate in which the thickness of the light guide plate is reduced as the distance from the incident end surface portion increases as described above, the incident end surface portion is avoided in order to avoid the shape of the semiconductor light emitting element itself being observed from the output surface. Use the neighborhood without actually using it. For this reason, there is a problem that a light guide plate larger than the required area of the flat illumination device must be used.

  In the case of a conventional large flat illumination device, as shown in FIG. 7, the thickness of the light guide plate 21A is reduced toward the center from the incident end face portions 31a and 31b at both ends, and the incident end face portions 31a and 31b are arranged. In a configuration in which both ends of the light guide plate 21A are made incident end surface portions 31a and 31b by using a method using a taper leak of light traveling in the opposite direction from the incident end surface portions 31a and 31b, the thickness of the central portion of the light guide plate 21A is There is a problem that the thickness becomes the thinnest part, and the thickness of the central part becomes thinner as the whole becomes lighter, and the mechanical strength is weak structurally.

  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 each RGB light source is arranged in an array, each emission color is incident on the end face. Since it is difficult to mix in the vicinity of the portion, there is a problem that the light emission color does not become white in the vicinity of the incident end surface portion, and the respective emission colors are emitted from the emission surface in the form of spots.

  In addition, a plain illuminating device using a point light source such as an LED as a conventional light source has a plurality of LEDs arranged on the incident end surface portion of the light guide plate, and a projection such as a prism on the incident end surface portion of the light guide plate at a position facing these LEDs. In the configuration in which the concave shape is provided, the light source is a point light source, so that the light beam intensity distribution is circular or elliptical. For this reason, the incident end surface portion of the light guide plate facing the light source is subjected to prism processing and dispersed in the left and right direction of the light source to be uniformly emitted from the entire light guide plate, but the light of adjacent light sources such as LEDs overlaps, There is a problem that unevenness in brightness occurs.

  Further, as shown in FIGS. 9A and 9B, in the conventional illumination 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 31, As shown in FIG. 9B, the light source 9 of the semiconductor light emitting element such as an LED has directivity, so that the light beam travels in the direction toward the non-incident end surface portion 41 in a narrow range and from the incident end surface portion 31 toward the anti-incident end surface portion 41. The critical angle is broken while going forward to exit. For this reason, there is a problem that both end portions of the incident end surface portion 31 (between the incident end surface portion 31 and the incident light beam L0) become dark portions.

  The present invention has been made in order to solve the above-described problems. The purpose of the present invention is to make the light rays existing in the light guide plate from the incident end surface portion to the opposite side of the incident end surface portion (the direction opposite to the incident surface surface or the opposite side). The incident end face part can be generated for the first time when it goes to the incident end face part again or to the opposite incident end face part. In the vicinity, do not emit high-intensity light from the light source, but once it is totally reflected on the opposite side of the incident end face of the light guide plate, and then emits it, while repeating the total reflection several times in the light guide plate in the meantime It is possible to eliminate reflections of light sources and brightness spots in order to proceed, and even in the case of a light source in which monochromatic light sources such as RGB are arranged, it does not immediately emit in the vicinity of the incident end surface, but once on the side opposite to the incident end surface of the light guide plate Full reflection and emission Therefore, in order to proceed while repeating total reflection several times in the light guide plate in the meantime, RGB single color light can be mixed to obtain complete white light, and brightness spots and emission color spots can be controlled along with luminance In addition, the light exiting surface of the light guide plate can be made larger, and even with a large light guide plate or flat illumination device, the incident end surface near the light source has the minimum thickness and the central portion has the maximum thickness, so it has excellent mechanical strength. It is providing the plane illuminating device which can obtain.

A flat illumination device according to claim 1 of the present invention includes a light source having directivity,
Nearly perpendicular to the incident end face part that guides light from the light source, the anti-incident end face part located on the opposite side of the incident end face part, the front surface part and / or the back surface part that emits the light, and the front surface part and the back surface part A wedge shape with a thin rectangular cube shape, and the surface surrounding them forms a mirror surface, and the distance between the front surface and the back surface is minimized at the incident end surface. The surface portion and / or the back surface portion has an inclined surface having a single slope from the incident end surface portion to the anti-incident end surface portion, and the surface portion Or / and / or the back surface is provided with a fine dot-shaped light deflecting element so that the quantity or area increases as it approaches the incident end face, and the light incident from the incident end face is critical when traveling away from the incident end face. Without breaking the corner, it is reflected at the anti-incident end face and reflected at the incident end face. A light guide plate for light is refracted emitted advanced to the inclined surface of the light deflector with defeating emits critical angle at that,
And a reflector having reflectivity that covers portions other than the incident end face and the exit face of the light guide plate.

The flat illumination device according to claim 1 is a light source having directivity,
Nearly perpendicular to the incident end face part that guides light from the light source, the anti-incident end face part located on the opposite side of the incident end face part, the front surface part and / or the back surface part that emits the light, and the front surface part and the back surface part A wedge shape with a thin rectangular cube shape, and the surface surrounding them forms a mirror surface, and the distance between the front surface and the back surface is minimized at the incident end surface. The surface portion and / or the back surface portion has an inclined surface having a single slope from the incident end surface portion to the anti-incident end surface portion, and the surface portion Or / and / or the back surface is provided with a fine dot-shaped light deflecting element so that the quantity or area increases as it approaches the incident end face, and the light incident from the incident end face is critical when traveling away from the incident end face. Without breaking the corner, it is reflected at the anti-incident end face and reflected at the incident end face. A light guide plate for light is refracted emitted advanced to the inclined surface of the light deflector with defeating emits critical angle at that,
Since it has a reflective body that covers the portions other than the incident end face and the exit face of the light guide plate, the light from the light source is taken into the light guide plate without distortion at the incident end face and is opposite to the incident end face. Even when the light guide plate has a wedge shape, there is no light beam that breaks the critical angle and taper leak does not occur even when the light guide plate is in a wedge shape. The shape of the light source such as incident light or the semiconductor light emitting element itself is not observed (reflected) or luminance unevenness from the exit surface, and many light rays are totally reflected at the anti-incident end surface portion on each surface of the light guide plate and the anti-incident end surface portion There are many rays that break the critical angle when approaching the incident end face again, or rays that are close to the critical angle, etc., and break the critical angle when reaching a fine light deflection element with a taper leak. Controls the amount of light emitted No reflection of the light source makes it Rukoto, 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.
In addition, since a taper leak can be caused only by a light beam totally reflected at the anti-incident end face part, even in the case of a light source in which monochromatic light sources such as RGB are arranged, light emitting color spots are not emitted immediately near the incident end face part. Since the incident light is totally reflected once on the opposite side of the incident end face portion of the light guide plate and then emitted, the light is propagated through the light guide plate while repeating the total reflection several times. The monochromatic light can be mixed to obtain complete white light, and the light exiting surface of the light guide plate can be made larger. Since it is the maximum thickness, the mechanical strength is increased structurally and mechanically superior.
Furthermore, since the quantity or area of the light deflecting elements increases as the light deflecting element is closer to the incident end face part, the light incident from the incident end face part does not reach the critical angle even if it reaches the front or back part of the light guide plate. It does not exist, and since the light that has been totally reflected once at the anti-incident end face on the opposite side of the incident end face has many rays that break the critical angle or are close to the critical angle, it returns from the anti-incident end face to the incident end face. Since it is necessary to increase the amount of light to be emitted as it approaches the incident end face part in order to emit from the exit surface, the quantity or area of the light deflection element increases as the distance from the incident end face part increases, thereby obtaining uniform outgoing light. be able to.

A planar illumination device according to claim 2 is a light source having directivity,
Two opposing incident end face parts that guide light from the light source, a front face part or / and a back face part that emits the light, and a side face part that intersects the front face part and the back face part at a substantially right angle and surrounds them The front surface and / or the back surface so that the distance between the front surface and the back surface is minimized at the incident end surface, and the distance between the two incident end surfaces is maximized. Have an inclined surface having a single inclination from the incident end surface portion to the central portion, and the light incident from the incident end surface portions does not break the critical angle when traveling to the central portion in the direction away from the incident end surface portion, The critical angle is broken when going to each incident end face after passing through, and the critical angle is broken when going back to the incident end face after being reflected by each incident end face and not going to break the central angle. An outgoing light guide plate;
And a reflector having reflectivity that covers portions other than the incident end face and the exit face of the light guide plate.

A flat illumination device according to claim 2 is a light source having directivity,
Two opposing incident end face parts that guide light from the light source, a front face part or / and a back face part that emits the light, and a side face part that intersects the front face part and the back face part at a substantially right angle and surrounds them The front surface and / or the back surface so that the distance between the front surface and the back surface is minimized at the incident end surface, and the distance between the two incident end surfaces is maximized. Have an inclined surface having a single inclination from the incident end surface portion to the central portion, and the light incident from the incident end surface portions does not break the critical angle when traveling to the central portion in the direction away from the incident end surface portion, The critical angle is broken when going to each incident end face after passing through, and the critical angle is broken when going back to the incident end face after being reflected by each incident end face and not going to break the central angle. An outgoing light guide plate;
Since it has a reflecting body that covers the portions other than the incident end face and the exit face of the light guide plate, the light from the light source is taken into the light guide plate without distortion at the incident end faces at both ends, and one incident end face Even if the light guide plate has a wedge shape, there is no light beam that breaks the critical angle, and no taper leak occurs, so even if the light source has strong directivity, The shape of the light source such as the emitted light and the semiconductor light emitting element itself is not observed (reflected) or luminance unevenness from the emitting surface, and many light rays are totally reflected on each surface of the light guide plate, and at the incident end surface portion on the opposite side When the totally reflected light beam travels again in the direction of the incident end face, there are many light beams that break the critical angle, light beams close to the critical angle, and the like, and bright and uniform outgoing light can be obtained. Further, since the thickness of the incident end face portions at both ends is the minimum and the center portion is the maximum thickness, the mechanical strength is increased structurally and mechanically excellent.

Further, a flat illumination device according to claim 3 is a light source having directivity,
Two opposing incident end face parts that guide light from the light source, a front face part or / and a back face part that emits the light, and a side face part that intersects the front face part and the back face part at a substantially right angle and surrounds them The front surface and / or the back surface so that the distance between the front surface and the back surface is minimized at the incident end surface, and the distance between the two incident end surfaces is maximized. Has an inclined surface with a single inclination from the incident end surface portion to the center portion, and the surface portion and / or the back surface portion has fine dot-shaped light so that the number or area increases as the incident end surface portion is approached. A deflecting element is provided, and the light incident from the incident end faces does not break the critical angle when traveling to the center in the direction away from the incident end faces, but breaks the critical angle when proceeding to the respective incident end faces past the center. When reflected at the incident end face of the light and proceeds to the center Without breaking the critical angle, only the central portion, a light guide plate light traveling on the inclined surface of the light deflector is refracted emitted with defeating emits critical angle when returning to the incident end face,
And a reflector having reflectivity that covers portions other than the incident end face and the exit face of the light guide plate.

The flat illumination device according to claim 3 is a light source having directivity,
Two opposing incident end face parts that guide light from the light source, a front face part or / and a back face part that emits the light, and a side face part that intersects the front face part and the back face part at a substantially right angle and surrounds them The front surface and / or the back surface so that the distance between the front surface and the back surface is minimized at the incident end surface, and the distance between the two incident end surfaces is maximized. Has an inclined surface with a single inclination from the incident end surface portion to the center portion, and the surface portion and / or the back surface portion has fine dot-shaped light so that the number or area increases as the incident end surface portion is approached. A deflecting element is provided, and the light incident from the incident end faces does not break the critical angle when traveling to the center in the direction away from the incident end faces, but breaks the critical angle when proceeding to the respective incident end faces past the center. When reflected at the incident end face of the light and proceeds to the center Without breaking the critical angle, only the central portion, a light guide plate light traveling on the inclined surface of the light deflector is refracted emitted with defeating emits critical angle when returning to the incident end face,
Since it has a reflecting body that covers the portions other than the incident end face and the exit face of the light guide plate, the light from the light source is taken into the light guide plate without distortion at the incident end faces at both ends, and one incident end face Even if the light guide plate has a wedge shape, there is no light beam that breaks the critical angle, and no taper leak occurs, so even if the light source has strong directivity, The shape of the light source such as the emitted light and the semiconductor light emitting element itself is not observed (reflected) or luminance unevenness from the emitting surface, and many light rays are totally reflected on each surface of the light guide plate, and at the incident end surface portion on the opposite side There are many rays that break the critical angle or light near the critical angle when the totally reflected light travels in the direction of the incident end face again, and breaks the critical angle along with the taper leak and exits from the light guide plate Control the amount of 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. Further, since the thickness of the incident end face portions at both ends is the minimum and the center portion is the maximum thickness, the mechanical strength is increased structurally and mechanically excellent.

Further, in the flat illumination device according to claim 4 , the light source is composed of a plurality of directional semiconductor light emitting elements, and is monochromatic light, trichromatic light of red light, green light, blue light, or white light using a wavelength conversion material. In addition, they are characterized by being configured as a single body or an array.

In the flat illumination device according to claim 4 , the light source is composed of a plurality of directional semiconductor light emitting elements, and is monochromatic light or red light, green light, blue light, three primary colors, or white light using a wavelength conversion material. Since these are configured as a single unit or an array, high-luminance outgoing light can be obtained, and high-luminance white light can be emitted according to the purpose. From the surface, it is possible to obtain outgoing light that is free from observation (reflection) and luminance spots.

Moreover, the flat illuminating device which concerns on Claim 5 is characterized by the reflective surface of a reflector being uneven | corrugated shape or a prism shape.

In the flat illumination device according to the fifth aspect, since the reflecting surface of the reflector has an uneven shape or a prism shape, the light beam or the exit surface that has traveled from the incident end surface portion to the anti-incident end surface portion located on the opposite side of the incident end surface portion The light emitted from the opposite side or 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 again by controlling the uneven shape and prism shape. 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.

As described above, the flat illumination device according to claim 1 includes a light source having directivity,
Nearly perpendicular to the incident end face part that guides light from the light source, the anti-incident end face part located on the opposite side of the incident end face part, the front surface part and / or the back surface part that emits the light, and the front surface part and the back surface part A wedge shape with a thin rectangular cube shape, and the surface surrounding them forms a mirror surface, and the distance between the front surface and the back surface is minimized at the incident end surface. The surface portion and / or the back surface portion has an inclined surface having a single slope from the incident end surface portion to the anti-incident end surface portion, and the surface portion Or / and / or the back surface is provided with a fine dot-shaped light deflecting element so that the quantity or area increases as it approaches the incident end face, and the light incident from the incident end face is critical when traveling away from the incident end face. Without breaking the corner, it is reflected at the anti-incident end face and reflected at the incident end face. A light guide plate for light is refracted emitted advanced to the inclined surface of the light deflector with defeating emits critical angle at that,
Since it has a reflective body that covers the portions other than the incident end face and the exit face of the light guide plate, the light from the light source is taken into the light guide plate without distortion at the incident end face and is opposite to the incident end face. Even when the light guide plate has a wedge shape, there is no light beam that breaks the critical angle and taper leak does not occur even when the light guide plate is in a wedge shape. The shape of the light source such as incident light or the semiconductor light emitting element itself is not observed (reflected) or luminance unevenness from the exit surface, and many light rays are totally reflected at the anti-incident end surface portion on each surface of the light guide plate and the anti-incident end surface portion There are many rays that break the critical angle when approaching the incident end face again, or rays that are close to the critical angle, etc., and break the critical angle when reaching a fine light deflection element with a taper leak. Controls the amount of light emitted No reflection of the light source makes it Rukoto, 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.
In addition, since a taper leak can be caused only by a light beam totally reflected at the anti-incident end face part, even in the case of a light source in which monochromatic light sources such as RGB are arranged, light emitting color spots are not emitted immediately near the incident end face part. Since the incident light is totally reflected once on the opposite side of the incident end face portion of the light guide plate and then emitted, the light is propagated through the light guide plate while repeating the total reflection several times. The monochromatic light can be mixed to obtain complete white light, and the light exiting surface of the light guide plate can be made larger. Since it is the maximum thickness, the mechanical strength is increased structurally and mechanically superior.
Furthermore, since the quantity or area of the light deflecting elements increases as the light deflecting element is closer to the incident end face part, the light incident from the incident end face part does not reach the critical angle even if it reaches the front or back part of the light guide plate. It does not exist, and since the light that has been totally reflected once at the anti-incident end face on the opposite side of the incident end face has many rays that break the critical angle or are close to the critical angle, the light returns from the anti-incident end face to the incident end face. Since it is necessary to increase the amount of light to be emitted as it approaches the incident end face part in order to emit from the exit surface, the quantity or area of the light deflection element increases as the distance from the incident end face part increases, thereby obtaining uniform outgoing light. be able to.

A flat illumination device according to claim 2 is a light source having directivity,
Two opposing incident end face parts that guide light from the light source, a front face part or / and a back face part that emits the light, and a side face part that intersects the front face part and the back face part at a substantially right angle and surrounds them The front surface and / or the back surface so that the distance between the front surface and the back surface is minimized at the incident end surface, and the distance between the two incident end surfaces is maximized. Have an inclined surface having a single inclination from the incident end surface portion to the central portion, and the light incident from the incident end surface portions does not break the critical angle when traveling to the central portion in the direction away from the incident end surface portion, The critical angle is broken when going to each incident end face after passing through, and the critical angle is broken when going back to the incident end face after being reflected by each incident end face and not going to break the central angle. An outgoing light guide plate;
Since it has a reflecting body that covers the portions other than the incident end face and the exit face of the light guide plate, the light from the light source is taken into the light guide plate without distortion at the incident end faces at both ends, and one incident end face Even if the light guide plate has a wedge shape, there is no light beam that breaks the critical angle, and no taper leak occurs, so even if the light source has strong directivity, The shape of the light source such as the emitted light and the semiconductor light emitting element itself is not observed (reflected) or luminance unevenness from the emitting surface, and many light rays are totally reflected on each surface of the light guide plate, and at the incident end surface portion on the opposite side When the totally reflected light beam travels again in the direction of the incident end face, there are many light beams that break the critical angle, light beams close to the critical angle, and the like, and bright and uniform outgoing light can be obtained. Further, since the thickness of the incident end face portions at both ends is the minimum and the center portion is the maximum thickness, the mechanical strength is increased structurally and mechanically excellent.

The flat illumination device according to claim 3 is a light source having directivity,
Two opposing incident end face parts that guide light from the light source, a front face part or / and a back face part that emits the light, and a side face part that intersects the front face part and the back face part at a substantially right angle and surrounds them The front surface and / or the back surface so that the distance between the front surface and the back surface is minimized at the incident end surface, and the distance between the two incident end surfaces is maximized. Has an inclined surface with a single inclination from the incident end surface portion to the center portion, and the surface portion and / or the back surface portion has fine dot-shaped light so that the number or area increases as the incident end surface portion is approached. A deflecting element is provided, and the light incident from the incident end faces does not break the critical angle when traveling to the center in the direction away from the incident end faces, but breaks the critical angle when proceeding to the respective incident end faces past the center. When reflected at the incident end face of the light and proceeds to the center Without breaking the critical angle, only the central portion, a light guide plate light traveling on the inclined surface of the light deflector is refracted emitted with defeating emits critical angle when returning to the incident end face,
Since it has a reflecting body that covers the portions other than the incident end face and the exit face of the light guide plate, the light from the light source is taken into the light guide plate without distortion at the incident end faces at both ends, and one incident end face Even if the light guide plate has a wedge shape, there is no light beam that breaks the critical angle, and no taper leak occurs, so even if the light source has strong directivity, The shape of the light source such as the emitted light and the semiconductor light emitting element itself is not observed (reflected) or luminance unevenness from the emitting surface, and many light rays are totally reflected on each surface of the light guide plate, and at the incident end surface portion on the opposite side There are many rays that break the critical angle or light near the critical angle when the totally reflected light travels in the direction of the incident end face again, and breaks the critical angle along with the taper leak and exits from the light guide plate Control the amount of 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. Further, since the thickness of the incident end face portions at both ends is the minimum and the center portion is the maximum thickness, the mechanical strength is increased structurally and mechanically excellent.

In the flat illumination device according to claim 4 , the light source is composed of a plurality of directional semiconductor light emitting elements, and is monochromatic light or red light, green light, blue light, three primary colors, or white light using a wavelength conversion material. Since these are configured as a single body or an array, high-luminance outgoing light can be obtained and high-luminance white light can be emitted according to the purpose. In addition, by forming the light source in an array shape, the light source can be observed (reflected) from the light exit surface, and output light with no brightness spots can be obtained, and high-intensity white light can be emitted depending on the purpose. Therefore, clear white light or monochromatic light can be obtained.

In the flat illumination device according to the fifth aspect, since the reflecting surface of the reflector has an uneven shape or a prism shape, the light beam or the exit surface that has traveled from the incident end surface portion to the anti-incident end surface portion located on the opposite side of the incident end surface portion It is possible to control the position where the light beam emitted to the opposite surface or the leaked light beam is returned to the light guide plate more reliably. Thereby, the brightness | luminance of the last emission light, light quantity distribution, an emission angle, etc. can be adjusted. Furthermore, when the light source is RGB or other primary color light, the light of the three primary colors can be mixed in the light guide plate by reflection from the prism surface, so light from the light source is converted to light emitted from the light source plate without wasting it. The efficiency to do is excellent.

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 rectangular cubic body shape, and the six surfaces surrounding the light guide plate form a mirror surface, and a fine light deflection element approaches the incident end surface portion on the front surface portion and / or the back surface portion. 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 separation distance from the incident end surface portion. The light source is composed of a plurality of directional semiconductor light emitting elements, and is either monochromatic light, red light, green light, blue light, or white light using a wavelength conversion material. It consists of a single semiconductor light emitting element having an array or directivity. In addition, the light source near the incident end surface portion of the light guide plate is provided with a reflector that covers the portions other than the incident end surface portion and the output surface of the light guide plate, and the reflective surface has an uneven shape or a prism shape. It is possible to provide a light guide plate and a flat illumination device that can control the reflection of light, the occurrence of luminance spots and emission color spots, and can take a large use exit surface of the light guide plate.

  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, and FIG. 3 shows a locus of light rays in the light guide plate of FIG. 4 (a) and 4 (b) are diagrams showing the trajectory of a light beam 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 is a diagram of the light guide plate according to the present invention. It is a side view which shows another shape.

  As shown in FIG. 1, the flat illumination device 1 includes a light guide plate 2, a light source 9, and a reflector 10.

  The light guide plate 2 is formed of a transparent acrylic resin (PMMA) or polycarbonate (PC) having a refractive index of about 1.4 to 1.7. The light guide plate 2 includes an incident end face 3 that guides light from the light source 9, a counter incident end face 4 that is located on the opposite side of the incident end face 3, and both ends of the incident end face 3 and the counter incident end face 4. Side surface portions 5 and 5 connected to each other, a front surface portion 6 for emitting light, and a back surface portion 7 located on the opposite side of the front surface portion 6. The front surface portion 6 and the back surface portion 7 are provided with a light deflection element 8 that totally reflects or refracts light.

In the light guide plate 2, the distance between the front surface portion 6 and the back surface portion 7 (thickness of the light guide plate 2) is minimum (thin) at the incident end surface portion 3, and the maximum separation distance (incident end surface portion) from the incident end surface portion 3. The distance (thickness) is maximized (thick) in the distance from 3 to the counter-incident end face portion 4 located on the opposite side of the incident end face portion 3.
Therefore, as shown in FIG. 2, the light guide plate 2 includes a light source 9 disposed substantially parallel to the incident end surface portion 3 in the vicinity of the thin incident end surface portion 3, and the incident end surface portion where the light source 9 is disposed. 3 is an arrangement in which the thickness of the anti-incident end face portion 4 on the opposite side (maximum separation distance) of 3 is thick.

  Further, a light deflection element 8 is provided on the front surface portion 6 and the back surface portion 7. In the example of FIG. 1, the light deflection element 8 is provided only on the surface portion 6. As a result, while the incident light from the incident end face portion 3 travels to the anti-incident end face portion 4 located on the opposite side of the incident end face portion 3, even if the light guide plate 2 has a wedge shape, there is no ray breaking the critical angle. Total reflection is performed at the anti-incident end face portion 4. Then, the light beam totally reflected by the counter-incident end face portion 4 can be refracted by the light deflecting element 8 when traveling again in the direction of the incident end face portion 3, and can be emitted from the surface portion 6 by breaking the critical angle.

As shown in FIG. 3, the light incident on the light guide plate 2 travels into the light guide plate 2 within a range where the refraction angle γ satisfies the expression 0 ≦ | γ | ≦ sin ⁻¹ (1 / n). For example, the refractive index of acrylic resin, which is a resin material used for the general light guide plate 2, is about n = 1.49. Therefore, the maximum incident angle is 90 ° for the light from the front surface portion 6 direction to the back surface portion 7 direction and the light from the back surface portion 7 direction to the front surface portion 6 direction. For this reason, the refraction angle γ refracted at the incident end face portion 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.

  Here, the light that has entered the light guide plate 2 within the range of the refraction angle γ = 0 to ± 42 ° is expressed as sin α = (1 / in the boundary surface between the light guide plate 2 and the air layer (refractive index n = 1). The critical angle can be expressed by the equation n). For example, since the refractive index of 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 the front surface portion 6 and the back surface portion 7 of the light guide plate 2 are not convex or concave to deflect the light beam or do not exceed the critical angle α, all the light in the light guide plate 2 is transmitted through the front surface portion 6 and the back surface portion 7. The light travels in the direction of the anti-incident end face 4 while being totally reflected.

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 of the incident end surface portion 3 from the incident end surface portion 3. Since the thickness of the light guide plate 2 becomes thinner (minimum) toward the counter-incident end face portion 4 (maximum separation distance from the incident end face portion 3), the wedge shape (generally or opposite to the conventional one) is shown in FIG. As shown, there is no light beam that breaks the critical angle even if the light guide plate 2 has a wedge shape while the incident light Ln1 from the incident end surface portion 3 travels to the counter incident end surface portion 4 located on the opposite side of the incident end surface portion 3. The light beam Ln2 that has undergone total reflection at the front surface portion 6 and the back surface portion 7 is totally reflected at the anti-incident end surface portion 4. Then, when the light beam Ln3 again travels in the direction of the incident end face portion 3, the light deflecting element 8 can perform refraction and the like to break the critical angle and emit the light beam Ln4 from the surface portion 6.
Here, although the convex shape and the concave shape are described for the light deflecting element 8, the light is refracted and emitted to the outside by the convex or concave inclined surface.

  Furthermore, although not shown, the light guide plate 2 of the present invention is provided on the front surface portion 6 and the back surface portion 7 so that the quantity or area of the light deflection elements 8 increases as the light deflection element 8 approaches the incident end surface portion 3. As a result, the light initially incident from the incident end surface portion 3 from the light source 9 does not have the light reaching the critical angle α even when reaching the front surface portion 6 or the rear surface portion 7 of the light guide plate 2. While repeating total reflection at the portion 7, the light advances to the anti-incident end surface portion 4 on the opposite side of the incident end surface portion 3 and is totally reflected at the anti-incident end surface portion 4. In the process in which the totally reflected light returns in the direction of the incident end face 3, there are many light rays that break the critical angle α, light rays that are close to the critical angle α, and the like. For this reason, of the light that has traveled again in the direction of the incident end face portion 3 due to the total reflection, a light beam in the vicinity of the critical angle α is refracted by the inclined surface of the light deflection element 8 while returning from the counter incident end face portion 4 to the incident end face portion 3. Etc. are emitted and emitted from the emission surface (surface portion 6).

  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 approaches the incident end surface portion 3 (the more it returns), the more the light amount is attenuated. Are emitted from the emission surface (surface portion 6). For this reason, it is necessary to increase the amount of light to be emitted as it approaches the incident end surface portion 3, and as the number or area of the light deflection elements 8 increases as it approaches the incident end surface portion 3, uniform emitted light can be obtained.

  Further, even when the light source 9 is single, the light that has been totally reflected by the anti-incident end surface portion 4 on the opposite side of the incident end surface portion 3 proceeds to the entire incident end surface portion 3, and the light is deflected as it proceeds in the direction of the incident end surface portion 3. The quantity or area of the light deflection element 8 increases as the element 8 approaches the incident end face 3. Thereby, uniform emitted light can be obtained also at both end portions of the incident end surface portion 3 which are both ends of the light source 9.

  Further, in the case of the flat illumination device 1 having a large screen size, the light guide plate 2 has a structure in which the both ends of the light guide plate 2 are provided with the incident end face portions 3. The distance (thickness of the light guide plate 2) is minimum (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. .

  That is, as shown in FIG. 5, the flat illumination device 1 includes two light sources 9a and 9b as the light sources 9, and the light guide plates 2 facing the two light sources 9a and 9b have the thinnest ends. This is the incident end face 3 (3a, 3b). The thickness of the light guide plate 2 increases as the distance from the incident end surface portions 3a and 3b increases toward the center, and the distance between the front surface portion 6 and the rear surface portion 7 (7a and 7b) toward the center in the center is maximum. become.

  Therefore, in the light guide plate 2, 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 incident from each incident end surface portion 3a and the incident end surface portion 3b. The shape is such 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 incident end face part 3a and incident end face part 3b). Thereby, even if the light guide plate 2 is tapered while the incident light from each incident end face part 3a and the incident end face part 3b proceeds to the center, there is no light beam that breaks the critical angle to the center. The light beams that have undergone total reflection at the front surface portion 6 and the back surface portion 7 are totally reflected in the light guide plate 2 facing each other and the incident end surface portion 3a and the incident end surface portion 3b facing each other, and are incident on each other again. When the light beam travels in the direction of the incident end surface portion 3a and the incident end surface portion 3b, the light deflection element 8 can refract the light to break the critical angle and emit the light beam from the surface portion 6.

  Also, as shown in FIGS. 4A and 4B, when only one light source 9 made of a semiconductor light emitting element (LED or the like) is provided at the center of the incident end face 3, the light source 9 emits semiconductor light. The light beam travels in the direction of the anti-incident end face portion 4 in a narrow range because of an element or the like, but there is no light beam that breaks the critical angle while traveling from the incident end face portion 3 to the anti-incident end face portion 4 direction. The critical angle is broken while the light beam Ln again travels in the direction of the incident end face portion 3 after being totally reflected by the light beam, and the light deflecting element 8 provided on the surface portion 6 causes the light beam near the critical angle to be reflected by the inclined surface of the light deflecting element 8. Since refraction or the like is caused and a larger number of light beams can be emitted to the surface portion 6, dark portions cannot be formed at both end portions of the incident end surface portion 3, and uniform and bright emitted light can be obtained. 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 surface portion.

  Thus, 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 surface portion 3 and the thickness of the light guide plate 2 increases as the distance from the incident end surface portion 3 increases. The light beam first incident on the light guide plate 2 from the light source 9 is totally reflected 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 guide plate 2 again proceeds in the direction of the incident end face 3, and at this time, the thickness of the light guide plate 2 is gradually reduced. The element 8 causes the light beam near the critical angle to be refracted by the inclined surface of the light deflecting element 8 and emits a larger number of light beams to the surface portion 6.

  In addition, when the incident end surface portions 3 are provided at both ends of the light guide plate 2, the thickness of the light guide plate 2 is such that the position of the incident end surface portion 3 is the thinnest and the distance from the incident end surface portion 3 is greater. And the light guide plate 2 is configured so that the thickness of the light guide plate 2 is the thickest at the central portion at the same distance from both ends of the light guide plate 2. Since only the total reflection occurs at the mirror surface such as the back surface portion 7 and the thickness of the light guide plate 2 gradually decreases from the position beyond the center portion, the critical angle is broken while the light source advances, and the light is emitted from the surface portion 6 and the surface portion. The light deflecting element 8 provided at 6 causes a light beam near the critical angle to be refracted by the inclined surface of the light deflecting element 8 to emit a larger number of light beams to the surface portion 6. Therefore, in the vicinity of the incident end face portion 3, light with no bright spots is emitted on the entire light guide plate 2 without emitting (reflecting) direct high-intensity light from the light source 9. In the case where the incident end face portion 3 is provided, the mechanical strength is excellent.

The light source 9 is a semiconductor light emitting element, and is composed of an LED, a laser, or the like, and each RGB (red, green, blue) monochromatic light is provided in the vicinity of each incident portion 3 or RGB (red light emission, green light emission, blue color). A unit configured in an array shape in which a plurality of semiconductor light emitting elements composed of light emission) is combined may be provided in each incident portion 3.
Furthermore, the light source 9 may be a light source that emits white light using a wavelength conversion material (for example, a blue light emitting element combined with a yellow fluorescent agent).

The light source 9 may be a CCFL (cold cathode tube) when the incident end face portion 3 is large or 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 surface portion 3 of the light guide plate 2, and other light is reflected by a reflector (not shown), and the space between the light source 9 and the reflector. Then, the light enters the light guide plate 2.
In the case of this linear light source 9, in the conventional light guide plate 21, high-brightness bright lines appear in the vicinity of the incident end face portion 31, but bright lines are generated by using the light guide plate 2 of the present invention. Can be prevented.

Although not shown, the reflector 10 has a reflective surface with an uneven shape or a prism shape, and metal such as aluminum is deposited on a sheet of thermoplastic resin mixed with a white material such as titanium oxide or a sheet of thermoplastic resin. Or made of metal foil laminated or sheet metal. The reflector 10 covers a portion other than the incident end face portion 3 and the surface portion 6, reflects or irregularly reflects light other than light emitted from the light source 9 to the surface portion 6 by the light guide plate 2, and is reflected on the light guide plate 2 again. Incident light is emitted so that all the light from the light source 9 is emitted from the surface portion 6.
In addition, by controlling the uneven shape and prism shape of the reflector 10 used for the anti-incident end face part 4 and the back face part 7, the position to be returned to the light guide plate 2 is controlled again, and the final emitted light brightness, light quantity distribution and The emission angle and the like can be adjusted.

  Further, the reflector 10 can have a reflective surface with an uneven shape or a prism shape. As a result, 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 the light from the light source 9 is converted from the light source 9 to the light emitted from the light guide plate 2 without wasting it. Efficiency can be improved.

Although not shown here, for example, when the directivity of the light source 9 such as CCFL (cold cathode tube) indicates a radial direction, a reflector is provided around the light source 9 (CCFL), and the light guide plate 2 The incident end face 3 and the light source 9 are surrounded. As a result, the light from the light source 9 is reflected, and the reflected light is incident again on the incident end face 3 of the light guide plate 2.
Further, the reflector is made of a sheet-like material or a metal on which a white insulating material or a metal such as aluminum is deposited.

Further, although not shown here, as a realistic flat illumination device 1, a light beam that breaks the critical angle from the light guide plate 2 and exits to the surface portion 6 or the like has a large incident angle with respect to the surface portion 6, and therefore has a large exit angle. Become. This means that the angle formed by the surface portion 6 and the emitted light is reduced, and the emitted light is along the light guide plate 2. Therefore, for example, for a liquid crystal display device or the like, since the emitted light substantially perpendicular to the light guide plate 2 is required, a prism sheet is used for the emission surface (surface portion 6) of the light guide plate 2.
At this time, the prism surface (prism ridge) of the prism sheet is arranged facing the light guide plate 2, and the emitted light along the light guide plate 2 is once taken into the prism sheet, and on the surface opposite to the captured surface. Total reflection is performed, and finally, substantially vertical outgoing light is obtained from the flat illumination device 1.

  FIG. 10A is a diagram showing the results of measurement using the light guide plate of the present invention and the conventional light guide plate, and FIG. 10B shows how to divide the region of the light guide plate when measuring the average luminance. FIG.

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 0.9 mm-thick portion is used as an incident end surface portion, and a light source is disposed in the vicinity of the incident end surface portion. On the other hand, in the conventional light guide plate, a 1.3 mm thick portion is used as an incident end face portion, and a light source is disposed in the vicinity of the incident end face portion. In addition, the same size is used for the present invention and the conventional light guide plate. The light source used was a product in which four semiconductor light emitting elements (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 were manufactured by Sumitomo 3M Co., Ltd. The luminance measuring instrument is Topcon BM-7 (viewing angle 1 °), and the unit of numerical values is Cd / m ² .

As is apparent from the measurement results shown in FIG. 10A, regarding the average luminance, the average luminance and the central luminance of all the three regions of the light guide plate are better when the light guide plate of the present invention is used. The result that it was higher than the case where the conventional light-guide plate was used was obtained. Further, with respect to the luminance unevenness, the result that the light guide plate of the present invention is less than the case of using the conventional light guide plate (substantially half the number) was obtained.
As shown in FIG. 10B, the average luminance was measured by dividing the area A, B, and C into three equal parts from the incident end face where the light source is disposed opposite to the counter incident end face. .

  Thus, in the light guide plate and the flat illumination device of the present invention, the thickness of the light guide plate 2 is such that the position of the incident end face portion 3 is the thinnest, and the distance from the incident end face portion 3 increases. It has become a structure. As a result, when traveling in the direction from the incident end surface portion 3 to the anti-incident end surface portion 4 located on the opposite side of the incident end surface portion 3 (this direction is referred to as the 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 and undergoes total reflection at the anti-incident end face portion 4, and then proceeds again in the direction of the incident end face portion 3 (this direction is referred to as a reverse direction). When traveling in the opposite direction, the thickness of the light guide plate 2 is gradually reduced, so that the critical angle α is broken while the light travels and is emitted from the surface portion 6. In addition, the light deflection element 8 provided so that the amount of distribution increases as it approaches the incident end face portion 3 of the surface portion 6 causes the light rays near the critical angle α to be refracted by the inclined surface of the light deflection element 8, thereby increasing the number of light rays. Can be emitted to the surface portion 6 and uniform and high-luminance outgoing light can be obtained.

  Similarly, when the incident end face portions 3 a and 3 b 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 face portions 3 a and 3 b, and the light guide plate 2 is at the center of the light guide plate 2. The thickness of 2 is the largest. As a result, in the forward direction from the two incident end face portions 3a and 3b toward the central portion of the light guide plate 2, only total reflection is performed on the mirror surface of each surface, and the reverse direction from the position beyond the central portion toward the opposite incident end face portion. Since the thickness of the light guide plate 2 gradually decreases as the light travels toward the surface, the light breaks off the critical angle α as it travels and exits from the surface portion 6. In addition, the light deflection element 8 provided such that the amount of distribution increases as it approaches the incident end face portions 3a and 3b of the surface portion 6, and the light near the critical angle α is refracted by the inclined surface of the light deflection element 8 and more. Can be emitted to the surface portion 6 and uniform and high-luminance outgoing light can be obtained.

  Therefore, in the vicinity of the incident end face portion 3, light having high brightness and no spots is emitted on the entire light guide plate 2 without emitting so-called direct high-luminance light from the light source 9. In particular, when the incident end surface 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 secured as much as there is no reflection. Further, even when a white light source of three primary colors (RGB) is used as the light source 9, since it does not exit near the incident end face part 3, each color (RGB) light beam is mixed while traveling in the opposite direction to the incident end face part. When the angle α is broken, it can be emitted as complete white light.

  Further, when only one directional light source 9 is provided at the center of the incident end face portion 3 like a semiconductor light emitting element, the light beam proceeds in the direction toward the anti-incident end face portion 4 in a narrow range. For this reason, in the conventional configuration, both end portions of the incident end surface portion 3 of the light guide plate 2 become dark portions. On the other hand, in the configuration of the present invention, there is no light beam that breaks the critical angle α while traveling from the incident end surface portion 3 toward the anti-incident end surface portion 4, and the light beam Ln is totally reflected by the anti-incident end surface portion 4. Breaks the critical angle while the light beam travels again in the direction of the incident end face portion 3, and the light deflecting element 8 provided on 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. Can be emitted to the surface portion 6. Thereby, a dark part cannot be formed in the both ends of the incident end surface part 3, and uniform and bright emitted light can be obtained.

It is a disassembled perspective view which shows schematic structure of the plain illuminating device containing the light-guide plate which concerns on this invention. It is a side view of the light-guide plate which concerns on this invention. It is a figure which shows the locus | trajectory of the light ray in the light-guide plate of FIG. (A), (b) It is a figure which shows the locus | trajectory of a light ray when one light source is arrange | positioned in the center part of the incident-end surface part in the light-guide plate of FIG. It is a side view which shows the other shape of the light-guide plate which concerns on this invention. It is a perspective view of the conventional light-guide plate. It is a side view which shows schematic structure of the planar illuminating device containing the light-guide plate by the other conventional shape. It is a figure which shows the locus | trajectory of the light beam in the light-guide plate of FIG. (A), (b) It is a figure which shows the locus | trajectory of a light ray when one light source is arrange | positioned in the center part of the incident-end surface part in the light-guide plate of FIG. (A) It is a figure which shows the result of the measured value using the light-guide plate of this invention, and the conventional light-guide plate. (B) It is a figure which shows how to divide the area | region of a light-guide plate when measuring an average brightness | luminance.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Planar illuminating device 2,21,21A Light-guide plate 6,61 Front surface part 7,71 Back surface part 3,31 Incident end surface part 4,41 Anti-incident end surface part 5,51 Side surface part 8 Optical deflection element 9, 9a, 9b91a, 91b Light source 10 Reflector Ln, Ln1, Ln2, Ln3. Ln4, L0, L01, L02, L03, L04 rays

Claims (5)

A directional light source;
An incident end face part that guides light from the light source, a counter incident end face part located on the opposite side of the incident end face part, a front surface part and / or a back surface part that emits the light, and the front surface part and the back surface part And a wedge shape in the shape of a thin plate-like rectangular cube, and the surface surrounding them forms a mirror surface, and the distance between the front surface portion and the back surface portion is the incident end surface. And the distance between the front surface portion and the back surface portion is maximum at the anti-incident end surface portion, and the front surface portion and / or the back surface portion is simply from the incident end surface portion to the anti-incident end surface portion. An inclined surface having a single inclination, and a fine dot-shaped light deflecting element is provided on the front surface portion and / or the back surface portion so as to increase in quantity or area as it approaches the incident end surface portion, The light incident from the incident end surface is the incident end. When traveling in a direction away from the part, the critical angle is not broken, and the light that is reflected by the anti-incident end face part and breaks out of the critical angle when returning to the incident end face part and travels to the inclined surface part of the light deflection element is refracted. A light guide plate that emits light,
A flat illumination device comprising: a reflector having reflectivity that covers a portion other than the incident end surface portion and the emission surface of the light guide plate. A directional light source;
Two opposing incident end face parts that guide light from the light source, a front surface part or / and a back surface part that emits the light, and a side surface part that intersects the front surface part and the back surface part at a substantially right angle; The surface surrounding them forms a mirror surface so that the distance between the front surface portion and the back surface portion is minimized at the incident end surface portion, and the distance is maximized at the central portion between the two incident end surface portions. The front surface portion and / or the back surface portion has an inclined surface having a single inclination from the incident end surface portion to the central portion, and light incident from the incident end surface portion is separated from the incident end surface portion. The critical angle is not broken when traveling to the central portion, the critical angle is broken when proceeding to the incident end surface portion through the central portion, and the critical angle is reflected at the incident end surface portion and proceeds to the central portion. Without passing through the central portion, A light guide plate for emitting defeating critical angle when returning to hurt surface,
A flat illumination device comprising: a reflector having reflectivity that covers a portion other than the incident end surface portion and the emission surface of the light guide plate. A directional light source;
Two opposing incident end face parts that guide light from the light source, a front surface part or / and a back surface part that emits the light, and a side surface part that intersects the front surface part and the back surface part at a substantially right angle; The surface surrounding them forms a mirror surface so that the distance between the front surface portion and the back surface portion is minimized at the incident end surface portion, and the distance is maximized at the central portion between the two incident end surface portions. The front surface portion and / or the back surface portion has an inclined surface having a single inclination from the incident end surface portion to the central portion, and the front surface portion and / or the back surface portion approaches the incident end surface portion. Provided with a fine dot-shaped light deflecting element so that the quantity or area increases so that the light incident from the incident end face part does not break the critical angle when traveling to the central part in the direction away from the incident end face part, Past each other in front of each other Breaks the critical angle when proceeding to the incident end face, and breaks the critical angle when returning to the incident end face after passing through the central section without breaking the critical angle when reflected to each other at the incident end face. A light guide plate that emits and refracts and emits the light that has traveled to the inclined surface portion of the light deflection element; and
A flat illumination device comprising: a reflector having reflectivity that covers a portion other than the incident end surface portion and the emission surface of the light guide plate. The light source is composed of a plurality of directional semiconductor light emitting elements, and is composed of monochromatic light, red light, green light, blue light, primary light or white light using a wavelength conversion material, and is configured as a single light or an array. The flat illumination device according to any one of claims 1 to 3 . The planar illumination device according to any one of claims 1 to 3 , wherein the reflector has an uneven shape or a prism shape.

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