JP2010123295A - Lighting unit and lighting device using this unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lighting unit capable of efficiently emitting incident light from an emission surface. <P>SOLUTION: Reflecting plates 11, 12, 10, 14, 15 are installed on a light guide plate 20 which has an incident part 20a from which visible light from a light source 13 enters and the emission surface 20b from which the visible light entered from the incident part is propagated inside and emitted. A large number of fine reflecting parts 20e of concave shape are arranged point-like on the opposite side face 20d to the emission surface 20b of the light guide plate. With this structure, light entered from the light source into the light guide plate is guided efficiently to the emission surface by being reflected, refracted, or scattered by the reflecting parts. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an illumination unit including a light guide plate that propagates and emits visible light incident from an incident portion, and an illumination device using the illumination unit.

  Conventional light guide plates are configured to take light from a light source disposed on a light incident surface of the light guide plate into the light guide plate and emit light perpendicular to the light incident surface, and as a surface light source device for a liquid crystal display screen Widely used. In such a surface light source device for a liquid crystal display screen, a method has been proposed in which a plurality of light sources are used to increase the amount of light incident on the light guide plate in order to obtain high luminance (see Patent Document 1 below).

  Further, when a light guide plate is used, it is said that a light guide plate that is thin in the emission direction has higher emission efficiency than a light guide plate that is thick in the emission direction. This is because the number of reflections of light in the light guide plate increases and the probability of reflection and diffusion in the reflection part (diffusion pattern) increases when a plurality of thin light guide plates are stacked and arranged rather than one thick light guide plate. This is because light is efficiently emitted from the light emission surface.

On the other hand, the LED as the light source cannot be said to have good light conversion efficiency. In order to efficiently dissipate the heat generated from the LED in the high-brightness LED, the LED light emitting part is often made large and thick as necessary. In some cases, a light guide plate must be used.
JP-A-11-101665

  Each light guide plate constituting the illumination unit is provided with a reflection portion (diffusion pattern) in order to efficiently emit light incident on the light guide plate. This reflecting portion (diffusion pattern) is generally printed in white and is provided on the surface opposite to the exit surface of each light guide plate. Therefore, in the light guide plate closest to the exit surface of the laminated light guide plates, light can be efficiently emitted to the exit surface, but in other light guide plates, the light emitted in the exit direction is close to the exit surface of the light guide plate. It is shielded by the reflection part (diffusion pattern) of another light guide plate, and cannot be efficiently emitted to the emission surface.

  Accordingly, the present invention has been made to solve such problems, and it is an object of the present invention to provide an illumination unit capable of efficiently emitting incident light to the exit surface and an illumination device using the illumination unit.

The present invention
A light guide plate comprising: an incident part for entering light from a light source; and an exit surface for propagating and emitting the light incident from the incident part.
A reflector for reflecting visible light emitted from other than the exit surface of the light guide plate, and an illumination unit comprising:
The light guide plate is disposed on at least one of the exit surface and the surface opposite to the exit surface, or both so as to be dotted with a plurality of fine-shaped reflective portions formed in a convex shape or a concave shape. It is characterized by that.

  In addition, the present invention is characterized by an illumination device including the illumination unit and a light source.

  In the present invention, a plurality of fine-shaped reflecting portions formed in a convex shape or a concave shape are dotted on at least one of or both of the exit surface of the light guide plate and the surface opposite to the exit surface. Since the light is incident on the light guide plate from the light source, the light is reflected, refracted or scattered by the reflecting portion and efficiently guided to the exit surface, and the brightness of the light emitted from the exit surface can be increased.

  When multiple light guide plates are provided and each light guide plate is stacked so that its exit surface overlaps the surface opposite to the exit surface of the light guide plate above it, the number of times the light from the light source is reflected within the light guide plate The probability that the light is reflected and diffused by the reflecting portion (diffusion pattern) increases, and light is efficiently emitted from the light exit surface.

  If the reflective portions of the light guide plate are arranged so that the number per unit area gradually increases as the distance from the incident portion of the light guide plate increases, the luminance of the entire light exit surface of the light guide plate can be made substantially uniform.

  Hereinafter, the present invention will be described based on embodiments shown in the drawings.

  FIG. 1 shows an embodiment of a lighting unit 1 according to the present invention. The illumination unit 1 includes a light guide plate 20 that includes an incident portion 20 a that makes visible light from the light source 13 incident thereon, an emission surface 20 b that propagates and emits visible light incident from the incident portion, and a light source 13. The light guide plate 21 is provided with an incident portion 21a for allowing the visible light to enter, and an emission surface 21b for propagating the visible light incident from the incident portion and emitting the visible light toward the light guide plate 20. The light source 13 is composed of, for example, a light emitting diode that emits visible light with high luminance and strong directivity.

  The illumination unit 1 includes a reflector for reflecting visible light emitted from other than the exit surface 20b of the light guide plate 20 having the exit surface of the illumination unit (that is, the uppermost layer). The reflector includes a rear reflector 11 disposed opposite to a surface 21d opposite to the exit surface 21b of the light guide plate 21 that is stacked farthest from the exit surface of the illumination unit (that is, the lowermost layer), and the incident surface. The end surface reflecting plate disposed opposite to the end surface other than the portion, that is, the end surface reflecting plate 12 disposed opposite to the end surface 20c other than the end surface where the light source 13 is disposed intersects with the end surface where the light source 13 is disposed. Side reflectors arranged to face the side surfaces on both sides (they appear on the front and back of the paper surface of FIG. 1 and cannot be shown in FIG. 1, but are shown by reference numerals 14 and 15 in FIGS. 7A and 13). Plate) and the incident portion reflecting plate 10 disposed on the light source 13 side so as not to prevent light incidence from the light source. As the reflector, any one of the back reflector 11, the end reflector 12, the incident reflector 10, and the side reflectors (14, 15), any two, any three, or any These four may be used.

  The light guide plates 20 and 21 are made of a highly light-transmitting material, for example, a transparent acrylic resin. On the surfaces 20d and 21d on the opposite side of the emission surfaces 20b and 21b, the concave fine-shaped reflecting portions 20e and A plurality of 21e are arranged.

FIG. 3 shows the reflecting portion in detail, and the light guide plate 20 in which the fine reflecting portions 20e are arranged in a grid pattern is formed by injection molding using a mold. In the reflection part 20e, the thickness of the light guide plate 20 is 1 mm (dot density is about 15000 pieces / cm ² ), and as shown in an enlarged view in FIG. 3, the larger diameter d1 is about 55 μm, and the smaller diameter is It is formed in a truncated cone shape with d2 of about 10 μm and height d3 of about 30 μm. In FIG. 3, as can be seen from the shape of the reflecting portion 20e, it is shown upside down from FIG. 1, and the lower side is the emission surface 20b. FIG. 3 is shown for ease of understanding and does not match the actual scale.

  Such reflection portions 20e and 21e may be arranged uniformly on the end surfaces 20d and 21d of the light guide plates 20 and 21, but as shown in FIG. 1, the unit increases as the distance from the incidence portions 20a and 21a of the light guide plate increases. It arrange | positions so that the number per area may increase gradually.

  In the example of FIG. 1, two light guide plates 20 and 21 are stacked on the illumination unit 1. The light guide plates 20 and 21 are formed of the same material in the same manner, and the light guide plates 20 and 21 are in contact with each other so that the exit surface thereof overlaps the surface opposite to the exit surface of the light guide plate thereon. Or, a predetermined air layer is provided between them for lamination.

  As shown in FIG. 3, the arrangement of the reflection portions 20 e of the light guide plate provides a matrix-like reflection portion pattern. However, since the two light guide plates 20 and 21 are formed identically, 21 has the same reflecting portion pattern. At that time, when the light guide plates are laminated, the light reflection plates are laminated so that the respective reflecting portion patterns are aligned. Therefore, as shown in FIG. 1, the reflecting portions 20e and 21e are arranged in the vertical alignment with the upper and lower light guide plates 20 and 21, respectively. Needless to say, the reflection portion patterns formed on the light guide plates 20 and 21 can be different patterns.

  In the lighting unit configured as described above, when the light source 13 is turned on, since the light source 13 is configured by a light emitting diode, light having high directivity is incident on the light guide plates 20 and 21. FIG. 1 illustrates various ray paths. This ray path is qualitatively illustrated to facilitate understanding of the present invention, and does not necessarily follow the laws of optics.

  The light incident on the light guide plates 20 and 21 is reflected, refracted, or scattered multiple times by the reflecting plates 10, 11 and 12, the surfaces 20 a to 20 d and 21 a to 21 d of the light guide plates 20 and 21, or the reflecting portions 20 e and 21 e. The light is emitted to the outside through the light emission surface 20b of the uppermost light guide plate 20. For example, the light beam L1 is repeatedly reflected on the upper and lower surfaces of the lower light guide plate 21, and then enters the air layer of the reflection portion 20e of the upper light guide plate 20, and refracts the upper light guide plate 20 to be emitted to the outside. The light beam L2 passes through the upper light guide plate 20 and is emitted to the outside without passing through the reflecting portions 20e and 21e from the lower light guide plate 21. The light beam L3 collides with the inclined surface of the reflecting portion 20e of the light guide plate 20, and is reflected, refracted, or scattered and guided to the exit surface side. Although not shown in FIG. 1, incident light is also reflected by the side reflectors (14, 15), and the reflected light repeats reflection, refraction, and scattering similar to those of the light beams L1 to L3.

  In this way, the light that has entered the light guide plate propagates through the light guide plate while being repeatedly reflected, refracted, or scattered along various paths, and light having high luminance is emitted from the light exit surface 20b of the light guide plate 20 above.

  FIG. 2 shows an embodiment of a conventional light guide plate, and shows an illumination unit in which a light guide plate 30 in which a large number of fine reflecting portions (scattering portions) 30a are printed on a surface opposite to an exit surface is printed with a white paint. In the illumination unit shown in the conventional example of FIG. 2, a part of the light emitted from the lower light guide plate 30 is reflected by the reflecting portion 30a of the upper light guide plate 30 and is not guided to the upper light guide plate. As in the configuration of FIG. 1, it is impossible to emit high-luminance light.

  In general, when a light guide plate is used, a light guide plate that is thin in the emission direction has higher emission efficiency than a light guide plate that is thick in the emission direction. This is because the number of reflections of light in the light guide plate increases and the probability of reflection and diffusion in the reflection part (diffusion pattern) increases when a plurality of thin light guide plates are stacked and arranged rather than one thick light guide plate. This is because light is efficiently emitted from the light emission surface. This effect is illustrated in FIG. 4, in which FIG. 4 (a) illustrates an illumination unit having a single light guide plate 20 and FIG. 4 (b) illustrates three light guide plates. 20, 21, and 22 are laminated, and the laminated thickness is the same as the thickness of one light guide plate in FIG. 4A, except that the light guide plate 22 has a different thickness. 1 light guide plates 20 and 21. As can be seen from FIG. 4B, the number of times the light guide plate is arranged in a stacked manner increases the number of times the light is reflected in the light guide plate, so that light is efficiently emitted from the light exit surface.

  As shown in FIG. 4A, a light guide plate with high emission efficiency can be obtained with the light guide plate itself in which a plurality of fine-shaped reflection portions 20e are interspersed, as shown in FIG. The illumination unit can be configured with only one light guide plate.

  In FIG. 5, the average luminance value that changes in accordance with the number of laminated light guide plates is shown as two values, an actual measurement value and a simulation value. From this figure, it can be seen that the average luminance value increases as the number of light guide plates is increased.

  In the embodiment described above, the shape of the reflecting portion 20e formed on the light guide plate 20 is a truncated cone shape. This effect is shown in FIG. 6 in comparison with a cylindrical reflecting portion. As shown in FIG. 6 (b), when the reflecting portion is formed in a cylindrical shape, only about 8% of the total luminance is obtained at a viewing angle of ± 20 °, whereas FIG. 6 (a) shows. Thus, when the truncated cone shape is used, illumination of about 80% of the overall luminance is obtained at a viewing angle of ± 20 °, and illumination with high emission efficiency is obtained even when compared with about 40%, which is a standard in a liquid crystal backlight. You can see that As described above, this is because the proportion of the light beam colliding with the inclined surface of the truncated cone increases the ratio of being guided to the exit surface side by reflection or refraction. Therefore, the reflecting portion can be not only a truncated cone shape, but also a cone shape having an inclined portion, a pyramid shape, a truncated pyramid shape, or a spherical shape.

  As described above, the reflective portions 20e of the light guide plate 20 are arranged so that the number per unit area gradually increases as the distance from the incident portion 20a of the light guide plate increases. This state is illustrated in FIG. In the light guide plate 20 as shown in FIG. 7A, the luminance of light emitted from the opposite surface 20c facing the light source 13 is increased in the vicinity of the incident portion 20a on the light source 13 side. Therefore, with one reflecting portion 20e as one dot, the dot density per area of D1 (88 mm) × D2 (48 mm) is reduced in the high luminance region (near the light source) shown in FIG. The dot density is increased as going to (near the light source). By such a method, an illumination unit that can emit more uniform illumination light over the entire surface of the light guide plate 20 can be obtained.

  FIG. 8A shows the sum of the energy emitted from the exit surface due to the increase in the number of light guide plates in the illumination unit according to the present invention, its average value, the output efficiency that is the ratio of the incident energy and the sum of the output energy, and the increase in the number of light guide plates. FIG. 8 (b) shows the change in the total output energy as the total number of dots increases, FIG. 8 (c) shows the change in the exit surface light beam as the total number of dots increases, and FIG. 8 (d) shows the change in the total number of dots. Indicates an average luminance change with an increase in the total number of dots. In both cases, the numerical values are simulated values with a viewing angle of ± 20 ° and a vertical and horizontal size of the light guide plate of 30 mm × 30 mm. From FIG. 8 (a), when the number of light guide plates increases, the total energy, its average value, emission efficiency, and the total number of dots increase, and when the total number of dots increases from FIGS. 8 (b), (c), and (d), It can be seen that the total output energy, the output surface light flux, and the average luminance are increased.

  FIG. 9 is a diagram illustrating the spectral characteristics of the light guide plate 20, where 41 is when light is incident from the surface (bottom surface) on which the reflecting portion is formed, and 42 is when light is incident from the opposite surface (upper surface) of the reflecting portion. The transmittance when entering from the reflecting portion surface is slightly higher than the transmittance when entering from the opposing surface of the reflecting portion, but each has a substantially constant high transmittance from a wavelength of about 420 nm or more. Show.

  In the embodiment of the lighting unit 1 shown in FIG. 1, the light guide plate is arranged so that a plurality of concave fine-shaped reflecting portions are dotted on the surfaces 20 d and 21 d on the opposite side of the light emission surfaces 20 b and 21 b. However, instead of this, a plurality of reflecting portions may be arranged on the light exit side surface of the light guide plate. Examples thereof are shown in FIGS.

  10, the same members as those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted. As in FIG. 1, two light guide plates 40 and 41 made of the same material and similarly configured are stacked on the illumination unit 1. The light guide plates 40 and 41 are respectively incident portions 40a and 41a for allowing visible light from the light source 13 to enter, end faces 40c and 41c facing the incident portions, exit-side surfaces 40b and 41b for emitting visible light, and the exit surfaces. And opposite surfaces 40d and 41c. Unlike the light guide plates 20 and 21, the light guide plates 40 and 41 are arranged with a plurality of convex fine reflection portions 40 e and 41 e scattered on the exit-side surfaces 40 b and 41 b.

  FIG. 11 illustrates the shape and arrangement pattern of the reflecting portion 40 e formed on the light guide plate 40. The reflecting portion 40e has a convex shape obtained by turning the reflecting portion 20e in FIG. 3 upside down, that is, a truncated cone shape, and the dimensions d1, d2, and d3 are the same as those in FIG. The thickness of the light guide plate 40 and the reflection portion pattern are the same as those in FIG. In FIG. 11, the upper part is the emission surface 40b.

  The light guide plate 41 also has the same thickness and reflection part pattern as the light guide plate 40, and is laminated so that the light guide plates 40 and 41 are in contact with each other and a predetermined air layer is formed between the light guide plates 40 and 41. The Thus, the illumination unit composed of the light guide plates 40 and 41 also emits uniform and high-intensity illumination light from the exit surface 40b of the upper light guide plate 40, and the same effect as the illumination unit of FIG. 1 is obtained. It is done.

  As described above, the convex or concave fine reflecting portion can be provided on the exit side surface (upper surface) and / or the surface opposite to the exit side surface (bottom surface), and an example thereof is shown in FIG. Has been.

  FIG. 12A shows a light guide plate 100 in which a concave reflecting portion 100a is arranged on the bottom surface, and corresponds to the light guide plates 20 and 21 in FIG. FIG. 12B shows a light guide plate 101 having a convex reflecting portion 101a disposed on the upper surface, and corresponds to the light guide plates 40 and 41 shown in FIG. FIG. 12C shows the light guide plate 102 with the convex reflection portion 102a arranged on the bottom surface, and FIG. 12D shows the light guide plate 103 with the concave reflection portion 103a arranged on the top surface.

  The convex or concave reflecting portions can be provided not only on one side of the light guide plate but also on both the top and bottom surfaces. 12 (e) shows the light guide plate 104 with the convex reflecting portion 104a on the top surface and the concave reflecting portion 104b on the bottom surface, and FIG. 12 (f) shows the concave reflecting portion 105a on the top surface and the concave reflecting portion. FIG. 12 (g) shows the light guide plate 105 with the concave reflection portion 106a on the top surface, and FIG. 12 (h) shows the light guide plate 106 with the convex reflection portion 106b on the bottom surface. A light guide plate 107 having a reflective portion 107a on the top surface and a convex reflective portion 107b on the bottom surface is shown.

  Even if any of the light guide plates 100 to 107 is used, an illumination unit that emits uniform and high-intensity illumination light as described above can be configured.

  FIG. 13 shows the lighting unit 1 in which the three light guide plates 20 described above are stacked and the reflectors 11, 12, 10, 14, and 15 are attached to the bottom surface, the end surface opposite to the incident portion, the incident side end surface, and the side surfaces, respectively. An embodiment in which a surface light emitting device to which a light source 13 composed of a high-intensity light emitting diode is attached is used as an illumination device will be described. As described above, the illumination unit emits high-luminance light uniformly from the emission surface 20b. At this time, light is effectively prevented from leaking from the end surface other than the exit surface 20b of the illumination unit due to the reflection of the light by the reflectors 11, 12, 10, 14, and 15 of the illumination unit. Can do.

  In the illumination unit according to the present invention, the light having a high directivity of the light emitting diode is reflected, refracted and diffused inside the light guide plate, and the light is emitted in a wide range through the emission surface. Therefore, the number of light emitting diodes to be used can be reduced, and manufacturing cost and power consumption can be reduced. Further, since the light emitting diode is disposed at the end of the light guide plate, the device can be miniaturized particularly in the thickness direction of the light guide plate. Furthermore, since a light emitting diode is used as a light source, it can contribute to a long life and low power consumption.

  In the embodiment of the present invention, the light source 13 has been described using a visible light LED. However, the lighting unit and the lighting device of the present invention are not limited to the visible light LED, for example, an ultraviolet light LED that emits ultraviolet light, or a red light that emits infrared light. Use of the external light LED as the light source 13 is not prevented.

  In the illumination unit according to the embodiment of the present invention, the shape of the light guide plate has been described using a quadrangle. Needless to say, however, a polygonal illumination unit can be used.

  Moreover, although the Example of this invention demonstrated the light source incident part as one place, even if it is an illumination unit which has many light source incident parts, the effect of this invention is not prevented.

It is explanatory drawing explaining the state from which the light ray from a light source radiate | emits in the illumination unit by this invention. It is explanatory drawing explaining the state from which the light ray from a light source radiate | emits in the illumination unit of a conventional structure. It is the fragmentary perspective view which showed the light-guide plate in which the reflection part was dotted with several in cross section. (A) is explanatory drawing explaining the light beam path | route in the illumination unit with one light-guide plate, (b) is explanatory drawing explaining the light beam path | route in the illumination unit which laminated | stacked three light-guide plates. It is the graph which showed the change of the average luminance by the change of the number of light-guide plates. (A) is the graph which showed the brightness | luminance change accompanying the viewing angle change when a reflection part has a truncated cone shape, (b) showed the brightness | luminance change accompanying the viewing angle change when a reflection part has a cylindrical shape. FIG. (A) is a top view of an illumination unit, (b) is a graph showing a state in which the dot density is changed according to the luminance value. (A) is a table showing the total energy, the average value, the output efficiency, and the change in the total number of dots in the illumination unit according to the present invention, and (b) shows the change in the total output energy with the increase in the total number of dots. FIG. 4C is a graph showing the change in the exit surface light flux accompanying the increase in the total number of dots, and FIG. It is the graph which showed the transmittance | permeability characteristic of the light-guide plate. It is explanatory drawing explaining the state from which the light ray from the light source in the other Example of an illumination unit radiate | emits. It is the fragmentary perspective view which showed the light-guide plate in which the reflection part was scattered in the Example of FIG. It is explanatory drawing explaining various light-guide plates. It is a perspective view of the illuminating device which combined the illumination unit and the light source.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Illumination unit 13 Light source 10, 11, 12, 14, 15 Reflection plate 20, 21, 40, 41, 100-107 Light guide plate 20e, 21e, 40e, 41a, 100a-107a, 100b-107b Reflection part

Claims (9)

A light guide plate comprising: an incident part for entering light from a light source; and an exit surface for propagating and emitting the light incident from the incident part.
A reflector for reflecting visible light emitted from other than the exit surface of the light guide plate, and an illumination unit comprising:
The light guide plate is disposed on at least one of the exit surface and the surface opposite to the exit surface, or both so as to be dotted with a plurality of fine-shaped reflective portions formed in a convex shape or a concave shape. A lighting unit characterized by that.   A plurality of the light guide plates are provided, and each light guide plate is laminated so that an emission surface thereof overlaps a surface opposite to the emission surface of the light guide plate thereon.   The illumination unit according to claim 2, wherein the reflection part pattern formed by the reflection part of the light guide plate is the same pattern for each light guide plate.   The lighting unit according to claim 3, wherein each of the light guide plates is stacked so that the reflection part patterns thereof are aligned.   5. The illumination unit according to claim 1, wherein the reflection portion of the light guide plate has a cone shape, a truncated cone shape, a pyramid shape, a truncated pyramid shape, or a spherical shape.   6. The illumination according to claim 1, wherein the reflection part of the light guide plate is arranged so that the number per unit area gradually increases as the distance from the incident part of the light guide plate increases. unit.   The reflector includes a rear reflector disposed on a surface opposite to the exit surface of the light guide plate, an end surface reflector disposed to face an end surface other than the end surface on which the light source is disposed, and a light source. 7. The apparatus according to claim 1, comprising at least one of a side-surface reflecting plate disposed to face both side surfaces intersecting with the end surface, and an incident-portion reflecting plate disposed on the light source side. The lighting unit according to any one of claims. The lighting unit according to any one of claims 1 to 7,
A light source that causes visible light to enter the incident portion of the light guide plate;
A lighting device comprising:   The lighting device according to claim 8, wherein the light source is a light emitting diode.

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