JP2011113648A - Light source device and planar lighting system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light source device excellent in light emitting efficiency and suited for a side-light type planar lighting system. <P>SOLUTION: The light source device 10 includes an LED chip 11, a lead frame 21 mounting the LED chip 11, a resin sealed body 31 covering the LED chip 11, and a reflector 41 covering the surrounding of the resin sealed body 31. The resin sealed body 31 includes a rectangular parallelepiped base 32, and an elliptical semi-spherical protrusion 33 protruding forward from a front surface 32e of the base 32. Gaps G are formed between a pair of longitudinal side surfaces 32a, 32b which are side surfaces extending in a longitudinal direction of the base 32 and between a pair of longitudinal sidewalls 42a, 42b of the reflector 41. A pair of overhangs 43a, 43b covering the protrusion 33 of the resin sealed body 31 are formed on the pair of longitudinal sidewalls 42a, 42b of the reflector 41. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a light source device suitable for a sidelight type planar illumination device and a sidelight type planar illumination device using the light source device.

  A so-called side-light type planar illumination device in which a light source is arranged on the side surface (light-incident end surface) of a light guide plate as illumination means for a liquid crystal display panel is advantageous for thinning. Widely adopted mainly in the field of information equipment. As a light source disposed on the light incident end face of the light guide plate, an LED (Light Emitting Diode) excellent in miniaturization and low power consumption is frequently used.

  As the LED disposed on the light incident end face of the light guide plate, the present applicant, as shown in FIG. 5A, translucent resin covering an LED chip (not shown) mounted on a long rectangular substrate 71. In 72, an LED in which a protrusion 73 protruding in a semi-cylindrical shape is formed in front of the emission direction is proposed and put into practical use. By optimizing the curved surface shape of the projecting portion 73 and forming a notch portion 75b having a shape complementary to the projecting portion 73 on the light incident end surface 75a of the plate-like light guide plate 75, the emission plane of the light guide plate 75 is formed. Improvement of the brightness and uniformity of illumination light emitted in a planar shape from 75c has been achieved (see Patent Document 1).

JP 2006-228588 A

  However, recent planar illumination devices are required to have higher luminance in response to further higher definition of the liquid crystal display panel. Therefore, the present inventor has reexamined the LED disclosed in Patent Document 1 in detail from the viewpoint of increasing the brightness, and as a result, a pair of reflectors 76 arranged in parallel to the short direction (thickness direction) of the LED. , 76 (see FIG. 5 (b)), the light absorption loss is of a level that cannot be ignored. That is, there is still room for achieving higher emission efficiency of the LED and further higher luminance of the planar illumination device by reducing the light absorption loss by the pair of reflectors 76 and 76. I understood.

  The present invention has been made in view of the above situation, and is a light source device that is excellent in light emission efficiency, and a sidelight-type planar shape that is superior in luminance of illumination light by combining this light source device and a light guide plate. The object is to provide a lighting device.

  In order to solve the above problems, a light source device according to the present invention includes a light emitting element chip, a lead frame on which the light emitting element chip is mounted, and a pair of side surfaces facing each other and extending in a direction perpendicular to the optical axis. A resin sealing body that covers the light emitting element chip, and a reflector that has a pair of reflecting walls that respectively cover the pair of side surfaces, and the pair of side surfaces of the resin sealing body and the reflector A gap is formed between the pair of reflecting walls.

  According to the present invention, the light emitting element chip is covered with the resin sealing body including the base portion having a pair of side surfaces facing each other and extending in the direction orthogonal to the optical axis (resin sealing body including the substantially rectangular parallelepiped base portion). It has been broken. A gap is formed between the pair of side surfaces of the base and the pair of reflecting walls of the reflector that respectively cover the pair of side surfaces. As a result, the amount of light emitted from the light source device is increased, and a light source device having excellent emission efficiency can be realized. This is because by forming a gap between each side surface and each reflection wall, absorption of light by each reflection wall when light emitted from the light emitting element chip is reflected by each side surface is suppressed. is there. Moreover, it is because the ratio of the light reflected by the reflection wall among the light which passed each side surface decreases.

  In a preferred embodiment of the present invention, a protruding portion that protrudes forward is formed on the front surface, which is the surface of the base on the side from which light is emitted.

  In this case, it is preferable that the protruding portion is formed in an elliptical hemispherical shape.

  According to this invention, the emission efficiency of the light source device can be further improved.

  Moreover, in preferable embodiment of this invention, the overhang | projection part which covers the said protrusion part is formed in said pair of reflection wall, respectively.

  Further, the planar illumination device according to the present invention includes the light source device, a light incident end surface that receives light emitted from the light source device, and an output that emits light incident from the light incident end surface in a planar shape. A light guide plate having a flat surface, and a notch portion having a cross-sectional shape that follows the outer shape of the projecting portion of the pair of reflection walls along the thickness direction of the light guide plate. Is formed.

  According to this invention, the pair of reflecting walls of the reflector constituting the light source device is formed with the overhanging portion that covers the protrusion, and the light incident end surface of the light guide plate has a cross-sectional shape that follows the external shape of the overhanging portion. A notch is formed. For this reason, a light source device can be arrange | positioned at the light-incidence end surface of a light-guide plate so that the protrusion part of a reflector may be fitted in the notch part of a light-guide plate. Thereby, the light emitted from the light source device is efficiently guided into the light guide plate. As a result, a planar illumination device with higher brightness can be realized.

It is a perspective view which shows the whole structure of the light source device which concerns on embodiment of this invention. It is a disassembled perspective view of the light source device. It is a longitudinal cross-sectional view of the light source device. It is a graph which shows the relationship between the "gap" between the resin sealing body and reflective wall in the light source device, and "output efficiency". It is a perspective view which shows the principal part structure of the planar illuminating device using the conventional light source device, (a) is an exploded view, (b) is a joint figure.

  Hereinafter, a light source device 10 according to an embodiment of the present invention will be described with reference to FIGS. 1 to 3.

  The light source device 10 includes an LED chip 11 as a light emitting element chip, a lead frame 21 on which the LED chip 11 is mounted, a resin sealing body 31 that covers the LED chip 11, and a reflector 41 that covers the periphery of the resin sealing body 31. And.

  The LED chip 11 is a small blue LED chip that emits blue light (wavelength 410 nm to 480 nm). The LED chip 11 has a pair of electrode pads on the light emitting surface 11 a which is the front surface, and the mounting surface which is the back surface is fixed to the lead frame 21. Hereinafter, the direction in which the mounting surface of the LED chip 11 faces the light emitting surface 11a is referred to as “front”, and the direction in which the light emitting surface 11a faces the mounting surface is referred to as “rear”. The front-rear direction (direction perpendicular to the light emitting surface 11a) is referred to as an optical axis.

  Next, the lead frame 21 is made of a material (in this embodiment, a silver-plated copper plate, hereinafter referred to as a silver-plated copper plate) that is excellent in workability, light reflectivity, thermal conductivity, and the like and can be wire-bonded. Is formed. The lead frame 21 includes a long rectangular mounting portion 22, a rectangular connecting portion 23 that is connected to one long side of the mounting portion 22 (lower side in the illustrated example) and extends rearward, and a rear side of the connecting portion 23. A long rectangular heat dissipating portion 24 connected to and extending outward, and a pair of electrode terminal portions 25, 25 having an L-shaped cross section disposed separately from the mounting portion 22 on both longitudinal sides of the mounting portion 22; Yes.

  The mounting portion 22 is a portion where the LED chip 11 is fixedly arranged. In the present embodiment, the LED chip 11 is fixed to the central portion of the mounting portion 22 using an adhesive.

  The connecting portion 23 and the heat radiating portion 24 are portions for radiating Joule heat generated from the LED chip 11 to the outside. By bringing the heat radiating portion 24 into contact with a heat sink (not shown), heat can be efficiently radiated to the outside.

  The pair of electrode terminal portions 25, 25 are arranged on the same plane as the mounting portion 22 so as to coincide with the center line and are covered with the resin sealing body 31, and are orthogonal to the first terminal portion 25 a and rearward And a rectangular second terminal portion 25b whose rear end is exposed to the outside by extending toward the outside. In the present embodiment, the first terminal portion 25a has a dimension in a direction (vertical direction in the figure) corresponding to the short direction of the mounting portion 22 set to be slightly shorter than the dimension of the mounting portion 22 in the same direction. This is to ensure insulation between the pair of electrode terminal portions 25, 25 and the reflector 41.

  The pair of first terminal portions 25a and 25a are respectively wire-bonded and electrically connected to a pair of electrode pads formed on the light emitting surface 11a of the LED chip 11 via the pair of bonding wires 26 and 26. ing. On the other hand, the pair of second terminal portions 25 b and 25 b are electrically connected to a circuit board (not shown) at a portion exposed from the resin sealing body 31. With this configuration, an electric signal from a control circuit unit (not shown) arranged outside is supplied to the LED chip 11 via the pair of electrode terminal units 25 and 25 and the bonding wires 26 and 26. Can do.

  Next, the resin sealing body 31 is formed of a translucent material (silicone resin in the present embodiment), and the translucent material receives blue light emitted from the LED chip 11 and emits yellow component light. The yellow phosphor that emits light is dispersed. That is, the resin sealing body 31 is formed so that predetermined white light can be obtained by mixing the yellow light emitted from the yellow phosphor with the blue light emitted from the LED chip 11.

  The resin sealing body 31 includes a rectangular parallelepiped base portion 32 and a protruding portion 33 protruding forward from the base portion 32.

  The base 32 is horizontally long along the longitudinal direction of the mounting portion 22 of the lead frame 21 so as to integrally cover a part of the LED chip 11, the mounting portion 22 of the lead frame 21, and each electrode terminal portion 25 of the lead frame 21. Is formed. The base 32 has, as its outer peripheral side, a long rectangular upper side surface 32a that extends in the direction orthogonal to the optical axis, a lower long side surface 32b that faces the upper long side 32a in parallel, and an upper length. Both ends of the side surface 32a and the lower long side surface 32b are connected to each other, and have a left short side surface 32c and a right short side surface 32d that are shorter in the circumferential direction than the upper long side surface 32a (lower long side surface 32b). is doing. The base portion 32 is a front surface among the surfaces defined by the four side surfaces 32a to 32d and is a front surface 32e that is a surface on which light is emitted, and a rear surface that is a surface facing the front surface 32e. 32f. The LED chip 11, the mounting portion 22 of the lead frame 21, and the first terminal portion 25 a of each electrode terminal portion 25 are disposed at an intermediate portion between the front surface 32 e and the rear surface 32 f. The upper long side surface 32a and the lower long side surface 32b correspond to “a pair of side surfaces” in the present invention.

  Further, the base portion 32 is formed such that the longitudinal dimension thereof is somewhat longer than the distance between the outer end faces of the pair of electrode terminal portions 25, 25. This is to ensure insulation between the pair of electrode terminal portions 25, 25 and the reflector 41.

  The protruding portion 33 is formed at the central portion in the longitudinal direction of the front surface 32 e of the base portion 32, is arc-shaped in both the short side direction and the long side direction of the base portion 32, and the long axis direction is the longitudinal direction of the base portion 32. Matching elliptical hemispheres are formed. The dimension of the protrusion 33 in the short direction is the same as the dimension of the base 32 in the same direction.

  Next, the reflector 41 is configured using a silver-plated copper plate in the present embodiment, and includes a frame-like portion 42 that covers each outer peripheral side surface of the base portion 32 of the resin sealing body 31 in parallel, and the resin sealing body 31. The projecting portion 33 includes projecting portions 43 (an upper projecting portion 43a and a lower projecting portion 43b) that cover both sides in the short direction of the projecting portion 33 in parallel.

  The frame-shaped portion 42 includes an upper long side wall 42a, a lower long side wall 42b, which cover the upper long side surface 32a, the lower long side surface 32b, the left short side surface 32c, and the right short side surface 32d of the base portion 32 of the resin sealing body 31, respectively. It consists of a left short side wall 42c and a right short side wall 42d. Among these, the upper long side wall 42a and the lower long side wall 42b correspond to “a pair of reflecting walls” in the present invention.

  Further, the distance L1 (see FIG. 3) between the inner surface of the upper long side wall 42a and the inner surface of the lower long side wall 42b of the frame-like portion 42 is predetermined from the dimension L2 in the short direction of the resin sealing body 31 (base portion 32). It is formed larger by the value of. Thereby, between the upper long side wall 42a of the frame-shaped part 42 and the upper long side surface 32a of the resin sealing body 31, and the lower long side wall 42b of the frame-shaped part 42 and the lower long side surface 32b of the resin sealing body 31 A gap G having the same dimension is formed over the entire area. The gap G is G = (L1−L2) / 2, and is constant from the rear surface 32f side to the front surface 32e side of the base portion 32.

  On the other hand, the distance between the inner surface of the left short side wall 42 c and the inner surface of the right short side wall 42 d of the frame-like portion 42 is the same as the longitudinal dimension of the resin sealing body 31. This is because in the present embodiment, the reflector 41 is integrated with the resin sealing body 31 with the left short side wall 42c and the right short side wall 42d of the frame-like portion 42 as the joint surfaces.

  The overhanging portion 43 is formed in a shape that substantially covers the entire protruding portion 33 of the resin sealing body 31 when viewed in plan. That is, the pair of overhanging portions 43a and 43b are formed so as to protrude forward from the central portion of the front side of the upper long side wall 42a and the lower long side wall 42b of the frame-like portion 42, respectively. The outer shape substantially coincides with the maximum arc shape of the protruding portion 33 of the resin sealing body 31 (the arc shape in the longitudinal direction at the center in the short direction).

  Next, the operation of the light source device 10 configured as described above and the planar illumination device configured by combining the light source device 10 and a conventional light guide plate will be described. Note that the conventional light guide plate will be described with reference to FIGS. 5A and 5B with the same reference numerals.

  First, an electrical signal from a control circuit unit (not shown) for driving an object to be illuminated (in this embodiment, a liquid crystal display panel) causes a pair of electrode terminal units 25 and 25 and bonding wires 26 and 26 of the lead frame 21 to be connected. Via the LED chip 11. The LED chip 11 emits blue light based on the electrical signal. A part of the blue light emitted from the LED chip 11 is converted into yellow light by the yellow phosphor mixed in the resin sealing body 31. Then, blue light and yellow light are mixed to generate white light.

  The generated white light is emitted forward from the protruding portion 33 of the resin sealing body 31, and enters the light guide plate 75 from a notch 75 b formed on the light incident end surface of the light guide plate 75. The light incident on the light guide plate 75 is propagated through the light guide plate 75, and the light path is changed by the light path changing means formed on the reflection plane of the light guide plate 75 (the plane opposite to the emission plane 75c). The light is emitted from 75 emission planes 75c. The light emitted from the emission plane 75c of the light guide plate 75 is adjusted to a predetermined viewing angle distribution by passing through the diffusion plate and the pair of prism sheets as necessary, and then enters the back surface of the liquid crystal display panel. . Thereby, the image displayed on the liquid crystal display panel is visually recognized by the viewer on the front side.

  Next, a description will be given of the specific effects obtained by the light source device 10 and the planar illumination device using the light source device 10.

  The light source device 10 includes a pair of long side surfaces 32a and 32b in a short direction and a pair of long side surfaces 32a and 32b of the base 32 formed in a rectangular parallelepiped shape covering the LED chip 11 in the resin sealing body 31. Between the pair of long side walls 42a, 42b of 41, gaps G having a constant size in the front-rear direction are formed. Thereby, the light absorption by the pair of long side walls 42a and 42b when the light emitted from the LED chip 11 is incident on and reflected by the pair of long side surfaces 32a and 32b is suppressed. As a result, the amount of light emitted from the light source device 10 is increased, and the light source device 10 having excellent emission efficiency can be realized.

  In the light source device 10, a gap is also formed between the protruding portion 33 and the protruding portion 43 of the reflector 41 that covers the protruding portion 33. Thereby, absorption of light by the protruding portion 43 when the light emitted from the LED chip 11 is incident on the surface of the protruding portion 33 and reflected is suppressed, and the amount of light emitted from the light source device 10 is increased.

  Here, FIG. 4 shows the result of analyzing the relationship between the emission efficiency and the total 2G of the gap between the pair of long side surfaces 32a and 32b of the base portion 32 of the resin sealing body 31 and the pair of long side walls 42a and 42b of the reflector 41. Show. It can be seen that the emission efficiency of the light source device is increased by forming the gap 2G. This result proves that the amount of light emitted from the light source device 10 is increased by forming a gap between the pair of long side surfaces 32a and 32b and the pair of long side walls 42a and 42b.

  Note that, as the gap G is increased, the emission efficiency tends to be improved, though slightly. The reason why the emission efficiency is improved is considered as follows. That is, the light that has passed through the pair of long side surfaces 32 a and 32 b and leaked to the outside is reflected by the reflector 41 (the pair of long side walls 42 a and 42 b and the pair of projecting portions 43 a and 43 b) and returned to the resin sealing body 31. However, the larger the gap G, the greater the proportion of the light that has passed through the pair of long side surfaces 32a and 32b and exits forward without entering the reflector 41. In addition, the number of multiple reflections between the pair of long side surfaces 32 a and 32 b of the resin sealing body 31 and the pair of long side walls 42 a and 42 b of the reflector 41 is reduced. For this reason, it is considered that as the gap G is larger, the light absorption by the reflector 41 is reduced and the emission efficiency is improved.

  Further, in the light source device 10, the protruding portion 33 of the resin sealing body 31 is formed in an elliptical hemispherical shape. Thereby, the emission efficiency can be further increased. The present inventor has found that a light source device having an elliptical hemispherical protrusion has an emission efficiency of 7 as compared with a light source device having a conventional semicylindrical protrusion (the outer shape is constant in the lateral direction). % Has been confirmed.

  Moreover, the light source device 10 forms the heat radiation part 24 by exposing a part of the lead frame 21 on which the LED chip 11 is mounted to the outside. By bringing the heat dissipating part 24 into contact with a heat sink (not shown), the heat generated from the LED chip 11 can be dissipated to the heat sink. Thereby, the temperature rise of the LED chip 11 can be suppressed, and the emission efficiency of the light source device 10 can be further improved.

  In this way, by combining the light source device 10 having excellent emission efficiency with the conventional light guide plate 75, a sidelight type planar illumination device having excellent luminance of illumination light can be realized. In particular, the light emitted from the light source device 10 can be efficiently guided to the light guide plate 75 by fitting the protruding portion 43 of the reflector 41 to the notch 75 c formed on the light incident end surface 75 a of the light guide plate 75. And the brightness of the illumination light can be further improved. Moreover, since the resin sealing body 31 and the reflector 41 are integrated, the assembly workability | operativity of a planar illuminating device improves.

  The preferred embodiments of the present invention have been described above. However, the embodiments are not limited to the above, and various modifications and combinations can be made without departing from the gist of the present invention.

  For example, in the above embodiment, between the upper long side surface 32 a of the resin sealing body 31 and the upper long side wall 42 a of the reflector 41, and the lower long side surface 32 b of the resin sealing body 31 and the lower long side wall 42 b of the reflector 41. The size of the gap G between the two is the same, but may be different from each other.

  Moreover, in the said embodiment, although the protrusion part 33 is formed in the resin sealing body 31, the protrusion part 33 does not necessarily need to be formed depending on the use of the light source device 10, or the specification requested | required. When the protruding portion 33 is not formed, the protruding portion 43 may not be formed on the reflector 41.

  Moreover, in the said embodiment, although the base 32 of the resin sealing body 31 is formed in the rectangular parallelepiped, you may form the shape of a short end surface into a circular arc instead of a plane, for example, and may form in a substantially rectangular parallelepiped shape as a whole.

  Moreover, in the said embodiment, although the thermal radiation part 24 is formed in the lead frame 21, when thermal radiation property is not regarded as important, the thermal radiation part 24 does not necessarily need to be formed.

  Moreover, in the said embodiment, although a pair of short side surface 32c, 32d of the resin sealing body 31 and a pair of short side wall 42c, 42d of the reflector 41 are joined, a clearance gap is not formed between both. It is not limited. For example, when the distance between the LED chip 11 and the pair of short side surfaces 32c and 32d (the pair of short side walls 42c and 42d) is relatively short and the ratio of light incident on the pair of short side surfaces 32c and 32d is high, A gap may also be provided between the short side surfaces 32c and 32d and the pair of short side walls 42c and 42d.

  Moreover, in the said embodiment, although the clearance gap G is formed between a pair of reflective walls 42a and 42b over the whole region of a pair of long side surfaces 32a and 32b, it is not limited to this. For example, a gap is formed between the pair of reflecting walls 42a and 42b in a portion of the pair of long side surfaces 32a and 32b where the ratio of light incident on the front side of the mounting portion 22 of the lead frame 21 is relatively high. If so, a certain effect can be expected. Also, if a gap is formed between the pair of long side surfaces 32a and 32b and the pair of reflecting walls 42a and 42b in the portion closer to the center (portion close to the LED chip 11), as well. A certain effect can be expected.

  Moreover, in the said embodiment, although the pair of electrode terminal parts 25 and 25 of the lead frame 21 were L-shaped in cross section, it is not limited to this. For example, when a plurality of light source devices are arranged in a straight line, each electrode terminal portion is formed in a linear shape extending toward the adjacent light source device, and the ends of the adjacent electrode terminal portions are connected by, for example, a connector. It is good also as a structure.

  The use of the light source device according to the present invention is not limited to the sidelight type planar illumination device, but can be applied to other uses including general illumination.

10 Light source device 11 LED chip (light emitting element chip)
21 Lead frame 22 Mounting portion 23 Connecting portion 24 Heat radiating portion 25 A pair of electrode terminal portions 26 Bonding wire 31 Resin sealing body 32 Base portion 32a Upper long side surface (a pair of side surfaces)
32b Lower long side (a pair of sides)
32c Left short side surface 32d Right short side surface 32e Front surface 32f Rear surface 33 Projection portion 41 Reflector 42 Frame-shaped portion 42a Upper long side wall (a pair of reflection walls)
42b Lower long side wall (a pair of reflecting walls)
42c Left short side wall 42d Right short side wall 43 Overhang portion (43a upper overhang portion, 43b lower overhang portion)

Claims (5)

A light emitting device chip;
A lead frame on which the light emitting element chip is mounted;
A resin sealing body that includes a base portion having a pair of side surfaces facing each other and extending in a direction perpendicular to the optical axis, and covering the light emitting element chip;
A reflector having a pair of reflecting walls that respectively cover the pair of side surfaces;
A light source device in which a gap is formed between the pair of side surfaces of the resin sealing body and the pair of reflection walls of the reflector.   The light source device according to claim 1, wherein a protruding portion that protrudes forward is formed on a front surface that is a surface of the base portion on which light is emitted.   The light source device according to claim 2, wherein the protruding portion is formed in an elliptical hemispherical shape.   4. The light source device according to claim 2, wherein an extension portion that covers the protruding portion is formed on each of the pair of reflection walls. 5. A light source device according to claim 4,
A light guide plate having a light incident end surface that receives light emitted from the light source device, and a light emission plate that emits light incident from the light incident end surface in a planar shape,
A planar illumination device in which a cutout portion having a shape following the outer shape of the projecting portion is formed in the light incident end face of the light guide plate along the thickness direction of the light guide plate.

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