JP4113832B2 - Planar light source device and liquid crystal display device using the same - Google Patents

Description

  The present invention relates to a planar light source device and a liquid crystal display device using the planar light source device, and more particularly to improvement of means for supplying current to a plurality of point light sources used in the planar light source device.

  In general, a liquid crystal display device is provided with a planar light source device on the back side of a transmissive liquid crystal panel in which a liquid crystal layer is sandwiched between two insulating substrates and an image is displayed using the birefringence of the liquid crystal. ing. Conventionally, linear cold-cathode tubes have been used as light sources for planar light source devices. However, R, G, and B three-color light emitting diodes (hereinafter referred to as LEDs) are used because of their long life and good light emission. Some use multiple light sources. Further, there is a light source using a plurality of LEDs that emit white light. In a planar light source device used in a liquid crystal display device, light from an LED, which is a light source, enters from one end surface (light incident surface) of the light guide plate and is guided to the entire light emitting surface of the light guide plate, but improves brightness. For this purpose, it is necessary to arrange a plurality of LEDs to face the end face of the light guide plate.

  For example, Patent Document 1 discloses a planar light source device in which a plurality of LEDs are attached to a substrate in order to increase the brightness of a liquid crystal display device. In this example, a plurality of LEDs are arranged in series or in parallel on a substrate, and a wiring pattern for supplying current to the LEDs is formed on the substrate. Thus, when a plurality of LEDs are placed on the substrate, the brightness of the light source can be increased.

Japanese Patent Laid-Open No. 10-247748 (page 4, FIG. 9)

  However, in the case of series connection, the drive voltage increases as the number of LEDs increases, so when a large number of LEDs are mounted, the voltage must be boosted by an inverter or the like, and the number of LEDs is increased due to the limitation of the drive voltage. It was difficult to improve the luminance. In the case of parallel connection, it is not necessary to increase the drive voltage even if a large number of LEDs are mounted. However, the supply voltage to the LEDs is reduced due to the wiring resistance, resulting in luminance variations among the LEDs. was there. In addition, there is a problem that luminance variation occurs due to variation in LED characteristics.

  The present invention has been made to solve such a problem, and provides a planar light source device capable of being driven at a low voltage with high brightness without luminance variation, and a liquid crystal display device using the same. Objective.

A planar light source device according to a first aspect of the present invention includes a light guide plate having opposing light emitting surfaces and reflection surfaces, and four end surfaces connecting them, and a wiring board disposed along at least one end surface of the light guide plate. A light source group in which a plurality of point light sources are arranged on the wiring board in a direction parallel to the one end face of the light guide plate, and an end portion surrounding the wiring board and the light source group and adjacent to the one end face of the light guide plate fitted, and a reflector for reflecting the light from the light source group on the one end face of the light guide plate, a wiring board a planar light source device provided with a fixing means for fixing to the reflector, the wiring substrate anode wires and the cathode wires the point light sources of the source group are connected in parallel are formed, also two power supply input section provided at both ends of the wiring board in an extension of the direction of arrangement of the point light sources The positive and negative terminals of the It is connected to both ends of the cathode wiring, in which current is supplied from each of these power input unit to the point light sources.

The planar light source device according to the second aspect of the present invention is arranged along a light guide plate having a light emitting surface and a reflective surface facing each other and four end surfaces connecting them, and at least one end surface of the light guide plate. A wiring board, at least two sets of light sources each having a plurality of point light sources arranged on the wiring board in a direction parallel to one end surface of the light guide plate, and surrounding the wiring board and each light source group and one of the light guide plates The planar light source device includes a reflector that is fitted to an end adjacent to the end surface and reflects light from each light source group toward one end surface of the light guide plate, and a fixing unit that fixes the wiring board to the reflector. Te, two sets of light source group are arranged so as to face the upper and lower areas of the same length the width of the one end face of the light guide plate, a wiring board, corresponding to each set of light source groups, each set the anode wire and a cathode the point light sources are connected in parallel Line is formed, also the positive and negative terminals of the two power input unit provided at both ends of the wiring board in an extension of the direction of arrangement of the point light sources are, each anode wire and the cathode for each set of light source groups They are respectively connected to both ends of the wiring, and current is supplied from each of these power input portions to each point light source of each set .

Furthermore, the planar light source device according to the third aspect of the present invention is disposed along the light emitting plate and the reflecting surface facing each other, and the light guide plate having four end faces connecting them, and at least one end surface of the light guide plate. A wiring board, at least two sets of light sources each having a plurality of point light sources arranged on the wiring board in a direction parallel to one end surface of the light guide plate, and surrounding the wiring board and each light source group and one of the light guide plates The planar light source device includes a reflector that is fitted to an end adjacent to the end surface and reflects light from each light source group toward one end surface of the light guide plate, and a fixing unit that fixes the wiring board to the reflector. Te, two sets of light source group are arranged so as to face the upper and lower areas of the same length the width of the one end face of the light guide plate, a wiring board, corresponding to each set of light source groups, each set the anode wirings and cathode of the point light sources are connected in parallel Wiring is formed, also one of the first positive and negative terminals are two pairs of light source groups of the power supply input unit provided at one end of the wiring board in an extension of the direction of arrangement of the point light sources Connected to one end of anode wiring and cathode wiring corresponding to a set of light source groups, current is supplied from the first power input section to each point light source of one set of light source groups, and the direction in which the point light sources are arranged the anode wires and the cathode wires second positive and negative terminals of the power input unit provided on the other end of the wiring board in an extension has been corresponding to the other set of optical source group of the two sets of light source groups of Connected to the other end , a current is supplied from the second power input unit to each point light source constituting the other set of light sources .

According to the surface light source device in the first and second aspects of the present invention, the wiring board, the anode wiring and the cathode wiring connecting the point light sources of the light source groups in parallel is formed, also like the points positive and negative terminals of the two power input unit provided at both ends of the wiring board in an extension of the direction of arrangement of the light source are connected to both ends of the anode wires and the cathode wires, each of these two power input unit by supplying a current to the point light sources, the influence of the voltage drop due to the wiring resistance to a plurality of point light sources is eliminated, there is no brightness variation at high intensity, allowing low voltage drive.

Further, according to the surface light source device of the third aspect of the present invention, two sets of light source group are arranged so as to face the upper and lower areas of the same length the width of the one end face of the light guide plate, each set in response to the group of light source, the anode wires and the cathode wires each set of the point light sources are connected in parallel are formed, or one end of the wiring board in an extension of the direction of arrangement of the point light sources The positive and negative terminals of the first power input section provided in the first section are connected to one end of the anode wiring and the cathode wiring corresponding to one of the two sets of light sources, and the first power input current to the point light sources of one set of light source groups is supplied from the parts, also of the second power supply section provided on the other end of the wiring board in an extension of the direction of arrangement of the point light sources Positive and negative terminals are anode wiring and cathode wiring corresponding to the other light source group of the two light source groups. Is connected to the other end, by Rukoto it is current supplied to the point light sources of the other set of light source groups from the second power supply input section, canceled in both the luminance difference generated respectively in two sets of light source groups Therefore, since uniform light emission can be obtained, high luminance and no luminance variation are possible, and low voltage driving is possible.

  Embodiments 1 to 7, which are the best modes for carrying out the present invention, will be described below with reference to the drawings.

Embodiment 1 FIG.
The first embodiment is an embodiment corresponding to the first aspect of the present invention. FIG. 1 is an exploded perspective view showing a configuration of a liquid crystal display device using a planar light source device according to Embodiment 1 of the present invention, and FIGS. 2 and 3 each show a configuration of the planar light source device in Embodiment 1. It is a disassembled perspective view and sectional drawing. As shown in FIG. 1, the liquid crystal display device 1 in the present embodiment includes a liquid crystal panel 5 in which a liquid crystal layer is sandwiched between two insulating substrates, and a planar shape disposed on the back side of the liquid crystal panel 5. The light source device 20, the optical sheet 4 composed of a diffusion sheet, a protective sheet, a lens sheet, a prism sheet, and the like disposed between the liquid crystal panel 5 and the planar light source device 20, and disposed on the reflective surface side of the planar light source device 20. A reflection sheet 6 is provided.

  A transmissive liquid crystal panel 5 that displays an image using the birefringence of liquid crystal includes a TFT array substrate and a color filter substrate, and a liquid crystal layer is sandwiched between the two substrates. . The TFT array substrate includes a thin film transistor that is a switching element, a pixel electrode, and the like, and a driving voltage is applied to the pixel electrode by turning the switching element ON and OFF. The liquid crystal layer is aligned by this driving voltage, and a desired image is displayed. The color filter substrate includes a red, green, and blue colored layer, a light shielding layer (black matrix), and the like. The liquid crystal panel 5, the optical sheet 4, the planar light source device 20, and the reflection sheet 6 are fixed by a casing (not shown) to constitute the liquid crystal display device 1.

  Next, the planar light source device 20 according to the first embodiment will be described with reference to FIGS.

  The light guide plate 3 is made of acrylic, polycarbonate, or the like, and has a light emitting surface 3a and a reflective surface 3b facing each other and four end surfaces connecting these. In addition, the wiring board 11 is disposed along at least one end surface of the light guide plate 3, in this embodiment, one end surface 3c therein. The end surface 3c has a flat rectangular shape, and the rectangular end surface 3c has a pair of long sides 3d and a pair of short sides 3e. The direction in which the long side 3d extends is referred to as the X direction, the direction in which the short side 3e extends is referred to as the Z direction, and the direction orthogonal thereto is referred to as the Y direction. This Z direction is a direction in which the liquid crystal panel 5, the optical sheet 4, the planar light source device 20, and the reflection sheet 6 are laminated. The wiring board 11 is a printed wiring board having substantially the same length as the long side 3d, and a plurality of point light sources 10 are parallel to the long side 3d of the end face 3c of the light guide plate 3 on the upper surface, that is, the mounting surface 11a. A light source group 10a arranged at equal intervals in a row in the X direction is provided. The point light source 10 is a chip type light source having a light emitting diode (LED) which is a semiconductor light emitting element, and has a light emitting region on a surface substantially perpendicular to the mounting surface 11 a of the wiring substrate 11. That is, the light source group 10 a emits light having directivity in the Y direction toward the end surface 3 c of the light guide plate 3.

  The wiring board 11 and the light source group 10a are surrounded by the reflector 2 made of metal or white resin. The reflector 2 surrounds the wiring substrate 11 and the light source group 10 a and is fitted to an end adjacent to the one end surface 3 c of the light guide plate 3, so that the light from the light source group 10 a is directed toward the one end surface 3 c of the light guide plate 3. reflect. Thereby, the light emitted from the light source group 10a is reflected directly or by the reflector 2, enters the end surface 3c that is the light incident surface of the light guide plate 3, repeats total reflection in the light guide plate 3, and is applied to the entire surface. Led. The light emitted from the light emitting surface 3 a side of the light guide plate 3 passes through the optical sheet 4 and enters the liquid crystal panel 5. The light emitted from the reflection surface 3 b of the light guide plate 3 is reflected by the reflection sheet 6 and enters the light guide plate 3 again. Thus, the planar light source device 20 that efficiently emits light from the entire light emitting surface 3a is configured.

  Next, the configuration of the light source group 10a composed of a plurality of point light sources 10 and the wiring board 11 on which the light source group 10a is mounted will be described with reference to FIG. FIG. 4A is a perspective view showing the wiring board 11 on which the light source group 10a of the planar light source device 20 in the present embodiment is mounted. A plurality of point light sources 10 are attached to the upper surface of the wiring substrate 11, that is, the mounting surface 11 a in a line at equal intervals, thereby constituting a light source group 10 a. Each of the point light sources 10 is a substantially rectangular parallelepiped having a height of 1.3 mm, a width of 2 mm, and a depth of about 3 mm, and the wiring board 11 so that the light emitting surface thereof faces the end surface 3c that is the light incident surface of the light guide plate 3. Has been implemented. The light emitting region 13 formed on the light emitting surface of each point light source 10 is substantially elliptical, and has a width of 1.3 mm and a depth of about 2 mm. Light having directivity is emitted from the light emitting region 13 in the direction of the end surface 3 c of the light guide plate 3.

  Further, as shown in FIG. 4A, a wiring pattern for supplying current to the plurality of point light sources 10 is formed on the mounting surface 11 a of the wiring substrate 11. In the first embodiment, this wiring pattern includes two parallel wiring patterns of an anode wiring 12a and a cathode wiring 12b made of a strip of copper material, and from these anode wiring 12a and cathode wiring 12b. And a plurality of projecting portions projecting toward each other. Each point light source (LED) 10 is mounted in a state in which each anode is bonded to the protruding portion of the anode wiring 12a and each cathode is bonded to the protruding portion of the cathode wiring 12b.

Further, terminals (not shown) as power input portions are respectively provided at both ends 11c and 11d of the wiring board 11 on the extended line in the X direction in which a plurality of point light sources 10 are arranged, thereby constituting a light source group 10a. Current is supplied to both of the plurality of point light sources 10 from both sides. FIG. 4B is a circuit diagram showing a wiring pattern of the wiring board 11. A plurality of point light sources 10 are connected in the same direction to the anode wiring 12 a and the cathode wiring 12 b, and a DC is connected to both ends thereof. Power supplies 40c and 40d are connected. The DC power supply 40c is connected to both positive and negative terminals of a power input section provided at the end 11c, the positive terminal is connected to one end of the anode wiring 12a, and the negative terminal is connected to one end of the cathode wiring 12b. . The DC power supply 40d is connected to both positive and negative terminals of the power input section provided at the end 11d, the positive terminal is connected to the other end of the anode wiring 12a, and the negative terminal is connected to the other end of the cathode wiring 12b. Is done.

  When the point light source 10 is mounted on the wiring board 11, the point light source 10 is disposed on the wiring board 11 using a chip mounter, and soldered to the anode wiring 12a and the cathode wiring 12b on the wiring board 11. I do. At this time, due to mounting restrictions in the chip mounter, the light source is mounted with a space of 1 mm or more between the adjacent point light sources 10. By using a substrate made of glass epoxy resin or FPC (Flexible Printed Circuit) as the wiring substrate 11, the thickness of the substrate can be reduced to 1 mm or less. Further, as the length (depth) in the Y direction, the depth of the point light source 10 can be 3 mm, the wiring board 11 portion can be 2 mm, and the total length is 5 mm or less, so that the planar light source device 20 can be narrowed. be able to.

  Further, a structure for fixing the wiring board 11 on which the light source group 10a is mounted inside the reflector 2 will be described with reference to FIG. FIG. 5 is a side view showing a state in which the wiring board 11 used in the planar light source device 20 according to the first embodiment is fixed inside the reflector 2, and the reflector 2 extends from the end face 3 c that is the light incident surface of the light guide plate 3. Shows the state of seeing. Fixers 14 are attached to both ends of the lower surface 2b of the reflector 2 with an adhesive. The two fixtures 14 are arranged at an interval slightly shorter than the length of the wiring board 11. A recess 14a having the same thickness as that of the wiring board 11 is provided inside the fixing tool 14, and the wiring board 11 is sandwiched and fixed from the outside.

  As a material of the fixture 14, an elastic body such as silicon (Si) rubber is used. When attaching the wiring board 11, it is possible to insert the wiring board 11 into the recess 14 a by widening the interval between the fixtures 14. Moreover, since the light from the light source group 10a is reflected by making the fixture 14 white, the light use efficiency can be improved. In order to make the fixture 14 white, the fixture 14 made of a white material may be used, or it may be painted white. In the present embodiment, the fixing structure using the fixing tool 14 is used. However, the fixing structure of the wiring board 11 is not limited to this, and can be fixed by another structure. For example, holes may be formed at both ends of the wiring board 11, and a post or the like may be provided on the reflector 2 so as to correspond to the holes, and fixed with screws or the like.

  As described above, in the first embodiment, the planar light source device 20 including the light source group 10a in which the plurality of point light sources 10 are arranged on the wiring board 11 in the direction parallel to the one end surface 3c of the light guide plate 3. , A plurality of point light sources 10 constituting the light source group 10a are connected in parallel by two wiring patterns (anode wiring 12a and cathode wiring 12b) formed on the wiring substrate 11, and each point light source Since the current is supplied from the two power input portions provided at both ends 11c and 11d of the wiring board 11 on the extended line in the direction in which the 10 lines are arranged, the voltage due to the wiring resistance is applied to the plurality of point light sources 10 The planar light source device 20 that is free from the influence of the drop, has no luminance variation, has high luminance, and can be driven at a low voltage can be obtained.

Embodiment 2. FIG.
The second embodiment is an embodiment corresponding to the second and third aspects of the present invention. 6 and 7 are respectively an exploded perspective view and a cross-sectional view showing the configuration of the planar light source device according to Embodiment 2 of the present invention. In the drawings, the same and corresponding parts are denoted by the same reference numerals and description thereof is omitted. Further, the basic configuration of the liquid crystal display device using the planar light source device 20a in the present embodiment is the same as that of the first embodiment, and the description thereof is omitted (see FIG. 1).

The planar light source device 20a in the present embodiment includes two sets of light source groups 10a and 10b in which a plurality of point light sources are arranged in the X direction parallel to the long side 3d of the one end surface 3c of the light guide plate 3. Yes. In the present embodiment, these two sets of light source groups 10 a and 10 b are respectively provided on the upper surface 11 a and the lower surface 11 b facing each other of the wiring substrate 11, and have substantially the same length of the one end surface 3 c of the light guide plate 3. Opposite the upper and lower areas within the width.

  In the present embodiment, a chip-type light source having a light emitting diode (LED), which is a semiconductor light emitting element, is used as the point light source 10 as in the first embodiment, which is substantially the same as the mounting surface of the wiring board 11. It has a light emitting area on a vertical surface. Both the light source groups 10 a and 10 b emit light having directivity in the Y direction from the surface facing the end surface 3 c of the light guide plate 3, and this light is incident on the end surface 3 c that is a light incident surface of the light guide plate 3. Further, on the upper surface 11a and the lower surface 11b of the wiring board 11, as in the first embodiment, an anode wiring and a cathode for supplying current to the plurality of point light sources 10 constituting each of the light source groups 10a and 10b. Wiring (both not shown) is formed. Further, the fixing structure of the wiring board 11 is also the same as that of the first embodiment, and the description thereof is omitted.

  There are two means for supplying current to the two sets of light source groups 10a and 10b in the present embodiment. The first means corresponds to the second aspect of the present invention. Similarly to the first embodiment, power input portions (not shown) are provided at both ends 11c and 11d of the wiring board 11, respectively. The current is supplied from both sides to the plurality of point light sources 10 constituting the light source groups 10a and 10b. In this case, the terminal attached to the upper surface 11a of the wiring board 11 and the terminal attached to the lower surface 11b may be connected by a through hole or the like.

  The second means for supplying current corresponds to the third aspect of the present invention, and one of the two sets of light source groups 10a and 10b, for example, the light source group 10a has a dot-like shape of the light source group 10a. A current is supplied from a power input portion (not shown) provided at one end 11c of the wiring board 11 on the extended line in the direction in which the light sources 10 are arranged. A current is supplied from a power input portion (not shown) provided at the other end 11d. By any means, it is possible to obtain a planar light source device 20a which has high luminance and can be driven at a low voltage with no luminance variation. In this embodiment, an example in which two sets of light source groups 10a and 10b are provided has been described. However, the second means for supplying power is a planar light source device having two or more sets of even number of light source groups. Can be applied to.

  As described above, in the planar light source device 20a according to the second embodiment, the two sets of light source groups 10a and 10b are provided on the upper surface 11a and the lower surface 11b of the wiring board 11, which are opposed to each other. Increases the brightness. Further, by connecting the power input portion (terminal) attached to the upper surface 11a of the wiring board 11 and the power input portion (terminal) attached to the lower surface 11b through a through hole or the like, the wiring pattern is not complicated. Current can be supplied to the light source groups 10a and 10b on both sides, and the light source group 10a on the upper surface 11a and the light source group 10b on the lower surface 11b can obtain uniform light emission with no luminance difference.

  Further, a current is supplied to the light source group 10a from a terminal provided at one end 11c of the upper surface 11a of the wiring board 11, and a current is supplied from the terminal provided at the other end 11d of the lower surface 11b of the wiring board 11 to the light source group 10b. , The luminance difference generated in the light source group 10a on the upper surface 11a and the luminance difference generated in the light source group 10b on the lower surface 11b are canceled out, and uniform light emission can be obtained. Further, according to the second embodiment, the luminance can be improved without increasing the thickness of the planar light source device 20a and the liquid crystal display device using the same.

Embodiment 3 FIG.
The third embodiment is an embodiment corresponding to the second and third aspects of the present invention. A planar light source device according to Embodiment 3 of the present invention will be described with reference to FIGS. FIG. 8 is a perspective view showing a wiring board (state before bending) used in the planar light source device 20b in the present embodiment, and FIG. 9 is a wiring board (folding) used in the planar light source device 20b in the present embodiment. FIG. In the drawings, the same and corresponding parts are denoted by the same reference numerals and description thereof is omitted. In addition, the basic configuration of the liquid crystal display device using the planar light source device 20b in the present embodiment is the same as that in the first embodiment, and thus the description thereof is omitted (see FIG. 1).

  In the present embodiment, as shown in FIG. 8, two sets of light source groups 10 a and 10 b are provided on the same surface 11 a of the wiring board 11. The light source groups 10a are arranged in a line along one end face 11e of the wiring board 11, and the light source groups 10b are arranged in a line along an end face 11f facing the end face 11e on which the light source group 10a is provided. As the point light source 10, a chip type light source having a light emitting diode (LED) which is a semiconductor light emitting element is used as in the first embodiment, and is substantially perpendicular to the mounting surface 11 a of the wiring substrate 11. The surface has a light emitting region. In FIG. 8, the light emitting regions 13 of the light source groups 10 a and 10 b are all arranged outward with respect to the wiring board 11. Similarly to the first embodiment, anode wiring and cathode wiring (both not shown) for supplying current to the respective point light sources 10 are formed on the mounting surface 11 a of the wiring board 11.

Further, in the present embodiment, as shown in FIG. 9, the wiring board 11 is bent between the rows of the light source groups 10a and 10b with the surface 11b of the wiring board 11 on which the light source groups 10a and 10b are not provided facing inward. Thus, two sets of light source groups 10a and 10b are arranged on opposite surfaces. As a result, the light source groups 10a and 10b are arranged in an upper row and a lower row, respectively , facing the upper and lower areas within the same length width of the one end surface 3a of the light guide plate 3, and emitting light in the same direction.

  As the wiring substrate 11 used in the planar light source device 20b in the present embodiment, an FPC that can be easily bent is suitable. As described above, by using the FPC as the wiring board 11 in a bent state, an area where a wiring pattern can be formed is widened. Thereby, a wiring pattern for supplying current to the light source groups 10a and 10b can be easily formed, and current can be stably supplied to the plurality of point light sources 10, thereby improving display quality. Can be planned.

  Note that, as in the second embodiment, there are two means for supplying current to the two sets of light source groups 10a and 10b in the present embodiment. The first means corresponds to the second aspect of the present invention. Terminals that are power input portions are provided at both ends 11c and 11d of the wiring board 11, and two sets of light source groups 10a and 10b are respectively provided. A current is supplied from both sides to the plurality of point light sources 10 constituting the same.

  The second means for supplying current is a wiring board on an extension line in a direction in which the point light sources 10 of the light source group 10a are arranged in one set (for example, the light source group 10a) of the two sets of light source groups 10a and 10b. The current is supplied from the power supply input section provided at one end 11c of the power supply 11 and the other set (for example, the light source group 10b) is supplied from the power supply input section provided at the other end 11d of the wiring board 11 to the other set. It supplies current. By any means, it is possible to obtain a planar light source device 20b that has high luminance and can be driven at a low voltage with no luminance variation.

  The wiring board 11 according to the present embodiment is incorporated in the reflector 2 in a state as shown in FIG. 10, and is fixed as shown in FIG. 11 to complete the planar light source device 20b. Both of the two sets of light source groups 10 a and 10 b emit light having directivity in the Y direction from the surface facing the end surface 3 c of the light guide plate 3, and this light enters the end surface 3 c of the light guide plate 3. Since the fixing structure of the wiring board 11 is the same as that of the first embodiment, description thereof is omitted.

  As described above, in the planar light source device 20b according to the third embodiment, the two sets of the light source groups 10a and 10b are provided on the same surface 11a of the wiring board 11, and are used by being bent. The number increases and the brightness improves. Further, the light source groups 10a and 10b may be mounted only on one surface 11a of the wiring board (FPC) 11, so that the mounting process can be simplified and the productivity is improved. Furthermore, a heat radiation plate (not shown) made of a thin metal plate is provided on the surface 11b of the wiring board 11 where the light source groups 10a and 10b are not provided, and the heat radiation efficiency is improved by sandwiching between the folded wiring boards 11. . Also in the third embodiment, the luminance can be improved without increasing the thickness of the planar light source device 20b and the liquid crystal display device using the same.

Embodiment 4 FIG.
The fourth embodiment is an embodiment corresponding to the second and third aspects of the present invention. A planar light source device according to Embodiment 4 of the present invention will be described with reference to FIGS. 12 and 13 are an exploded perspective view and a sectional view, respectively, showing the configuration of the planar light source device according to Embodiment 4 of the present invention. In the drawings, the same and corresponding parts are denoted by the same reference numerals and description thereof is omitted. Further, the basic configuration of the liquid crystal display device using the planar light source device 20c in the present embodiment is the same as that of the first embodiment, and thus the description thereof is omitted (see FIG. 1).

  The planar light source device 20c in the present embodiment includes two sets of light source groups 10a and 10b in which a plurality of point light sources 10 are arranged side by side in the X direction parallel to the long side 3d of the one end surface 3c of the light guide plate 3. ing. In the present embodiment, the same number of light source groups as the number of light source groups, that is, two wiring boards 11 and 21 are provided, and two sets of light source groups 10a and 10b are provided on different wiring boards 11 (or 21). is there. In the present embodiment, as shown in FIG. 12, the light source group 10 a is provided on the wiring board 11 and the light source group 10 b is provided on the wiring board 21. As the point light source 10, a chip type light source having a light emitting diode (LED) which is a semiconductor light emitting element is used as in the first embodiment, and is substantially perpendicular to the mounting surface of the wiring boards 11 and 21. It has a light emitting area on the surface. Further, similarly to the first embodiment, anode wiring and cathode wiring (both not shown) for supplying current to the respective point light sources 10 are formed on the mounting surfaces of the wiring boards 11 and 21. .

  Further, the two wiring boards 11 and 21 are arranged to face each other with the surfaces on which the light source groups 10a and 10b are provided, respectively. As shown in FIG. 13, the wiring board 11 is attached to the upper surface 2 a of the reflector 2, and the wiring board 21 is attached to the lower surface 2 b of the reflector 2, so that the two light source groups 10 a and 10 b face each other vertically. Is provided. In the present embodiment, since the light source group 10a (10b) is provided only on one surface of the wiring board 11 (21), the entire surface on which the light source group 10a (10b) is not provided is brought into contact with the reflector 2. Can do. Thereby, the cooling efficiency of the light source group 10a (10b) can be improved. Further, in order to further increase the cooling efficiency, the wiring boards 11 and 21 can be pressed and brought into close contact with the reflector 2.

  FIG. 14 is a side view showing a state in which the wiring boards 11 and 21 used in the planar light source device 20 c in the present embodiment are fixed inside the reflector 2, and an end face 3 c that is a light incident surface of the light guide plate 3. The state which looked at the reflector 2 from FIG. As shown in FIG. 14, the wiring boards 11 and 21 may be fixed by providing a heat sink 15 between the wiring boards 11 and 21 and the reflector 2.

  The LED used for the point light source 10 usually varies in emission characteristics such as emission spectrum and chromaticity depending on the environmental temperature. In addition, the LED tends to decrease the amount of light emission when the environmental temperature increases. For this reason, in order to keep the luminance of the planar light source device 20c high and keep the chromaticity constant, it is desirable to keep the environmental temperature constant at a low temperature. In the present embodiment, since the light source group 10a (10b) is provided only on one surface of the wiring board 11 (21), the entire surface on which the light source group 10a (10b) is not provided is brought into contact with the heat radiating plate 15. be able to. Thereby, the heat generated from the light source groups 10a and 10b can be efficiently radiated to the reflector 2 side. Furthermore, the wiring boards 11 and 21 may be pressed against the heat dissipation plate 15 to improve the cooling efficiency.

  For example, a metal plate having a high thermal conductivity is used as the heat sink 15. Holes can be made in the end portions of the heat radiating plate 15 and the wiring boards 11 and 21 and fixed to the reflector 2 with screws or the like. The heat sink 15 is not used only for the planar light source device 20c in the present embodiment, but is also used for the planar light source devices 20, 20a, and 20b in the first to third embodiments. it can.

  Furthermore, in the planar light source device 20c in the present embodiment, as shown in FIG. 14, the point light sources 10 constituting the light source group 10a and the point light sources 10 constituting the light source group 10b do not overlap each other. It is desirable to arrange them alternately. Thereby, the brightness can be further uniformed. In the planar light source devices 20a and 20b having two sets of light source groups 10a and 10b as in the second embodiment and the third embodiment, the respective light source groups 10a and 10b are similar to the present embodiment. It is desirable that the point light sources 10 constituting the are arranged alternately.

  Note that the means for supplying current to the two sets of light source groups 10a and 10b in the present embodiment is the same as that in the second and third embodiments described above, in which the first is supplied simultaneously from both ends of the wiring boards 11 and 21. There is a first means and a second means for supplying current to the two sets of light source groups 10a and 10b from power supply input portions provided at opposite ends of the wiring boards 11 and 21, respectively. By any means, it is possible to obtain a planar light source device 20c that has high luminance and can be driven at a low voltage with no luminance variation.

  As described above, the planar light source device 20c according to the fourth embodiment includes the two wiring boards 11 and 21, and the two sets of light source groups 10a and 10b are respectively arranged on different wiring boards 11 (or 21). Since it provided, the number of the point light sources 10 increases and a brightness | luminance improves. Further, since the light sources 10a and 10b need only be mounted on one surface of the wiring boards 11 and 21, the mounting process can be simplified, and productivity is improved. Further, by making the configuration of the two wiring boards 11 and 21 and the arrangement of the point light sources 10 the same, the components of the two wiring boards 11 and 21 and the mounting process of the point light sources 10 can be unified. And productivity is improved.

Embodiment 5. FIG.
A planar light source device according to Embodiment 5 of the present invention will be described with reference to FIG. FIG. 15 is a circuit diagram showing a wiring pattern of a wiring board used in the planar light source device according to the present embodiment. In the present embodiment, as shown in FIG. 15, a plurality of point light sources 10 are connected in series, and are connected in parallel to a plurality of columns of anode wiring 12a and cathode wiring 12b. The number of point light sources 10 connected in series is preferably 3 to 6, so that it is not necessary to boost the power supply voltage with an inverter or the like.

  In general, when the point light sources 10 are connected in parallel, a luminance difference may occur in each chip due to variations in forward voltage due to the characteristics of the point light source (LED chip) 10. In order to suppress variation, a plurality of point light sources 10 are connected in series, and further connected in parallel in a plurality of columns. Thereby, the same value of electric power is supplied to the point-like light sources 10 connected in series, and luminance variations can be suppressed. Further, by connecting the point-like light sources 10 connected in series to the anode wiring and the cathode wiring in parallel, the influence of wiring resistance and the like is reduced, and uniform light emission with little luminance variation can be obtained.

Embodiment 6 FIG.
A planar light source device according to Embodiment 6 of the present invention will be described with reference to FIGS. 17 and 18. 17 and 18 are perspective views showing a wiring board and a light guide plate used in the planar light source device according to the sixth embodiment. In the drawings, the same and corresponding parts are denoted by the same reference numerals and description thereof is omitted. In addition, the basic configuration of the liquid crystal display device using the planar light source devices 20e and 20f in the present embodiment is the same as that in the first embodiment, and thus the description thereof is omitted (see FIG. 1).

  In the sixth embodiment, an example in which the wiring board 11 is arranged along two or three end faces of the light guide plate 3 will be described. A planar light source device 20e shown in FIG. 17 has a wiring board 11 bent at a substantially right angle so as to be along the two end faces of the light guide plate 3. On the wiring substrate 11, two sets of light source groups 10 a are provided in which a plurality of point light sources are arranged in a direction parallel to the respective end faces of the light guide plate 3. Although FIG. 17 shows the wiring board 11 bent at a substantially right angle, separate wiring boards may be arranged on each of the two end faces of the light guide plate 3.

Further, in the planar light source device 20 f shown in FIG. 18, the wiring substrate 11 bent in a U-shape is arranged along the three end surfaces of the light guide plate 3. On the wiring board 11, three sets of light source groups 10 a in which a plurality of point light sources are arranged in a direction parallel to the respective end surfaces of the light guide plate 3 are provided. In FIG. 18, the wiring board 11 bent in a U shape is shown, but separate wiring boards may be arranged on each of the three end faces of the light guide plate 3.
As described above, according to the sixth embodiment, since the number of light source groups 10a can be increased without increasing the thickness in the Z direction, planar light source devices 20e and 20f and a liquid crystal display device using the same. The luminance can be improved without increasing the thickness.

Embodiment 7 FIG.
A planar light source device according to Embodiment 7 of the present invention will be described with reference to FIGS. 19 and 20 are an exploded perspective view and a cross-sectional view showing the configuration of the planar light source device according to the seventh embodiment. In the drawings, the same and corresponding parts are denoted by the same reference numerals and description thereof is omitted. Further, the basic configuration of the liquid crystal display device using the planar light source device 20g in the present embodiment is the same as that of the first embodiment, and thus the description thereof is omitted (see FIG. 1).

In the seventh embodiment, three wiring boards 11, 21, and 31 are provided, and three sets of light source groups 10a, 10b, and 10c are provided on different wiring boards, respectively. In the present embodiment, as shown in FIG. 20, the light source group 10 a is provided on the wiring board 11, the light source group 10 b is provided on the wiring board 21, and the light source group 10 c is provided on the wiring board 31.
As described above, according to the seventh embodiment, since the number of light source groups 10a (10b, 10c) can be increased without increasing the width in the Y direction, a planar light source device with a narrow frame and high brightness. 20 g and a liquid crystal display device using the same can be obtained.

  The present invention is not limited to the configuration examples shown in the first to seventh embodiments, and various modifications can be made. For example, the size of the point light source (LED chip) 10 shown in the first embodiment is a typical example, and is not limited to this. The light emitting surface of the point light source 10 may be a surface substantially parallel to the mounting surface of the wiring board. Further, a current supply terminal of the wiring board may be provided only on one side of the board, and current may be supplied from both sides of the light source groups 10a and 10b by drawing a wiring pattern on the wiring board. Thereby, the wiring outside the wiring board can be simplified.

  The wiring substrate 11 may be a film substrate such as a flexible tape, or may be a substrate having a level difference that can provide the light source groups 10a and 10b in two rows. Further, as shown in FIG. 16, a reflector 22 having a function of an external housing of the planar light source device 20d may be used. Thus, by increasing the area of the reflector 22, the heat from the light source group 10a can be efficiently diffused and radiated, and the number of parts can be reduced. Further, instead of providing the reflector 2 alone, a housing for fixing the light guide plate 3 and the reflection sheet is formed of white resin or the like, and the light from the light source group 10a (10b) is reflected toward the end surface 3c of the light guide plate 3. You may make it have the function of the reflector to be made.

  The present invention is used for a liquid crystal display device, and can be used for a display device or monitor of a personal computer, a display device of a television, or the like.

It is a disassembled perspective view which shows the structure of the liquid crystal display device using the planar light source device in Embodiment 1 of this invention. It is a disassembled perspective view which shows the structure of the planar light source device in Embodiment 1 of this invention. It is sectional drawing which shows the structure of the planar light source device in Embodiment 1 of this invention. It is a perspective view which shows the wiring board used for the planar light source device in Embodiment 1 of this invention, and a circuit diagram which shows the wiring pattern of this wiring board. It is a side view which shows the state which fixed the wiring board used for the planar light source device in Embodiment 1 of this invention inside a reflector. It is a disassembled perspective view which shows the structure of the planar light source device in Embodiment 2 of this invention. It is sectional drawing which shows the structure of the planar light source device in Embodiment 2 of this invention. It is a perspective view which shows the wiring board (state before bending) used for the planar light source device in Embodiment 3 of this invention. It is a perspective view which shows the wiring board (state after bending) used for the planar light source device in Embodiment 3 of this invention. It is a disassembled perspective view which shows the structure of the planar light source device in Embodiment 3 of this invention. It is sectional drawing which shows the structure of the planar light source device in Embodiment 3 of this invention. It is a disassembled perspective view which shows the structure of the planar light source device in Embodiment 4 of this invention. It is sectional drawing which shows the structure of the planar light source device in Embodiment 4 of this invention. It is a side view which shows the state which fixed the wiring board used for the planar light source device in Embodiment 4 of this invention inside a reflector. It is a circuit diagram which shows the wiring pattern of the wiring board used for the planar light source device in Embodiment 5 of this invention. It is a disassembled perspective view which shows the planar light source device in Embodiment 7 of this invention. It is a perspective view which shows the wiring board and light guide plate which are used for the planar light source device in Embodiment 6 of this invention. It is a perspective view which shows the wiring board and light guide plate which are used for the planar light source device in Embodiment 6 of this invention. It is a disassembled perspective view which shows the structure of the planar light source device in Embodiment 7 of this invention. It is sectional drawing which shows the structure of the planar light source device in Embodiment 7 of this invention.

Explanation of symbols

1 liquid crystal display device, 2, 22 reflector, 2a upper surface, 2b lower surface, 3 light guide plate,
3a Light emitting surface, 3b Reflecting surface, 3c End surface (light incident surface) 3d Long side of light guide plate light incident surface,
3e Short side of light guide plate light incident surface, 4 optical sheet, 5 liquid crystal panel, 6 reflective sheet,
10 point light source (LED), 10a, 10b, 10c light source group,
11, 21, 31 Wiring board, 11a upper surface, 11b lower surface, 11c, 11d end,
11e, 11f end face, 12a anode wiring, 12b cathode wiring, 13 light emitting region, 14 fixture, 14a recess, 15 heat sink,
20, 20a, 20b, 20c, 20d, 20e, 20f, 20g Planar light source device.

Claims (10)

A light guide plate having opposing light emitting surfaces and reflective surfaces and four end surfaces connecting them, a wiring substrate disposed along at least one end surface of the light guide plate, and a plurality of point light sources on the wiring substrate A light source group arranged side by side in a direction parallel to the one end surface of the light guide plate, and the end portion adjacent to the one end surface of the light guide plate and surrounding the wiring board and the light source group, A planar light source device comprising: a reflector that reflects the light toward the one end surface of the light guide plate; and a fixing unit that fixes the wiring board to the reflector.
In the wiring board, anode wiring and cathode wiring in which the point light sources of the light source group are connected in parallel are formed, and at both ends of the wiring board on an extension line in the direction in which the point light sources are arranged. The positive and negative terminals of the two power input portions provided are respectively connected to both ends of the anode wiring and the cathode wiring, and current is supplied from the power input portions to the point light sources. A planar light source device. A light guide plate having opposing light emitting surfaces and reflective surfaces and four end surfaces connecting them, a wiring substrate disposed along at least one end surface of the light guide plate, and a plurality of point light sources on each of the wiring substrates At least two sets of light source groups arranged side by side in a direction parallel to the one end surface of the light guide plate, and the end portion adjacent to the one end surface of the light guide plate and surrounding the wiring board and each light source group And a planar light source device comprising a reflector that reflects light from each of the light source groups toward the one end surface of the light guide plate, and a fixing unit that fixes the wiring board to the reflector,
The two sets of light source groups are arranged so as to face upper and lower areas within the same length width of one end face of the light guide plate,
Wherein the wiring substrate, the corresponding to each set of light source groups, each set of the point light sources is connected to anode wiring and the cathode wiring is formed in parallel, and extending in a direction of arrangement of the respective point light sources The positive and negative terminals of two power input portions provided at both ends of the wiring board on the line are respectively connected to both ends of each anode wiring and each cathode wiring with respect to each set of light source groups. A planar light source device, wherein an electric current is supplied to each point light source of each set from an input unit . A light guide plate having opposing light emitting surfaces and reflective surfaces and four end surfaces connecting them, a wiring substrate disposed along at least one end surface of the light guide plate, and a plurality of point light sources on each of the wiring substrates At least two sets of light source groups arranged side by side in a direction parallel to the one end surface of the light guide plate, and the end portion adjacent to the one end surface of the light guide plate and surrounding the wiring board and each light source group And a planar light source device comprising a reflector that reflects light from each of the light source groups toward the one end surface of the light guide plate, and a fixing unit that fixes the wiring board to the reflector,
The two sets of light source groups are arranged so as to face upper and lower areas within substantially the same width of one end face of the light guide plate,
Wherein the wiring substrate, the corresponding to each set of light source groups, each set of the point light sources is connected to anode wiring and the cathode wiring is formed in parallel, and before SL direction of arrangement of the point light sources An anode wiring and a cathode wiring corresponding to one light source group of the two sets of light source groups, the positive and negative terminals of the first power input section provided at one end of the wiring board on the extension line The wiring board is connected to one end of the light source, is supplied with current from the first power supply input unit to each point light source of the one set of light source groups, and is on an extension line in the direction in which the point light sources are arranged. The positive and negative terminals of the second power supply input section provided at the other end of the second power source are connected to the other ends of the anode wiring and the cathode wiring corresponding to the other light source group of the two sets of light sources. each point-like light constituting the light source group of the other set from the second power supply unit Surface light source device and a current is supplied to.   4. The planar light source device according to claim 2, wherein two sets of the light source groups are arranged on the wiring board, and the two sets of light source groups are arranged on opposite surfaces of the wiring board. A planar light source device provided on each of the lower surfaces.   4. The planar light source device according to claim 2, wherein two sets of the light source groups are arranged on the wiring substrate, and the two sets of light source groups are provided on the same surface of the wiring substrate. 5. Further, the two sets of light source groups are arranged on opposite surfaces by bending the wiring board between the rows of the light source groups with the surface of the wiring substrate on which the light source group is not provided facing inward. A planar light source device.   4. The planar light source device according to claim 2, wherein the number of the wiring boards is the same as the number of the light source groups, and each of the light source groups is provided on a different wiring board. A planar light source device.   The planar light source device according to claim 6, wherein the wiring board includes two wiring boards, and the two wiring boards are arranged to face each other with a surface provided with the light source group inside. A planar light source device.   The planar light source device according to claim 1, further comprising a heat radiating plate between the wiring board and the reflector.   The planar light source device according to claim 1, wherein the point light source constituting the light source group has a light emitting region on a surface substantially perpendicular to the wiring board surface on which the point light source is provided. And a planar light source device that emits light toward the one end face of the light guide plate.   A transmissive liquid crystal panel that displays an image using birefringence of liquid crystal is disposed above the light emitting surface of the planar light source device according to any one of claims 1 to 9. Liquid crystal display device.

Images