Patent Application
20150234117
The present invention relates to a light source device, and more particularly to a light source device that is provided with a light guide plate and emits light in a planar manner. The present invention also relates to a display device provided with such a light source device.
A liquid crystal display device is known as an example of a display device that display images. Liquid crystal display devices are provided with a liquid crystal panel and a light source device (referred to as a backlight device) that illuminates the liquid crystal panel from behind. These light source devices include types known as direct-lit and edge-lit (side-lit) devices.
As disclosed in Patent Document 1, for example, an edge-lit type light source device is provided with a light source and a light guide plate arranged so that light from the light source enters from the end (side) of the light guide plate. According to Snell's law, among the light that has emerged from the light source and entered the light guide plate, light having an angle component greater than the critical angle repeatedly undergoes total reflection inside the light guide plate, and light having an angle component smaller than the critical angle is emitted outside the light guide plate. Light scattering elements that cause light to scatter (scattering dots, unevenness, etc.) are formed on one of the two mutually facing principal surfaces of the light guide plate. As a result, light undergoing total reflection inside the light guide plate can be extracted to the outside of the light guide plate, and emitted in a planar manner.
Patent document 1 discloses a technique for positioning and fixing the light guide plate to a frame that forms a portion of the light source device, so that the light guide plate does not become displaced with respect to the frame.
Variation is present in the dimensions of the components constituting a light source device (dimensional variation), and variation (assembly variation) also arises during assembly of a light source device. These variations can cause deterioration in the display quality of a display device in which the light source device is incorporated. Examples of deterioration in display quality are described below.
As a result of the dimensional variation and/or assembly variation described above, differences can arise between the clearance CL1 between the light source 102 and the first end face 101a and the clearance CL2 between the light source 102 and the second end face 101b in the conventional light source device 100, as shown in
In this kind of light source device 100, an imbalance in brightness (luminance) can arise, as shown in
When using the technique disclosed in Patent Document 1, it is possible to suppress the occurrence of variation in clearance between the light guide plate and light sources caused by assembly variation. However, if component dimensional variation has occurred, for example, there is a concern that the non-uniform display quality described above could easily occur when using this technique.
In consideration of the situation described above, an objective of the present invention is to provide a light source device that readily suppresses the occurrence of uneven brightness resulting from component dimensional variation and assembly variation. A further objective of the present invention is to provide a display device that readily suppresses deterioration in display quality through the provision of such a light source device.
To achieve the aforementioned objectives, a light source device of the present invention has a configuration includes: a light source a light source; a light guide plate having an end face into which light emitted from the light source enters; and a clearance adjustment part for adjusting clearance between the light source and the light guide plate (configuration 1).
According to this configuration, clearance between the light source and the light guide plate can be easily set to a prescribed value (design value) because clearance adjustment parts are provided. In other words, according to this configuration, it is possible to provide a light source device that readily suppresses the occurrence of uneven brightness resulting from component dimensional variation and assembly variation.
In the light source device according to configuration 1, it is preferable that the clearance adjustment part comprise: a protruding member that projects from part of a first member forming a portion of the light source device; and a contact surface that is included on a second member forming a portion of the light source device and that contacts the protruding member (configuration 2). According to this configuration, the clearance adjustment parts can be obtained without increasing the number of new members; this is beneficial in terms of cost.
The light source device of configuration 2 may further include a substrate on which the light source is mounted; and a heat dissipation member to which the substrate is attached, wherein the protruding member is formed on the end face of the light guide plate, and wherein the contact surface is included on one of the substrate and the heat dissipation member (configuration 3).
It is preferable that the light source device according to configuration 3 further include a securing member to which the heat dissipation member is secured by a fastener, that an engaging hole that engages with the fastener be formed in the securing member, that a through-hole into which the fastener is inserted is formed in the heat dissipation member, and that the through-hole is larger than the engaging hole (configuration 4). A screw can be cited as an example of the fastener. According to this configuration, clearance between a light source and a light guide plate can be adjusted to a design value by screw-fastening a heat dissipation member (to which is attached a substrate on which is mounted a light source) to a chassis (securing member) of a light source device.
The light source device according to configuration 2 may be further provided with a substrate on which the light source is mounted, wherein the protruding member is formed on the end face of the light guide plate, and wherein the contact surface is included on the substrate (configuration 5). The light source device according to the present configuration is also useful in that the heat dissipating member may be shared with external components of a device (liquid crystal display device, etc.) incorporating a light source device, for example.
The light source device of any of configurations 1 to 5 may be configured such that the light source is provided on each of two end faces of the light guide plate that oppose each other (configuration 6). In a light source device in which the light sources are arranged opposite each of the two mutually facing end faces of the light guide plate, component dimensional variation and assembly variation can cause imbalance in brightness over a region bounded by the center of the light guide plate, for example. However, the present configuration can reduce the possibility of such a condition (imbalance in brightness) arising, because the present configuration is provided with clearance adjustment parts.
To achieve the above-described objectives, a display device according to the present invention is configured so as to include the light source device according to any of configurations 1 to 6; and a display panel illuminated with light by the light source device (configuration 7). The display device according to the present configuration is configured so as to be provided with a light source device that readily suppresses the occurrence of uneven brightness due to component dimensional variation and assembly variation, and can therefore readily suppress deterioration in display quality.
In the display device according to the seventh configuration, a configuration in which the display panel is a liquid crystal panel (configuration 8) may be adopted.
By means of the present invention it is possible to provide a light source device that readily suppresses the occurrence of uneven brightness resulting from component dimensional variation and assembly variation. Also, by means of the present invention it is possible to provide a display device that readily suppresses deterioration in display quality by being provided with such a light source device.
Embodiments of the light source device and display device of the present invention are described below with reference to the drawings.
The light guide plate 12 is a substantially rectangular, flat member in top view, and is formed from a resin such as polymethyl methacrylate (PMMA), for example. The light sources 13 are arranged respectively opposite two end faces 12a and 12b (mutually facing end faces 12a, 12b) that are parallel in a lengthwise direction of the light guide plate 12. Protruding members 121 that project in a direction substantially perpendicular to the two end faces 12a and 12b are provided at both lengthwise ends of the two end faces 12a and 12b. The protruding members 121 provided on the two end faces 12a and 12b are arranged symmetrically with a principal surface of the light guide plate 12 interposed therebetween. The protruding members 121 may be separate members to the light guide plate 12, but it is preferable that the protruding members 121 be molded integral to the light guide plate 12. Also, a shape of the protruding members 121 has no particular limitations, and can be cylindrical, prismatic or the like, for example. Further, it is preferable that the protruding members 121 be members that readily transmit light.
As the light source 13, an LED (Light Emitting Diode) is suitable, but other light emitting elements may be used. The light sources are 13 are mounted on a substrate 131 and are arranged in rows in parallel to a lengthwise direction of the end faces 12a and 12b of the light guide plate 12. The substrate 131 is secured to a heat spreader 15. As the substrate 131, a known printed substrate can be used, and this may be a flexible substrate such as an FPC (Flexible Printed Circuit), or a rigid substrate, for example. In this embodiment, the number of substrates 131 arranged opposite the end faces 12a and 12b is more than one (two in this embodiment), but the number of substrates may be changed to one depending on circumstances.
Light emitted by the light sources 13 enters the light guide plate 12 from the end faces 12a and 12b of the light guide plate 12. Among the light that has entered the light guide plate 12, light having an angle component equal to or greater than a critical angle propagates inside the light guide plate 12 while undergoing total refection. Light scattering elements (not shown) are formed on either one of two mutually facing principal surfaces 12c and 12d of the light guide plate 12. By means of these light scattering elements, it is possible to uniformly extract from the principal surface 12c (upper principal surface in
A reflective sheet 14 is arranged opposite the principal surface 12d (lower principal surface in
The heat spreader 15 is formed by a member with high heat dissipation (heat dissipation member) and has the role of dissipating heat emitted from the light sources 13. The heat spreader 15 is affixed to the chassis 11. The heat spreader 15 may be shared with external components of a liquid crystal display device incorporating the light source device 1, for example.
In addition, an optical sheet that regulates light emitted from the light guide plate 12 may be arranged on a light-exiting surface 12c of the light guide plate 12 in the light source device 1. As the optical sheet, a scattering sheet, prism sheet or the like can be used, for example, and the number and type of optical sheets may be appropriately set. One or a plurality of optical sheets (of the same or different types) may be used.
An example procedure for assembling the above-described light source device 1 is described below. First, the light guide plate 12 is secured in position on the chassis 11 using a positioning part (not shown). At this stage, the reflective sheet 14 is secured in position therewith. Also, before and after, or at the same time as, attaching the light guide plate 12 to the chassis 11, the substrate 131 on which a plurality of light sources 13 are mounted is affixed to the heat spreader 15 using a double-sided adhesive or the like, for example.
Next, the heat spreader 15 with the affixed substrate 131 is affixed to the chassis 11 after being positionally adjusted, while the protruding members 121 of the light guide plate 12 are pressed against a contact surface 131a (placement surface on which the light sources 13 are placed) of the substrate 131. The heat spreader 15 can be affixed to the chassis 11 using an adhesive agent, adhesive tape or the like, for example. As a result, the light source device 1 is obtained.
In the light source device 1 of the present embodiment, a clearance can be set between the light sources 13 and light guide plate 12 (end faces 12a and 12b of the light guide plate 12) by means of the protruding members 121 pressed against the contact surface 131a. For this reason, the clearance between the light sources 13 and light guide plate 12 at a first end face 12a side and second end face 12b side can be easily made uniform. For this reason, the above-described imbalance in brightness (see
In the light source device 1, clearance adjustment parts of the present invention are constituted by the protruding members 121 provided on the light guide plate 12, and the contact surface 131a of the substrate 131. For example, when a design value for clearance between the light sources 13 and light guide plate 12 is 1.3 mm, supposing a thickness of the light source 13 (LED) is 0.9 mm, then a height of the protruding members 121 will be 2.1 mm (=1.3 mm+0.9 mm).
If dimensional variation has occurred between each protruding member 121 (four in this embodiment), variation will arise in the above-described clearance. However, if dimensions of the protruding members 121 have been strictly controlled, for example, it is possible to curtail the possibility of the light source device 1 being deemed defective due to the above-described clearance being unsuitable after assembly. In this regard too, the light source device 1 of the present embodiment can be considered to be a configuration that readily suppresses the occurrence of uneven brightness resulting from component dimensional variation and assembly variation.
In the above description, the clearance adjustment parts are constituted by the protruding members 121 provided on the light guide plate 12, and the contact surface 131a of the substrate 131. However, this is only one example.
Next, a schematic configuration of a light source device according to Embodiment 2 of the present invention will be described. The description of the light source device of Embodiment 2 will omit features shared in Embodiment 1 and will focus on the differences from Embodiment 1. Also, components shared with Embodiment 1 will be described using the same reference characters.
The heat spreader 15 requires a screwing region 152 in order to be screwed to the chassis 11. For this reason, the heat spreader 15 differs from that of Embodiment 1 (substantially L-shaped in cross-section; see
As shown in
Here, when securing the heat spreader 15 to the chassis 11, the position of the heat spreader 15 is adjusted while placing protruding members 121 of a light guide plate 12 against a contact surface 131a of the substrate 131, so that clearance between a light source 13 and the light guide plate 12 attains a prescribed value. The assembly method requires room for adjustment of the position of the heat spreader 15 relative to the chassis 11 in a direction parallel to a direction of protrusion of the protruding members 12. For this reason, the through-holes 153 are described as elongated holes. The through-holes 153 should at least be of a length greater than the screw holes 111 along the direction of protrusion of the protruding members 121, and may be so-called unloaded holes or the like, for example.
A screw is an example of a fastener of the present invention; as a fastener, a rivet or the like may be used, for example, instead of a screw. Also, the screw hole 111 is an example of an engaging hole of the present invention, and the through-hole 153 is an example of a through-hole of the present invention. Further, the chassis 11 is an example of a securing member of the present invention.
In addition, the screw-fastening method for the heat spreader 15 adopted in the light source device 2 of Embodiment 2 may be used in the configurations of the first to third variations of Embodiment 1.
Next, a schematic configuration of the light source device according to Embodiment 3 of the present invention will be described. The description of the light source device of Embodiment 3 will omit those features shared with Embodiment 1 and will focus on the differences from Embodiment 1. Also, components shared with Embodiment 1 will be described using the same reference characters.
By providing protruding members 121 towards the center, improvement can be expected in the precision of the prescribed value of clearance between a light source 13 and the light guide plate 12. In particular, the application of this configuration may be beneficial if a light-exiting surface of the light source device is enlarged. It is preferable that the protruding members 121 provided towards the center in particular be of a size (of course, this excludes the size in the direction of protrusion) that is as small as possible. By doing so, the generation of parts with decreased luminance (dark spots) due to providing the protruding members 121 is readily suppressed.
A configuration providing protruding members other than at both of the ends parallel to a lengthwise direction of the light guide plate 12 may be applied to configurations of first to third variations of Embodiment 1 and/or the configuration of Embodiment 2.
Next, a configuration of a liquid crystal display device according to an embodiment of the present invention will be described.
In the description herein, the light source device 2 of Embodiment 2 is applied to the liquid crystal display device 4, but light source devices 1 and 3 of Embodiment 1 (including variations) and Embodiment 3 can similarly be applied to the liquid crystal display device.
In the liquid crystal panel 40, liquid crystal (not shown) is enclosed between a pair of glass substrates 41 and 42 facing each other with a gap therebetween. Also, the liquid crystal panel 40 includes polarizing plates 43 and 44 attached to each outer surface of the pair of glass substrates 41 and 42.
A plurality of switching elements, such as TFTs (Thin Film Transistors), and pixel electrodes connected to these switching elements are arranged in matrix form on the surface of a first glass substrate 41. Also, a plurality of scan signal lines and data signal lines (neither shown) that drive the plurality of switching elements are formed in a mutually intersecting manner on the first glass substrate 41. An opposite electrode and color filters (neither shown) are formed on a second glass substrate 42.
The light source device 2 functions as a backlight device that radiates light from a back surface of the liquid crystal panel 40. Light that has emerged from a light-exiting surface 12c after entering a light guide plate 12 by emission from a light source 13 passes through a plurality of optical sheets 60 arranged between the light guide plate 12 and liquid crystal panel 40 and then reaches the liquid crystal panel 40. The plurality of optical sheets 60 includes a diffusion sheet and a prism sheet, for example. In this embodiment the number of optical sheets 60 is three, but this number may be changed as appropriate.
Any of the light source devices 1 to 3 according to the above-described embodiments can be applied to the liquid crystal display device 4. As described above, light source devices 1 to 3 include clearance adjustment parts constituted by protruding members 121 and a contact surface 131a. For this reason, imbalance of brightness of light emerging from light source devices 1 to 3 is unlikely to occur. Furthermore, non-uniformity of display quality is unlikely to occur in the liquid crystal display device 4 that includes this kind of light source device 1 to 3.
<Other>
The embodiments presented above are only illustrative examples of the present invention. In other words, the scope of the present invention includes suitable variations of the above-described embodiments insofar as the scope of technical ideas of the present invention is not departed from.
The above-described embodiments are configured such that light sources 13 are respectively arranged opposite two mutually facing end faces 12a and 12b of the light guide plate 12. However, this does not mean that the scope of the present invention is limited to this configuration. In other words, the present invention can also be applied to a configuration in which light sources 13 are arranged at only one side of two mutually facing end faces 12a and 12b of a light guide plate 12.
Also, the present invention can be applied to cases where a light source 13 is constituted by a cold-cathode tube, or cases where, for example, a light guide plate 12 is wedge-shaped or the like, rather than flat.
Also, in the embodiments presented above, the light source device according to the present invention was configured to be applied to a liquid crystal display device. However, the scope of application of the light source device of the present invention is not limited to a liquid crystal display device. In other words, the light source device of the present invention is also naturally applicable to a display device constituted by a display panel that uses an electro-optical material other than liquid crystal as an optical switching material.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2012-205705 | Sep 2012 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2013/074820 | 9/13/2013 | WO | 00 |
