JP2020071980A - Light source device and image formation device - Google Patents

Abstract

To provide a light source device which enables reduction of the number of fastening members of a light source substrate while inhibiting increase of contact thermal resistance between the light source substrate and a heat radiation member.SOLUTION: A light source device of the invention has a light source substrate and a heat radiation member disposed on a rear surface of the light source substrate. The light source substrate is fastened to the heat radiation member, and the heat radiation member has an arch shape at the side of a contact surface contacting with the side of the light source substrate. Providing the arch shape in the heat radiation plate causes the light source substrate and the heat radiation plate to be fixed while pressed each other to inhibit a gap from occurring between the light source substrate and the heat radiation plate and reduce the number of fastening members of the light source substrate.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a light source device and an image display device.

  In the liquid crystal display device, a liquid crystal display panel for displaying an image and a backlight device are arranged on the back surface thereof. Conventionally, a cold cathode fluorescent tube has been used as a light source of a backlight device, but in recent years, a backlight device using an emitting diode (LED) as a light source has become mainstream, and in a liquid crystal display device using this. High definition, high brightness, and high contrast are being promoted.

  In the case of high definition, that is, when the display pixel pitch of the liquid crystal panel is reduced, the transmittance of light passing through the liquid crystal panel generally decreases. In order to obtain a display image with high brightness using such a liquid crystal panel, it is necessary to increase the emission brightness from the light source device.

  Further, in the case of increasing the contrast, by utilizing the fact that the LED is a point light source, the brightness of the backlight device is partially changed by individually controlling the light emission brightness of the LED, thereby increasing the contrast of the display image. Enhancing techniques are used. Such control of light emission brightness is generally called local dimming control. In the local dimming control, a process of analyzing the brightness value of the image signal for each of the plurality of divided regions forming the screen region and controlling the emission brightness of the corresponding light source based on the analysis result of the brightness value is performed. Usually, a process of increasing the light emission brightness of the light source in the area corresponding to the bright part of the image signal and decreasing the light emission brightness of the light source in the dark part is performed. When such local dimming control is used, in order to obtain a display image with high brightness in the bright part of the image signal, it is necessary to increase the light emission brightness from the light source device.

  As described above, the light emission brightness of the light source device tends to increase, and along with this, the amount of heat generated by the light source device also increases. When the temperature of the LED, which is a light source, becomes high, the luminous efficiency may decrease, or the resin package or the sealing agent that constitutes the LED element may deteriorate, resulting in failure. Need to do.

  Conventionally, in order to efficiently dissipate heat generated from a large number of LEDs, a heat dissipation plate is attached to a light source substrate, and heat is dissipated to air via the heat dissipation plate.

  Patent Document 1 discloses a technique in which a heat dissipation plate is attached to the back surface of a light source substrate, a heat sink and a heat pipe are further attached to the heat dissipation plate, and air is blown by a cooling fan. Further, Patent Document 2 discloses a technique of attaching a heat dissipation plate to the front surface of a light source substrate.

  In such a configuration, when the light source board has a warp or when the light source board and the heat dissipation plate use materials having different thermal expansion coefficients, a gap is left between the light source board and the heat dissipation plate. Sometimes. This gap hinders heat transfer to the heat radiating plate and reduces heat radiating efficiency. In order to prevent this, generally, a large number of mounting holes are provided in the light source substrate, and a large number of screws are fixed to the heat dissipation plate.

  Further, in Patent Document 3, a heat radiating plate is attached to the back surface of the light source substrate, and the light source substrate is pressed against the heat radiating plate by a reflection plate attached to the front surface of the light source substrate. A technique for suppressing the gap is disclosed.

  As described above, conventionally, there is a problem that the contact heat resistance with the heat dissipation member increases due to the formation of the gap between the light source substrate and the heat dissipation plate. In order to suppress this, fastening and fixing using many members had to be performed.

JP, 2005-316337, A JP, 2008-129464, A JP, 2009-129705, A

  It is an object of the present invention to provide a light source device capable of suppressing an increase in contact thermal resistance between a light source substrate and a heat dissipation member and reducing the number of fastening members of the light source substrate.

In order to achieve the above object, the light source device according to the present invention,
It has a light source substrate and a heat dissipation member arranged on the back surface of the light source substrate, the light source substrate is fastened and fixed to the heat dissipation member, and the heat dissipation member has an arch shape on the contact surface side with the light source substrate side. It is characterized by

  According to the light source device of the present invention, by providing the heat radiation plate with the arch shape, the light source substrate and the heat radiation plate are fixed in a state of being pressed against each other, so that a gap is generated between the light source substrate and the heat radiation plate. Can be suppressed, and the number of fastening members of the light source board can be reduced.

Exploded perspective view schematically showing the image display device according to the first embodiment. Light source substrate front view of the image display device according to the first embodiment AA 'sectional view of the image display device according to the first embodiment FIG. 3 is a diagram showing another example of the configuration of the image display device according to the first embodiment. Light source substrate front view of the image display device according to the second embodiment BB 'cross-sectional view of the image display device according to the second embodiment FIG. 6 is a diagram showing another example of the configuration of the image display device according to the second embodiment.

  Hereinafter, modes for carrying out the present invention will be described with reference to the drawings.

(Embodiment 1)
A first embodiment according to the present invention will be described.

  FIG. 1 is an exploded perspective view schematically showing the entire image display device 1 according to this embodiment.

  The image display device 1 includes a frame 10, a liquid crystal display panel 20, a panel holder 30, an optical sheet 40, a reflection sheet 50, a light source substrate 60, and a case 70.

  The frame 10 covers the liquid crystal display panel 20 from the front side and has an opening that exposes an image display area portion of the liquid crystal display panel 20. The frame 10 is often made of metal and is formed by pressing or machining, but it may be formed by resin molding.

  The panel holder 30 covers the liquid crystal display panel 20 from the back side and holds the liquid crystal display panel 20 by sandwiching it with the frame 10. The panel holder 30 is provided with an opening for passing light from the light source substrate 60 arranged on the back side to the image display area of the liquid crystal display panel 20. The panel holder 30 is preferably resin-molded, but may be made of a metal material.

  The optical sheet 40 is arranged between the panel holder 30 and the light source substrate 60, and diffuses and condenses when the light from the light source substrate 60 is transmitted. The optical sheet 40 is configured by laminating a plurality of light-transmissive sheets, and the sheet has a property of diffusing light or a property of having unevenness on the surface and condensing light. The thing etc. can be used.

  The reflection sheet 50 covers the surface of the light source substrate 60 on the liquid crystal display panel 20 side, and reflects the light emitted from the light source substrate 60 toward the liquid crystal display panel 20. A plurality of openings 51 are formed in the reflection sheet 50, and a plurality of light source groups 61 provided on the light source substrate 60 are exposed in the openings 51. Further, a wall portion formed by bending toward the liquid crystal display panel 20 side is provided at an end portion of the reflection sheet 50. It is desirable to use a sheet material having a high reflectance as the reflection sheet 50, and a white foamed PET sheet or a metal thin plate having a high reflection film applied on its surface can be used.

  A plurality of LEDs 61 are mounted on the light source board 60 as a light source. The LEDs 61 are arranged on the light source substrate 60 in a grid pattern at predetermined intervals.

  The case 70 covers the light source board 60 from the back side, and the reflection sheet 50 and the light source board 60 are housed inside the wall part provided around the case. The case 70 is composed of a plurality of members, and is a heat dissipation plate 71 that is a part to which the light source board is attached, and a peripheral wall member that is attached to the periphery of the heat dissipation plate 71 and extends toward the liquid crystal display panel 20 side. Composed of and. A metal is often used for the heat dissipation plate 71, and in particular, an aluminum alloy having high heat conductivity is often used. The heat dissipation plate 71 can be formed by sheet metal pressing or machining.

  The case 70, the reflection sheet 50, and the light source substrate 60 are fixed by screws (not shown) and rivets (not shown). The case 70 and the panel holder 30 are fixed by engagement means such as screws and claw fitting, and are integrated with the optical sheet 40, the reflection sheet 50, and the light source substrate 60 to form a backlight device 80. Further, the backlight device 80 and the frame 10 are fixed to form the image display device 1. The image display device 1 also includes an electric board (not shown) for driving and controlling the liquid crystal display panel 20 and the light source board 60.

  2 and 3 are schematic front views and a cross section taken along the line AA ′ before the light source substrate of the image display device according to the first embodiment is attached to the case 70. In these figures, for the sake of explanation, the reflection sheet 50 and the peripheral wall member of the case 70 are not shown, and the warp of the light source substrate 60 and the arch shape of the heat dissipation plate 71, which will be described later, are exaggerated.

  The light source board 60 is composed of a rectangular wiring board and a plurality of LEDs 61 mounted on the surface thereof. The wiring board is formed by laminating a glass epoxy base material, copper wiring, and prepreg in multiple layers. In this embodiment, the wiring board has a size of 380 mm × 220 mm and a thickness of 1 mm. Further, the light source board 60 is provided with a plurality of positioning holes 62 and 63 used for positioning when attaching to the heat dissipation plate 71, and a plurality of holes 64 through which a screw is inserted at the time of screw fastening. The positioning holes 62 and 63 are arranged along the central portion of the long side of the light source substrate 60 and along the short side direction. The holes 64 are arranged along both short sides of the light source substrate 60.

  The light source substrate 60 has a warp having a center of a circle of curvature on the mounting surface side of the LED 61. This warp is caused by a combination of a warp caused by stacking a plurality of wiring substrates and a warp caused by a heating process in a reflow process when mounting the LED 61. In this embodiment, the light source substrate 60 has a warp of about 1 mm along the longitudinal direction.

  Although it is necessary to increase the total thickness of the wiring board in order to reduce the warp of the light source board 60, it is preferable to be thin in order to efficiently transfer heat from the LED 61 to the heat dissipation plate 71.

  The heat dissipation plate 71 is a rectangular aluminum alloy plate. In this embodiment, the size is 390 mm × 230 mm and the thickness is 2 mm. Positioning pins 73 for mounting the light source substrate 60 are attached to the heat radiating plate 71 so as to be convex toward the light source substrate 60 side by about 2 mm.

  Further, the heat dissipation plate 71 is provided with a plurality of screw holes 74 for fixing the light source substrate 60 by screw fastening. Further, screw holes (not shown) for attaching the peripheral wall member as described above are provided.

  The heat dissipation plate 71 has an arch shape having a center of a circle of curvature on the side opposite to the light source substrate 60. This arch shape is given in advance by press molding when the heat dissipation plate 71 is manufactured, and has a warp of about 1 mm in this embodiment. The positioning pin 73 is arranged on this arch-shaped convex portion.

  When assembling the light source board 60 to the heat dissipation plate 71, first, the positioning pins 73 of the heat dissipation plate 71 are inserted into the positioning holes 62 and 63 of the light source board 60 to relatively position the light source board 60 and the heat dissipation plate 71. Next, from the light source substrate 60 side, the screw 72 is fastened to the screw hole 74 at the hole 64 portion. The light source board 60 is elastically deformed along the arch shape of the heat radiating plate 71 and fixed to the heat radiating plate 71 by screwing. At this time, the heat dissipation plate 71 is elastically deformed along the light source substrate 60 side. Due to this elastic deformation, the light source substrate 60 and the heat dissipation plate 71 are pressed against each other, so that the gap amount is reduced.

  Before the screw 72 is completely fastened, the warp of the light source board 60 and the arch shape of the heat dissipation plate 71 cause the positioning pin 73 to separate the light source board 60 from the heat dissipation plate 71. Also in this case, the positioning pin 73 is provided with a sufficient length so that the positioning pin 73 is inserted into the positioning holes 62 and 63, so that the positional deviation between the light source substrate 60 and the heat dissipation plate 71 does not occur. be able to.

  Although the light source substrate 60 is warped toward the mounting surface side of the LED 61 and the heat dissipation plate 71 has a convex arch shape toward the light source substrate 60 side in this embodiment, the present invention is not limited to this.

  As shown in FIG. 4A, the light source substrate 60 has a warp having the center of the circle of curvature on the mounting surface side of the LED 61, and the heat dissipation plate 71 has the center of the circle of curvature on the side of the light source substrate 60. The shape may have an arch shape. At this time, the arch-shaped curve R of the heat dissipation plate 71 is made larger than the curve R of the warp of the light source board 60, so that the light source board 60 and the heat dissipation plate 71 are pressed against each other to reduce the gap amount.

  As shown in FIG. 4B, the light source board 60 has a warp having the center of a curvature circle on the side opposite to the mounting surface of the LED 61, and the heat dissipation plate 71 has a curvature circle on the side opposite to the light source board 60. The shape may have an arch shape having a center. At this time, the arch-shaped bend R of the heat dissipation plate 71 is made smaller than the bend R of the light source substrate 60, so that the light source substrate 60 and the heat dissipation plate 71 are pressed against each other to reduce the amount of gap.

  The wiring substrate of the light source substrate 60 is not limited to the glass epoxy base material, and any base material may be used as long as it has flexibility. Further, the thickness of the wiring board is not limited to 1.0 mm, and may be appropriately used as long as it can be deformed by flexibility when being fastened to the heat dissipation plate 71.

  It suffices that the heat dissipation plate 71 has an arch shape on the side facing the light source substrate 60, and the surface opposite to the light source substrate 60 does not have to have the arch shape. For example, the heat dissipation plate 71 having an arch shape on the light source substrate 60 side and a flat surface on the opposite side can be easily manufactured by extrusion molding. Further, the material and thickness of the heat dissipation plate 71 may not be flexible as long as the gap can be reduced when the light source substrate 60 is fixed.

  As the arch shape, the shape along the longitudinal direction of the light source substrate 60 is described, but the shape is not limited to this, and the arch shape may be formed in the short side direction.

  Further, an insulating sheet or a heat conductive sheet may be sandwiched between the heat dissipation plate 71 and the light source substrate 60.

  As described above, according to the present embodiment, by providing the heat dissipation plate 71 with the arch shape, even if the light source substrate 60 is warped, the light source substrate 60 and the light source substrate 60 can be used without using a large number of fastening members. The heat radiating plate 71 is fixed while being pressed against each other. As a result, it is possible to suppress the formation of a gap between the light source substrate and the heat dissipation plate.

(Embodiment 2)
A second embodiment according to the present invention will be described below with reference to the drawings.

  The description of the same parts as those in the first embodiment will be omitted.

  5 and 6 are schematic front views and a cross section taken along the line AA ′ before the light source substrate 60 ′ of the image display device according to the second embodiment is attached to the case 70. In these figures, for the sake of explanation, the reflection sheet 50 and the peripheral wall member of the case 70 are not shown, and the warp of the light source substrate 60 ′ and the arch shape of the heat dissipation plate 71 ′ which will be described later are exaggerated. ..

  The light source board 60 'is composed of a rectangular wiring board and a plurality of LEDs 61 mounted on the surface thereof. The wiring board has a size of 380 mm × 220 mm and a thickness of 1 mm. Further, the light source board 60 'is provided with a plurality of positioning holes 62' and 63 'used for positioning at the time of attachment to the heat dissipation plate 71', and a plurality of holes 64 'through which screws are inserted at the time of screw fastening. The positioning holes 62 'and 63' are arranged along the long side direction of the light source substrate 60 'in the central portion of the short side. The hole 64 'is arranged along the central portion and the short side of the long side of the light source substrate 60'.

The light source substrate 60 ′ has a warp having a center of a circle of curvature on the mounting surface side of the LED 61. In this embodiment, the light source substrate 60 'has a warp of about 1 mm along the longitudinal direction.
The heat dissipation plate 71 'is a rectangular aluminum alloy plate. In this embodiment, the size is 390 mm × 230 mm and the thickness is 2 mm. Positioning pins 73 'for mounting the light source board 60' are assembled to the heat dissipation plate 71 'so that the projections 73' project toward the light source board 60 'by about 2 mm.

  The heat dissipation plate 71 'has an arch shape having a center of a circle of curvature on the light source substrate 60' side. This arch shape is given in advance by press molding when the heat dissipation plate 71 'is manufactured, and has a warp of about 1 mm in this embodiment. The positioning pin 73 'is arranged on this arch-shaped convex portion.

  When assembling the light source board 60 ′ to the heat dissipation plate 71 ′, first, the positioning pins 73 ′ of the heat dissipation plate 71 ′ are inserted into the positioning holes 62 ′ and 63 ′ of the light source board 60 ′, and the light source board 60 ′ and the heat dissipation plate 71 ′. Relative positioning of. Then, from the side of the light source substrate 60 ', the screw 72 is fastened to the screw hole 74' at the hole 64 '. The light source board 60 'is fixed to the heat dissipation plate 71' by being screwed by being elastically deformed along the arch shape of the heat dissipation plate 71 '. At this time, the heat dissipation plate 71 'is elastically deformed along the light source substrate 60'. By this elastic deformation, the light source substrate 60 'and the heat dissipation plate 71' are pressed against each other, and the amount of the gap is reduced.

  In this embodiment, the light source substrate 60 ′ is curved toward the mounting surface of the LED 61, and the heat dissipation plate 71 ′ is arched toward the light source substrate 60 ′. However, the configuration is not limited to this.

  As shown in FIG. 7A, the light source board 60 ′ has a warp having the center of a circle of curvature on the side opposite to the mounting surface of the LED 61, and the heat dissipation plate 71 ′ has a circle of curvature on the side of the light source board 60 ′. It may have a shape having an arch shape having the center of.

  As shown in FIG. 7B, the light source board 60 ′ has a warp having the center of a curvature circle on the side opposite to the mounting surface of the LED 61, and the heat dissipation plate 71 ′ is on the side opposite to the light source board 60 ′. The shape may have an arch shape having the center of the circle of curvature. At this time, the arch-shaped curve R of the heat dissipation plate 71 ′ is made larger than the curve R of the warp of the light source board 60 ′, so that the light source board 60 ′ and the heat dissipation plate 71 ′ are pressed against each other to reduce the gap amount. ..

  The arch shape has been described as a shape along the longitudinal direction of the light source substrate 60 ', but the shape is not limited to this, and an arch shape may be formed in the short side direction.

  As described above, according to the present embodiment, by providing the heat dissipation plate 71 ′ with the arch shape, even if the light source substrate 60 ′ is warped, the light source substrate is not used with a large number of fastening members. 60 'and the heat dissipation plate 71' are fixed in a state of being pressed against each other. As a result, it is possible to suppress the formation of a gap between the light source substrate and the heat dissipation plate.

1 image display device 10 frame, 20 display panel, 30 panel holder,
40 optical sheet, 50 reflective sheet, 51 opening,
60 light source board, 61 LED, 70 case, 71 heat dissipation plate,
72 screws, 80 backlight device

Claims (6)

A light source board, and a heat dissipation member arranged on the back surface of the light source board,
The light source board is fastened and fixed to the heat dissipation member,
The heat dissipation member has an arch shape on the contact surface side with the light source substrate side.   The light source device according to claim 1, wherein the arch shape is formed along a longitudinal direction of the light source substrate.   The light source device according to claim 1, wherein the arch shape is formed at each of fastening and fixing intervals. The light source board is fastened and fixed at the arch-shaped peripheral portion of the heat dissipation member,
The arch shape is such that, when the center of the curvature circle of the warp of the light source board is on the light source element mounting side of the light source board, the center of the curvature circle of the heat dissipation member is on the light source board side and is larger than the radius of curvature of the light source board, Alternatively, the center of the curvature circle of the heat dissipation member is on the side opposite to the light source substrate, and the light source device according to claim 2 or 3. The light source board is fastened and fixed at the arch-shaped peripheral portion of the heat dissipation member,
When the center of the curvature circle of the warp of the light source board is opposite to the light source element mounting side of the light source board, the arch shape is such that the center of the curvature circle of the heat dissipation member is opposite to the light source board side and The light source device according to claim 2, wherein the light source device has a smaller radius of curvature. The light source board is fastened and fixed at the arch-shaped central portion of the heat dissipation member,
The arch shape is such that, when the center of the curvature circle of the warp of the light source substrate is on the light source element mounting side of the light source substrate, the center of the curvature circle of the heat dissipation member is on the light source substrate side and smaller than the radius of curvature of the light source substrate, When the center of the curvature circle of the warp of the light source board is opposite to the light source element mounting side of the light source board, the center of the curvature circle of the heat dissipation member is on the light source board side, or the center of the curvature circle of the heat dissipation member is the light source board The light source device according to claim 2 or 3, wherein the light source device is on the opposite surface side to and is larger than the radius of curvature of the light source substrate.