JP4912844B2 - LIGHT EMITTING DEVICE AND DISPLAY DEVICE USING THE SAME - Google Patents

Description

  The present invention relates to various light emitting devices typified by a backlight device such as a liquid crystal display device, and a display device using the light emitting device.

  In recent years, for example, in a display device such as a liquid crystal display device typified by a liquid crystal television or a liquid crystal monitor, a backlight is employed as a light emitting device in order to irradiate light from the back surface or the side surface of the display panel. As this backlight, for example, there is a so-called direct type in which a light source is arranged on a plane directly under (back) a liquid crystal panel. In addition, a light source is installed only on two sides or one side of a transparent resin light guide plate, and the light incident on the light guide plate is reflected by a reflecting portion provided on the back surface of the light guide plate to irradiate, for example, a liquid crystal panel surface. There is an edge light type. Here, the direct type is excellent in that high luminance can be secured, but it is disadvantageous for making the backlight thinner. In addition, the edge light type is superior in that it can be made thinner than the direct type, but is disadvantageous in terms of uniform luminance for large screens.

  As such a backlight device, a fluorescent tube of a hot cathode type or a cold cathode type is widely used. On the other hand, as an alternative to the backlight device using such a fluorescent tube, in recent years, technological development of a backlight device using a light emitting diode (LED), which is one of solid light emitting elements, as a light source. Is underway.

  When this LED is used, for example, a backlight used for a small display such as a liquid crystal display for a mobile phone, it is possible to ensure high luminance with low power consumption. Conventionally, the backlight for liquid crystal using this LED has been applied to a liquid crystal display for a small mobile phone as described above. However, in recent years, the range of application has expanded, and the liquid crystal display for car navigation has been used for a large screen television (TV). ). In particular, when a backlight of a large-screen liquid crystal TV is configured using three color LEDs corresponding to the three primary colors of red, blue, and green, the color reproduction range can be widened, so that high image quality can be realized. It is also attracting attention.

  In the case of backlights for large-screen LCD TVs, a large number of LED chips must be arranged directly underneath because a large amount of light is required, but the LED's luminous efficiency (electrical energy ⇒ conversion efficiency to light energy) is currently However, since it is still 50% or less, the majority of the input energy becomes heat. This leads to an increase in the junction temperature of the LED light source (chip), which further reduces the light emission efficiency and shortens the life of the LED. That is, the LED light source has lower utilization efficiency (lm / w) due to heat generation, and the reflectance and transmission due to deterioration of resin members such as die bond agent, sealant, light source package, and light guide plate disposed in the vicinity of the chip. Since the rate is reduced and the emission intensity is reduced, the heat draw (heat dissipation) property greatly affects the performance of the LED light source.

  Here, as a prior art described in the publication, in order to efficiently dissipate heat generated from a large number of light emitting diodes and to make temperature distribution uniform over the entire surface, a heat dissipating plate is attached to the back panel. There is a heat pipe and a heat sink attached to a plate and a cooling fan assembled to the heat sink (see, for example, Patent Document 1).

JP 2005-316337 A

  FIGS. 4A and 4B are views showing an example of a mounting structure of a mounting board that has been conventionally employed. A mounting substrate 200 shown in FIGS. 4A and 4B includes an insulating layer 201 and a take-out electrode (wiring circuit) 202 formed on the insulating layer 201. An LED 203 is disposed on the mounting substrate 200, and the LED 203 is connected to the extraction electrode 202 on the insulating layer 201 by a wire 204. In addition, the mounting substrate 200 includes a metal pattern 206 that forms a heat dissipation path on a surface (second surface, back surface) opposite to a surface (first surface, front surface) on which the LEDs 203 are disposed. In addition, a path 207 such as a through hole or a bump connecting the first surface and the second surface directly below the LED 203 is formed on the mounting substrate 200. This path 207 is connected to the metal pattern 206 and transfers heat generated by the LED 203 to the metal pattern 206.

  Then, as shown in FIG. 4B, the mounting substrate 200 to which the LED 203 as shown in FIG. 4A is attached is attached to the housing 210. At this time, a thermal sheet 211 that is a sheet having high thermal conductivity is provided between the metal pattern 206 provided on the second surface of the mounting substrate 200 and the housing 210. With the above structure, heat generated from the chip of the LED 203 is released to the outside. In some cases, a thermal layer 211 or a heat radiation layer such as heat radiation grease is not provided.

  However, in the conventional technique as shown in FIG. 4, for example, it is necessary to create a path 207 for releasing heat from the LED 203 between the front surface and the back surface of the mounting substrate 200, which increases the cost for generating the substrate. . In addition, since it is necessary to provide the metal pattern 206 on the back surface, the back surface of the insulating layer 201 is limited, and the selection of the substrate is restricted.

  The present invention has been made in order to solve the technical problems as described above. The object of the present invention is to provide a light emitting device using a solid light emitting element such as an LED, and to reduce the product unit price and manufacturing cost. The object is to achieve good heat dissipation without increasing.

  In order to achieve such an object, the present invention is a display device that includes a display panel that displays an image and a backlight that irradiates the display panel from the back, and the backlight includes a solid-state light emitting element. A mounting substrate, a first surface facing the display panel, and a second surface serving as a back surface of the first surface, and a frame for mounting the mounting substrate from the second surface side are provided.

  Here, the mounting substrate of the backlight includes a plurality of solid light emitting elements, the frame of the backlight includes a plurality of through holes, and the plurality of solid light emitting elements provided on the mounting substrate are connected to the plurality of through holes. If the mounting board is attached from the second surface side according to the position, and the solid light emitting element is arranged toward the display panel, the light emitted from the solid light emitting element is provided to the display panel satisfactorily. it can. The shape of the “through hole” can be arbitrarily selected from a circle, an ellipse, a polygon such as a triangle and a quadrangle. In addition, as the hole cross section of the “through hole”, a straight shape having no inclination, an inclined shape that is inclined with respect to the surface of the mounting substrate, or the like can be selected.

In addition, the backlight mounting board may include a heat transfer unit that is provided on the same surface as the solid light-emitting element and transmits heat generated by the solid light-emitting element. For example, a copper exposed region corresponds to the heat transfer unit.
Further, the backlight is provided with a heat conduction means that is provided between the mounting board and the frame and transfers heat generated from the solid light emitting element of the mounting board to the frame, so that the heat can be better. It is excellent in that it can be transmitted.
Furthermore, the mounting substrate of the backlight includes a wiring circuit provided on the solid light emitting element side and connected to the solid light emitting element, a heat dissipation circuit connected to the solid light emitting element, and an insulating layer covering the wiring circuit and the heat dissipation circuit. It can be characterized by comprising.

  From another point of view, the light emitting device to which the present invention is applied includes a mounting substrate including a solid light emitting element, a first surface that provides light from the solid light emitting element, and a back surface that is the back surface of the first surface. And a frame to which the mounting board is attached from the second surface side.

  This frame includes a through-hole, and a solid-state light emitting device provided on the mounting board is aligned with the position of the through-hole, and the mounting board is attached from the second surface side. The mounting board includes a plurality of solid state light emitting elements arranged at regular intervals, and the frame includes a plurality of through holes.

  Furthermore, it is possible to provide heat conduction means that is provided between the second surface side of the frame and the mounting substrate, and transfers heat generated from the solid light emitting elements of the mounting substrate to the frame.

The mounting board includes a wiring circuit provided on the solid light emitting element side and connected to the solid light emitting element, and an insulating layer covering the wiring circuit, and the surface including the insulating layer is opposed to the second surface of the frame. It can be characterized by making it.
Further, the mounting substrate is provided with a wiring circuit on a surface which is a back surface with respect to the surface on which the solid light emitting element is disposed, and the solid light emitting element and the wiring circuit are connected to each other, and the solid light emitting element is disposed. The surface may be opposed to the second surface of the frame.

  According to the present invention configured as described above, good heat dissipation can be realized in a light-emitting device using a solid light-emitting element such as an LED without increasing the product unit price or manufacturing cost.

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
FIG. 1 is a diagram showing an overall configuration of a liquid crystal display device to which the present embodiment is applied. The liquid crystal display device to which the present embodiment is applied is a large module, a direct-type backlight device (backlight) 10 which is one of light emitting devices, and a liquid crystal display irradiated from the back by the backlight device 10. Module 30. The backlight device 10 includes a backlight frame 11 that houses a light emitting unit, and a mounting substrate 12 that is a substrate on which a plurality of light emitting diodes (LEDs) that are one of solid light emitting elements are arranged as a light emitting source. ing. In addition, the backlight device 10 has a diffusion plate 13 that is a transparent plate that scatters and diffuses light in order to make the entire surface uniform brightness as a laminated body of optical films, and has a forward focusing effect. Prism sheets 14 and 15. In some cases, a diffusion film is further placed on the diffusion plate 13. Further, a diffusion / reflection type brightness enhancement film 16 for improving brightness is provided.

  On the other hand, as a liquid crystal display module 30, a liquid crystal panel 31 in which liquid crystal is sandwiched between two glass substrates, and a polarization layer that is laminated on each glass substrate of the liquid crystal panel 31 to limit light wave vibration in a certain direction. Plates (polarizing filters) 32 and 33 are provided. Further, peripheral members such as a driving LSI (not shown) are arranged in the liquid crystal display device.

The liquid crystal panel 31 includes various components not shown. For example, two glass substrates are provided with a display electrode (not shown), an active element such as a thin film transistor (TFT), a liquid crystal, a spacer, a sealant, an alignment film, a common electrode, a protective film, a color filter, and the like. .
Note that the structural unit of the backlight device 10 is arbitrarily selected. For example, a distribution form in which only a backlight frame 11 having a mounting substrate 12 is called a “backlight device (backlight)” and does not include a laminated body of optical films such as a diffusion plate 13 and prism sheets 14 and 15 is also possible. possible.

  The present embodiment is characterized in that the mounting substrate 12 is attached from the back side of the backlight frame 11 (the side opposite to the side facing the liquid crystal display module 30). That is, when the surface of the backlight frame 11 facing the liquid crystal display module 30 is the first surface, the LED arrangement surface of the mounting substrate 12 is made to correspond to the second surface which is the back surface of the first surface. Is attached.

  FIG. 2 is a view for explaining the structure of the mounting portion of the mounting substrate 12 in the backlight device 10 which is a light emitting device. In the example shown in FIG. 2, a direct type backlight structure in which a light source is placed directly under the back surface of the liquid crystal display module 30 is employed. In this backlight structure, a predetermined interval is provided with respect to the entire back surface of the liquid crystal display module 30. A plurality of LED chips are arranged.

  The backlight frame 11 forms a housing structure made of, for example, aluminum, magnesium, iron, or a metal alloy containing them. And the polyester film etc. which have the performance of white high reflection, for example are stuck inside the housing structure, and the white paint containing the filler represented by titanium oxide etc. is painted, and it has a function as a reflector. The casing structure includes an LED arrangement portion 11a provided corresponding to the size of the liquid crystal display module 30, and side portions 11b surrounding the four corners of the LED arrangement portion 11a. In addition, a heat sink structure (not shown) including cooling fins for exhaust heat may be formed on the LED arrangement portion 11a and the side surface portion 11b as necessary.

  In the example shown in FIG. 2, a plurality of mounting boards 12 (eight in the example of FIG. 2) are provided, and these mounting boards 12 are each provided with a plurality of screws (not shown) in the LED arrangement portion of the backlight frame 11. It is fixed from the back side (second surface side) of 11a. The LED placement portion 11 a is formed with a through hole 11 c which is a notch corresponding to the position of the light emitting diode (LED) 21 placed on the mounting substrate 12. With each light emitting diode (LED) 21 protruding from the through hole 11c, the mounting substrate 12 is attached from the back side of the LED placement portion 11a. As the shape of the through hole 11c, for example, a circle, an ellipse, a polygon such as a triangle or a square can be selected. Moreover, the hole cross section of the through-hole 11c can be made straight with or without taper.

  FIGS. 3A and 3B are explanatory views showing each element formed on the mounting substrate 12. FIG. 3A is a plan view of a part of the mounting substrate 12, and FIG. 3B is a back surface (second surface) of the LED placement portion 11a in the backlight frame 11, and FIG. The partial cross section at the time of mounting such a mounting substrate 12 is shown. As shown in FIG. 3A, a light emitting diode (LED) 21 is attached to the surface of the mounting substrate 12. A wiring circuit 22 for supplying a driving current to the light emitting diode (LED) 21 is provided on the surface of the mounting substrate 12.

  The wiring circuit 22 is made of, for example, copper or a copper-based metal material, and light emitting diodes (LEDs) 21 attached to the mounting substrate 12 are electrically connected to the wiring circuit 22 via wires 23, respectively. Yes. That is, the (+) pole and the (−) pole of the light emitting diode (LED) 21 are connected to the wiring circuit 22 by wire bonding. In addition, an insulating layer 24 such as a resist is provided at a portion where the wiring circuit 22 is formed so as to correspond to a portion of the backlight frame 11 facing the LED placement portion 11a. An electrical short circuit with the frame 11 is prevented.

  Further, the mounting substrate 12 to which the present embodiment is applied has a metal film region 25 (a region indicated by hatching in the drawing) serving as a heat transfer unit for heat dissipation on the surface on which the wiring circuit 22 is formed. Yes. The metal film region 25 is generated from, for example, a metal (for example, copper) of the same material as the wiring circuit 22 and is designed so that the area can be as wide as possible at a position avoiding the light emitting diode (LED) 21 and the wiring circuit 22. It is provided in the state. Thus, by taking a larger area, the heat dissipation effect with respect to the heat | fever emitted from the light emitting diode (LED) 21 can be heightened more.

  Further, the metal film region 25 is generated by the same process as the generation of the wiring circuit 22. For example, as a method of manufacturing the mounting substrate 12, a method of etching unnecessary conductor portions is widely used. In this method, a resist is first applied on a copper-clad laminate, and a wiring is formed using the resist. The circuit 22 and the metal film region 25 are masked. Thereafter, etching is performed through baking, exposure, and development, and the resist is removed, whereby the wiring circuit 22 and the metal film region 25 are formed on the mounting substrate 12. The metal film region 25 thus formed is a portion that has been removed by etching when the wiring circuit 22 is generated. Therefore, a special increase in cost due to the newly formed metal film region 25 does not occur.

  The mounting substrate 12 having such a metal film region 25 is attached to the back surface of the LED placement portion 11a of the backlight frame 11 as shown in FIG. That is, the LED arrangement portion 11a includes a first surface facing the display panel side (the liquid crystal display module 30 side) and a second surface serving as a back surface of the first surface, and is mounted from the second surface side. A substrate 12 is attached. In this attachment, as described above, the light-emitting diode (LED) 21 is aligned with the through hole 11c, and the mounting board is further sandwiched with the thermal sheet 26 as the heat conducting means on the second surface side of the LED arrangement portion 11a. 12 is attached. In addition, as shown in FIG. 3B, this attachment is fixed to the LED placement portion 11a with screws 27 from the back side, for example. It should be noted that other layers can be used instead of the thermal sheet 26 as long as a thicker layer than the insulating layer 24 shown in FIG. For example, grease or a metal thin film can be used.

  Here, since the mounting substrate 12 is a single-sided or double-sided substrate in which a wiring circuit 22 such as a metal film is formed on a resin, since the thermal conductivity is generally extremely low as compared with a metal material, the light-emitting diode (LED) 21 The generated heat tends to accumulate on the mounting substrate 12. Therefore, if no heat dissipation measures are taken, the temperature rise of the light emitting diode (LED) 21 becomes severe, the light emitting efficiency of the light emitting diode (LED) 21 decreases, and the light emitting diode (LED) 21 is disposed in the vicinity. Deterioration of resin members such as die bond agents, sealing agents, light source packages, and light guide plates causes problems such as a decrease in reflectance and transmittance and a decrease in light emission intensity. In the present embodiment, a metal film region 25 that is a heat transfer film is provided in the vicinity of the light emitting diode (LED) 21, thereby enhancing the heat dissipation effect to the outside, and the heat absorbed by the metal film region 25 is thermally transferred. It escapes directly to the backlight frame 11 via the seat 26.

  As described above in detail, according to the present embodiment, since it is not necessary to create a heat sink path between the upper and lower sides of the mounting board 12, it is not necessary to employ a double-sided board, and the mounting board 12 is a single-sided board. Can be formed. As a result, the cost can be greatly reduced. Moreover, since there is no restriction | limiting of a back surface in the mounting board | substrate 12, it becomes possible to employ | adopt the thing based on a glass cloth base-material epoxy resin (glass epoxy resin), for example, and a metal base. Furthermore, since the mounting substrate 12 is attached from the back surface (second surface) of the backlight frame 11, unevenness on the surface (first surface) of the backlight frame 11 can be reduced. As a result, for example, a reflection sheet or the like can be easily applied to the surface (first surface) of the backlight frame 11 or a white paint containing a filler typified by titanium can be easily applied. Layer formation is simplified.

  In the example described above (shown in FIG. 3), the wiring circuit 22 that supplies the drive current to the light emitting diode (LED) 21 is provided on the surface of the mounting substrate 12 to which the light emitting diode (LED) 21 is attached. However, although there is a disadvantage in reducing the cost, a wiring circuit may be provided on the back surface to which the light emitting diode (LED) 21 is not attached. In such a case, a metal film region 25 using, for example, copper is exposed on the surface facing the backlight frame 11 except for the chip portion of the light emitting diode (LED) 21. Moreover, the extraction part of the light emitting diode (LED) 21 and the wiring circuit on the back surface are connected by, for example, a through hole. In this case, no wiring exists on the surface facing the backlight frame 11.

It is a figure which shows the whole structure of the liquid crystal display device with which this Embodiment is applied. It is a figure for demonstrating the structure of the attachment part of the mounting board | substrate in a backlight apparatus. (A), (b) is explanatory drawing which shows each element formed on a mounting substrate. (A), (b) is the figure shown about an example of the attachment structure of the mounting board | substrate conventionally employ | adopted.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Backlight apparatus (backlight), 11 ... Backlight frame, 11a ... LED arrangement part, 11c ... Through-hole, 12 ... Mounting board, 13 ... Diffusing plate, 14, 15 ... Prism sheet, 16 ... Brightness improvement film, DESCRIPTION OF SYMBOLS 21 ... Light emitting diode (LED), 24 ... Insulating layer, 25 ... Metal film area | region, 26 ... Thermal sheet, 30 ... Liquid crystal display module, 31 ... Liquid crystal panel, 32, 33 ... Polarizing plate (polarizing filter)

Claims (4)

A display device that includes a display panel that displays an image and a direct-type backlight that irradiates the display panel from the back side,
The backlight is
A plurality of solid-state light emitting elements, which are composed of a plate-like member made of a resin-containing material and are arranged at predetermined intervals, and a heat transfer portion for transmitting heat generated by the solid-state light emitting elements are mounted on the mounting surface. a mounting substrate,
One surface facing the mounting surface of the mounting substrate, and the other surface serving as the back surface of the one surface, provided on the mounting substrate so that the one surface is in contact with the heat transfer portion, A heat conduction member that conducts heat transferred from the heat transfer unit;
The first surface and facing the display panel side, the second surface and a Rutotomoni as a rear surface of the first face, is arranged at a predetermined interval in the entire second surface, the first from the second surface A plurality of through holes penetrating toward the surface, the plurality of solid-state light emitting elements provided on the mounting substrate are respectively aligned with the positions of the plurality of through holes, and the mounting substrate is attached from the second surface side and a frame to be,
In the frame, the heat generated from the plurality of solid state light emitting elements and transmitted to the heat conducting member via the heat transfer unit is caused by the other surface of the heat conducting member being in contact with the second surface. Conducting through the second surface and sandwiching the heat conducting member between the mounting substrate, so that the plurality of solid state light emitting devices provided on the mounting substrate do not protrude from the first surface. The display device is characterized in that the mounting substrate is attached thereto. The mounting substrate of the backlight is provided with a wiring circuit connected to the solid-state light-emitting element provided on the mounting surface, and an insulating layer on the mounting surface to cover the wiring circuit,
The display device according to claim 1 , wherein the wiring circuit and the heat transfer unit are made of the same metal material . A plurality of solid-state light emitting elements, which are composed of a plate-like member made of a resin-containing material and are arranged at predetermined intervals, and a heat transfer portion for transmitting heat generated by the solid-state light emitting elements are mounted on the mounting surface. a mounting substrate,
One surface facing the mounting surface of the mounting substrate, and the other surface serving as the back surface of the one surface, provided on the mounting substrate so that the one surface is in contact with the heat transfer portion, A heat conduction member that conducts heat transferred from the heat transfer unit;
Wherein a first surface to provide light from the solid state light emitters, said second surface and a Rutotomoni to be the rear surface of the first face, is arranged at a predetermined interval in the entire second surface, said second surface A plurality of through holes penetrating from the second surface side to the first surface, and aligning the plurality of solid state light emitting elements provided on the mounting substrate with the positions of the plurality of through holes, respectively, from the second surface side. A frame to which a mounting board is attached ,
In the frame, the heat generated from the plurality of solid state light emitting elements and transmitted to the heat conducting member via the heat transfer unit is caused by the other surface of the heat conducting member being in contact with the second surface. Conducting through the second surface and sandwiching the heat conducting member between the mounting substrate, so that the plurality of solid state light emitting devices provided on the mounting substrate do not protrude from the first surface. And the mounting board is attached to the light emitting device. The mounting board and configured wiring circuit of the same material as the heat transfer unit is connected to the solid-state light-emitting element provided on the mounting surface, an insulating layer on the mounting surface to cover the wiring circuit The light emitting device according to claim 3 , wherein the mounting surface including the insulating layer is opposed to the second surface of the frame.

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