JP2012014949A - Lighting system and image display device equipped with it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lighting system and an image display device equipped with it capable of improving heat dissipation performance with structural strength maintained, restraining brightness unevenness caused by uneven distribution of heat, and aiming at thinning of the system.SOLUTION: A thermally conductive member 6 has a light source retention part with a face opposed to a light-incident face and a plate-shaped part with a face opposed to a light irradiation face as well as a face opposed to a heat dissipation member 5 formed in adjacency. The light source retention part has light sources 7 arranged toward the light-incident face on a face opposed to the light-incident face, a face of the plate-shaped part opposed to the heat dissipation member 5 is in contact with a face of the heat dissipation member 5 opposed to a light guide member, and a gravity center of the plate-shaped part is slanted along a direction in parallel with both the light-incident face and the light irradiation face.

Description

  The present invention relates to an illumination device used in an image display device such as a liquid crystal display device.

  In general, an image display device such as a liquid crystal display device includes a display panel for controlling brightness, chromaticity, and the like of a pixel, a backlight device (illumination device) that emits light toward the display panel, and these It consists of a control circuit and a circuit board for controlling.

  The backlight device diffuses light rays in the image display device and emits light toward the display panel. There are two types of backlight devices: a direct-light type in which light sources are distributed on the back side of the backlight device, and an edge light method in which the light source is installed to allow light to enter from the side of the backlight device (“side light method”). Also called). The edge light method has an advantage that the thickness of the backlight device can be reduced compared with the direct type and the commercial value can be increased.

  Conventionally, cold cathode fluorescent lamps have been used as types of light sources used in image display apparatuses. In recent years, point light sources such as light-emitting diodes (hereinafter referred to as “LEDs”) have also been used. The light source generally generates heat with the light. Even in the case of an LED, heat is generated by causing a current to flow to emit light. When the LED becomes high temperature due to the heat, the luminous efficiency is lowered, and the lifetime of the element in the image display device is shortened. In the worst case, the element is destroyed and there is a possibility that the element does not emit light.

  In particular, in the edge light system, the light source serving as a heat source is not distributed on the back surface of the backlight device, and is installed in the edge portion around the backlight device, which is a disadvantageous configuration from the viewpoint of heat dissipation. Yes. This is because heat is most easily transmitted and released when it is uniformly distributed, and heat is less likely to be transferred and released when it is unevenly distributed.

  In recent years, the edge light system has been used not only for a small screen (display) such as a mobile phone but also for a large screen (display) such as a television. In order to increase the size of the screen, the luminance on the screen cannot usually be lowered, so the total amount of light required for the light source must be increased in proportion to the area. That is, it is necessary to increase the amount of light in proportion to the square of the length in the vertical direction or the horizontal direction on the screen.

  On the other hand, in the case of the edge light system, the amount of increase in the space where the light source can be installed is proportional to the length of the periphery of the screen (display). That is, only an increase proportional to the first power of the length in the vertical or horizontal direction on the screen can be obtained. Therefore, in principle, the amount of light required per LED increases, and the amount of heat generation increases.

  This situation is a general problem related to the light source when the screen size is increased from the direct type to the edge light method. However, heat generation from the light source is larger in the light incident method from the upper and lower two sides or the left and right sides of the screen than the light incident method from the four sides of the screen. In particular, LCD TVs, personal computer displays, etc. are generally used in a horizontally long shape, so that heat generation is greater when light enters from the left and right sides instead of the upper and lower sides, and conventional heat dissipation methods cannot cope with it. A situation has arisen.

  Here, as a conventional heat dissipation method, in a backlight device equipped with a small and medium-sized screen (display) such as a mobile phone and a car navigation system, conventionally, a method of releasing heat by releasing heat due to heat generated by the element has been performed. ing. For example, in Patent Document 1, in a liquid crystal display device, a board on which an LED is mounted is directly fixed to a rear frame and a front frame with screws, thereby shortening the path to the frame and efficiently transferring heat to dissipate heat. A heat dissipation technique is shown. According to this heat dissipation method, the rear frame and the front frame act as heat dissipation members.

JP 2009-3081 A (published January 8, 2009) JP 2008-152109 A (released July 3, 2008)

  However, in the liquid crystal display device disclosed in Patent Document 1, since heat concentrates in the vicinity of the LED that is a point light source, the heat distribution becomes uneven and the rear frame and the front frame that act as a heat radiating member are moved to. The heat conduction of the worsens. As a result, there is a problem that the heat dissipation performance is degraded. In addition, the liquid crystal display device has a problem in that the structural strength of the rear frame and the front frame is reduced when the liquid crystal display device is enlarged.

  The present invention has been made in view of the above-described conventional problems, and the object thereof is to improve heat dissipation performance while maintaining structural strength, and is based on uneven distribution of heat. An object of the present invention is to provide an illuminating device capable of suppressing unevenness in luminance and reducing the thickness of the device, and an image display device including the same.

  As a technique for solving the above-mentioned problem, for example, in Patent Document 2, a display device (backlight device) includes a display surface on which information is displayed and a light source that emits light for illuminating the display surface from the rear side. A display panel unit having a light emitting part that generates heat linearly with light emission, a heat radiator that transmits heat emitted from the light emitting part of the display panel unit, and a light emitting part The center of the heat transfer part is provided with a heat transfer part that has better heat transfer at the center and end of the linear heat generation point in the light emitting part that transfers heat to the heat radiator. A heat dissipation method that actively dissipates heat is shown.

  In view of the above problems, the present inventors have intensively studied the heat dissipation performance of the display device (backlight device) disclosed in Patent Document 2.

  Here, in a general display device (backlight device), the actual situation is that the display surface is used vertically (the light sources are arranged vertically, and the light is emitted in the form of vertical lines). When the light source is turned on in the display device, heat flows upward due to natural convection, and heat tends to stay on the upper side of the display device.

  In the display device shown in Patent Document 2, when light is emitted linearly from a light source that exists on the side of the display surface, heat is likely to accumulate in the central portion of the heat generation portion that has generated heat linearly. In the heat transfer section, the heat at the center is efficiently radiated. However, the heat dissipation method disclosed in Patent Document 2 cannot be said to be a method that matches the actual situation of the display device, and cannot effectively dissipate the upper heat. As a result, the present inventors have found that the heat distribution is not uniform throughout the heat transfer section.

  And, based on the actual situation of using the display surface of the display device in a vertical orientation, the present inventors make the area above the heat transfer section larger than the area below the heat transfer section, Since the heat distribution is uniform throughout the heat transfer section, it has been found that the heat dissipation performance of the display device can be improved, and the present invention has been completed.

  That is, in the illumination device of the present invention, in order to solve the above problems, a light source, a light guide member having a light incident surface and a light output surface perpendicular to the light incident surface, and the back surface of the light guide member A heat dissipating member disposed opposite to the light emitting surface, and a heat conductive member for transmitting heat generated by the light source to the heat dissipating member. In the heat conductive member, A light source holding portion having a surface facing the light incident surface, and a plate-like portion having a surface facing the light emitting surface and a surface facing the heat radiating member are formed adjacent to each other in the light source holding portion. The light source is disposed on the surface facing the light incident surface toward the light incident surface, and the surface of the plate-shaped portion facing the heat radiating member is the light guide of the heat radiating member. In contact with the surface facing the member, in the plate-like portion, the plate-like portion Center of gravity, is characterized by biased along a direction parallel to both the light incident surface and the light exit surface.

  According to said structure, since the gravity center of a plate-shaped part is biased along the direction parallel to both a light-incidence surface and a light-projection surface, in the plate-shaped part, the area of the surface of the side where the gravity center is biased However, it becomes larger than the area of the other surface. As a result, heat is easily radiated on the surface where the center of gravity is biased. And, in a display device that uses the display surface in a vertical orientation, heat is efficiently diffused on the upper side where heat is accumulated by using the lighting device with the side where the center of gravity is biased upward. Heat can be efficiently transferred to the heat radiating member. Thereby, in the whole said illuminating device, the heat conduction from a light source to a heat radiating member becomes favorable. As a result, the lighting device of the present invention can improve the heat dissipation performance.

  Moreover, according to said structure, since the heat conductive member is provided separately from the heat radiating member, heat radiating performance can be improved, maintaining structural strength.

  Moreover, according to said structure, since heat is diffused by a heat conductive member, the heat distribution in a light source becomes uniform, and the dispersion | variation in the temperature in a light source can be reduced. As a result, the illumination device of the present invention can suppress uneven brightness of the light source.

  Moreover, according to said structure, a circuit board etc. can be arrange | positioned using the part in which the gravity center of a plate-shaped part is not biased in a heat conductive member. As a result, the lighting device of the present invention can be reduced in thickness.

  Moreover, it is preferable that the said light source holding | maintenance part and the said plate-shaped part are integrally formed in the illuminating device of this invention.

  Thereby, the illuminating device of this invention can reduce the interface of each member. As a result, the lighting device of the present invention can transmit heat to the heat radiating member more efficiently, and can further improve the heat radiating performance.

  The lighting device of the present invention further includes a reinforcing member for reinforcing the thermal conductive member, and a surface of the reinforcing member that faces the light incident surface is the thermal conductive member. It is preferable that the surface facing the light incident surface is in contact with the back surface, and the surface of the reinforcing member facing the heat dissipation member is in contact with the surface of the heat dissipation member facing the light guide member.

  Thereby, the illuminating device of this invention can improve structural intensity | strength.

  In the illumination device of the present invention, it is preferable that the center of gravity is biased in the direction opposite to the gravity direction when both the light incident surface and the light output surface are arranged perpendicular to the horizontal plane.

  Thereby, heat becomes easy to radiate heat in the lighting device of the present invention on the upper side. As a result, in a display device in which the display surface is used vertically, heat can be efficiently radiated on the upper side where heat is accumulated.

  Further, in the lighting device of the present invention, the thermal resistance per unit length in the direction along the contact surface between the heat conductive member and the heat radiating member in the heat conductive member is the heat resistance in the heat radiating member. It is preferably smaller than the thermal resistance per unit length in the direction along the contact surface between the conductive member and the heat radiating member.

  Thereby, as for the illuminating device of this invention, a heat conductive member can assist the heat conduction to the said direction in a thermal radiation member. As a result, in the lighting device of the present invention, the heat distribution in the heat radiating member is made more uniform, and the heat radiating performance can be further improved.

  In the lighting device of the present invention, it is preferable that the thermal conductivity of the thermal conductive member is in a range of 200 W / m · K or more and 1000 W / m · K or less.

  Thereby, the illuminating device of this invention can diffuse a heat | fever efficiently with the said heat conductive member. As a result, the lighting device of the present invention can transfer heat to the heat dissipation member more efficiently.

  In addition, an image display device of the present invention includes the above-described illumination device.

  As a result, the image display apparatus of the present invention can suppress the uneven brightness of the light source and improve the heat dissipation performance while maintaining the structural strength, so the temperature of the light source can be lowered and the luminous efficiency can be improved. Can be made. In addition, the image display device of the present invention can suppress the temperature rise of the element even when operated at high brightness to illuminate a large screen, and the operation of a large and thin image display device due to side incident light. Enable.

  As described above, the lighting device of the present invention includes a light source, a light guide member having a light incident surface and a light emitting surface perpendicular to the light incident surface, and the light emitting surface on the back surface of the light guiding member. And a heat conductive member for transmitting heat generated by the light source to the heat dissipating member, and facing the light incident surface in the heat conductive member. A light source holding portion having a surface, and a plate-like portion having a surface facing the light emitting surface and a surface facing the heat radiating member are formed adjacent to each other, and in the light source holding portion, the light source The surface facing the light incident surface is disposed toward the light incident surface, and the surface of the plate-shaped portion facing the heat radiating member is the surface of the heat radiating member facing the light guide member. And the center of gravity of the plate-like portion is the light incident surface and the plate-like portion. Those that are biased along a direction parallel to both of the light emitting surface.

  Therefore, the illuminating device of the present invention can improve the heat dissipation performance while maintaining the structural strength, can suppress the luminance unevenness caused by the non-uniform distribution of heat, and is thin. There is an effect that it can be realized.

It is sectional drawing which shows schematic structure of the liquid crystal display device provided with the backlight apparatus in Embodiment 1 of this invention. It is a perspective view which shows the structure of the light source vicinity of the backlight apparatus in Embodiment 1 of this invention. It is sectional drawing which shows the structure of the light source vicinity of the backlight apparatus in Embodiment 1 of this invention. It is a perspective view which shows the structure of the heat spreader (thermally conductive member) in Embodiment 1 of this invention. It is a graph which shows the temperature of the light source vicinity of the backlight apparatus in Embodiment 1 of this invention. It is a graph which shows the temperature of the light source vicinity of the backlight apparatus in Embodiment 1 of this invention. It is a top view which shows the structure of the heat spreader (thermally conductive member) in Embodiment 1 of this invention. (A)-(d) is a top view which shows the structure of the heat spreader (thermally conductive member) in Embodiment 1 of this invention. (A) * (b) is typical sectional drawing for demonstrating the difference in heat conductive performance in case the magnitude | size of a heat source differs. It is sectional drawing which shows the structure of the light source vicinity of the backlight apparatus in Embodiment 2 of this invention. It is a perspective view which shows the structure of the heat spreader (thermally conductive member) in Embodiment 2 of this invention. It is sectional drawing which shows the structure of the light source vicinity of the backlight apparatus in Embodiment 3 of this invention. It is a perspective view which shows the structure of the heat spreader (thermally conductive member) in Embodiment 3 of this invention. (A) * (b) is sectional drawing which shows the preferable structure of the light source vicinity of the backlight apparatus in Embodiment 3 of this invention. It is sectional drawing which shows the preferable structure of the light source vicinity of the backlight apparatus in Embodiment 3 of this invention.

  Embodiments of the present invention will be described in detail below, but the scope of the present invention is not limited to these descriptions, and modifications other than the following examples may be made as appropriate without departing from the spirit of the present invention. It can be implemented.

Embodiment 1
(I) Configuration of Illumination Device in Present Embodiment In the illumination device in the present embodiment, a light source, a light guide member having a light incident surface and a light exit surface perpendicular to the light incident surface, and the light guide member A heat dissipating member disposed on the back surface facing the light emitting surface, and a heat conductive member for transmitting heat generated by the light source to the heat dissipating member, A light source holding portion having a surface facing the light incident surface, and a plate-like portion having a surface facing the light emitting surface and a surface facing the heat radiating member are formed adjacent to each other, and the light source holding portion The light source is disposed on the surface facing the light incident surface toward the light incident surface, and the surface of the plate-shaped portion facing the heat radiating member is the conductive member of the heat radiating member. In contact with the surface facing the optical member, The center of gravity of the plate-like portion is biased along a direction parallel to both the light incident surface and the light emitting surface.

  That is, the illuminating device in the present embodiment includes a light source and a light guide member. Light from the light source is incident from the light incident surface of the light guide member, and light is emitted from the light output surface of the light guide member. The back surface of the light guide member viewed from the light emitting surface side has a function of releasing the amount of heat generated by the light source to the outside of the apparatus. The light source is provided on a heat conductive member connected to the heat radiating member having a surface perpendicular to the light emitting surface of the light guide member, and an optical axis thereof is directed to the inside of the light guide member. ing. Here, the light source is disposed on the heat conductive member, and the heat conductive member and the heat radiating member are in contact, that is, the heat conductive member and the heat radiating member are connected. The amount of heat generated by the light source is successfully transmitted to the heat radiating member, and the amount of heat is released from the heat radiating member to the outside of the apparatus.

  Further, in the lighting device according to the present embodiment, the plate-like portion in the direction along both the light emitting surface and the light incident surface on the surface of the thermally conductive member facing the light guide member in the plate-like portion. When the plate-like part is divided into two so that the length of both ends of the part is halved, the area of one surface is larger than the area of the other surface, and the light incident surface of the one surface The length of the longest portion in the normal direction is longer than the length of the longest portion of the other surface in the normal direction of the light incident surface.

  Moreover, the illuminating device in this embodiment may be provided with the housing | casing which consists of a heat radiating member.

  Moreover, since the illuminating device in this embodiment needs to install many kinds of components, such as a speaker, an external connection terminal, and a power switch, it is necessary to reduce the area of a heat sink as much as possible. At that time, by reducing the area of the heat sink at the lower part of the center with less heat generation, and making that part a place to place other parts etc., heat dissipation can be achieved without increasing the size. Can be secured.

  In the illumination device according to the present embodiment, it is preferable that the light source holding part and the plate-like part are integrally formed. In the illumination device according to the present embodiment, it is preferable that the center of gravity is biased in the direction opposite to the gravitational direction when both the light incident surface and the light exit surface are arranged perpendicular to the horizontal plane. Further, in the lighting device according to the present embodiment, the thermal resistance per unit length in the direction along the contact surface between the heat conductive member and the heat dissipation member in the heat conductive member is It is preferably smaller than the thermal resistance per unit length in the direction along the contact surface between the heat conductive member and the heat dissipation member.

  Specifically, it demonstrates concretely, referring FIGS. FIG. 1 is a schematic cross-sectional view illustrating a configuration of a liquid crystal display device (image display device) 10 including a backlight device (illumination device) 1 according to the present embodiment. FIG. 2 is a perspective view showing a configuration in the vicinity of the light source 7 of the backlight device 1 in the present embodiment. 3 and 4 are cross-sectional views showing the configuration near the light source 7.

  As shown in FIGS. 1 to 4, the backlight device 1 in this embodiment mainly includes a light source 7 (a plurality of point light sources (light emitting elements) 2 and a substrate 3 on which the point light sources 2 are mounted), and a light source 7. A heat spreader (thermally conductive member) 6 to be fixed, a chassis (heat radiating member) 5 connected to the heat spreader 6, and a light guide plate (light guide member) 22 that emits light incident from the light source 7 are provided. As a means for connecting each member (component), in addition to screwing, for example, fixing with an adhesive tape, an adhesive, etc .; fitting;

  As shown in FIG. 1, the liquid crystal display device 10 in this embodiment mainly includes a backlight device 1, a reflection sheet 21, an optical sheet 23, a liquid crystal panel 24, and a bezel (outer frame) 25.

  The backlight device 1 according to the present embodiment diffuses heat in the heat path and makes the heat distribution uniform in order to improve the heat conduction performance when the heat generated from the light source 7 is transmitted to the heat radiating member 5. This is realized by using a configuration that can Details of each member will be described below.

<Light source (light emitting element and substrate)>
The light source 7 used in the backlight device 1 of the present embodiment may be only the point light source (light emitting element) 2 or may be one in which the point light source 2 is carried on the substrate 3. In FIGS. 1 to 3 and 10, the light source 7 is illustrated as having the point light source 2 carried on the substrate 3.

  In the backlight device 1 of the present embodiment, the light source 7 serves as a heat source, and the necessity of heat dissipation arises.

  Examples of the point light source 2 used in the backlight device 1 of the present embodiment include a light emitting diode (LED) and a cold cathode tube (CCFL). As the light emitting diode (LED), any of white LED light source, RGB-LED (light emitting diode in which R, G, B chips are molded in one package) light source, multi-color LED light source, and laser light source are preferable. Can be used.

  The substrate 3 used in the backlight device 1 of the present embodiment is not particularly limited as long as the point light source 2 can be mounted. For example, a metal substrate based on aluminum (Al), copper (Cu), or the like having high thermal conductivity can be preferably used.

  In the present embodiment, “mounting” refers to mounting an electronic component such as a light source on a substrate. In this embodiment, the method of attaching a light source etc. on a board | substrate is not specifically limited, For example, the method of attaching by soldering etc. are mentioned.

  Here, the heat conducted to the back side of the substrate 3 is transmitted to the heat spreader 6 in contact therewith. At this time, thermal resistance is generated at the interface between the substrate 3 and the heat spreader 6. In order to reduce this thermal resistance as much as possible, it is important to make the contact area between the heat spreader 6 and the substrate 3 wider and to ensure adhesion.

  In the structure of the present embodiment, the heat spreader 6 is disposed on the back side of the substrate 3 on which the point light source 2 serving as a heat source is mounted, and the heat path from the heat source is the shortest, so that heat dissipation is achieved. It has an excellent structure.

<Heat spreader (thermally conductive member)>
The heat spreader 6 used in the backlight device 1 of the present embodiment includes a frame (light source holding unit) 17 having a surface facing the light incident surface, a surface facing the light emitting surface, and a surface facing the heat dissipation member 5. A heat conduction plate (plate-like portion) 16 having a gap is formed adjacently (see FIG. 10). In the present embodiment, as illustrated in FIGS. 1 to 4, the heat spreader 6 is illustrated as a frame 17 and a heat conductive plate 16 that are integrally formed. The heat spreader 6 in which the frame 17 and the heat conductive plate 16 are separately formed is shown as a second embodiment described later.

  The heat spreader 6 used in the backlight device 1 of the present embodiment is not particularly limited as long as it has structural strength and high thermal conductivity.

  FIG. 4 shows the shape of the heat spreader 6 of this embodiment. When the lighting device is used in a vertical position, the front side (portion having a length L) of the heat spreader 6 shown in FIG. 4 is positioned on the upper side, and the back side of the heat spreader 6 shown in FIG. 4 is positioned on the lower side. To do.

  In the present embodiment, as a structure for further improving heat conduction, an L-shaped shape is used when the shape of the heat spreader 6 is viewed from the cross section (the surface shown in FIG. 3). Thereby, the contact area of the heat spreader 6 and the chassis 5 increases, and the thermal resistance at the interface further decreases.

  The prism portion (frame, light source holding portion) located on the back side of the substrate 3 of the heat spreader 6 is, for example, a prism column of about 7 mm square, and it is desirable that the cross-sectional area is larger than that of the substrate 3. Moreover, in the heat spreader 6, the plate | board thickness of the thin-plate part (heat conductive board, plate-shaped part) extended in the direction parallel to the chassis 5 is about 2 mm, for example. Further, the lateral length L of the thin plate is set to about 100 mm in the case of a liquid crystal display device of 60 type or more, for example, because heat can be radiated to the outside more efficiently. The prism portion and the thin plate portion are combined to form an L-shaped heat spreader 6.

  Further, the shape of the tip of the thin plate in the heat spreader 6 located on the center side of the lighting device is made to have a long tip length slightly lowered from the upper side (front side) of the heat spreader 6 as shown in FIG. The lower end of the heat spreader 6 is shortened. The reason for this structure will be described below with reference to FIGS.

  FIG. 5 shows each LED (dot) when the length L in the light incident direction of the L-shaped heat spreader 6 shown in FIG. 4 is set to 100 mm using a 68-type liquid crystal display device having the structure shown in FIG. The result of the temperature distribution of the light source) is shown. The horizontal axis of the graph shown in FIG. 5 is the LED temperature measurement position, and the vertical axis is the measurement temperature. The left side of the horizontal axis of the graph is the measurement point on the upper side of the LED, and the right side of the horizontal axis of the graph indicates the measurement point on the lower side of the LED.

  According to this result, it turns out that the temperature of LED located on the upper side of an illuminating device is high, and the temperature of LED located below is lower than the upper side. This is because, when an LED is turned on as a liquid crystal display device, heat is convected upward due to natural convection, and accordingly, heat generated from each LED is also convected upward. For this reason, the heat radiation of the upper LED is deteriorated, and the temperature of the lower LED is lower than that of the upper LED.

  Furthermore, according to the result of FIG. 5, the portion where the temperature of the LED is most increased is not the uppermost LED but an LED located slightly below the uppermost portion. The reason for this is that the uppermost LED has no adjacent LED on the upper side, so that the generated heat is relatively easily released to the outside. For this reason, the temperature of the LED located immediately below the uppermost portion where heat is most likely to be accumulated tends to increase.

  FIG. 6 shows the result of the temperature distribution of each LED when the length in the light incident direction from the light source of the thin plate portion of the L-shaped heat spreader 6 is shortened to 40 mm as compared with the measurement shown in FIG. Is shown. According to this result, when the length of the thin plate portion is shortened, it can be seen that the LED temperature generally increases by 2 to 3 ° C. while maintaining the temperature distribution above and below the LED. Therefore, by extending the length of the thin plate portion of the L-shaped heat spreader 6, the influence of the thermal resistance can be minimized, and heat can be radiated efficiently, so that the temperature of the heat source can also be lowered.

  From the results of FIGS. 5 and 6, it is apparent that the temperature of the heat source can be lowered by increasing the length of the thin plate portion of the L-shaped heat spreader 6. Based on this, in order to make the variation in the light output of each LED uniform, along the temperature distribution of the LEDs that are the arranged heat sources, in the portion where the LED temperature is high relative to the portion where the LED temperature is low By increasing the length of the L-shaped thin plate portion in the heat spreader 6, the temperature of the heat source can be evenly dissipated.

  Based on these results, in the evaluation using the 68-inch liquid crystal display device, in the heat spreader 6, when the longest part located slightly below the uppermost part is 100 mm, the lower length which is the shortest part is determined. When the thickness was about 30 mm, the temperature distribution of the LED was uniform.

  FIG. 7 shows the shapes of the heat spreader 6 and the chassis 5 as viewed from above. 8A to 8D show specific examples in which the shape of the heat spreader 6 shown in FIG. 7 is changed in the direction perpendicular to the light source arrangement direction. 7 and 8 (a) to 8 (d), the upper side in the figure is the upper side of the liquid crystal display device, and the lower side in the figure is the lower side of the liquid crystal light emitting device. As shown in FIGS. 8A to 8D, the length of the heat spreader 6 in the portion where the temperature of the heat source such as the LED is high is set to be longer than the length of the heat spreader 6 in the portion where the temperature of the heat source is low. By making it long, heat can be radiated without generating a temperature distribution in the arranged light sources. Furthermore, a circuit board etc. can be accommodated using the space of the part where the length of the heat spreader 6 is short. Therefore, when it is set as a liquid crystal display device, an empty space can be used effectively and it can lead to further thickness reduction.

<Chassis (heat dissipation member)>
The chassis 5 used in the backlight device 1 of the present embodiment is not particularly limited as long as it has heat dissipation performance and structural strength. Moreover, as the chassis 5 used for the backlight device 1 of the present embodiment, for example, an aluminum alloy, a steel plate, stainless steel, or the like can be preferably used. Examples of the aluminum alloy include materials such as A5052 (tensile strength 195 N / mm ² , thermal conductivity 138 W / m · K) and A6063 (tensile strength 185 N / mm ² , thermal conductivity 209 W / m · K). . Examples of the steel plate include SECC (thermal conductivity 70 W / m · K). Examples of stainless steel include materials such as SUS (thermal conductivity 15 W / m · K).

<Light guide plate (light guide member)>
The light guide plate 22 used in the backlight device 1 of the present embodiment has a light incident surface and a light emitting surface perpendicular to the light incident surface, and can emit light incident from the light source 7. There is no particular limitation as long as it is possible.

<Other members>
In the liquid crystal display device 10 according to the present embodiment, as the reflection sheet 21, the optical sheet 23, the liquid crystal panel 24, and the bezel 25, those provided in a conventionally known liquid crystal display device can be used.

<Method of heat conduction>
A method of heat conduction in the backlight device 1 of the present embodiment will be specifically described below with reference to FIGS. 1 to 4 and FIGS. 9A and 9B. In the following description, the light source 7 is described as an example in which the point light source 2 is carried on the substrate 3.

  Heat generated from the point light source 2 such as an LED is first transmitted to the substrate 3. At this time, the thickness of the substrate 3 is generally about 1 to 2 mm in the case of a metal substrate, and the length in the longitudinal direction of the substrate 3 is the length of one side of the screen. Generally, it is about 300 mm to 1200 mm. A plurality of point light sources 2 are arranged in the longitudinal direction of the substrate 3. As the size of the point light source 2, a rectangle (rectangle, square, etc.) having a side of about 3 mm to 10 mm is generally used.

  In that case, heat conduction in the thickness direction of the substrate 3 is relatively good because heat is transferred within the range of the size of the point light source 2. However, since the heat conduction in the longitudinal direction of the substrate 3 proceeds only in the range of the thickness direction of the substrate 3, it is inferior to the heat conduction in the thickness direction. For this reason, distribution arises in heat by arrangement | positioning etc. of LED.

  Specifically, the LEDs near the center are densely populated with other LEDs on both sides, so heat is trapped. On the other hand, since the LED arranged at the end has no heat source next to it, heat is likely to diffuse. As a result, the heat generated in the point light source 2 is distributed in the longitudinal direction of the substrate 3. In general, the luminous efficiency of an LED varies depending on the temperature. If all the LEDs are operated in a state where the heat generation state varies depending on each LED, the light emission state is different, which leads to occurrence of luminance unevenness in the backlight device 1, and this state is not preferable. The present embodiment can eliminate this state. The principle is as follows.

  According to the present embodiment, the substrate 3 is in contact with the heat spreader 6. The heat spreader 6 is formed of a material having high thermal conductivity as described above. Accordingly, sufficient heat diffusion is performed in the heat spreader 6. As a result, an effect of making the temperature of the substrate 3 uniform is produced, and variations in the operating temperature of the LEDs are reduced, so that uneven brightness in the backlight device 1 can be suppressed.

  In addition, heat uniformity has the effect of reducing thermal resistance. The mechanism by which heat conduction deteriorates when the heat distribution is uneven is explained as follows.

  FIGS. 9A and 9B are cross-sectional views when heat sources 12 and 13 having different sizes are mounted on a certain heat conductor 11. The thermal conductor 11 is the same in FIGS. 9A and 9B and has the same thermal conductivity, so the thermal resistance per unit area is also the same.

  When the same amount of heat is given to each of the heat sources 12 and 13 per unit time, heat is conducted through the heat conductor 11 according to the 45 degree rule. However, in a cross section A of the heat conductor 11, in the case of FIG. 9B compared to the case of FIG. 9A, the region contributing to heat conduction is narrow, and heat concentrates in a narrow area. Since the thermal resistance per unit area in the thermal conductor 11 is equal, the thermal resistance increases in the case of FIG. 9B compared to the case of FIG. 9A because the area contributing to the heat conduction is small. Accordingly, it can be seen that the temperature difference between the upper and lower sides of the heat conductor 11 is larger in the case of FIG. 9B than in the case of FIG. 9A, and the heat conduction is deteriorated.

  Therefore, if the heat conduction of the heat conductor 11 is improved when the same amount of heat is input per unit time, it is better to conduct the heat after expanding the heat in terms of area. I understand. It can also be seen that the heat conduction is best when the heat distribution is uniform.

  According to this embodiment, the heat transmitted from the substrate 3 to the heat spreader 6 is transmitted to the chassis 5 in a state of uniform distribution. For this reason, heat conduction is performed to the chassis 5 in a state with good heat conduction. And if the heat conduction to the chassis 5 is good, the temperature of the chassis 5 becomes high and the temperature difference from the atmospheric temperature is widened, so that the efficiency of heat exchange increases. As a result, the heat dissipation performance of the backlight device 1 is improved. Furthermore, the heat distribution in the planar direction of the chassis 5 is made uniform by adopting a configuration in which the thermal resistance in the planar direction of the heat spreader 6 is smaller than the thermal resistance in the planar direction of the chassis 5. Therefore, the performance of heat dissipation can be improved.

  In addition, it is desirable that a heat conduction auxiliary material such as a resin sheet, a metal sheet, or grease is inserted between each member in the backlight device 1 because the thermal resistance at the interface can be further lowered.

  In the present embodiment, the case of the edge light system with two-side incident light has been described. However, the present invention can be similarly applied to the case of four-side incident light.

  Further, in the present embodiment, the case where the illumination device is used as a backlight device for a liquid crystal display device has been described. The lighting device of the present embodiment is not limited to this case, and can also be used for lighting installed on the ceiling.

(II) Manufacturing Method of Lighting Device in the Present Embodiment In the manufacturing method of the lighting device in the present embodiment, the light source 7 (the point light source 2 and the substrate 3), the heat spreader 6, and the chassis 5 are connected in order. Thereafter, the light guide plate 22 is disposed. As a means for connecting each member, in addition to screwing, for example, fixing with an adhesive tape, an adhesive or the like; fitting; pressing;

[Embodiment 2]
The following describes the present embodiment with reference to FIGS. 10 and 11. For convenience of explanation, members having the same functions as those in the drawings described in the first embodiment are denoted by the same reference numerals and description thereof is omitted. Further, the explanation of the terms explained in the first embodiment will be omitted.

(I) Configuration of Illuminating Device in the Present Embodiment The illuminating device in the present embodiment is different from the illuminating device in the first embodiment described above in that the “heat spreader 6” is integrated with the “frame 17 and the heat conducting plate 16”. It is assumed that “the frame 17 and the heat conducting plate 16 are separated and formed” instead of “the formed one”.

  Specifically, FIG. 10 is a schematic cross-sectional view illustrating a configuration of a liquid crystal display device (image display device) 10 including the backlight device (illumination device) 1 according to the present embodiment. FIG. 11 shows the shape of the heat spreader 6 of this embodiment.

<Heat spreader (thermally conductive member)>
As shown in FIG. 10, the heat spreader 6 used in the backlight device 1 of the present embodiment includes a frame (light source holding unit) 17 having a surface facing the light incident surface, a surface facing the light emitting surface, and A heat conducting plate (plate-like portion) 16 having a surface facing the heat radiating member 5 is formed adjacent to the heat conducting plate 5. In the present embodiment, the frame 17 and the heat conductive plate 16 are separately formed.

<Frame (light source holder)>
The frame 17 used in the backlight device 1 of the present embodiment is not particularly limited as long as it has structural strength. In addition, as the frame 17 used in the backlight device 1 of the present embodiment, for example, an aluminum alloy, a steel plate, stainless steel, or the like can be preferably used. Examples of the aluminum alloy include materials such as A5052 (tensile strength 195 N / mm ² , thermal conductivity 138 W / m · K) and A6063 (tensile strength 185 N / mm ² , thermal conductivity 209 W / m · K). . Examples of the steel plate include SECC (thermal conductivity 70 W / m · K). Examples of stainless steel include materials such as SUS (thermal conductivity 15 W / m · K).

  The shape of the frame 17 used in the backlight device 1 of the present embodiment is a quadrangular prism shape having a rectangular or square cross section (surface shown in FIG. 3).

  The frame 17 has a surface perpendicular to the light exit surface of the light guide plate 22. Further, the frame 17 may or may not surround the light guide plate 22 with a surface perpendicular to the light emitting surface.

<Heat conduction plate (plate-shaped part)>
As the heat conductive plate 16 used in the backlight device 1 of the present embodiment, a plate having high thermal conductivity is used. The thermal conductivity of the heat conductive plate 16 is preferably in the range of 200 W / m · K or more and 1000 W / m · K or less. When the thermal conductivity of the heat conducting plate 16 is less than 200 W / m · K, the heat conduction becomes insufficient and the heat does not spread to the heat radiating member, so the area contributing to heat radiation becomes small and the heat radiation performance is insufficient. It is not preferable for the reason. On the other hand, when the thermal conductivity of the heat conductive plate 16 is larger than 1000 W / m · K, it is not preferable because it is expensive, soft and difficult to use, and causes deterioration over time.

  In the present embodiment, the “thermal conductivity” is a value obtained by dividing the amount of heat flowing in a unit time through a unit area perpendicular to the heat flow by a temperature difference (temperature gradient) per unit length in heat conduction. (W / m · K).

  Further, in the present embodiment, “thermal resistance” is a value representing the difficulty of transmitting temperature, and means a temperature increase amount (° C./W) with respect to a heat generation amount per unit time.

  Further, as the heat conduction plate 16 used in the backlight device 1 of the present embodiment, structural strength is not required, so a material having high heat conductivity may be selected. For example, aluminum, copper, carbon, silver or the like can be preferably used. Examples of pure aluminum include materials such as A1050 (thermal conductivity 225 W / m · K). Examples of pure copper include materials such as C1100 (thermal conductivity 391 W / m · K). In addition, materials such as a sheet containing a filler such as carbon and silver, and a metal flat plate with a built-in heat pipe can be used.

  The thermal conductivity of the heat conductive plate 16 used in the backlight device 1 of the present embodiment is larger than the thermal conductivity of the frame 17 and the chassis 5. Moreover, as thickness of the heat conductive board 16, about 0.5-2 mm is preferable.

  Examples of the shape of the heat conductive plate 16 used in the backlight device 1 of the present embodiment include a plate shape shown in FIG.

  The contact area between the heat conduction plate 16 and the chassis 5 is preferably larger than the contact area between the heat conduction plate 16 and the frame 17. In other words, the frame 17 has a shape such as a prism because mechanical strength is required. If an attempt is made to increase the contact area with the chassis 5 without using the heat conducting plate 16, the volume increases and the material cost increases. And the weight will increase. However, when the heat conduction plate 16 is used, even if the volume of the heat conduction plate 16 increases, the thickness is sufficiently thin, about 0.5 to 2 mm. Thus, the thermal resistance of the interface can be lowered by increasing the contact area between the heat conducting plate 16 and the chassis 5.

(II) Manufacturing method of lighting device in the present embodiment The manufacturing method of the lighting device in the present embodiment is “frame 17” and “thermal conductive plate 16” as compared with the manufacturing method of the lighting device in the first embodiment described above. Is the same as the manufacturing method of the lighting device in the first embodiment described above except that the “heat spreader 6” is manufactured.

[Embodiment 3]
The following describes the present embodiment with reference to FIGS. For convenience of explanation, members having the same functions as those in the drawings described in the first embodiment are denoted by the same reference numerals and description thereof is omitted. Further, the explanation of the terms explained in the first embodiment will be omitted.

(I) Configuration of Lighting Device in the Present Embodiment The lighting device in the present embodiment further includes a reinforcing member for reinforcing the “heat spreader 6” as compared with the lighting device in the first embodiment described above.

  Specifically, FIG. 12 is a schematic cross-sectional view illustrating a configuration of a liquid crystal display device (image display device) 10 including the backlight device (illumination device) 1 in the present embodiment. FIG. 13 shows the shape of the heat spreader 6 of this embodiment.

<Reinforcing member>
The reinforcing member 18 used in the backlight device 1 of the present embodiment is not particularly limited as long as it has structural strength. Moreover, as the reinforcing member 18 used in the backlight device 1 of the present embodiment, for example, an aluminum alloy, a steel plate, stainless steel, or the like can be preferably used. Examples of the aluminum alloy include materials such as A5052 (tensile strength 195 N / mm ² , thermal conductivity 138 W / m · K) and A6063 (tensile strength 185 N / mm ² , thermal conductivity 209 W / m · K). . Examples of the steel plate include SECC (thermal conductivity 70 W / m · K). Examples of stainless steel include materials such as SUS (thermal conductivity 15 W / m · K).

  The shape of the reinforcing member 18 used in the backlight device 1 of the present embodiment is a quadrangular prism shape having a rectangular or square cross section (surface shown in FIG. 12).

<Other embodiments>
As another example of the backlight device 1 according to the present embodiment, there is one in which the shape of the reinforcing member 18 is changed. Specifically, this will be specifically described with reference to FIGS. 14 (a) and 14 (b) and FIG.

  As shown in FIGS. 14A and 14B, the shape of the reinforcing member 18 is a polygonal column shape having a U-shaped cross section (the surface shown in FIGS. 14 and 15), or as shown in FIG. By making the shape of the reinforcing member 18 into a polygonal column shape having an L-shaped cross section, the material cost can be reduced as compared to a rectangular column shape having a rectangular or square cross section. The mechanical strength can be increased by bending the flat plate as described above.

  Further, the heat spreader 6 is configured such that the thermal resistance in the vertical direction (longitudinal direction of the substrate 3 and the frame 17) is smaller than the thermal resistance in the same direction of the chassis 5, so that the cross-sectional area of the frame 17 is increased. Even when the heat spreader 6 becomes smaller and the thermal resistance becomes higher than that of the prism, the heat is transferred to the chassis 5 after the heat distribution in the vertical direction of the heat spreader 6 becomes uniform. Therefore, compared with the case of only the chassis 5, the heat distribution in the vertical direction of the chassis 5 is made uniform. Further, by adopting a configuration in which the heat resistance in the planar direction of the heat spreader 6 is smaller than the thermal resistance in the planar direction of the chassis 5, the heat distribution becomes uniform in the planar direction of the heat spreader 6 and then the chassis. Since heat is transmitted to 5, heat conduction and heat dissipation performance can be improved.

(II) Manufacturing Method of Lighting Device in the Present Embodiment The manufacturing method of the lighting device in the present embodiment is the “reinforcing member 18” after the “heat spreader 6” as compared with the manufacturing method of the lighting device in the first embodiment described above. ”Is the same as the manufacturing method of the lighting device in the first embodiment described above.

[Other Embodiments]
The lighting device of the present embodiment includes, for example, a plurality of point light sources serving as heat sources, a substrate on which the plurality of point light sources are mounted in one or a plurality of rows, and a heat spreader serving as a heat conductor. The lighting device includes a chassis serving as a radiator, wherein the lighting device is a side-entering edge light system in which the plurality of point light sources are arranged in a line in a vertical direction, The point light source and the chassis are in contact with each other so as to conduct heat through the substrate and the heat spreader, and the heat spreader includes a surface parallel to the chassis, and the surface is provided on the substrate. When the upper part of the length in the longitudinal direction is divided into two as the first surface and the lower part as the second surface, the area of the first surface is larger than the area of the second surface, Next to the plane parallel to the chassis In the length of the direction, the longest portion of the first surface may be configured as longer than the longest portion of the second surface.

  Further, the illumination device of the present embodiment includes, for example, a plurality of point light sources serving as heat sources, a substrate on which the plurality of point light sources are mounted in one or a plurality of rows, and a heat spreader serving as a heat conductor. The lighting device includes a chassis serving as a radiator, wherein the lighting device is a side-entering edge light system in which the plurality of point light sources are arranged in a line in a vertical direction, The point light source and the chassis are in contact with each other so as to conduct heat through the substrate and the heat spreader, and the heat spreader has a surface perpendicular to the chassis, and the surface is formed on the substrate. When the upper part of the length in the longitudinal direction is divided into two as the first surface and the lower part as the second surface, the area of the first surface is larger than the area of the second surface, Next to the plane parallel to the chassis In the length of the direction, the longest portion of the first surface may be configured as longer than the longest portion of the second surface.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention.

  INDUSTRIAL APPLICABILITY The present invention is suitably used for a surface emitting backlight device provided in a liquid crystal display device such as a mobile phone, a notebook personal computer, and a television, particularly a side edge type large backlight device using a point light source such as an LED as a light source. can do.

1 Backlight device (lighting device)
2 Point light source (light emitting element, light source)
3 Substrate 5 Chassis (heat dissipation member)
6 Heat spreader (thermally conductive member)
7 Light source 10 Liquid crystal display device (image display device)
DESCRIPTION OF SYMBOLS 11 Heat conductor 12 Heat source 13 Heat source 16 Heat conductive plate (plate-shaped part)
17 frames (light source holder)
18 Reinforcing member 21 Reflecting sheet 22 Light guide plate (light guide member)
23 Optical sheet 24 Liquid crystal panel 25 Bezel (outer frame)

Claims (7)

A light source, a light guide member having a light incident surface and a light emitting surface perpendicular to the light incident surface, a heat dissipating member disposed on the back surface of the light guide member so as to face the light emitting surface, and A heat conductive member for transmitting heat generated by the light source to the heat radiating member;
In the heat conductive member, a light source holding portion having a surface facing the light incident surface, and a plate-like portion having a surface facing the light emitting surface and a surface facing the heat radiating member are formed adjacent to each other. And
In the light source holding part, the light source is disposed on a surface facing the light incident surface toward the light incident surface,
The surface of the plate-like portion facing the heat dissipation member is in contact with the surface of the heat dissipation member facing the light guide member,
In the above plate-like portion, the center of gravity of the plate-like portion is biased along a direction parallel to both the light incident surface and the light emitting surface.   The lighting device according to claim 1, wherein the light source holding part and the plate-like part are integrally formed. A reinforcing member for reinforcing the thermally conductive member,
The surface of the reinforcing member facing the light incident surface is in contact with the back surface of the surface of the thermally conductive member facing the light incident surface,
The lighting device according to claim 2, wherein a surface of the reinforcing member facing the heat radiating member is in contact with a surface of the heat radiating member facing the light guide member.   The center of gravity is biased in the direction opposite to the direction of gravity when both the light incident surface and the light exit surface are arranged perpendicular to a horizontal plane. Lighting device.   In the heat conductive member, the thermal resistance per unit length in the direction along the contact surface between the heat conductive member and the heat radiating member is determined between the heat conductive member and the heat radiating member in the heat radiating member. The lighting device according to claim 1, wherein the lighting device is smaller than a thermal resistance per unit length in a direction along the contact surface.   6. The lighting device according to claim 1, wherein the thermal conductivity of the thermal conductive member is in a range of 200 W / m · K to 1000 W / m · K. An image display device comprising the illumination device according to claim 1.

Images