JP2012014946A - 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 the same capable of improving heat dissipation performance with structural strength maintained, and capable of restraining brightness unevenness of light sources.SOLUTION: The lighting system is provided with light sources 7, a light guide member 22 equipped with a light-incident face and a light emitting face vertical to the former, a light source retention member 4 for arranging the light sources 7 in a direction of the light-incident face and a heat dissipation member 5 arranged in opposition to the light emitting face at the back of the light guide member 22. The light source retention member 4 is equipped with a face opposed to the light guide member 22 and a face opposed to the heat dissipation member 5, with the face opposed to the heat dissipation member 5 connected with a face opposed to the light guide member 22 of the heat dissipation member 5. The light sources 7 are arranged on a face of the light source retention member 4 opposed to the light guide member 22 through a thermally conductive member 6, which 6 is in contact with a face opposed to the light guide member 22 of the heat dissipation member 5.

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. In general, a light source generates heat together with 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 likely to be conducted and released when it has a uniform distribution, and heat and conduction are less likely to occur when it has a non-uniform distribution.

  Further, in recent years, the edge light system has been used not only on a small screen (display) such as a mobile phone but also on 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 reduced. Therefore, 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 rule relating 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, as shown in FIG. 14, in the liquid crystal display device 100, the substrate 104 on which the LED 103 is mounted is directly fixed to the rear frame 101 and the front frame 111 with screws 113, so that a route to the frame is obtained. A heat dissipation method is disclosed in which heat is efficiently transmitted and heat is dissipated. According to this heat dissipation method, the rear frame 101 and the front frame 111 act as heat dissipation members. Further, as shown in FIG. 15, Patent Document 2 discloses a heat dissipation technique for dissipating heat by attaching a substrate 222 mounted with LEDs 221 directly to a heat sink (heat dissipation member) 223 on the back surface of the liquid crystal display device 210 (backlight 211). Has been. According to this heat dissipation method, the substrate 222 on which the LED 221 is mounted and the heat sink 223 are in direct contact, and the heat conduction path is shortened.

JP 2009-3081 A (published January 8, 2009) JP 2007-286467 A (published November 1, 2007)

  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 non-uniform, and the rear frame and the front frame function as heat dissipation members. The heat conduction to becomes worse. 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.

  Further, in the liquid crystal display device disclosed in Patent Document 2, heat is transmitted to the lower part of the LED because the heat conduction of the substrate on which the LED is mounted is poor, but the heat sink temperature is too low in the portion without the LED. Does not rise. As a result, in the heat sink, there is a problem that heat distribution becomes uneven and heat dissipation performance is deteriorated. In addition, the liquid crystal display device has a problem in that the structural strength of the heat sink decreases 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 the heat dissipation performance while maintaining the structural strength, and to suppress the luminance unevenness of the light source. An object of the present invention is to provide a lighting device that can be used and an image display device including the same.

  In view of the above problems, the present inventors have intensively studied why the heat dissipation performance cannot be improved while maintaining the structural strength in the liquid crystal display devices (backlight devices) disclosed in Patent Documents 1 and 2 above. did. As a result, in the liquid crystal display devices disclosed in Patent Documents 1 and 2, a substrate on which an LED (light emitting element) is mounted is directly attached to a heat radiating member ("Rear frame" in Patent Document 1 above, "Heat dissipation" in Patent Document 2 above). It was found that it is difficult to give the heat radiating member structural strength because the material is fixed to the member “) and a material having high thermal conductivity is used as the heat radiating member. This is because there is generally no material having both heat conduction performance and structural strength.

  The inventors have uniquely found that by providing a heat conductive member separately from the heat radiating member and the light source holding member, it is possible to improve the heat radiating performance while maintaining the structural strength. It came to complete.

  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 emitting surface perpendicular to the light incident surface, and the light source as a light incident surface. A light source holding member that is disposed toward the light guide member, and a heat radiating member that is disposed on the back surface of the light guide member so as to be opposed to the light emitting surface. And a surface facing the heat radiating member, and a surface facing the heat radiating member is connected to a surface of the heat radiating member facing the light guide member, and the light source Is disposed on a surface of the light source holding member facing the light guide member via a heat conductive member, and the heat conductive member is a surface of the heat radiating member facing the light guide member. It is characterized by being in contact with.

  According to said structure, since heat is spread | diffused by the heat conductive member, heat can be efficiently transmitted to a thermal radiation 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 light source holding member, heat dissipation 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.

  In the illuminating device of the present invention, it is preferable that a cross-sectional shape of the thermally conductive member in a plane perpendicular to both the light incident surface and the light emitting surface is L-shaped.

  Thereby, the illuminating device of this invention can transmit heat | fever more efficiently with respect to a thermal radiation member, and can further improve thermal radiation performance.

  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 illumination device of the present invention, it is preferable that the light source includes a substrate carrying a light emitting element.

  Thereby, as for the illuminating device of this invention, a light source becomes easy to be arrange | positioned on a light source holding member via a heat conductive member.

  In the lighting device of the present invention, it is preferable that the substrate is made of a heat conductive material, and the substrate is in contact with the heat dissipation member.

  According to said structure, since heat is spread | diffused by the board | substrate which is a heat conductive material, heat can be efficiently transmitted to a thermal radiation 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 board | substrate which is a heat conductive material is provided separately from the light source holding member, heat dissipation performance can be improved, maintaining structural strength.

  In addition, according to the above configuration, heat is diffused by the substrate that is a thermally conductive material, so that the heat distribution in the light source becomes uniform, and temperature variations in the light source can be reduced. As a result, the illumination device of the present invention can suppress uneven brightness of the light source.

  In the illumination device of the present invention, it is preferable that the cross-sectional shape of the substrate in a plane perpendicular to both the light incident surface and the light emitting surface is L-shaped.

  Thereby, the illuminating device of this invention can transmit heat | fever more efficiently with respect to a thermal radiation member, and can further improve thermal radiation performance.

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

  Thereby, as for the illuminating device of this invention, a board | substrate 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.

  Further, in the illumination device of the present invention, in the light source holding member, a thermal resistance per unit length in a direction along a contact surface between the light source holding member and the heat conductive member or the substrate is It is preferable that the thermal resistance per unit length in the direction along the contact surface between the light source holding member and the thermally conductive member or the substrate is smaller.

  Thereby, as for the illuminating device of this invention, the light source holding member can assist the heat conduction to the said direction in a board | substrate. As a result, in the lighting device of the present invention, the heat distribution on the substrate is made more uniform, and the unevenness in luminance of the light source can be further suppressed.

  The lighting device of the present invention is in a plane perpendicular to both the first surface where the light source holding member and the heat conductive member are in contact and the second surface where the light source holding member and the heat dissipation member are in contact. The cross-sectional shape of the light source holding member is preferably rectangular or square.

  Thereby, the illuminating device of this invention can enlarge the area of the said surface in a light source holding member. As a result, the illumination device of the present invention can reduce the thermal resistance per unit length in the direction along the contact surface between the light source holding member and the thermally conductive member or the substrate in the light source holding member. The heat conduction performance in can be improved.

  The lighting device of the present invention is in a plane perpendicular to both the first surface where the light source holding member and the heat conductive member are in contact and the second surface where the light source holding member and the heat dissipation member are in contact. The cross-sectional shape of the light source holding member is preferably L-shaped or U-shaped.

  Thereby, the illuminating device of this invention can reduce the volume of a light source holding member, hold | maintaining structural intensity | strength. As a result, the lighting device of the present invention can achieve weight reduction and cost reduction.

  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 illuminating device of the present invention has 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 source disposed toward the light incident surface. A light source holding member, and a heat dissipating member disposed on the back surface of the light guide member so as to face the light emitting surface, the light source holding member facing the light guide member, A surface facing the heat dissipation member, a surface facing the heat dissipation member is connected to a surface of the heat dissipation member facing the light guide member, and the light source is the light source holding member The heat conductive member is disposed on the surface facing the light guide member via the heat conductive member, and the heat conductive member is in contact with the surface of the heat radiating member facing the light guide member. It is.

  Therefore, the lighting device of the present invention has an effect that heat dissipation performance can be improved while maintaining structural strength, and luminance unevenness of the light source can be suppressed.

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

  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 the 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 emitting surface perpendicular to the light incident surface, and light incident on the light source. A light source holding member arranged toward the surface, and a heat radiating member arranged opposite to the light emitting surface on the back surface of the light guide member, the light source holding member comprising the heat radiating member The light source is disposed on a surface facing the light incident surface of the light source holding member via a heat conductive member, and the heat conductive member is in contact with the heat dissipation member. Yes. Here, the light guide member causes light from the light source disposed on the light source holding member to enter the light guide member from the light incident surface of the light guide member, and enters the light guide member. Light is emitted from the light exit 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 the light source holding member connected to the heat radiating member, which has a surface perpendicular to the light emitting surface of the light guide member, and its optical axis is directed to the inside of the light guide member. Yes. Here, the light source is disposed on the light source holding member via a 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 Is 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.

  The illuminating device in this embodiment may be provided with the housing | casing which consists of a heat radiating member. Moreover, in the illuminating device in this embodiment, the light source holding member is arrange | positioned on the heat radiating member as a structural reinforcement part.

  In the illumination device according to the present embodiment, the shape of the cross section of the thermally conductive member in a plane perpendicular to both the light incident surface and the light emitting surface is preferably L-shaped. 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. From the frame (light source holding member) 4 to be fixed, the chassis (heat radiating member) 5 connected to the frame 4, the heat conductive plate 6 disposed between the light source 7 and the frame 4 and connected to the chassis 5, and the light source 7 A light guide plate (light guide member) 22 for emitting incident light is 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. 1 to 6, 7, and 8, 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.

<Frame (light source holding member)>
The frame 4 used in the backlight device 1 of the present embodiment is not particularly limited as long as it has structural strength. Further, as the frame 4 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 4 used in the backlight device 1 of the present embodiment is a quadrangular prism shape having a rectangular or square cross section (the surface shown in FIGS. 3 and 4), or an L-shaped or U-shaped cross section. It has a polygonal column shape. The shape of the frame 4 will be specifically described below as “another embodiment”.

  The frame 4 has a surface perpendicular to the light exit surface of the light guide plate 22. Further, the frame 4 may or may not surround the light guide plate 22 with a surface perpendicular to the light emitting surface. Further, the frame 4 is preferably disposed as a structural reinforcing column at both ends of the chassis 5 so as to face two surfaces of the light guide plate 22 that are not adjacent to each other.

<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).

<Heat conductive plate (thermal conductive member)>
As the heat conductive plate 6 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 6 is preferably in the range of 200 W / m · K to 1000 W / m · K. When the thermal conductivity of the heat conducting plate 6 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 6 is larger than 1000 W / m · K, it is not preferable because of its high price, softness and difficulty in use, and 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.

  Moreover, as the heat conductive plate 6 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 heat conductivity of the heat conductive plate 6 used in the backlight device 1 of the present embodiment is larger than the heat conductivity of the frame 4 and the chassis 5. Moreover, as thickness of the heat conductive board 6, about 0.5-2 mm is preferable.

  The shape of the heat conductive plate 6 used in the backlight device 1 of the present embodiment is not particularly limited, and examples thereof include a planar shape shown in FIG. 3 and an L-shaped shape shown in FIG.

  Here, when the backlight device 1 shown in FIG. 3 is compared with the backlight device 1 shown in FIG. 4, in the backlight device 1 shown in FIG. 4, the chassis 5 and the heat conduction plate 6 are in contact with each other over a wide area. Therefore, the heat dissipation performance can be further improved.

<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.

<Relevance of each member>
The relevance of each member in the backlight device 1 of the present embodiment will be specifically described below with reference to FIG.

  As shown in FIG. 5, if the frame 4 has the function of the heat conduction plate 6 and the heat conduction plate 6 is omitted, the frame 4 has both the structural strength and the heat conductivity. Will have to. However, in general, it is difficult to make the two performances compatible. For example, the thermal conductivity of A5052, which is a general aluminum alloy (excellent in structural strength) as a structural member, is higher than that of SUS or the like, but is less than half that of C1100, which is pure copper. On the other hand, A1050, which is pure aluminum excellent in thermal conductivity, has insufficient strength to use as a structural member (inferior in structural strength). A1050 is inferior to A5052 in all respects: tensile strength, shear strength and yield strength. In addition, since A1050 is inferior in hardness, there is a problem that even if tapping is performed for screw fastening, the effect of tapping is actually easily lost. Therefore, in order to have both the performance of structural strength and thermal conductivity, the thermal conductive plate 6 is essential separately from the frame 4.

  Conversely, if the frame 4 is omitted and the structural strength is secured by the chassis 5 and only the heat conductive plate 6 is adopted from the viewpoint of thermal conductivity, it is a small and medium size panel such as a mobile phone and a car navigation system. Since the total amount of light required for the light source is small, there is a possibility that the two performances can be compatible. However, in large displays such as liquid crystal televisions and digital signage displays, the weight increases in terms of area. Therefore, if the structural strength can be maintained only by the chassis 5, the thickness of the chassis 5 is increased in proportion to the increase in size. Need to increase. In that case, it is not realistic in terms of weight, material cost, workability and the like. Therefore, the frame 4 is indispensable separately from the chassis 5 in order to achieve the structural strength by setting the chassis 5 to about 2 mm or less which is a realistic thickness.

  Accordingly, the structural strength is assigned to the frame 4 and the thermal conductivity is assigned to the thermal conductive plate 6 respectively, and the best performance as a whole can be exhibited by using optimal members for each.

  In addition, even with the same edge light type backlight, as the size of the backlight has increased, the long side of the four-sided incident light to the two-sided incident light and the two-sided incident light have a longer side from the upper and lower light incidents. If the left and right incident light and the form change, the thermal conditions become more severe due to the dense heat sources. For this reason, it is even more important to share the roles of the structural strength member and the heat conductive member as described above and to maximize the performance of each member.

<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. 7 (a) and 7 (b). 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 by the point light source 2 has a heat distribution 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 frame 4 via the heat conductive plate 6. The heat conductive plate 6 is formed of a material having high heat conductivity as described above. The frame 4 is a member that maintains structural strength, and thus has a larger cross-sectional area than the substrate 3. Therefore, the thermal resistance in the longitudinal direction of the frame 4 is smaller than that of the substrate 3, and sufficient thermal diffusion is performed in the heat conductive plate 6 and the frame 4. 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. 7A and 7B are cross-sectional views when heat sources 12 and 13 having different sizes are mounted on a certain heat conductor 11. Since the heat conductor 11 is the same in FIGS. 7A and 7B and has the same thermal conductivity, 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, the region contributing to heat conduction is narrower in the case of FIG. 7B than in the case of FIG. 7A, 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. 7B compared to the case of FIG. 7A 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. 7B than in the case of FIG. 7A, 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 the present embodiment, the heat transferred from the substrate 3 to the heat conducting plate 6 and the frame 4 is transferred to the chassis 5 in a state having a 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 conducting plate 6 is smaller than the thermal resistance in the planar direction of the chassis 5. Therefore, the heat dissipation performance 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.

<Other embodiments>
As another example of the backlight device 1 in the present embodiment, there is one in which the shape of the frame 4 is changed. Specifically, this will be specifically described with reference to FIGS. 8 (a) and 8 (b) and FIG.

  As shown in FIGS. 8A and 8B, the shape of the frame 4 is a polygonal column shape having a U-shaped cross section (the surface shown in FIGS. 3 and 4), or the frame as shown in FIG. By making the shape of 4 into a polygonal column shape having an L-shaped cross section, material costs can be reduced compared to a rectangular column shape having a rectangular or square cross section, and a U-shaped, L-shaped, etc. Thus, the mechanical strength can be increased by bending the flat plate.

  That is, in the illumination device of the present embodiment, a plane perpendicular to both the first surface where the light source holding member and the heat conductive member are in contact and the second surface where the light source holding member and the heat dissipation member are in contact with each other. The cross-sectional shape of the light source holding member is preferably rectangular or square. In the illumination device of the present embodiment, the plane is perpendicular to both the first surface where the light source holding member and the heat conductive member are in contact and the second surface where the light source holding member and the heat dissipation member are in contact. It is also preferable that the shape of the cross section of the light source holding member is L-shaped or U-shaped.

(II) Manufacturing method of lighting device in the present embodiment The manufacturing method of the lighting device in the present embodiment connects the light source 7 (the point light source 2 and the substrate 3), the heat conduction plate 6, the frame 4 and the chassis 5 in order. I will do it. 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 present embodiment will be described below 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.

  In the illuminating device according to the present embodiment, a light source, a light guide member having a light incident surface and a light emitting surface perpendicular to the light incident surface, and a light source holding member for arranging the light source toward the light incident surface And a heat radiating member disposed on the back surface of the light guide member so as to face the light emitting surface, the light source holding member is connected to the heat radiating member, and the light source is The light source holding member is disposed on a surface facing the light incident surface via a heat conductive member, the heat conductive member is in contact with the heat dissipation member, and the light source carries a light emitting element. A substrate is included, the substrate is made of a heat conductive material, and the substrate is in contact with the heat dissipation member, that is, the substrate is connected to the heat dissipation member.

  In the illumination device according to the present embodiment, the cross-sectional shape of the substrate in a plane perpendicular to both the light incident surface and the light emitting surface is preferably L-shaped. 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 substrate and the heat dissipation member in the substrate is such that the substrate and the heat dissipation member in the heat dissipation member The thermal resistance per unit length in the direction along the contact surface is preferably smaller. Further, in the illumination device according to the present embodiment, the thermal resistance per unit length in the direction along the contact surface between the light source holding member and the substrate in the light source holding member is the same as the light source holding member in the substrate. It is preferably smaller than the thermal resistance per unit length in the direction along the contact surface with the substrate.

  Compared with the illuminating device in the first embodiment described above, the illuminating device in the present embodiment has a “substrate 33 (thermal conductivity) included in the“ light source 8 ”as a thermally conductive member instead of the“ thermal conductive plate 6 ”. Made of a conductive material) is given thermal conductivity (similar to the thermal conductivity plate 6).

  Specifically, FIG. 10 is a schematic cross-sectional view showing a configuration of a liquid crystal display device (image display device) 30 including a backlight device (illumination device) 31 in the present embodiment. FIG. 11 is a perspective view showing a configuration in the vicinity of the light source 8 of the backlight device 31 in the present embodiment. 12 and 13 are cross-sectional views showing the configuration near the light source 8.

  As shown in FIGS. 10 to 13, the backlight device 31 in this embodiment mainly includes a light source 8 (a plurality of point light sources (light emitting elements) 2 and a substrate 33 on which the point light sources 2 are mounted), and a light source 8. A frame (light source holding member) 4 to be fixed, a chassis (heat radiating member) 5 connected to the frame 4, and a light guide plate (light guide member) 22 that emits light incident from the light source 8 are provided. The substrate 33 is connected to the chassis 5. As a means for connecting each member (component), in addition to screwing, for example, fixing with an adhesive tape, an adhesive, etc .; fitting;

<Light source (light emitting element and substrate)>
As the substrate 33 (made of a heat conductive material) on which the point light source 2 is mounted used in the backlight device 31 of the present embodiment, the point light source 2 can be mounted and the thermal conductivity is high. Use expensive ones. The thermal conductivity of the substrate 33 is preferably in the range of 200 W / m · K to 1000 W / m · K. When the thermal conductivity of the substrate 33 is less than 200 W / m · K, the heat conduction is insufficient and the heat does not spread to the heat dissipation member, so that the area contributing to heat dissipation is reduced and the heat dissipation performance is insufficient. It is not preferable for the reason. On the other hand, when the thermal conductivity of the substrate 33 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.

  Further, as the substrate 33 used in the backlight device 31 of the present embodiment, structural strength is not required, so a material having high thermal 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 substrate 33 used in the backlight device 31 of this embodiment is larger than the thermal conductivity of the frame 4 and the chassis 5.

  Although the shape of the board | substrate 33 used for the backlight apparatus 1 of this embodiment is not specifically limited, For example, the planar shape shown in FIG. 12, the L-shape shown in FIG. 13, etc. are mentioned.

  Here, comparing the backlight device 31 shown in FIG. 12 with the backlight device 31 shown in FIG. 13, in the backlight device 31 shown in FIG. 13, the chassis 5 and the substrate 33 are in contact with each other over a wide area. Therefore, the heat dissipation performance can be further improved.

<Method of heat conduction>
The present embodiment is different from the first embodiment described above in that the substrate 33 also serves as the heat conduction plate 6. The principle of improving the performance of heat conduction is basically the same as in the first embodiment. However, compared with Embodiment 1 mentioned above, since there is no heat conductive board 6, the number of interfaces reduces and heat conductivity can be improved more.

  Further, by adopting a configuration in which the thermal resistance in the longitudinal direction of the frame 4 is smaller than the thermal resistance in the longitudinal direction of the substrate 33, the heat distribution in the longitudinal direction of the substrate 33 can be made uniform. Thereby, the brightness nonuniformity in the backlight apparatus 31 resulting from the dispersion | variation in the temperature in LED can be suppressed. Furthermore, as compared with the substrate 3, heat is transmitted to the chassis 5 in a state where the heat distribution in the longitudinal direction of the substrate 33 is made uniform, so that good heat conduction and heat dissipation can be performed.

<Other embodiments>
Also in this embodiment, what changed the shape of the flame | frame 4 as another Example of the backlight apparatus 31 is mentioned. Specifically, as in FIGS. 8A and 8B, the shape of the frame 4 is a polygonal column shape having a U-shaped cross section (the surface shown in FIGS. 3 and 4), or FIG. Thus, by making the shape of the frame 4 into a polygonal column shape having an L-shaped cross section, the material cost can be reduced as compared with a quadrangular column shape having a rectangular or square cross section. The mechanical strength can be increased by bending the flat plate like a letter shape.

<The manufacturing method of the illuminating device in this embodiment>
Compared with the manufacturing method of the lighting device in the first embodiment, the manufacturing method of the lighting device in the present embodiment uses the “substrate 33” instead of the “substrate 3”, and uses the “heat conduction plate 6”. Except for this, it is the same as the manufacturing method of the lighting device in the first embodiment described above.

[Other Embodiments]
Note that the illumination device of the present embodiment is, for example, an edge light type backlight device that enters from the side, and includes a point light source, a substrate on which the point light source is mounted, a frame, a chassis, and heat conduction. Even if the board and the frame are in contact with each other through the heat conduction plate, the heat conduction plate and the frame are in contact, and the heat conduction plate and the chassis are in contact with each other. Good.

  Further, the lighting device of the present embodiment has a configuration in which, for example, the thermal resistance per unit length in the planar direction of the heat conducting plate is smaller than the thermal resistance per unit length in the planar direction of the chassis. May be.

  In addition, the illumination device of the present embodiment includes, for example, an edge light type backlight device that enters from the side, and includes a point light source, a substrate on which the point light source is mounted, a frame, and a chassis. A configuration in which the substrate and the frame are in contact with each other and the substrate and the chassis are in contact with each other may be employed.

  Further, the lighting device of the present embodiment may be configured such that, for example, the thermal resistance per unit length in the longitudinal direction of the frame is smaller than the thermal resistance per unit length in the longitudinal direction of the substrate. Good.

  Moreover, the structure with which the said flame | frame has a rectangular or square cross section in the cross section of a longitudinal direction may be sufficient as the illuminating device of this embodiment, for example.

  In addition, in the lighting device of the present embodiment, for example, the frame may have an L-shaped or U-shaped cross section in the longitudinal section.

  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 4 Frame (Light source holding member)
5 Chassis (heat dissipation member)
6 Thermal conductive plate (thermal conductive member)
7 Light source 8 Light source 10 Liquid crystal display device (image display device)
DESCRIPTION OF SYMBOLS 11 Heat conductor 12 Heat source 13 Heat source 21 Reflection sheet 22 Light guide plate (light guide member)
23 Optical sheet 24 Liquid crystal panel 25 Bezel (outer frame)
30 Liquid crystal display device (image display device)
31 Backlight device (lighting device)
33 Substrate

Claims (12)

A light source, a light guide member having a light incident surface and a light emitting surface perpendicular to the light incident surface, a light source holding member for arranging the light source toward the light incident surface, and the light guide member It has a heat dissipating member arranged on the back so as to face the light exit surface,
The light source holding member has a surface facing the light guide member and a surface facing the heat radiating member, and a surface facing the heat radiating member faces the light guide member of the heat radiating member. Connected to the surface to be
The light source is disposed on a surface of the light source holding member facing the light guide member via a heat conductive member,
The said heat conductive member is contacting the surface which opposes the said light guide member of the said heat radiating member, The illuminating device characterized by the above-mentioned.   2. The lighting device according to claim 1, wherein a cross-sectional shape of the thermally conductive member in a plane perpendicular to both the light incident surface and the light emitting surface is L-shaped.   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 2, wherein the lighting device is smaller than a thermal resistance per unit length in a direction along the contact surface.   The lighting device according to claim 1, wherein the light source includes a substrate carrying a light emitting element. The substrate is made of a heat conductive material,
The lighting device according to claim 4, wherein the substrate is in contact with the heat dissipation member.   6. The illumination device according to claim 5, wherein a cross-sectional shape of the substrate in a plane perpendicular to both the light incident surface and the light emitting surface is L-shaped.   The thermal resistance per unit length in the direction along the contact surface between the substrate and the heat dissipation member in the substrate is a unit length in the direction along the contact surface between the substrate and the heat dissipation member in the heat dissipation member. The lighting device according to claim 6, wherein the lighting device is smaller than a thermal resistance per unit.   In the light source holding member, the thermal resistance per unit length in the direction along the contact surface between the light source holding member and the heat conductive member or the substrate is the light source holding member and the heat conductivity in the substrate. The lighting device according to claim 4, wherein the lighting device is smaller than a thermal resistance per unit length in a direction along a contact surface with the member or the substrate.   The shape of the cross section of the light source holding member in a plane perpendicular to both the first surface where the light source holding member and the heat conductive member are in contact and the second surface where the light source holding member and the heat dissipation member are in contact Is a rectangle or a square, The illuminating device of any one of Claims 1-8 characterized by the above-mentioned.   The shape of the cross section of the light source holding member in a plane perpendicular to both the first surface where the light source holding member and the heat conductive member are in contact and the second surface where the light source holding member and the heat dissipation member are in contact The lighting device according to any one of claims 1 to 8, wherein the lighting device is L-shaped or U-shaped.   11. 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.

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