JP2012014947A - 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 reducing cost.SOLUTION: A light source retention member 4 has its face opposed to a heat dissipation member 5 connected to a face opposed to a light guide member 22 of the heat dissipation member 5. A thermally conductive member 6 is provided with a first plate-shaped part in contact with a face opposed to the light guide member 22 of the light source retention member 4, and a second plate-shaped part in contact with a face opposed to the light guide member 22 of the heat dissipation member 5. Light sources 7 are arranged on a face of the light source retention member 4 opposed to a light-incident face through the first plate-shaped part, and the light source retention part 4 is provided with a third plate-shaped part in contact with a rear face of the first plate-shaped part opposed to the light guide member 22, and a fourth plate-shaped part in contact with a face of the heat dissipation member 5 opposed to the light guide member 22. The second plate-shaped part and the fourth plate-shaped part are formed in adjacency to the first plate-shaped part and the third plate-shaped part, respectively, by a bending process.

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. 7, a cylindrical housing formed by one end surface of the light guide plate 122, the frame 104, and the heat radiating plate 105 includes a light source unit (backlight device) 101. The light source unit 101 is configured to be detachable in the first direction, the light source unit 101 includes a light emitting diode 102, a film substrate 103 on which a plurality of light emitting diodes 102 are mounted side by side in the first direction, a support unit that supports the film substrate 103, and A heat dissipation member 106 having a reflective portion extending in a second direction orthogonal to the first direction from the support portion, and an adhesive tape that adheres the film substrate 103 to the support portion and has heat dissipation properties, and is inserted into the accommodating portion In this state, the light emitting surface of the light emitting diode 102 faces the one end surface of the light guide plate 122, and the reflecting portion of the heat radiating member 106 and the heat radiating plate 105 are The liquid crystal display device 110 having a light source unit 101 to touch are shown. Patent Document 2 discloses a backlight device having a heat radiation fin.

JP 2010-9787 A (published January 14, 2010) JP 2001-44517 A (published February 16, 2001)

  However, the liquid crystal display device disclosed in Patent Document 1 has a problem that the cost cannot be reduced. Further, the backlight device disclosed in Patent Document 2 has a problem that heat dissipation performance cannot be improved while maintaining structural strength.

  The present invention has been made in view of the above-described conventional problems, and an object of the present invention is to provide a lighting device capable of improving heat dissipation performance while maintaining structural strength and reducing cost. And providing an image display apparatus including the same.

  In view of the above problems, the present inventors have intensively studied the reason why the cost cannot be reduced in the liquid crystal display device disclosed in Patent Document 1. As a result, in the liquid crystal display device disclosed in Patent Document 1, since the cross-sectional shape includes a T-shaped prismatic frame, extrusion molding is required for manufacturing the prismatic frame, and screw holes are formed. It has been found that the manufacturing cost increases because it is post-processing.

  The inventors of the present invention use a frame formed by bending a flat plate (sheet metal processing) to bring the frame into contact with a heat radiating member and a heat conductive member while maintaining structural strength. The inventors have found that the heat dissipation performance can be improved and the cost can be reduced, 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 emitting surface perpendicular to the light incident surface, and the light source as a light incident surface. A light source holding member to be disposed toward the heat radiation member, a heat radiating member disposed on the back surface of the light guide member to face the light emitting surface, and heat in contact with the light source holding member and the heat radiating member. The light source holding member has a surface facing the light guide member and a surface facing the heat radiating member, and the surface facing the heat radiating member is the heat radiating member. The heat conductive member is connected to a surface facing the light guide member, and the heat conductive member is a first plate-like portion in contact with the surface facing the light guide member of the light source holding member, and It has a second plate-like portion that contacts the surface of the heat dissipation member facing the light guide member. The light source is disposed on a surface of the light source holding member facing the light incident surface via a first plate-like part, and the light source holding member is arranged on the first plate-like part. A third plate-shaped portion in contact with the back surface of the surface facing the optical member, and a fourth plate-shaped portion in contact with the surface of the heat dissipation member facing the light guide member, The plate-like portion and the fourth plate-like portion are formed adjacent to the first plate-like portion and the third plate-like portion, respectively, by bending.

  According to said structure, since heat is spread | diffused by a heat conductive member, the heat distribution in a light source holding member and a heat radiating member becomes uniform, and heat can be efficiently transmitted to a 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 and the light source holding member, the heat radiating performance can be improved while maintaining the 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.

  Further, according to the above configuration, in the heat conductive member, the second plate-shaped portion is formed adjacent to the first plate-shaped portion by bending, and the fourth plate-shaped portion is bent in the light source holding member. It is formed adjacent to the third plate-like part by processing. As a result, the lighting device of the present invention can reduce the cost.

  In the illuminating device of the present invention, it is preferable that a cross-sectional shape of the light source holding member in a plane perpendicular to both the light incident surface and the light emitting surface is 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 further cost reduction. Furthermore, the illuminating device of the present invention can further improve the heat dissipation performance by the L-shaped or U-shaped space portion.

  Moreover, it is preferable that the 3rd plate-shaped part is contacting the said light source in the illuminating device of this invention.

  Thereby, the illuminating device of this invention can conduct heat from the several surface in a light source, and can make favorable heat conduction from a light source to a thermal radiation member.

  In the illumination 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 an L shape or a U shape. .

  Thereby, the illuminating device of this invention can aim at weight reduction and the further 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, a heat radiating member disposed on the back surface of the light guide member to face the light emitting surface, and a heat conductive member in contact with the light source holding member and the heat radiating member. The light source holding member has a surface facing the light guide member and a surface facing the heat radiating member, and the surface facing the heat radiating member is the light guide member of the heat radiating member. The heat conductive member is connected to a surface of the light source holding member in contact with a surface of the light source holding member facing the light guide member, and The second light source has a second plate-like portion in contact with the surface facing the optical member, and the light source is The light source holding member is disposed on the surface facing the light incident surface via the first plate-like portion, and the light source holding member is the surface of the first plate-like portion facing the light guide member. A third plate-shaped portion in contact with the back surface of the heat-dissipating member, and a fourth plate-shaped portion in contact with the surface of the heat radiating member facing the light guide member. The portions are formed adjacent to the first plate portion and the third plate portion by bending.

  Therefore, the lighting device of the present invention can improve the heat dissipation performance while maintaining the structural strength, can suppress the luminance unevenness of the light source, and can reduce the cost. .

It is sectional drawing which shows schematic structure of the liquid crystal display device provided with the backlight apparatus in one Embodiment of this invention. (A)-(c) is sectional drawing which shows the structure of the light source vicinity of the backlight apparatus in one Embodiment of this invention. (A)-(c) is sectional drawing which shows the structure of the light source vicinity of the backlight apparatus in one Embodiment of this invention. It is sectional drawing which shows the structure of the light source vicinity of the conventional backlight apparatus. 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. It is sectional drawing which shows schematic structure of the liquid crystal display device provided with the conventional backlight apparatus.

  One embodiment of the present invention will be described in detail below, but the scope of the present invention is not limited to these explanations, and modifications other than the following exemplifications are made as appropriate without departing from the spirit of the present invention. Can be implemented.

(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 to be arranged toward the surface, a heat radiating member arranged to face the light emitting surface on the back surface of the light guide member, and the light source holding member and the heat radiating member in contact with each other. A heat conductive member is provided, and the light source holding member has a surface facing the light guide member and a surface facing the heat dissipation member, and the surface facing the heat dissipation member is the heat dissipation member. A first plate-like portion that is connected to a surface of the member facing the light guide member, and the heat conductive member is in contact with a surface of the light source holding member facing the light guide member; and A second surface of the heat dissipating member in contact with the surface facing the light guide member; The light source is disposed on a surface of the light source holding member facing the light incident surface via a first plate portion, and the light source holding member is a first plate. A third plate-shaped portion in contact with the back surface of the surface facing the light guide member, and a fourth plate-shaped portion in contact with the surface of the heat dissipation member facing the light guide member. The second plate portion and the fourth plate portion are formed adjacent to the first plate portion and the third plate portion by bending, respectively. 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 the optical axis thereof is guided. It is directed to the inside of the optical member. Here, since the light source is disposed on the light source holding member via the heat conductive member, the amount of heat generated by the light source is successfully transmitted to the heat radiating member, and from the heat radiating member to the outside of the apparatus. The amount of heat is released. Moreover, the said heat conductive member has the 1st plate-shaped part raised by the bending process from the 2nd plate-shaped part couple | bonded with the said heat radiating member, and a 2nd plate-shaped part. The light source holding member includes a fourth plate-like portion that is coupled to the heat dissipation member, and a third plate-like portion that is raised from the fourth plate-like portion by bending.

  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 this embodiment, the shape of the cross section of the light source holding member on a plane perpendicular to both the light incident surface and the light emitting surface is preferably L-shaped or U-shaped. . Moreover, as for the illuminating device in this embodiment, it is preferable that the 3rd plate-shaped part is contacting the said light source. In the illumination device according to the present embodiment, the cross-sectional shape of the thermally conductive member on a plane perpendicular to both the light incident surface and the light emitting surface is L-shaped or U-shaped. preferable.

  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. FIGS. 2A to 2C and FIGS. 3A to 3C are cross-sectional views showing a configuration in the vicinity of the light source 7 of the backlight device 1 in the present embodiment.

  As shown in FIGS. 1 to 3, the backlight device 1 in the present 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. 1 is described using the backlight device 1 shown in FIG. 2B, the “backlight device 1 shown in FIG. 2B” is replaced with “FIG. (C) or the backlight device 1 ”shown in FIGS. 3A to 3C is also included in this embodiment.

  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, 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 (light source substrate, light emitting 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 material of 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 frame 4 used in the backlight device 1 of the present embodiment includes a third plate-like portion that contacts the back surface of the surface of the first plate-like portion of the heat conducting plate 6 facing the light guide plate 22, and the chassis 5. The fourth plate portion is in contact with the surface facing the light guide plate 22, and the fourth plate portion is formed adjacent to the third plate portion by bending. Further, the frame 4 used in the backlight device 1 of the present embodiment has a cross-sectional shape (surface shown in FIGS. 2 and 3) in a plane perpendicular to both the light incident surface and the light emitting surface of the light guide plate 22. L-shaped as shown in FIGS. 2 (c) and 3 (c), or U-shaped as shown in FIGS. 2 (a), 2 (b), 3 (a), and 3 (b). Is preferred. That is, it is preferable that the frame 4 used in the backlight device 1 of the present embodiment is partially cut from the shape shown in FIG.

  By making the shape of the frame 4 into a polygonal column shape having an L-shaped or U-shaped cross section, material costs can be reduced compared to a rectangular column shape having a rectangular or square cross section. The mechanical strength can be increased by bending a flat plate such as an L shape.

  The frame 4 used in the backlight device 1 of the present embodiment may be wavy. Thereby, intensity | strength can be raised.

  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 material of 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 heat conductive plate 6 used in the backlight device 1 of the present embodiment is opposed to the light guide plate 22 of the first plate-like portion in contact with the surface of the frame 4 facing the light guide plate 22 and the chassis 5. A second plate-like portion in contact with the surface. Further, the heat conductive plate 6 used in the backlight device 1 of the present embodiment has a cross-sectional shape (surface shown in FIGS. 2 and 3) in a plane perpendicular to both the light incident surface and the light emitting surface of the light guide plate 22. Is preferably L-shaped as shown in FIGS. 2 (a) to 2 (c) or U-shaped as shown in FIGS. 3 (a) to 3 (c). In the U-shaped shape of the heat conducting plate 6 shown in FIGS. 3A to 3C, the length of the upper side (the liquid crystal panel 24 side) is the length of the lower side (chassis 5 side). It may be shorter or the same as the length.

  The heat conductive plate 6 used in the backlight device 1 of the present embodiment may be subjected to wave processing. Thereby, intensity | strength can be raised.

<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. 6 (a) and 6 (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. 6A and 6B 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. 6A and 6B 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, the region contributing to heat conduction is narrower in the case of FIG. 6B than in the case of FIG. 6A, and heat concentrates in a narrow area. Since the thermal resistance per unit area in the thermal conductor 11 is equal, in the case of FIG. 6B compared to the case of FIG. 6A, the thermal resistance increases because the area contributing to heat conduction is small. Accordingly, it can be seen that the temperature difference between the upper and lower sides of the heat conductor 11 becomes larger in the case of FIG. 6B than in the case of FIG.

  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.

(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;

(III) Modified Example of the Present Embodiment The illumination device of the present embodiment may be configured such that, for example, a member that supports the light emitting substrate of the sidelight type backlight is configured by two L-shaped members. .

  Moreover, the structure which pinched | interposed the light emission board | substrate with the L-shaped member may be sufficient as the illuminating device of this embodiment, for example.

  Moreover, the structure by which the L-shaped member is produced by the bending process may be sufficient as the illuminating device of this embodiment, for example.

  The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope shown in the claims. That is, embodiments obtained by combining technical means appropriately modified within the scope of the claims are 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 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)

Claims (6)

A light source, a light guide member having a light incident surface and a light exit surface perpendicular to the light incident surface, a light source holding member for disposing the light source toward the light incident surface, and a back surface of the light guide member A heat dissipating member disposed to face the light emitting surface, and a heat conductive member in contact with the light source holding member and the heat dissipating member,
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 heat conductive member is in contact with a first plate-like portion that is in contact with a surface of the light source holding member that faces the light guide member, and a surface of the heat dissipation member that is opposed to the light guide member. Has a second plate-like part,
The light source is disposed on a surface of the light source holding member facing the light incident surface via a first plate-shaped portion,
The light source holding member includes a third plate-shaped portion that is in contact with the back surface of the first plate-shaped portion that faces the light guide member, and a surface of the heat dissipation member that faces the light guide member. Has a fourth plate-shaped part in contact with
The second plate-like portion and the fourth plate-like portion are formed adjacent to the first plate-like portion and the third plate-like portion, respectively, by bending.   2. The illumination device according to claim 1, wherein a shape of a cross section of the light source holding member in a plane perpendicular to both the light incident surface and the light emitting surface is L-shaped or U-shaped. .   The lighting device according to claim 1, wherein the third plate-like portion is in contact with the light source.   The 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 or U-shaped. The lighting device according to claim 1.   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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