JP2008171797A - Backlight unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a backlight unit with an improved heat radiating property. <P>SOLUTION: The backlight unit is provided with a flexible substrate 200 with a light source 201, a light guide body 100 having an end surface facing a light emitting surface of the light source 201 and a case 300 having a concave portion housing all the above, and the flexible substrate 200 is bent and placed in the concave portion of the case 300. Especially, the flexible substrate 200 has a side end portion 202 where the light source 201 is placed and an extended portion 203 which is extended alongside a bottom surface of the concave portion. The side end portion 202 or the extended portion 203 is placed on an inside surface 301 and a bottom surface 302 of the case respectively, direct or through a thermal conductive member. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a backlight structure used in a liquid crystal display module or the like.

  A backlight unit used in a liquid crystal display module or the like includes a substrate on which a light source is disposed, a light guide having an end surface for receiving light from the light source, an optical sheet unit including a diffusion sheet and a prism sheet, and And a housing having a recess for housing the housing.

For example, the backlight unit described in Japanese Patent Application Laid-Open No. 2003-90993 has a flexible substrate (hereinafter sometimes referred to as “flexible substrate”) on which a light emitting diode is mounted in the direction of the end face of the light guide plate. By bending the light emitting diode, the light emitting surface of the light emitting diode faces the end surface of the light guide plate. This light emitting diode is configured by mounting an LED chip on a package, and an electrode provided in the package is soldered to a conductor wiring of a flexible substrate. Thereby, the light emitting diode is electrically and mechanically connected to the flexible substrate.
JP2003-90993A. JP 2004-214094 A. JP-A-2005-243267. JP 2006-308738 A.

  However, the heat radiation from the light emitting diode in the backlight unit is mainly from the side edge of the flexible substrate on which the light emitting diode is mounted to the side wall of the housing that the back of the side edge contacts. Therefore, it has become impossible to sufficiently dissipate the heat generated with the higher output of the light emitting diode.

  Further, when the flexible substrate on which the light emitting diode is mounted is arranged on the housing, the side end portion on which the light emitting diode is mounted is bent and held on the side wall of the housing, and the light emitting surface of the light emitting diode is placed on the light guide plate. Arrange it facing the light entrance. Here, the light emitting surface of the light emitting diode needs to be accurately aligned with the light incident portion of the light guide plate so that the light from the light emitting diode is incident on the light incident portion of the light guide plate without leaking. However, in the manufacturing process of the conventional backlight unit, it is troublesome to accurately align the light emitting surface of the light emitting diode arranged on the flexible flexible substrate and the light incident part of the light guide plate. The workability was reduced.

  Therefore, an object of the present invention is to provide a backlight unit with improved heat dissipation from a light source and easy to manufacture.

  In order to achieve the above object, a backlight unit according to the present invention includes a flexible substrate on which a light source is disposed, a light guide having an end surface on which a light emitting surface of the light source is faced, and the light guide. A backlight unit in which the flexible substrate is bent and disposed in the recess of the housing, wherein the flexible substrate is provided with the light source. A side end portion and an extension portion extending along the bottom surface of the recess, and the side end portion or the extension portion is directly or thermally applied to the inner side surface or the bottom surface of the casing. It arrange | positions through a transmission member, It is characterized by the above-mentioned.

  In the backlight unit according to the present invention, a metal flat plate is interposed between the back surface of the side end portion of the flexible substrate and the inner side surface of the casing, and the main surface of the metal flat plate is the side end. The light emitting surface of the light source is connected to the light incident part of the light guide disposed on the extension by connecting the side surface of the metal flat plate to the bottom surface of the housing. The backlight unit is positioned.

  In the backlight unit according to the present invention, the flexible substrate is formed by applying a conductor wiring to a sheet material made of resin, and the light source includes a light emitting element mounted on a package made of ceramics. A backlight unit in which the electrode of the package and the conductor wiring are connected by soldering.

  The backlight unit of the present invention is equipped with a high-output light source because heat can be radiated from the side end of the flexible substrate on which the light source is disposed toward the flexible substrate disposed on the bottom surface of the housing. It can be set as the backlight unit with high heat dissipation.

  In the backlight unit of the present invention, the light emitting surface of the light source and the light incident surface of the light guide plate are aligned with high accuracy, so that there is no light leakage and the backlight unit can be easily manufactured.

  The best mode for carrying out the present invention will be described below with reference to the drawings. However, the form shown below illustrates the backlight for materializing the technical idea of this invention, and this invention does not limit a backlight to the following.

  Further, the present specification by no means specifies the members shown in the claims to the members of the embodiments. The dimensions, materials, shapes, relative arrangements, and the like of the components described in the embodiments are not intended to limit the scope of the present invention only to the description unless otherwise specified. It is just an example. Note that the size, positional relationship, and the like of the members shown in each drawing may be exaggerated for clarity of explanation. Further, in the following description, the same name and reference sign indicate the same or the same members, and detailed description will be omitted as appropriate. Furthermore, each element constituting the present invention may be configured such that a plurality of elements are constituted by the same member and the plurality of elements are shared by one member, and conversely, the function of one member is constituted by a plurality of members. It can also be realized by sharing.

  FIG. 1 is a perspective view schematically showing each component of the backlight unit of the present embodiment. 2 to 4 are cross-sectional views of the backlight unit of this embodiment.

  The backlight unit of the present invention includes a flexible substrate 200 on which a light source 201 is disposed, a light guide body 100 having an end surface on which the light emitting surface of the light source 201 is faced, and a housing having a recess in which they are accommodated. 300, and the flexible substrate 200 is bent and disposed in the recess of the housing 300. In order to improve the heat dissipation of such a backlight unit, the present inventor has made various studies. As a result, the flexible substrate 200 has a side end portion 202 where the light source 201 is disposed, and an extension portion 203 extended along the bottom surface of the concave portion, and the side end portion 202. Alternatively, the extension 203 is arranged on the inner side surface 301 or the bottom surface 302 of the casing directly or via a heat transfer member, respectively, thereby solving the problem.

  That is, as shown in FIGS. 1 and 2, the backlight unit of the present invention bends the flexible substrate 200 on which the light source 201 is disposed, and extends from the inner side surface 301 to the bottom surface 302 of the recess of the housing 300. It is arranged. Furthermore, since the flexible substrate 200 is disposed on each inner wall surface of the housing 300 directly or via a heat transfer member, heat transfer from the flexible substrate to the housing is promoted. Thereby, heat can be obtained from the side end portion 202 of the flexible substrate 200 on which the light source 201 is disposed toward the extension portion 203 of the flexible substrate disposed on the bottom surface of the housing. Therefore, it can be set as the backlight unit with high heat dissipation which mounts the high output light source. In addition, the below-mentioned metal flat plate, a thermal radiation sheet, etc. can be utilized suitably as a heat transfer member in this form.

  The heat transfer member is interposed between at least one of the side end portion 202 of the flexible substrate 200 and the inner side surface of the housing or between the extension portion 203 of the flexible substrate and the bottom surface of the housing. Can do. Note that, of the side end portion 202 or the extension portion 203 of the flexible substrate 200, the side where the heat transfer member is not disposed is directly disposed on the inner wall surface (inner side surface or bottom surface) of the housing. The heat transfer member is thermally connected to each part of the flexible substrate 200, the inner wall surface including the inner side surface and the bottom surface of the housing, and at least a part of the surface. For example, as shown in FIG. 4, between the side end portion 202 of the flexible substrate 200 and the inner surface of the housing, and between the extension portion 203 of the flexible substrate 200 and the bottom surface of the housing. The metal flat plate 401 and the metal flat plate 402 can be disposed as heat transfer members, respectively. As the heat radiating member, a flexible sheet-like member or a non-flexible flat plate member can be used. Here, when the non-flexible flat plate is disposed on the side end portion 202 and the extension portion 203, a side plate is used so that the flexible substrate 200 can be easily bent, in addition to using a member in which the flat plate is previously bent. Preferably, a gap is provided between the flat plate of the portion 202 and the flat plate of the extension portion 203, or the flat plate of the side end portion 202 and the flat plate of the extension portion 203 are connected via a flexible member. .

  Further, as shown in FIG. 3, the backlight unit according to the present invention has a metal flat plate 400 interposed between the back surface of the side end portion 202 of the flexible substrate 200 and the inner side surface 301 of the housing 300. The main surface of the metal flat plate 400 is connected to the back surface of the side end portion 202, and the side surface of the metal flat plate 400 is in contact with the bottom surface 302 of the housing 300. The light emitting surface of the light source 201 is positioned on the light incident part of the light guide 100 arranged on the extension part 202 of the flexible substrate 200 by the metal flat plate 400. The metal flat plate 400 is made of aluminum, copper, iron, or an alloy thereof. Further, the metal flat plate 400 may be connected to the back surface of the flexible substrate 200 by various fixing methods so as not to be displaced from the flexible substrate 200. In addition, it is preferable to adhere to the back surface of the side end portion 202 of the flexible substrate 200 with an adhesive.

  The shape and size of the metal flat plate 400 are adjusted in advance so that the light emitting surface of the light source 201 arranged on the surface of the side end portion 202 of the flexible substrate 200 faces the light incident portion of the light guide 100. ing. In the manufacturing process of the backlight unit of the present invention, when the side end portion 202 of the flexible substrate 200 on which the light source 201 is arranged is arranged on the inner side surface 301 of the casing 300, the side surface of the metal flat plate 400 is moved by the own weight. A light source disposed on the main surface of the metal flat plate 400 is disposed at a predetermined position with respect to the light incident portion of the light guide 100. Thereby, it becomes easy to manufacture the backlight unit by accurately aligning the light emitting surface of the light source 201 and the light incident portion of the light guide 100. Further, the side end portion 202 of the flexible substrate 200 is supported by the housing 300 via the metal flat plate 400 even when the backlight unit is driven. Therefore, the optimal positional relationship between the light emitting surface of the light source and the light incident portion of the light guide can be maintained, and a backlight unit free from light leakage can be obtained.

  In the backlight unit according to the present invention, a flexible substrate 200 is obtained by applying a conductor wiring to a sheet material made of resin, and a light source 201 is mounted on a package made of ceramic material. The electrode of the package and the conductor wiring are connected by solder. That is, it is assumed that the package material is ceramic, the flexible substrate is a resin material sheet material, and the conductor wiring is applied. Thus, by selecting the material of each member, damage to the solder connecting the electrode of the light emitting diode and the flexible substrate can be suppressed. Hereinafter, each structure of this form is explained in full detail.

(light source)
The light source in this embodiment is a light emitting device that emits light that can be incident on a light guide, such as a semiconductor light emitting element such as a light emitting diode or a semiconductor laser, a cold cathode ray tube, or a composite light source that is selected and combined variously. Say. Regarding the arrangement of the light source on the light guide, it may be an edge light system in which a light source is arranged on the side end face of the light guide, or may be a direct type system in which a light source is arranged on the lower surface of the light guide. It is good also as a system using together.

  Hereinafter, although a light emitting diode is demonstrated, it is not limited to this. The light emitting diode can be variously selected depending on the dominant wavelength of light emitted from the semiconductor layer. In particular, light-emitting diodes that emit white mixed light are widely used. Such light-emitting diodes include various combinations of LED chips that emit RGB colors, light-emitting diodes including LED chips, and phosphors that emit light excited by light emitted from the LED chips. Things. An LED chip capable of emitting blue light can emit light with high brightness by using, for example, a gallium nitride compound semiconductor.

  In addition, the light emitting diode in this embodiment includes a package serving as a support for the LED chip. The electrode arranged in the package and the electrode of the LED chip are electrically connected by a conductive wire such as a gold wire or a conductive paste such as an Ag-containing epoxy resin. The LED chip and the conductive wire are covered with a light-transmitting resin such as an epoxy resin or a silicone resin, and are protected from the external environment.

  The package used in this embodiment is preferably a frame insert molded body having a recess in which an LED chip is disposed. Examples of the package material include epoxy resin, acrylic resin, PBT (polybutylene terephthalate), liquid crystal polymer, and aromatic nylon. And the like in which additives such as white pigment are mixed.

  As another package, a ceramic package obtained by laminating and firing ceramic green sheets can be obtained. Since the ceramic package is superior in heat resistance and light resistance as compared with a package made of a resin material, it can be a light emitting diode with high output and high reliability. For example, as disclosed in Japanese Patent Application Laid-Open No. 2006-308738, one of the side surfaces of a package made of ceramics can be mounted on a flexible substrate (flexible substrate) as a mounting surface.

Here, the translucent resin that covers the LED chip may contain a fluorescent material as necessary. The fluorescent material used in the present embodiment converts the wavelength of the LED chip light. That is, the fluorescent material absorbs at least a part of the light of the LED chip and emits light having a different wavelength. Here, the phosphor is preferably a phosphor that converts light from the LED chip to a longer wavelength side. When the light from the LED chip is high-energy short-wavelength visible light, YAG: Ce (for example, YAlO ₃ : Ce, Y ₃ Al ₅ O ₁₂ : Ce, etc.), which is a kind of aluminum oxide phosphor, or Eu Inorganic phosphors such as nitrogen-containing CaO—Al ₂ O ₃ —SiO ₂ activated by Cr and / or Cr are suitably used. In particular, the YAG: Ce phosphor absorbs part of the blue light from the LED chip depending on its content and emits yellow light that is a complementary color. Can be formed relatively easily.

(Flexible substrate)
The flexible board | substrate in this form is a flexible board | substrate with which conductor wiring was given on the sheet | seat which has flexibility. The conductor wiring is formed from a conductor for supplying power to the mounted light source. For example, it can be suitably formed by forming a conductive wiring pattern made of gold, silver or copper on a sheet of insulating resin such as polyimide film or liquid crystal polymer film. Or it can be set as the board | substrate with high heat dissipation by which the conductor wiring was given to the flexible metal plate which uses aluminum and copper as the main material through the insulating material. The flexible substrate is provided with conductor wiring from the side end portion where the light source is arranged to the extension portion arranged on the bottom surface of the housing, so that the flexible substrate is heated together with the electrical connection in the direction from the side end portion to the extension portion. It can also serve as a general connection. That is, the metal material of the conductor wiring can also promote heat dissipation from the side end portion of the flexible substrate toward the bottom surface of the housing. Moreover, it is preferable that a flexible board | substrate is closely_contact | adhered and arrange | positioned through a heat conductive member like a heat dissipation sheet. In addition, since the flexible substrate reflects light from the light source, it is preferable that a reflective sheet is provided on the surface of the flexible substrate or a light reflective material is disposed. Furthermore, the side edge part or extension part of a flexible board | substrate is extended and arrange | positioned to the magnitude | size which covers substantially the whole inner surface or bottom face of a housing | casing, respectively, and can improve heat dissipation.

(Light guide)
The light guide in this embodiment refers to a light which can guide light from a light source incident from a part of an end face by utilizing internal reflection and emit light in a desired shape from a predetermined light exit surface. It is an optical member. Therefore, various shapes such as a needle shape that can be used as a meter needle and a plate shape that can be used as a liquid crystal backlight light source can be used depending on the desired shape of the light emitting surface. The light guide has translucency in order to efficiently emit light from the light emitting diode or light obtained by wavelength conversion of the light from the light emitting surface. As a material for such a light guide, various materials such as acrylic resin, epoxy resin, and glass are preferably exemplified.

(Casing)
The housing in this embodiment has a recess that accommodates a mounting substrate on which a light source is arranged, a light guide, and an optical sheet portion including a diffusion sheet and a prism sheet, and a frame body at the opening of the recess. Is a member that holds and holds those members.

  As the material for the housing, various materials such as resins and metals containing various light diffusing agents are preferably exemplified. In particular, in consideration of heat dissipation and light reflection of a light emitting diode that generates heat, metals such as nickel, iron, copper, and aluminum, and various alloys such as stainless steel are more preferably used. The size and shape of the housing can be variously selected according to the size and shape of the member to be accommodated.

  Examples according to the present invention will be described in detail below. Needless to say, the present invention is not limited to the following examples.

  FIG. 3 is a cross-sectional view of the backlight unit of the present embodiment. The backlight unit of the present embodiment includes a flexible substrate 200 on which a light source 201 is disposed, a light guide plate 100 having a light incident portion facing a light emitting surface of the light source 201, and a housing having a recess in which they are accommodated. The flexible substrate 200 is bent and disposed in the concave portion of the housing 300. Further, the flexible substrate 200 includes a side end portion 202 where the light source 201 is disposed, and a bent portion disposed at a corner portion of the recess formed by the inner surface and the bottom surface of the recess where the side end portion 202 is disposed. And an extension 203 arranged to extend from the bent portion to the bottom surface 302 of the recess. Here, a metal flat plate 400 is interposed between the side end portion 202 and the inner side surface 301 of the housing 300. The metal flat plate 400 is made of corrosion-resistant aluminum and is bonded to the back surface of the side end portion 202 with an adhesive. Further, the extension 203 of the flexible substrate 200 is directly disposed on the bottom surface 302 of the housing 300. The side surface of the metal flat plate 400 is in contact with the bottom surface 302 of the housing 300, and the light source 201 disposed on the side end portion 202 is positioned on the light incident portion of the light guide plate 100 disposed on the extension portion 203. Has been.

  The light source of the present embodiment is a light emitting diode in which a light emitting element and a fluorescent material are mounted in a ceramic package, and emits white light by color mixture of light from the light emitting element and fluorescence by the light. Further, the light emitting diode is soldered to the conductor wiring of the side end portion 202 of the flexible substrate 200.

  FIG. 4 is a cross-sectional view of the backlight unit of the present embodiment. The backlight unit of the present embodiment includes a flexible substrate 200 on which a light source 201 is disposed, a light guide plate 100 having a light incident portion facing a light emitting surface of the light source 201, and a housing having a recess in which they are accommodated. A flexible substrate 200 with metal flat plates 401 and 402 bonded to the back surface thereof is bent and disposed in a recess of the housing 300. Further, the flexible substrate 200 has a side end portion 202 where the light source 201 is disposed, and an extension portion 203 disposed so as to extend to the bottom surface 302 of the recess.

  In the backlight unit of the present embodiment, a first metal flat plate 401 is interposed between the side end portion 202 and the inner side surface 301 of the housing 300, and further, the extension portion 203 and the bottom surface 302 of the housing 300. Between the two, a second metal flat plate 402 is interposed. These metal flat plates 401 and 402 are made of aluminum, and are adhered to the side end portion 202 of the flexible substrate 200 and the back surface of the extension portion 203 by an adhesive. In addition, a gap is provided between the side end portion of the first metal flat plate 401 and the side end portion of the second metal flat plate 402 facing the side end portion, and the flexible substrate 200 is provided in the gap. The corresponding bent portion is supported.

  In the backlight unit of this embodiment, the flexible substrate 200 with the metal flat plates 401 and 402 bonded to the back surface is bent and disposed in the concave portion of the casing 300, and these metal flat plates improve heat dissipation. be able to.

  INDUSTRIAL APPLICABILITY The present invention can be used as an in-vehicle liquid crystal display device or a large display as a backlight unit with improved heat dissipation.

FIG. 1 is a perspective view schematically showing one embodiment of a backlight unit according to the present invention. FIG. 2 is a cross-sectional view schematically showing one embodiment of a backlight unit according to the present invention. FIG. 3 is a cross-sectional view schematically showing one embodiment of a backlight unit according to the present invention. FIG. 4 is a cross-sectional view schematically showing one embodiment of a backlight unit according to the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 ... Light guide plate 200 ... Flexible board | substrate 201 ... Light source 202 ... Side edge part 203 ... Extension part 300 ... Case 301 ... Inner side surface 302 ... Bottom surface 400 401, 402 ... Metal flat plate

Claims (3)

A flexible substrate on which a light source is disposed, a light guide having an end surface facing a light emitting surface of the light source, and a housing having a recess in which they are accommodated. Is a backlight unit that is bent and disposed in the recess of the housing,
The flexible substrate has a side end portion on which the light source is disposed and an extension portion extended to the bottom surface of the concave portion, and the side end portion or the extension portion respectively corresponds to the casing. The backlight unit is arranged directly or via a heat transfer member on the inner surface or bottom surface of the backlight unit. A metal flat plate is interposed between the back surface of the side end portion of the flexible substrate and the inner surface of the housing,
The main surface of the metal flat plate is connected to the back surface of the side end portion, and the side surface of the metal flat plate is brought into contact with the bottom surface of the housing, whereby the light emitting surface of the light source is disposed on the extension portion. The backlight unit according to claim 1, wherein the backlight unit is positioned at a light incident portion of the light guide.   The flexible substrate is formed by applying a conductor wiring to a sheet material made of a resin, and the light source is a light emitting diode in which a light emitting element is mounted on a package made of a ceramic material. The backlight unit according to claim 1, wherein the electrode and the conductor wiring are connected by solder.

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