JP2007041476A - Backlight - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To attain high reliability and high luminance of a backlight using a light source constituted of a light emitting element array module. <P>SOLUTION: In a light source part 480 of the backlight wherein a light emitting element array module 420 formed by arranging a plurality of light emitting elements 421 on a oblong substrate along the longitudinal direction thereof and sealing the light emitting elements by using a transparent material 424 is mounted on a wiring board and a reflection plate 440 is disposed on both sides of the light emitting element array module, a shape deformable transparent member 400 is disposed so as to closely adhere to both of a light outputting part of the light emitting element array module 420 and an incident surface 411 of a light guide plate 410, a reflection member 431 is added onto a side surface of the transparent member and the light source part 480 is fixed directly to an outer case 490 which is separate from a frame 460 supporting the light guide plate 410 and has satisfactory thermal conductivity. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a liquid crystal display device, and more particularly to a backlight that illuminates a liquid crystal panel from the back side.

  Thin and lightweight liquid crystal displays capable of displaying images have rapidly spread due to price reduction and development of high image quality technology due to progress in manufacturing technology, and are widely used in personal computer monitors, TV receivers, and the like.

  A transmissive liquid crystal display device is generally used as the liquid crystal display device. The transmissive liquid crystal display device includes a planar light source called a backlight, and forms an image by spatially modulating illumination light from the light source using a liquid crystal panel.

  As the backlight, a backlight that uses a cold cathode tube, which is a substantially linear light source, and is incident from the side surface of a thin light guide plate is often used. The basic configuration is shown in FIG. FIG. 5A is a front view of a backlight using a conventional cold cathode ray tube observed from the exit surface side, and FIG. 5B is a cross-sectional view thereof.

  The light incident on the side surface 111 of the light guide plate 110 from the cold cathode ray tube 120 propagates while repeating total reflection between the opposing main surfaces. A part of the propagating light is emitted by forming a diffuse reflection layer or reflection unevenness having a specific density distribution and size on the surface of the reflection surface 113 which is the opposite surface of the emission surface 112. By appropriately setting the density distribution, the size distribution, etc. that form the diffuse reflection layer or the reflection unevenness, it is possible to perform almost uniform illumination over the entire surface of the liquid crystal panel. By providing the reflection sheet 140 on the reflection surface 113 side of the light guide plate 110, a part of light leaking from the reflection surface to the outside of the light guide plate is reflected to the light guide plate side to prevent light loss. In addition, in order to illuminate a liquid crystal panel (not shown) with desired light distribution characteristics by controlling the directivity of light emitted from the backlight, a diffusion film, a prism sheet, or the like is provided on the light exit surface 112 side of the light guide plate 110. The optical film 150 is generally installed.

  At this time, a reflector 130 surrounding the cold cathode ray tube 120 and opening toward the incident surface 111 of the light guide plate 110 is provided. As a result, the light emitted from the cold cathode ray tube can be guided to the light guide plate without any excess.

  Recently, a light emitting diode (hereinafter referred to as LED) having high luminous efficiency has been developed, and it has been proposed to use it as a light source for a liquid crystal backlight.

  As a method for obtaining planar light emission that can be used as a backlight from an LED that is a point light source, a method in which a large number of LEDs are arranged on an end surface of a light guide plate and light is directly input is generally used. An example is shown in FIG.

  FIG. 6 is a diagram showing a configuration of a method using an LED light-emitting element called a side emitter type in which a light-emitting element itself is provided with a box-like reflecting member. FIG. 6A shows a main part centering on a light source part. FIG. 6B is a partial cross-sectional view showing the light source unit as seen from the light guide plate. In FIG. 6B, the transparent sealing resin portion is omitted.

  An LED chip 221 is bonded on the element substrate 222, a reflective member 223 is provided around the LED chip 221 and sealed with a transparent sealing resin 224, and a side emitter type LED light source element 220 having a connection electrode 225 is provided as a wiring board. Arrange on 270 and connect.

  This light source unit is fixed on the frame 260 so that the openings of the plurality of side emitter LED elements 220 face each other in close proximity to the incident surface 211 of the light guide plate 210.

  With this configuration, the emitted light can be guided to the light guide plate while the light source unit is stably held at a predetermined position facing the light guide plate.

  Furthermore, a method of using a light emitting element array module in which a plurality of light emitting elements are linearly arranged on one substrate and sealed has been proposed (see, for example, Patent Document 1). The pattern is shown in FIG. FIG. 7 is a diagram showing a configuration of a method using a light emitting element array module. FIG. 7A is a cross-sectional view showing a main part centering on the light source part, and FIG. It is the front view seen from. In FIG. 7B, the transparent sealing resin portion is omitted.

  The light emitting element array module 320 has a configuration in which a plurality of light emitting elements 321 are linearly arranged on a module substrate 322 and sealed with a transparent sealing resin 324. Such an array module can be efficiently produced by arranging and sealing light emitting elements in a matrix on one large substrate and then cutting it. In general, the light emitting element array module is firmly fixed to the wiring board 370, and the wiring board is fixed to the frame 360 holding the light guide plate, thereby easily positioning the incident surface 311 of the light guide plate and the light emitting element array module. I have to.

  The resin sealing portion 324 of the light emitting element array module 320 produced by the above method has a rectangular cross section, and light can be emitted not only from the surface facing the module substrate 322 but also from the side surface adjacent thereto. It becomes a light emitting part. A reflective member 330 is provided on the side surface. Accordingly, it is possible to prevent light from leaking from the side surface portion of the light emitting element array module to a portion other than the incident surface 311 of the light guide plate 310.

When the light emitting element array module is used in this way, it is possible to expect great effects such as reduction in manufacturing cost and simplification of wiring compared to the case of using LED light source elements in which the light emitting elements are individually sealed.
JP 2004-235139 A

  Recently, a brighter backlight is demanded. Therefore, since the light emitting element is driven with high luminance, the light emitting element generates a large amount of heat. However, the conventional structure shown in FIG. 7 is not necessarily able to efficiently dissipate heat generated in the light emitting element.

  Generally, epoxy that is transparent and has excellent heat resistance and weather resistance is used for sealing the light emitting element, but its heat conductivity is poor and the heat dissipation effect due to heat generation of the light emitting element is not sufficient. Therefore, it is preferable that heat dissipation of the light emitting element is performed mainly from the array module substrate to the wiring substrate.

  However, since the wiring board is generally fixed to a frame made of a resin material that holds the light guide plate, the heat of the wiring board is not sufficiently transmitted to the frame. Even if the module board and wiring board are made of a material with good thermal conductivity, the thermal conductivity is poor at the tip of the wiring board. Eventually, if the light emitting element is driven with high brightness, the light emitting element becomes hot and the luminous efficiency There was a problem that reliability was lowered.

  In view of the above-described problems, an object of the present invention is to provide a compact and bright liquid crystal display device that realizes a backlight with high light utilization efficiency while driving a light emitting element with high luminance.

  The object described above is achieved by the following backlight. A light guide plate that is substantially flat and emits light introduced from the incident surface of the side surface from one of the opposed two main surfaces to illuminate the surface, and on the elongated substrate along the longitudinal direction thereof. A light source part in which a light emitting element array module in which a plurality of arranged light emitting elements are sealed with a transparent material to form a light emitting part is mounted on a wiring board, and reflectors are disposed on both sides of the light emitting element array module; A transparent member that is deformable so as to be in close contact with both the light emitting portion of the light emitting element array module and the incident surface of the light guide plate, and is disposed on a side surface of the transparent member. A backlight having a reflecting member added thereto, wherein the light source unit is directly fixed and installed in an exterior case different from a frame supporting the light guide plate.

  According to the present invention, since the light emitting element array module is tightly fixed to the outer case having good thermal conductivity via the closely connected wiring board, the heat generated in the light emitting element can be efficiently radiated to the outside. For this reason, even if the light emitting element is driven with high luminance, the temperature rise of the light emitting element can be suppressed low, and a light source with high luminance and high reliability can be provided. In addition, since the light emitting element array module is fixed to an outer case different from the frame that holds the light guide plate, the relative positioning accuracy of the light guide plate incident surface and the light output portion of the light emitting element array module may be reduced. However, by arranging a transparent member that can be deformed so as to be in close contact with both sides and to which a reflecting member is added, the light from the light emitting element array module can be removed even if the relative positioning accuracy is somewhat reduced. Can be efficiently transmitted to the entrance surface of the light guide plate without leaking.

(Embodiment 1)
FIG. 1 shows the first embodiment of the backlight of the present invention, and FIG. 2 shows the configuration of the light source section and the light emitting element array module. FIG. 2A is a front view of the light source section viewed from the incident surface side of the light guide plate, and FIG. 2B is a cross-sectional view taken along the line XX ′.

  In the light emitting element array module 420 of the light source unit 480, as shown in FIG. 2A, a plurality of light emitting elements 421 are arranged and connected on an elongated rectangular module substrate 422, and the light emitting elements are shown in FIG. As shown in b), the structure is sealed with a transparent sealing resin 424.

  In the light source unit 480, the light emitting element array module 420 is firmly fixed on the wiring board 470, and the reflectors 440 are arranged on both sides along the light emitting element array module 420.

  This embodiment is a backlight using the light source unit 480, and the configuration and operation thereof will be described with reference to FIG. The light emitting part of the light emitting element array module 420 and the light incident surface 411 of the light guide plate 410 are arranged to face each other with a certain distance. On the frame 460, the reflection sheet 445, the light guide plate 410, the prism sheet 450, and the diffusion sheet 455 are laminated in this order.

  The reflection sheet 445 is a white PET sheet. The prism sheet 450 is formed by using a transparent PET sheet as a base material and a fine prism array is formed on one surface thereof using an ultraviolet curable resin or the like. There is an effect of guiding the light from the light plate 410 to the front direction and brightening the front direction. Further, the transparent shape is deformable so that the light emitted from the light emitting element array module 420 is in close contact with both the light emitting part of the light emitting element array module 420 and the incident surface 411 of the light guide plate 410 so that the light does not leak outside the light guide plate incident surface. The reflective member 431 is added to the side surface of the transparent member 400.

  Here, a conventional backlight will be described. A conventional light source unit 380 shown in FIG. 7 is fixed to a frame 360 that supports the light guide plate 310. For this reason, the light from the light source unit 380 needs to be relatively positioned in order to efficiently enter the light incident surface 311 of the light guide plate 310. For this purpose, the light guide plate is placed on the same frame 360. This is because the structure for fixing 310 and the light source unit 380 is suitable for relative positioning. In general, the frame 360 is often a resin material in terms of the weight and cost of the final product. In this case, heat generated in the light emitting element of the light source unit 380 is transmitted to the module substrate 322 and the wiring substrate 370, but the resin frame 360 has a poor heat dissipation property because the heat conductivity is not good. . For this reason, it is not suitable for increasing the luminance of the light source.

  On the other hand, as is apparent from FIG. 1, the present invention has a structure in which the light source unit 480 is fixed in close contact with the outer case 490. Therefore, the heat generated in the light emitting element 421 is transmitted to the module substrate 422, the wiring substrate 470, and the exterior case 490, and is efficiently dissipated outside the system. Therefore, higher brightness and higher reliability are possible.

  Here, the outer case 490 is preferably a metal material having good thermal conductivity. Furthermore, the feature of this embodiment is that the transparent member 400 is formed of a member that can be deformed. As described above, in the present embodiment, the support structure (corresponding to the frame 460) of the light guide plate 410 and the structure (corresponding to the exterior case 490) for fixing the light source unit 480 are different. Deviations are likely to occur in relative positioning. A transparent member 400 that can be deformed is disposed in order to efficiently guide the light from the light-emitting element light-emitting element module to the incident surface of the light guide plate even if this slight deviation occurs, and a reflective member is added to the side surface. Yes. For example, silicon rubber is suitable for the transparent member 400. As the reflecting member, an optical thin film or a reflecting sheet is suitable. In addition, since silicon rubber has an optical refractive index of about 1.4 to 1.5 at the d-line, the interface reflection that occurs while light travels from the light emitting element module to the light guide plate is reduced as compared with the structure in the air layer. I can do it.

  According to the present embodiment, a backlight with high luminance and high reliability can be realized.

(Embodiment 2)
The second embodiment is a modification of the first embodiment. Only differences from the first embodiment will be described below.

  FIG. 3 is a diagram of the light emitting element array module of the light source unit in the backlight according to the second embodiment of the present invention. In this embodiment mode, out of the light emitted from the light emitting element 421, the light that deviates in the longitudinal direction of the incident surface 411 of the light guide plate 410 and does not contribute to the illumination of the backlight is efficiently taken into the light guide plate 410. The first embodiment is modified to make the above uniform.

  3A is a front view of the light-emitting element array module 420 according to the present embodiment as viewed from the incident surface 411 of the light guide plate 410, and FIG. 3B is a side view thereof. Reflecting mirrors 426 are arranged between the light emitting elements 421 and the light emitting element array modules 420 and at both ends of the light emitting element array module 420. Of the light emitted from the light emitting elements 421, in the longitudinal direction of the incident surface 411 of the light guide plate 410. The diverging light is reflected by the reflection mirror 426 and taken into the light guide plate 410. With this structure, a backlight with little light loss can be realized.

(Embodiment 3)
The third embodiment is a modification of the third embodiment. Only differences from the first and second embodiments will be described below.

  FIG. 4 is a diagram of a light source unit in the third embodiment of the backlight of the present invention. By arranging the light emitting element array module 420 on the wiring substrate 430 without changing the light source array module 420, a backlight light source corresponding to a large screen can be easily realized. FIG. 4 shows an example thereof, which is a light source unit in which three light emitting element array modules 420 are arranged in a horizontal row on a wiring board 430. According to the present embodiment, a backlight from a small size to a large size can be easily realized.

  The backlight and the liquid crystal display device of the present invention can increase the brightness while maintaining the reliability of the light source, have an effect of being able to be configured in a compact manner, and are easily applied to a small to large size backlight. Therefore, it is useful for video display parts such as portable information terminals and notebook personal computers that are required to be small and light.

Configuration diagram of Embodiment 1 of backlight of the present invention (A) The front view which looked at the light source part of Embodiment 1 of the backlight of this invention from the entrance plane side of the light-guide plate, (b) The sectional drawing (A) The front view which looked at the light emitting element array module of the light source part of Embodiment 2 of the backlight of this invention from the entrance plane side of the light-guide plate, (b) The side view The front view which looked at the light source part of Embodiment 3 of the backlight of this invention from the entrance plane side of the light-guide plate (A) The front view which shows the backlight using the conventional cold cathode tube, (b) The sectional drawing (A) The fragmentary sectional view which shows the principal part of the conventional backlight using a side emitter type LED light source element, (b) The front view which looked at the light source part from the light-guide plate side (A) Main part sectional drawing which shows the conventional backlight using an LED array module, (b) The front view which looked at the light source part from the light-guide plate side

Explanation of symbols

400 Transparent member 410 Light guide plate 411 Incident surface 420 Light emitting element array module 421 Light emitting element 422 Module substrate 424 Sealing resin 425 Light emitting portion 426 Reflecting mirror 430 Wiring substrate 431 Reflecting member 440 Reflecting plate 445 Reflecting sheet 450 Prism sheet 455 Diffusing sheet 460 Frame 470 Wiring board 480 Light source 490 Exterior case

Claims (3)

A light guide plate that is substantially flat and emits light introduced from the side surface entrance surface from one of the two exit surfaces facing each other to provide planar illumination;
A light emitting element array module in which a plurality of light emitting elements arranged along a longitudinal direction on a thin substrate is sealed with a transparent material to form a light emitting portion is mounted on a wiring board and is disposed on both sides of the light emitting element array module. And a light source part having a reflector disposed thereon,
A transparent member whose shape can be deformed is arranged so as to be in close contact with both the light emitting part of the light emitting element array module and the incident surface of the light guide plate, and a reflective member is added to the side surface of the transparent member, Further, the light source unit is directly fixed and installed in an outer case different from the frame that supports the light guide plate.   The backlight according to claim 1, wherein the light emitting element array module includes reflection mirrors disposed at both ends of the light emitting elements and alternately with the light emitting elements.   2. The back according to claim 1, wherein a plurality of the light emitting element array modules are arranged on the wiring board in a longitudinal direction so as to be substantially in contact with each other, and reflectors are disposed on both sides of the light emitting element array module. Light.

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