JP2010073389A - Plane light source device and liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a retention structure of an optical sheet capable of surely retaining an optical sheet without needs of other components or the thinning of a resin frame, and a plane light source device and a liquid crystal display capable of enabling thinning without causing a cost increase or the complication of assembling work. <P>SOLUTION: The plane light source device is provided with a light source, a light guide plate 4 with light from the light source incident from an end face, an optical sheet 6 arranged in contact with a top face of the light guide plate 4, and a metal frame 2 and a resin frame 3 housing these items. A top face of the optical sheet 6 is supported by a folded piece 8 provided at the metal frame 2. The optical sheet 6 has a locking piece 7 which is protrusively formed, and the top face of the locking piece 7 is supported by the folded piece 8 provided at the metal frame 2. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a planar light source device that irradiates light from a light source in a planar shape with a light guide plate, and further relates to a liquid crystal display device incorporating the planar light source device.

  In recent years, liquid crystal display devices having features such as light weight, thinness, and low power consumption are widely used as display devices for information devices such as personal computers and word processors, and display devices for video devices such as televisions, video movies, and car navigation systems. . In many cases, such a liquid crystal display device adopts a configuration in which a backlight unit (planar light source device) for applying illumination light from behind the liquid crystal panel is incorporated in order to realize a bright display screen.

  Here, the planar light source device used as the backlight unit is classified into a sidelight system and a direct system according to the location of the light source. For example, the sidelight system is a system in which a light source such as an LED is disposed on the side surface of the light guide plate facing the liquid crystal panel. When using LEDs, for example, LEDs arranged in a straight line on a flexible wiring board are arranged on one of the long sides of the display surface, and light emitted therefrom is taken into the light guide plate from the light incident surface of the light guide plate. Then, the light is converted into plane light directed in the display surface direction by an optical sheet such as a reflection sheet or the light guide plate. The sidelight method is advantageous in terms of thinning, and can be said to be a method suitable for a display device of a portable electronic device or a notebook personal computer, for example.

  In the above-described planar light source device, it is important to efficiently introduce the light from the light source into the liquid crystal panel or the like in order to ensure the brightness. The prism sheet is provided on the surface (light irradiation surface) side of the light guide plate. In general, an optical sheet such as the above is disposed. By disposing one or a plurality of optical sheets on the light guide plate, it becomes possible to efficiently irradiate a liquid crystal panel or the like with uniform light.

By the way, when an optical sheet is arranged on the surface of the light guide plate as described above, it is necessary to position and fix the optical sheet, and various methods for fixing the optical sheet have been studied. For example, Patent Document 1 discloses a structure in which an optical sheet is positioned and fixed using a columnar member for positioning a liquid crystal display panel at a predetermined position. In the optical sheet holding structure described in Patent Document 1, a through hole is provided in a side portion corresponding to the peripheral edge where the columnar member of the optical sheet is installed, the optical sheet is positioned by inserting the columnar member therein, and the optical sheet The optical sheet is fixed with a single-sided adhesive tape having through holes similar to those in FIG.
JP 2002-196212 A

  However, in the optical sheet holding structure described in Patent Document 1, it is necessary to form a columnar member on the frame and to form a through hole in the optical sheet. Also, the operation of attaching the optical sheet is complicated. Moreover, since a single-sided adhesive tape or the like in which a through hole is formed for fixing is also required, the number of parts is increased, which also leads to an increase in cost and poor workability.

  As a method for easily fixing an optical sheet without increasing the number of parts, for example, a structure in which a light guide plate or an optical sheet is sandwiched between a resin frame and a metal frame, and an upper surface of a locking piece (so-called ear) provided on the optical sheet A method of holding the resin with a resin frame is conceivable. However, due to the demand for thinning the liquid crystal display device, the thinning of the resin frame has also reached its limit, and the resin frame corresponding to the locking piece of the optical sheet is thinned to hold it. Is getting harder. For example, it is difficult to mold a resin frame with a thickness of 0.3 mm or less.

  Alternatively, it is conceivable to delete the resin frame corresponding to the locking piece of the optical sheet and hold the locking piece of the optical sheet using a sheet pressing tape. Separate parts such as a tape are required, and as with the invention described in Patent Document 1, the cost increases and the assembly work becomes complicated.

  The present invention has been proposed in view of such a conventional situation, and is capable of reliably holding an optical sheet without requiring separate parts, and a novel holding that does not require a thin resin frame or the like. An object of the present invention is to provide a planar light source device and a liquid crystal display device which can provide a structure and can be thinned without causing an increase in cost or a complicated assembly operation.

  In order to solve the above-described problems, a planar light source device according to the present invention includes a light source, a light guide plate into which light from the light source enters from an end surface, and an optical element disposed in contact with the upper surface of the light guide plate. The optical sheet includes a sheet, a metal frame that accommodates the sheet, and a resin frame, and an upper surface of the optical sheet is supported by a bent piece provided on the metal frame. The liquid crystal display device according to the present invention is characterized in that the planar light source device having the above-described configuration is incorporated in the back surface of the liquid crystal panel, and the liquid crystal panel is held by the resin frame.

  In the present invention, since the upper surface of the optical sheet is pressed and held by the bent piece provided on the metal frame, a separate part for holding the optical sheet is unnecessary. Further, it is not necessary to form a thin portion on the resin frame. Furthermore, since the optical sheet is sandwiched between the metal frame and the resin frame, the workability during assembly is good, and it is only necessary to insert the optical sheet between the bent piece of the metal frame and the resin frame.

  ADVANTAGE OF THE INVENTION According to this invention, it is possible to provide the planar light source device and liquid crystal display device which can hold | maintain an optical sheet with a simple structure, without requiring another components or thinning a resin frame. Therefore, it is possible to easily provide a planar light source device and a liquid crystal display device which can easily cope with holding an optical sheet, which is concerned about thinning, without increasing costs, and which is reliable and easy to assemble. Is possible.

  Hereinafter, a planar light source device according to the present invention and a liquid crystal display device using the same will be described in detail with reference to the drawings.

  FIG. 1 is a plan view showing a liquid crystal display device incorporating a planar light source device according to the present invention, and FIG.

  As shown in FIGS. 1 and 2, the liquid crystal display device of the present embodiment includes a liquid crystal panel 1 and a planar light source device that emits planar light from the back side of the liquid crystal panel 1. The structure is held by being sandwiched between the metal frame 2 formed in (1) and the resin frame 3 formed from a resin material.

  The liquid crystal panel 1 is configured, for example, by enclosing a liquid crystal material between an array substrate 11 and a counter substrate 12, and pixel electrodes and switching elements (thin film transistors) are formed in a matrix on the array substrate 11 corresponding to display pixels. Has been. In addition, on the array substrate 11, a signal line for sending an electric signal to the pixel electrode and a gate line for supplying a switching signal to the thin film transistor which is a switching element are wired orthogonally to each other. On the other hand, on the counter substrate 12, the counter electrode is formed on almost the entire surface with a transparent electrode material (for example, ITO), and a color filter layer is formed corresponding to each pixel. Further, polarizing films 13 and 14 are bonded to the outer surfaces of the array substrate 11 and the counter substrate 12 with their polarization axes orthogonal to each other.

  The liquid crystal panel 1 is mounted with an LSI or the like that supplies a drive signal, and image display is performed by driving the switching element based on the drive signal from the external circuit board. A region where this image display is performed is a display region, and the liquid crystal panel 1 has a display region in which a large number of pixels are arranged.

  On the other hand, the planar light source device that irradiates the liquid crystal panel 1 with planar light includes an LED (not shown) that is a point light source, a light guide plate 4 that converts light from the LED into planar light, and a light guide plate. 4 includes a reflection sheet 5 disposed on the back side of the light guide 4 and an optical sheet 6 disposed on the upper surface side of the light guide plate 4 and interposed between the light guide plate 4 and the liquid crystal panel 1.

  The LEDs that are point light sources are arranged in a line on the flexible wiring board along at least one side of the light guide plate 4, and the flexible wiring board on which the LEDs are mounted is installed on, for example, the long side of the light guide plate 4. Has been. A reflection sheet 5 is disposed on the lower surface of the light guide plate 4, and light emitted from the LED enters from the end surface of the light guide plate 4 and is reflected directly or by the reflection sheet 5 and passes through the light guide plate 4. The liquid crystal panel 1 is irradiated through the sheet 6.

  The above-described components are assembled in a frame and assembled as a liquid crystal display device. In the case of the liquid crystal display device of the present embodiment, the outer frame is configured by combining the metal frame 2 and the resin frame 3, and the periphery of the liquid crystal panel 1 and the light guide plate 4 extends around the entire circumference. 3 is supported by the shape.

  Specifically, the flexible wiring board on which the LED is mounted is fixed on the bottom plate 2a of the metal frame 2, and the light guide plate 4 is also made of metal so that the end face faces the LED. The frame 2 is accommodated in such a manner that it is placed on the bottom surface 2a. The reflection sheet 5 is installed on the back side of the light guide plate 4 and is fixed and accommodated so as to be sandwiched between the bottom plate 2 a of the metal frame 2 and the light guide plate 4. The metal frame 2 has a thickness of about 0.2 mm, for example.

  Further, the resin frame 3 is formed with a bowl-shaped support plate 3a projecting inward in the middle in the height direction, and the upper surface of the light guide plate 4 and the liquid crystal panel 1 are supported by the support plate 3a. The bottom is supported. Therefore, the light guide plate 4 is sandwiched and fixed between the bottom plate 2 a of the metal frame 2 and the support plate 3 a of the resin frame 3.

  Further, an optical sheet 6 is installed on the light guide plate 4. The optical sheet 6 is a so-called prism sheet, a diffusion sheet, or the like, and has one or two or more sheet configurations. In this embodiment, it is comprised by the two optical sheets 6a and 6b. The optical sheet 6 is placed on the light guide plate 4 in an overlapping manner, but it is difficult to support the outer periphery of the optical sheet 6 with the metal frame 2 or the resin frame 3.

  Therefore, in the present embodiment, the optical sheet 6 is provided with the locking piece 7 and fixedly held by the metal frame 2. As shown in FIG. 1, the locking piece 7 is formed in a shape protruding at two locations on the outer periphery of the optical sheet 6, and has a structure in which this is held by the metal frame 2. In the present embodiment, the locking pieces 7 are formed at two positions on the outer periphery of the optical sheet 6 at facing positions such as facing or diagonally, but the number is not limited to this, and for example, three or more positions. If possible, a plurality of optical sheets 6 can be formed at opposing positions in order to hold the optical sheet 6 evenly and reliably.

  3 is an enlarged schematic plan view showing the vicinity of the position where the locking piece 7 is formed, and FIG. 4 is a sectional view thereof. In this embodiment, a bent piece 8 is formed at a position corresponding to the locking piece 7 of the metal frame 2, and the upper surface of the locking piece 7 of the optical sheet 6 is supported by the bent piece 8. . Further, at the position corresponding to the locking piece 7 of the resin frame 3, the support plate 3 a is deleted, and a step surface 3 b that supports the lower surface of the locking piece 7 is formed. Therefore, after placing the optical sheet 6 on the light guide plate 4 and positioning the locking piece 7 on the stepped surface 3b of the resin frame 3, the bent piece 8 is moved to the locking piece 7 side. The optical sheet 6 can be positioned and fixed by bending.

  Here, as shown in FIG. 5, for example, the bent piece 8 is easily formed by processing a predetermined position of the metal frame 2 by cutting out three sides of a quadrangle and bending it at the position of the remaining one side. can do. Further, the step surface 3b of the resin frame 3 can be easily formed by a resin molding technique. For example, it is not necessary to reduce the thickness of the portion corresponding to the locking piece 7 of the support plate 3a of the resin frame 3, and it is not necessary to form a thickness that is less than the limit, making it difficult to mold the resin frame 3. There is nothing.

  In the planar light source device and the liquid crystal display device having the above-described configuration, the optical sheet 6 can be held with a simple structure without requiring separate parts or reducing the thickness of the resin frame. Further, when assembling the optical sheet 6, it is only necessary to fold the locking piece 7 (after placing the locking piece 7 on the stepped surface 3b of the resin frame 3 and then folding the bent piece 8 onto the locking piece 7, so that the optical sheet 6 can be easily and reliably assembled. For these reasons, it is possible to easily realize the holding of the optical sheet, which is concerned about the reduction in thickness, without increasing the cost.

It is a schematic plan view of a liquid crystal display device. It is a schematic sectional drawing of a liquid crystal display device. It is a schematic plan view which expands and shows the locking piece formation position vicinity of an optical sheet. It is a schematic sectional drawing of the locking piece formation position vicinity of an optical sheet. It is a schematic perspective view which shows the level | step difference surface of the bending piece of a metal frame, and a resin frame.

Explanation of symbols

1 liquid crystal panel, 2 metal frame, 2a bottom surface, 3 resin frame, 3a support plate, 3b stepped surface, 4 light guide plate, 5 reflection sheet, 6 optical sheet, 7 locking piece, 8 folded piece, 11 array substrate, 12 facing Substrate, 13, 14 Polarizing film

Claims (4)

A light source, a light guide plate into which light from the light source enters from an end surface, an optical sheet disposed in contact with the upper surface of the light guide plate, and a metal frame and a resin frame for housing them,
The planar light source device, wherein an upper surface of the optical sheet is supported by a bent piece provided on the metal frame.   The planar light source device according to claim 1, wherein a locking piece protrudes from the optical sheet, and an upper surface of the locking piece is supported by a bent piece provided on the metal frame.   3. The locking piece is formed at two or more positions opposite to each other around the optical sheet, and a bent piece is formed on the metal frame corresponding to each locking piece. The planar light source device described.   4. The liquid crystal display device according to claim 1, wherein the planar light source device according to claim 1 is incorporated in a back surface of the liquid crystal panel, and the liquid crystal panel is held by the resin frame.

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