JP2010015767A - Planar light source device and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a planar light source device capable of restraining generation of luminance variation caused by floating of an optical sheet and realizing its thinning, and a liquid crystal display device. <P>SOLUTION: The planar light source device has a light source (LED), a light guide plate 4 wherein light of the light source is entered from an end face, the optical sheet 6 arranged to come in contact with an upper surface of the light guide plate 4, and a frame 8 for storing the items. An end edge 9a of a support film 9 is superposed and supported on an end edge 6a at the light source side of the optical sheet 6. The light source is formed by arranging a plurality of LEDs 2, and the support film 9 is fixed on the upper surface of the LEDs 2 with a double-sided adhesive tape. Or, the LEDs 2 are stored in a metal cover 7, and the support film 9 is fixed inside the metal cover 7. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a planar light source device that irradiates light from a point light source such as an LED 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 a fluorescent tube is disposed on the side surface of the light guide plate facing the liquid crystal panel. When a fluorescent tube is used, a thin fluorescent tube is disposed 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, and the optical sheet such as a reflection sheet or the like The light guide plate converts the light into plane light directed in the display surface direction. On the other hand, the direct method is a method in which a plurality of straight tubular light sources such as fluorescent tubes are arranged on the back surface of the liquid crystal panel, and a diffusion plate is arranged between the liquid crystal panel and the light source. Among these systems, the sidelight system is advantageous in terms of thinning, and can be said to be a system suitable for display devices of portable electronic devices and notebook personal computers, for example.

  In recent years, the luminous efficiency of LEDs has been improved and has become comparable to fluorescent tubes. Therefore, in the sidelight type planar light source device, LEDs are used as light sources instead of fluorescent tubes. It is becoming. When using LEDs, LEDs arranged in a straight line are arranged at positions where fluorescent tubes have been arranged so far, and this is used as a light source. Since the size of the LED is smaller than that of the fluorescent tube, the use of the LED as a light source is advantageous in reducing the thickness of the liquid crystal display device.

  In addition, in the above-described planar light source device, it is important to efficiently introduce the light from the light source into the light guide plate, and it is important to ensure the luminance. A prism sheet or the like is provided on the surface (light irradiation surface) side of the light guide plate. Generally, an optical sheet is provided. By disposing the optical sheet, it becomes possible to efficiently irradiate the liquid crystal panel or the like with uniform light.

  By the way, when the optical sheet is disposed on the surface of the light guide plate as described above, in particular, when the optical sheet is lifted on the light incident surface side of the light guide plate, there is a risk of uneven brightness. The LED light source is a linear light source as a whole, but is only a continuous point light source. For this reason, there exists a bright part before the LED light source and a dark part between the LEDs. When the optical sheet is thin, this light and dark becomes easy to see due to slight floating and bending, resulting in uneven brightness. Such luminance unevenness is countered by widening the frame area of the liquid crystal display device or narrowing the LED pitch, but it is not sufficient.

  In order to reliably prevent the optical sheet from lifting up, it is considered effective to press the edge of the optical sheet by some means, and this is considered to eliminate the occurrence of uneven brightness. For example, although there are different purposes, several structures for supporting the periphery of the optical sheet have been proposed (see Patent Document 1, Patent Document 2, etc.), and by using this structure, the optical sheet can be prevented from being lifted. Is considered possible.

  For example, the invention described in Patent Document 1 suppresses floating due to peeling of a flexible wiring board attached to a light guide plate by an eaves portion extended from a light control sheet (prism sheet), and a point light source (LED) is controlled. The light control sheet is stably held at an appropriate position facing the light incident surface of the light guide plate, but the light control sheet extends to the area where the point light source is installed, and extends between the flexible wiring board and the partition plate of the frame case. Since the emitted light control sheet is interposed, it is considered that the lifting of the light control sheet is also prevented by the partition plate.

The invention described in Patent Document 2 has a structure in which foreign matter that has entered the gap between the light emitting surface side peripheral portion of the light guide plate and the mold frame facing the light guide plate does not easily move to the display region side. Since the optical sheet holding unit is opposed to the light guide plate with a space between the light guide plate and the light guide plate, the floating of the optical sheet is considered to be suppressed to some extent.
JP 2006-66171 A Japanese Patent Laid-Open No. 2005-100692

  However, when the structure described in Patent Document 1 or Patent Document 2 is adopted, it is disadvantageous from the viewpoint of reducing the thickness of the planar light source device. For example, in the invention described in Patent Document 1, the light control sheet (prism sheet) is extended and sandwiched between the flexible wiring board and the partition plate of the frame case. Accordingly, it is necessary to set a gap between the flexible wiring board and the partition plate. Since the light control sheet is relatively thick, the gap needs to be increased, and the thickness of the planar light source device must be increased. The same applies to the invention described in Patent Document 2, and in order to form the optical sheet holding portion, it is necessary to form a space corresponding to the thickness of the optical sheet, which increases the thickness dimension of the mold frame. Connected.

  The present invention has been proposed in view of such a conventional situation, and it is possible to surely suppress the occurrence of luminance unevenness due to lifting of the optical sheet and the like, and it is possible to realize a reduction in thickness. It is an object to provide a light source device and further to provide a liquid crystal display device.

  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. A sheet and a frame that accommodates the sheet are provided, and at least the edge of the support film having one end fixed on the edge of the optical sheet on the light source side is overlapped and supported. 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.

  In the planar light source device of the present invention, the support film is superimposed on the light source side edge of the optical sheet, and the edge of the optical film is pressed by the support film. Therefore, no lifting or the like occurs at the light source side edge of the optical sheet, and the occurrence of luminance unevenness is eliminated. In addition, unlike an optical sheet, a thin film can be used as a support film, so that only a small space is required to accommodate this, and there is no need to increase the thickness of a frame or the like. .

  According to the present invention, it is possible to reliably suppress the occurrence of luminance unevenness due to floating of the optical sheet, and to provide a highly reliable planar light source device and a liquid crystal display device with high display quality. In addition, according to the present invention, it is possible to suppress the occurrence of the luminance unevenness without hindering the thinning of the planar light source device and the liquid crystal display device, and to promote the thinning of the planar light source device and the liquid crystal display device. It is advantageous.

  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.

(First embodiment)
In this embodiment, the light source is configured by arranging a plurality of LEDs (light emitting diodes), and the support film that presses the optical sheet is fixed to the upper surface of the LED so as to prevent the optical sheet from being lifted. This is an example.

  FIG. 1 shows a basic configuration of the planar light source device 1. As shown in FIG. 1, the planar light source device 1 of the present embodiment includes a flexible wiring board 3 on which a plurality of LEDs 2 that are point light sources are mounted in a straight line, a rectangular plate-shaped light guide plate 4, a reflective sheet 5, and an optical element. A sheet 6 is provided, and light from the LED 2 that is a point light source is converted into planar light by the light guide plate 4.

  The LEDs 2 that are point light sources are arranged in a line on the flexible wiring board 3 along at least one side of the light guide plate 4. In this embodiment, the flexible wiring board 3 on which the LEDs 2 are mounted is guided. It is installed on the long side of the light plate 4. A reflection sheet 5 is disposed on the lower surface of the light guide plate 4, and light emitted from the LED 2 enters from the end surface of the light guide plate 4 and is reflected by the reflection sheet 5 directly or after passing through the light guide plate 4. For example, the liquid crystal display panel is irradiated through the sheet 6. Therefore, the planar light source device 1 of the present embodiment is a side light type illumination unit.

  The above-described components (the flexible wiring board 3 and the light guide plate 4 on which the LEDs 2 are mounted) are assembled in the frame and assembled as the planar light source device 1. In the case of the planar light source device 1 of the present embodiment, the outer frame is configured by combining the metal cover 7 and the frame 8, and the vicinity of the flexible wiring board 3 on which the LED 2 is mounted is covered by the metal cover 7. In addition, the periphery of the light guide plate 4 is supported by the frame 8 over the entire circumference.

  FIG. 2 is a schematic plan view of the surface light source device, and FIG. 3 is a cross-sectional view (cross-sectional view taken along the line AA in FIG. 2) showing a cross-sectional structure when the respective constituent elements are assembled. is there. In the embodiment shown in FIG. 1, the case where the LED 2 is a top view type LED 2 is illustrated, and for this reason, the flexible wiring board 3 is also upright so as to be parallel to the incident surface of the light guide plate 4. However, in the case illustrated in FIG. 3, the flexible wiring board 3 is arranged in parallel to the lower surface side of the light guide plate 4 because the LED 2 is illustrated with respect to a form using the side view type LED 2. Shows the case. However, since there is no functional change, the following description will be made taking an example of application to the side view type.

  A flexible wiring board 3 on which the LED 2 is mounted is fixed on the bottom plate 7a of the metal cover 7 having a U-shaped cross section, and the light guide plate 4 has an end face facing the LED 2. Are inserted into the metal cover 7. 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 7 a of the metal cover 7 and the light guide plate 4. The frame 8 is attached so as to cover the outside of the metal cover 7.

  On the other hand, 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. When the edge 6a on the light source (LED2) side is lifted, this optical sheet 6 leads to luminance unevenness in the vicinity of the LED2. Therefore, in order to prevent the end edge 6a from being lifted, it is preferable to press the end edge 6a by some means.

  As one method for pressing the edge 6 a of the optical sheet 6, for example, the size of the optical sheet 6 may be enlarged and sandwiched between the upper surface of the LED 2 and the top plate 7 b of the metal cover 7. However, since the optical sheet 6 (especially the prism sheet) is relatively thick, it is necessary to increase the distance between the upper surface of the LED 2 and the top plate 7b of the metal cover 7, and it is necessary to increase the thickness of the metal cover 7. There is. An increase in the thickness of the metal cover 7 leads to an increase in the thickness of the planar light source device 1, which is not preferable.

  Therefore, in the planar light source device 1 of the present embodiment, the edge 9a of the support film 9 is overlapped with the light source side edge 6a of the optical sheet 6 to prevent the edge 6a from being lifted. In the case of the present embodiment, one end edge 9a of the support film 9 is overlapped with the light source side end edge 6a of the optical sheet 6, and the other end edge 9b is fixed to the upper surface of the LED 2, thereby the optical sheet. 6 edge 6a is pressed down.

  Unlike the optical sheet 6, a thin film can be used for the support film 9. For example, it is preferable to use a film having a thickness of about 0.1 mm. The thickness of 0.1 mm is a value smaller than the thickness of the optical sheet 6. Therefore, when it is inserted between the upper surface of the LED 2 and the top plate 7b of the metal cover 7, it is not necessary to widen the distance between the upper surface of the LED 2 and the top plate 7b of the metal cover 7, and the upper surface of the LED 2 even with a slight gap. It is possible to fix to.

  The support film 9 is preferably a transparent film having light transmittance. By using the transparent film, the light emitted from the light guide plate 4 is not blocked, and the support film 9 does not adversely affect the light irradiation.

  The support film 9 may be bonded and fixed to the upper surface of the LED 2 using, for example, a double-sided adhesive tape. Alternatively, by fixing the distance between the upper surface of the LED 2 and the top plate 7 b of the metal cover 7, the LED 2 can be fixed by being sandwiched between the upper surface of the LED 2 and the top plate 7 b of the metal cover 7.

  As described above, by adopting a structure in which the optical sheet 6 is pressed by attaching and fixing the support film 9 to the upper surface of the LED 2, the optical function is not affected by the shape of the metal cover 7, the frame 8, or the like. The edge 6a of the sheet 6 can be pressed. Therefore, it is possible to suppress the occurrence of luminance unevenness. Moreover, since the space | interval of the upper surface of LED2 and the top plate 7b of the metal cover 7 should just be few, it is not necessary to enlarge the thickness dimension of the metal cover 7, and thickness reduction of the planar light source device 1 is realizable. .

  The planar light source device 1 having the above configuration is incorporated as a backlight unit in a liquid crystal display device. Next, a liquid crystal display device incorporating the above-described planar light source device 1 will be described.

  FIG. 4 is an exploded view of a liquid crystal display device in which the illumination unit 1 that is a planar light source device is incorporated, and FIG. 5 is a sectional view in an assembled state. As shown in FIGS. 4 and 5, the liquid crystal display device according to the present embodiment includes a liquid crystal panel 11 and the above-described planar light source device 1, which are back cover 12 formed of a metal material, a resin material, or the like. I try to keep it.

  The liquid crystal panel 11 is configured, for example, by enclosing a liquid crystal material between an array substrate and a counter substrate, and pixel electrodes and switching elements (thin film transistors) corresponding to display pixels are formed in a matrix on the array substrate. . In addition, 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 on the array substrate at right angles to each other. On the other hand, on the counter substrate, 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 are bonded to the outer surfaces of the array substrate and the counter substrate, with their polarization axes orthogonal to each other.

  The liquid crystal panel 11 is mounted with an LSI or the like for supplying 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 11 has a display region in which a large number of pixels are arranged.

  The planar light source device 1 is incorporated as a backlight of the liquid crystal panel 11, and light emitted from the LED 2 that is a light source is reflected directly or by the reflection sheet 5 and guided to the light guide plate 4. After passing through the optical plate 4, the liquid crystal panel 11 is irradiated through the optical sheet 6. The irradiated light is transmitted through the liquid crystal panel 11, and images such as characters and videos are displayed with a predetermined brightness.

  As shown in FIG. 5, the liquid crystal panel 11 includes an array substrate 21 and a counter substrate 22, and polarizing films 23 and 24 are bonded to both surfaces thereof with the polarization axes orthogonal to each other. The liquid crystal panel 11 is overlapped facing the light guide plate 4 of the planar light source device 1, and the peripheral portion of the array substrate 21 is supported in a state of being placed on the top plate 7 b of the metal cover 7. .

  In the liquid crystal display device having the above-described configuration, the optical film 6 can be prevented from being lifted in the planar light source device 1, so that a liquid crystal display device with excellent display quality without luminance unevenness can be provided while realizing a reduction in thickness. Is possible.

(Second Embodiment)
In this embodiment, the light source is configured by arranging a plurality of LEDs, and is housed in a metal cover, and by fixing a support film that presses the optical sheet to the inner surface of the metal cover, This is an example in which lifting is prevented.

  FIG. 6 shows a cross-sectional structure of the planar light source device 1 of the present embodiment. The components of the surface light source device are the same as those of the first embodiment, and the basic structure is also the same. In the planar light source device of this embodiment, one end edge 9 a of the support film 9 is overlapped with the light source side edge 6 a of the optical sheet 6, and the other end edge 9 b is double-sided on the inner surface of the top plate 7 b of the metal cover 7. It is fixed by adhering using an adhesive tape or the like, and the edge 6a of the optical sheet 6 is pressed down.

  FIG. 7 shows a state in which the liquid crystal panel 11 is overlaid on the planar light source device of FIG. The configuration of the liquid crystal panel 11 is the same as that of the first embodiment, and is composed of an array substrate 21 and a counter substrate 22, and polarizing films 23 and 24 are bonded to both surfaces with their polarization axes orthogonal to each other. . The liquid crystal panel 11 is overlapped facing the light guide plate 4 of the planar light source device 1, and the peripheral portion of the array substrate 21 is supported in a state of being placed on the top plate 7 b of the metal cover 7. .

  Also in the planar light source device and the liquid crystal display device of the present embodiment, it is possible to suppress the occurrence of luminance unevenness due to the floating of the optical sheet 6. Further, it is possible to reduce the thickness. Furthermore, by sticking the support film 9 on the inner side of the metal cover 7, there is an advantage that the size of the support film 9 can be made smaller than in the case of the first embodiment.

It is a disassembled perspective view of a planar light source device. It is a typical top view of a planar light source device. It is a schematic sectional drawing of the planar light source device of 1st Embodiment. It is a disassembled perspective view which shows an example of the liquid crystal display device incorporating the planar light source device. It is a schematic sectional drawing of the liquid crystal display device incorporating the planar light source device of 1st Embodiment. It is a schematic sectional drawing of the planar light source device of 2nd Embodiment. It is a schematic sectional drawing of the liquid crystal display device incorporating the planar light source device of 2nd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Planar light source device, 2 LED, 3 Flexible wiring board, 4 Light guide plate, 5 Reflective sheet, 6 Optical sheet, 7 Metal cover, 8 Frame, 9 Support film, 11 Liquid crystal panel, 12 Back cover, 21 Array substrate, 22 Opposing substrate, 23, 24 Polarizing film

Claims (6)

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 frame that accommodates them.
A planar light source device, wherein at least an edge of a support film, one end of which is fixed, is overlapped and supported on an edge on the light source side of the optical sheet.   The planar light source device according to claim 1, wherein the light source is configured by arranging a plurality of LEDs, and the support film is fixed by an upper surface of the LEDs.   The planar light source device according to claim 2, wherein the support film is attached to the upper surface of the LED with a double-sided adhesive tape.   2. The surface according to claim 1, wherein the light source is configured by arranging a plurality of LEDs, is housed in a metal cover, and the support film is fixed to an inner surface of the metal cover. Light source device.   The planar light source device according to claim 1, wherein the support film has light transmittance.   6. A liquid crystal display device, wherein the planar light source device according to claim 1 is incorporated in a back surface of the liquid crystal panel.

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