JP2004333859A - Backlight device of liquid crystal panel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a backlight device capable of uniformly illuminating the entire display screen of a liquid crystal panel. <P>SOLUTION: Light emitted from LEDs 11 is made incident toward a center part of a light guide plate 14 from light incident surfaces 20 and 21 formed at lower both ends of the light guide plate 14. Light made incident from the light incident surface 20 goes toward an opposing light reflection surface 30 and light made incident from the light incident surface 21 goes toward a light reflection surface 31. Light reaching the light reflection surfaces 30 and 31 is reflected by reflection plates 40 and 41 toward the center part of the light guide plate 14. The light guide plate 14 is uniformly illuminated with light from the light incident surfaces 20 and 21 and light reflected by the light reflection surfaces 30 and 31. Thereby, luminance unevenness given to an object to be illuminated such as the liquid crystal panel can be prevented. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a backlight device for a liquid crystal panel, and more particularly, a light source that emits light from a point-like light source and a light incident surface formed on one end face thereof and facing the back surface of the liquid crystal panel. The present invention relates to a backlight device for a liquid crystal panel including a light guide plate that emits light from a surface.
[0002]
[Prior art]
In various devices, a liquid crystal display device using a liquid crystal panel in which liquid crystal is sealed is used. Since the liquid crystal itself does not emit light, it is necessary to illuminate the liquid crystal panel with an external light source. For this reason, backlight devices that illuminate a liquid crystal panel from the back are used in many devices. The backlight device is provided with a light source and a light guide plate. The light guide plate has a light incident surface on one end surface on which light from the light source is incident. After the light incident from the light incident surface is diffused inside, the light guide plate is emitted from the light emitting surface facing the back of the liquid crystal panel. Let The light exit surface serves as a surface light source and illuminates the back surface of the liquid crystal panel.
[0003]
As a light source of a recent backlight device, a light emitting diode (hereinafter referred to as an LED) that emits white light is frequently used in place of an elongated fluorescent tube. Since the LED is a point light source, the shape and material of the light guide plate, the arrangement position of the light source, and the like are devised to prevent unevenness in the brightness of the irradiation light from the light exit surface.
[0004]
Patent Document 1 listed below describes a backlight device in which a spot-like light source is arranged at a corner portion of a light guide plate so that luminance unevenness is not generated in light irradiated from a light exit surface. There is also a backlight device in which two adjacent corners of the light guide plate are cut so that light enters from the cut portion (see, for example, Patent Document 2).
[0005]
[Patent Document 1]
JP 2001-143512 A [Patent Document 2]
Japanese Patent Laid-Open No. 2001-228475
[Problems to be solved by the invention]
However, the method described in the above publication has a problem in that light from the light source is difficult to reach the corner portion of the light guide plate far from the light source, and uneven illuminance is generated on the liquid crystal panel.
[0007]
The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a backlight device capable of providing uniform illumination to the entire display screen of a liquid crystal panel.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the backlight device of the liquid crystal panel of the present invention is irradiated when light incident from the light incident surface is irradiated on the cut surface by cutting a corner portion of the light guide plate. It is characterized by forming a light reflecting surface that reflects light and re-irradiates it toward the inside of the light guide plate. The light reflecting surface may be covered with a light reflecting member that irradiates part of the light leaking from the light reflecting surface toward the inside of the light guide slope again. The light incident surface may be provided at a corner portion facing the light reflecting surface.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
An external perspective view and an exploded view of a backlight device 10 to which the present invention is applied are shown in FIGS. 1 and 2, respectively. The backlight device 10 includes a white LED 11 as a light source and a light guide means 13. The backlight device 10 converts the light emitted from the LED 11 into a surface light source by the light guide means 13 and irradiates an object to be irradiated such as a liquid crystal panel.
[0010]
The light guide means 13 includes a light guide plate 14, reflection plates 40 and 41, a case 17, and a diffusion filter 19. The light guide plate 14 has a plate shape, and is formed of, for example, transparent plastic. The surface is provided with irregularities, or a lot of minute light diffusing materials are mixed therein. Light incident on the light guide plate 14 is diffused inside the light guide plate 14.
[0011]
At both lower ends of the light guide plate 14, light incident surfaces 20 and 21 are formed so as to face the central portion of the light guide plate 14, respectively. In the vicinity of the light incident surfaces 20 and 21, the LED 11 is disposed so that the light emitting portion faces the light incident surfaces 20 and 21. Each LED 11 is connected to a light emitting circuit (not shown), and is driven by this light emitting circuit to emit light.
[0012]
As is well known, the light emitted from the LED 11 diffuses radially but has a certain degree of directivity. The light emitted from each LED 11 enters from the light incident surfaces 20 and 21 and travels toward the center of the light guide plate 14 while being diffused inside the light guide plate 14.
[0013]
In the light guide plate 14, a corner portion facing the light incident surface 20 is cut, and a light reflecting surface 30 is formed so as to face the light incident surface 20. A reflector 40 is disposed behind the light reflecting surface 30. The reflection plate 40 is formed of a light-reflective material, and the reflection surface is provided with irregularities and grooves, and the light irradiated on the reflection surface is diffused during reflection. When the light incident from the light incident surface 20 reaches the light reflecting surface 30, it is reflected by the reflecting plate 40 and is irradiated again toward the central portion of the light guide plate 14.
[0014]
Similarly, a light reflecting surface 31 is formed at a corner portion facing the light incident surface 21 so as to face the light incident surface 21. A reflection plate 41 is disposed behind the light reflection surface 31, and light incident from the light incident surface 21 is reflected by the reflection plate 41 when reaching the light reflection surface 31, and again toward the center of the light guide plate 14. Irradiated.
[0015]
The light guide plate 14 is covered with a case 17 at the top, bottom, left and right side surfaces and the back surface. The inner wall of the case 17 is a reflective surface, and the reflective surface is provided with unevenness and grooves, like the reflective plates 40 and 41. The case 17 diffuses and reflects the light leaking from the light guide plate 14 to irradiate the inside of the light guide plate 14 again.
[0016]
The front surface of the light guide plate 14 is a light emitting surface 50 from which light incident from the light incident surfaces 20 and 21 is emitted. The light that can be emitted from the LED 11 is diffused and leveled by the light guide plate 14, the reflectors 30 and 31, and the case 17, and is emitted from the light exit surface 50. A diffusion sheet 19 is provided in front of the light emitting surface 50. As the diffusion filter 119, for example, a prism plate or a diffusion sheet is used, and the light emitted from the light emitting surface 50 is more sufficiently diffused.
[0017]
Hereinafter, the operation of the backlight device 10 configured as described above will be described with reference to the drawings. The light emitted from the LED 11 is incident toward the center of the light guide plate 14 from the light incident surfaces 20 and 21 formed at both lower ends of the light guide plate 14.
[0018]
The light incident from the light incident surface 20 travels toward the light reflecting surface 30 facing the light incident surface 20. Similarly, light incident from the light incident surface 20 travels toward the light reflecting surface 30. The light reaching the light reflecting surfaces 30 and 31 is reflected toward the central portion of the light guide plate 14 by the reflecting plates 40 and 42, respectively.
[0019]
As shown in FIG. 3A, when the light reflecting surfaces 30 and 31 are not provided, the upper portion of the light guide plate 14 is far from the LED 11, and in particular, the upper corner portion is narrowed toward the tip, so the LED 11 Difficult to reach the light emitted from For this reason, the brightness | luminance difference of the light-guide plate 14 will become large in the lower corner part in which LED11 is arrange | positioned, and the upper corner part far from LED11.
[0020]
On the other hand, as shown in FIG. 3B, in the backlight device 10, the light reflecting surfaces 30 and 31 are formed by cutting off the corner portions that are diagonal to the light incident surfaces 20 and 21. Light from the LED 11 is likely to reach each part. Moreover, since the light from the LED 11 is reflected by the light reflecting surfaces 30 and 31, the inside of the light guide plate 14 can be illuminated uniformly. As a result, it is possible to prevent luminance unevenness applied to an object to be irradiated such as a liquid crystal panel illuminated by the backlight device 10.
[0021]
In the above-described embodiment, the light incident surfaces are provided at both lower ends of the light guide plate and the light reflecting surfaces are provided at both upper ends. However, the present invention is not limited to this. For example, as shown in FIG. 4A, a part of the lower surface of the light guide plate 50 is a light incident surface 51 and four corners are light reflection surfaces 55, and a reflection plate 57 is provided behind the light reflection surface 55. May be. Further, as shown in FIG. 5B, the entire lower surface of the light guide plate 60 may be a light incident surface 61. Similarly, a light incident surface may be formed on the side surface or the upper surface.
[0022]
Moreover, although the said embodiment demonstrated the example in which a light reflection surface and a light-incidence surface are planes, you may form these with a curved surface. Further, although an example in which one light reflecting surface or light incident surface is formed by one surface has been described, a plurality of surfaces may be combined to form one light reflecting surface or light incident surface.
[0023]
【The invention's effect】
As described above in detail, according to the backlight device of the present invention, the point light source and the light from the light source are incident from the light incident surface formed on one end surface and face the back surface of the liquid crystal panel. In a backlight device of a liquid crystal panel composed of a light guide plate that emits from the light exit surface, the corner portion of the light guide plate is cut, and when the light incident from the light incident surface is irradiated on the cut surface, Since the light reflecting surface for reflecting the irradiated light and re-irradiating it toward the inside of the light guide plate is formed, the light guide plate can be evenly illuminated, and uneven illuminance of the liquid crystal panel can be prevented.
[Brief description of the drawings]
FIG. 1 is an external perspective view of a backlight device.
FIG. 2 is an exploded view of the backlight device.
FIG. 3 is an explanatory diagram showing a difference in how light is transmitted between a case where a light reflecting surface is not provided and a case where a light reflecting surface is provided.
FIG. 4 is a plan view of the backlight device in which the positions of the light reflecting surface and the light incident surface are changed.
10 Backlight device 11 LED
13 Light guide means 14, 50, 60 Light guide plates 20, 21, 51, 61 Light incident surfaces 30, 31, 55 Light reflecting surfaces 40, 41, 57 Reflecting plates

Claims (3)

A backlight device for a liquid crystal panel, comprising a point-like light source and a light guide plate that allows light from the light source to enter from a light incident surface formed on one end surface and to exit from a light exit surface facing the back surface of the liquid crystal panel In
A light reflecting surface that cuts a corner portion of the light guide plate and reflects the irradiated light and re-irradiates the light into the light guide plate when the light incident on the cut surface is irradiated from the light incident surface. A liquid crystal panel backlight device characterized by comprising: The liquid crystal panel according to claim 1, wherein the light reflecting surface is covered with a light reflecting member so that a part of the light leaking from the light reflecting surface is irradiated again toward the inside of the light guide hill. Backlight device. 3. The liquid crystal panel backlight device according to claim 1, wherein the light incident surface is provided at a corner portion facing the light reflecting surface.

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